fix: derive v8_control_flow_integrity from target_os for win-arm64 cross-compile

The snapshot toolchain (linux:clang_x64_v8_arm64) has current_os=linux,
so arm_control_flow_integrity defaults to 'standard' there while the
win-arm64 target gets 'none'. v8_control_flow_integrity then disagrees
between mksnapshot and the runtime, mksnapshot bakes pacibsp/autibsp
into the builtins, and electron.exe fast-fails with
FAST_FAIL_POINTER_AUTH_INVALID_RETURN_ADDRESS on real hardware.

Key v8_control_flow_integrity on target_os so it evaluates the same in
every toolchain.

.github/actions/build-electron/action.yml

@@ -42,111 +42,8 @@ runs:
       shell: bash
       if: ${{ inputs.target-platform == 'win' }}
       run: |
-        GN_APPENDED_ARGS="$GN_EXTRA_ARGS target_cpu=\"${{ inputs.target-arch }}\" use_v8_context_snapshot=true v8_win_cross_compile_using_wine=true target_os=\"win\""
+        GN_APPENDED_ARGS="$GN_EXTRA_ARGS target_os=\"win\" target_cpu=\"${{ inputs.target-arch }}\" use_v8_context_snapshot=true"
         echo "GN_EXTRA_ARGS=$GN_APPENDED_ARGS" >> $GITHUB_ENV
-        echo "ELECTRON_BUILD_TOOLS_MAIN_STAR=`pwd`/src/electron/build/siso/main.star" >> $GITHUB_ENV
-    - name: Install wine for Windows builds on non-Windows hosts
-      shell: bash
-      if: ${{ inputs.target-platform == 'win' && runner.os != 'Windows' }}
-      run: |
-        sudo mkdir -pm755 /etc/apt/keyrings
-        wget -O - https://dl.winehq.org/wine-builds/winehq.key | sudo gpg --dearmor -o /etc/apt/keyrings/winehq-archive.key -
-        sudo dpkg --add-architecture i386
-        sudo wget -NP /etc/apt/sources.list.d/ https://dl.winehq.org/wine-builds/ubuntu/dists/jammy/winehq-jammy.sources
-        sudo apt-get update  
-        sudo apt install -y --install-recommends winehq-stable libgcc-s1:i386 libgcc-s1
-        # Increase virtual memory limits for Wine's VirtualAlloc (V8 sandbox
-        # reserves a very large contiguous region that fails under default limits)
-        sudo sysctl vm.mmap_min_addr
-        sudo sysctl -w vm.mmap_min_addr=65536
-        sudo sysctl -w vm.max_map_count=1048576
-        sudo sysctl -w vm.overcommit_memory=1
-        sudo sysctl -w kernel.randomize_va_space=0
-        if [ -x /usr/bin/wine ]; then
-          WINE_PATH=/usr/bin/wine
-        elif command -v wine >/dev/null 2>&1; then
-          WINE_PATH=$(command -v wine)
-        fi
-        if [ -z "$WINE_PATH" ] || [ ! -x "$WINE_PATH" ]; then
-          echo "ERROR: wine binary not found anywhere after install"
-          exit 1
-        fi
-        echo "Found wine at: $WINE_PATH"
-        export WINEPREFIX="$HOME/.wine"
-        mkdir -p "$WINEPREFIX"
-        echo "WINEPREFIX=$WINEPREFIX" >> $GITHUB_ENV
-        # Start a persistent Xvfb server for wine (xvfb-run per-invocation hangs
-        # because wineserver keeps the X connection alive)
-        export DISPLAY=:99.0
-        echo "DISPLAY=:99.0" >> $GITHUB_ENV
-        export XDG_RUNTIME_DIR=/tmp/runtime-$(whoami)
-        echo "XDG_RUNTIME_DIR=$XDG_RUNTIME_DIR" >> $GITHUB_ENV
-        mkdir -p "$XDG_RUNTIME_DIR"
-        echo "Starting Xvfb on :99 with 1024x768x24 resolution"
-        Xvfb :99 -screen 0 1024x768x24 &
-        echo "Wait for Xvfb to be ready"
-        # Wait for Xvfb to be ready (up to 5 seconds)
-        for i in $(seq 1 10); do
-          if xdpyinfo -display :99 >/dev/null 2>&1; then
-            echo "Xvfb is running on :99"
-            break
-          fi
-          echo "xvfb not ready yet, waiting..."
-          sleep 0.5
-        done
-        if ! xdpyinfo -display :99 >/dev/null 2>&1; then
-          echo "ERROR: Xvfb failed to start"
-          exit 1
-        fi
-        echo "Xvfb is ready; about to run wineboot"
-
-        export WINEDEBUG=-all
-        echo "WINEDEBUG=$WINEDEBUG" >> $GITHUB_ENV
-        export WINEARCH=win64
-        echo "WINEARCH=$WINEARCH" >> $GITHUB_ENV
-        WINEDLLOVERRIDES="mscoree,mshtml=" wineboot --init
-        echo "Done running wineboot"
-        # Initialize wine prefix to avoid first-run delays during build
-        #"$WINE_PATH" wineboot --init 2>/dev/null || true
-        WINE_WRAPPER="/usr/local/bin/xvfb-wine"
-        printf '#!/bin/sh\nsetarch x86_64 -R %s "$@"\n' "$WINE_PATH" | sudo tee "$WINE_WRAPPER" > /dev/null
-        sudo chmod +x "$WINE_WRAPPER"
-        GN_APPENDED_ARGS="$GN_EXTRA_ARGS v8_wine_path=\"$WINE_WRAPPER\""
-
-        # Pass wine path to GN so siso can find it regardless of PATH
-        GN_APPENDED_ARGS="$GN_EXTRA_ARGS v8_wine_path=\"$WINE_PATH\""
-        echo "GN_EXTRA_ARGS=$GN_APPENDED_ARGS" >> $GITHUB_ENV
-        echo "GN APPENDED_ARGS set with wine path: $GN_APPENDED_ARGS"
-        echo "Wine setup complete"
-    # - name: Download mksnapshot.zip
-    #   shell: bash
-    #   if: ${{ inputs.target-platform == 'win' }}
-    #   run: |
-    #     # Download mksnapshot.zip from https://electronbuildtools.blob.core.windows.net/windows-toolchains/mksnapshot.zip
-    #     curl -L -o mksnapshot.zip https://electronbuildtools.blob.core.windows.net/windows-toolchains/mksnapshot.zip
-    #     if [ $? -ne 0 ]; then
-    #       echo "Failed to download mksnapshot.zip"
-    #       exit 1
-    #     fi
-    #     if [ -f mksnapshot.zip ]; then
-    #       echo "Successfully downloaded mksnapshot.zip"
-    #     else
-    #       echo "mksnapshot.zip not found after download"
-    #       exit 1
-    #     fi
-    #     if [ -f mksnapshot.zip ]; then
-    #       unzip mksnapshot.zip -d mksnapshot || true
-    #       PREBUILT_MKSNAPSHOT="$(pwd)/mksnapshot/mksnapshot.exe"
-    #       if [ -f "$PREBUILT_MKSNAPSHOT" ]; then
-    #         GN_APPENDED_ARGS="$GN_EXTRA_ARGS v8_prebuilt_mksnapshot=\"$PREBUILT_MKSNAPSHOT\""
-    #         echo "GN_EXTRA_ARGS=$GN_APPENDED_ARGS" >> $GITHUB_ENV
-    #         echo "Using pre-built mksnapshot at $PREBUILT_MKSNAPSHOT"
-    #       else
-    #         echo "mksnapshot binary not found in mksnapshot.zip, will build from source"
-    #       fi
-    #     else
-    #       echo "mksnapshot.zip not found, skipping unzip and PATH update"
-    #     fi        
     - name: Add Clang problem matcher
       shell: bash
       run: echo "::add-matcher::src/electron/.github/problem-matchers/clang.json"
@@ -185,11 +82,7 @@ runs:
         node electron/script/check-symlinks.js
 
