Add host platform detection and macOS styles

Expose host platform to the UI and apply platform-specific styling. Backend: add CurrentPlatformName() and include "platform" in the JSON sent from NebulaController so the frontend can know the host OS. Frontend: detectHostPlatform() initializes state.platform, applyPlatform() sets a platform-* body class, and applyState() applies it. CSS: add .platform-macos rules to adjust title padding and hide window controls on macOS. Also fix FilePathToUrl to avoid producing an extra slash when the encoded path already starts with '/'.

.clangd

@@ -0,0 +1,17 @@
+# clangd configuration for Nebula Browser
+#
+# Full diagnostics require:
+#   1. CEF binary distribution unpacked to thirdparty/cef/
+#   2. Running: cmake -B build -DCMAKE_EXPORT_COMPILE_COMMANDS=ON
+#   3. Symlink or copy: ln -s build/compile_commands.json .
+#
+# Without compile_commands.json, clangd uses fallback flags below.
+
+CompileFlags:
+  Add:
+    - -std=c++20
+    - -xobjective-c++
+    - -Isrc
+    - -Ithirdparty/cef
+    - -Ithirdparty/cef/include
+    - -Wno-c++17-extensions

.gitignore

@@ -18,3 +18,4 @@ CMakeFiles/
 
 # Logs
 *.log
+/.cache

ASSETS-LICENSE.md

@@ -0,0 +1,11 @@
+# Nebula Browser Asset License
+
+The source code of Nebula Browser is licensed under the Mozilla Public License 2.0, as described in the LICENSE file.
+
+However, the Nebula Browser name, logo, icons, artwork, screenshots, visual identity, branding materials, and other non-code assets are not automatically covered by the MPL-2.0 license.
+
+Unless otherwise stated, these assets are All Rights Reserved.
+
+You may not use the Nebula Browser name, logo, or branding in a way that suggests endorsement, official status, or affiliation with the Nebula Project without permission.
+
+Community forks are welcome, but they should use their own name and branding unless permission is granted.

CMakeLists.txt

@@ -1,6 +1,11 @@
 cmake_minimum_required(VERSION 3.21)
 
-project(NebulaBrowser LANGUAGES CXX)
+# Enable OBJCXX early on macOS for Cocoa integration
+if(APPLE)
+    project(NebulaBrowser LANGUAGES CXX OBJCXX)
+else()
+    project(NebulaBrowser LANGUAGES CXX)
+endif()
 
 set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
@@ -16,16 +21,11 @@ if(NOT EXISTS "${CEF_ROOT}/cmake/FindCEF.cmake")
         "CEF was not found.\n"
         "Expected CEF here:\n"
         "  ${CEF_ROOT}\n\n"
-        "Make sure the contents of the CEF binary distribution are inside thirdparty/cef."
+        "Unpack the CEF binary distribution for your OS into thirdparty/cef."
     )
 endif()
 
-# ------------------------------------------------------------
-# CEF setup
-# ------------------------------------------------------------
-
 list(APPEND CMAKE_MODULE_PATH "${CEF_ROOT}/cmake")
-
 find_package(CEF REQUIRED)
 
 add_subdirectory(
@@ -33,81 +33,226 @@ add_subdirectory(
     "${CMAKE_BINARY_DIR}/libcef_dll_wrapper"
 )
 
+SET_CEF_TARGET_OUT_DIR()
+
 # ------------------------------------------------------------
-# Nebula source files
+# Sources
 # ------------------------------------------------------------
 
-set(NEBULA_SOURCES
+set(NEBULA_COMMON_SOURCES
-    app/main.cpp
+    src/app/first_run_state.cpp
+    src/app/nebula_controller.cpp
+    src/app/run.cpp
+    src/browser/session_state.cpp
+    src/browser/tab.cpp
+    src/browser/tab_manager.cpp
+    src/browser/url_utils.cpp
+    src/cef/browser_client.cpp
+    src/cef/nebula_app.cpp
+    src/ui/paths.cpp
 )
 
-add_executable(NebulaBrowser WIN32
+if(OS_WINDOWS)
-    ${NEBULA_SOURCES}
+    set(NEBULA_PLATFORM_SOURCES
-)
+        src/platform/win/default_browser_win.cpp
-
+        src/platform/win/paths_win.cpp
-SET_EXECUTABLE_TARGET_PROPERTIES(NebulaBrowser)
+        src/platform/win/startup_win.cpp
-
+        src/platform/win/browser_host_win.cpp
-if(MSVC)
+        src/platform/win/nebula_window_win.cpp
-    set_property(TARGET NebulaBrowser PROPERTY
-        MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>"
     )
+elseif(OS_MACOSX)
+    set(NEBULA_PLATFORM_SOURCES
+        src/platform/mac/default_browser_mac.mm
+        src/platform/mac/paths_mac.cpp
+        src/platform/mac/startup_mac.mm
+        src/platform/mac/browser_host_mac.mm
+        src/platform/mac/nebula_window_mac.mm
+    )
+    set_source_files_properties(
+        src/platform/mac/startup_mac.mm
+        src/platform/mac/browser_host_mac.mm
+        src/platform/mac/nebula_window_mac.mm
+        PROPERTIES
+            COMPILE_FLAGS "-fobjc-arc"
+    )
+elseif(OS_LINUX)
+    set(NEBULA_PLATFORM_SOURCES
+        src/platform/linux/default_browser_linux.cpp
+        src/platform/linux/paths_linux.cpp
+        src/platform/linux/startup_linux.cpp
+        src/platform/linux/browser_host_linux.cpp
+        src/platform/linux/nebula_window_linux.cpp
+    )
+else()
+    message(FATAL_ERROR "Unsupported platform.")
 endif()
 
-target_include_directories(NebulaBrowser PRIVATE
+# On macOS, CEF is a framework linked via CEF_STANDARD_LIBS.
-    "${CEF_ROOT}"
+# On Windows/Linux, we create a logical target for libcef.
-    "${CEF_ROOT}/include"
+if(NOT OS_MACOSX)
-)
+    ADD_LOGICAL_TARGET("libcef_lib" "${CEF_LIB_RELEASE}" "${CEF_LIB_DEBUG}")
-
-target_link_libraries(NebulaBrowser PRIVATE
-    libcef_dll_wrapper
-    ${CEF_STANDARD_LIBS}
-)
-
-# ------------------------------------------------------------
-# Platform-specific CEF linking
-# ------------------------------------------------------------
-
-if(WIN32)
-    target_link_libraries(NebulaBrowser PRIVATE
-        "${CEF_ROOT}/Release/libcef.lib"
-    )
-
-    target_compile_definitions(NebulaBrowser PRIVATE
-        NOMINMAX
-        WIN32_LEAN_AND_MEAN
-    )
 endif()
 
-# ------------------------------------------------------------
+if(OS_LINUX)
-# Copy CEF runtime files after build
+    FIND_LINUX_LIBRARIES("X11")
-# ------------------------------------------------------------
+endif()
 
-if(WIN32)
+function(add_nebula_app_target nebula_target entry_source)
-    add_custom_command(TARGET NebulaBrowser POST_BUILD
+    if(OS_WINDOWS)
+        add_executable(${nebula_target} WIN32
+            ${entry_source}
+            ${NEBULA_COMMON_SOURCES}
+            ${NEBULA_PLATFORM_SOURCES}
+        )
+    elseif(OS_MACOSX)
+        add_executable(${nebula_target} MACOSX_BUNDLE
+            ${entry_source}
+            ${NEBULA_COMMON_SOURCES}
+            ${NEBULA_PLATFORM_SOURCES}
+        )
+    elseif(OS_LINUX)
+        add_executable(${nebula_target}
+            ${entry_source}
+            ${NEBULA_COMMON_SOURCES}
+            ${NEBULA_PLATFORM_SOURCES}
+        )
+    endif()
+
+    SET_EXECUTABLE_TARGET_PROPERTIES(${nebula_target})
+    add_dependencies(${nebula_target} libcef_dll_wrapper)
+
+    target_include_directories(${nebula_target} PRIVATE
+        "${CMAKE_SOURCE_DIR}/src"
+        "${CEF_ROOT}"
+        "${CEF_ROOT}/include"
+    )
+
+    if(OS_MACOSX)
+        # On macOS, CEF is a framework; don't link libcef_lib
+        target_link_libraries(${nebula_target} PRIVATE
+            libcef_dll_wrapper
+            ${CEF_STANDARD_LIBS}
+        )
+    else()
+        target_link_libraries(${nebula_target} PRIVATE
+            libcef_lib
+            libcef_dll_wrapper
+            ${CEF_STANDARD_LIBS}
+        )
+    endif()
+
+    if(MSVC)
+        set_property(TARGET ${nebula_target} PROPERTY
+            MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>"
+        )
+    endif()
+
+    # ------------------------------------------------------------
+    # Platform-specific CEF runtime deployment
+    # ------------------------------------------------------------
+
+    if(OS_WINDOWS)
+        target_link_libraries(${nebula_target} PRIVATE dwmapi)
+        target_compile_definitions(${nebula_target} PRIVATE
+            NOMINMAX
+            WIN32_LEAN_AND_MEAN
+        )
+        COPY_FILES("${nebula_target}" "${CEF_BINARY_FILES}" "${CEF_BINARY_DIR_RELEASE}" "${CEF_TARGET_OUT_DIR}")
+        COPY_FILES("${nebula_target}" "${CEF_RESOURCE_FILES}" "${CEF_RESOURCE_DIR}" "${CEF_TARGET_OUT_DIR}")
+    elseif(OS_LINUX)
+        COPY_FILES("${nebula_target}" "${CEF_BINARY_FILES}" "${CEF_BINARY_DIR_RELEASE}" "${CEF_TARGET_OUT_DIR}")
+        COPY_FILES("${nebula_target}" "${CEF_RESOURCE_FILES}" "${CEF_RESOURCE_DIR}" "${CEF_TARGET_OUT_DIR}")
+    elseif(OS_MACOSX)
+        target_link_libraries(${nebula_target} PRIVATE
+            "-framework Cocoa"
+            "-framework ApplicationServices"
+        )
+        set(NEBULA_APP "${CEF_TARGET_OUT_DIR}/${nebula_target}.app")
+        set(NEBULA_HELPER_TARGET "${nebula_target}_Helper")
+        set(NEBULA_HELPER_OUTPUT_NAME "${nebula_target} Helper")
+        string(TOLOWER "${nebula_target}" NEBULA_HELPER_BUNDLE_NAME)
+
+        COPY_MAC_FRAMEWORK(
+            "${nebula_target}"
+            "${CEF_BINARY_DIR_RELEASE}"
+            "${NEBULA_APP}"
+        )
+        COPY_FILES(
+            "${nebula_target}"
+            "${CEF_BINARY_FILES}"
+            "${CEF_BINARY_DIR_RELEASE}"
+            "${NEBULA_APP}/Contents/Frameworks"
+        )
+        COPY_FILES(
+            "${nebula_target}"
+            "${CEF_RESOURCE_FILES}"
+            "${CEF_RESOURCE_DIR}"
+            "${NEBULA_APP}/Contents/Resources"
+        )
+
+        foreach(_suffix_list ${CEF_HELPER_APP_SUFFIXES})
+            string(REPLACE ":" ";" _suffix_list ${_suffix_list})
+            list(GET _suffix_list 0 _name_suffix)
+            list(GET _suffix_list 1 _target_suffix)
+            list(GET _suffix_list 2 _plist_suffix)
+
+            set(_helper_target "${NEBULA_HELPER_TARGET}${_target_suffix}")
+            set(_helper_output_name "${NEBULA_HELPER_OUTPUT_NAME}${_name_suffix}")
+            set(_helper_info_plist "${CMAKE_CURRENT_BINARY_DIR}/${_helper_target}-Info.plist")
+
+            file(READ "${CMAKE_SOURCE_DIR}/cmake/mac-helper-Info.plist.in" _plist_contents)
+            string(REPLACE "\${EXECUTABLE_NAME}" "${_helper_output_name}" _plist_contents "${_plist_contents}")
+            string(REPLACE "\${PRODUCT_NAME}" "${_helper_output_name}" _plist_contents "${_plist_contents}")
+            string(REPLACE "\${HELPER_BUNDLE_NAME}" "${NEBULA_HELPER_BUNDLE_NAME}" _plist_contents "${_plist_contents}")
+            string(REPLACE "\${BUNDLE_ID_SUFFIX}" "${_plist_suffix}" _plist_contents "${_plist_contents}")
+            file(WRITE "${_helper_info_plist}" "${_plist_contents}")
+
+            add_executable(${_helper_target} MACOSX_BUNDLE
+                app/process_helper_mac.cc
+                src/cef/nebula_app.cpp
+            )
+            SET_EXECUTABLE_TARGET_PROPERTIES(${_helper_target})
+            add_dependencies(${_helper_target} libcef_dll_wrapper)
+            target_include_directories(${_helper_target} PRIVATE
+                "${CMAKE_SOURCE_DIR}/src"
+                "${CEF_ROOT}"
+                "${CEF_ROOT}/include"
+            )
+            target_link_libraries(${_helper_target} PRIVATE
+                libcef_dll_wrapper
+                ${CEF_STANDARD_LIBS}
+            )
+            set_target_properties(${_helper_target} PROPERTIES
+                MACOSX_BUNDLE_INFO_PLIST "${_helper_info_plist}"
+                OUTPUT_NAME "${_helper_output_name}"
+            )
+
+            add_dependencies(${nebula_target} "${_helper_target}")
+            add_custom_command(TARGET ${nebula_target} POST_BUILD
+                COMMAND ${CMAKE_COMMAND} -E copy_directory
+                    "${CEF_TARGET_OUT_DIR}/${_helper_output_name}.app"
+                    "${NEBULA_APP}/Contents/Frameworks/${_helper_output_name}.app"
+                VERBATIM
+            )
+        endforeach()
+    endif()
+
+    # ------------------------------------------------------------
+    # Copy Nebula UI files after build
+    # ------------------------------------------------------------
+
+    add_custom_command(TARGET ${nebula_target} POST_BUILD
         COMMAND ${CMAKE_COMMAND} -E copy_directory
-            "${CEF_ROOT}/Release"
+            "${CMAKE_SOURCE_DIR}/ui"
-            "$<TARGET_FILE_DIR:NebulaBrowser>"
+            "$<TARGET_FILE_DIR:${nebula_target}>/ui"
 
         COMMAND ${CMAKE_COMMAND} -E copy_directory
-            "${CEF_ROOT}/Resources"
+            "${CMAKE_SOURCE_DIR}/assets"
-            "$<TARGET_FILE_DIR:NebulaBrowser>"
+            "$<TARGET_FILE_DIR:${nebula_target}>/ui/assets"
 
-        COMMENT "Copying CEF runtime files..."
+        COMMENT "Copying Nebula UI files and assets for ${nebula_target}..."
     )
-endif()
+endfunction()
 
-# ------------------------------------------------------------
+add_nebula_app_target(NebulaBrowser app/main.cpp)
-# Copy Nebula UI files after build
+add_nebula_app_target(NebulaBigPicture app/main_bigpicture.cpp)
-# ------------------------------------------------------------
-
-add_custom_command(TARGET NebulaBrowser POST_BUILD
-    COMMAND ${CMAKE_COMMAND} -E copy_directory
-        "${CMAKE_SOURCE_DIR}/ui"
-        "$<TARGET_FILE_DIR:NebulaBrowser>/ui"
-
-    COMMAND ${CMAKE_COMMAND} -E copy_directory
-        "${CMAKE_SOURCE_DIR}/assets"
-        "$<TARGET_FILE_DIR:NebulaBrowser>/ui/assets"
-
-    COMMENT "Copying Nebula UI files and assets..."
-)

LICENSE

@@ -0,0 +1,373 @@
+Mozilla Public License Version 2.0
+==================================
+
+1. Definitions
+--------------
+
+1.1. "Contributor"
+ means each individual or legal entity that creates, contributes to
+ the creation of, or owns Covered Software.
+
+1.2. "Contributor Version"
+ means the combination of the Contributions of others (if any) used
+ by a Contributor and that particular Contributor's Contribution.
+
+1.3. "Contribution"
+ means Covered Software of a particular Contributor.
+
+1.4. "Covered Software"
+ means Source Code Form to which the initial Contributor has attached
+ the notice in Exhibit A, the Executable Form of such Source Code
+ Form, and Modifications of such Source Code Form, in each case
+ including portions thereof.
+
+1.5. "Incompatible With Secondary Licenses"
+ means
+
+ (a) that the initial Contributor has attached the notice described
+ in Exhibit B to the Covered Software; or
+
+ (b) that the Covered Software was made available under the terms of
+ version 1.1 or earlier of the License, but not also under the
+ terms of a Secondary License.
+
+1.6. "Executable Form"
+ means any form of the work other than Source Code Form.
+
+1.7. "Larger Work"
+ means a work that combines Covered Software with other material, in
+ a separate file or files, that is not Covered Software.
+
+1.8. "License"
+ means this document.
+
+1.9. "Licensable"
+ means having the right to grant, to the maximum extent possible,
+ whether at the time of the initial grant or subsequently, any and
+ all of the rights conveyed by this License.
+
+1.10. "Modifications"
+ means any of the following:
+
+ (a) any file in Source Code Form that results from an addition to,
+ deletion from, or modification of the contents of Covered
+ Software; or
+
+ (b) any new file in Source Code Form that contains any Covered
+ Software.
+
+1.11. "Patent Claims" of a Contributor
+ means any patent claim(s), including without limitation, method,
+ process, and apparatus claims, in any patent Licensable by such
+ Contributor that would be infringed, but for the grant of the
+ License, by the making, using, selling, offering for sale, having
+ made, import, or transfer of either its Contributions or its
+ Contributor Version.
+
+1.12. "Secondary License"
+ means either the GNU General Public License, Version 2.0, the GNU
+ Lesser General Public License, Version 2.1, the GNU Affero General
+ Public License, Version 3.0, or any later versions of those
+ licenses.
+
+1.13. "Source Code Form"
+ means the form of the work preferred for making modifications.
+
+1.14. "You" (or "Your")
+ means an individual or a legal entity exercising rights under this
+ License. For legal entities, "You" includes any entity that
+ controls, is controlled by, or is under common control with You. For
+ purposes of this definition, "control" means (a) the power, direct
+ or indirect, to cause the direction or management of such entity,
+ whether by contract or otherwise, or (b) ownership of more than
+ fifty percent (50%) of the outstanding shares or beneficial
+ ownership of such entity.
+
+2. License Grants and Conditions
+--------------------------------
+
+2.1. Grants
+
+Each Contributor hereby grants You a world-wide, royalty-free,
+non-exclusive license:
+
+(a) under intellectual property rights (other than patent or trademark)
+ Licensable by such Contributor to use, reproduce, make available,
+ modify, display, perform, distribute, and otherwise exploit its
+ Contributions, either on an unmodified basis, with Modifications, or
+ as part of a Larger Work; and
+
+(b) under Patent Claims of such Contributor to make, use, sell, offer
+ for sale, have made, import, and otherwise transfer either its
+ Contributions or its Contributor Version.
+
+2.2. Effective Date
+
+The licenses granted in Section 2.1 with respect to any Contribution
+become effective for each Contribution on the date the Contributor first
+distributes such Contribution.
+
+2.3. Limitations on Grant Scope
+
+The licenses granted in this Section 2 are the only rights granted under
+this License. No additional rights or licenses will be implied from the
+distribution or licensing of Covered Software under this License.
+Notwithstanding Section 2.1(b) above, no patent license is granted by a
+Contributor:
+
+(a) for any code that a Contributor has removed from Covered Software;
+ or
+
+(b) for infringements caused by: (i) Your and any other third party's
+ modifications of Covered Software, or (ii) the combination of its
+ Contributions with other software (except as part of its Contributor
+ Version); or
+
+(c) under Patent Claims infringed by Covered Software in the absence of
+ its Contributions.
+
+This License does not grant any rights in the trademarks, service marks,
+or logos of any Contributor (except as may be necessary to comply with
+the notice requirements in Section 3.4).
+
+2.4. Subsequent Licenses
+
+No Contributor makes additional grants as a result of Your choice to
+distribute the Covered Software under a subsequent version of this
+License (see Section 10.2) or under the terms of a Secondary License (if
+permitted under the terms of Section 3.3).
+
+2.5. Representation
+
+Each Contributor represents that the Contributor believes its
+Contributions are its original creation(s) or it has sufficient rights
+to grant the rights to its Contributions conveyed by this License.
+
+2.6. Fair Use
+
+This License is not intended to limit any rights You have under
+applicable copyright doctrines of fair use, fair dealing, or other
+equivalents.
+
+2.7. Conditions
+
+Sections 3.1, 3.2, 3.3, and 3.4 are conditions of the licenses granted
+in Section 2.1.
+
+3. Responsibilities
+-------------------
+
+3.1. Distribution of Source Form
+
+All distribution of Covered Software in Source Code Form, including any
+Modifications that You create or to which You contribute, must be under
+the terms of this License. You must inform recipients that the Source
+Code Form of the Covered Software is governed by the terms of this
+License, and how they can obtain a copy of this License. You may not
+attempt to alter or restrict the recipients' rights in the Source Code
+Form.
+
+3.2. Distribution of Executable Form
+
+If You distribute Covered Software in Executable Form then:
+
+(a) such Covered Software must also be made available in Source Code
+ Form, as described in Section 3.1, and You must inform recipients of
+ the Executable Form how they can obtain a copy of such Source Code
+ Form by reasonable means in a timely manner, at a charge no more
+ than the cost of distribution to the recipient; and
+
+(b) You may distribute such Executable Form under the terms of this
+ License, or sublicense it under different terms, provided that the
+ license for the Executable Form does not attempt to limit or alter
+ the recipients' rights in the Source Code Form under this License.
+
+3.3. Distribution of a Larger Work
+
+You may create and distribute a Larger Work under terms of Your choice,
+provided that You also comply with the requirements of this License for
+the Covered Software. If the Larger Work is a combination of Covered
+Software with a work governed by one or more Secondary Licenses, and the
+Covered Software is not Incompatible With Secondary Licenses, this
+License permits You to additionally distribute such Covered Software
+under the terms of such Secondary License(s), so that the recipient of
+the Larger Work may, at their option, further distribute the Covered
+Software under the terms of either this License or such Secondary
+License(s).
+
+3.4. Notices
+
+You may not remove or alter the substance of any license notices
+(including copyright notices, patent notices, disclaimers of warranty,
+or limitations of liability) contained within the Source Code Form of
+the Covered Software, except that You may alter any license notices to
+the extent required to remedy known factual inaccuracies.
+
+3.5. Application of Additional Terms
+
+You may choose to offer, and to charge a fee for, warranty, support,
+indemnity or liability obligations to one or more recipients of Covered
+Software. However, You may do so only on Your own behalf, and not on
+behalf of any Contributor. You must make it absolutely clear that any
+such warranty, support, indemnity, or liability obligation is offered by
+You alone, and You hereby agree to indemnify every Contributor for any
+liability incurred by such Contributor as a result of warranty, support,
+indemnity or liability terms You offer. You may include additional
+disclaimers of warranty and limitations of liability specific to any
+jurisdiction.
+
+4. Inability to Comply Due to Statute or Regulation
+---------------------------------------------------
+
+If it is impossible for You to comply with any of the terms of this
+License with respect to some or all of the Covered Software due to
+statute, judicial order, or regulation then You must: (a) comply with
+the terms of this License to the maximum extent possible; and (b)
+describe the limitations and the code they affect. Such description must
+be placed in a text file included with all distributions of the Covered
+Software under this License. Except to the extent prohibited by statute
+or regulation, such description must be sufficiently detailed for a
+recipient of ordinary skill to be able to understand it.
+
+5. Termination
+--------------
+
+5.1. The rights granted under this License will terminate automatically
+if You fail to comply with any of its terms. However, if You become
+compliant, then the rights granted under this License from a particular
+Contributor are reinstated (a) provisionally, unless and until such
+Contributor explicitly and finally terminates Your grants, and (b) on an
+ongoing basis, if such Contributor fails to notify You of the
+non-compliance by some reasonable means prior to 60 days after You have
+come back into compliance. Moreover, Your grants from a particular
+Contributor are reinstated on an ongoing basis if such Contributor
+notifies You of the non-compliance by some reasonable means, this is the
+first time You have received notice of non-compliance with this License
+from such Contributor, and You become compliant prior to 30 days after
+Your receipt of the notice.
+
+5.2. If You initiate litigation against any entity by asserting a patent
+infringement claim (excluding declaratory judgment actions,
+counter-claims, and cross-claims) alleging that a Contributor Version
+directly or indirectly infringes any patent, then the rights granted to
+You by any and all Contributors for the Covered Software under Section
+2.1 of this License shall terminate.
+
+5.3. In the event of termination under Sections 5.1 or 5.2 above, all
+end user license agreements (excluding distributors and resellers) which
+have been validly granted by You or Your distributors under this License
+prior to termination shall survive termination.
+
+************************************************************************
+*                                                                      *
+* 6. Disclaimer of Warranty                                            *
+* -------------------------                                            *
+*                                                                      *
+* Covered Software is provided under this License on an "as is"        *
+* basis, without warranty of any kind, either expressed, implied, or   *
+* statutory, including, without limitation, warranties that the         *
+* Covered Software is free of defects, merchantable, fit for a         *
+* particular purpose or non-infringing. The entire risk as to the      *
+* quality and performance of the Covered Software is with You.         *
+* Should any Covered Software prove defective in any respect, You      *
+* (not any Contributor) assume the cost of any necessary servicing,    *
+* repair, or correction. This disclaimer of warranty constitutes an    *
+* essential part of this License. No use of any Covered Software is    *
+* authorized under this License except under this disclaimer.          *
+*                                                                      *
+************************************************************************
+
+************************************************************************
+*                                                                      *
+* 7. Limitation of Liability                                           *
+* --------------------------                                           *
+*                                                                      *
+* Under no circumstances and under no legal theory, whether tort       *
+* (including negligence), contract, or otherwise, shall any            *
+* Contributor, or anyone who distributes Covered Software as           *
+* permitted above, be liable to You for any direct, indirect,          *
+* special, incidental, or consequential damages of any character       *
+* including, without limitation, damages for lost profits, loss of     *
+* goodwill, work stoppage, computer failure or malfunction, or any     *
+* and all other commercial damages or losses, even if such party       *
+* shall have been informed of the possibility of such damages. This    *
+* limitation of liability shall not apply to liability for death or    *
+* personal injury resulting from such party's negligence to the        *
+* extent applicable law prohibits such limitation. Some                *
+* jurisdictions do not allow the exclusion or limitation of            *
+* incidental or consequential damages, so this exclusion and           *
+* limitation may not apply to You.                                    *
+*                                                                      *
+************************************************************************
+
+8. Litigation
+-------------
+
+Any litigation relating to this License may be brought only in the
+courts of a jurisdiction where the defendant maintains its principal
+place of business and such litigation shall be governed by laws of that
+jurisdiction, without reference to its conflict-of-law provisions.
+Nothing in this Section shall prevent a party's ability to bring
+cross-claims or counter-claims.
+
+9. Miscellaneous
+----------------
+
+This License represents the complete agreement concerning the subject
+matter hereof. If any provision of this License is held to be
+unenforceable, such provision shall be reformed only to the extent
+necessary to make it enforceable. Any law or regulation which provides
+that the language of a contract shall be construed against the drafter
+shall not be used to construe this License against a Contributor.
+
+10. Versions of the License
+---------------------------
+
+10.1. New Versions
+
+Mozilla Foundation is the license steward. Except as provided in Section
+10.3, no one other than the license steward has the right to modify or
+publish new versions of this License. Each version will be given a
+distinguishing version number.
+
+10.2. Effect of New Versions
+
+You may distribute the Covered Software under the terms of the version
+of the License under which You originally received the Covered Software,
+or under the terms of any subsequent version published by the license
+steward.
+
+10.3. Modified Versions
+
+If you create software not governed by this License, and you want to
+create a new license for such software, you may create and use a
+modified version of this License if you rename the license and remove
+any references to the name of the license steward (except to note that
+such modified license differs from this License).
+
+10.4. Distributing Source Code Form that is Incompatible With Secondary
+Licenses
+
+If You choose to distribute Source Code Form that is Incompatible With
+Secondary Licenses under the terms of this version of the License, the
+notice described in Exhibit B of this License must be attached.
+
+Exhibit A - Source Code Form License Notice
+-------------------------------------------
+
+ This Source Code Form is subject to the terms of the Mozilla Public
+ License, v. 2.0. If a copy of the MPL was not distributed with this
+ file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+If it is not possible or desirable to put the notice in a particular
+file, then You may include the notice in a location (such as a LICENSE
+file in a relevant directory) where a recipient would be likely to look
+for such a notice.
+
+You may add additional accurate notices of copyright ownership.
+
+Exhibit B - "Incompatible With Secondary Licenses" Notice
+---------------------------------------------------------
+
+ This Source Code Form is "Incompatible With Secondary Licenses", as
+ defined by the Mozilla Public License, v. 2.0.

README.md

@@ -0,0 +1,351 @@
+# Nebula Browser
+
+A Chromium Embedded Framework (CEF) browser with a custom HTML chrome UI.
+
+**Nebula Browser** is a controller-first web browser designed for Steam Deck, SteamOS-style systems, handheld PCs, living room setups, and gamepad-driven desktop environments.
+
+Originally developed as an Electron-based browser for SteamOS users, Nebula Browser is now being rebuilt with **CEF / Chromium Embedded Framework** to provide deeper control over the browser experience, improved native integration, and a cleaner long-term foundation for custom UI, controller navigation, and platform-specific builds.
+
+Development on Nebula Browser has somewhat resumed, with the project now moving toward a more native custom browser architecture.
+
+Nebula Browser is intended to remain open source. The browser source code is licensed under MPL-2.0, while Nebula branding and visual assets are protected separately.
+
+## Documentation
+
+- **[Cross-platform build & architecture](docs/cross-platform.md)** — how to use one repo for Windows, macOS, and Linux; CEF setup; source layout; porting status.
+
+---
+
+## Project Status
+
+Nebula Browser is currently in early active redevelopment.
+
+The original Electron version proved the core idea: a browser built around controller use, large-screen navigation, and a UI that does not feel like a standard desktop browser awkwardly placed on a handheld gaming device.
+
+The new CEF version is the next major step.
+
+Current focus areas include:
+
+* Rebuilding the browser around CEF
+* Creating a fully custom browser interface
+* Moving away from default Chromium UI elements
+* Reusing and adapting existing Nebula UI concepts where possible
+* Supporting controller-first navigation
+* Preparing for cross-platform builds across Windows, Linux, and macOS
+* Creating a stronger foundation for future NebulaOS integration
+
+---
+
+## Why CEF?
+
+Nebula Browser originally used Electron because it was fast to prototype, easy to package, and allowed the project to move quickly. However, Electron also comes with limits when building a browser that is meant to feel fully custom and deeply integrated with the operating system.
+
+The move to **CEF** allows Nebula Browser to become more than a web app wrapped in a browser shell.
+
+CEF gives the project:
+
+* More control over the native window and browser lifecycle
+* Better separation between the browser engine and the custom UI
+* Greater flexibility for building a non-Chrome-like interface
+* A more suitable foundation for SteamOS, Linux, and future NebulaOS use
+* The ability to build a browser that feels purpose-built rather than wrapped
+
+The goal is not to create another Chromium clone. The goal is to create a browser interface designed around how people actually use handhelds, controllers, TVs, and gaming-first systems.
+
+---
+
+## Distribution Direction
+
+Nebula Browser was originally aimed at Steam. However, after exploring Steam as a release platform, it became clear that Steam may not be the best fit for this kind of application.
+
+The current distribution direction is:
+
+### Primary Target
+
+* **Itch.io**
+
+Itch.io is currently the most practical and flexible platform for distributing Nebula Browser. It allows the project to be released as a utility-style app without needing to fit into a traditional game store category.
+
+### Potential Future Targets
+
+* **Epic Games Store**
+* **GOG**
+* **Flatpak / Linux package distribution**
+* **Direct downloads from the Nebula website**
+
+Epic Games and GOG are being considered as possible future distribution platforms, especially if Nebula Browser grows into a more polished desktop or gaming utility. These are not confirmed release platforms yet, but they remain possible options.
+
+---
+
+## Open Source Direction
+
+Nebula Browser is intended to remain open source because browsers are privacy-sensitive software. Users should be able to inspect how the browser works, verify that it is not doing anything suspicious, and contribute fixes or improvements when they find problems.
+
+Open source is especially important for:
+
+* User trust
+* Privacy transparency
+* Linux and Steam Deck community adoption
+* Cross-platform testing
+* Community contributions
+* Long-term sustainability
+
+The core Nebula Browser project should remain open source, including:
+
+* Browser shell
+* CEF integration code
+* Custom browser UI
+* Controller navigation systems
+* Settings and theme systems
+* Build scripts and documentation
+
+Not every Nebula-related component has to be open source. Some future or external components may remain private or be licensed separately, such as:
+
+* NebulaOS-specific services
+* Account systems
+* Cloud sync
+* Hosted backend services
+* Internal analytics or crash reporting infrastructure
+* Private distribution tooling
+* Experimental unreleased features
+* Protected branding assets
+
+Suggested openness model:
+
+```text
+Nebula Browser: open source
+Nebula Core: open source or source-available
+NebulaOS: potentially partially open source
+Nebula online services/backend: private
+Branding assets: protected
+```
+
+---
+
+## Core Vision
+
+Nebula Browser is built around one simple idea:
+
+> The web should be comfortable to use from a couch, handheld, controller, or gaming-focused operating system.
+
+Most browsers are designed around keyboards, mice, and desktop workflows. Nebula Browser is designed around a different experience.
+
+Nebula Browser aims to support:
+
+* Controller-first navigation
+* Large, readable interface elements
+* Gamepad-friendly menus and shortcuts
+* Steam Deck and handheld PC usability
+* Custom home pages and launcher-style navigation
+* Better integration with gaming-focused environments
+* A UI that feels closer to a console app than a traditional browser
+
+---
+
+## Planned Features
+
+The CEF rebuild is still early, but the intended feature set includes:
+
+* Fully custom browser chrome
+* Custom tab bar
+* Custom address bar
+* Controller-friendly navigation system
+* On-screen keyboard support
+* Bookmarks and quick access tiles
+* Custom home page
+* Desktop mode and controller mode
+* Fullscreen and couch-friendly browsing
+* Custom context menus
+* Download management
+* Settings system
+* Theme support
+* Steam Deck / handheld-focused layout options
+* Optional integration with NebulaOS
+
+Some features may be ported or adapted from the earlier Electron version where it makes sense.
+
+---
+
+## Nebula Core
+
+Nebula Browser may also make use of **Nebula Core**, a shared package system for Nebula-related projects.
+
+Nebula Core is intended to provide reusable systems such as:
+
+* Controller input handling
+* Navigation helpers
+* UI components
+* Glyphs and button prompts
+* Theming utilities
+* On-screen keyboard systems
+* Shared Nebula project logic
+
+Because the new browser is CEF-based rather than Electron-based, some Nebula Core modules may need to be adapted for native integration or used through the browser UI layer rather than directly inside the C++ application layer.
+
+---
+
+## Relationship to NebulaOS
+
+Nebula Browser is part of the wider **Nebula Project** ecosystem.
+
+NebulaOS is a controller-focused operating system / shell concept designed around gaming, handheld PCs, and living room devices. Nebula Browser is intended to become one of the key built-in applications for that ecosystem.
+
+While Nebula Browser can exist as a standalone app, its long-term role is to provide a web browsing experience that feels native inside NebulaOS.
+
+---
+
+## Technology Stack
+
+The current redevelopment direction uses:
+
+* **C++** for the native browser shell
+* **CEF / Chromium Embedded Framework** for web rendering
+* **HTML, CSS, and JavaScript** for the custom browser UI
+* **CMake** for project configuration
+* Platform-specific CEF builds for Windows, Linux, and macOS
+
+The previous version used Electron, but the current direction is focused on CEF.
+
+---
+
+## Repository Structure
+
+The repository structure may change as the CEF rebuild develops, but the project is expected to follow a layout similar to:
+
+```text
+NebulaBrowser/
+├── app/
+│   ├── browser/
+│   ├── ui/
+│   └── platform/
+├── cef/
+│   └── README.md
+├── resources/
+│   ├── icons/
+│   ├── themes/
+│   └── pages/
+├── scripts/
+├── third_party/
+├── CMakeLists.txt
+└── README.md
+```
+
+CEF itself should generally not be committed directly into the repository. Instead, platform-specific CEF builds should be downloaded separately and placed into the expected local folder during development.
+
+---
+
+## Development Notes
+
+Nebula Browser is still experimental and in transition from the original Electron version to the new CEF version.
+
+Expect changes in:
+
+* Build setup
+* File structure
+* UI architecture
+* Controller input systems
+* Platform support
+* Packaging and distribution
+
+The project is not yet considered production-ready.
+
+---
+
+## Building
+
+Build instructions will be expanded as the CEF version becomes more stable.
+
+At a high level, development requires:
+
+1. A supported C++ compiler
+2. CMake
+3. A downloaded CEF binary distribution for your operating system
+4. The Nebula Browser source code
+5. A local build folder
+
+Example build flow:
+
+```bash
+cmake -S . -B build
+cmake --build build
+```
+
+More detailed platform-specific instructions will be added later. For macOS/Linux prerequisites, directory structure, and current port status, see [docs/cross-platform.md](docs/cross-platform.md).
+
+### Quick start (Windows)
+
+1. Download the [CEF standard binary distribution](https://cef-builds.spotifycdn.com/index.html) for Windows 64-bit.
+2. Extract into `thirdparty/cef/` so `thirdparty/cef/cmake/FindCEF.cmake` exists.
+3. Build:
+
+   ```powershell
+   cmake -B build
+   cmake --build build --config Release
+   ```
+
+4. Run `build\Release\NebulaBrowser.exe`.
+
+---
+
+## Platform Goals
+
+Nebula Browser is being designed with cross-platform support in mind.
+
+Target platforms include:
+
+* Windows
+* Linux
+* SteamOS / Steam Deck
+* macOS
+
+Linux and SteamOS are especially important because Nebula Browser was originally created to solve a gap in the handheld and couch-browsing experience.
+
+---
+
+## Release Plans
+
+Nebula Browser does not currently have a fixed release date.
+
+The current release plan is:
+
+1. Rebuild the core browser shell in CEF
+2. Replace default Chromium UI with a custom Nebula interface
+3. Restore core browser functionality
+4. Add controller-first navigation
+5. Prepare an early public build
+6. Release through Itch.io first
+7. Explore additional distribution options later
+
+---
+
+## Contributing
+
+Nebula Browser is currently a personal / experimental project and is still finding its new technical direction.
+
+Contributions, ideas, testing, and feedback may become more open once the CEF rebuild has a more stable foundation.
+
+---
+
+## Licensing
+
+Nebula Browser separates source code licensing from branding and visual assets.
+
+The preferred licensing direction is:
+
+* **Source code:** Mozilla Public License 2.0
+* **Documentation:** CC BY 4.0, unless otherwise specified
+* **Branding, logos, icons, names, and visual identity:** All Rights Reserved, unless explicitly stated otherwise
+
+MPL-2.0 is being used because it is a practical open-source license for a browser-style project. It allows people to use, modify, and contribute to the code while requiring changes to MPL-licensed files to remain open under the same license.
+
+The Nebula name, logo, and brand identity are not automatically granted for reuse just because the code is open source. See [ASSETS-LICENSE.md](ASSETS-LICENSE.md) for the separate asset and branding terms.
+
+See the CEF distribution and Chromium license terms for third-party runtime components.
+
+---
+
+## About
+
+Nebula Browser is created as part of the wider Nebula Project, a collection of software experiments focused on controller-first computing, gaming-focused interfaces, and custom desktop experiences.
+
+The project began as a browser for SteamOS and Steam Deck users, but is now evolving into a more flexible, native, and custom browser experience built around CEF.

app/main.cpp

@@ -1,341 +1,33 @@
+#include "app/run.h"
+#include "platform/types.h"
+
+#if defined(_WIN32)
 #include <windows.h>
+#elif defined(__APPLE__)
+#include "include/wrapper/cef_library_loader.h"
+#endif
 
-#include <algorithm>
+#if defined(_WIN32)
-#include <cctype>
-#include <filesystem>
-#include <string>
-
-#include "include/cef_app.h"
-#include "include/cef_browser.h"
-#include "include/cef_client.h"
-#include "include/cef_command_line.h"
-#include "include/cef_request.h"
-#include "include/cef_request_handler.h"
-#include "include/wrapper/cef_helpers.h"
-
-namespace {
-
-std::string WideToUtf8(const std::wstring& value) {
-    if (value.empty()) {
-        return {};
-    }
-
-    const int size = WideCharToMultiByte(
-        CP_UTF8, 0, value.data(), static_cast<int>(value.size()),
-        nullptr, 0, nullptr, nullptr);
-    std::string result(size, '\0');
-    WideCharToMultiByte(
-        CP_UTF8, 0, value.data(), static_cast<int>(value.size()),
-        result.data(), size, nullptr, nullptr);
-    return result;
-}
-
-std::string FilePathToUrl(std::filesystem::path path) {
-    std::string value = WideToUtf8(path.wstring());
-    for (char& ch : value) {
-        if (ch == '\\') {
-            ch = '/';
-        }
-    }
-
-    std::string encoded;
-    encoded.reserve(value.size());
-    for (char ch : value) {
-        encoded += ch == ' ' ? "%20" : std::string(1, ch);
-    }
-    return "file:///" + encoded;
-}
-
-std::filesystem::path GetHomePath() {
-    wchar_t exe_path[MAX_PATH] = {};
-    const DWORD length = GetModuleFileNameW(nullptr, exe_path, MAX_PATH);
-    if (length == 0 || length == MAX_PATH) {
-        return {};
-    }
-
-    return std::filesystem::path(exe_path).parent_path() /
-           "ui" / "pages" / "home.html";
-}
-
-std::string GetHomeUrl() {
-    const auto home_path = GetHomePath();
-    if (home_path.empty()) {
-        return "https://www.google.com";
-    }
-
-    return FilePathToUrl(home_path);
-}
-
-std::string GetUrlWithoutDecoration(std::string url) {
-    const size_t split = url.find_first_of("?#");
-    if (split != std::string::npos) {
-        url.resize(split);
-    }
-    return url;
-}
-
-std::string ToLowerAscii(std::string value) {
-    std::transform(value.begin(), value.end(), value.begin(), [](unsigned char ch) {
-        return static_cast<char>(std::tolower(ch));
-    });
-    return value;
-}
-
-bool IsInternalHomeUrl(const std::string& url) {
-    return GetUrlWithoutDecoration(url) == GetHomeUrl();
-}
-
-bool IsChromiumNewTabUrl(const std::string& url) {
-    const std::string target = ToLowerAscii(GetUrlWithoutDecoration(url));
-    return target == "about:blank" ||
-           target == "chrome://newtab" ||
-           target == "chrome://newtab/" ||
-           target == "chrome://new-tab-page" ||
-           target == "chrome://new-tab-page/" ||
-           target == "chrome-search://local-ntp/local-ntp.html";
-}
-
-bool IsEmptyOrChromiumNewTabUrl(const std::string& url) {
-    return url.empty() || IsChromiumNewTabUrl(url);
-}
-
-class NebulaClient final : public CefClient,
-                           public CefDisplayHandler,
-                           public CefKeyboardHandler,
-                           public CefLifeSpanHandler,
-                           public CefPermissionHandler,
-                           public CefRequestHandler {
-public:
-    CefRefPtr<CefDisplayHandler> GetDisplayHandler() override {
-        return this;
-    }
-
-    CefRefPtr<CefKeyboardHandler> GetKeyboardHandler() override {
-        return this;
-    }
-
-    CefRefPtr<CefLifeSpanHandler> GetLifeSpanHandler() override {
-        return this;
-    }
-
-    CefRefPtr<CefPermissionHandler> GetPermissionHandler() override {
-        return this;
-    }
-
-    CefRefPtr<CefRequestHandler> GetRequestHandler() override {
-        return this;
-    }
-
-    void OnAddressChange(CefRefPtr<CefBrowser> browser,
-                         CefRefPtr<CefFrame> frame,
-                         const CefString& url) override {
-        CEF_REQUIRE_UI_THREAD();
-
-        if (browser && frame && frame->IsMain() &&
-            IsChromiumNewTabUrl(url)) {
-            browser->GetMainFrame()->LoadURL(GetHomeUrl());
-        }
-    }
-
-    void OnTitleChange(CefRefPtr<CefBrowser> browser,
-                       const CefString& title) override {
-        CEF_REQUIRE_UI_THREAD();
-
-        CefWindowHandle window = browser->GetHost()->GetWindowHandle();
-        if (window) {
-            SetWindowText(window, std::wstring(title).c_str());
-        }
-    }
-
-    bool OnPreKeyEvent(CefRefPtr<CefBrowser> browser,
-                       const CefKeyEvent& event,
-                       CefEventHandle os_event,
-                       bool* is_keyboard_shortcut) override {
-        CEF_REQUIRE_UI_THREAD();
-        UNREFERENCED_PARAMETER(os_event);
-
-        if (event.type == KEYEVENT_RAWKEYDOWN &&
-            (event.modifiers & EVENTFLAG_CONTROL_DOWN) != 0 &&
-            event.windows_key_code == 'T') {
-            if (is_keyboard_shortcut) {
-                *is_keyboard_shortcut = true;
-            }
-            browser->GetMainFrame()->LoadURL(GetHomeUrl());
-            return true;
-        }
-
-        return false;
-    }
-
-    bool OnBeforePopup(CefRefPtr<CefBrowser> browser,
-                       CefRefPtr<CefFrame> frame,
-                       int popup_id,
-                       const CefString& target_url,
-                       const CefString& target_frame_name,
-                       CefLifeSpanHandler::WindowOpenDisposition target_disposition,
-                       bool user_gesture,
-                       const CefPopupFeatures& popupFeatures,
-                       CefWindowInfo& windowInfo,
-                       CefRefPtr<CefClient>& client,
-                       CefBrowserSettings& settings,
-                       CefRefPtr<CefDictionaryValue>& extra_info,
-                       bool* no_javascript_access) override {
-        CEF_REQUIRE_UI_THREAD();
-        UNREFERENCED_PARAMETER(frame);
-        UNREFERENCED_PARAMETER(popup_id);
-        UNREFERENCED_PARAMETER(target_frame_name);
-        UNREFERENCED_PARAMETER(user_gesture);
-        UNREFERENCED_PARAMETER(popupFeatures);
-        UNREFERENCED_PARAMETER(windowInfo);
-        UNREFERENCED_PARAMETER(settings);
-        UNREFERENCED_PARAMETER(extra_info);
-        UNREFERENCED_PARAMETER(no_javascript_access);
-
-        if (target_disposition == CEF_WOD_NEW_WINDOW &&
-            IsEmptyOrChromiumNewTabUrl(target_url)) {
-            client = this;
-            return false;
-        }
-
-        if (IsChromiumNewTabUrl(target_url)) {
-            browser->GetMainFrame()->LoadURL(GetHomeUrl());
-            return true;
-        }
-
-        return false;
-    }
-
-    bool OnBeforeBrowse(CefRefPtr<CefBrowser> browser,
-                        CefRefPtr<CefFrame> frame,
-                        CefRefPtr<CefRequest> request,
-                        bool user_gesture,
-                        bool is_redirect) override {
-        CEF_REQUIRE_UI_THREAD();
-        UNREFERENCED_PARAMETER(browser);
-        UNREFERENCED_PARAMETER(user_gesture);
-        UNREFERENCED_PARAMETER(is_redirect);
-
-        if (frame && frame->IsMain() && request &&
-            IsChromiumNewTabUrl(request->GetURL())) {
-            frame->LoadURL(GetHomeUrl());
-            return true;
-        }
-
-        return false;
-    }
-
-    void OnAfterCreated(CefRefPtr<CefBrowser> browser) override {
-        CEF_REQUIRE_UI_THREAD();
-        ++browser_count_;
-
-        if (browser_count_ > 1 && browser &&
-            IsEmptyOrChromiumNewTabUrl(browser->GetMainFrame()->GetURL())) {
-            browser->GetMainFrame()->LoadURL(GetHomeUrl());
-        }
-    }
-
-    void OnBeforeClose(CefRefPtr<CefBrowser> browser) override {
-        CEF_REQUIRE_UI_THREAD();
-
-        --browser_count_;
-        if (browser_count_ == 0) {
-            CefQuitMessageLoop();
-        }
-    }
-
-    bool OnShowPermissionPrompt(
-        CefRefPtr<CefBrowser> browser,
-        uint64_t prompt_id,
-        const CefString& requesting_origin,
-        uint32_t requested_permissions,
-        CefRefPtr<CefPermissionPromptCallback> callback) override {
-        CEF_REQUIRE_UI_THREAD();
-        UNREFERENCED_PARAMETER(prompt_id);
-        UNREFERENCED_PARAMETER(requesting_origin);
-
-        if ((requested_permissions & CEF_PERMISSION_TYPE_GEOLOCATION) != 0 &&
-            browser && callback &&
-            IsInternalHomeUrl(browser->GetMainFrame()->GetURL())) {
-            callback->Continue(CEF_PERMISSION_RESULT_ACCEPT);
-            return true;
-        }
-
-        return false;
-    }
-
-private:
-    int browser_count_ = 0;
-
-    IMPLEMENT_REFCOUNTING(NebulaClient);
-};
-
-class NebulaApp final : public CefApp {
-public:
-    void OnBeforeCommandLineProcessing(
-        const CefString& process_type,
-        CefRefPtr<CefCommandLine> command_line) override {
-        UNREFERENCED_PARAMETER(process_type);
-
-        // The bundled UI is loaded from file:// and uses ES modules.
-        command_line->AppendSwitch("allow-file-access-from-files");
-    }
-
-private:
-    IMPLEMENT_REFCOUNTING(NebulaApp);
-};
-
-int RunNebula(HINSTANCE instance) {
-    CefMainArgs main_args(instance);
-    CefRefPtr<NebulaApp> app(new NebulaApp);
-
-    const int subprocess_exit_code =
-        CefExecuteProcess(main_args, app, nullptr);
-    if (subprocess_exit_code >= 0) {
-        return subprocess_exit_code;
-    }
-
-    CefSettings settings;
-    settings.no_sandbox = true;
-
-    if (!CefInitialize(main_args, settings, app, nullptr)) {
-        return CefGetExitCode();
-    }
-
-    CefRefPtr<CefCommandLine> command_line = CefCommandLine::CreateCommandLine();
-    command_line->InitFromString(GetCommandLineW());
-
-    std::string url = command_line->GetSwitchValue("url");
-    if (url.empty()) {
-        url = GetHomeUrl();
-    }
-
-    CefWindowInfo window_info;
-    window_info.SetAsPopup(nullptr, "Nebula Browser");
-
-    CefBrowserSettings browser_settings;
-    CefRefPtr<NebulaClient> client(new NebulaClient);
-
-    if (!CefBrowserHost::CreateBrowser(
-            window_info, client, url, browser_settings, nullptr, nullptr)) {
-        CefShutdown();
-        return 1;
-    }
-
-    CefRunMessageLoop();
-    CefShutdown();
-
-    return 0;
-}
-
-}  // namespace
-
 int APIENTRY wWinMain(HINSTANCE instance,
                       HINSTANCE previous_instance,
                       LPWSTR command_line,
                       int show_command) {
-    UNREFERENCED_PARAMETER(previous_instance);
+    NEBULA_UNUSED(previous_instance);
-    UNREFERENCED_PARAMETER(command_line);
+    NEBULA_UNUSED(command_line);
-    UNREFERENCED_PARAMETER(show_command);
 
-    return RunNebula(instance);
+    const nebula::platform::AppStartup startup{instance, show_command};
+    return nebula::app::RunNebula(startup, {nebula::app::AppMode::Desktop});
 }
+#else
+int main(int argc, char* argv[]) {
+#if defined(__APPLE__)
+    CefScopedLibraryLoader library_loader;
+    if (!library_loader.LoadInMain()) {
+        return 1;
+    }
+#endif
+
+    const nebula::platform::AppStartup startup{argc, argv};
+    return nebula::app::RunNebula(startup, {nebula::app::AppMode::Desktop});
+}
+#endif

app/main_bigpicture.cpp

@@ -0,0 +1,33 @@
+#include "app/run.h"
+#include "platform/types.h"
+
+#if defined(_WIN32)
+#include <windows.h>
+#elif defined(__APPLE__)
+#include "include/wrapper/cef_library_loader.h"
+#endif
+
+#if defined(_WIN32)
+int APIENTRY wWinMain(HINSTANCE instance,
+                      HINSTANCE previous_instance,
+                      LPWSTR command_line,
+                      int show_command) {
+    NEBULA_UNUSED(previous_instance);
+    NEBULA_UNUSED(command_line);
+
+    const nebula::platform::AppStartup startup{instance, show_command};
+    return nebula::app::RunNebula(startup, {nebula::app::AppMode::BigPicture});
+}
+#else
+int main(int argc, char* argv[]) {
+#if defined(__APPLE__)
+    CefScopedLibraryLoader library_loader;
+    if (!library_loader.LoadInMain()) {
+        return 1;
+    }
+#endif
+
+    const nebula::platform::AppStartup startup{argc, argv};
+    return nebula::app::RunNebula(startup, {nebula::app::AppMode::BigPicture});
+}
+#endif

app/process_helper_mac.cc

@@ -0,0 +1,25 @@
+#include "cef/nebula_app.h"
+#include "include/cef_app.h"
+#include "include/wrapper/cef_library_loader.h"
+
+#if defined(CEF_USE_SANDBOX)
+#include "include/cef_sandbox_mac.h"
+#endif
+
+int main(int argc, char* argv[]) {
+#if defined(CEF_USE_SANDBOX)
+    CefScopedSandboxContext sandbox_context;
+    if (!sandbox_context.Initialize(argc, argv)) {
+        return 1;
+    }
+#endif
+
+    CefScopedLibraryLoader library_loader;
+    if (!library_loader.LoadInHelper()) {
+        return 1;
+    }
+
+    const CefMainArgs main_args(argc, argv);
+    CefRefPtr<nebula::cef::NebulaApp> app(new nebula::cef::NebulaApp);
+    return CefExecuteProcess(main_args, app, nullptr);
+}

cmake/mac-helper-Info.plist.in

@@ -0,0 +1,39 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>CFBundleDevelopmentRegion</key>
+	<string>en</string>
+	<key>CFBundleDisplayName</key>
+	<string>${EXECUTABLE_NAME}</string>
+	<key>CFBundleExecutable</key>
+	<string>${EXECUTABLE_NAME}</string>
+	<key>CFBundleIdentifier</key>
+	<string>com.nebula.browser.${HELPER_BUNDLE_NAME}.helper${BUNDLE_ID_SUFFIX}</string>
+	<key>CFBundleInfoDictionaryVersion</key>
+	<string>6.0</string>
+	<key>CFBundleName</key>
+	<string>${PRODUCT_NAME}</string>
+	<key>CFBundlePackageType</key>
+	<string>APPL</string>
+	<key>CFBundleSignature</key>
+	<string>????</string>
+	<key>CFBundleVersion</key>
+	<string>1.0</string>
+	<key>CFBundleShortVersionString</key>
+	<string>1.0</string>
+	<key>LSEnvironment</key>
+	<dict>
+		<key>MallocNanoZone</key>
+		<string>0</string>
+	</dict>
+	<key>LSFileQuarantineEnabled</key>
+	<true/>
+	<key>LSMinimumSystemVersion</key>
+	<string>12.0</string>
+	<key>LSUIElement</key>
+	<string>1</string>
+	<key>NSSupportsAutomaticGraphicsSwitching</key>
+	<true/>
+</dict>
+</plist>

compile_commands.json

@@ -0,0 +1 @@
+build/compile_commands.json

docs/cross-platform.md

@@ -0,0 +1,215 @@
+# Cross-platform build guide
+
+Nebula Browser uses a **single codebase** and **one git branch** for Windows, macOS, and Linux. You do not maintain separate platform branches. Instead, each machine unpacks the correct [CEF](https://bitbucket.org/chromiumembedded/cef) binary distribution into `thirdparty/cef/` and builds with CMake.
+
+## Overview
+
+| Layer | Location | Platform-specific? |
+|-------|----------|-------------------|
+| CEF binaries | `thirdparty/cef/` (gitignored) | Yes — one distribution per OS |
+| CMake / deploy | `CMakeLists.txt` | Yes — uses CEF’s `COPY_FILES`, `COPY_MAC_FRAMEWORK`, etc. |
+| App entry & CEF init | `src/app/run.cpp`, `src/platform/*/startup_*.cpp` | Partly |
+| Native window shell | `src/platform/win\|mac\|linux/` | Yes |
+| Browser embedding | `src/platform/*/browser_host_*.cpp` | Partly |
+| Tabs, URLs, UI routing | `src/browser/`, `src/ui/`, `src/cef/` | No (shared) |
+
+**Windows** has a full native shell (custom frame, DWM, embedded CEF views).
+
+**macOS** has a Cocoa native shell (`NSWindow` / `NSView`) with CEF child-view embedding.
+
+**Linux** compiles and links today, but `NebulaWindow::Create()` is still a stub that returns `false` until a real X11 (or GTK) host is implemented.
+
+## Directory layout
+
+```
+thirdparty/cef/          # CEF standard distribution for your OS (not in git)
+
+src/platform/
+  types.h                # Rect, BrowserLayout, NativeWindow, AppStartup
+  startup.h              # PrepareApp, single-instance, CefMainArgs, CefSettings paths
+  browser_host.h         # CefWindowInfo helpers, resize/show/destroy browser HWNDs
+  paths_platform.h       # ExecutableDirectory, DefaultUserDataRoot, PathToUtf8
+
+  win/                   # Windows implementation
+  mac/                   # macOS Cocoa implementation
+  linux/                 # Linux stubs + partial CEF glue
+
+src/window/
+  nebula_window.h        # Platform-agnostic window API (PIMPL)
+
+src/app/                 # Shared controller and run loop
+src/browser/             # Shared tab/session logic
+src/cef/                 # Shared CEF app and browser client
+src/ui/                  # Shared nebula:// URLs and path helpers
+ui/                      # HTML/JS UI (copied next to the binary at build time)
+```
+
+## Prerequisites
+
+- **CMake** 3.21+
+- **C++20** compiler  
+  - Windows: Visual Studio 2022  
+  - macOS: Xcode 16+ (Clang)  
+  - Linux: GCC 10+ or Clang, plus development packages for X11 (CEF’s CMake runs `pkg-config` for X11 on Linux)
+- **CEF standard binary distribution** for your OS and CPU architecture from the [CEF builds](https://cef-builds.spotifycdn.com/index.html) page (or your usual CEF source)
+
+## CEF setup
+
+1. Download the **standard distribution** for your platform (e.g. `cef_binary_*_windows64`, `*_macos*`, `*_linux64`).
+2. Extract so that this path exists:
+
+   ```
+   thirdparty/cef/cmake/FindCEF.cmake
+   ```
+
+3. The rest of the distribution (`Release/`, `Resources/`, `libcef_dll/`, etc.) should sit directly under `thirdparty/cef/` as shipped by CEF.
+
+`thirdparty/cef/` is listed in `.gitignore` so binaries are never committed. Each developer and CI machine supplies its own copy.
+
+## IDE / clangd setup
+
+Without CEF headers, clangd will show many errors (unknown types like `CefWindowInfo`, `CefMainArgs`, etc.). To get full IDE support:
+
+1. Unpack CEF into `thirdparty/cef/` as described above
+2. Generate `compile_commands.json`:
+   ```bash
+   cmake -B build -DCMAKE_EXPORT_COMPILE_COMMANDS=ON
+   ```
+3. Symlink it to the project root:
+   ```bash
+   ln -s build/compile_commands.json .
+   ```
+
+The included `.clangd` file provides fallback flags, but full diagnostics require the compile database.
+
+Optional: override the location at configure time:
+
+```bash
+cmake -B build -DCEF_ROOT=/path/to/cef_binary
+```
+
+## Building
+
+### Windows
+
+```powershell
+cmake -B build
+cmake --build build --config Release
+```
+
+Output: `build/Release/NebulaBrowser.exe` (plus CEF DLLs and `ui/` copied beside it).
+
+### macOS
+
+```bash
+cmake -B build -DPROJECT_ARCH=x86_64   # or arm64 on Apple Silicon
+cmake --build build --config Release
+```
+
+CMake builds a `NebulaBrowser.app` bundle and copies the Chromium Embedded Framework into `Contents/Frameworks`. The macOS port includes a Cocoa `NSWindow` / `NSView` host and child-view embedding for CEF browsers.
+
+CEF **helper app** subprocess targets may still need to be added if the selected CEF distribution does not provide a compatible default subprocess layout. Use CEF’s `cefsimple` sample as the reference for the complete Mac bundle layout.
+
+### Linux
+
+```bash
+cmake -B build
+cmake --build build
+```
+
+Output: `build/NebulaBrowser` (or `build/<Config>/NebulaBrowser` depending on generator). CEF `.so` files and resources are copied next to the executable.
+
+You may need to set **SUID** on `chrome-sandbox` as printed by CMake post-build (CEF documents this in its Linux README).
+
+Until a Linux host window exists, the binary will not show a UI for the same reason as macOS.
+
+## How CMake picks a platform
+
+`find_package(CEF)` loads CEF’s `cef_variables.cmake`, which sets:
+
+- `OS_WINDOWS`
+- `OS_MACOSX`
+- `OS_LINUX`
+
+`CMakeLists.txt` then:
+
+1. Adds the matching `src/platform/{win,mac,linux}/*.cpp` sources
+2. Sets the executable type (`WIN32`, `MACOSX_BUNDLE`, or plain executable)
+3. Links `libcef_dll_wrapper`, `libcef_lib`, and `${CEF_STANDARD_LIBS}`
+4. Runs CEF’s copy macros so runtime files land beside the app
+
+Shared sources are always compiled; only the `src/platform/...` tree changes per OS.
+
+## Application flow
+
+```
+main (app/main.cpp)
+  └─ RunNebula(AppStartup)          src/app/run.cpp
+       ├─ platform::PrepareApp()
+       ├─ CefExecuteProcess()       (subprocesses)
+       ├─ platform::TryAcquireSingleInstance()
+       ├─ CefInitialize()
+       ├─ NebulaController::Create()
+       │    └─ NebulaWindow::Create()   platform-specific
+       └─ CefRunMessageLoop()
+```
+
+`AppStartup` carries platform entry data:
+
+- **Windows:** `HINSTANCE` + show command (`wWinMain`)
+- **macOS / Linux:** `argc` / `argv` (`main`)
+
+## User data and profile paths
+
+Shared logic in `src/ui/paths.cpp` writes under:
+
+| OS | Default root |
+|----|----------------|
+| Windows | `%LOCALAPPDATA%\Nebula\User Data` (falls back to exe directory) |
+| macOS | `~/Library/Application Support/Nebula/User Data` |
+| Linux | `$XDG_DATA_HOME/Nebula/User Data` or `~/.local/share/Nebula/User Data` |
+
+Platform-specific discovery lives in `src/platform/*/paths_*.cpp`.
+
+## GPU / Chromium flags
+
+`src/cef/nebula_app.cpp` applies shared switches (`no-sandbox`, `ignore-gpu-blocklist`, etc.) and platform graphics backends:
+
+| OS | Backend |
+|----|---------|
+| Windows | ANGLE + D3D11 |
+| macOS | ANGLE + Metal |
+| Linux | EGL |
+
+## Adding or changing platform code
+
+1. **Shared behavior** (tabs, `nebula://` URLs, CEF clients) → edit under `src/browser/`, `src/ui/`, `src/cef/`, `src/app/` only if it is truly cross-platform.
+2. **Native window or OS API** → edit `src/platform/<os>/` and keep `src/window/nebula_window.h` free of `#include <windows.h>` (or Cocoa/X11 headers).
+3. **CEF child window embedding** → `src/platform/<os>/browser_host_*.cpp` (`MakeChildWindowInfo`, resize, visibility).
+4. **Startup / paths** → `startup_*.cpp` and `paths_*.cpp` in the same folder.
+5. **New OS** → add `src/platform/<os>/`, extend the `if(OS_...)` blocks in `CMakeLists.txt`, and document CEF distribution layout here.
+
+## Porting checklist (macOS / Linux)
+
+- [x] macOS: implement `NebulaWindow` in `nebula_window_mac.mm`
+- [x] macOS: wire `browser_host_mac.mm` resize/show/raise to Cocoa views
+- [ ] Linux: implement `NebulaWindow` in `nebula_window_linux.cpp`
+- [ ] Linux: wire `browser_host_linux.cpp` resize/show/raise to the real toolkit
+- [ ] macOS: add CEF helper app targets and bundle layout (copy from `cefsimple`)
+- [ ] Linux: confirm X11 (or chosen toolkit) parent handle for `CefWindowInfo::SetAsChild`
+- [ ] Test GPU diagnostics page and hardware acceleration on target hardware
+- [ ] Package or script runtime layout (`ui/`, CEF frameworks/libs, ICU locales, etc.)
+
+## FAQ
+
+**Do I need a separate git branch per OS?**  
+No. Use one branch; swap `thirdparty/cef` and rebuild on each machine.
+
+**Can I commit CEF into the repo?**  
+Not recommended (size, licensing, per-arch binaries). Keeping `thirdparty/cef/` gitignored is intentional.
+
+**Why does Linux build but not run?**
+The Linux window stub intentionally returns `false` from `Create()` until a native shell exists. Shared CEF and browser code are ready; the missing piece is the host window.
+
+**Where is the Windows UI code?**  
+`src/platform/win/nebula_window_win.cpp` — custom chrome, hit-testing, fullscreen, and child browser placement.