         # Build stats and object checksums
-        if [ "$TARGET_PLATFORM" = "win" ]; then
-          BUILD_STATS_ARGS="out/Default/siso.exe.INFO --out-dir out/Default --output-object-checksums object-checksums.${{ inputs.artifact-platform }}_${{ inputs.target-arch }}.json"
-        else
-          BUILD_STATS_ARGS="out/Default/siso.INFO --out-dir out/Default --output-object-checksums object-checksums.${{ inputs.artifact-platform }}_${{ inputs.target-arch }}.json"
-        fi
+        BUILD_STATS_ARGS="out/Default/siso.INFO --out-dir out/Default --output-object-checksums object-checksums.${{ inputs.artifact-platform }}_${{ inputs.target-arch }}.json"
         if [ -f previous-object-checksums.json ]; then
           BUILD_STATS_ARGS="$BUILD_STATS_ARGS --input-object-checksums previous-object-checksums.json"
         fi
@@ -226,7 +119,7 @@ runs:
         sed $SEDOPTION '/--warn-about-builtin-profile-data/d' out/Default/mksnapshot_args
         sed $SEDOPTION '/--abort-on-bad-builtin-profile-data/d' out/Default/mksnapshot_args
 
-        (cd out/Default; zip mksnapshot.zip mksnapshot_args gen/v8/embedded.S)        
+        (cd out/Default; zip mksnapshot.zip mksnapshot_args gen/v8/embedded.S)
     - name: Generate Cross-Arch Snapshot (arm/arm64)  ${{ inputs.step-suffix }}
       shell: bash
       if: ${{ (inputs.target-arch == 'arm' || inputs.target-arch == 'arm64') && inputs.target-platform == 'linux' }}
@@ -260,12 +153,6 @@ runs:
           fi
           electron/script/zip_manifests/check-zip-manifest.py out/Default/chromedriver.zip electron/script/zip_manifests/chromedriver_zip.$target_os.${{ inputs.target-arch }}.manifest
         fi
-    - name: Profile Windows Toolchain ${{ inputs.step-suffix }}
-      shell: bash
-      if: ${{ inputs.is-release == 'true' && inputs.target-platform == 'win' }}
-      run: |
-        cd src
-        python3 electron/build/profile_toolchain.py --output-json=out/Default/windows_toolchain_profile.json
     - name: Add msdia140.dll to Path ${{ inputs.step-suffix }}
       shell: bash
       if: ${{ inputs.is-release == 'true' && inputs.target-platform == 'win' }}

.github/actions/install-build-tools/action.yml

@@ -15,7 +15,7 @@ runs:
         git config --global core.preloadindex true
         git config --global core.longpaths true
       fi
-      export BUILD_TOOLS_SHA=1aa9dce0b3fa9353c38a6c3d4aac0249f0f68973
+      export BUILD_TOOLS_SHA=03f1603d5698368077ae830599b0b6f6248325b1
       npm i -g @electron/build-tools
       # Update depot_tools to ensure python
       e d update_depot_tools

.github/workflows/build.yml

@@ -11,12 +11,12 @@ on:
       skip-macos:
         type: boolean
         description: 'Skip macOS builds'
-        default: true
+        default: false
         required: false
       skip-linux:
         type: boolean
         description: 'Skip Linux builds'
-        default: true
+        default: false
         required: false
       skip-windows:
         type: boolean
@@ -108,7 +108,7 @@ jobs:
   # Checkout Jobs
   checkout-macos:
     needs: setup
-    if: ${{ needs.setup.outputs.src == 'true' && inputs.skip-macos == 'false'}}
+    if: ${{ needs.setup.outputs.src == 'true' && !inputs.skip-macos}}
     runs-on: electron-arc-centralus-linux-amd64-32core
     permissions:
       contents: read
@@ -138,7 +138,7 @@ jobs:
 
   checkout-linux:
     needs: setup
-    if: ${{ inputs.skip-linux == 'false' }}
+    if: ${{ !inputs.skip-linux}}
     runs-on: electron-arc-centralus-linux-amd64-32core
     permissions:
       contents: read

.github/workflows/pipeline-segment-electron-build.yml

@@ -137,7 +137,7 @@ jobs:
     - name: Enable windows toolchain
       if: ${{ inputs.target-platform == 'win' }}
       run: |
-        echo "ELECTRON_DEPOT_TOOLS_WIN_TOOLCHAIN=1" >> $GITHUB_ENV      
+        echo "ELECTRON_DEPOT_TOOLS_WIN_TOOLCHAIN=1" >> $GITHUB_ENV
     - name: Set GN_EXTRA_ARGS for Linux
       if: ${{ inputs.target-platform == 'linux' }}
       run: |
@@ -172,7 +172,7 @@ jobs:
       if: ${{ inputs.target-platform != 'macos' }}
       uses: ./src/electron/.github/actions/restore-cache-aks
       with:
-        target-platform: ${{ inputs.target-platform }}      
+        target-platform: ${{ inputs.target-platform }}
     - name: Checkout Electron
       uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd
       with:
@@ -189,14 +189,10 @@ jobs:
     - name: Init Build Tools
       run: |
         e init -f --root=$(pwd) --out=Default ${{ inputs.gn-build-type }} --import ${{ inputs.gn-build-type }} --target-cpu ${{ inputs.target-arch }} --remote-build siso
-        e sanitize-config
     - name: Run Electron Only Hooks
       run: |
-        if [ "${{ inputs.target-platform }}" = "win" ]; then
-          rm -rf src/third_party/depot_tools/win_toolchain/vs_files*
-        fi
         echo "solutions=[{'name':'src/electron','url':None,'deps_file':'DEPS','custom_vars':{'process_deps':False},'managed':False}]" > tmpgclient
-        if [ "${{ inputs.target-platform }}" = "win" ]; then          
+        if [ "${{ inputs.target-platform }}" = "win" ]; then
           echo "target_os=['win']" >> tmpgclient
         fi
         gclient runhooks --gclientfile=tmpgclient
@@ -242,11 +238,3 @@ jobs:
         generate-symbols: '${{ inputs.generate-symbols }}'
         upload-to-storage: '${{ inputs.upload-to-storage }}'
         step-suffix: '(mas)'
-    - name: Wait for active SSH sessions
-      shell: bash
-      if: always() && !cancelled()
-      run: |
-        while [ -f /var/.ssh-lock ]
-        do
-          sleep 60
-        done        

.github/workflows/pipeline-segment-electron-publish.yml

@@ -142,6 +142,10 @@ jobs:
       - name: Install AZCopy
         if: ${{ inputs.target-platform == 'macos' }}
         run: brew install azcopy
+      - name: Enable windows toolchain
+        if: ${{ inputs.target-platform == 'win' }}
+        run: |
+          echo "ELECTRON_DEPOT_TOOLS_WIN_TOOLCHAIN=1" >> $GITHUB_ENV
       - name: Set GN_EXTRA_ARGS for Linux
         if: ${{ inputs.target-platform == 'linux' }}
         run: >
@@ -169,13 +173,15 @@ jobs:
           echo "DEPSHASH=$DEPSHASH" >> $GITHUB_ENV
           echo "CACHE_PATH=$DEPSHASH.tar" >> $GITHUB_ENV
       - name: Restore src cache via AZCopy
-        if: ${{ inputs.target-platform != 'linux' }}
+        if: ${{ inputs.target-platform == 'macos' }}
         uses: ./src/electron/.github/actions/restore-cache-azcopy
         with:
           target-platform: ${{ inputs.target-platform }}
       - name: Restore src cache via AKS
-        if: ${{ inputs.target-platform == 'linux' }}
+        if: ${{ inputs.target-platform != 'macos' }}
         uses: ./src/electron/.github/actions/restore-cache-aks
+        with:
+          target-platform: ${{ inputs.target-platform }}
       - name: Checkout Electron
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd
         with:
@@ -183,7 +189,7 @@ jobs:
           fetch-depth: 0
           ref: ${{ github.event.pull_request.head.sha }}
       - name: Fix Sync
-        if: ${{ inputs.target-platform != 'linux' }}
+        if: ${{ inputs.target-platform == 'macos' }}
         uses: ./src/electron/.github/actions/fix-sync
         with:
           target-platform: ${{ inputs.target-platform }}
@@ -196,7 +202,15 @@ jobs:
           inputs.target-arch }} --remote-build siso
       - name: Run Electron Only Hooks
         run: |
-          e d gclient runhooks --spec="solutions=[{'name':'src/electron','url':None,'deps_file':'DEPS','custom_vars':{'process_deps':False},'managed':False}]"
+          echo "solutions=[{'name':'src/electron','url':None,'deps_file':'DEPS','custom_vars':{'process_deps':False},'managed':False}]" > tmpgclient
+          if [ "${{ inputs.target-platform }}" = "win" ]; then
+            echo "target_os=['win']" >> tmpgclient
+          fi
+          gclient runhooks --gclientfile=tmpgclient
+          # Fix VS Toolchain
+          if [ "${{ inputs.target-platform }}" = "win" ]; then
+            e d python3 src/build/vs_toolchain.py update --force
+          fi
       - name: Regenerate DEPS Hash
         run: >
           (cd src/electron && git checkout .) && node

.github/workflows/windows-publish.yml

@@ -61,7 +61,8 @@ jobs:
     needs: checkout-windows
     with:
       environment: production-release
-      build-runs-on: electron-arc-centralus-windows-amd64-16core
+      build-runs-on: electron-arc-centralus-linux-amd64-32core
+      build-container: '{"image":"ghcr.io/electron/build:${{ needs.checkout-windows.outputs.build-image-sha }}","options":"--user root --device /dev/fuse --cap-add SYS_ADMIN","volumes":["/mnt/win-cache:/mnt/win-cache"]}'
       target-platform: win
       target-arch: x64
       is-release: true
@@ -80,7 +81,8 @@ jobs:
     needs: checkout-windows
     with:
       environment: production-release
-      build-runs-on: electron-arc-centralus-windows-amd64-16core
+      build-runs-on: electron-arc-centralus-linux-amd64-32core
+      build-container: '{"image":"ghcr.io/electron/build:${{ needs.checkout-windows.outputs.build-image-sha }}","options":"--user root --device /dev/fuse --cap-add SYS_ADMIN","volumes":["/mnt/win-cache:/mnt/win-cache"]}'
       target-platform: win
       target-arch: arm64
       is-release: true
@@ -99,7 +101,8 @@ jobs:
     needs: checkout-windows
     with:
       environment: production-release
-      build-runs-on: electron-arc-centralus-windows-amd64-16core
+      build-runs-on: electron-arc-centralus-linux-amd64-32core
+      build-container: '{"image":"ghcr.io/electron/build:${{ needs.checkout-windows.outputs.build-image-sha }}","options":"--user root --device /dev/fuse --cap-add SYS_ADMIN","volumes":["/mnt/win-cache:/mnt/win-cache"]}'
       target-platform: win
       target-arch: x86
       is-release: true

build/siso/main.star

@@ -1,103 +0,0 @@
-load("@builtin//encoding.star", "json")
-load("@builtin//lib/gn.star", "gn")
-load("@builtin//path.star", "path")
-load("@builtin//runtime.star", "runtime")
-load("@builtin//struct.star", "module")
-load("@config//main.star", upstream_init = "init")
-load("@config//win_sdk.star", "win_sdk")
-load("@config//gn_logs.star", "gn_logs")
-
-def init(ctx):
-    mod = upstream_init(ctx)
-    step_config = json.decode(mod.step_config)
-
-    # Buildbarn doesn't support input_root_absolute_path so disable that
-    for rule in step_config["rules"]:    
-      input_root_absolute_path = rule.get("input_root_absolute_path", False)
-      if input_root_absolute_path:
-        rule.pop("input_root_absolute_path", None)
-
-    # Only wrap clang rules with a remote wrapper if not on Linux. These are currently only
-    # needed for X-Compile builds, which run on Windows and Mac.
-    if runtime.os != "linux":
-      for rule in step_config["rules"]:
-        if rule["name"].startswith("clang/") or rule["name"].startswith("clang-cl/"):
-          rule["remote_wrapper"] = "../../buildtools/reclient_cfgs/chromium-browser-clang/clang_remote_wrapper"
-          if "inputs" not in rule:
-            rule["inputs"] = []
-          rule["inputs"].append("buildtools/reclient_cfgs/chromium-browser-clang/clang_remote_wrapper")
-          rule["inputs"].append("third_party/llvm-build/Release+Asserts_linux/bin/clang")
-
-      if "executables" not in step_config:
-        step_config["executables"] = []
-      step_config["executables"].append("buildtools/reclient_cfgs/chromium-browser-clang/clang_remote_wrapper")
-      step_config["executables"].append("third_party/llvm-build/Release+Asserts_linux/bin/clang")
-
-    if runtime.os == "darwin":
-      # Update platforms to match our default siso config instead of reclient configs.
-      step_config["platforms"].update({
-          "clang": step_config["platforms"]["default"],
-          "clang_large": step_config["platforms"]["default"],          
-      })      
-
-    # Add additional Windows SDK headers needed by Electron      
-    win_toolchain_dir = win_sdk.toolchain_dir(ctx)
-    if win_toolchain_dir:
-      sdk_version = gn_logs.read(ctx).get("windows_sdk_version")
-      step_config["input_deps"][win_toolchain_dir + ":headers"].extend([
-        # third_party/electron_node/deps/uv/include/uv/win.h includes mswsock.h
-        path.join(win_toolchain_dir, "Windows Kits", "10/Include", sdk_version, "um/mswsock.h"),
-        # third_party/electron_node/src/debug_utils.cc includes lm.h
-        path.join(win_toolchain_dir, "Windows Kits", "10/Include", sdk_version, "um/Lm.h"),
-      ])
-
-    if runtime.os == "windows":      
-      # Update platforms to match our default siso config instead of reclient configs.
-      step_config["platforms"].update({
-          "clang-cl": step_config["platforms"]["default"],
-          "clang-cl_large": step_config["platforms"]["default"],
-          "lld-link": step_config["platforms"]["default"],
-      })
-
-    # When cross-compiling for Windows using wine, mksnapshot.exe is run via
-    # wine64 on the local machine. The remote execution service cannot handle
-    # this, so force mksnapshot to run locally. The wine64 prefix also changes
-    # the command so the upstream v8/mksnapshot rule's command_prefix won't
-    # match — add an explicit rule for the wine-prefixed command.
-    if "args.gn" in ctx.metadata:
-      gn_args = gn.args(ctx)
-      if gn_args.get("v8_win_cross_compile_using_wine", "").strip('"') == "true":
-        # Force the existing v8/mksnapshot rule to run locally
-        for rule in step_config["rules"]:
-          if rule.get("name") == "v8/mksnapshot":
-            rule["remote"] = False
-
-        # Add a rule that matches the wine64-prefixed mksnapshot command.
-        # With wine, GN emits: python3 ../../v8/tools/run.py <wine_path> ./mksnapshot.exe
-        # The upstream command_prefix ("python3 ...run.py ./mksnapshot") won't
-        # match because wine_path appears before ./mksnapshot.exe.
-        wine_path = gn_args.get("v8_wine_path", "").strip('"')
-        if wine_path:
-          step_config["rules"].insert(0, {
-            "name": "v8/mksnapshot_wine",
-            "command_prefix": "python3 ../../v8/tools/run.py " + wine_path,
-            "remote": False,
-            "timeout": "2m",
-            "output_local": True,
-          })
-          # Same treatment for v8_context_snapshot_generator which uses
-          # gn_run_binary.py instead of v8/tools/run.py.
-          step_config["rules"].insert(0, {
-            "name": "v8/context_snapshot_wine",
-            "command_prefix": "python3 ../../build/gn_run_binary.py " + wine_path,
-            "remote": False,
-            "timeout": "2m",
-            "output_local": True,
-          })
-
-    return module(
-      "config",
-      step_config = json.encode(step_config),
-      filegroups = mod.filegroups,
-      handlers = mod.handlers,
-    )

patches/chromium/.patches

@@ -150,4 +150,3 @@ fix_use_fresh_lazynow_for_onendworkitemimpl_after_didruntask.patch
 fix_pulseaudio_stream_and_icon_names.patch
 fix_fire_menu_popup_start_for_dynamically_created_aria_menus.patch
 feat_allow_enabling_extensions_on_custom_protocols.patch
-chore_run_v8_context_snapshot_generator_through_wine_when.patch