src/app/first_run_state.cpp

@@ -0,0 +1,96 @@
+#include "app/first_run_state.h"
+
+#include <cctype>
+#include <filesystem>
+#include <fstream>
+#include <sstream>
+#include <string>
+#include <string_view>
+#include <system_error>
+
+#include "ui/paths.h"
+
+namespace nebula::app {
+namespace {
+
+std::string ReadFile(const std::filesystem::path& path) {
+    std::ifstream input(path, std::ios::binary);
+    if (!input) {
+        return {};
+    }
+
+    std::ostringstream buffer;
+    buffer << input.rdbuf();
+    return buffer.str();
+}
+
+bool ReadFirstStartValue(const std::string& json, bool& first_start) {
+    constexpr std::string_view key = "\"first-start\"";
+    const size_t key_pos = json.find(key);
+    if (key_pos == std::string::npos) {
+        return false;
+    }
+
+    size_t colon = json.find(':', key_pos + key.size());
+    if (colon == std::string::npos) {
+        return false;
+    }
+
+    ++colon;
+    while (colon < json.size() && std::isspace(static_cast<unsigned char>(json[colon]))) {
+        ++colon;
+    }
+
+    if (json.compare(colon, 4, "true") == 0) {
+        first_start = true;
+        return true;
+    }
+    if (json.compare(colon, 5, "false") == 0) {
+        first_start = false;
+        return true;
+    }
+
+    return false;
+}
+
+}  // namespace
+
+bool ShouldShowFirstRunSetup() {
+    const auto path = nebula::ui::GetFirstRunStatePath();
+    if (path.empty()) {
+        return true;
+    }
+
+    const std::string json = ReadFile(path);
+    if (json.empty()) {
+        return true;
+    }
+
+    bool first_start = true;
+    return ReadFirstStartValue(json, first_start) ? first_start : true;
+}
+
+bool WriteFirstRunState(bool first_start) {
+    const auto path = nebula::ui::GetFirstRunStatePath();
+    if (path.empty()) {
+        return false;
+    }
+
+    std::filesystem::path temp_path = path;
+    temp_path += L".tmp";
+    {
+        std::ofstream output(temp_path, std::ios::binary | std::ios::trunc);
+        if (!output) {
+            return false;
+        }
+        output << "{\n  \"first-start\": " << (first_start ? "true" : "false") << "\n}\n";
+    }
+
+    std::error_code ec;
+    std::filesystem::remove(path, ec);
+    ec.clear();
+    std::filesystem::rename(temp_path, path, ec);
+    return !ec;
+}
+
+}  // namespace nebula::app

src/app/first_run_state.h

@@ -0,0 +1,8 @@
+#pragma once
+
+namespace nebula::app {
+
+bool ShouldShowFirstRunSetup();
+bool WriteFirstRunState(bool first_start);
+
+}  // namespace nebula::app

src/app/nebula_controller.h

@@ -0,0 +1,117 @@
+#pragma once
+
+#include <memory>
+#include <string>
+#include <unordered_set>
+#include <vector>
+
+#include "app/run.h"
+#include "browser/tab_manager.h"
+#include "cef/browser_client.h"
+#include "platform/types.h"
+#include "window/nebula_window.h"
+
+namespace nebula::app {
+
+class NebulaController final : public nebula::window::WindowDelegate,
+                              public nebula::browser::TabObserver,
+                              public nebula::cef::BrowserClientDelegate {
+public:
+    NebulaController(nebula::platform::AppStartup startup,
+                     std::string initial_url,
+                     LaunchOptions launch_options = {});
+    ~NebulaController() override;
+
+    bool Create();
+
+    void OnWindowCreated() override;
+    void OnWindowResized(const nebula::window::BrowserLayout& layout) override;
+    void OnWindowCloseRequested() override;
+    void OnExternalOpenRequested(const std::string& target) override;
+
+    void OnActiveTabChanged(const nebula::browser::NebulaTab& tab) override;
+
+    void OnBrowserCreated(nebula::cef::BrowserRole role, CefRefPtr<CefBrowser> browser) override;
+    void OnBrowserClosing(nebula::cef::BrowserRole role, CefRefPtr<CefBrowser> browser) override;
+    void OnChromeCommand(const std::string& command, const std::string& payload) override;
+    void OnContentAddressChanged(CefRefPtr<CefBrowser> browser, const std::string& url) override;
+    void OnContentTitleChanged(CefRefPtr<CefBrowser> browser, const std::string& title) override;
+    void OnContentLoadingStateChanged(CefRefPtr<CefBrowser> browser, bool is_loading) override;
+    void OnContentLoadProgressChanged(CefRefPtr<CefBrowser> browser, double progress) override;
+    void OnContentLoadFinished(CefRefPtr<CefBrowser> browser, const std::string& url) override;
+    void OnContentFaviconChanged(CefRefPtr<CefBrowser> browser, const std::vector<std::string>& urls) override;
+    void OnContentFullscreenChanged(CefRefPtr<CefBrowser> browser, bool fullscreen) override;
+    void OnPopupRequested(CefRefPtr<CefBrowser> browser, const std::string& target_url) override;
+    bool ShouldBypassInsecureWarning(CefRefPtr<CefBrowser> browser, const std::string& target_url) override;
+
+private:
+    void CreateNewTab(std::string url = {});
+    void ActivateTab(int tab_id);
+    void CloseTab(int tab_id);
+    void CreateChromeBrowser();
+    void CreateBigPictureBrowser();
+    void CreateContentBrowser();
+    void EnterBigPictureMode();
+    void ExitBigPictureMode();
+    nebula::window::BrowserLayout CurrentBrowserLayout() const;
+    void ToggleMenuPopup();
+    void CloseMenuPopup();
+    void CreateMenuPopupBrowser();
+    void PositionMenuPopup();
+    void SendMenuPopupZoom();
+    void SendThemeToChromeSurfaces(const std::string& theme_json);
+    void ToggleDevTools();
+    void AdjustZoom(double delta);
+    void FreshReload();
+    void SendBigPictureMouseMove(const std::string& payload);
+    void SendBigPictureMouseClick(const std::string& payload, bool right_click);
+    void SendBigPictureMouseWheel(const std::string& payload);
+    void SendBigPictureText(const std::string& payload);
+    void SetBigPictureBrowseVisible(bool visible);
+    void SetContentFullscreen(bool fullscreen);
+    void CompleteFirstRunSetup();
+    void SendDefaultBrowserResult(const std::string& request_id,
+                                  bool success,
+                                  bool needs_user_action,
+                                  const std::string& error = {});
+    void ResizeBrowsers();
+    void SendChromeState(const nebula::browser::NebulaTab& tab);
+    void SendBigPictureState(const nebula::browser::NebulaTab& tab);
+    void RecordSiteHistory(const std::string& url);
+    void InjectSettingsHistory(CefRefPtr<CefBrowser> browser);
+    void InjectBigPictureCursor(CefRefPtr<CefBrowser> browser);
+    void RemoveBigPictureCursor(CefRefPtr<CefBrowser> browser);
+    void PersistSession() const;
+    void BeginShutdown();
+    void MaybeFinishShutdown();
+    bool ForgetClosingTabBrowser(CefRefPtr<CefBrowser> browser);
+    void LoadPendingNavigationDelayed();
+
+    nebula::platform::AppStartup startup_;
+    std::string initial_url_;
+    std::string pending_initial_navigation_;
+    LaunchOptions launch_options_;
+    bool closing_ = false;
+    bool chrome_ready_ = false;
+    bool big_picture_ready_ = false;
+    bool big_picture_mode_ = false;
+    bool big_picture_browse_visible_ = false;
+    bool content_fullscreen_ = false;
+    bool first_run_setup_active_ = false;
+    bool menu_popup_visible_ = false;
+
+    std::unique_ptr<nebula::window::NebulaWindow> window_;
+    nebula::browser::TabManager tabs_;
+    CefRefPtr<CefBrowser> chrome_browser_;
+    CefRefPtr<CefBrowser> big_picture_browser_;
+    CefRefPtr<CefBrowser> menu_popup_browser_;
+    CefRefPtr<nebula::cef::NebulaBrowserClient> chrome_client_;
+    CefRefPtr<nebula::cef::NebulaBrowserClient> big_picture_client_;
+    CefRefPtr<nebula::cef::NebulaBrowserClient> content_client_;
+    CefRefPtr<nebula::cef::NebulaBrowserClient> menu_popup_client_;
+    std::vector<CefRefPtr<CefBrowser>> closing_tab_browsers_;
+    std::unordered_set<std::string> insecure_warning_bypasses_;
+    std::vector<std::string> site_history_;
+};
+
+}  // namespace nebula::app

src/app/run.cpp

@@ -0,0 +1,153 @@
+#include "app/run.h"
+
+#include "app/nebula_controller.h"
+#include "browser/url_utils.h"
+#include "cef/nebula_app.h"
+#include "include/cef_app.h"
+#include "include/cef_command_line.h"
+#include "platform/default_browser.h"
+#include "platform/startup.h"
+#include "ui/paths.h"
+
+#include <algorithm>
+#include <cctype>
+#include <filesystem>
+#include <system_error>
+#include <vector>
+
+#if defined(_WIN32)
+#include <windows.h>
+#endif
+
+namespace nebula::app {
+namespace {
+
+std::string Trim(std::string value) {
+    while (!value.empty() && std::isspace(static_cast<unsigned char>(value.front()))) {
+        value.erase(value.begin());
+    }
+    while (!value.empty() && std::isspace(static_cast<unsigned char>(value.back()))) {
+        value.pop_back();
+    }
+    return value;
+}
+
+std::string ToLowerAscii(std::string value) {
+    std::transform(value.begin(), value.end(), value.begin(), [](unsigned char ch) {
+        return static_cast<char>(std::tolower(ch));
+    });
+    return value;
+}
+
+bool StartsWithKnownScheme(const std::string& value) {
+    const std::string lower = ToLowerAscii(value);
+    return lower.starts_with("http://") ||
+           lower.starts_with("https://") ||
+           lower.starts_with("file:") ||
+           lower.starts_with("data:") ||
+           lower.starts_with("blob:") ||
+           lower.starts_with("chrome:") ||
+           lower.starts_with("nebula://");
+}
+
+std::filesystem::path PathFromUtf8(const std::string& value) {
+#if defined(_WIN32)
+    const int size = MultiByteToWideChar(
+        CP_UTF8, 0, value.data(), static_cast<int>(value.size()), nullptr, 0);
+    if (size <= 0) {
+        return std::filesystem::path(value);
+    }
+
+    std::wstring wide(size, L'\0');
+    MultiByteToWideChar(
+        CP_UTF8, 0, value.data(), static_cast<int>(value.size()), wide.data(), size);
+    return std::filesystem::path(wide);
+#else
+    return std::filesystem::path(value);
+#endif
+}
+
+std::string NormalizeLaunchTarget(std::string target) {
+    target = Trim(std::move(target));
+    if (target.empty() || nebula::ui::IsChromiumNewTabUrl(target)) {
+        return target.empty() ? std::string{} : nebula::ui::GetHomeUrl();
+    }
+
+    if (StartsWithKnownScheme(target)) {
+        return target;
+    }
+
+    const std::filesystem::path path = PathFromUtf8(target);
+    std::error_code ec;
+    if (!path.empty() && std::filesystem::exists(path, ec) && !ec) {
+        const std::filesystem::path absolute_path = std::filesystem::absolute(path, ec);
+        return nebula::ui::FilePathToUrl(ec ? path : absolute_path);
+    }
+
+    return nebula::browser::NormalizeNavigationInput(target);
+}
+
+std::string GetLaunchTarget(CefRefPtr<CefCommandLine> command_line) {
+    if (!command_line) {
+        return {};
+    }
+
+    std::string target = command_line->GetSwitchValue("url");
+    if (!target.empty()) {
+        return NormalizeLaunchTarget(std::move(target));
+    }
+
+    std::vector<CefString> arguments;
+    command_line->GetArguments(arguments);
+    for (const auto& argument : arguments) {
+        target = argument.ToString();
+        if (!Trim(target).empty()) {
+            return NormalizeLaunchTarget(std::move(target));
+        }
+    }
+
+    return {};
+}
+
+}  // namespace
+
+int RunNebula(const nebula::platform::AppStartup& startup, LaunchOptions options) {
+    nebula::platform::PrepareApp();
+
+    const CefMainArgs main_args = nebula::platform::MakeMainArgs(startup);
+    CefRefPtr<nebula::cef::NebulaApp> app(new nebula::cef::NebulaApp);
+
+    const int subprocess_exit_code = CefExecuteProcess(main_args, app, nullptr);
+    if (subprocess_exit_code >= 0) {
+        return subprocess_exit_code;
+    }
+
+    CefRefPtr<CefCommandLine> command_line = CefCommandLine::CreateCommandLine();
+    nebula::platform::InitCommandLine(command_line, startup);
+    std::string initial_url = GetLaunchTarget(command_line);
+
+    if (!nebula::platform::TryAcquireSingleInstance(initial_url)) {
+        return 0;
+    }
+    nebula::platform::EnsureDefaultBrowserRegistration();
+
+    CefSettings settings;
+    settings.no_sandbox = true;
+    settings.persist_session_cookies = true;
+    nebula::platform::ConfigureCefSettings(settings);
+
+    if (!CefInitialize(main_args, settings, app, nullptr)) {
+        return CefGetExitCode();
+    }
+
+    NebulaController controller(startup, std::move(initial_url), options);
+    const bool created = controller.Create();
+    if (created) {
+        CefRunMessageLoop();
+    }
+
+    CefShutdown();
+    return created ? 0 : 1;
+}
+
+}  // namespace nebula::app

src/app/run.h

@@ -0,0 +1,18 @@
+#pragma once
+
+#include "platform/types.h"
+
+namespace nebula::app {
+
+enum class AppMode {
+    Desktop,
+    BigPicture,
+};
+
+struct LaunchOptions {
+    AppMode mode = AppMode::Desktop;
+};
+
+int RunNebula(const nebula::platform::AppStartup& startup, LaunchOptions options = {});
+
+}  // namespace nebula::app

src/browser/session_state.cpp

@@ -0,0 +1,229 @@
+#include "browser/session_state.h"
+
+#include <algorithm>
+#include <charconv>
+#include <cctype>
+#include <filesystem>
+#include <fstream>
+#include <optional>
+#include <sstream>
+#include <system_error>
+
+#include "browser/url_utils.h"
+#include "ui/paths.h"
+
+namespace nebula::browser {
+namespace {
+
+constexpr size_t kMaxRestoredTabs = 50;
+
+std::string ReadFile(const std::filesystem::path& path) {
+    std::ifstream input(path, std::ios::binary);
+    if (!input) {
+        return {};
+    }
+
+    std::ostringstream buffer;
+    buffer << input.rdbuf();
+    return buffer.str();
+}
+
+std::optional<size_t> ReadUnsignedValue(const std::string& json, std::string_view key) {
+    const size_t key_pos = json.find(key);
+    if (key_pos == std::string::npos) {
+        return std::nullopt;
+    }
+
+    size_t colon = json.find(':', key_pos + key.size());
+    if (colon == std::string::npos) {
+        return std::nullopt;
+    }
+
+    ++colon;
+    while (colon < json.size() && std::isspace(static_cast<unsigned char>(json[colon]))) {
+        ++colon;
+    }
+
+    size_t end = colon;
+    while (end < json.size() && std::isdigit(static_cast<unsigned char>(json[end]))) {
+        ++end;
+    }
+
+    size_t value = 0;
+    const auto result = std::from_chars(json.data() + colon, json.data() + end, value);
+    if (result.ec != std::errc{} || result.ptr != json.data() + end) {
+        return std::nullopt;
+    }
+
+    return value;
+}
+
+std::optional<std::string> ReadStringValue(const std::string& object, std::string_view key) {
+    const size_t key_pos = object.find(key);
+    if (key_pos == std::string::npos) {
+        return std::nullopt;
+    }
+
+    size_t colon = object.find(':', key_pos + key.size());
+    if (colon == std::string::npos) {
+        return std::nullopt;
+    }
+
+    size_t quote = object.find('"', colon + 1);
+    if (quote == std::string::npos) {
+        return std::nullopt;
+    }
+
+    std::string value;
+    for (size_t i = quote + 1; i < object.size(); ++i) {
+        const char ch = object[i];
+        if (ch == '"') {
+            return value;
+        }
+
+        if (ch != '\\') {
+            value += ch;
+            continue;
+        }
+
+        if (++i >= object.size()) {
+            return std::nullopt;
+        }
+
+        switch (object[i]) {
+            case '"':
+            case '\\':
+            case '/':
+                value += object[i];
+                break;
+            case 'b':
+                value += '\b';
+                break;
+            case 'f':
+                value += '\f';
+                break;
+            case 'n':
+                value += '\n';
+                break;
+            case 'r':
+                value += '\r';
+                break;
+            case 't':
+                value += '\t';
+                break;
+            default:
+                return std::nullopt;
+        }
+    }
+
+    return std::nullopt;
+}
+
+std::vector<PersistedTab> ReadTabs(const std::string& json) {
+    std::vector<PersistedTab> tabs;
+    const size_t tabs_pos = json.find("\"tabs\"");
+    if (tabs_pos == std::string::npos) {
+        return tabs;
+    }
+
+    const size_t array_start = json.find('[', tabs_pos);
+    const size_t array_end = json.find(']', array_start == std::string::npos ? tabs_pos : array_start);
+    if (array_start == std::string::npos || array_end == std::string::npos) {
+        return tabs;
+    }
+
+    size_t cursor = array_start + 1;
+    while (cursor < array_end && tabs.size() < kMaxRestoredTabs) {
+        const size_t object_start = json.find('{', cursor);
+        if (object_start == std::string::npos || object_start >= array_end) {
+            break;
+        }
+
+        const size_t object_end = json.find('}', object_start + 1);
+        if (object_end == std::string::npos || object_end > array_end) {
+            break;
+        }
+
+        const std::string object = json.substr(object_start, object_end - object_start + 1);
+        const auto url = ReadStringValue(object, "\"url\"");
+        if (url && !url->empty()) {
+            PersistedTab tab;
+            tab.url = *url;
+            if (const auto title = ReadStringValue(object, "\"title\""); title && !title->empty()) {
+                tab.title = *title;
+            }
+            tabs.push_back(std::move(tab));
+        }
+
+        cursor = object_end + 1;
+    }
+
+    return tabs;
+}
+
+}  // namespace
+
+SessionState LoadSessionState() {
+    SessionState state;
+    const std::string json = ReadFile(nebula::ui::GetSessionStatePath());
+    if (json.empty()) {
+        return state;
+    }
+
+    state.tabs = ReadTabs(json);
+    if (const auto active_index = ReadUnsignedValue(json, "\"activeTabIndex\"")) {
+        state.active_tab_index = *active_index;
+    }
+
+    if (!state.tabs.empty()) {
+        state.active_tab_index = std::min(state.active_tab_index, state.tabs.size() - 1);
+    } else {
+        state.active_tab_index = 0;
+    }
+
+    return state;
+}
+
+void SaveSessionState(const std::vector<NebulaTab>& tabs, size_t active_tab_index) {
+    const auto path = nebula::ui::GetSessionStatePath();
+    if (path.empty()) {
+        return;
+    }
+
+    std::ostringstream json;
+    json << "{\n  \"activeTabIndex\": " << active_tab_index << ",\n  \"tabs\": [\n";
+
+    bool wrote_tab = false;
+    for (const auto& tab : tabs) {
+        if (tab.url.empty()) {
+            continue;
+        }
+
+        if (wrote_tab) {
+            json << ",\n";
+        }
+
+        json << "    {\"url\": \"" << JsonEscape(tab.url)
+             << "\", \"title\": \"" << JsonEscape(tab.title) << "\"}";
+        wrote_tab = true;
+    }
+
+    json << "\n  ]\n}\n";
+
+    std::filesystem::path temp_path = path;
+    temp_path += L".tmp";
+    {
+        std::ofstream output(temp_path, std::ios::binary | std::ios::trunc);
+        if (!output) {
+            return;
+        }
+        output << json.str();
+    }
+
+    std::error_code ec;
+    std::filesystem::remove(path, ec);
+    ec.clear();
+    std::filesystem::rename(temp_path, path, ec);
+}
+
+}  // namespace nebula::browser

src/browser/session_state.h

@@ -0,0 +1,24 @@
+#pragma once
+
+#include <cstddef>
+#include <string>
+#include <vector>
+
+#include "browser/tab.h"
+
+namespace nebula::browser {
+
+struct PersistedTab {
+    std::string url;
+    std::string title = "New Tab";
+};
+
+struct SessionState {
+    std::vector<PersistedTab> tabs;
+    size_t active_tab_index = 0;
+};
+
+SessionState LoadSessionState();
+void SaveSessionState(const std::vector<NebulaTab>& tabs, size_t active_tab_index);
+
+}  // namespace nebula::browser

src/browser/tab.cpp

@@ -0,0 +1,13 @@
+#include "browser/tab.h"
+
+namespace nebula::browser {
+
+bool NebulaTab::CanGoBack() const {
+    return browser && browser->CanGoBack();
+}
+
+bool NebulaTab::CanGoForward() const {
+    return browser && browser->CanGoForward();
+}
+
+}  // namespace nebula::browser

src/browser/tab.h

@@ -0,0 +1,23 @@
+#pragma once
+
+#include <string>
+#include <vector>
+
+#include "include/cef_browser.h"
+
+namespace nebula::browser {
+
+struct NebulaTab {
+    int id = 1;
+    std::string url;
+    std::string title = "New Tab";
+    bool is_loading = false;
+    double load_progress = 0.0;
+    std::string favicon_url;
+    CefRefPtr<CefBrowser> browser;
+
+    bool CanGoBack() const;
+    bool CanGoForward() const;
+};
+
+}  // namespace nebula::browser

src/browser/tab_manager.cpp

@@ -0,0 +1,273 @@
+#include "browser/tab_manager.h"
+
+#include <algorithm>
+
+#include "browser/url_utils.h"
+#include "ui/paths.h"
+
+namespace nebula::browser {
+
+TabManager::TabManager(TabObserver* observer) : observer_(observer) {}
+
+NebulaTab& TabManager::CreateInitialTab(std::string initial_url) {
+    tabs_.clear();
+    NebulaTab tab;
+    tab.id = next_tab_id_++;
+    tab.url = std::move(initial_url);
+    tabs_.push_back(std::move(tab));
+    active_tab_id_ = tabs_.front().id;
+    Notify();
+    return tabs_.front();
+}
+
+NebulaTab& TabManager::CreateTab(std::string url) {
+    NebulaTab tab;
+    tab.id = next_tab_id_++;
+    tab.url = std::move(url);
+    tabs_.push_back(std::move(tab));
+    active_tab_id_ = tabs_.back().id;
+    Notify();
+    return tabs_.back();
+}
+
+void TabManager::RestoreTabs(const std::vector<PersistedTab>& tabs, size_t active_tab_index) {
+    tabs_.clear();
+    active_tab_id_ = 0;
+
+    for (const auto& restored_tab : tabs) {
+        NebulaTab tab;
+        tab.id = next_tab_id_++;
+        tab.url = restored_tab.url.empty() ? nebula::ui::GetHomeUrl() : restored_tab.url;
+        tab.title = restored_tab.title.empty() ? "New Tab" : restored_tab.title;
+        tabs_.push_back(std::move(tab));
+    }
+
+    if (tabs_.empty()) {
+        CreateInitialTab(nebula::ui::GetHomeUrl());
+        return;
+    }
+
+    active_tab_index = std::min(active_tab_index, tabs_.size() - 1);
+    active_tab_id_ = tabs_[active_tab_index].id;
+    Notify();
+}
+
+NebulaTab* TabManager::ActiveTab() {
+    for (auto& tab : tabs_) {
+        if (tab.id == active_tab_id_) {
+            return &tab;
+        }
+    }
+    return nullptr;
+}
+
+const NebulaTab* TabManager::ActiveTab() const {
+    for (const auto& tab : tabs_) {
+        if (tab.id == active_tab_id_) {
+            return &tab;
+        }
+    }
+    return nullptr;
+}
+
+const std::vector<NebulaTab>& TabManager::Tabs() const {
+    return tabs_;
+}
+
+size_t TabManager::ActiveTabIndex() const {
+    for (size_t i = 0; i < tabs_.size(); ++i) {
+        if (tabs_[i].id == active_tab_id_) {
+            return i;
+        }
+    }
+    return 0;
+}
+
+bool TabManager::ActivateTab(int tab_id) {
+    if (!FindTab(tab_id)) {
+        return false;
+    }
+
+    active_tab_id_ = tab_id;
+    Notify();
+    return true;
+}
+
+CefRefPtr<CefBrowser> TabManager::CloseTab(int tab_id) {
+    for (auto it = tabs_.begin(); it != tabs_.end(); ++it) {
+        if (it->id != tab_id) {
+            continue;
+        }
+
+        CefRefPtr<CefBrowser> browser = it->browser;
+        const bool was_active = it->id == active_tab_id_;
+        const auto next_it = tabs_.erase(it);
+
+        if (tabs_.empty()) {
+            active_tab_id_ = 0;
+        } else if (was_active) {
+            active_tab_id_ = next_it != tabs_.end() ? next_it->id : tabs_.back().id;
+        }
+
+        Notify();
+        return browser;
+    }
+
+    return nullptr;
+}
+
+void TabManager::SetActiveBrowser(CefRefPtr<CefBrowser> browser) {
+    if (NebulaTab* tab = ActiveTab()) {
+        tab->browser = browser;
+        if (browser && tab->url.empty()) {
+            tab->url = browser->GetMainFrame()->GetURL();
+        }
+        Notify();
+    }
+}
+
+bool TabManager::OwnsBrowser(CefRefPtr<CefBrowser> browser) const {
+    if (!browser) {
+        return false;
+    }
+
+    for (const auto& tab : tabs_) {
+        if (tab.browser && tab.browser->IsSame(browser)) {
+            return true;
+        }
+    }
+    return false;
+}
+
+bool TabManager::HasOpenBrowsers() const {
+    for (const auto& tab : tabs_) {
+        if (tab.browser) {
+            return true;
+        }
+    }
+    return false;
+}
+
+void TabManager::ClearBrowser(CefRefPtr<CefBrowser> browser) {
+    if (NebulaTab* tab = FindTab(browser)) {
+        tab->browser = nullptr;
+        Notify();
+    }
+}
+
+void TabManager::LoadURL(const std::string& input) {
+    NebulaTab* tab = ActiveTab();
+    if (!tab || !tab->browser) {
+        return;
+    }
+
+    const std::string target = NormalizeNavigationInput(input);
+    if (target.empty()) {
+        return;
+    }
+
+    tab->url = target;
+    tab->favicon_url.clear();
+    tab->browser->GetMainFrame()->LoadURL(nebula::ui::ResolveInternalUrl(target));
+    Notify();
+}
+
+void TabManager::GoBack() {
+    NebulaTab* tab = ActiveTab();
+    if (tab && tab->browser && tab->browser->CanGoBack()) {
+        tab->browser->GoBack();
+    }
+}
+
+void TabManager::GoForward() {
+    NebulaTab* tab = ActiveTab();
+    if (tab && tab->browser && tab->browser->CanGoForward()) {
+        tab->browser->GoForward();
+    }
+}
+
+void TabManager::Reload() {
+    NebulaTab* tab = ActiveTab();
+    if (tab && tab->browser) {
+        tab->browser->Reload();
+    }
+}
+
+void TabManager::StopLoad() {
+    NebulaTab* tab = ActiveTab();
+    if (tab && tab->browser) {
+        tab->browser->StopLoad();
+    }
+}
+
+void TabManager::UpdateURL(CefRefPtr<CefBrowser> browser, std::string url) {
+    if (NebulaTab* tab = FindTab(browser)) {
+        tab->url = std::move(url);
+        Notify();
+    }
+}
+
+void TabManager::UpdateTitle(CefRefPtr<CefBrowser> browser, std::string title) {
+    if (NebulaTab* tab = FindTab(browser)) {
+        tab->title = title.empty() ? "New Tab" : std::move(title);
+        Notify();
+    }
+}
+
+void TabManager::UpdateLoadingState(CefRefPtr<CefBrowser> browser, bool is_loading) {
+    if (NebulaTab* tab = FindTab(browser)) {
+        tab->is_loading = is_loading;
+        if (is_loading) {
+            tab->favicon_url.clear();
+        }
+        if (!is_loading) {
+            tab->load_progress = 1.0;
+        }
+        Notify();
+    }
+}
+
+void TabManager::UpdateLoadProgress(CefRefPtr<CefBrowser> browser, double progress) {
+    if (NebulaTab* tab = FindTab(browser)) {
+        tab->load_progress = progress;
+        Notify();
+    }
+}
+
+void TabManager::UpdateFavicon(CefRefPtr<CefBrowser> browser, const std::vector<std::string>& urls) {
+    if (NebulaTab* tab = FindTab(browser)) {
+        tab->favicon_url = urls.empty() ? std::string{} : urls.front();
+        Notify();
+    }
+}
+
+void TabManager::Notify() {
+    const NebulaTab* tab = ActiveTab();
+    if (observer_ && tab) {
+        observer_->OnActiveTabChanged(*tab);
+    }
+}
+
+NebulaTab* TabManager::FindTab(int tab_id) {
+    for (auto& tab : tabs_) {
+        if (tab.id == tab_id) {
+            return &tab;
+        }
+    }
+    return nullptr;
+}
+
+NebulaTab* TabManager::FindTab(CefRefPtr<CefBrowser> browser) {
+    if (!browser) {
+        return nullptr;
+    }
+
+    for (auto& tab : tabs_) {
+        if (tab.browser && tab.browser->IsSame(browser)) {
+            return &tab;
+        }
+    }
+    return nullptr;
+}
+
+}  // namespace nebula::browser

src/browser/tab_manager.h

@@ -0,0 +1,60 @@
+#pragma once
+
+#include <cstddef>
+#include <string>
+#include <vector>
+
+#include "browser/tab.h"
+#include "browser/session_state.h"
+
+namespace nebula::browser {
+
+class TabObserver {
+public:
+    virtual ~TabObserver() = default;
+    virtual void OnActiveTabChanged(const NebulaTab& tab) = 0;
+};
+
+class TabManager {
+public:
+    explicit TabManager(TabObserver* observer);
+
+    NebulaTab& CreateInitialTab(std::string initial_url);
+    NebulaTab& CreateTab(std::string url);
+    void RestoreTabs(const std::vector<PersistedTab>& tabs, size_t active_tab_index);
+    NebulaTab* ActiveTab();
+    const NebulaTab* ActiveTab() const;
+    const std::vector<NebulaTab>& Tabs() const;
+    size_t ActiveTabIndex() const;
+
+    bool ActivateTab(int tab_id);
+    CefRefPtr<CefBrowser> CloseTab(int tab_id);
+    void SetActiveBrowser(CefRefPtr<CefBrowser> browser);
+    bool OwnsBrowser(CefRefPtr<CefBrowser> browser) const;
+    void ClearBrowser(CefRefPtr<CefBrowser> browser);
+    bool HasOpenBrowsers() const;
+
+    void LoadURL(const std::string& input);
+    void GoBack();
+    void GoForward();
+    void Reload();
+    void StopLoad();
+
+    void UpdateURL(CefRefPtr<CefBrowser> browser, std::string url);
+    void UpdateTitle(CefRefPtr<CefBrowser> browser, std::string title);
+    void UpdateLoadingState(CefRefPtr<CefBrowser> browser, bool is_loading);
+    void UpdateLoadProgress(CefRefPtr<CefBrowser> browser, double progress);
+    void UpdateFavicon(CefRefPtr<CefBrowser> browser, const std::vector<std::string>& urls);
+
+private:
+    void Notify();
+    NebulaTab* FindTab(int tab_id);
+    NebulaTab* FindTab(CefRefPtr<CefBrowser> browser);
+
+    TabObserver* observer_ = nullptr;
+    std::vector<NebulaTab> tabs_;
+    int active_tab_id_ = 0;
+    int next_tab_id_ = 1;
+};
+
+}  // namespace nebula::browser

src/browser/url_utils.cpp

@@ -0,0 +1,115 @@
+#include "browser/url_utils.h"
+
+#include <algorithm>
+#include <cctype>
+#include <iomanip>
+#include <sstream>
+
+namespace nebula::browser {
+namespace {
+
+constexpr char kSearchUrl[] = "https://www.google.com/search?q=";
+
+std::string Trim(std::string value) {
+    while (!value.empty() && std::isspace(static_cast<unsigned char>(value.front()))) {
+        value.erase(value.begin());
+    }
+    while (!value.empty() && std::isspace(static_cast<unsigned char>(value.back()))) {
+        value.pop_back();
+    }
+    return value;
+}
+
+bool StartsWithScheme(std::string value) {
+    std::transform(value.begin(), value.end(), value.begin(), [](unsigned char ch) {
+        return static_cast<char>(std::tolower(ch));
+    });
+    return value.starts_with("http://") ||
+           value.starts_with("https://") ||
+           value.starts_with("file:") ||
+           value.starts_with("data:") ||
+           value.starts_with("blob:") ||
+           value.starts_with("chrome:") ||
+           value.starts_with("nebula://");
+}
+
+bool LooksLikeHostName(const std::string& value) {
+    return value.find('.') != std::string::npos &&
+           value.find_first_of(" \t\r\n") == std::string::npos;
+}
+
+std::string UrlEncodeSearch(const std::string& value) {
+    std::ostringstream encoded;
+    encoded << std::hex << std::uppercase;
+
+    for (unsigned char ch : value) {
+        if (std::isalnum(ch) || ch == '-' || ch == '_' || ch == '.' || ch == '~') {
+            encoded << static_cast<char>(ch);
+        } else if (ch == ' ') {
+            encoded << '+';
+        } else {
+            encoded << '%' << std::setw(2) << std::setfill('0') << static_cast<int>(ch);
+        }
+    }
+
+    return encoded.str();
+}
+
+}  // namespace
+
+std::string NormalizeNavigationInput(const std::string& input) {
+    const std::string value = Trim(input);
+    if (value.empty()) {
+        return {};
+    }
+
+    if (StartsWithScheme(value)) {
+        return value;
+    }
+
+    if (LooksLikeHostName(value)) {
+        return "https://" + value;
+    }
+
+    return std::string(kSearchUrl) + UrlEncodeSearch(value);
+}
+
+std::string JsonEscape(const std::string& value) {
+    std::ostringstream escaped;
+    for (unsigned char ch : value) {
+        switch (ch) {
+            case '\\':
+                escaped << "\\\\";
+                break;
+            case '"':
+                escaped << "\\\"";
+                break;
+            case '\b':
+                escaped << "\\b";
+                break;
+            case '\f':
+                escaped << "\\f";
+                break;
+            case '\n':
+                escaped << "\\n";
+                break;
+            case '\r':
+                escaped << "\\r";
+                break;
+            case '\t':
+                escaped << "\\t";
+                break;
+            default:
+                if (ch < 0x20) {
+                    escaped << "\\u" << std::hex << std::uppercase << std::setw(4)
+                            << std::setfill('0') << static_cast<int>(ch);
+                } else {
+                    escaped << static_cast<char>(ch);
+                }
+                break;
+        }
+    }
+    return escaped.str();
+}
+
+}  // namespace nebula::browser

src/browser/url_utils.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#include <string>
+
+namespace nebula::browser {
+
+std::string NormalizeNavigationInput(const std::string& input);
+std::string JsonEscape(const std::string& value);
+
+}  // namespace nebula::browser