patches/chromium/chore_run_v8_context_snapshot_generator_through_wine_when.patch

@@ -1,49 +0,0 @@
-From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
-From: John Kleinschmidt <kleinschmidtorama@gmail.com>
-Date: Tue, 7 Apr 2026 14:05:09 -0400
-Subject: chore: run v8_context_snapshot_generator through Wine when
- cross-compiling
-
-When cross-compiling for Windows on Linux with Wine, the
-v8_context_snapshot_generator binary is a Windows PE executable (.exe)
-that cannot be run directly. Prepend the wine path to args and append
-.exe to the binary name, matching the approach used for mksnapshot.
-
-diff --git a/tools/v8_context_snapshot/BUILD.gn b/tools/v8_context_snapshot/BUILD.gn
-index ec2357139826613e8b295cb01be341acb03b4737..6c4171dbaf7a76cfc89d71871b73058747675811 100644
---- a/tools/v8_context_snapshot/BUILD.gn
-+++ b/tools/v8_context_snapshot/BUILD.gn
-@@ -50,12 +50,27 @@ if (use_v8_context_snapshot) {
-     output_file = "$root_build_dir/$v8_context_snapshot_filename"
-     output_path = rebase_path(output_file, root_build_dir)
- 
--    args = [
--      "./" + rebase_path(
--              get_label_info(
--                      ":v8_context_snapshot_generator($v8_snapshot_toolchain)",
--                      "root_out_dir") + "/v8_context_snapshot_generator",
--              root_build_dir),
-+    _generator_dir = get_label_info(
-+            ":v8_context_snapshot_generator($v8_snapshot_toolchain)",
-+            "root_out_dir")
-+    if (v8_win_cross_compile_using_wine) {
-+      _generator_bin = "./" + rebase_path(
-+              _generator_dir + "/v8_context_snapshot_generator.exe",
-+              root_build_dir)
-+    } else {
-+      _generator_bin = "./" + rebase_path(
-+              _generator_dir + "/v8_context_snapshot_generator",
-+              root_build_dir)
-+    }
-+
-+    args = []
-+    if (v8_win_cross_compile_using_wine) {
-+      assert(v8_wine_path != "",
-+             "v8_wine_path must be set when v8_win_cross_compile_using_wine is true")
-+      args += [ v8_wine_path ]
-+    }
-+    args += [
-+      _generator_bin,
-       "--snapshot_blob=$snapshot_blob_path",
-       "--output_file=$output_path",
-     ]

patches/v8/.patches

@@ -1,3 +1,6 @@
 chore_allow_customizing_microtask_policy_per_context.patch
 build_warn_instead_of_abort_on_builtin_pgo_profile_mismatch.patch
-feat_support_running_mksnapshot_exe_via_wine_for_windows.patch
+fix_emit_win64_pdata_xdata_for_embedded_builtins_when.patch
+fix_use_clang_x64_v8_arm64_snapshot_toolchain_for_win-arm64_on.patch
+fix_use_zu_for_size_t_in_arm64_emitunwinddata_snprintf.patch
+fix_derive_v8_control_flow_integrity_from_target_os_not.patch

patches/v8/feat_support_running_mksnapshot_exe_via_wine_for_windows.patch

@@ -1,113 +0,0 @@
-From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
-From: John Kleinschmidt <kleinschmidtorama@gmail.com>
-Date: Tue, 24 Mar 2026 16:29:55 -0400
-Subject: feat: support running mksnapshot.exe via Wine for Windows
- cross-compile
-
-When v8_win_cross_compile_using_wine=true is set, mksnapshot is built as a
-Windows .exe using the target toolchain and executed via Wine on the Linux
-host. This avoids needing source-level cross-compile patches for the
-unwinding info code paths.
-
-diff --git a/BUILD.gn b/BUILD.gn
-index 751265ba83c04f0c545248a71b35e46034bfc90a..9ca41b06b569c729496abde7cba085518a9f0d71 100644
---- a/BUILD.gn
-+++ b/BUILD.gn
-@@ -2699,7 +2699,11 @@ template("run_mksnapshot") {
-     suffix = "_$name"
-   }
-   action("run_mksnapshot_" + name) {
--    deps = [ ":mksnapshot($v8_snapshot_toolchain)" ]
-+    if (v8_prebuilt_mksnapshot != "") {
-+      deps = []
-+    } else {
-+      deps = [ ":mksnapshot($v8_snapshot_toolchain)" ]
-+    }
-     if (v8_verify_deterministic_mksnapshot) {
-       # We archive the snapshot executable when verifying snapshot
-       # determinism to ease debugging.
-@@ -2753,10 +2757,26 @@ template("run_mksnapshot") {
-       data += [ "$root_out_dir/mksnapshot_output${suffix}.log" ]
-     }
- 
-+    if (v8_prebuilt_mksnapshot != "") {
-+      _mksnapshot_bin = v8_prebuilt_mksnapshot
-+    } else {
-+      _mksnapshot_dir =
-+          get_label_info(":mksnapshot($v8_snapshot_toolchain)", "root_out_dir")
-+      if (v8_win_cross_compile_using_wine) {
-+        _mksnapshot_bin = _mksnapshot_dir + "/mksnapshot.exe"
-+      } else {
-+        _mksnapshot_bin = _mksnapshot_dir + "/mksnapshot"
-+      }
-+    }
-+
-+    if (v8_win_cross_compile_using_wine) {
-+      assert(
-+          v8_wine_path != "",
-+          "v8_wine_path must be set when v8_win_cross_compile_using_wine is true")
-+      args += [ v8_wine_path ]
-+    }
-     args += [
--      "./" + rebase_path(get_label_info(":mksnapshot($v8_snapshot_toolchain)",
--                                        "root_out_dir") + "/mksnapshot",
--                         root_build_dir),
-+      "./" + rebase_path(_mksnapshot_bin, root_build_dir),
-       "--turbo_instruction_scheduling",
-       "--turbo-always-optimize-spills",
- 
-diff --git a/gni/snapshot_toolchain.gni b/gni/snapshot_toolchain.gni
-index 37ed262640d048a6fa5923279ae0388c1c0ae766..d9830914f0abd919143f0cf8b3069c5a3f70516e 100644
---- a/gni/snapshot_toolchain.gni
-+++ b/gni/snapshot_toolchain.gni
-@@ -32,6 +32,21 @@ declare_args() {
-   # toolchain that matches the bit-width of the target CPU, but runs on
-   # the host.
-   v8_snapshot_toolchain = ""
-+
-+  # When cross-compiling for Windows on a non-Windows host, build mksnapshot
-+  # as a Windows .exe and run it via Wine instead of building a host-native
-+  # mksnapshot with cross-compile patches.
-+  v8_win_cross_compile_using_wine = false
-+
-+  # Absolute path to the wine64 binary. Required when
-+  # v8_win_cross_compile_using_wine is true.
-+  v8_wine_path = ""
-+
-+  # Path to a pre-built mksnapshot binary to use instead of building one from
-+  # source. When set, run_mksnapshot will use this binary directly and skip
-+  # building the mksnapshot target. The path should be absolute or relative
-+  # to the source root.
-+  v8_prebuilt_mksnapshot = ""
- }
- 
- # Try to infer the appropriate snapshot toolchain for the v8_current_cpu
-@@ -69,7 +84,12 @@ if (v8_snapshot_toolchain == "") {
-     # Cross-build from same ISA on one OS to another. For example:
-     # * targeting win/x64 on a linux/x64 host
-     # * targeting win/arm64 on a mac/arm64 host
--    v8_snapshot_toolchain = host_toolchain
-+    if (v8_win_cross_compile_using_wine && is_win && host_os != "win") {
-+      # Build mksnapshot as a Windows .exe and run it via Wine.
-+      v8_snapshot_toolchain = current_toolchain
-+    } else {
-+      v8_snapshot_toolchain = host_toolchain
-+    }
-   } else if (host_cpu == "arm64" && current_cpu == "x64") {
-     # Cross-build from arm64 to intel (likely on an Apple Silicon mac).
-     v8_snapshot_toolchain =
-@@ -119,7 +139,13 @@ assert(v8_snapshot_toolchain != "",
- # We reuse the snapshot toolchain for building torque and other generators to
- # avoid building v8_libbase on the host more than once. On mips with big endian,
- # the snapshot toolchain is the target toolchain and, hence, can't be used.
--v8_generator_toolchain = v8_snapshot_toolchain
-+# When using Wine for cross-compilation, mksnapshot is built as a Windows .exe
-+# but other generators (torque, etc.) must still be host-native binaries.
-+if (v8_win_cross_compile_using_wine && is_win && host_os != "win") {
-+  v8_generator_toolchain = host_toolchain
-+} else {
-+  v8_generator_toolchain = v8_snapshot_toolchain
-+}
- if (host_cpu == "x64" && v8_current_cpu == "mips64") {
-   v8_generator_toolchain = "//build/toolchain/linux:clang_x64"
- }