src/cef/browser_client.cpp

@@ -0,0 +1,340 @@
+#include "cef/browser_client.h"
+
+#include "include/cef_request.h"
+#include "platform/types.h"
+#include "include/wrapper/cef_helpers.h"
+#include "ui/paths.h"
+
+namespace nebula::cef {
+namespace {
+
+constexpr char kChromeCommandMessage[] = "NebulaChromeCommand";
+
+bool IsInsecureInterstitialFrame(CefRefPtr<CefFrame> frame) {
+    if (!frame) {
+        return false;
+    }
+
+    return nebula::ui::ToInternalUrl(frame->GetURL().ToString()).starts_with("nebula://insecure");
+}
+
+bool IsSettingsFrame(CefRefPtr<CefFrame> frame) {
+    if (!frame) {
+        return false;
+    }
+
+    return nebula::ui::ToInternalUrl(frame->GetURL().ToString()).starts_with("nebula://settings");
+}
+
+bool IsSetupFrame(CefRefPtr<CefFrame> frame) {
+    if (!frame) {
+        return false;
+    }
+
+    return nebula::ui::ToInternalUrl(frame->GetURL().ToString()).starts_with("nebula://setup");
+}
+
+bool IsBigPictureFrame(CefRefPtr<CefFrame> frame) {
+    if (!frame) {
+        return false;
+    }
+
+    const std::string url = nebula::ui::ToInternalUrl(frame->GetURL().ToString());
+    return url.starts_with("nebula://bigpicture") ||
+           url.starts_with("nebula://big-picture");
+}
+
+bool IsBigPictureCommand(const std::string& command) {
+    return command == "navigate" ||
+           command == "new-tab" ||
+           command == "activate-tab" ||
+           command == "close-tab" ||
+           command == "back" ||
+           command == "forward" ||
+           command == "reload" ||
+           command == "stop" ||
+           command == "home" ||
+           command == "settings" ||
+           command == "open-settings" ||
+           command == "big-picture" ||
+           command == "exit-bigpicture" ||
+           command == "gpu-diagnostics" ||
+           command == "zoom-out" ||
+           command == "zoom-in" ||
+           command == "clear-site-history" ||
+           command == "clear-search-history" ||
+           command == "bigpicture-mouse-move" ||
+           command == "bigpicture-click" ||
+           command == "bigpicture-right-click" ||
+           command == "bigpicture-scroll" ||
+           command == "bigpicture-text" ||
+           command == "bigpicture-browse-visible";
+}
+
+std::vector<std::string> ToStringVector(const std::vector<CefString>& values) {
+    std::vector<std::string> result;
+    result.reserve(values.size());
+    for (const auto& value : values) {
+        result.push_back(value.ToString());
+    }
+    return result;
+}
+
+}  // namespace
+
+NebulaBrowserClient::NebulaBrowserClient(BrowserRole role, BrowserClientDelegate* delegate)
+    : role_(role), delegate_(delegate) {}
+
+bool NebulaBrowserClient::OnProcessMessageReceived(CefRefPtr<CefBrowser> browser,
+                                                   CefRefPtr<CefFrame> frame,
+                                                   CefProcessId source_process,
+                                                   CefRefPtr<CefProcessMessage> message) {
+    CEF_REQUIRE_UI_THREAD();
+    NEBULA_UNUSED(browser);
+    NEBULA_UNUSED(source_process);
+
+    if (!message || message->GetName().ToString() != kChromeCommandMessage) {
+        return false;
+    }
+
+    if (role_ != BrowserRole::Chrome && role_ != BrowserRole::Content &&
+        role_ != BrowserRole::BigPicture && role_ != BrowserRole::MenuPopup) {
+        return false;
+    }
+
+    CefRefPtr<CefListValue> args = message->GetArgumentList();
+    const std::string command = args && args->GetSize() > 0 ? args->GetString(0).ToString() : "";
+    const std::string payload = args && args->GetSize() > 1 ? args->GetString(1).ToString() : "";
+    if (role_ == BrowserRole::Content) {
+        const bool allowed_insecure_command =
+            command == "navigate-insecure" && IsInsecureInterstitialFrame(frame);
+        const bool allowed_settings_command =
+            IsSettingsFrame(frame) && (command == "navigate" ||
+                                       command == "new-tab" ||
+                                       command == "check-default-browser" ||
+                                       command == "set-default-browser" ||
+                                       command == "clear-site-history" ||
+                                       command == "clear-search-history");
+        const bool allowed_setup_command =
+            IsSetupFrame(frame) && (command == "complete-first-run" ||
+                                    command == "check-default-browser" ||
+                                    command == "set-default-browser");
+        const bool allowed_big_picture_command =
+            IsBigPictureFrame(frame) && command == "exit-bigpicture";
+        if (!allowed_insecure_command && !allowed_settings_command &&
+            !allowed_setup_command && !allowed_big_picture_command) {
+            return false;
+        }
+    } else if (role_ == BrowserRole::BigPicture) {
+        if (!IsBigPictureFrame(frame) || !IsBigPictureCommand(command)) {
+            return false;
+        }
+    }
+
+    if (delegate_ && !command.empty()) {
+        delegate_->OnChromeCommand(command, payload);
+        return true;
+    }
+
+    return false;
+}
+
+void NebulaBrowserClient::OnAddressChange(CefRefPtr<CefBrowser> browser,
+                                          CefRefPtr<CefFrame> frame,
+                                          const CefString& url) {
+    CEF_REQUIRE_UI_THREAD();
+    if (role_ == BrowserRole::Content && delegate_ && frame && frame->IsMain()) {
+        delegate_->OnContentAddressChanged(browser, url.ToString());
+    }
+}
+
+void NebulaBrowserClient::OnTitleChange(CefRefPtr<CefBrowser> browser,
+                                        const CefString& title) {
+    CEF_REQUIRE_UI_THREAD();
+    if (role_ == BrowserRole::Content && delegate_) {
+        delegate_->OnContentTitleChanged(browser, title.ToString());
+    }
+}
+
+void NebulaBrowserClient::OnFaviconURLChange(CefRefPtr<CefBrowser> browser,
+                                             const std::vector<CefString>& icon_urls) {
+    CEF_REQUIRE_UI_THREAD();
+    if (role_ == BrowserRole::Content && delegate_) {
+        delegate_->OnContentFaviconChanged(browser, ToStringVector(icon_urls));
+    }
+}
+
+void NebulaBrowserClient::OnFullscreenModeChange(CefRefPtr<CefBrowser> browser, bool fullscreen) {
+    CEF_REQUIRE_UI_THREAD();
+    if (role_ == BrowserRole::Content && delegate_) {
+        delegate_->OnContentFullscreenChanged(browser, fullscreen);
+    }
+}
+
+bool NebulaBrowserClient::OnPreKeyEvent(CefRefPtr<CefBrowser> browser,
+                                        const CefKeyEvent& event,
+                                        CefEventHandle os_event,
+                                        bool* is_keyboard_shortcut) {
+    CEF_REQUIRE_UI_THREAD();
+    NEBULA_UNUSED(os_event);
+
+    if (role_ == BrowserRole::Content &&
+        event.type == KEYEVENT_RAWKEYDOWN &&
+        (event.modifiers & EVENTFLAG_CONTROL_DOWN) != 0 &&
+        event.windows_key_code == 'T') {
+        if (is_keyboard_shortcut) {
+            *is_keyboard_shortcut = true;
+        }
+        if (delegate_) {
+            delegate_->OnPopupRequested(browser, nebula::ui::GetHomeUrl());
+        }
+        return true;
+    }
+
+    return false;
+}
+
+bool NebulaBrowserClient::OnBeforePopup(CefRefPtr<CefBrowser> browser,
+                                        CefRefPtr<CefFrame> frame,
+                                        int popup_id,
+                                        const CefString& target_url,
+                                        const CefString& target_frame_name,
+                                        CefLifeSpanHandler::WindowOpenDisposition target_disposition,
+                                        bool user_gesture,
+                                        const CefPopupFeatures& popupFeatures,
+                                        CefWindowInfo& windowInfo,
+                                        CefRefPtr<CefClient>& client,
+                                        CefBrowserSettings& settings,
+                                        CefRefPtr<CefDictionaryValue>& extra_info,
+                                        bool* no_javascript_access) {
+    CEF_REQUIRE_UI_THREAD();
+    NEBULA_UNUSED(frame);
+    NEBULA_UNUSED(popup_id);
+    NEBULA_UNUSED(target_frame_name);
+    NEBULA_UNUSED(target_disposition);
+    NEBULA_UNUSED(user_gesture);
+    NEBULA_UNUSED(popupFeatures);
+    NEBULA_UNUSED(windowInfo);
+    NEBULA_UNUSED(client);
+    NEBULA_UNUSED(settings);
+    NEBULA_UNUSED(extra_info);
+    NEBULA_UNUSED(no_javascript_access);
+
+    if (role_ == BrowserRole::Content && delegate_) {
+        delegate_->OnPopupRequested(browser, target_url.ToString());
+        return true;
+    }
+
+    return false;
+}
+
+void NebulaBrowserClient::OnAfterCreated(CefRefPtr<CefBrowser> browser) {
+    CEF_REQUIRE_UI_THREAD();
+    if (delegate_) {
+        delegate_->OnBrowserCreated(role_, browser);
+    }
+}
+
+void NebulaBrowserClient::OnBeforeClose(CefRefPtr<CefBrowser> browser) {
+    CEF_REQUIRE_UI_THREAD();
+    if (delegate_) {
+        delegate_->OnBrowserClosing(role_, browser);
+    }
+}
+
+void NebulaBrowserClient::OnLoadingStateChange(CefRefPtr<CefBrowser> browser,
+                                               bool isLoading,
+                                               bool canGoBack,
+                                               bool canGoForward) {
+    CEF_REQUIRE_UI_THREAD();
+    NEBULA_UNUSED(canGoBack);
+    NEBULA_UNUSED(canGoForward);
+
+    if (role_ == BrowserRole::Content && delegate_) {
+        delegate_->OnContentLoadingStateChanged(browser, isLoading);
+    }
+}
+
+void NebulaBrowserClient::OnLoadStart(CefRefPtr<CefBrowser> browser,
+                                      CefRefPtr<CefFrame> frame,
+                                      TransitionType transition_type) {
+    CEF_REQUIRE_UI_THREAD();
+    NEBULA_UNUSED(transition_type);
+
+    if (role_ == BrowserRole::Content && delegate_ && frame && frame->IsMain()) {
+        delegate_->OnContentLoadProgressChanged(browser, 0.12);
+    }
+}
+
+void NebulaBrowserClient::OnLoadEnd(CefRefPtr<CefBrowser> browser,
+                                    CefRefPtr<CefFrame> frame,
+                                    int httpStatusCode) {
+    CEF_REQUIRE_UI_THREAD();
+
+    if (role_ == BrowserRole::Content && delegate_ && frame && frame->IsMain()) {
+        if (httpStatusCode == 404) {
+            frame->LoadURL(nebula::ui::ResolveInternalUrl(
+                nebula::ui::GetNotFoundUrl(frame->GetURL().ToString())));
+            return;
+        }
+
+        delegate_->OnContentLoadProgressChanged(browser, 1.0);
+        delegate_->OnContentLoadFinished(browser, frame->GetURL().ToString());
+    }
+}
+
+bool NebulaBrowserClient::OnBeforeBrowse(CefRefPtr<CefBrowser> browser,
+                                         CefRefPtr<CefFrame> frame,
+                                         CefRefPtr<CefRequest> request,
+                                         bool user_gesture,
+                                         bool is_redirect) {
+    CEF_REQUIRE_UI_THREAD();
+    NEBULA_UNUSED(browser);
+    NEBULA_UNUSED(user_gesture);
+    NEBULA_UNUSED(is_redirect);
+
+    if (role_ == BrowserRole::Content && frame && frame->IsMain() && request) {
+        const std::string url = request->GetURL().ToString();
+        if (nebula::ui::IsChromiumNewTabUrl(url)) {
+            frame->LoadURL(nebula::ui::ResolveInternalUrl(nebula::ui::GetHomeUrl()));
+            return true;
+        }
+
+        if (nebula::ui::IsNebulaInternalUrl(url)) {
+            frame->LoadURL(nebula::ui::ResolveInternalUrl(url));
+            return true;
+        }
+
+        if (nebula::ui::IsHttpUrl(url) &&
+            (!delegate_ || !delegate_->ShouldBypassInsecureWarning(browser, url))) {
+            frame->LoadURL(nebula::ui::ResolveInternalUrl(
+                nebula::ui::GetInsecureWarningUrl(url)));
+            return true;
+        }
+    }
+
+    return false;
+}
+
+bool NebulaBrowserClient::OnShowPermissionPrompt(
+    CefRefPtr<CefBrowser> browser,
+    uint64_t prompt_id,
+    const CefString& requesting_origin,
+    uint32_t requested_permissions,
+    CefRefPtr<CefPermissionPromptCallback> callback) {
+    CEF_REQUIRE_UI_THREAD();
+    NEBULA_UNUSED(prompt_id);
+    NEBULA_UNUSED(requesting_origin);
+
+    if (role_ == BrowserRole::Content &&
+        (requested_permissions & CEF_PERMISSION_TYPE_GEOLOCATION) != 0 &&
+        browser && callback &&
+        nebula::ui::IsInternalHomeUrl(browser->GetMainFrame()->GetURL().ToString())) {
+        callback->Continue(CEF_PERMISSION_RESULT_ACCEPT);
+        return true;
+    }
+
+    return false;
+}
+
+}  // namespace nebula::cef

src/cef/browser_client.h

@@ -0,0 +1,123 @@
+#pragma once
+
+#include <string>
+#include <vector>
+
+#include "include/cef_client.h"
+#include "include/cef_display_handler.h"
+#include "include/cef_keyboard_handler.h"
+#include "include/cef_life_span_handler.h"
+#include "include/cef_load_handler.h"
+#include "include/cef_permission_handler.h"
+#include "include/cef_request_handler.h"
+
+namespace nebula::cef {
+
+enum class BrowserRole {
+    Chrome,
+    Content,
+    BigPicture,
+    MenuPopup,
+};
+
+class BrowserClientDelegate {
+public:
+    virtual ~BrowserClientDelegate() = default;
+    virtual void OnBrowserCreated(BrowserRole role, CefRefPtr<CefBrowser> browser) = 0;
+    virtual void OnBrowserClosing(BrowserRole role, CefRefPtr<CefBrowser> browser) = 0;
+    virtual void OnChromeCommand(const std::string& command, const std::string& payload) = 0;
+    virtual void OnContentAddressChanged(CefRefPtr<CefBrowser> browser, const std::string& url) = 0;
+    virtual void OnContentTitleChanged(CefRefPtr<CefBrowser> browser, const std::string& title) = 0;
+    virtual void OnContentLoadingStateChanged(CefRefPtr<CefBrowser> browser, bool is_loading) = 0;
+    virtual void OnContentLoadProgressChanged(CefRefPtr<CefBrowser> browser, double progress) = 0;
+    virtual void OnContentLoadFinished(CefRefPtr<CefBrowser> browser, const std::string& url) = 0;
+    virtual void OnContentFaviconChanged(CefRefPtr<CefBrowser> browser, const std::vector<std::string>& urls) = 0;
+    virtual void OnContentFullscreenChanged(CefRefPtr<CefBrowser> browser, bool fullscreen) = 0;
+    virtual void OnPopupRequested(CefRefPtr<CefBrowser> browser, const std::string& target_url) = 0;
+    virtual bool ShouldBypassInsecureWarning(CefRefPtr<CefBrowser> browser, const std::string& target_url) = 0;
+};
+
+class NebulaBrowserClient final : public CefClient,
+                                 public CefDisplayHandler,
+                                 public CefKeyboardHandler,
+                                 public CefLifeSpanHandler,
+                                 public CefLoadHandler,
+                                 public CefPermissionHandler,
+                                 public CefRequestHandler {
+public:
+    NebulaBrowserClient(BrowserRole role, BrowserClientDelegate* delegate);
+
+    CefRefPtr<CefDisplayHandler> GetDisplayHandler() override { return this; }
+    CefRefPtr<CefKeyboardHandler> GetKeyboardHandler() override { return this; }
+    CefRefPtr<CefLifeSpanHandler> GetLifeSpanHandler() override { return this; }
+    CefRefPtr<CefLoadHandler> GetLoadHandler() override { return this; }
+    CefRefPtr<CefPermissionHandler> GetPermissionHandler() override { return this; }
+    CefRefPtr<CefRequestHandler> GetRequestHandler() override { return this; }
+
+    bool OnProcessMessageReceived(CefRefPtr<CefBrowser> browser,
+                                  CefRefPtr<CefFrame> frame,
+                                  CefProcessId source_process,
+                                  CefRefPtr<CefProcessMessage> message) override;
+
+    void OnAddressChange(CefRefPtr<CefBrowser> browser,
+                         CefRefPtr<CefFrame> frame,
+                         const CefString& url) override;
+    void OnTitleChange(CefRefPtr<CefBrowser> browser,
+                       const CefString& title) override;
+    void OnFaviconURLChange(CefRefPtr<CefBrowser> browser,
+                            const std::vector<CefString>& icon_urls) override;
+    void OnFullscreenModeChange(CefRefPtr<CefBrowser> browser, bool fullscreen) override;
+
+    bool OnPreKeyEvent(CefRefPtr<CefBrowser> browser,
+                       const CefKeyEvent& event,
+                       CefEventHandle os_event,
+                       bool* is_keyboard_shortcut) override;
+
+    bool OnBeforePopup(CefRefPtr<CefBrowser> browser,
+                       CefRefPtr<CefFrame> frame,
+                       int popup_id,
+                       const CefString& target_url,
+                       const CefString& target_frame_name,
+                       CefLifeSpanHandler::WindowOpenDisposition target_disposition,
+                       bool user_gesture,
+                       const CefPopupFeatures& popupFeatures,
+                       CefWindowInfo& windowInfo,
+                       CefRefPtr<CefClient>& client,
+                       CefBrowserSettings& settings,
+                       CefRefPtr<CefDictionaryValue>& extra_info,
+                       bool* no_javascript_access) override;
+
+    void OnAfterCreated(CefRefPtr<CefBrowser> browser) override;
+    void OnBeforeClose(CefRefPtr<CefBrowser> browser) override;
+
+    void OnLoadingStateChange(CefRefPtr<CefBrowser> browser,
+                              bool isLoading,
+                              bool canGoBack,
+                              bool canGoForward) override;
+    void OnLoadStart(CefRefPtr<CefBrowser> browser,
+                     CefRefPtr<CefFrame> frame,
+                     TransitionType transition_type) override;
+    void OnLoadEnd(CefRefPtr<CefBrowser> browser,
+                   CefRefPtr<CefFrame> frame,
+                   int httpStatusCode) override;
+
+    bool OnBeforeBrowse(CefRefPtr<CefBrowser> browser,
+                        CefRefPtr<CefFrame> frame,
+                        CefRefPtr<CefRequest> request,
+                        bool user_gesture,
+                        bool is_redirect) override;
+
+    bool OnShowPermissionPrompt(CefRefPtr<CefBrowser> browser,
+                                uint64_t prompt_id,
+                                const CefString& requesting_origin,
+                                uint32_t requested_permissions,
+                                CefRefPtr<CefPermissionPromptCallback> callback) override;
+
+private:
+    BrowserRole role_;
+    BrowserClientDelegate* delegate_ = nullptr;
+
+    IMPLEMENT_REFCOUNTING(NebulaBrowserClient);
+};
+
+}  // namespace nebula::cef

src/cef/nebula_app.cpp

@@ -0,0 +1,119 @@
+#include "cef/nebula_app.h"
+
+#include "include/cef_process_message.h"
+#include "platform/types.h"
+#include "include/wrapper/cef_helpers.h"
+
+namespace nebula::cef {
+namespace {
+
+constexpr char kChromeCommandMessage[] = "NebulaChromeCommand";
+
+class NativeBridgeHandler final : public CefV8Handler {
+public:
+    bool Execute(const CefString& name,
+                 CefRefPtr<CefV8Value> object,
+                 const CefV8ValueList& arguments,
+                 CefRefPtr<CefV8Value>& retval,
+                 CefString& exception) override {
+        NEBULA_UNUSED(object);
+        NEBULA_UNUSED(retval);
+
+        if (name != "postMessage" && name != "sendToHost" && name != "send") {
+            return false;
+        }
+
+        if (arguments.empty() || !arguments[0]->IsString()) {
+            exception = "nebulaNative.postMessage requires a command string.";
+            return true;
+        }
+
+        CefRefPtr<CefV8Context> context = CefV8Context::GetCurrentContext();
+        CefRefPtr<CefBrowser> browser = context ? context->GetBrowser() : nullptr;
+        CefRefPtr<CefFrame> frame = context ? context->GetFrame() : nullptr;
+        if (!browser || !frame) {
+            exception = "No CEF frame is available for native messaging.";
+            return true;
+        }
+
+        CefRefPtr<CefProcessMessage> message = CefProcessMessage::Create(kChromeCommandMessage);
+        CefRefPtr<CefListValue> args = message->GetArgumentList();
+        args->SetString(0, arguments[0]->GetStringValue());
+        args->SetString(1, arguments.size() > 1 && arguments[1]->IsString()
+                               ? arguments[1]->GetStringValue()
+                               : CefString());
+
+        frame->SendProcessMessage(PID_BROWSER, message);
+        return true;
+    }
+
+private:
+    IMPLEMENT_REFCOUNTING(NativeBridgeHandler);
+};
+
+}  // namespace
+
+void NebulaApp::OnBeforeCommandLineProcessing(const CefString& process_type,
+                                              CefRefPtr<CefCommandLine> command_line) {
+    NEBULA_UNUSED(process_type);
+
+    // The bundled UI is loaded from file:// and uses ES modules.
+    command_line->AppendSwitch("allow-file-access-from-files");
+
+    // CefSettings.no_sandbox disables the browser-level sandbox, but Chromium
+    // still attempts to bring up a separate GPU sandbox inside the GPU process.
+    // Without the host-side sandbox plumbing this fails with STATUS_BREAKPOINT
+    // (-2147483645) immediately on startup, which is exactly what the GPU
+    // diagnostics page was showing - the GPU process crashed three times and
+    // Chromium then fell back to software rendering. Disabling the GPU sandbox
+    // matches the rest of our no_sandbox configuration and lets the GPU
+    // process initialize.
+    command_line->AppendSwitch("no-sandbox");
+    command_line->AppendSwitch("disable-gpu-sandbox");
+    command_line->AppendSwitch("in-process-gpu");
+
+    // Avoid Chromium's conservative GPU blocklist, but let Chromium choose the
+    // safest graphics backend for this machine. Forcing raster/zero-copy paths
+    // can prevent WebGL shared contexts from initializing on some drivers.
+    command_line->AppendSwitch("ignore-gpu-blocklist");
+    command_line->AppendSwitch("enable-accelerated-video-decode");
+
+#if defined(_WIN32)
+    command_line->AppendSwitchWithValue("use-gl", "angle");
+    command_line->AppendSwitchWithValue("use-angle", "d3d11");
+#elif defined(__APPLE__)
+    command_line->AppendSwitchWithValue("use-angle", "metal");
+#else
+    command_line->AppendSwitchWithValue("use-gl", "egl");
+#endif
+}
+
+void NebulaApp::OnContextCreated(CefRefPtr<CefBrowser> browser,
+                                 CefRefPtr<CefFrame> frame,
+                                 CefRefPtr<CefV8Context> context) {
+    CEF_REQUIRE_RENDERER_THREAD();
+    NEBULA_UNUSED(browser);
+    NEBULA_UNUSED(frame);
+
+    CefRefPtr<CefV8Value> global = context->GetGlobal();
+    CefRefPtr<NativeBridgeHandler> handler = new NativeBridgeHandler();
+    CefRefPtr<CefV8Value> native = CefV8Value::CreateObject(nullptr, nullptr);
+    native->SetValue(
+        "postMessage",
+        CefV8Value::CreateFunction("postMessage", handler),
+        V8_PROPERTY_ATTRIBUTE_NONE);
+    global->SetValue("nebulaNative", native, V8_PROPERTY_ATTRIBUTE_READONLY);
+
+    CefRefPtr<CefV8Value> electron_api = CefV8Value::CreateObject(nullptr, nullptr);
+    electron_api->SetValue(
+        "sendToHost",
+        CefV8Value::CreateFunction("sendToHost", handler),
+        V8_PROPERTY_ATTRIBUTE_NONE);
+    electron_api->SetValue(
+        "send",
+        CefV8Value::CreateFunction("send", handler),
+        V8_PROPERTY_ATTRIBUTE_NONE);
+    global->SetValue("electronAPI", electron_api, V8_PROPERTY_ATTRIBUTE_READONLY);
+}
+
+}  // namespace nebula::cef

src/cef/nebula_app.h

@@ -0,0 +1,25 @@
+#pragma once
+
+#include "include/cef_app.h"
+#include "include/cef_render_process_handler.h"
+#include "include/cef_v8.h"
+
+namespace nebula::cef {
+
+class NebulaApp final : public CefApp,
+                       public CefRenderProcessHandler {
+public:
+    CefRefPtr<CefRenderProcessHandler> GetRenderProcessHandler() override { return this; }
+
+    void OnBeforeCommandLineProcessing(const CefString& process_type,
+                                       CefRefPtr<CefCommandLine> command_line) override;
+
+    void OnContextCreated(CefRefPtr<CefBrowser> browser,
+                          CefRefPtr<CefFrame> frame,
+                          CefRefPtr<CefV8Context> context) override;
+
+private:
+    IMPLEMENT_REFCOUNTING(NebulaApp);
+};
+
+}  // namespace nebula::cef

src/platform/browser_host.h

@@ -0,0 +1,23 @@
+#pragma once
+
+#include <string>
+#include <utility>
+
+#include "include/cef_browser.h"
+#include "platform/types.h"
+
+namespace nebula::platform {
+
+CefWindowInfo MakeChildWindowInfo(NativeWindow parent, const Rect& rect);
+CefWindowInfo MakeDevToolsPopup(NativeWindow parent, const char* title);
+void ResizeBrowserWindow(NativeWindow browser_window, const Rect& rect);
+void SetBrowserVisible(NativeWindow browser_window, bool visible);
+void RaiseBrowserWindow(NativeWindow browser_window);
+void MoveCursorToBrowserPoint(NativeWindow browser_window, int x, int y);
+Rect MenuPopupRect(NativeWindow parent, const BrowserLayout& layout);
+std::string CacheBusterToken();
+void DestroyTopLevelWindow(NativeWindow window);
+int ScaleForParentWindow(NativeWindow parent, int value);
+std::pair<int, int> ParentClientSize(NativeWindow parent);
+
+}  // namespace nebula::platform

src/platform/default_browser.h

@@ -0,0 +1,9 @@
+#pragma once
+
+namespace nebula::platform {
+
+bool IsDefaultBrowser();
+bool EnsureDefaultBrowserRegistration();
+bool RequestDefaultBrowser();
+
+}  // namespace nebula::platform

src/platform/linux/browser_host_linux.cpp

@@ -0,0 +1,77 @@
+#include "platform/browser_host.h"
+
+#include <algorithm>
+
+namespace nebula::platform {
+
+CefWindowInfo MakeChildWindowInfo(NativeWindow parent, const Rect& rect) {
+    CefWindowInfo info;
+    info.SetAsChild(
+        reinterpret_cast<CefWindowHandle>(parent),
+        CefRect(rect.x, rect.y, rect.width, rect.height));
+    info.runtime_style = CEF_RUNTIME_STYLE_ALLOY;
+    return info;
+}
+
+CefWindowInfo MakeDevToolsPopup(NativeWindow parent, const char* title) {
+    CefWindowInfo info;
+    info.SetAsPopup(reinterpret_cast<CefWindowHandle>(parent), title);
+    info.runtime_style = CEF_RUNTIME_STYLE_ALLOY;
+    return info;
+}
+
+void ResizeBrowserWindow(NativeWindow browser_window, const Rect& rect) {
+    NEBULA_UNUSED(browser_window);
+    NEBULA_UNUSED(rect);
+}
+
+void SetBrowserVisible(NativeWindow browser_window, bool visible) {
+    NEBULA_UNUSED(browser_window);
+    NEBULA_UNUSED(visible);
+}
+
+void RaiseBrowserWindow(NativeWindow browser_window) {
+    NEBULA_UNUSED(browser_window);
+}
+
+void MoveCursorToBrowserPoint(NativeWindow browser_window, int x, int y) {
+    NEBULA_UNUSED(browser_window);
+    NEBULA_UNUSED(x);
+    NEBULA_UNUSED(y);
+}
+
+int ScaleForParentWindow(NativeWindow parent, int value) {
+    NEBULA_UNUSED(parent);
+    return value;
+}
+
+std::pair<int, int> ParentClientSize(NativeWindow parent) {
+    NEBULA_UNUSED(parent);
+    return {1280, 720};
+}
+
+Rect MenuPopupRect(NativeWindow parent, const BrowserLayout& layout) {
+    const auto client_size = ParentClientSize(parent);
+    const int width = 260;
+    const int height = 258;
+    const int margin = 12;
+    const int overlap = 2;
+    const int x = std::max(0, client_size.first - width - margin);
+    const int y = std::max(0, layout.chrome.y + layout.chrome.height - overlap);
+    return {
+        x,
+        y,
+        std::min(client_size.first, x + width) - x,
+        std::min(client_size.second, y + height) - y,
+    };
+}
+
+std::string CacheBusterToken() {
+    return "0";
+}
+
+void DestroyTopLevelWindow(NativeWindow window) {
+    NEBULA_UNUSED(window);
+}
+
+}  // namespace nebula::platform

src/platform/linux/default_browser_linux.cpp

@@ -0,0 +1,17 @@
+#include "platform/default_browser.h"
+
+namespace nebula::platform {
+
+bool IsDefaultBrowser() {
+    return false;
+}
+
+bool EnsureDefaultBrowserRegistration() {
+    return false;
+}
+
+bool RequestDefaultBrowser() {
+    return false;
+}
+
+}  // namespace nebula::platform

src/platform/linux/nebula_window_linux.cpp

@@ -0,0 +1,45 @@
+#include "window/nebula_window.h"
+
+#include <memory>
+
+namespace nebula::window {
+
+struct nebula::window::NebulaWindowImpl {
+    WindowDelegate* delegate = nullptr;
+};
+
+NebulaWindow::NebulaWindow(WindowDelegate* delegate)
+    : impl_(std::make_unique<NebulaWindowImpl>()) {
+    impl_->delegate = delegate;
+}
+
+NebulaWindow::~NebulaWindow() = default;
+
+bool NebulaWindow::Create(const platform::AppStartup& startup) {
+    NEBULA_UNUSED(startup);
+    return false;
+}
+
+platform::NativeWindow NebulaWindow::native_handle() const {
+    return nullptr;
+}
+
+BrowserLayout NebulaWindow::CurrentLayout(bool show_chrome) const {
+    NEBULA_UNUSED(show_chrome);
+    return {};
+}
+
+void NebulaWindow::ResizeChild(platform::NativeWindow child, const platform::Rect& rect) const {
+    NEBULA_UNUSED(child);
+    NEBULA_UNUSED(rect);
+}
+
+void NebulaWindow::Minimize() {}
+void NebulaWindow::ToggleMaximize() {}
+void NebulaWindow::SetFullscreen(bool fullscreen) { NEBULA_UNUSED(fullscreen); }
+void NebulaWindow::Close() {}
+void NebulaWindow::BeginDrag() {}
+void NebulaWindow::SetTitle(const std::string& title) { NEBULA_UNUSED(title); }
+void NebulaWindow::EnableFrameHitTest(platform::NativeWindow child) const { NEBULA_UNUSED(child); }
+
+}  // namespace nebula::window

src/platform/linux/paths_linux.cpp

@@ -0,0 +1,41 @@
+#include "platform/paths_platform.h"
+
+#include <pwd.h>
+#include <unistd.h>
+
+#include <cstdlib>
+
+namespace nebula::platform {
+
+std::filesystem::path ExecutableDirectory() {
+    char buffer[4096] = {};
+    const ssize_t length = readlink("/proc/self/exe", buffer, sizeof(buffer) - 1);
+    if (length <= 0) {
+        return {};
+    }
+
+    buffer[length] = '\0';
+    return std::filesystem::path(buffer).parent_path();
+}
+
+std::filesystem::path DefaultUserDataRoot() {
+    if (const char* xdg_data = std::getenv("XDG_DATA_HOME"); xdg_data && *xdg_data) {
+        return std::filesystem::path(xdg_data);
+    }
+
+    if (const char* home = std::getenv("HOME")) {
+        return std::filesystem::path(home) / ".local" / "share";
+    }
+
+    if (passwd* pw = getpwuid(getuid())) {
+        return std::filesystem::path(pw->pw_dir) / ".local" / "share";
+    }
+
+    return ExecutableDirectory();
+}
+
+std::string PathToUtf8(const std::filesystem::path& path) {
+    return path.string();
+}
+
+}  // namespace nebula::platform

src/platform/linux/startup_linux.cpp

@@ -0,0 +1,55 @@
+#include "platform/startup.h"
+
+#include <fcntl.h>
+#include <filesystem>
+#include <system_error>
+#include <sys/file.h>
+#include <unistd.h>
+
+#include "include/cef_command_line.h"
+#include "ui/paths.h"
+
+namespace nebula::platform {
+namespace {
+
+int g_single_instance_lock = -1;
+
+}  // namespace
+
+void PrepareApp() {}
+
+bool TryAcquireSingleInstance(const std::string& launch_target) {
+    NEBULA_UNUSED(launch_target);
+
+    const auto lock_path = nebula::ui::GetUserDataDirectory() / ".nebula_instance.lock";
+    std::error_code ec;
+    std::filesystem::create_directories(lock_path.parent_path(), ec);
+
+    g_single_instance_lock = open(lock_path.c_str(), O_CREAT | O_RDWR, 0644);
+    if (g_single_instance_lock < 0) {
+        return true;
+    }
+
+    return flock(g_single_instance_lock, LOCK_EX | LOCK_NB) == 0;
+}
+
+CefMainArgs MakeMainArgs(const AppStartup& startup) {
+    return CefMainArgs(startup.argc, startup.argv);
+}
+
+void InitCommandLine(CefRefPtr<CefCommandLine> command_line, const AppStartup& startup) {
+    command_line->InitFromArgv(startup.argc, startup.argv);
+}
+
+void ConfigureCefSettings(CefSettings& settings) {
+    const std::string user_data_dir = nebula::ui::GetUserDataDirectory().string();
+    const std::string cache_dir = nebula::ui::GetCacheDirectory().string();
+    if (!user_data_dir.empty()) {
+        CefString(&settings.root_cache_path).FromString(user_data_dir);
+    }
+    if (!cache_dir.empty()) {
+        CefString(&settings.cache_path).FromString(cache_dir);
+    }
+}
+
+}  // namespace nebula::platform

src/platform/mac/browser_host_mac.mm

@@ -0,0 +1,134 @@
+#include "platform/browser_host.h"
+
+#import <ApplicationServices/ApplicationServices.h>
+#import <Cocoa/Cocoa.h>
+
+#include <algorithm>
+#include <chrono>
+#include <cmath>
+
+namespace nebula::platform {
+namespace {
+
+NSView* AsView(NativeWindow window) {
+    return (__bridge NSView*)window;
+}
+
+NSRect ToNativeRect(const Rect& rect) {
+    return NSMakeRect(rect.x, rect.y, std::max(0, rect.width), std::max(0, rect.height));
+}
+
+Rect ToPlatformRect(NSRect rect) {
+    return {
+        static_cast<int>(std::round(NSMinX(rect))),
+        static_cast<int>(std::round(NSMinY(rect))),
+        std::max(0, static_cast<int>(std::round(NSWidth(rect)))),
+        std::max(0, static_cast<int>(std::round(NSHeight(rect)))),
+    };
+}
+
+}  // namespace
+
+CefWindowInfo MakeChildWindowInfo(NativeWindow parent, const Rect& rect) {
+    CefWindowInfo info;
+    info.SetAsChild((__bridge CefWindowHandle)AsView(parent),
+                    CefRect(rect.x, rect.y, rect.width, rect.height));
+    info.runtime_style = CEF_RUNTIME_STYLE_ALLOY;
+    return info;
+}
+
+CefWindowInfo MakeDevToolsPopup(NativeWindow parent, const char* title) {
+    (void)title;
+    CefWindowInfo info;
+    info.SetAsChild((__bridge CefWindowHandle)AsView(parent), CefRect(0, 0, 800, 600));
+    info.runtime_style = CEF_RUNTIME_STYLE_ALLOY;
+    return info;
+}
+
+void ResizeBrowserWindow(NativeWindow browser_window, const Rect& rect) {
+    NSView* view = AsView(browser_window);
+    if (!view) {
+        return;
+    }
+
+    [view setFrame:ToNativeRect(rect)];
+}
+
+void SetBrowserVisible(NativeWindow browser_window, bool visible) {
+    NSView* view = AsView(browser_window);
+    if (!view) {
+        return;
+    }
+
+    [view setHidden:!visible];
+    if (visible && [view superview]) {
+        [[view superview] addSubview:view positioned:NSWindowAbove relativeTo:nil];
+    }
+}
+
+void RaiseBrowserWindow(NativeWindow browser_window) {
+    NSView* view = AsView(browser_window);
+    if (view && [view superview]) {
+        [[view superview] addSubview:view positioned:NSWindowAbove relativeTo:nil];
+    }
+}
+
+void MoveCursorToBrowserPoint(NativeWindow browser_window, int x, int y) {
+    NSView* view = AsView(browser_window);
+    if (!view || ![view window]) {
+        return;
+    }
+
+    const NSPoint window_point = [view convertPoint:NSMakePoint(x, y) toView:nil];
+    const NSPoint screen_point = [[view window] convertPointToScreen:window_point];
+    const CGFloat screen_height = NSMaxY([[NSScreen mainScreen] frame]);
+    CGWarpMouseCursorPosition(CGPointMake(screen_point.x, screen_height - screen_point.y));
+}
+
+int ScaleForParentWindow(NativeWindow parent, int value) {
+    (void)parent;
+    return value;
+}
+
+std::pair<int, int> ParentClientSize(NativeWindow parent) {
+    NSView* view = AsView(parent);
+    if (!view) {
+        return {0, 0};
+    }
+
+    const Rect rect = ToPlatformRect([view bounds]);
+    return {rect.width, rect.height};
+}
+
+Rect MenuPopupRect(NativeWindow parent, const BrowserLayout& layout) {
+    const auto client_size = ParentClientSize(parent);
+    const int width = 260;
+    const int height = 258;
+    const int margin = 12;
+    const int overlap = 2;
+    const int x = std::max(0, client_size.first - width - margin);
+    const int y = std::max(0, layout.chrome.y + layout.chrome.height - overlap);
+    return {
+        x,
+        y,
+        std::min(client_size.first, x + width) - x,
+        std::min(client_size.second, y + height) - y,
+    };
+}
+
+std::string CacheBusterToken() {
+    const auto now = std::chrono::system_clock::now().time_since_epoch();
+    const auto millis = std::chrono::duration_cast<std::chrono::milliseconds>(now).count();
+    return std::to_string(millis);
+}
+
+void DestroyTopLevelWindow(NativeWindow window) {
+    NSView* view = AsView(window);
+    NSWindow* native_window = [view window];
+    if (native_window) {
+        [native_window setDelegate:nil];
+        [native_window close];
+    }
+}
+
+}  // namespace nebula::platform

src/platform/mac/default_browser_mac.mm

@@ -0,0 +1,17 @@
+#include "platform/default_browser.h"
+
+namespace nebula::platform {
+
+bool IsDefaultBrowser() {
+    return false;
+}
+
+bool EnsureDefaultBrowserRegistration() {
+    return false;
+}
+
+bool RequestDefaultBrowser() {
+    return false;
+}
+
+}  // namespace nebula::platform

src/platform/mac/nebula_window_mac.mm

@@ -0,0 +1,222 @@
+#include "window/nebula_window.h"
+
+#import <Cocoa/Cocoa.h>
+
+#include <algorithm>
+#include <cmath>
+#include <memory>
+
+namespace nebula::window {
+struct NebulaWindowImpl;
+}  // namespace nebula::window
+
+@interface NebulaContentView : NSView
+@end
+
+@implementation NebulaContentView
+- (BOOL)isFlipped {
+    return YES;
+}
+@end
+
+@interface NebulaWindowDelegate : NSObject <NSWindowDelegate> {
+@private
+    nebula::window::NebulaWindowImpl* owner_;
+}
+- (instancetype)initWithOwner:(nebula::window::NebulaWindowImpl*)owner;
+@end
+
+namespace nebula::window {
+namespace {
+
+constexpr CGFloat kChromeHeight = 104.0;
+
+NSRect ToNativeRect(const platform::Rect& rect) {
+    return NSMakeRect(rect.x, rect.y, std::max(0, rect.width), std::max(0, rect.height));
+}
+
+}  // namespace
+
+struct NebulaWindowImpl {
+    WindowDelegate* delegate = nullptr;
+    NSWindow* window = nil;
+    NebulaContentView* content_view = nil;
+    NebulaWindowDelegate* window_delegate = nil;
+    bool fullscreen = false;
+
+    BrowserLayout CurrentLayout(bool show_chrome) const {
+        const NSRect bounds = content_view ? [content_view bounds] : NSZeroRect;
+        const int width = std::max(0, static_cast<int>(std::round(NSWidth(bounds))));
+        const int height = std::max(0, static_cast<int>(std::round(NSHeight(bounds))));
+        const int chrome_height = show_chrome ? std::min(height, static_cast<int>(kChromeHeight)) : 0;
+
+        BrowserLayout layout;
+        layout.chrome = show_chrome ? platform::Rect{0, 0, width, chrome_height} : platform::Rect{};
+        layout.content = {0, chrome_height, width, std::max(0, height - chrome_height)};
+        return layout;
+    }
+
+    void NotifyCreated() const {
+        if (delegate) {
+            delegate->OnWindowCreated();
+        }
+    }
+
+    void NotifyResized() const {
+        if (delegate) {
+            delegate->OnWindowResized(CurrentLayout(true));
+        }
+    }
+
+    void NotifyCloseRequested() const {
+        if (delegate) {
+            delegate->OnWindowCloseRequested();
+        }
+    }
+};
+
+}  // namespace nebula::window
+
+@implementation NebulaWindowDelegate
+- (instancetype)initWithOwner:(nebula::window::NebulaWindowImpl*)owner {
+    self = [super init];
+    if (self) {
+        owner_ = owner;
+    }
+    return self;
+}
+
+- (void)windowDidResize:(NSNotification*)notification {
+    (void)notification;
+    if (owner_) {
+        owner_->NotifyResized();
+    }
+}
+
+- (BOOL)windowShouldClose:(id)sender {
+    (void)sender;
+    if (owner_) {
+        owner_->NotifyCloseRequested();
+    }
+    return NO;
+}
+@end
+
+namespace nebula::window {
+
+NebulaWindow::NebulaWindow(WindowDelegate* delegate)
+    : impl_(std::make_unique<NebulaWindowImpl>()) {
+    impl_->delegate = delegate;
+}
+
+NebulaWindow::~NebulaWindow() = default;
+
+bool NebulaWindow::Create(const platform::AppStartup& startup) {
+    (void)startup;
+
+    @autoreleasepool {
+        [NSApplication sharedApplication];
+
+        const NSRect visible_frame = [[NSScreen mainScreen] visibleFrame];
+        const CGFloat width = std::min<CGFloat>(1400.0, NSWidth(visible_frame));
+        const CGFloat height = std::min<CGFloat>(900.0, NSHeight(visible_frame));
+        const CGFloat x = NSMinX(visible_frame) + (NSWidth(visible_frame) - width) / 2.0;
+        const CGFloat y = NSMinY(visible_frame) + (NSHeight(visible_frame) - height) / 2.0;
+
+        impl_->content_view = [[NebulaContentView alloc] initWithFrame:NSMakeRect(0, 0, width, height)];
+        impl_->window_delegate = [[NebulaWindowDelegate alloc] initWithOwner:impl_.get()];
+        impl_->window = [[NSWindow alloc] initWithContentRect:NSMakeRect(x, y, width, height)
+                                                    styleMask:NSWindowStyleMaskTitled |
+                                                              NSWindowStyleMaskClosable |
+                                                              NSWindowStyleMaskMiniaturizable |
+                                                              NSWindowStyleMaskResizable |
+                                                              NSWindowStyleMaskFullSizeContentView
+                                                      backing:NSBackingStoreBuffered
+                                                        defer:NO];
+        if (!impl_->window) {
+            return false;
+        }
+
+        [impl_->window setTitle:@"Nebula Browser"];
+        [impl_->window setTitleVisibility:NSWindowTitleHidden];
+        [impl_->window setTitlebarAppearsTransparent:YES];
+        [impl_->window setContentView:impl_->content_view];
+        [impl_->window setDelegate:impl_->window_delegate];
+        [impl_->window center];
+        [impl_->window makeKeyAndOrderFront:nil];
+        [NSApp activateIgnoringOtherApps:YES];
+
+        impl_->NotifyCreated();
+        return true;
+    }
+}
+
+platform::NativeWindow NebulaWindow::native_handle() const {
+    return (__bridge void*)impl_->content_view;
+}
+
+BrowserLayout NebulaWindow::CurrentLayout(bool show_chrome) const {
+    return impl_->CurrentLayout(show_chrome);
+}
+
+void NebulaWindow::ResizeChild(platform::NativeWindow child, const platform::Rect& rect) const {
+    NSView* view = (__bridge NSView*)child;
+    if (!view) {
+        return;
+    }
+
+    [view setFrame:ToNativeRect(rect)];
+}
+
+void NebulaWindow::Minimize() {
+    [impl_->window miniaturize:nil];
+}
+
+void NebulaWindow::ToggleMaximize() {
+    if (impl_->window && !impl_->fullscreen) {
+        [impl_->window zoom:nil];
+    }
+}
+
+void NebulaWindow::SetFullscreen(bool fullscreen) {
+    if (!impl_->window || impl_->fullscreen == fullscreen) {
+        return;
+    }
+
+    impl_->fullscreen = fullscreen;
+    [impl_->window toggleFullScreen:nil];
+}
+
+void NebulaWindow::Close() {
+    if (impl_->delegate) {
+        impl_->delegate->OnWindowCloseRequested();
+    }
+}
+
+void NebulaWindow::BeginDrag() {
+    if (!impl_->window) {
+        return;
+    }
+
+    NSEvent* event = [NSApp currentEvent];
+    if (event) {
+        [impl_->window performWindowDragWithEvent:event];
+    }
+}
+
+void NebulaWindow::SetTitle(const std::string& title) {
+    if (!impl_->window) {
+        return;
+    }
+
+    NSString* native_title = title.empty()
+        ? @"Nebula Browser"
+        : [[NSString alloc] initWithUTF8String:title.c_str()];
+    [impl_->window setTitle:native_title ?: @"Nebula Browser"];
+}
+
+void NebulaWindow::EnableFrameHitTest(platform::NativeWindow child) const {
+    (void)child;
+}
+
+}  // namespace nebula::window

src/platform/mac/paths_mac.cpp

@@ -0,0 +1,37 @@
+#include "platform/paths_platform.h"
+
+#include <mach-o/dyld.h>
+#include <pwd.h>
+#include <unistd.h>
+
+#include <cstdlib>
+
+namespace nebula::platform {
+
+std::filesystem::path ExecutableDirectory() {
+    char buffer[4096] = {};
+    uint32_t size = sizeof(buffer);
+    if (_NSGetExecutablePath(buffer, &size) != 0) {
+        return {};
+    }
+
+    return std::filesystem::path(buffer).parent_path();
+}
+
+std::filesystem::path DefaultUserDataRoot() {
+    if (const char* home = std::getenv("HOME")) {
+        return std::filesystem::path(home) / "Library" / "Application Support";
+    }
+
+    if (passwd* pw = getpwuid(getuid())) {
+        return std::filesystem::path(pw->pw_dir) / "Library" / "Application Support";
+    }
+
+    return ExecutableDirectory();
+}
+
+std::string PathToUtf8(const std::filesystem::path& path) {
+    return path.string();
+}
+
+}  // namespace nebula::platform

src/platform/mac/startup_mac.mm

@@ -0,0 +1,63 @@
+#include "platform/startup.h"
+
+#import <Cocoa/Cocoa.h>
+
+#include <fcntl.h>
+#include <filesystem>
+#include <system_error>
+#include <sys/file.h>
+#include <unistd.h>
+
+#include "include/cef_command_line.h"
+#include "ui/paths.h"
+
+namespace nebula::platform {
+namespace {
+
+int g_single_instance_lock = -1;
+
+}  // namespace
+
+void PrepareApp() {
+    @autoreleasepool {
+        [NSApplication sharedApplication];
+        [NSApp setActivationPolicy:NSApplicationActivationPolicyRegular];
+        [NSApp finishLaunching];
+    }
+}
+
+bool TryAcquireSingleInstance(const std::string& launch_target) {
+    NEBULA_UNUSED(launch_target);
+
+    const auto lock_path = nebula::ui::GetUserDataDirectory() / ".nebula_instance.lock";
+    std::error_code ec;
+    std::filesystem::create_directories(lock_path.parent_path(), ec);
+
+    g_single_instance_lock = open(lock_path.c_str(), O_CREAT | O_RDWR, 0644);
+    if (g_single_instance_lock < 0) {
+        return true;
+    }
+
+    return flock(g_single_instance_lock, LOCK_EX | LOCK_NB) == 0;
+}
+
+CefMainArgs MakeMainArgs(const AppStartup& startup) {
+    return CefMainArgs(startup.argc, startup.argv);
+}
+
+void InitCommandLine(CefRefPtr<CefCommandLine> command_line, const AppStartup& startup) {
+    command_line->InitFromArgv(startup.argc, startup.argv);
+}
+
+void ConfigureCefSettings(CefSettings& settings) {
+    const std::string user_data_dir = nebula::ui::GetUserDataDirectory().string();
+    const std::string cache_dir = nebula::ui::GetCacheDirectory().string();
+    if (!user_data_dir.empty()) {
+        CefString(&settings.root_cache_path).FromString(user_data_dir);
+    }
+    if (!cache_dir.empty()) {
+        CefString(&settings.cache_path).FromString(cache_dir);
+    }
+}
+
+}  // namespace nebula::platform

src/platform/paths_platform.h

@@ -0,0 +1,12 @@
+#pragma once
+
+#include <filesystem>
+#include <string>
+
+namespace nebula::platform {
+
+std::filesystem::path ExecutableDirectory();
+std::filesystem::path DefaultUserDataRoot();
+std::string PathToUtf8(const std::filesystem::path& path);
+
+}  // namespace nebula::platform

src/platform/startup.h

@@ -0,0 +1,16 @@
+#pragma once
+
+#include "include/cef_app.h"
+#include "platform/types.h"
+
+#include <string>
+
+namespace nebula::platform {
+
+void PrepareApp();
+bool TryAcquireSingleInstance(const std::string& launch_target = {});
+CefMainArgs MakeMainArgs(const AppStartup& startup);
+void InitCommandLine(CefRefPtr<CefCommandLine> command_line, const AppStartup& startup);
+void ConfigureCefSettings(CefSettings& settings);
+
+}  // namespace nebula::platform

src/platform/types.h

@@ -0,0 +1,35 @@
+#pragma once
+
+#ifndef NEBULA_UNUSED
+#define NEBULA_UNUSED(P) (void)(P)
+#endif
+
+namespace nebula::platform {
+
+struct Rect {
+    int x = 0;
+    int y = 0;
+    int width = 0;
+    int height = 0;
+};
+
+struct BrowserLayout {
+    Rect chrome;
+    Rect content;
+};
+
+using NativeWindow = void*;
+
+#if defined(_WIN32)
+struct AppStartup {
+    void* instance = nullptr;
+    int show_command = 0;
+};
+#else
+struct AppStartup {
+    int argc = 0;
+    char** argv = nullptr;
+};
+#endif
+
+}  // namespace nebula::platform

src/platform/win/browser_host_win.cpp

@@ -0,0 +1,139 @@
+#include "platform/browser_host.h"
+
+#include <windows.h>
+
+#include <algorithm>
+
+namespace nebula::platform {
+namespace {
+
+HWND AsHwnd(NativeWindow window) {
+    return static_cast<HWND>(window);
+}
+
+RECT ToRect(const Rect& rect) {
+    return {
+        rect.x,
+        rect.y,
+        rect.x + rect.width,
+        rect.y + rect.height,
+    };
+}
+
+}  // namespace
+
+CefWindowInfo MakeChildWindowInfo(NativeWindow parent, const Rect& rect) {
+    CefWindowInfo info;
+    info.SetAsChild(
+        AsHwnd(parent),
+        CefRect(rect.x, rect.y, rect.width, rect.height));
+    info.runtime_style = CEF_RUNTIME_STYLE_ALLOY;
+    return info;
+}
+
+CefWindowInfo MakeDevToolsPopup(NativeWindow parent, const char* title) {
+    CefWindowInfo info;
+    info.SetAsPopup(AsHwnd(parent), title);
+    info.runtime_style = CEF_RUNTIME_STYLE_ALLOY;
+    return info;
+}
+
+void ResizeBrowserWindow(NativeWindow browser_window, const Rect& rect) {
+    const HWND hwnd = AsHwnd(browser_window);
+    if (!hwnd) {
+        return;
+    }
+
+    SetWindowPos(
+        hwnd,
+        nullptr,
+        rect.x,
+        rect.y,
+        std::max(0, rect.width),
+        std::max(0, rect.height),
+        SWP_NOZORDER | SWP_NOACTIVATE | SWP_NOOWNERZORDER);
+}
+
+void SetBrowserVisible(NativeWindow browser_window, bool visible) {
+    const HWND hwnd = AsHwnd(browser_window);
+    if (!hwnd) {
+        return;
+    }
+
+    ShowWindow(hwnd, visible ? SW_SHOW : SW_HIDE);
+    if (visible) {
+        SetWindowPos(hwnd, HWND_TOP, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_NOACTIVATE);
+    }
+}
+
+void RaiseBrowserWindow(NativeWindow browser_window) {
+    const HWND hwnd = AsHwnd(browser_window);
+    if (!hwnd) {
+        return;
+    }
+
+    SetWindowPos(hwnd, HWND_TOP, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_NOACTIVATE);
+}
+
+void MoveCursorToBrowserPoint(NativeWindow browser_window, int x, int y) {
+    const HWND hwnd = AsHwnd(browser_window);
+    if (!hwnd) {
+        return;
+    }
+
+    POINT point = {x, y};
+    if (!ClientToScreen(hwnd, &point)) {
+        return;
+    }
+
+    SetCursorPos(point.x, point.y);
+}
+
+int ScaleForParentWindow(NativeWindow parent, int value) {
+    const HWND hwnd = AsHwnd(parent);
+    if (!hwnd) {
+        return value;
+    }
+
+    return MulDiv(value, static_cast<int>(GetDpiForWindow(hwnd)), 96);
+}
+
+std::pair<int, int> ParentClientSize(NativeWindow parent) {
+    RECT client = {};
+    const HWND hwnd = AsHwnd(parent);
+    if (hwnd) {
+        GetClientRect(hwnd, &client);
+    }
+
+    return {static_cast<int>(client.right), static_cast<int>(client.bottom)};
+}
+
+Rect MenuPopupRect(NativeWindow parent, const BrowserLayout& layout) {
+    const auto client_size = ParentClientSize(parent);
+    const int width = ScaleForParentWindow(parent, 260);
+    const int height = ScaleForParentWindow(parent, 258);
+    const int margin = ScaleForParentWindow(parent, 12);
+    const int overlap = ScaleForParentWindow(parent, 2);
+
+    const int x = std::max(0, client_size.first - width - margin);
+    const int y = std::max(0, layout.chrome.y + layout.chrome.height - overlap);
+    return {
+        x,
+        y,
+        std::min(client_size.first, x + width) - x,
+        std::min(client_size.second, y + height) - y,
+    };
+}
+
+std::string CacheBusterToken() {
+    return std::to_string(GetTickCount64());
+}
+
+void DestroyTopLevelWindow(NativeWindow window) {
+    const HWND hwnd = AsHwnd(window);
+    if (hwnd) {
+        DestroyWindow(hwnd);
+    }
+}
+
+}  // namespace nebula::platform

src/platform/win/default_browser_win.cpp

@@ -0,0 +1,176 @@
+#include "platform/default_browser.h"
+
+#include <windows.h>
+#include <shellapi.h>
+
+#include <filesystem>
+#include <string>
+#include <string_view>
+
+namespace nebula::platform {
+namespace {
+
+constexpr wchar_t kAppName[] = L"Nebula Browser";
+constexpr wchar_t kClientKeyName[] = L"NebulaBrowser";
+constexpr wchar_t kRegisteredApplicationsKey[] = L"Software\\RegisteredApplications";
+constexpr wchar_t kClientRootKey[] = L"Software\\Clients\\StartMenuInternet\\NebulaBrowser";
+constexpr wchar_t kFileAssociationsKey[] =
+    L"Software\\Clients\\StartMenuInternet\\NebulaBrowser\\Capabilities\\FileAssociations";
+constexpr wchar_t kUrlAssociationsKey[] =
+    L"Software\\Clients\\StartMenuInternet\\NebulaBrowser\\Capabilities\\URLAssociations";
+constexpr wchar_t kHttpUserChoiceKey[] =
+    L"Software\\Microsoft\\Windows\\Shell\\Associations\\UrlAssociations\\http\\UserChoice";
+constexpr wchar_t kHttpsUserChoiceKey[] =
+    L"Software\\Microsoft\\Windows\\Shell\\Associations\\UrlAssociations\\https\\UserChoice";
+constexpr std::wstring_view kWebFileExtensions[] = {
+    L".htm",
+    L".html",
+    L".shtml",
+    L".xht",
+    L".xhtml",
+    L".svg",
+    L".webp",
+};
+
+std::wstring CurrentExecutablePath() {
+    std::wstring path(MAX_PATH, L'\0');
+    DWORD length = 0;
+    while (true) {
+        length = GetModuleFileNameW(nullptr, path.data(), static_cast<DWORD>(path.size()));
+        if (length == 0) {
+            return {};
+        }
+        if (length < path.size() - 1) {
+            path.resize(length);
+            return path;
+        }
+        path.resize(path.size() * 2);
+    }
+}
+
+std::wstring Quote(std::wstring_view value) {
+    std::wstring quoted = L"\"";
+    quoted += value;
+    quoted += L"\"";
+    return quoted;
+}
+
+bool SetStringValue(HKEY root,
+                    const std::wstring& subkey,
+                    const wchar_t* value_name,
+                    const std::wstring& value) {
+    HKEY key = nullptr;
+    const LSTATUS status = RegCreateKeyExW(
+        root, subkey.c_str(), 0, nullptr, 0, KEY_SET_VALUE, nullptr, &key, nullptr);
+    if (status != ERROR_SUCCESS) {
+        return false;
+    }
+
+    const DWORD byte_size = static_cast<DWORD>((value.size() + 1) * sizeof(wchar_t));
+    const LSTATUS set_status = RegSetValueExW(
+        key,
+        value_name,
+        0,
+        REG_SZ,
+        reinterpret_cast<const BYTE*>(value.c_str()),
+        byte_size);
+    RegCloseKey(key);
+    return set_status == ERROR_SUCCESS;
+}
+
+std::wstring ReadStringValue(HKEY root, const wchar_t* subkey, const wchar_t* value_name) {
+    HKEY key = nullptr;
+    if (RegOpenKeyExW(root, subkey, 0, KEY_QUERY_VALUE, &key) != ERROR_SUCCESS) {
+        return {};
+    }
+
+    DWORD type = 0;
+    DWORD byte_size = 0;
+    if (RegQueryValueExW(key, value_name, nullptr, &type, nullptr, &byte_size) != ERROR_SUCCESS ||
+        type != REG_SZ || byte_size == 0) {
+        RegCloseKey(key);
+        return {};
+    }
+
+    std::wstring value(byte_size / sizeof(wchar_t), L'\0');
+    const LSTATUS status = RegQueryValueExW(
+        key, value_name, nullptr, nullptr, reinterpret_cast<BYTE*>(value.data()), &byte_size);
+    RegCloseKey(key);
+    if (status != ERROR_SUCCESS) {
+        return {};
+    }
+
+    while (!value.empty() && value.back() == L'\0') {
+        value.pop_back();
+    }
+    return value;
+}
+
+bool RegisterDefaultBrowserCapabilities() {
+    const std::wstring exe_path = CurrentExecutablePath();
+    if (exe_path.empty()) {
+        return false;
+    }
+
+    const std::wstring exe_name = std::filesystem::path(exe_path).filename().wstring();
+    const std::wstring command = Quote(exe_path) + L" --url=" + Quote(L"%1");
+    bool ok = true;
+
+    ok &= SetStringValue(HKEY_CURRENT_USER, kRegisteredApplicationsKey, kAppName,
+                         std::wstring(kClientRootKey) + L"\\Capabilities");
+    ok &= SetStringValue(HKEY_CURRENT_USER, kClientRootKey, nullptr, kAppName);
+    ok &= SetStringValue(HKEY_CURRENT_USER, std::wstring(kClientRootKey) + L"\\DefaultIcon",
+                         nullptr, exe_path + L",0");
+    ok &= SetStringValue(HKEY_CURRENT_USER, std::wstring(kClientRootKey) + L"\\shell\\open\\command",
+                         nullptr, Quote(exe_path));
+    ok &= SetStringValue(HKEY_CURRENT_USER, std::wstring(kClientRootKey) + L"\\Capabilities",
+                         L"ApplicationName", kAppName);
+    ok &= SetStringValue(HKEY_CURRENT_USER, std::wstring(kClientRootKey) + L"\\Capabilities",
+                         L"ApplicationDescription", L"Nebula Browser");
+    for (std::wstring_view extension : kWebFileExtensions) {
+        const std::wstring extension_name(extension);
+        ok &= SetStringValue(HKEY_CURRENT_USER, kFileAssociationsKey, extension_name.c_str(),
+                             kClientKeyName);
+    }
+    ok &= SetStringValue(HKEY_CURRENT_USER, kUrlAssociationsKey, L"http", kClientKeyName);
+    ok &= SetStringValue(HKEY_CURRENT_USER, kUrlAssociationsKey, L"https", kClientKeyName);
+    ok &= SetStringValue(HKEY_CURRENT_USER, L"Software\\Classes\\NebulaBrowser", nullptr,
+                         L"Nebula Browser HTML Document");
+    ok &= SetStringValue(HKEY_CURRENT_USER, L"Software\\Classes\\NebulaBrowser", L"URL Protocol",
+                         L"");
+    ok &= SetStringValue(HKEY_CURRENT_USER, L"Software\\Classes\\NebulaBrowser\\DefaultIcon",
+                         nullptr, exe_path + L",0");
+    ok &= SetStringValue(HKEY_CURRENT_USER, L"Software\\Classes\\NebulaBrowser\\shell\\open\\command",
+                         nullptr, command);
+    const std::wstring application_key = std::wstring(L"Software\\Classes\\Applications\\") + exe_name;
+    ok &= SetStringValue(HKEY_CURRENT_USER, application_key,
+                         L"ApplicationName", kAppName);
+    ok &= SetStringValue(HKEY_CURRENT_USER,
+                         application_key + L"\\shell\\open\\command",
+                         nullptr, command);
+
+    return ok;
+}
+
+void OpenDefaultAppsSettings() {
+    ShellExecuteW(nullptr, L"open", L"ms-settings:defaultapps", nullptr, nullptr, SW_SHOWNORMAL);
+}
+
+}  // namespace
+
+bool IsDefaultBrowser() {
+    return ReadStringValue(HKEY_CURRENT_USER, kHttpUserChoiceKey, L"ProgId") == kClientKeyName &&
+           ReadStringValue(HKEY_CURRENT_USER, kHttpsUserChoiceKey, L"ProgId") == kClientKeyName;
+}
+
+bool EnsureDefaultBrowserRegistration() {
+    return RegisterDefaultBrowserCapabilities();
+}
+
+bool RequestDefaultBrowser() {
+    const bool registered = RegisterDefaultBrowserCapabilities();
+    OpenDefaultAppsSettings();
+    return registered;
+}
+
+}  // namespace nebula::platform