patches/v8/fix_derive_v8_control_flow_integrity_from_target_os_not.patch

@@ -0,0 +1,58 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Sam Attard <sattard@anthropic.com>
+Date: Wed, 8 Apr 2026 05:07:17 +0000
+Subject: fix: derive v8_control_flow_integrity from target_os, not
+ arm_control_flow_integrity
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+arm_control_flow_integrity is set in //build/config/arm.gni based on
+is_linux/is_android (i.e. current_os). v8_control_flow_integrity then
+uses 'arm_control_flow_integrity != none' to decide whether the
+macro-assembler should emit pacibsp/autibsp/bti into generated code.
+
+That breaks when the snapshot toolchain's current_os differs from the
+real target — e.g. building win-arm64 on Linux, where mksnapshot is
+//build/toolchain/linux:clang_x64_v8_arm64 (current_os=linux,
+target_os=win). The snapshot toolchain sees arm_control_flow_integrity=
+standard and bakes PAC into the embedded builtins, while the win-arm64
+runtime is built with v8_control_flow_integrity=false. The runtime's
+PointerAuthentication helpers are then no-ops, a PAC-signed LR flows
+through unstripped, and the next autibsp in a code-range-copied builtin
+fast-fails with FAST_FAIL_POINTER_AUTH_INVALID_RETURN_ADDRESS.
+
+Key the non-simulator clause on target_os directly (the same OSes
+arm.gni would enable CFI for), which is global and therefore identical
+in every toolchain. No behaviour change for native Linux/Android arm64,
+mac, or native Windows-hosted win-arm64.
+
+diff --git a/BUILD.gn b/BUILD.gn
+index bf8793c24a1146d39692ef7103a9c54b8d61d509..184b43f74dc6fa3212c0915cecf5b832a34179eb 100644
+--- a/BUILD.gn
++++ b/BUILD.gn
+@@ -345,9 +345,21 @@ declare_args() {
+   # ARM64. Enable it by default for simulator builds and when native code
+   # supports it as well. On Mac, control-flow integrity does not work so we
+   # avoid enabling it when using the simulator.
+-  v8_control_flow_integrity = v8_current_cpu == "arm64" &&
+-                              ((v8_target_is_simulator && target_os != "mac") ||
+-                               arm_control_flow_integrity != "none")
++  #
++  # The non-simulator clause checks target_os directly rather than
++  # arm_control_flow_integrity (which is keyed on current_os via is_linux /
++  # is_android in //build/config/arm.gni). This keeps the value consistent
++  # between the target toolchain and the snapshot toolchain when
++  # cross-compiling — e.g. building win-arm64 on a Linux host where the
++  # snapshot toolchain (//build/toolchain/linux:clang_x64_v8_arm64) has
++  # current_os == "linux" but target_os == "win". Otherwise mksnapshot bakes
++  # pacibsp/autibsp into the embedded builtins while the runtime is built
++  # without V8_ENABLE_CONTROL_FLOW_INTEGRITY, and the resulting binary
++  # fast-fails with FAST_FAIL_POINTER_AUTH_INVALID_RETURN_ADDRESS.
++  v8_control_flow_integrity =
++      v8_current_cpu == "arm64" &&
++      ((v8_target_is_simulator && target_os != "mac") ||
++       target_os == "android" || target_os == "linux")
+ 
+   # Enable heap reservation of size 4GB. Only possible for 64bit archs.
+   cppgc_enable_caged_heap =