src/platform/win/nebula_window_win.cpp

@@ -0,0 +1,673 @@
+#include "window/nebula_window.h"
+
+#include <dwmapi.h>
+#include <windows.h>
+#include <windowsx.h>
+
+#include <algorithm>
+#include <string_view>
+
+namespace nebula::window {
+namespace {
+
+constexpr wchar_t kWindowClassName[] = L"NebulaBrowserWindow";
+constexpr wchar_t kWindowTitle[] = L"Nebula Browser";
+constexpr wchar_t kChildFrameHitTestOldProcProp[] = L"NebulaChildFrameHitTestOldProc";
+constexpr wchar_t kChildFrameHitTestParentProp[] = L"NebulaChildFrameHitTestParent";
+constexpr ULONG_PTR kOpenTargetCopyDataId = 0x4E42554CUL;
+constexpr int kTitleRowHeightDip = 42;
+constexpr int kWindowControlWidthDip = 46;
+constexpr int kWindowControlCount = 3;
+constexpr COLORREF kNoWindowBorderColor = 0xFFFFFFFE;
+
+RECT GetWorkArea() {
+    RECT work_area = {};
+    SystemParametersInfoW(SPI_GETWORKAREA, 0, &work_area, 0);
+    return work_area;
+}
+
+RECT GetMonitorWorkArea(HWND hwnd) {
+    MONITORINFO monitor_info = {};
+    monitor_info.cbSize = sizeof(monitor_info);
+
+    const HMONITOR monitor = MonitorFromWindow(hwnd, MONITOR_DEFAULTTONEAREST);
+    if (monitor && GetMonitorInfoW(monitor, &monitor_info)) {
+        return monitor_info.rcWork;
+    }
+
+    return GetWorkArea();
+}
+
+RECT GetMonitorArea(HWND hwnd) {
+    MONITORINFO monitor_info = {};
+    monitor_info.cbSize = sizeof(monitor_info);
+
+    const HMONITOR monitor = MonitorFromWindow(hwnd, MONITOR_DEFAULTTONEAREST);
+    if (monitor && GetMonitorInfoW(monitor, &monitor_info)) {
+        return monitor_info.rcMonitor;
+    }
+
+    return GetWorkArea();
+}
+
+bool IsResizeHit(LRESULT hit) {
+    return hit == HTLEFT || hit == HTRIGHT || hit == HTTOP || hit == HTBOTTOM ||
+           hit == HTTOPLEFT || hit == HTTOPRIGHT || hit == HTBOTTOMLEFT || hit == HTBOTTOMRIGHT;
+}
+
+HCURSOR CursorForResizeHit(LRESULT hit) {
+    switch (hit) {
+        case HTLEFT:
+        case HTRIGHT:
+            return LoadCursor(nullptr, IDC_SIZEWE);
+        case HTTOP:
+        case HTBOTTOM:
+            return LoadCursor(nullptr, IDC_SIZENS);
+        case HTTOPLEFT:
+        case HTBOTTOMRIGHT:
+            return LoadCursor(nullptr, IDC_SIZENWSE);
+        case HTTOPRIGHT:
+        case HTBOTTOMLEFT:
+            return LoadCursor(nullptr, IDC_SIZENESW);
+        default:
+            return nullptr;
+    }
+}
+
+bool SetResizeCursor(LRESULT hit) {
+    HCURSOR cursor = CursorForResizeHit(hit);
+    if (!cursor) {
+        return false;
+    }
+
+    SetCursor(cursor);
+    return true;
+}
+
+void ApplyWindowFrameStyle(HWND hwnd) {
+    const BOOL dark_mode = TRUE;
+    const DWM_WINDOW_CORNER_PREFERENCE corner_preference = DWMWCP_ROUND;
+    DwmSetWindowAttribute(
+        hwnd,
+        DWMWA_USE_IMMERSIVE_DARK_MODE,
+        &dark_mode,
+        sizeof(dark_mode));
+
+    DwmSetWindowAttribute(
+        hwnd,
+        DWMWA_WINDOW_CORNER_PREFERENCE,
+        &corner_preference,
+        sizeof(corner_preference));
+
+    DwmSetWindowAttribute(
+        hwnd,
+        DWMWA_BORDER_COLOR,
+        &kNoWindowBorderColor,
+        sizeof(kNoWindowBorderColor));
+}
+
+platform::Rect ToPlatformRect(const RECT& rect) {
+    return {
+        rect.left,
+        rect.top,
+        std::max(0L, rect.right - rect.left),
+        std::max(0L, rect.bottom - rect.top),
+    };
+}
+
+RECT ToNativeRect(const platform::Rect& rect) {
+    return {
+        rect.x,
+        rect.y,
+        rect.x + rect.width,
+        rect.y + rect.height,
+    };
+}
+
+std::string WideToUtf8(std::wstring_view value) {
+    if (value.empty()) {
+        return {};
+    }
+
+    const int size = WideCharToMultiByte(
+        CP_UTF8,
+        0,
+        value.data(),
+        static_cast<int>(value.size()),
+        nullptr,
+        0,
+        nullptr,
+        nullptr);
+    if (size <= 0) {
+        return {};
+    }
+
+    std::string result(size, '\0');
+    WideCharToMultiByte(
+        CP_UTF8,
+        0,
+        value.data(),
+        static_cast<int>(value.size()),
+        result.data(),
+        size,
+        nullptr,
+        nullptr);
+    return result;
+}
+
+}  // namespace
+
+struct nebula::window::NebulaWindowImpl {
+    WindowDelegate* delegate = nullptr;
+    HINSTANCE instance = nullptr;
+    HWND hwnd = nullptr;
+    bool fullscreen = false;
+    LONG_PTR restore_style = 0;
+    LONG_PTR restore_ex_style = 0;
+    WINDOWPLACEMENT restore_placement = {sizeof(WINDOWPLACEMENT)};
+    UINT dpi = 96;
+    int resize_border_dip = 8;
+    int chrome_height_dip = 104;
+
+    int ScaleForDpi(int value) const {
+        return MulDiv(value, static_cast<int>(dpi), 96);
+    }
+
+    void UpdateDpi() {
+        if (hwnd) {
+            dpi = GetDpiForWindow(hwnd);
+        }
+    }
+
+    void NotifyResize() {
+        if (delegate) {
+            delegate->OnWindowResized(CurrentLayout(true));
+        }
+    }
+
+    BrowserLayout CurrentLayout(bool show_chrome) const {
+        RECT client = {};
+        if (hwnd) {
+            GetClientRect(hwnd, &client);
+        }
+
+        BrowserLayout layout;
+        layout.chrome = show_chrome
+            ? ToPlatformRect(RECT{
+                  0,
+                  0,
+                  client.right,
+                  std::min<LONG>(ScaleForDpi(chrome_height_dip), client.bottom)})
+            : platform::Rect{};
+        layout.content = ToPlatformRect(
+            RECT{0, layout.chrome.y + layout.chrome.height, client.right, client.bottom});
+        return layout;
+    }
+
+    void EnableFrameHitTestForWindow(HWND child) const;
+    LRESULT HitTest(LPARAM lparam) const;
+    LRESULT HitTestPoint(POINT point) const;
+    LRESULT WndProc(UINT message, WPARAM wparam, LPARAM lparam);
+    void RegisterClass(HINSTANCE instance_handle);
+
+    static LRESULT CALLBACK StaticWndProc(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam);
+    static LRESULT CALLBACK ChildFrameWndProc(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam);
+    static BOOL CALLBACK EnableFrameHitTestForDescendant(HWND hwnd, LPARAM lparam);
+};
+
+LRESULT CALLBACK nebula::window::NebulaWindowImpl::StaticWndProc(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam) {
+    NebulaWindowImpl* self = nullptr;
+
+    if (message == WM_NCCREATE) {
+        auto* create = reinterpret_cast<CREATESTRUCTW*>(lparam);
+        self = static_cast<NebulaWindowImpl*>(create->lpCreateParams);
+        SetWindowLongPtrW(hwnd, GWLP_USERDATA, reinterpret_cast<LONG_PTR>(self));
+        self->hwnd = hwnd;
+    } else {
+        self = reinterpret_cast<NebulaWindowImpl*>(GetWindowLongPtrW(hwnd, GWLP_USERDATA));
+    }
+
+    return self ? self->WndProc(message, wparam, lparam)
+                : DefWindowProcW(hwnd, message, wparam, lparam);
+}
+
+LRESULT CALLBACK nebula::window::NebulaWindowImpl::ChildFrameWndProc(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam) {
+    auto old_proc = reinterpret_cast<WNDPROC>(GetPropW(hwnd, kChildFrameHitTestOldProcProp));
+
+    if (message == WM_NCHITTEST) {
+        const auto parent = reinterpret_cast<HWND>(GetPropW(hwnd, kChildFrameHitTestParentProp));
+        auto* self = parent ? reinterpret_cast<NebulaWindowImpl*>(GetWindowLongPtrW(parent, GWLP_USERDATA)) : nullptr;
+        if (self) {
+            const LRESULT hit = self->HitTest(lparam);
+            if (IsResizeHit(hit)) {
+                return hit;
+            }
+        }
+    }
+
+    if (message == WM_SETCURSOR) {
+        const auto parent = reinterpret_cast<HWND>(GetPropW(hwnd, kChildFrameHitTestParentProp));
+        auto* self = parent ? reinterpret_cast<NebulaWindowImpl*>(GetWindowLongPtrW(parent, GWLP_USERDATA)) : nullptr;
+        POINT point = {};
+        if (self && GetCursorPos(&point) && SetResizeCursor(self->HitTestPoint(point))) {
+            return TRUE;
+        }
+    }
+
+    if (message == WM_MOUSEMOVE || message == WM_NCMOUSEMOVE) {
+        const auto parent = reinterpret_cast<HWND>(GetPropW(hwnd, kChildFrameHitTestParentProp));
+        auto* self = parent ? reinterpret_cast<NebulaWindowImpl*>(GetWindowLongPtrW(parent, GWLP_USERDATA)) : nullptr;
+        POINT point = {};
+        if (self && GetCursorPos(&point) && SetResizeCursor(self->HitTestPoint(point))) {
+            return 0;
+        }
+    }
+
+    if (message == WM_NCLBUTTONDOWN && IsResizeHit(static_cast<LRESULT>(wparam))) {
+        const auto parent = reinterpret_cast<HWND>(GetPropW(hwnd, kChildFrameHitTestParentProp));
+        if (parent) {
+            ReleaseCapture();
+            SendMessageW(parent, WM_NCLBUTTONDOWN, wparam, lparam);
+            return 0;
+        }
+    }
+
+    if (message == WM_NCDESTROY) {
+        RemovePropW(hwnd, kChildFrameHitTestParentProp);
+        RemovePropW(hwnd, kChildFrameHitTestOldProcProp);
+        if (old_proc) {
+            SetWindowLongPtrW(hwnd, GWLP_WNDPROC, reinterpret_cast<LONG_PTR>(old_proc));
+        }
+    }
+
+    return old_proc ? CallWindowProcW(old_proc, hwnd, message, wparam, lparam)
+                    : DefWindowProcW(hwnd, message, wparam, lparam);
+}
+
+BOOL CALLBACK nebula::window::NebulaWindowImpl::EnableFrameHitTestForDescendant(HWND hwnd, LPARAM lparam) {
+    const auto* self = reinterpret_cast<const NebulaWindowImpl*>(lparam);
+    if (self) {
+        self->EnableFrameHitTestForWindow(hwnd);
+    }
+    return TRUE;
+}
+
+void nebula::window::NebulaWindowImpl::EnableFrameHitTestForWindow(HWND child) const {
+    if (!child || GetPropW(child, kChildFrameHitTestOldProcProp)) {
+        return;
+    }
+
+    SetPropW(child, kChildFrameHitTestParentProp, hwnd);
+    const auto old_proc = reinterpret_cast<WNDPROC>(
+        SetWindowLongPtrW(child, GWLP_WNDPROC, reinterpret_cast<LONG_PTR>(&NebulaWindowImpl::ChildFrameWndProc)));
+    if (old_proc) {
+        SetPropW(child, kChildFrameHitTestOldProcProp, reinterpret_cast<HANDLE>(old_proc));
+    } else {
+        RemovePropW(child, kChildFrameHitTestParentProp);
+    }
+}
+
+LRESULT nebula::window::NebulaWindowImpl::WndProc(UINT message, WPARAM wparam, LPARAM lparam) {
+    switch (message) {
+        case WM_CREATE:
+            UpdateDpi();
+            if (delegate) {
+                delegate->OnWindowCreated();
+            }
+            return 0;
+
+        case WM_NCCALCSIZE:
+            if (wparam == TRUE) {
+                return 0;
+            }
+            break;
+
+        case WM_NCACTIVATE:
+            ApplyWindowFrameStyle(hwnd);
+            return TRUE;
+
+        case WM_ERASEBKGND:
+            return 1;
+
+        case WM_NCHITTEST:
+            return HitTest(lparam);
+
+        case WM_SETCURSOR: {
+            POINT point = {};
+            if (GetCursorPos(&point) && SetResizeCursor(HitTestPoint(point))) {
+                return TRUE;
+            }
+            break;
+        }
+
+        case WM_MOUSEMOVE:
+        case WM_NCMOUSEMOVE: {
+            POINT point = {};
+            if (GetCursorPos(&point) && SetResizeCursor(HitTestPoint(point))) {
+                return 0;
+            }
+            break;
+        }
+
+        case WM_SIZE:
+            NotifyResize();
+            return 0;
+
+        case WM_DPICHANGED: {
+            dpi = HIWORD(wparam);
+            const auto* suggested_rect = reinterpret_cast<RECT*>(lparam);
+            SetWindowPos(
+                hwnd,
+                nullptr,
+                suggested_rect->left,
+                suggested_rect->top,
+                suggested_rect->right - suggested_rect->left,
+                suggested_rect->bottom - suggested_rect->top,
+                SWP_NOZORDER | SWP_NOACTIVATE);
+            NotifyResize();
+            return 0;
+        }
+
+        case WM_GETMINMAXINFO: {
+            const RECT work_area = GetMonitorWorkArea(hwnd);
+            const RECT monitor_area = GetMonitorArea(hwnd);
+
+            auto* minmax = reinterpret_cast<MINMAXINFO*>(lparam);
+            minmax->ptMaxPosition.x = work_area.left - monitor_area.left;
+            minmax->ptMaxPosition.y = work_area.top - monitor_area.top;
+            minmax->ptMaxSize.x = work_area.right - work_area.left;
+            minmax->ptMaxSize.y = work_area.bottom - work_area.top;
+            return 0;
+        }
+
+        case WM_CLOSE:
+            if (delegate) {
+                delegate->OnWindowCloseRequested();
+                return 0;
+            }
+            break;
+
+        case WM_COPYDATA: {
+            const auto* copy_data = reinterpret_cast<const COPYDATASTRUCT*>(lparam);
+            if (copy_data && copy_data->dwData == kOpenTargetCopyDataId &&
+                copy_data->lpData && copy_data->cbData >= sizeof(wchar_t)) {
+                const auto* text = static_cast<const wchar_t*>(copy_data->lpData);
+                const size_t char_count = (copy_data->cbData / sizeof(wchar_t)) - 1;
+                if (delegate) {
+                    delegate->OnExternalOpenRequested(WideToUtf8(std::wstring_view(text, char_count)));
+                }
+                return TRUE;
+            }
+            break;
+        }
+
+        case WM_DESTROY:
+            hwnd = nullptr;
+            return 0;
+    }
+
+    return DefWindowProcW(hwnd, message, wparam, lparam);
+}
+
+void nebula::window::NebulaWindowImpl::RegisterClass(HINSTANCE instance_handle) {
+    WNDCLASSEXW window_class = {};
+    window_class.cbSize = sizeof(window_class);
+    window_class.lpfnWndProc = StaticWndProc;
+    window_class.hInstance = instance_handle;
+    window_class.hCursor = LoadCursor(nullptr, IDC_ARROW);
+    window_class.lpszClassName = kWindowClassName;
+
+    RegisterClassExW(&window_class);
+}
+
+LRESULT nebula::window::NebulaWindowImpl::HitTest(LPARAM lparam) const {
+    if (!hwnd) {
+        return HTNOWHERE;
+    }
+
+    POINT point = {GET_X_LPARAM(lparam), GET_Y_LPARAM(lparam)};
+    return HitTestPoint(point);
+}
+
+LRESULT nebula::window::NebulaWindowImpl::HitTestPoint(POINT point) const {
+    if (!hwnd) {
+        return HTNOWHERE;
+    }
+
+    RECT window = {};
+    GetWindowRect(hwnd, &window);
+
+    if (fullscreen || IsZoomed(hwnd)) {
+        return HTCLIENT;
+    }
+
+    const int resize_border = ScaleForDpi(resize_border_dip);
+    const bool left = point.x >= window.left && point.x < window.left + resize_border;
+    const bool right = point.x < window.right && point.x >= window.right - resize_border;
+    const bool top = point.y >= window.top && point.y < window.top + resize_border;
+    const bool bottom = point.y < window.bottom && point.y >= window.bottom - resize_border;
+
+    if (top && left) {
+        return HTTOPLEFT;
+    }
+    if (top && right) {
+        return HTTOPRIGHT;
+    }
+    if (bottom && left) {
+        return HTBOTTOMLEFT;
+    }
+    if (bottom && right) {
+        return HTBOTTOMRIGHT;
+    }
+    if (left) {
+        return HTLEFT;
+    }
+    if (right) {
+        return HTRIGHT;
+    }
+    if (top) {
+        return HTTOP;
+    }
+    if (bottom) {
+        return HTBOTTOM;
+    }
+
+    const int controls_width = ScaleForDpi(kWindowControlWidthDip * kWindowControlCount);
+    const int controls_height = ScaleForDpi(kTitleRowHeightDip);
+    const bool window_controls = point.x >= window.right - controls_width && point.x < window.right &&
+                                 point.y >= window.top && point.y < window.top + controls_height;
+    if (window_controls) {
+        return HTCLIENT;
+    }
+
+    return HTCLIENT;
+}
+
+std::wstring Utf8ToWide(const std::string& value) {
+    if (value.empty()) {
+        return {};
+    }
+
+    const int size = MultiByteToWideChar(
+        CP_UTF8, 0, value.data(), static_cast<int>(value.size()), nullptr, 0);
+    std::wstring result(size, L'\0');
+    MultiByteToWideChar(
+        CP_UTF8, 0, value.data(), static_cast<int>(value.size()), result.data(), size);
+    return result;
+}
+
+}  // namespace
+
+namespace nebula::window {
+
+NebulaWindow::NebulaWindow(WindowDelegate* delegate)
+    : impl_(std::make_unique<NebulaWindowImpl>()) {
+    impl_->delegate = delegate;
+}
+
+NebulaWindow::~NebulaWindow() = default;
+
+bool NebulaWindow::Create(const platform::AppStartup& startup) {
+    impl_->instance = static_cast<HINSTANCE>(startup.instance);
+    impl_->RegisterClass(impl_->instance);
+
+    const RECT work_area = GetWorkArea();
+    impl_->dpi = GetDpiForSystem();
+    const int width =
+        std::min<LONG>(impl_->ScaleForDpi(1400), work_area.right - work_area.left);
+    const int height =
+        std::min<LONG>(impl_->ScaleForDpi(900), work_area.bottom - work_area.top);
+    const int x = work_area.left + ((work_area.right - work_area.left) - width) / 2;
+    const int y = work_area.top + ((work_area.bottom - work_area.top) - height) / 2;
+
+    impl_->hwnd = CreateWindowExW(
+        0,
+        kWindowClassName,
+        kWindowTitle,
+        WS_POPUP | WS_THICKFRAME | WS_MINIMIZEBOX | WS_MAXIMIZEBOX | WS_CLIPCHILDREN,
+        x,
+        y,
+        width,
+        height,
+        nullptr,
+        nullptr,
+        impl_->instance,
+        impl_.get());
+
+    if (!impl_->hwnd) {
+        return false;
+    }
+
+    impl_->UpdateDpi();
+    ApplyWindowFrameStyle(impl_->hwnd);
+
+    const MARGINS margins = {0, 0, 0, 0};
+    DwmExtendFrameIntoClientArea(impl_->hwnd, &margins);
+
+    ShowWindow(impl_->hwnd, startup.show_command);
+    UpdateWindow(impl_->hwnd);
+    return true;
+}
+
+platform::NativeWindow NebulaWindow::native_handle() const {
+    return impl_->hwnd;
+}
+
+BrowserLayout NebulaWindow::CurrentLayout(bool show_chrome) const {
+    return impl_->CurrentLayout(show_chrome);
+}
+
+void NebulaWindow::ResizeChild(platform::NativeWindow child, const platform::Rect& rect) const {
+    const HWND hwnd = static_cast<HWND>(child);
+    if (!hwnd) {
+        return;
+    }
+
+    EnableFrameHitTest(child);
+    const RECT native_rect = ToNativeRect(rect);
+    SetWindowPos(
+        hwnd,
+        nullptr,
+        native_rect.left,
+        native_rect.top,
+        std::max(0L, native_rect.right - native_rect.left),
+        std::max(0L, native_rect.bottom - native_rect.top),
+        SWP_NOZORDER | SWP_NOACTIVATE | SWP_NOOWNERZORDER);
+}
+
+void NebulaWindow::Minimize() {
+    if (impl_->hwnd) {
+        ShowWindow(impl_->hwnd, SW_MINIMIZE);
+    }
+}
+
+void NebulaWindow::ToggleMaximize() {
+    if (!impl_->hwnd || impl_->fullscreen) {
+        return;
+    }
+
+    ShowWindow(impl_->hwnd, IsZoomed(impl_->hwnd) ? SW_RESTORE : SW_MAXIMIZE);
+}
+
+void NebulaWindow::SetFullscreen(bool fullscreen) {
+    if (!impl_->hwnd || impl_->fullscreen == fullscreen) {
+        return;
+    }
+
+    if (fullscreen) {
+        impl_->restore_style = GetWindowLongPtrW(impl_->hwnd, GWL_STYLE);
+        impl_->restore_ex_style = GetWindowLongPtrW(impl_->hwnd, GWL_EXSTYLE);
+        impl_->restore_placement.length = sizeof(impl_->restore_placement);
+        GetWindowPlacement(impl_->hwnd, &impl_->restore_placement);
+
+        impl_->fullscreen = true;
+        const RECT monitor = GetMonitorArea(impl_->hwnd);
+        SetWindowLongPtrW(
+            impl_->hwnd,
+            GWL_STYLE,
+            impl_->restore_style & ~(WS_THICKFRAME | WS_MAXIMIZEBOX | WS_MINIMIZEBOX));
+        SetWindowLongPtrW(impl_->hwnd, GWL_EXSTYLE, impl_->restore_ex_style);
+        SetWindowPos(
+            impl_->hwnd,
+            HWND_TOPMOST,
+            monitor.left,
+            monitor.top,
+            monitor.right - monitor.left,
+            monitor.bottom - monitor.top,
+            SWP_NOOWNERZORDER | SWP_FRAMECHANGED);
+    } else {
+        impl_->fullscreen = false;
+        SetWindowLongPtrW(impl_->hwnd, GWL_STYLE, impl_->restore_style);
+        SetWindowLongPtrW(impl_->hwnd, GWL_EXSTYLE, impl_->restore_ex_style);
+        SetWindowPlacement(impl_->hwnd, &impl_->restore_placement);
+        SetWindowPos(
+            impl_->hwnd,
+            HWND_NOTOPMOST,
+            0,
+            0,
+            0,
+            0,
+            SWP_NOMOVE | SWP_NOSIZE | SWP_NOOWNERZORDER | SWP_FRAMECHANGED);
+        ApplyWindowFrameStyle(impl_->hwnd);
+    }
+
+    impl_->NotifyResize();
+}
+
+void NebulaWindow::Close() {
+    if (impl_->hwnd) {
+        SendMessageW(impl_->hwnd, WM_CLOSE, 0, 0);
+    }
+}
+
+void NebulaWindow::BeginDrag() {
+    if (!impl_->hwnd) {
+        return;
+    }
+
+    ReleaseCapture();
+    SendMessageW(impl_->hwnd, WM_NCLBUTTONDOWN, HTCAPTION, 0);
+}
+
+void NebulaWindow::SetTitle(const std::string& title) {
+    if (!impl_->hwnd) {
+        return;
+    }
+
+    const std::wstring wide = title.empty() ? kWindowTitle : Utf8ToWide(title);
+    SetWindowTextW(impl_->hwnd, wide.c_str());
+}
+
+void NebulaWindow::EnableFrameHitTest(platform::NativeWindow child) const {
+    if (!impl_->hwnd || !child) {
+        return;
+    }
+
+    impl_->EnableFrameHitTestForWindow(static_cast<HWND>(child));
+    EnumChildWindows(
+        static_cast<HWND>(child),
+        &NebulaWindowImpl::EnableFrameHitTestForDescendant,
+        reinterpret_cast<LPARAM>(impl_.get()));
+}
+
+}  // namespace nebula::window

src/platform/win/paths_win.cpp

@@ -0,0 +1,41 @@
+#include "platform/paths_platform.h"
+
+#include <windows.h>
+
+namespace nebula::platform {
+
+std::filesystem::path ExecutableDirectory() {
+    wchar_t exe_path[MAX_PATH] = {};
+    const DWORD length = GetModuleFileNameW(nullptr, exe_path, MAX_PATH);
+    if (length == 0 || length == MAX_PATH) {
+        return {};
+    }
+
+    return std::filesystem::path(exe_path).parent_path();
+}
+
+std::filesystem::path DefaultUserDataRoot() {
+    wchar_t buffer[MAX_PATH] = {};
+    const DWORD length = GetEnvironmentVariableW(L"LOCALAPPDATA", buffer, MAX_PATH);
+    if (length > 0 && length < MAX_PATH) {
+        return std::filesystem::path(buffer);
+    }
+
+    return ExecutableDirectory();
+}
+
+std::string PathToUtf8(const std::filesystem::path& path) {
+    const std::wstring wide = path.wstring();
+    if (wide.empty()) {
+        return {};
+    }
+
+    const int size = WideCharToMultiByte(
+        CP_UTF8, 0, wide.data(), static_cast<int>(wide.size()), nullptr, 0, nullptr, nullptr);
+    std::string result(size, '\0');
+    WideCharToMultiByte(
+        CP_UTF8, 0, wide.data(), static_cast<int>(wide.size()), result.data(), size, nullptr, nullptr);
+    return result;
+}
+
+}  // namespace nebula::platform

src/platform/win/startup_win.cpp

@@ -0,0 +1,112 @@
+#include "platform/startup.h"
+
+#include <windows.h>
+
+#include <string>
+
+#include "include/cef_command_line.h"
+#include "ui/paths.h"
+
+namespace nebula::platform {
+namespace {
+
+constexpr wchar_t kMainInstanceMutexName[] = L"Local\\NebulaBrowserMainInstance";
+constexpr wchar_t kWindowClassName[] = L"NebulaBrowserWindow";
+constexpr ULONG_PTR kOpenTargetCopyDataId = 0x4E42554CUL;
+
+class ScopedHandle {
+public:
+    explicit ScopedHandle(HANDLE handle) : handle_(handle) {}
+    ~ScopedHandle() {
+        if (handle_) {
+            CloseHandle(handle_);
+        }
+    }
+
+    ScopedHandle(const ScopedHandle&) = delete;
+    ScopedHandle& operator=(const ScopedHandle&) = delete;
+
+    bool valid() const { return handle_ != nullptr; }
+
+private:
+    HANDLE handle_ = nullptr;
+};
+
+std::wstring Utf8ToWide(const std::string& value) {
+    if (value.empty()) {
+        return {};
+    }
+
+    const int size = MultiByteToWideChar(
+        CP_UTF8, 0, value.data(), static_cast<int>(value.size()), nullptr, 0);
+    if (size <= 0) {
+        return {};
+    }
+
+    std::wstring result(size, L'\0');
+    MultiByteToWideChar(
+        CP_UTF8, 0, value.data(), static_cast<int>(value.size()), result.data(), size);
+    return result;
+}
+
+void ForwardLaunchTargetToExistingWindow(const std::string& launch_target) {
+    if (launch_target.empty()) {
+        return;
+    }
+
+    HWND existing_window = FindWindowW(kWindowClassName, nullptr);
+    if (!existing_window) {
+        return;
+    }
+
+    const std::wstring target = Utf8ToWide(launch_target);
+    if (target.empty()) {
+        return;
+    }
+
+    COPYDATASTRUCT data = {};
+    data.dwData = kOpenTargetCopyDataId;
+    data.cbData = static_cast<DWORD>((target.size() + 1) * sizeof(wchar_t));
+    data.lpData = const_cast<wchar_t*>(target.c_str());
+    SendMessageW(existing_window, WM_COPYDATA, 0, reinterpret_cast<LPARAM>(&data));
+
+    ShowWindow(existing_window, SW_SHOWNORMAL);
+    SetForegroundWindow(existing_window);
+}
+
+}  // namespace
+
+void PrepareApp() {
+    SetProcessDpiAwarenessContext(DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2);
+}
+
+bool TryAcquireSingleInstance(const std::string& launch_target) {
+    static ScopedHandle mutex(CreateMutexW(nullptr, TRUE, kMainInstanceMutexName));
+    const bool already_running = mutex.valid() && GetLastError() == ERROR_ALREADY_EXISTS;
+    if (already_running) {
+        ForwardLaunchTargetToExistingWindow(launch_target);
+    }
+    return !already_running;
+}
+
+CefMainArgs MakeMainArgs(const AppStartup& startup) {
+    return CefMainArgs(static_cast<HINSTANCE>(startup.instance));
+}
+
+void InitCommandLine(CefRefPtr<CefCommandLine> command_line, const AppStartup& startup) {
+    NEBULA_UNUSED(startup);
+    command_line->InitFromString(::GetCommandLineW());
+}
+
+void ConfigureCefSettings(CefSettings& settings) {
+    const std::wstring user_data_dir = nebula::ui::GetUserDataDirectory().wstring();
+    const std::wstring cache_dir = nebula::ui::GetCacheDirectory().wstring();
+    if (!user_data_dir.empty()) {
+        CefString(&settings.root_cache_path).FromWString(user_data_dir);
+    }
+    if (!cache_dir.empty()) {
+        CefString(&settings.cache_path).FromWString(cache_dir);
+    }
+}
+
+}  // namespace nebula::platform

src/ui/paths.cpp

@@ -0,0 +1,281 @@
+#include "ui/paths.h"
+
+#include "platform/paths_platform.h"
+
+#include <algorithm>
+#include <cctype>
+#include <string_view>
+
+namespace nebula::ui {
+namespace {
+
+constexpr std::string_view kNebulaScheme = "nebula://";
+constexpr std::string_view kInternalFallbackPage = "404.html";
+
+struct InternalPage {
+    std::string_view slug;
+    std::string_view file_name;
+};
+
+constexpr InternalPage kInternalPages[] = {
+    {"home", "home.html"},
+    {"settings", "settings.html"},
+    {"downloads", "downloads.html"},
+    {"bigpicture", "bigpicture.html"},
+    {"big-picture", "bigpicture.html"},
+    {"gpu-diagnostics", "gpu-diagnostics.html"},
+    {"setup", "setup.html"},
+    {"404", "404.html"},
+    {"insecure", "insecure.html"},
+};
+
+std::string GetUrlWithoutDecoration(std::string url) {
+    const size_t split = url.find_first_of("?#");
+    if (split != std::string::npos) {
+        url.resize(split);
+    }
+    return url;
+}
+
+std::string GetUrlDecoration(const std::string& url) {
+    const size_t split = url.find_first_of("?#");
+    return split == std::string::npos ? std::string{} : url.substr(split);
+}
+
+std::string ToLowerAscii(std::string value) {
+    std::transform(value.begin(), value.end(), value.begin(), [](unsigned char ch) {
+        return static_cast<char>(std::tolower(ch));
+    });
+    return value;
+}
+
+std::string PageFileUrl(std::string_view page_name) {
+    const auto path = GetUiPagePath(std::string(page_name));
+    return path.empty() ? std::string{} : FilePathToUrl(path);
+}
+
+std::string PercentEncode(const std::string& value) {
+    constexpr char kHex[] = "0123456789ABCDEF";
+    std::string encoded;
+    encoded.reserve(value.size());
+    for (unsigned char ch : value) {
+        if (std::isalnum(ch) || ch == '-' || ch == '_' || ch == '.' || ch == '~') {
+            encoded += static_cast<char>(ch);
+        } else {
+            encoded += '%';
+            encoded += kHex[ch >> 4];
+            encoded += kHex[ch & 0x0F];
+        }
+    }
+    return encoded;
+}
+
+std::string InternalPageName(const std::string& url) {
+    std::string target = ToLowerAscii(GetUrlWithoutDecoration(url));
+    if (!target.starts_with(kNebulaScheme)) {
+        return {};
+    }
+
+    target.erase(0, kNebulaScheme.size());
+    while (!target.empty() && target.front() == '/') {
+        target.erase(target.begin());
+    }
+    while (!target.empty() && target.back() == '/') {
+        target.pop_back();
+    }
+    return target.empty() ? "home" : target;
+}
+
+std::string InternalUrlForSlug(std::string_view slug) {
+    return std::string(kNebulaScheme) + std::string(slug);
+}
+
+const InternalPage* FindInternalPageBySlug(std::string_view slug) {
+    for (const auto& page : kInternalPages) {
+        if (page.slug == slug) {
+            return &page;
+        }
+    }
+    return nullptr;
+}
+
+const InternalPage* FindInternalPageByFileUrl(const std::string& url) {
+    const std::string base_url = GetUrlWithoutDecoration(url);
+    for (const auto& page : kInternalPages) {
+        if (PageFileUrl(page.file_name) == base_url) {
+            return &page;
+        }
+    }
+    return nullptr;
+}
+
+}  // namespace
+
+std::filesystem::path GetExecutableDirectory() {
+    return nebula::platform::ExecutableDirectory();
+}
+
+std::filesystem::path GetUserDataDirectory() {
+    auto root = nebula::platform::DefaultUserDataRoot();
+    if (root.empty()) {
+        root = GetExecutableDirectory();
+    }
+    if (root.empty()) {
+        return {};
+    }
+
+    std::filesystem::path user_data = root / "Nebula" / "User Data";
+    std::error_code ec;
+    std::filesystem::create_directories(user_data, ec);
+    return user_data;
+}
+
+std::filesystem::path GetCacheDirectory() {
+    auto user_data = GetUserDataDirectory();
+    if (user_data.empty()) {
+        return {};
+    }
+
+    std::filesystem::path cache = user_data / "Cache";
+    std::error_code ec;
+    std::filesystem::create_directories(cache, ec);
+    return cache;
+}
+
+std::filesystem::path GetSessionStatePath() {
+    auto user_data = GetUserDataDirectory();
+    return user_data.empty() ? std::filesystem::path{} : user_data / "session_state.json";
+}
+
+std::filesystem::path GetFirstRunStatePath() {
+    auto user_data = GetUserDataDirectory();
+    return user_data.empty() ? std::filesystem::path{} : user_data / "first_run_state.json";
+}
+
+std::filesystem::path GetUiPagePath(const std::string& page_name) {
+    const auto exe_dir = GetExecutableDirectory();
+    if (exe_dir.empty()) {
+        return {};
+    }
+
+    return exe_dir / "ui" / "pages" / page_name;
+}
+
+std::string FilePathToUrl(std::filesystem::path path) {
+    std::string value = nebula::platform::PathToUtf8(path);
+    for (char& ch : value) {
+        if (ch == '\\') {
+            ch = '/';
+        }
+    }
+
+    std::string encoded;
+    encoded.reserve(value.size());
+    for (char ch : value) {
+        encoded += ch == ' ' ? "%20" : std::string(1, ch);
+    }
+    return encoded.starts_with('/') ? "file://" + encoded : "file:///" + encoded;
+}
+
+std::string GetChromeUrl() {
+    const auto path = GetUiPagePath("chrome.html");
+    const std::string fallback = PageFileUrl("home.html");
+    return path.empty() ? (fallback.empty() ? "https://www.google.com" : fallback) : FilePathToUrl(path);
+}
+
+std::string GetHomeUrl() {
+    return InternalUrlForSlug("home");
+}
+
+std::string GetSetupUrl() {
+    return InternalUrlForSlug("setup");
+}
+
+std::string GetSettingsUrl() {
+    return InternalUrlForSlug("settings");
+}
+
+std::string GetDownloadsUrl() {
+    return InternalUrlForSlug("downloads");
+}
+
+std::string GetBigPictureUrl() {
+    return InternalUrlForSlug("bigpicture");
+}
+
+std::string GetGpuDiagnosticsUrl() {
+    return InternalUrlForSlug("gpu-diagnostics");
+}
+
+std::string GetMenuPopupUrl() {
+    const auto path = GetUiPagePath("menu-popup.html");
+    const std::string fallback = PageFileUrl("home.html");
+    return path.empty() ? (fallback.empty() ? "https://www.google.com" : fallback) : FilePathToUrl(path);
+}
+
+std::string GetInsecureWarningUrl(const std::string& target_url) {
+    return InternalUrlForSlug("insecure") + "?target=" + PercentEncode(target_url);
+}
+
+std::string GetNotFoundUrl(const std::string& target_url) {
+    return InternalUrlForSlug("404") + "?url=" + PercentEncode(target_url);
+}
+
+std::string ResolveInternalUrl(const std::string& url) {
+    const std::string page_name = InternalPageName(url);
+    if (page_name.empty()) {
+        return url;
+    }
+
+    if (const auto* page = FindInternalPageBySlug(page_name)) {
+        const std::string file_url = PageFileUrl(page->file_name);
+        return file_url.empty() ? url : file_url + GetUrlDecoration(url);
+    }
+
+    const std::string fallback_url = PageFileUrl(kInternalFallbackPage);
+    return fallback_url.empty() ? url : fallback_url + "?url=" + PercentEncode(url);
+}
+
+std::string ToInternalUrl(const std::string& url) {
+    const std::string page_name = InternalPageName(url);
+    if (!page_name.empty()) {
+        if (const auto* page = FindInternalPageBySlug(page_name)) {
+            return InternalUrlForSlug(page->slug) + GetUrlDecoration(url);
+        }
+        return url;
+    }
+
+    if (const auto* page = FindInternalPageByFileUrl(url)) {
+        return InternalUrlForSlug(page->slug) + GetUrlDecoration(url);
+    }
+
+    return url;
+}
+
+bool IsInternalHomeUrl(const std::string& url) {
+    return GetUrlWithoutDecoration(ToInternalUrl(url)) == GetHomeUrl();
+}
+
+bool IsNebulaInternalUrl(const std::string& url) {
+    return ToLowerAscii(url).starts_with(kNebulaScheme);
+}
+
+bool IsHttpUrl(const std::string& url) {
+    return ToLowerAscii(url).starts_with("http://");
+}
+
+bool IsChromiumNewTabUrl(const std::string& url) {
+    const std::string target = ToLowerAscii(GetUrlWithoutDecoration(url));
+    return target == "about:blank" ||
+           target == "chrome://newtab" ||
+           target == "chrome://newtab/" ||
+           target == "chrome://new-tab-page" ||
+           target == "chrome://new-tab-page/" ||
+           target == "chrome-search://local-ntp/local-ntp.html";
+}
+
+bool IsEmptyOrChromiumNewTabUrl(const std::string& url) {
+    return url.empty() || IsChromiumNewTabUrl(url);
+}
+
+}  // namespace nebula::ui