patches/v8/fix_emit_win64_pdata_xdata_for_embedded_builtins_when.patch

@@ -0,0 +1,815 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Sam Attard <sattard@anthropic.com>
+Date: Wed, 8 Apr 2026 00:46:31 +0000
+Subject: fix: emit Win64 .pdata/.xdata for embedded builtins when
+ cross-compiling
+
+V8's embedded-builtins unwind-info path (XdataEncoder in the assembler,
+SetBuiltinUnwindData on Isolate, EmitUnwindData in the embedded file
+writer) is gated on V8_OS_WIN64, which derives from the *host* V8_OS_WIN
+set by v8config.h. When mksnapshot is built for a non-Windows host while
+targeting Windows, V8_OS_WIN is undefined, so the entire generation path
+is compiled out and embedded.S contains no .pdata/.xdata for the
+builtins blob. The resulting electron.exe has no RUNTIME_FUNCTION
+records for V8 builtins, so Crashpad/ETW stack walks through builtins
+truncate.
+
+Introduce V8_TARGET_OS_WIN64/_X64/_ARM64 keyed on V8_TARGET_OS_WIN, and
+re-gate only the *generation* half (assembler hooks, BuiltinUnwindInfo
+collection, GetUnwindInfoForBuiltinFunctions, the embedded-file-writer
+emit path, BUILD.gn source inclusion) on the target macros. Leave the
+*runtime registration* half (RtlAddFunctionTable, the
+CrashForExceptionInNonABICompliantCodeRange handler body,
+RegisterNonABICompliantCodeRange, CodeRangeUnwindingRecord) on the host
+V8_OS_WIN64, since that code needs <windows.h> and runs in the target
+process. Define UNW_FLAG_EHANDLER locally so V8UnwindData compiles
+without <winnt.h>.
+
+Also fix two further host-vs-target mismatches that affect codegen when
+mksnapshot runs on a non-Windows host:
+- ia32 MacroAssembler::AllocateStackSpace was V8_OS_WIN-gated, so the
+  Windows guard-page stack-probing loop was dropped from win-x86
+  builtins. The x64 and arm64 equivalents already use V8_TARGET_OS_WIN.
+- arm64 MacroAssembler::Printf's varargs ABI selection (float varargs in
+  x0-x7 on Windows-arm64) was V8_OS_WIN-gated.
+
+On a native Windows build both macro families are defined and behaviour
+is unchanged.
+
+diff --git a/BUILD.gn b/BUILD.gn
+index 751265ba83c04f0c545248a71b35e46034bfc90a..bf8793c24a1146d39692ef7103a9c54b8d61d509 100644
+--- a/BUILD.gn
++++ b/BUILD.gn
+@@ -5033,7 +5033,7 @@ v8_header_set("v8_internal_headers") {
+       "third_party/valgrind/valgrind.h",
+     ]
+ 
+-    if (is_win) {
++    if (is_win || target_os == "win") {
+       sources += [ "src/diagnostics/unwinding-info-win64.h" ]
+     }
+ 
+@@ -5126,7 +5126,7 @@ v8_header_set("v8_internal_headers") {
+         sources += [ "src/trap-handler/trap-handler-simulator.h" ]
+       }
+     }
+-    if (is_win) {
++    if (is_win || target_os == "win") {
+       sources += [ "src/diagnostics/unwinding-info-win64.h" ]
+     }
+   } else if (v8_current_cpu == "mips64" || v8_current_cpu == "mips64el") {
+@@ -6531,7 +6531,7 @@ v8_cluster_source_set("v8_base_without_compiler") {
+       "src/regexp/x64/regexp-macro-assembler-x64.cc",
+     ]
+ 
+-    if (is_win) {
++    if (is_win || target_os == "win") {
+       sources += [ "src/diagnostics/unwinding-info-win64.cc" ]
+     }
+ 
+@@ -6607,7 +6607,7 @@ v8_cluster_source_set("v8_base_without_compiler") {
+         sources += [ "src/trap-handler/handler-outside-simulator.cc" ]
+       }
+     }
+-    if (is_win) {
++    if (is_win || target_os == "win") {
+       sources += [ "src/diagnostics/unwinding-info-win64.cc" ]
+     }
+   } else if (v8_current_cpu == "mips64" || v8_current_cpu == "mips64el") {
+diff --git a/src/builtins/arm64/builtins-arm64.cc b/src/builtins/arm64/builtins-arm64.cc
+index f3c787d701fd1f9421220717cec1228ffc049a80..4d36d1b931634d07eb2d4f71f3a7380ea5016978 100644
+--- a/src/builtins/arm64/builtins-arm64.cc
++++ b/src/builtins/arm64/builtins-arm64.cc
+@@ -39,9 +39,9 @@
+ #include "src/wasm/wasm-objects.h"
+ #endif  // V8_ENABLE_WEBASSEMBLY
+ 
+-#if defined(V8_OS_WIN)
++#if defined(V8_TARGET_OS_WIN)
+ #include "src/diagnostics/unwinding-info-win64.h"
+-#endif  // V8_OS_WIN
++#endif  // V8_TARGET_OS_WIN
+ 
+ namespace v8 {
+ namespace internal {
+@@ -642,7 +642,7 @@ void Generate_JSEntryVariant(MacroAssembler* masm, StackFrame::Type type,
+   {
+     NoRootArrayScope no_root_array(masm);
+ 
+-#if defined(V8_OS_WIN)
++#if defined(V8_TARGET_OS_WIN)
+     // In order to allow Windows debugging tools to reconstruct a call stack, we
+     // must generate information describing how to recover at least fp, sp, and
+     // pc for the calling frame. Here, JSEntry registers offsets to
+diff --git a/src/builtins/setup-builtins-internal.cc b/src/builtins/setup-builtins-internal.cc
+index e8f8a1138ea4de84f4348d12531b0b6042b19533..6c399eddacc36f39a7f7e8ab78feeb4a97b16d08 100644
+--- a/src/builtins/setup-builtins-internal.cc
++++ b/src/builtins/setup-builtins-internal.cc
+@@ -227,9 +227,9 @@ V8_NOINLINE Tagged<Code> BuildWithMacroAssembler(
+           .set_self_reference(masm.CodeObject())
+           .set_builtin(builtin)
+           .Build();
+-#if defined(V8_OS_WIN64)
++#if defined(V8_TARGET_OS_WIN64)
+   isolate->SetBuiltinUnwindData(builtin, masm.GetUnwindInfo());
+-#endif  // V8_OS_WIN64
++#endif  // V8_TARGET_OS_WIN64
+   return *code;
+ }
+ 
+diff --git a/src/codegen/arm64/assembler-arm64.cc b/src/codegen/arm64/assembler-arm64.cc
+index 40adf1773e658e5bfe5f40f503421a3320c49f7b..1583d4de4ca8b3968834401a8148367d12fdccd5 100644
+--- a/src/codegen/arm64/assembler-arm64.cc
++++ b/src/codegen/arm64/assembler-arm64.cc
+@@ -421,7 +421,7 @@ Assembler::Assembler(const MaybeAssemblerZone& zone,
+       constpool_(this) {
+   Reset();
+ 
+-#if defined(V8_OS_WIN)
++#if defined(V8_TARGET_OS_WIN)
+   if (options.collect_win64_unwind_info) {
+     xdata_encoder_ = std::make_unique<win64_unwindinfo::XdataEncoder>(*this);
+   }
+@@ -449,7 +449,7 @@ void Assembler::Reset() {
+   next_veneer_pool_check_ = kMaxInt;
+ }
+ 
+-#if defined(V8_OS_WIN)
++#if defined(V8_TARGET_OS_WIN)
+ win64_unwindinfo::BuiltinUnwindInfo Assembler::GetUnwindInfo() const {
+   DCHECK(options().collect_win64_unwind_info);
+   DCHECK_NOT_NULL(xdata_encoder_);
+@@ -1433,7 +1433,7 @@ void Assembler::stp(const CPURegister& rt, const CPURegister& rt2,
+                     const MemOperand& dst) {
+   LoadStorePair(rt, rt2, dst, StorePairOpFor(rt, rt2));
+ 
+-#if defined(V8_OS_WIN)
++#if defined(V8_TARGET_OS_WIN)
+   if (xdata_encoder_ && rt == x29 && rt2 == lr && dst.base().IsSP()) {
+     xdata_encoder_->onSaveFpLr();
+   }
+diff --git a/src/codegen/arm64/assembler-arm64.h b/src/codegen/arm64/assembler-arm64.h
+index a642a62f96a9748782b691a92ee5aecfe3d75b32..a3234c51322b8e3d620f996cb570333a7e6efa1e 100644
+--- a/src/codegen/arm64/assembler-arm64.h
++++ b/src/codegen/arm64/assembler-arm64.h
+@@ -27,9 +27,9 @@
+ #undef mvn
+ #endif
+ 
+-#if defined(V8_OS_WIN)
++#if defined(V8_TARGET_OS_WIN)
+ #include "src/diagnostics/unwinding-info-win64.h"
+-#endif  // V8_OS_WIN
++#endif  // V8_TARGET_OS_WIN
+ 
+ namespace v8 {
+ namespace internal {
+@@ -3200,7 +3200,7 @@ class V8_EXPORT_PRIVATE Assembler : public AssemblerBase {
+     DISALLOW_IMPLICIT_CONSTRUCTORS(BlockPoolsScope);
+   };
+ 
+-#if defined(V8_OS_WIN)
++#if defined(V8_TARGET_OS_WIN)
+   win64_unwindinfo::XdataEncoder* GetXdataEncoder() {
+     return xdata_encoder_.get();
+   }
+@@ -3531,7 +3531,7 @@ class V8_EXPORT_PRIVATE Assembler : public AssemblerBase {
+   // enabled.
+   JumpTableInfoWriter jump_table_info_writer_;
+ 
+-#if defined(V8_OS_WIN)
++#if defined(V8_TARGET_OS_WIN)
+   std::unique_ptr<win64_unwindinfo::XdataEncoder> xdata_encoder_;
+ #endif
+ 
+diff --git a/src/codegen/arm64/macro-assembler-arm64.cc b/src/codegen/arm64/macro-assembler-arm64.cc
+index a20c06e326c13d2965b217718c0df0c45784b286..f8e022fb66e42855cc33d8e4de07393025533a92 100644
+--- a/src/codegen/arm64/macro-assembler-arm64.cc
++++ b/src/codegen/arm64/macro-assembler-arm64.cc
+@@ -4552,7 +4552,7 @@ void MacroAssembler::PrintfNoPreserve(const char* format,
+ 
+   // Copies of the printf vararg registers that we can pop from.
+   CPURegList pcs_varargs = kPCSVarargs;
+-#ifndef V8_OS_WIN
++#ifndef V8_TARGET_OS_WIN
+   CPURegList pcs_varargs_fp = kPCSVarargsFP;
+ #endif
+ 
+@@ -4569,7 +4569,7 @@ void MacroAssembler::PrintfNoPreserve(const char* format,
+       if (args[i].Is32Bits()) pcs[i] = pcs[i].W();
+     } else if (args[i].IsVRegister()) {
+       // In C, floats are always cast to doubles for varargs calls.
+-#ifdef V8_OS_WIN
++#ifdef V8_TARGET_OS_WIN
+       // In case of variadic functions SIMD and Floating-point registers
+       // aren't used. The general x0-x7 should be used instead.
+       // https://docs.microsoft.com/en-us/cpp/build/arm64-windows-abi-conventions
+@@ -4607,7 +4607,7 @@ void MacroAssembler::PrintfNoPreserve(const char* format,
+   // Do a second pass to move values into their final positions and perform any
+   // conversions that may be required.
+   for (int i = 0; i < arg_count; i++) {
+-#ifdef V8_OS_WIN
++#ifdef V8_TARGET_OS_WIN
+     if (args[i].IsVRegister()) {
+       if (pcs[i].SizeInBytes() != args[i].SizeInBytes()) {
+         // If the argument is half- or single-precision
+diff --git a/src/codegen/ia32/macro-assembler-ia32.cc b/src/codegen/ia32/macro-assembler-ia32.cc
+index ce1b803cf691f17cdcf17cc950a87f557b1be3b5..e779ee79503797c4c6556606471e3c2bb6dbac7b 100644
+--- a/src/codegen/ia32/macro-assembler-ia32.cc
++++ b/src/codegen/ia32/macro-assembler-ia32.cc
+@@ -1076,7 +1076,7 @@ void MacroAssembler::LeaveFrame(StackFrame::Type type) {
+   leave();
+ }
+ 
+-#ifdef V8_OS_WIN
++#ifdef V8_TARGET_OS_WIN
+ void MacroAssembler::AllocateStackSpace(Register bytes_scratch) {
+   ASM_CODE_COMMENT(this);
+   // In windows, we cannot increment the stack size by more than one page
+diff --git a/src/codegen/ia32/macro-assembler-ia32.h b/src/codegen/ia32/macro-assembler-ia32.h
+index 77333472ebf6dbf4ee2b1f44466ce2110c9e97cd..992391f5138cfb8471f4100ee8be761331462737 100644
+--- a/src/codegen/ia32/macro-assembler-ia32.h
++++ b/src/codegen/ia32/macro-assembler-ia32.h
+@@ -96,7 +96,7 @@ class V8_EXPORT_PRIVATE MacroAssembler
+ // stack check, do it before calling this function because this function may
+ // write into the newly allocated space. It may also overwrite the given
+ // register's value, in the version that takes a register.
+-#ifdef V8_OS_WIN
++#ifdef V8_TARGET_OS_WIN
+   void AllocateStackSpace(Register bytes_scratch);
+   void AllocateStackSpace(int bytes);
+ #else
+diff --git a/src/codegen/x64/assembler-x64.cc b/src/codegen/x64/assembler-x64.cc
+index 6edc61b4d52f8d4e9019c4057b5a5d4b8ea7b4fe..13fd6d119486a56783a5673867cf09692929834e 100644
+--- a/src/codegen/x64/assembler-x64.cc
++++ b/src/codegen/x64/assembler-x64.cc
+@@ -446,7 +446,7 @@ Assembler::Assembler(const AssemblerOptions& options,
+     EnableCpuFeature(SSE3);
+   }
+ 
+-#if defined(V8_OS_WIN_X64)
++#if defined(V8_TARGET_OS_WIN_X64)
+   if (options.collect_win64_unwind_info) {
+     xdata_encoder_ = std::make_unique<win64_unwindinfo::XdataEncoder>(*this);
+   }
+@@ -532,7 +532,7 @@ void Assembler::FinalizeJumpOptimizationInfo() {
+   }
+ }
+ 
+-#if defined(V8_OS_WIN_X64)
++#if defined(V8_TARGET_OS_WIN_X64)
+ win64_unwindinfo::BuiltinUnwindInfo Assembler::GetUnwindInfo() const {
+   DCHECK(options().collect_win64_unwind_info);
+   DCHECK_NOT_NULL(xdata_encoder_);
+@@ -1991,7 +1991,7 @@ void Assembler::emit_mov(Register dst, Register src, int size) {
+   emit(0x8B);
+   emit_modrm(dst, src);
+ 
+-#if defined(V8_OS_WIN_X64)
++#if defined(V8_TARGET_OS_WIN_X64)
+   if (xdata_encoder_ && dst == rbp && src == rsp) {
+     xdata_encoder_->onMovRbpRsp();
+   }
+@@ -2437,7 +2437,7 @@ void Assembler::pushq(Register src) {
+   emit_optional_rex_32(src);
+   emit(0x50 | src.low_bits());
+ 
+-#if defined(V8_OS_WIN_X64)
++#if defined(V8_TARGET_OS_WIN_X64)
+   if (xdata_encoder_ && src == rbp) {
+     xdata_encoder_->onPushRbp();
+   }
+@@ -4920,7 +4920,7 @@ void Assembler::pushpq(Register src) {
+   EnsureSpace ensure_space(this);
+   emit_rex2_64(src, kRex2Map0);
+   emit(0x50 | src.low_bits());
+-#if defined(V8_OS_WIN_X64)
++#if defined(V8_TARGET_OS_WIN_X64)
+   if (xdata_encoder_ && src == rbp) {
+     xdata_encoder_->onPushRbp();
+   }
+@@ -4935,7 +4935,7 @@ void Assembler::push2q(Register src1, Register src2) {
+                                    kW0, kFlagUpdate, kNewDataDest);
+   emit(0xFF);
+   emit_modrm(6, src2);
+-#if defined(V8_OS_WIN_X64)
++#if defined(V8_TARGET_OS_WIN_X64)
+   if (xdata_encoder_ && src1 == rbp) {
+     xdata_encoder_->onPushRbp();
+   }
+@@ -4953,7 +4953,7 @@ void Assembler::push2pq(Register src1, Register src2) {
+                                    kW1, kFlagUpdate, kNewDataDest);
+   emit(0xFF);
+   emit_modrm(6, src2);
+-#if defined(V8_OS_WIN_X64)
++#if defined(V8_TARGET_OS_WIN_X64)
+   if (xdata_encoder_ && src1 == rbp) {
+     xdata_encoder_->onPushRbp();
+   }
+diff --git a/src/codegen/x64/assembler-x64.h b/src/codegen/x64/assembler-x64.h
+index a4aaae402920d90e961e163cf87af5c564c28a78..51098680c01df93dca361816020eb9fb6cf5c211 100644
+--- a/src/codegen/x64/assembler-x64.h
++++ b/src/codegen/x64/assembler-x64.h
+@@ -53,7 +53,7 @@
+ #include "src/codegen/x64/sse-instr.h"
+ #include "src/objects/smi.h"
+ 
+-#if defined(V8_OS_WIN_X64)
++#if defined(V8_TARGET_OS_WIN_X64)
+ #include "src/diagnostics/unwinding-info-win64.h"
+ #endif
+ 
+@@ -2687,7 +2687,7 @@ class V8_EXPORT_PRIVATE Assembler : public AssemblerBase {
+   uint8_t byte_at(int pos) { return buffer_start_[pos]; }
+   void set_byte_at(int pos, uint8_t value) { buffer_start_[pos] = value; }
+ 
+-#if defined(V8_OS_WIN_X64)
++#if defined(V8_TARGET_OS_WIN_X64)
+   win64_unwindinfo::BuiltinUnwindInfo GetUnwindInfo() const;
+ #endif
+ 
+@@ -3557,7 +3557,7 @@ class V8_EXPORT_PRIVATE Assembler : public AssemblerBase {
+ 
+   JumpTableInfoWriter builtin_jump_table_info_writer_;
+ 
+-#if defined(V8_OS_WIN_X64)
++#if defined(V8_TARGET_OS_WIN_X64)
+   std::unique_ptr<win64_unwindinfo::XdataEncoder> xdata_encoder_;