src/ui/paths.h

@@ -0,0 +1,34 @@
+#pragma once
+
+#include <filesystem>
+#include <string>
+
+namespace nebula::ui {
+
+std::filesystem::path GetExecutableDirectory();
+std::filesystem::path GetUserDataDirectory();
+std::filesystem::path GetCacheDirectory();
+std::filesystem::path GetSessionStatePath();
+std::filesystem::path GetFirstRunStatePath();
+std::filesystem::path GetUiPagePath(const std::string& page_name);
+std::string FilePathToUrl(std::filesystem::path path);
+std::string GetChromeUrl();
+std::string GetHomeUrl();
+std::string GetSetupUrl();
+std::string GetSettingsUrl();
+std::string GetDownloadsUrl();
+std::string GetBigPictureUrl();
+std::string GetGpuDiagnosticsUrl();
+std::string GetMenuPopupUrl();
+std::string GetInsecureWarningUrl(const std::string& target_url);
+std::string GetNotFoundUrl(const std::string& target_url);
+std::string ResolveInternalUrl(const std::string& url);
+std::string ToInternalUrl(const std::string& url);
+
+bool IsInternalHomeUrl(const std::string& url);
+bool IsNebulaInternalUrl(const std::string& url);
+bool IsHttpUrl(const std::string& url);
+bool IsChromiumNewTabUrl(const std::string& url);
+bool IsEmptyOrChromiumNewTabUrl(const std::string& url);
+
+}  // namespace nebula::ui

src/window/nebula_window.h

@@ -0,0 +1,45 @@
+#pragma once
+
+#include <memory>
+#include <string>
+
+#include "platform/types.h"
+
+namespace nebula::window {
+
+struct NebulaWindowImpl;
+
+using BrowserLayout = nebula::platform::BrowserLayout;
+
+class WindowDelegate {
+public:
+    virtual ~WindowDelegate() = default;
+    virtual void OnWindowCreated() = 0;
+    virtual void OnWindowResized(const BrowserLayout& layout) = 0;
+    virtual void OnWindowCloseRequested() = 0;
+    virtual void OnExternalOpenRequested(const std::string& target) = 0;
+};
+
+class NebulaWindow {
+public:
+    explicit NebulaWindow(WindowDelegate* delegate);
+    ~NebulaWindow();
+
+    bool Create(const nebula::platform::AppStartup& startup);
+    nebula::platform::NativeWindow native_handle() const;
+    BrowserLayout CurrentLayout(bool show_chrome = true) const;
+
+    void ResizeChild(nebula::platform::NativeWindow child, const nebula::platform::Rect& rect) const;
+    void Minimize();
+    void ToggleMaximize();
+    void SetFullscreen(bool fullscreen);
+    void Close();
+    void BeginDrag();
+    void SetTitle(const std::string& title);
+    void EnableFrameHitTest(nebula::platform::NativeWindow child) const;
+
+private:
+    std::unique_ptr<NebulaWindowImpl> impl_;
+};
+
+}  // namespace nebula::window

ui/css/bigpicture.css

@@ -132,6 +132,83 @@ body.mouse-active {
   left: -100px;
 }
 
+.browser-stage-frame {
+  position: fixed;
+  left: var(--browser-stage-x, 20%);
+  top: var(--browser-stage-y, 10%);
+  width: var(--browser-stage-width, 60%);
+  height: var(--browser-stage-height, 80%);
+  z-index: 3;
+  pointer-events: none;
+  border-radius: var(--bp-radius-xl);
+  box-shadow:
+    0 0 0 2px rgba(255, 255, 255, 0.08),
+    0 0 0 6px rgba(123, 46, 255, 0.18),
+    0 24px 80px rgba(0, 0, 0, 0.55),
+    0 0 80px var(--bp-primary-glow);
+  opacity: 1;
+  transition: opacity var(--bp-transition-normal), box-shadow var(--bp-transition-normal);
+}
+
+.browser-stage-frame.hidden {
+  opacity: 0;
+}
+
+.virtual-cursor {
+  position: fixed;
+  left: 0;
+  top: 0;
+  z-index: 250;
+  width: 34px;
+  height: 34px;
+  pointer-events: none;
+  transform: translate3d(var(--virtual-cursor-x, 50vw), var(--virtual-cursor-y, 50vh), 0);
+  transition: opacity var(--bp-transition-fast);
+  filter: drop-shadow(0 8px 18px rgba(0, 0, 0, 0.55));
+}
+
+.virtual-cursor.hidden {
+  opacity: 0;
+}
+
+.virtual-cursor::before {
+  content: '';
+  position: absolute;
+  left: 4px;
+  top: 3px;
+  width: 18px;
+  height: 24px;
+  background: linear-gradient(135deg, var(--bp-text), var(--bp-accent));
+  clip-path: polygon(0 0, 0 100%, 38% 76%, 60% 100%, 84% 86%, 62% 62%, 100% 62%);
+  box-shadow: 0 0 0 2px rgba(0, 0, 0, 0.45), 0 0 20px var(--bp-accent-glow);
+}
+
+.virtual-cursor-dot {
+  position: absolute;
+  left: 10px;
+  top: 10px;
+  width: 8px;
+  height: 8px;
+  border-radius: 999px;
+  background: var(--bp-primary);
+  opacity: 0;
+  transform: scale(1);
+}
+
+.virtual-cursor.clicking .virtual-cursor-dot {
+  animation: virtual-cursor-click 180ms ease-out;
+}
+
+.virtual-cursor.right-clicking .virtual-cursor-dot {
+  background: var(--bp-warning);
+  animation: virtual-cursor-click 180ms ease-out;
+}
+
+@keyframes virtual-cursor-click {
+  0% { opacity: 0.95; transform: scale(0.8); }
+  100% { opacity: 0; transform: scale(4.4); }
+}
+
 @keyframes glow-pulse {
   0% { transform: scale(1); opacity: 0.3; }
   100% { transform: scale(1.2); opacity: 0.5; }
@@ -220,6 +297,15 @@ body.mouse-active {
   color: var(--bp-text-muted);
 }
 
+.status-icon.controller-status.connected {
+  color: var(--bp-success);
+  box-shadow: 0 0 20px rgba(74, 222, 128, 0.25);
+}
+
+.status-icon.controller-status.disconnected {
+  color: var(--bp-text-dim);
+}
+
 .status-icon .material-symbols-outlined {
   font-size: 20px;
 }
@@ -338,8 +424,9 @@ body.mouse-active {
   inset: 0;
   width: 100%;
   height: 100%;
-  background: var(--bp-bg);
+  background: transparent;
   z-index: 2;
+  pointer-events: none;
 }
 
 .webview-container.hidden {
@@ -353,6 +440,155 @@ body.mouse-active {
   border: none;
 }
 
+.native-browser-panel {
+  position: absolute;
+  top: var(--bp-spacing-md);
+  right: var(--bp-spacing-md);
+  bottom: var(--bp-spacing-md);
+  width: clamp(168px, 18vw, 260px);
+  overflow-y: auto;
+  padding: var(--bp-spacing-sm);
+  background: linear-gradient(180deg, rgba(10,10,15,0.88) 0%, rgba(20,20,31,0.82) 100%);
+  border: 1px solid rgba(255, 255, 255, 0.08);
+  border-radius: var(--bp-radius-lg);
+  box-shadow: 0 18px 60px rgba(0, 0, 0, 0.35);
+  backdrop-filter: blur(20px);
+  pointer-events: auto;
+}
+
+.native-page-card {
+  display: grid;
+  grid-template-columns: auto minmax(0, 1fr);
+  align-items: center;
+  gap: var(--bp-spacing-sm);
+  padding: var(--bp-spacing-sm);
+  margin-bottom: var(--bp-spacing-md);
+  background: rgba(20, 20, 31, 0.78);
+  border: 2px solid var(--bp-border);
+  border-radius: var(--bp-radius-lg);
+  cursor: pointer;
+}
+
+.native-page-card:focus,
+.native-page-card.focused {
+  outline: none;
+  border-color: var(--bp-accent);
+  box-shadow: var(--bp-focus-ring-accent);
+}
+
+.native-page-card .material-symbols-outlined {
+  font-size: 28px;
+  color: var(--bp-accent);
+}
+
+.native-page-card h2 {
+  font-size: 0.95rem;
+  color: var(--bp-text);
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+
+.native-page-card p {
+  font-size: 0.72rem;
+  color: var(--bp-text-muted);
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+
+.native-page-card .controller-note {
+  grid-column: 1 / -1;
+  margin-top: 4px;
+  color: var(--bp-accent);
+  white-space: normal;
+}
+
+.browser-actions {
+  display: grid;
+  grid-template-columns: 1fr;
+  gap: var(--bp-spacing-xs);
+  margin-bottom: var(--bp-spacing-lg);
+}
+
+.action-button:disabled {
+  opacity: 0.45;
+  cursor: not-allowed;
+}
+
+.tab-list {
+  display: flex;
+  flex-direction: column;
+  gap: var(--bp-spacing-xs);
+}
+
+.bp-tab {
+  display: grid;
+  grid-template-columns: auto minmax(0, 1fr) auto;
+  grid-template-areas:
+    "dot title close"
+    "dot url close";
+  align-items: center;
+  column-gap: var(--bp-spacing-sm);
+  padding: var(--bp-spacing-sm);
+  background: var(--bp-surface);
+  border: 2px solid var(--bp-border);
+  border-radius: var(--bp-radius-md);
+  color: var(--bp-text);
+  cursor: pointer;
+  text-align: left;
+}
+
+.bp-tab.active {
+  border-color: var(--bp-primary);
+  background: var(--bp-surface-active);
+}
+
+.bp-tab:focus,
+.bp-tab.focused {
+  outline: none;
+  border-color: var(--bp-accent);
+  box-shadow: var(--bp-focus-ring-accent);
+}
+
+.tab-dot {
+  grid-area: dot;
+  color: var(--bp-accent);
+}
+
+.tab-text {
+  grid-area: title;
+  font-weight: 600;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+
+.tab-url {
+  grid-area: url;
+  color: var(--bp-text-muted);
+  font-size: 0.8rem;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+
+.tab-close-inline {
+  grid-area: close;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  width: 28px;
+  height: 28px;
+  border-radius: var(--bp-radius-sm);
+  color: var(--bp-text-muted);
+}
+
+.tab-close-inline:hover {
+  background: var(--bp-danger);
+  color: var(--bp-text);
+}
+
 /* Content area */
 .bp-content {
   flex: 1;

ui/css/chrome.css

@@ -0,0 +1,384 @@
+:root {
+  --bg: #080a0f;
+  --surface: #0e1119;
+  --surface-raised: #141824;
+  --surface-hover: rgba(255, 255, 255, 0.06);
+  --text: #e8e8f0;
+  --muted: #7a7e90;
+  --accent: #7b2eff;
+  --primary: #7b2eff;
+  --accent-2: #00c6ff;
+  --outline: #1f2533;
+  --outline-soft: rgba(255, 255, 255, 0.06);
+  --danger: #e0445c;
+  --url-bar-bg: #1c2030;
+  --url-bar-text: #e0e0e0;
+  --url-bar-border: #3e4652;
+  --tab-bg: #161925;
+  --tab-text: #a4a7b3;
+  --tab-active: #1c2030;
+  --tab-active-text: #e0e0e0;
+  --tab-border: #2b3040;
+  --chrome-hover: color-mix(in srgb, var(--text) 10%, transparent);
+  color-scheme: dark;
+}
+
+@font-face {
+  font-family: "InterVariable";
+  src: url("../assets/fonts/InterVariable.ttf") format("truetype");
+  font-weight: 100 900;
+  font-display: swap;
+}
+
+* {
+  box-sizing: border-box;
+}
+
+html,
+body {
+  width: 100%;
+  height: 100%;
+  margin: 0;
+  overflow: hidden;
+}
+
+body {
+  background: var(--bg);
+  color: var(--text);
+  font-family: "InterVariable", "Segoe UI", system-ui, sans-serif;
+  user-select: none;
+}
+
+button,
+input {
+  font: inherit;
+}
+
+button {
+  border: 0;
+  color: var(--text);
+  cursor: pointer;
+}
+
+button:disabled {
+  cursor: default;
+  opacity: 0.3;
+}
+
+/* ── Chrome shell ───────────────────────────────────────────── */
+
+.nebula-chrome {
+  display: grid;
+  grid-template-rows: 42px 52px 1fr;
+  height: 100%;
+  border-bottom: 1px solid var(--outline);
+  overflow: visible;
+}
+
+/* ── Title row ──────────────────────────────────────────────── */
+
+.title-row,
+.toolbar {
+  display: flex;
+  align-items: center;
+}
+
+.title-row {
+  gap: 10px;
+  padding: 0 0 0 12px;
+  background: var(--bg);
+}
+
+.platform-macos .title-row {
+  padding: 0 12px 0 78px;
+}
+
+/* ── Tabs ───────────────────────────────────────────────────── */
+
+.tabs {
+  display: flex;
+  align-items: flex-end;
+  gap: 3px;
+  min-width: 0;
+  flex: 1;
+  height: 100%;
+}
+
+.tab {
+  display: flex;
+  align-items: center;
+  gap: 7px;
+  min-width: 0;
+  width: min(260px, 38vw);
+  height: 33px;
+  padding: 0 14px;
+  border-radius: 10px 10px 0 0;
+  border: 1px solid transparent;
+  border-bottom: none;
+  background: transparent;
+  color: var(--tab-text);
+  cursor: pointer;
+  font-size: 0.82rem;
+  transition: background 120ms, color 120ms;
+}
+
+.tab:hover:not(.active) {
+  background: var(--tab-bg);
+  color: var(--tab-active-text);
+}
+
+.tab.active {
+  background: var(--tab-active);
+  border-color: var(--tab-border);
+  color: var(--tab-active-text);
+}
+
+.tab-title {
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+  flex: 1;
+  min-width: 0;
+}
+
+.tab-favicon,
+.tab-loading {
+  width: 16px;
+  height: 16px;
+  flex: 0 0 auto;
+  border-radius: 3px;
+}
+
+.tab-favicon {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  background: var(--primary);
+  opacity: 0.85;
+  border-radius: 999px;
+  overflow: hidden;
+}
+
+.tab-favicon.has-favicon {
+  background: transparent;
+  border-radius: 3px;
+  opacity: 1;
+}
+
+.tab-favicon.empty {
+  width: 13px;
+  height: 13px;
+}
+
+.tab-favicon img {
+  display: block;
+  width: 16px;
+  height: 16px;
+  object-fit: contain;
+}
+
+.tab-loading {
+  width: 13px;
+  height: 13px;
+  border: 2px solid color-mix(in srgb, var(--accent) 20%, transparent);
+  border-top-color: var(--accent);
+  border-radius: 999px;
+  animation: spin 0.8s linear infinite;
+}
+
+.tab-close {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 20px;
+  height: 20px;
+  padding: 0;
+  border-radius: 6px;
+  background: transparent;
+  color: var(--tab-text);
+  opacity: 0;
+  transition: background 120ms, color 120ms, opacity 120ms;
+}
+
+.tab:hover .tab-close,
+.tab.active .tab-close,
+.tab-close:focus-visible {
+  opacity: 1;
+}
+
+.tab-close:hover {
+  background: var(--chrome-hover);
+  color: var(--tab-active-text);
+}
+
+.tab-add {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 28px;
+  height: 28px;
+  margin-bottom: 2px;
+  border-radius: 8px;
+  border: 1px solid transparent;
+  background: transparent;
+  color: var(--tab-text);
+  transition: background 120ms, color 120ms, border-color 120ms;
+}
+
+.tab-add:hover {
+  background: var(--chrome-hover);
+  border-color: var(--tab-border);
+  color: var(--tab-active-text);
+}
+
+/* ── Window controls ────────────────────────────────────────── */
+
+.window-controls {
+  display: flex;
+  align-self: stretch;
+  margin: 0;
+  overflow: hidden;
+  border-top-right-radius: 10px;
+}
+
+.window-controls button {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 46px;
+  background: transparent;
+  color: var(--tab-text);
+  transition: background 100ms, color 100ms;
+}
+
+.window-controls button:hover {
+  background: var(--chrome-hover);
+  color: var(--tab-active-text);
+}
+
+.window-controls .close:hover {
+  background: var(--danger);
+  color: white;
+}
+
+.platform-macos .window-controls {
+  display: none;
+}
+
+/* ── Toolbar ────────────────────────────────────────────────── */
+
+.toolbar {
+  gap: 4px;
+  padding: 0 12px;
+  background: var(--tab-active);
+  border-top: 1px solid var(--tab-border);
+  overflow: visible;
+}
+
+/* ── Lucide icon sizing ─────────────────────────────────────── */
+
+/* Lucide replaces <i data-lucide> with <svg>; enforce consistent size */
+.icon-button svg,
+.tab-close svg,
+.tab-add svg,
+.window-controls svg {
+  width: 16px;
+  height: 16px;
+  display: block;
+  stroke-width: 1.75;
+  pointer-events: none;
+}
+
+/* ── Icon buttons ───────────────────────────────────────────── */
+
+.icon-button {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 34px;
+  height: 34px;
+  padding: 0;
+  border-radius: 9px;
+  background: transparent;
+  border: 1px solid transparent;
+  color: var(--tab-text);
+  flex-shrink: 0;
+  transition: background 120ms, color 120ms, border-color 120ms;
+}
+
+.icon-button:hover:not(:disabled) {
+  background: var(--chrome-hover);
+  border-color: var(--tab-border);
+  color: var(--tab-active-text);
+}
+
+/* ── Address bar ────────────────────────────────────────────── */
+
+.address-shell {
+  position: relative;
+  display: flex;
+  align-items: center;
+  min-width: 160px;
+  height: 36px;
+  flex: 1;
+  margin: 0 4px;
+  overflow: hidden;
+  border: 1px solid var(--url-bar-border);
+  border-radius: 10px;
+  background: var(--url-bar-bg);
+  transition: border-color 140ms, box-shadow 140ms;
+}
+
+.address-shell:focus-within {
+  border-color: color-mix(in srgb, var(--primary) 70%, var(--url-bar-border));
+  box-shadow: 0 0 0 3px color-mix(in srgb, var(--primary) 18%, transparent);
+}
+
+.address-shell input {
+  width: 100%;
+  height: 100%;
+  border: 0;
+  outline: 0;
+  padding: 0 16px;
+  background: transparent;
+  color: var(--url-bar-text);
+  font-size: 0.84rem;
+}
+
+.address-shell input::placeholder {
+  color: color-mix(in srgb, var(--url-bar-text) 55%, transparent);
+}
+
+.progress-bar {
+  position: absolute;
+  bottom: 0;
+  left: 0;
+  height: 2px;
+  width: 0%;
+  pointer-events: none;
+  background: var(--accent);
+  border-radius: 0 2px 2px 0;
+  opacity: 0.7;
+  transition: width 120ms ease, opacity 160ms ease;
+}
+
+/* ── Utilities ──────────────────────────────────────────────── */
+
+.sr-only {
+  position: absolute;
+  width: 1px;
+  height: 1px;
+  padding: 0;
+  margin: -1px;
+  overflow: hidden;
+  clip: rect(0, 0, 0, 0);
+  white-space: nowrap;
+  border: 0;
+}
+
+@keyframes spin {
+  to {
+    transform: rotate(360deg);
+  }
+}
+

ui/css/menu-popup.css

@@ -1,34 +1,40 @@
 :root {
-  --bg: #0b0d10;
+  --surface-raised: #141824;
-  --primary: #7b2eff;
+  --surface-hover: rgba(255, 255, 255, 0.06);
-  --accent: #00c6ff;
+  --text: #e8e8f0;
-  --text: #e0e0e0;
+  --muted: #7a7e90;
-  --url-bar-bg: #1c2030;
+  --outline: #1f2533;
-  --url-bar-border: #3e4652;
+  color-scheme: dark;
-  --shadow-1: 0 12px 30px rgba(0, 0, 0, 0.35);
+}
-  --blur: 12px;
+
+@font-face {
+  font-family: "InterVariable";
+  src: url("../assets/fonts/InterVariable.ttf") format("truetype");
+  font-weight: 100 900;
+  font-display: swap;
 }
 
 * { box-sizing: border-box; }
 
 body {
   margin: 0;
-  background: transparent;
+  background: var(--surface-raised);
   color: var(--text);
-  font-family: system-ui, -apple-system, Segoe UI, Roboto, sans-serif;
+  font-family: "InterVariable", "Segoe UI", system-ui, sans-serif;
+  overflow: hidden;
+  user-select: none;
 }
 
 #menu-popup {
-  background: color-mix(in srgb, var(--url-bar-bg) 92%, var(--text) 8%);
+  width: 100%;
-  border: 1px solid color-mix(in srgb, var(--primary) 25%, color-mix(in srgb, var(--accent) 18%, transparent));
+  height: 100%;
-  border-radius: 14px;
+  background: var(--surface-raised);
-  padding: 8px;
+  border: 1px solid var(--outline);
+  border-radius: 12px;
+  padding: 6px;
   display: flex;
   flex-direction: column;
-  min-width: 220px;
+  box-shadow: 0 12px 32px rgba(0, 0, 0, 0.45);
-  box-shadow: var(--shadow-1);
-  -webkit-backdrop-filter: blur(var(--blur));
-  backdrop-filter: blur(var(--blur));
 }
 
 #menu-popup button {
@@ -37,13 +43,15 @@ body {
   color: var(--text);
   text-align: left;
   padding: 8px 10px;
-  border-radius: 10px;
+  border-radius: 8px;
   cursor: pointer;
-  transition: background 120ms ease, filter 120ms ease;
+  font: inherit;
+  font-size: 0.84rem;
+  transition: background 120ms ease;
 }
 
 #menu-popup button:hover {
-  background: color-mix(in srgb, var(--text) 8%, transparent);
+  background: var(--surface-hover);
 }
 
 .zoom-controls {
@@ -63,4 +71,6 @@ body {
 #zoom-percent {
   min-width: 54px;
   text-align: center;
+  color: var(--muted);
+  font-size: 0.82rem;
 }

ui/js/chrome.js

@@ -0,0 +1,301 @@
+const SEARCH_URL = 'https://www.google.com/search?q=';
+
+const DEFAULT_THEME = {
+  colors: {
+    bg: '#080a0f',
+    darkBlue: '#0e1119',
+    darkPurple: '#141824',
+    primary: '#7b2eff',
+    accent: '#00c6ff',
+    text: '#e8e8f0',
+    urlBarBg: '#1c2030',
+    urlBarText: '#e0e0e0',
+    urlBarBorder: '#3e4652',
+    tabBg: '#161925',
+    tabText: '#a4a7b3',
+    tabActive: '#1c2030',
+    tabActiveText: '#e0e0e0',
+    tabBorder: '#2b3040'
+  }
+};
+
+const state = {
+  id: 1,
+  url: '',
+  title: 'New Tab',
+  isLoading: false,
+  progress: 0,
+  canGoBack: false,
+  canGoForward: false,
+  favicon: '',
+  platform: detectHostPlatform(),
+  tabs: []
+};
+
+function detectHostPlatform() {
+  const platform = `${navigator.userAgentData?.platform || ''} ${navigator.platform || ''} ${navigator.userAgent || ''}`.toLowerCase();
+  if (platform.includes('mac')) return 'macos';
+  if (platform.includes('win')) return 'windows';
+  if (platform.includes('linux')) return 'linux';
+  return 'unknown';
+}
+
+function applyPlatform(platform) {
+  const normalized = ['macos', 'windows', 'linux'].includes(platform) ? platform : 'unknown';
+  document.body.classList.remove('platform-macos', 'platform-windows', 'platform-linux', 'platform-unknown');
+  document.body.classList.add(`platform-${normalized}`);
+}
+
+function hexToRgb(hex) {
+  if (!hex || typeof hex !== 'string') return null;
+  let normalized = hex.trim().replace(/^#/, '');
+  if (normalized.length === 3) {
+    normalized = normalized.split('').map(char => char + char).join('');
+  }
+  if (!/^[a-fA-F\d]{6}$/.test(normalized)) return null;
+
+  const value = parseInt(normalized, 16);
+  return {
+    r: (value >> 16) & 255,
+    g: (value >> 8) & 255,
+    b: value & 255
+  };
+}
+
+function isDarkColor(hex) {
+  const rgb = hexToRgb(hex);
+  if (!rgb) return true;
+  const luminance = (0.2126 * rgb.r + 0.7152 * rgb.g + 0.0722 * rgb.b) / 255;
+  return luminance < 0.5;
+}
+
+function setCssVar(name, value, fallback) {
+  document.documentElement.style.setProperty(name, value || fallback);
+}
+
+function normalizeTheme(theme) {
+  const colors = theme?.colors || {};
+  return {
+    ...DEFAULT_THEME,
+    ...(theme || {}),
+    colors: {
+      ...DEFAULT_THEME.colors,
+      ...colors
+    }
+  };
+}
+
+function applyTheme(theme) {
+  const normalized = normalizeTheme(theme);
+  const colors = normalized.colors;
+
+  setCssVar('--bg', colors.bg, DEFAULT_THEME.colors.bg);
+  setCssVar('--surface', colors.darkBlue, DEFAULT_THEME.colors.darkBlue);
+  setCssVar('--surface-raised', colors.darkPurple, DEFAULT_THEME.colors.darkPurple);
+  setCssVar('--text', colors.text, DEFAULT_THEME.colors.text);
+  setCssVar('--muted', colors.tabText, DEFAULT_THEME.colors.tabText);
+  setCssVar('--primary', colors.primary, DEFAULT_THEME.colors.primary);
+  setCssVar('--accent', colors.accent, DEFAULT_THEME.colors.accent);
+  setCssVar('--accent-2', colors.accent, DEFAULT_THEME.colors.accent);
+  setCssVar('--outline', colors.tabBorder, DEFAULT_THEME.colors.tabBorder);
+  setCssVar('--url-bar-bg', colors.urlBarBg, colors.darkBlue);
+  setCssVar('--url-bar-text', colors.urlBarText, colors.text);
+  setCssVar('--url-bar-border', colors.urlBarBorder, colors.primary);
+  setCssVar('--tab-bg', colors.tabBg, colors.darkBlue);
+  setCssVar('--tab-text', colors.tabText, colors.text);
+  setCssVar('--tab-active', colors.tabActive, colors.darkPurple);
+  setCssVar('--tab-active-text', colors.tabActiveText, colors.text);
+  setCssVar('--tab-border', colors.tabBorder, colors.darkBlue);
+
+  document.documentElement.style.colorScheme = isDarkColor(colors.bg) ? 'dark' : 'light';
+}
+
+function applySavedTheme() {
+  try {
+    const savedTheme = localStorage.getItem('currentTheme');
+    if (savedTheme) applyTheme(JSON.parse(savedTheme));
+  } catch (error) {
+    console.warn('[Chrome] Failed to apply saved theme:', error);
+  }
+}
+
+function toNavigationUrl(input) {
+  const value = (input || '').trim();
+  if (!value) return null;
+  if (/^(https?:|file:|data:|blob:|chrome:|nebula:\/\/)/i.test(value)) return value;
+  if (value.includes('.') && !/\s/.test(value)) return `https://${value}`;
+  return `${SEARCH_URL}${encodeURIComponent(value)}`;
+}
+
+function postCommand(command, payload = '') {
+  if (window.nebulaNative && typeof window.nebulaNative.postMessage === 'function') {
+    window.nebulaNative.postMessage(command, String(payload));
+  }
+}
+
+function renderFavicon(favicon, tab) {
+  const url = (tab.favicon || '').trim();
+  favicon.className = 'tab-favicon';
+  favicon.textContent = '';
+
+  if (!url) {
+    favicon.classList.add('empty');
+    return;
+  }
+
+  const image = document.createElement('img');
+  image.alt = '';
+  image.decoding = 'async';
+  image.draggable = false;
+  image.addEventListener('load', () => {
+    favicon.classList.add('has-favicon');
+  });
+  image.addEventListener('error', () => {
+    image.remove();
+    favicon.classList.remove('has-favicon');
+    favicon.classList.add('empty');
+  });
+
+  favicon.append(image);
+  image.src = url;
+}
+
+function renderTabs() {
+  const tabsElement = document.querySelector('.tabs');
+  const addButton = tabsElement.querySelector('.tab-add');
+  const tabs = state.tabs.length
+    ? state.tabs
+    : [{ id: state.id, title: state.title, isLoading: state.isLoading, favicon: state.favicon }];
+
+  tabsElement.querySelectorAll('.tab').forEach(tab => tab.remove());
+
+  tabs.forEach(tab => {
+    const button = document.createElement('div');
+    const isActive = tab.id === state.id;
+    button.className = `tab${isActive ? ' active' : ''}`;
+    button.setAttribute('role', 'tab');
+    button.setAttribute('aria-selected', String(isActive));
+    button.tabIndex = 0;
+    button.dataset.tabId = String(tab.id);
+
+    const favicon = document.createElement('span');
+    renderFavicon(favicon, tab);
+
+    const title = document.createElement('span');
+    title.className = 'tab-title';
+    title.textContent = tab.title || 'New Tab';
+
+    const loading = document.createElement('span');
+    loading.className = 'tab-loading';
+    loading.hidden = !tab.isLoading;
+
+    const close = document.createElement('button');
+    close.className = 'tab-close';
+    close.type = 'button';
+    close.title = 'Close tab';
+    close.setAttribute('aria-label', `Close ${tab.title || 'New Tab'}`);
+    close.dataset.tabId = String(tab.id);
+    close.innerHTML = '<i data-lucide="x"></i>';
+
+    button.append(favicon, title, loading, close);
+    tabsElement.insertBefore(button, addButton);
+  });
+
+  if (window.lucide) lucide.createIcons({ nodes: [tabsElement] });
+}
+
+function applyState(nextState) {
+  Object.assign(state, nextState || {});
+  applyPlatform(state.platform);
+
+  const title = state.title || 'New Tab';
+  const url = state.url || '';
+  const addressInput = document.getElementById('address-input');
+  const backButton = document.getElementById('back-button');
+  const forwardButton = document.getElementById('forward-button');
+  const reloadButton = document.getElementById('reload-button');
+  const progressBar = document.getElementById('progress-bar');
+
+  document.title = `${title} - Nebula`;
+  renderTabs();
+  backButton.disabled = !state.canGoBack;
+  forwardButton.disabled = !state.canGoForward;
+  const reloadIcon = state.isLoading ? 'x' : 'rotate-cw';
+  reloadButton.dataset.command = state.isLoading ? 'stop' : 'reload';
+  reloadButton.innerHTML = `<i data-lucide="${reloadIcon}"></i>`;
+  if (window.lucide) lucide.createIcons({ nodes: [reloadButton] });
+
+  if (document.activeElement !== addressInput) {
+    addressInput.value = url;
+  }
+
+  progressBar.style.width = `${Math.max(0, Math.min(1, state.progress || 0)) * 100}%`;
+  progressBar.style.opacity = state.isLoading ? '1' : '0';
+
+}
+
+function wireCommands() {
+  document.querySelector('.tabs').addEventListener('click', event => {
+    const close = event.target.closest('.tab-close[data-tab-id]');
+    if (close) {
+      postCommand('close-tab', close.dataset.tabId);
+      return;
+    }
+
+    const tab = event.target.closest('.tab[data-tab-id]');
+    if (tab && !tab.classList.contains('active')) {
+      postCommand('activate-tab', tab.dataset.tabId);
+    }
+  });
+
+  document.querySelector('.tabs').addEventListener('auxclick', event => {
+    if (event.button !== 1) return;
+
+    const tab = event.target.closest('.tab[data-tab-id]');
+    if (tab) {
+      postCommand('close-tab', tab.dataset.tabId);
+    }
+  });
+
+  document.querySelectorAll('[data-command]').forEach(button => {
+    button.addEventListener('click', () => {
+      postCommand(button.dataset.command);
+    });
+  });
+
+  document.querySelectorAll('[data-drag-region]').forEach(region => {
+    region.addEventListener('pointerdown', event => {
+      const interactive = event.target.closest('button, input, .tab, .address-shell');
+      if (event.button === 0 && !interactive) {
+        postCommand('drag');
+      }
+    });
+  });
+
+  document.getElementById('address-form').addEventListener('submit', event => {
+    event.preventDefault();
+    const input = document.getElementById('address-input');
+    const target = toNavigationUrl(input.value);
+    if (target) {
+      postCommand('navigate', target);
+      input.blur();
+    }
+  });
+}
+
+window.NebulaChrome = { applyState, applyTheme, postCommand, toNavigationUrl };
+
+window.addEventListener('storage', event => {
+  if (event.key !== 'currentTheme' || !event.newValue) return;
+  try {
+    applyTheme(JSON.parse(event.newValue));
+  } catch (error) {
+    console.warn('[Chrome] Failed to apply updated theme:', error);
+  }
+});
+
+document.addEventListener('DOMContentLoaded', () => {
+  applySavedTheme();
+  wireCommands();
+  applyState(state);
+});

ui/js/customization.js

@@ -4,7 +4,7 @@
  */
 
 class BrowserCustomizer {
-  constructor() {
+  constructor(options = {}) {
     this.defaultTheme = {
       name: 'Default',
       colors: {
@@ -286,6 +286,10 @@ class BrowserCustomizer {
       }
     };
 
+    if (options.skipInit) {
+      return;
+    }
+
     this.currentTheme = this.loadTheme();
     this.activeThemeName = this.loadActiveThemeName();
     this.init();
@@ -584,9 +588,13 @@ class BrowserCustomizer {
     // This will be called to apply theme to home.html and other pages
     this.saveTheme();
 
-    // Send theme update to host (for settings webview)
+    const themePayload = JSON.stringify(this.currentTheme);
-    if (window.electronAPI && typeof window.electronAPI.sendToHost === 'function') {
+
-      window.electronAPI.sendToHost('theme-update', this.currentTheme);
+    // Send theme update to host so the separate chrome browser can update live.
+    if (window.nebulaNative && typeof window.nebulaNative.postMessage === 'function') {
+      window.nebulaNative.postMessage('theme-update', themePayload);
+    } else if (window.electronAPI && typeof window.electronAPI.sendToHost === 'function') {
+      window.electronAPI.sendToHost('theme-update', themePayload);
     }
     // Fallback: send via postMessage (for iframe embedding)
     try {

ui/js/home.js

@@ -88,7 +88,7 @@ function applySelectedSearchEngine(engine) {
 function normalizeNavigationUrl(input) {
   const value = (input || '').trim();
   if (!value) return null;
-  if (/^(https?:|file:|data:|blob:)/i.test(value)) return value;
+  if (/^(https?:|file:|data:|blob:|nebula:\/\/)/i.test(value)) return value;
   if (value.includes('.') && !/\s/.test(value)) return `https://${value}`;
   return `${searchEngines[selectedSearchEngine]}${encodeURIComponent(value)}`;
 }

ui/js/menu-popup.js

@@ -17,33 +17,36 @@ function applyTheme(theme) {
   setCssVar('--url-bar-border', colors.urlBarBorder, '#3e4652');
 }
 
-async function refreshZoom() {
+function sendMenuCommand(cmd) {
-  if (!window.electronAPI?.invoke || !zoomPercentEl) return;
+  if (window.nebulaNative?.postMessage) {
-  try {
+    window.nebulaNative.postMessage(cmd);
-    const z = await window.electronAPI.invoke('get-zoom-factor');
+  }
-    zoomPercentEl.textContent = `${Math.round(z * 100)}%`;
-  } catch {}
 }
 
-window.electronAPI?.on?.('menu-popup-init', (payload) => {
+function formatZoomPercent(zoomLevel) {
-  applyTheme(payload?.theme);
+  const level = Number.isFinite(zoomLevel) ? zoomLevel : 0;
-  refreshZoom();
+  return `${Math.round(Math.pow(1.2, level) * 100)}%`;
-});
+}
+
+function setZoomLevel(zoomLevel) {
+  if (zoomPercentEl) {
+    zoomPercentEl.textContent = formatZoomPercent(zoomLevel);
+  }
+}
+
+window.NebulaMenuPopup = { applyTheme, setZoomLevel };
 
 window.addEventListener('click', (e) => {
   const btn = e.target.closest('button[data-cmd]');
   if (!btn) return;
   const cmd = btn.getAttribute('data-cmd');
-  window.electronAPI?.send?.('menu-popup-command', { cmd });
+  sendMenuCommand(cmd);
-  if (cmd === 'zoom-in' || cmd === 'zoom-out') {
-    setTimeout(refreshZoom, 50);
-  }
 });
 
 window.addEventListener('keydown', (e) => {
   if (e.key === 'Escape') {
-    window.electronAPI?.send?.('menu-popup-command', { cmd: 'close' });
+    sendMenuCommand('close-menu-popup');
   }
 });
 
-refreshZoom();
+setZoomLevel(0);

ui/js/settings.js

@@ -12,6 +12,109 @@ const HOME_SEARCH_Y_KEY = 'nebula-home-search-y'; // number (vh)
 const HOME_BOOKMARKS_Y_KEY = 'nebula-home-bookmarks-y'; // number (vh)
 const HOME_GLANCE_CORNER_KEY = 'nebula-home-glance-corner'; // 'br'|'bl'|'tr'|'tl'
 const DISPLAY_SCALE_KEY = 'nebula-display-scale'; // number (50-300)
+const defaultBrowserRequests = new Map();
+let defaultBrowserRequestId = 0;
+
+function hasNebulaNativeBridge() {
+  return !!(window.nebulaNative && typeof window.nebulaNative.postMessage === 'function');
+}
+
+window.addEventListener('nebula-default-browser-result', (event) => {
+  const detail = event.detail || {};
+  const pending = defaultBrowserRequests.get(detail.requestId);
+  if (!pending) return;
+
+  defaultBrowserRequests.delete(detail.requestId);
+  pending.resolve(detail);
+});
+
+function sendDefaultBrowserRequest(command) {
+  return new Promise((resolve, reject) => {
+    if (!hasNebulaNativeBridge()) {
+      reject(new Error('Native browser integration is unavailable.'));
+      return;
+    }
+
+    const requestId = `settings-default-browser-${Date.now()}-${++defaultBrowserRequestId}`;
+    const timeout = setTimeout(() => {
+      defaultBrowserRequests.delete(requestId);
+      reject(new Error('Timed out waiting for default browser status.'));
+    }, 10000);
+
+    defaultBrowserRequests.set(requestId, {
+      resolve: (value) => {
+        clearTimeout(timeout);
+        resolve(value);
+      }
+    });
+
+    try {
+      window.nebulaNative.postMessage(command, requestId);
+    } catch (error) {
+      defaultBrowserRequests.delete(requestId);
+      clearTimeout(timeout);
+      reject(error);
+    }
+  });
+}
+
+async function refreshDefaultBrowserStatus() {
+  const btn = document.getElementById('set-default-browser-btn');
+  const status = document.getElementById('default-browser-status');
+  if (!btn || !status) return;
+
+  if (!hasNebulaNativeBridge()) {
+    btn.disabled = true;
+    status.textContent = 'Default browser setup is only available in the native app.';
+    return;
+  }
+
+  try {
+    const result = await sendDefaultBrowserRequest('check-default-browser');
+    btn.disabled = !!result.isDefault;
+    btn.textContent = result.isDefault ? 'Already Default' : 'Make Default Browser';
+    status.textContent = result.isDefault
+      ? 'Nebula is your default browser.'
+      : 'Nebula is not your default browser.';
+  } catch (error) {
+    console.error('Default browser status error:', error);
+    status.textContent = 'Unable to check default browser status.';
+  }
+}
+
+function attachDefaultBrowserHandler() {
+  const btn = document.getElementById('set-default-browser-btn');
+  const status = document.getElementById('default-browser-status');
+  if (!btn || !status) return;
+
+  btn.addEventListener('click', async () => {
+    btn.disabled = true;
+    btn.textContent = 'Opening Settings...';
+    status.textContent = 'Opening Windows default apps settings...';
+
+    try {
+      const result = await sendDefaultBrowserRequest('set-default-browser');
+      if (result.isDefault) {
+        btn.textContent = 'Already Default';
+        status.textContent = 'Nebula is your default browser.';
+        return;
+      }
+
+      btn.disabled = false;
+      btn.textContent = 'Check Again';
+      status.textContent = result.success
+        ? 'Choose Nebula in Windows default apps settings, then check again.'
+        : (result.error || 'Unable to open default browser settings.');
+    } catch (error) {
+      console.error('Default browser setup error:', error);
+      btn.disabled = false;
+      btn.textContent = 'Try Again';
+      status.textContent = 'Unable to open default browser settings.';
+    }
+  });
+
+  refreshDefaultBrowserStatus();
+}
 
 function showStatus(message) {
   if (statusText && statusDiv) {
@@ -65,7 +168,7 @@ function attachClearHandler(btn) {
     } finally {
       const currentTheme = window.browserCustomizer ? window.browserCustomizer.currentTheme : null;
       if (currentTheme && window.electronAPI && typeof window.electronAPI.sendToHost === 'function') {
-        window.electronAPI.sendToHost('theme-update', currentTheme);
+        window.electronAPI.sendToHost('theme-update', JSON.stringify(currentTheme));
       }
     }
   };
@@ -74,6 +177,8 @@ function attachClearHandler(btn) {
 // Try attaching immediately, and again on DOMContentLoaded
 attachClearHandler(clearBtn);
 window.addEventListener('DOMContentLoaded', () => {
+  attachDefaultBrowserHandler();
+
   if (!clearBtn) {
     clearBtn = document.getElementById('clear-data-btn');
     attachClearHandler(clearBtn);
@@ -773,7 +878,9 @@ window.addEventListener('DOMContentLoaded', () => {
       try {
         e.preventDefault();
         const url = gh.getAttribute('href');
-        if (window.electronAPI && typeof window.electronAPI.sendToHost === 'function') {
+        if (window.nebulaNative && typeof window.nebulaNative.postMessage === 'function') {
+          window.nebulaNative.postMessage('new-tab', url);
+        } else if (window.electronAPI && typeof window.electronAPI.sendToHost === 'function') {
           window.electronAPI.sendToHost('navigate', url, { newTab: true });
         } else if (window.parent && window.parent !== window) {
           window.parent.postMessage({ type: 'navigate', url, newTab: true }, '*');
@@ -792,7 +899,9 @@ window.addEventListener('DOMContentLoaded', () => {
       try {
         e.preventDefault();
         const url = help.getAttribute('href');
-        if (window.electronAPI && typeof window.electronAPI.sendToHost === 'function') {
+        if (window.nebulaNative && typeof window.nebulaNative.postMessage === 'function') {
+          window.nebulaNative.postMessage('new-tab', url);
+        } else if (window.electronAPI && typeof window.electronAPI.sendToHost === 'function') {
           window.electronAPI.sendToHost('navigate', url, { newTab: true });
         } else if (window.parent && window.parent !== window) {
           window.parent.postMessage({ type: 'navigate', url, newTab: true }, '*');

ui/js/setup.js

@@ -12,17 +12,130 @@ const setupState = {
   themes: []
 };
 
-const nativeApi = window.api || {
+function hasNebulaNativeBridge() {
-  async getAllThemes() {
+  return !!(window.nebulaNative && typeof window.nebulaNative.postMessage === 'function');
-    return {
+}
-      default: {
+
-        default: {
+const defaultBrowserRequests = new Map();
-          name: 'Default',
+let defaultBrowserRequestId = 0;
-          description: 'Classic Nebula theme',
+
-          colors: { bg: '#121418', primary: '#7B2EFF', accent: '#00C6FF', text: '#E0E0E0' }
+window.addEventListener('nebula-default-browser-result', (event) => {
-        }
+  const detail = event.detail || {};
+  const pending = defaultBrowserRequests.get(detail.requestId);
+  if (!pending) return;
+
+  defaultBrowserRequests.delete(detail.requestId);
+  pending.resolve(detail);
+});
+
+function sendDefaultBrowserRequest(command) {
+  return new Promise((resolve, reject) => {
+    if (!hasNebulaNativeBridge()) {
+      reject(new Error('Native browser integration is unavailable.'));
+      return;
+    }
+
+    const requestId = `default-browser-${Date.now()}-${++defaultBrowserRequestId}`;
+    const timeout = setTimeout(() => {
+      defaultBrowserRequests.delete(requestId);
+      reject(new Error('Timed out waiting for default browser status.'));
+    }, 10000);
+
+    defaultBrowserRequests.set(requestId, {
+      resolve: (value) => {
+        clearTimeout(timeout);
+        resolve(value);
+      },
+      reject: (error) => {
+        clearTimeout(timeout);
+        reject(error);
       }
-    };
+    });
+
+    try {
+      window.nebulaNative.postMessage(command, requestId);
+    } catch (error) {
+      defaultBrowserRequests.delete(requestId);
+      clearTimeout(timeout);
+      reject(error);
+    }
+  });
+}
+
+function createNebulaNativeApi() {
+  return {
+    async getAllThemes() {
+      return { default: getPresetThemes() };
+    },
+    async isDefaultBrowser() {
+      const result = await sendDefaultBrowserRequest('check-default-browser');
+      return !!result.isDefault;
+    },
+    async setAsDefaultBrowser() {
+      return sendDefaultBrowserRequest('set-default-browser');
+    },
+    async applyTheme(themeId) {
+      const theme = getThemeById(themeId);
+      if (theme) {
+        localStorage.setItem('currentTheme', JSON.stringify(normalizeTheme(theme)));
+      }
+      localStorage.setItem('activeThemeName', themeId);
+    },
+    async completeFirstRun(data) {
+      localStorage.setItem('nebula-first-run-complete', JSON.stringify(data));
+      window.nebulaNative.postMessage('complete-first-run', JSON.stringify(data));
+    }
+  };
+}
+
+function getPresetThemes() {
+  if (typeof BrowserCustomizer === 'function') {
+    const customizer = new BrowserCustomizer({ skipInit: true });
+    return customizer.predefinedThemes || { default: customizer.defaultTheme };
+  }
+
+  return {
+    default: {
+      name: 'Default',
+      colors: {
+        bg: '#121418',
+        darkBlue: '#0B1C2B',
+        darkPurple: '#1B1035',
+        primary: '#7B2EFF',
+        accent: '#00C6FF',
+        text: '#E0E0E0',
+        urlBarBg: '#1C2030',
+        urlBarText: '#E0E0E0',
+        urlBarBorder: '#3E4652',
+        tabBg: '#161925',
+        tabText: '#A4A7B3',
+        tabActive: '#1C2030',
+        tabActiveText: '#E0E0E0',
+        tabBorder: '#2B3040'
+      },
+      layout: 'centered',
+      showLogo: true,
+      customTitle: 'Nebula Browser',
+      gradient: 'linear-gradient(145deg, #121418 0%, #1B1035 100%)'
+    }
+  };
+}
+
+function normalizeTheme(theme) {
+  const fallback = getPresetThemes().default;
+  return {
+    ...fallback,
+    ...(theme || {}),
+    colors: {
+      ...fallback.colors,
+      ...((theme && theme.colors) || {})
+    }
+  };
+}
+
+const fallbackApi = {
+  async getAllThemes() {
+    return { default: getPresetThemes() };
   },
   async isDefaultBrowser() {
     return false;
@@ -31,13 +144,22 @@ const nativeApi = window.api || {
     return { success: false, error: 'Default browser setup is handled by the native CEF app.' };
   },
   async applyTheme(themeId) {
+    const theme = getThemeById(themeId);
+    if (theme) {
+      localStorage.setItem('currentTheme', JSON.stringify(normalizeTheme(theme)));
+    }
     localStorage.setItem('activeThemeName', themeId);
   },
   async completeFirstRun(data) {
     localStorage.setItem('nebula-first-run-complete', JSON.stringify(data));
+    if (hasNebulaNativeBridge()) {
+      window.nebulaNative.postMessage('complete-first-run', JSON.stringify(data));
+    }
   }
 };
 
+const nativeApi = window.api || (hasNebulaNativeBridge() ? createNebulaNativeApi() : fallbackApi);
+
 // Initialize setup when DOM is ready
 document.addEventListener('DOMContentLoaded', async () => {
   console.log('[Setup] Initializing first-time setup...');
@@ -67,9 +189,7 @@ async function loadThemes() {
     console.error('[Setup] Error loading themes:', error);
     // Fallback to a default theme
     setupState.themes = {
-      default: {
+      default: getPresetThemes()
-        default: { name: 'Default', description: 'Classic Nebula theme', colors: { bg: '#121418', primary: '#7B2EFF', accent: '#00C6FF' } }
-      }
     };
     renderThemeGrid(setupState.themes);
   }
@@ -167,8 +287,9 @@ function hexToRgb(hex) {
  * Apply theme to the setup page UI and persist selection
  */
 function applyThemeToSetupPage(theme, themeId = null) {
-  if (!theme || !theme.colors) return;
+  const completeTheme = normalizeTheme(theme);
-  const colors = theme.colors;
+  if (!completeTheme || !completeTheme.colors) return;
+  const colors = completeTheme.colors;
   const root = document.documentElement;
 
   const setVar = (cssVar, value, fallback) => {
@@ -202,15 +323,15 @@ function applyThemeToSetupPage(theme, themeId = null) {
     setVar('--warning-rgb', `${warningRgb.r}, ${warningRgb.g}, ${warningRgb.b}`);
   }
 
-  if (theme.gradient) {
+  if (completeTheme.gradient) {
-    document.body.style.background = theme.gradient;
+    document.body.style.background = completeTheme.gradient;
   } else if (colors.bg) {
     document.body.style.background = colors.bg;
   }
 
   // Persist for main UI to pick up on first load
   try {
-    localStorage.setItem('currentTheme', JSON.stringify(theme));
+    localStorage.setItem('currentTheme', JSON.stringify(completeTheme));
     if (themeId) localStorage.setItem('activeThemeName', themeId);
   } catch (err) {
     console.warn('[Setup] Failed to persist theme:', err);
@@ -355,7 +476,7 @@ async function setDefaultBrowser() {
     const result = await nativeApi.setAsDefaultBrowser();
     
     if (result.success) {
-      const isDefault = await window.api.isDefaultBrowser();
+      const isDefault = !!result.isDefault || await nativeApi.isDefaultBrowser();
       if (isDefault) {
         setupState.defaultBrowserSet = true;
         
@@ -499,7 +620,9 @@ async function completeSetup() {
     
     console.log('[Setup] First-time setup completed successfully');
     
-    window.location.href = 'home.html';
+    if (!hasNebulaNativeBridge()) {
+      window.location.href = 'home.html';
+    }
   } catch (error) {
     console.error('[Setup] Error completing setup:', error);
     alert('There was an error saving your preferences. Please try again.');
@@ -522,7 +645,9 @@ async function skipSetup() {
     
     console.log('[Setup] Setup skipped, using defaults');
     
-    window.location.href = 'home.html';
+    if (!hasNebulaNativeBridge()) {
+      window.location.href = 'home.html';
+    }
   } catch (error) {
     console.error('[Setup] Error skipping setup:', error);
     window.location.href = 'home.html';

ui/pages/404.html

@@ -61,7 +61,7 @@
   const attemptedUrl = params.get('url');
   const box = document.getElementById('targetBox');
   if (attemptedUrl) {
-    box.textContent = decodeURIComponent(attemptedUrl);
+    box.textContent = attemptedUrl;
   } else {
     box.textContent = 'Unknown URL';
   }

ui/pages/bigpicture.html

@@ -26,6 +26,10 @@
       <div class="bg-particles"></div>
       <div class="bg-glow"></div>
     </div>
+    <div id="browser-stage-frame" class="browser-stage-frame hidden" aria-hidden="true"></div>
+    <div id="virtual-cursor" class="virtual-cursor hidden" aria-hidden="true">
+      <div class="virtual-cursor-dot"></div>
+    </div>
 
     <!-- Top header bar -->
     <header class="bp-header">
@@ -41,6 +45,9 @@
       </div>
       <div class="header-right">
         <div class="status-icons">
+          <span id="bp-controller-status" class="status-icon controller-status disconnected" title="Controller disconnected">
+            <span class="material-symbols-outlined">sports_esports</span>
+          </span>
           <span id="bp-wifi" class="status-icon" title="Connected">
             <span class="material-symbols-outlined">wifi</span>
           </span>
@@ -123,13 +130,6 @@
             </div>
           </div>
 
-          <!-- Recent sites -->
-          <div class="recent-sites">
-            <h2 class="subsection-title">Continue Browsing</h2>
-            <div class="horizontal-scroll" id="recentSitesScroll">
-              <!-- Recent sites will be populated dynamically -->
-            </div>
-          </div>
         </section>
 
         <!-- Browse section (for webview) -->
@@ -162,20 +162,19 @@
         <section id="section-history" class="bp-section">
           <div class="section-header">
             <h1 class="section-title">History</h1>
-            <p class="section-subtitle">Recently visited sites</p>
+            <p class="section-subtitle">Recently visited sites from this profile</p>
           </div>
           <div class="section-actions">
-            <button class="action-btn" id="clearHistoryBtn" data-focusable tabindex="0">
+            <button class="action-btn danger" id="bp-clear-history" data-focusable tabindex="0">
-              <span class="material-symbols-outlined">delete_sweep</span>
+              <span class="material-symbols-outlined">delete</span>
               <span>Clear History</span>
             </button>
-            <button class="action-btn" id="refreshHistoryBtn" data-focusable tabindex="0">
-              <span class="material-symbols-outlined">refresh</span>
-              <span>Refresh</span>
-            </button>
           </div>
           <div class="list-container" id="historyList">
-            <!-- History will be populated dynamically -->
+            <div class="empty-state">
+              <span class="material-symbols-outlined">history</span>
+              <p>No browsing history</p>
+            </div>
           </div>
         </section>
 
@@ -364,7 +363,7 @@
                   </div>
                 </div>
                 <div class="option-control">
-                  <button class="action-button" id="bp-clear-history" data-focusable tabindex="0">
+                  <button class="action-button" id="bp-clear-history-settings" data-focusable tabindex="0">
                     <span class="material-symbols-outlined">delete</span>
                     <span>Clear</span>
                   </button>
@@ -435,28 +434,28 @@
 
     <!-- Bottom controller hints -->
     <footer class="bp-footer">
-      <div class="controller-hints">
+      <div class="controller-hints" id="controller-hints">
         <div class="hint">
           <span class="controller-btn dpad">
             <span class="material-symbols-outlined">gamepad</span>
           </span>
-          <span>Navigate</span>
+          <span id="hint-navigate">Navigate</span>
         </div>
         <div class="hint">
           <span class="controller-btn a-btn">A</span>
-          <span>Select</span>
+          <span id="hint-a">Select</span>
         </div>
         <div class="hint">
           <span class="controller-btn b-btn">B</span>
-          <span>Back</span>
+          <span id="hint-b">Back</span>
         </div>
         <div class="hint">
           <span class="controller-btn y-btn">Y</span>
-          <span>Search</span>
+          <span id="hint-y">Search</span>
         </div>
         <div class="hint">
           <span class="controller-btn menu-btn">☰</span>
-          <span>Menu</span>
+          <span id="hint-menu">Menu</span>
         </div>
       </div>
     </footer>

ui/pages/chrome.html

@@ -0,0 +1,69 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1.0">
+  <title>Nebula Chrome</title>
+  <link rel="stylesheet" href="../css/chrome.css">
+</head>
+<body>
+  <div class="nebula-chrome" data-drag-region>
+    <div class="title-row" data-drag-region>
+      <div class="tabs" role="tablist" aria-label="Nebula tabs">
+        <button id="active-tab" class="tab active" type="button" role="tab" aria-selected="true">
+          <span id="tab-favicon" class="tab-favicon"></span>
+          <span id="tab-title" class="tab-title">New Tab</span>
+          <span id="tab-loading" class="tab-loading" hidden></span>
+        </button>
+        <button class="tab-add" type="button" data-command="new-tab" title="New tab" aria-label="New tab">
+          <i data-lucide="plus"></i>
+        </button>
+      </div>
+
+      <div class="window-controls" aria-label="Window controls">
+        <button type="button" data-command="minimize" aria-label="Minimize">
+          <i data-lucide="minus"></i>
+        </button>
+        <button type="button" data-command="maximize" aria-label="Maximize">
+          <i data-lucide="square"></i>
+        </button>
+        <button type="button" data-command="close" class="close" aria-label="Close">
+          <i data-lucide="x"></i>
+        </button>
+      </div>
+    </div>
+
+    <div class="toolbar">
+      <button id="back-button" class="icon-button" type="button" data-command="back" aria-label="Back" disabled>
+        <i data-lucide="chevron-left"></i>
+      </button>
+      <button id="forward-button" class="icon-button" type="button" data-command="forward" aria-label="Forward" disabled>
+        <i data-lucide="chevron-right"></i>
+      </button>
+      <button id="reload-button" class="icon-button" type="button" data-command="reload" aria-label="Reload">
+        <i data-lucide="rotate-cw"></i>
+      </button>
+      <button class="icon-button" type="button" data-command="home" aria-label="Home">
+        <i data-lucide="home"></i>
+      </button>
+
+      <form id="address-form" class="address-shell" autocomplete="off">
+        <div id="progress-bar" class="progress-bar"></div>
+        <label class="sr-only" for="address-input">Search or enter address</label>
+        <input id="address-input" type="text" spellcheck="false" placeholder="Search or enter address">
+      </form>
+
+      <button class="icon-button" type="button" data-command="settings" aria-label="Settings">
+        <i data-lucide="settings"></i>
+      </button>
+      <button class="icon-button menu-button" type="button" data-command="menu-popup" aria-label="Open menu" title="Open menu">
+        <i data-lucide="menu"></i>
+      </button>
+    </div>
+  </div>
+
+  <script src="../js/lucide.min.js"></script>
+  <script>lucide.createIcons();</script>
+  <script src="../js/chrome.js"></script>
+</body>
+</html>

ui/pages/insecure.html

@@ -62,6 +62,10 @@
   const box = document.getElementById('targetBox');
   if (target) box.textContent = target;
   function sendNavigate(url, opts){
+    if (opts && opts.insecureBypass && window.nebulaNative && window.nebulaNative.postMessage){
+      window.nebulaNative.postMessage('navigate-insecure', url);
+      return;
+    }
     if (window.electronAPI && window.electronAPI.sendToHost){
       window.electronAPI.sendToHost('navigate', url, opts||{});
     } else if (window.parent && window.parent !== window) {

ui/pages/menu-popup.html

@@ -1,23 +1,28 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
 <head>
-  <meta charset="UTF-8" />
+  <meta charset="UTF-8">
-  <title>Menu</title>
+  <meta name="viewport" content="width=device-width, initial-scale=1.0">
-  <link rel="stylesheet" href="../css/menu-popup.css" />
+  <title>Nebula Menu</title>
+  <link rel="stylesheet" href="../css/menu-popup.css">
 </head>
 <body>
-  <div id="menu-popup" role="menu">
+  <main id="menu-popup" role="menu" aria-label="Nebula browser menu">
-    <button data-cmd="open-settings" role="menuitem">Settings</button>
+    <button type="button" role="menuitem" data-cmd="open-settings">Settings</button>
-    <button data-cmd="big-picture" role="menuitem">🎮 Big Picture Mode</button>
+    <button type="button" role="menuitem" data-cmd="gpu-diagnostics">GPU diagnostics</button>
-    <button data-cmd="toggle-devtools" role="menuitem">Toggle Developer Tools</button>
+    <button type="button" role="menuitem" data-cmd="big-picture">Big Picture mode</button>
-    <div class="zoom-controls" role="group" aria-label="Zoom controls">
+    <button type="button" role="menuitem" data-cmd="toggle-devtools">Developer tools</button>
-      <button data-cmd="zoom-out" aria-label="Zoom out">-</button>
+
+    <div class="zoom-controls" aria-label="Page zoom">
+      <button type="button" data-cmd="zoom-out" aria-label="Zoom out">-</button>
       <span id="zoom-percent">100%</span>
-      <button data-cmd="zoom-in" aria-label="Zoom in">+</button>
+      <button type="button" data-cmd="zoom-in" aria-label="Zoom in">+</button>
     </div>
-    <button data-cmd="hard-reload" role="menuitem">Hard Reload (Ignore Cache)</button>
+
-    <button data-cmd="fresh-reload" role="menuitem">Reload Fresh (Add Cache-Buster)</button>
+    <button type="button" role="menuitem" data-cmd="hard-reload">Hard reload</button>
-  </div>
+    <button type="button" role="menuitem" data-cmd="fresh-reload">Fresh reload</button>
+  </main>
+
   <script src="../js/menu-popup.js"></script>
 </body>
 </html>

ui/pages/nebot.html

@@ -1,59 +0,0 @@
-<!DOCTYPE html>
-<html>
-<head>
-  <meta charset="UTF-8" />
-  <title>Nebot</title>
-  <link rel="stylesheet" href="../plugins/nebot/page.css" onerror="this.remove()"/>
-  <style>
-    body { margin:0; font-family: system-ui,-apple-system,Segoe UI,Roboto,sans-serif; background:#12141c; color:#e6e8ef; }
-    .fallback { max-width:620px; margin:60px auto; padding:32px 36px; background:#1d222e; border:1px solid rgba(255,255,255,0.08); border-radius:18px; }
-    .fallback h1 { margin:0 0 12px; font-size:28px; background:linear-gradient(90deg,#a48bff,#6cb6ff); -webkit-background-clip:text; color:transparent; }
-    .fallback p { line-height:1.55; }
-    .tip { background:#232b38; padding:10px 14px; border-radius:10px; font-size:13px; margin-top:18px; border:1px solid rgba(255,255,255,0.08); }
-    .err { color:#ff6d7d; font-weight:600; }
-    #mount { min-height:400px; }
-  </style>
-</head>
-<body>
-  <div id="mount"></div>
-  <script>
-    (async function(){
-      // Wait a tick so plugin preload (renderer-preload) runs and exposes window.ollamaChat
-      const mount = document.getElementById('mount');
-      function showFallback(reason){
-        mount.innerHTML = `<div class="fallback">`+
-          `<h1>Nebot</h1>`+
-          `<p>The Nebot plugin page could not load automatically.</p>`+
-          (reason?`<p class='err'>${reason}</p>`:'')+
-          `<div class="tip"><strong>How to fix</strong><br/>1. Ensure the Nebot plugin folder exists at plugins/nebot.<br/>2. Confirm plugin is enabled (manifest enabled: true).<br/>3. Restart the app so the plugin manager registers pages.</div>`+
-        `</div>`;
-      }
-      try {
-        // Try to fetch plugin page HTML directly
-        const res = await fetch('../plugins/nebot/page.html');
-        if(!res.ok){ showFallback('Missing page.html (status '+res.status+').'); return; }
-        const html = await res.text();
-        // Simple sandboxed injection
-        mount.innerHTML = html;
-        // The injected page expects its CSS & JS relative to itself; adjust asset paths
-        const fixLinks = mount.querySelectorAll('link[rel="stylesheet"], script[src]');
-        fixLinks.forEach(el=>{
-          const attr = el.tagName==='SCRIPT'?'src':'href';
-          if(el.getAttribute(attr) && !/plugins\/nebot\//.test(el.getAttribute(attr))){
-            el.setAttribute(attr,'../plugins/nebot/'+el.getAttribute(attr));
-          }
-        });
-        // Inject JS if not already present
-        if(!mount.querySelector('script[data-nebot-page]')){
-          const s=document.createElement('script'); s.dataset.nebotPage='1'; 
-          // Pass the current URL hash to the page script for debug mode
-          s.src='../plugins/nebot/page.js' + window.location.hash; 
-          mount.appendChild(s);
-        }
-      } catch(e){
-        showFallback(e.message||'Unknown error');
-      }
-    })();
-  </script>
-</body>
-</html>

ui/pages/settings.html

@@ -45,6 +45,15 @@
           </div>
         </div>
 
+        <div class="setting-group">
+          <h3>Default Browser</h3>
+          <p class="note">Use Nebula Browser for web links opened from other apps.</p>
+          <div class="setting-row">
+            <button id="set-default-browser-btn" class="primary-btn">Make Default Browser</button>
+            <span id="default-browser-status" class="note">Checking status...</span>
+          </div>
+        </div>
+
         <div class="setting-group">
           <h3>Weather Display</h3>
           <p class="note">Choose how temperature is displayed on the Home page weather card.</p>
@@ -293,12 +302,12 @@
 
         <div class="customization-group about-actions">
           <button id="copy-about-btn">Copy diagnostics</button>
-          <a id="github-link" href="https://github.com/Bobbybear007/NebulaBrowser" class="github-btn" rel="noopener noreferrer">
+          <a id="github-link" href="https://gitpub.zambazosmedia.group/#repo/nebula-project/NebulaBrowser" class="github-btn" rel="noopener noreferrer">
             <!-- GitHub mark (Octicons) MIT License -->
             <svg viewBox="0 0 16 16" aria-hidden="true" focusable="false" role="img">
               <path d="M8 0C3.58 0 0 3.58 0 8c0 3.54 2.29 6.53 5.47 7.59.4.07.55-.17.55-.38 0-.19-.01-.82-.01-1.49-2.01.37-2.53-.49-2.69-.94-.09-.23-.48-.94-.82-1.13-.28-.15-.68-.52-.01-.53.63-.01 1.08.58 1.23.82.72 1.21 1.87.87 2.33.66.07-.52.28-.87.51-1.07-1.78-.2-3.64-.89-3.64-3.95 0-.87.31-1.59.82-2.15-.08-.2-.36-1.01.08-2.11 0 0 .67-.21 2.2.82.64-.18 1.32-.27 2-.27.68 0 1.36.09 2 .27 1.53-1.04 2.2-.82 2.2-.82.44 1.1.16 1.91.08 2.11.51.56.82 1.27.82 2.15 0 3.07-1.87 3.75-3.65 3.95.29.25.54.73.54 1.48 0 1.07-.01 1.93-.01 2.2 0 .21.15.46.55.38A8.013 8.013 0 0 0 16 8c0-4.42-3.58-8-8-8z"/>
             </svg>
-            <span>GitHub</span>
+            <span>Gitpub</span>
           </a>
           <a id="help-link" href="https://nebula.zambazosmedia.group" class="help-btn" rel="noopener noreferrer">
             <!-- Help icon -->
@@ -489,8 +498,10 @@
             a.addEventListener('click', (e) => {
               e.preventDefault();
               try {
-                if (window.electronAPI && typeof window.electronAPI.sendToHost === 'function') {
+                if (window.nebulaNative && typeof window.nebulaNative.postMessage === 'function') {
-                  // Ask the host to open this URL in a new tab to keep Settings open
+                  // Ask the CEF host to open this URL in a new tab to keep Settings open.
+                  window.nebulaNative.postMessage('new-tab', item);
+                } else if (window.electronAPI && typeof window.electronAPI.sendToHost === 'function') {
                   window.electronAPI.sendToHost('navigate', item, { newTab: true });
                 } else if (window.parent && window.parent !== window) {
                   // Fallback: postMessage to parent if available
@@ -534,6 +545,12 @@
 
     async function clearSiteHistory() {
       try {
+        if (window.electronAPI && typeof window.electronAPI.sendToHost === 'function') {
+          window.electronAPI.sendToHost('clear-site-history');
+        } else if (window.nebulaNative && typeof window.nebulaNative.postMessage === 'function') {
+          window.nebulaNative.postMessage('clear-site-history');
+        }
+
         // Clear from localStorage
         localStorage.removeItem('siteHistory');
         console.log('[SETTINGS DEBUG] Cleared site history from localStorage');

ui/pages/setup.html

@@ -129,6 +129,7 @@
     </div>
   </div>
 
+  <script src="../js/customization.js"></script>
   <script src="../js/setup.js"></script>
 </body>
 </html>