+ #endif
+ };
+diff --git a/src/common/globals.h b/src/common/globals.h
+index d5885006fca0b8fb78c71f833e054e18ba934731..fa4bf10799662137d876d5c4d870882638306658 100644
+--- a/src/common/globals.h
++++ b/src/common/globals.h
+@@ -340,6 +340,22 @@ const size_t kShortBuiltinCallsOldSpaceSizeThreshold = size_t{2} * GB;
+ #define V8_OS_WIN64 true
+ #endif
+ 
++// Like V8_OS_WIN_X64/ARM64/64 above, but keyed on the *target* OS rather than
++// the host. mksnapshot uses these to decide whether to collect and emit
++// Windows .pdata/.xdata for the embedded builtins blob when cross-compiling
++// for Windows on a non-Windows host (where V8_OS_WIN64 is undefined).
++#if defined(V8_TARGET_OS_WIN) && defined(V8_TARGET_ARCH_X64)
++#define V8_TARGET_OS_WIN_X64 true
++#endif
++
++#if defined(V8_TARGET_OS_WIN) && defined(V8_TARGET_ARCH_ARM64)
++#define V8_TARGET_OS_WIN_ARM64 true
++#endif
++
++#if defined(V8_TARGET_OS_WIN_X64) || defined(V8_TARGET_OS_WIN_ARM64)
++#define V8_TARGET_OS_WIN64 true
++#endif
++
+ // Support for floating point parameters in calls to C.
+ // It's currently enabled only for the platforms listed below. We don't plan
+ // to add support for IA32, because it has a totally different approach
+diff --git a/src/diagnostics/unwinding-info-win64.cc b/src/diagnostics/unwinding-info-win64.cc
+index 1312609e5b648fdca187373c374126282c7afa77..3655b3b344aa9d978c93ff4568cd8a2260014853 100644
+--- a/src/diagnostics/unwinding-info-win64.cc
++++ b/src/diagnostics/unwinding-info-win64.cc
+@@ -7,19 +7,28 @@
+ #include "src/codegen/macro-assembler.h"
+ #include "src/utils/allocation.h"
+ 
+-#if defined(V8_OS_WIN_X64)
++#if defined(V8_TARGET_OS_WIN_X64)
+ #include "src/codegen/x64/assembler-x64.h"
+-#elif defined(V8_OS_WIN_ARM64)
++#elif defined(V8_TARGET_OS_WIN_ARM64)
+ #include "src/codegen/arm64/assembler-arm64-inl.h"
+ #include "src/codegen/arm64/macro-assembler-arm64-inl.h"
+ #else
+ #error "Unsupported OS"
+-#endif  // V8_OS_WIN_X64
++#endif  // V8_TARGET_OS_WIN_X64
+ 
++#if defined(V8_OS_WIN64)
+ #include <windows.h>
+ 
+ // This has to come after windows.h.
+ #include <versionhelpers.h>  // For IsWindows8OrGreater().
++#endif                       // V8_OS_WIN64
++
++// UNW_FLAG_EHANDLER is normally provided by <winnt.h>; define it locally so
++// the xdata structs below also compile in mksnapshot when cross-compiling on
++// a non-Windows host.
++#ifndef UNW_FLAG_EHANDLER
++#define UNW_FLAG_EHANDLER 0x01
++#endif
+ 
+ namespace v8 {
+ namespace internal {
+@@ -27,6 +36,8 @@ namespace win64_unwindinfo {
+ 
+ bool CanEmitUnwindInfoForBuiltins() { return v8_flags.win64_unwinding_info; }
+ 
++#if defined(V8_OS_WIN64)
++
+ bool CanRegisterUnwindInfoForNonABICompliantCodeRange() {
+   return !v8_flags.jitless;
+ }
+@@ -61,7 +72,9 @@ extern "C" __declspec(dllexport) int CRASH_HANDLER_FUNCTION_NAME(
+   return ExceptionContinueSearch;
+ }
+ 
+-#if defined(V8_OS_WIN_X64)
++#endif  // V8_OS_WIN64
++
++#if defined(V8_TARGET_OS_WIN_X64)
+ 
+ #pragma pack(push, 1)
+ 
+@@ -88,7 +101,6 @@ struct UNWIND_INFO {
+ };
+ 
+ static constexpr int kNumberOfUnwindCodes = 2;
+-static constexpr int kMaxExceptionThunkSize = 12;
+ 
+ struct V8UnwindData {
+   UNWIND_INFO unwind_info;
+@@ -115,6 +127,10 @@ struct V8UnwindData {
+   }
+ };
+ 
++#if defined(V8_OS_WIN64)
++
++static constexpr int kMaxExceptionThunkSize = 12;
++
+ struct ExceptionHandlerUnwindData {
+   UNWIND_INFO unwind_info;
+ 
+@@ -145,6 +161,8 @@ struct ExceptionHandlerRecord {
+   uint8_t exception_thunk[kMaxExceptionThunkSize];
+ };
+ 
++#endif  // V8_OS_WIN64
++
+ #pragma pack(pop)
+ 
+ std::vector<uint8_t> GetUnwindInfoForBuiltinFunctions() {
+@@ -154,6 +172,8 @@ std::vector<uint8_t> GetUnwindInfoForBuiltinFunctions() {
+       reinterpret_cast<uint8_t*>(&xdata) + sizeof(xdata));
+ }
+ 
++#if defined(V8_OS_WIN64)
++
+ template <typename Record>
+ void InitUnwindingRecord(Record* record, size_t code_size_in_bytes) {
+   // We assume that the first page of the code range is executable and
+@@ -180,7 +200,9 @@ void InitUnwindingRecord(Record* record, size_t code_size_in_bytes) {
+          masm.instruction_size());
+ }
+ 
+-#elif defined(V8_OS_WIN_ARM64)
++#endif  // V8_OS_WIN64
++
++#elif defined(V8_TARGET_OS_WIN_ARM64)
+ 
+ #pragma pack(push, 1)
+ 
+@@ -220,7 +242,6 @@ struct UNWIND_INFO {
+ };
+ 
+ static constexpr int kDefaultNumberOfUnwindCodeWords = 1;
+-static constexpr int kMaxExceptionThunkSize = 16;
+ static constexpr int kFunctionLengthShiftSize = 2;
+ static constexpr int kFunctionLengthMask = (1 << kFunctionLengthShiftSize) - 1;
+ static constexpr int kAllocStackShiftSize = 4;
+@@ -299,6 +320,10 @@ struct V8UnwindData {
+   }
+ };
+ 
++#if defined(V8_OS_WIN64)
++
++static constexpr int kMaxExceptionThunkSize = 16;
++
+ struct CodeRangeUnwindingRecord {
+   void* dynamic_table;
+   uint32_t runtime_function_count;
+@@ -319,6 +344,8 @@ struct CodeRangeUnwindingRecord {
+   RUNTIME_FUNCTION runtime_function[kDefaultRuntimeFunctionCount];
+ };
+ 
++#endif  // V8_OS_WIN64
++
+ #pragma pack(pop)
+ 
+ FrameOffsets::FrameOffsets()
+@@ -383,6 +410,8 @@ std::vector<uint8_t> GetUnwindInfoForBuiltinFunction(
+           &xdata.unwind_codes[xdata.unwind_info.CodeWords]));
+ }
+ 
++#if defined(V8_OS_WIN64)
++
+ template <typename Record>
+ void InitUnwindingRecord(Record* record, size_t code_size_in_bytes) {
+   // We assume that the first page of the code range is executable and
+@@ -459,7 +488,11 @@ void InitUnwindingRecord(Record* record, size_t code_size_in_bytes) {
+          masm.instruction_size());
+ }
+ 
+-#endif  // V8_OS_WIN_X64
++#endif  // V8_OS_WIN64
++
++#endif  // V8_TARGET_OS_WIN_X64
++
++#if defined(V8_OS_WIN64)
+ 
+ namespace {
+ 
+@@ -604,7 +637,9 @@ void UnregisterNonABICompliantCodeRange(void* start) {
+   }
+ }
+ 
+-#if defined(V8_OS_WIN_X64)
++#endif  // V8_OS_WIN64
++
++#if defined(V8_TARGET_OS_WIN_X64)
+ 
+ void XdataEncoder::onPushRbp() {
+   current_frame_code_offset_ =
+@@ -618,7 +653,7 @@ void XdataEncoder::onMovRbpRsp() {
+   }
+ }
+ 
+-#elif defined(V8_OS_WIN_ARM64)
++#elif defined(V8_TARGET_OS_WIN_ARM64)
+ 
+ void XdataEncoder::onSaveFpLr() {
+   current_frame_code_offset_ = assembler_.pc_offset() - 4;
+@@ -633,7 +668,7 @@ void XdataEncoder::onFramePointerAdjustment(int fp_to_saved_caller_fp,
+   current_frame_adjustment_.fp_to_caller_sp = fp_to_caller_sp;
+ }
+ 
+-#endif  // V8_OS_WIN_X64
++#endif  // V8_TARGET_OS_WIN_X64
+ 
+ }  // namespace win64_unwindinfo
+ }  // namespace internal
+diff --git a/src/diagnostics/unwinding-info-win64.h b/src/diagnostics/unwinding-info-win64.h
+index bb32f49e5d8966bafc079d274ad9600f75f85759..54906f76fbe06fef08a4668faee1fc46b5699ff4 100644
+--- a/src/diagnostics/unwinding-info-win64.h
++++ b/src/diagnostics/unwinding-info-win64.h
+@@ -11,8 +11,7 @@
+ #include "include/v8config.h"
+ #include "src/common/globals.h"
+ 
+-#if defined(V8_OS_WIN64)
+-#include "src/base/win32-headers.h"
++#if defined(V8_TARGET_OS_WIN64)
+ 
+ namespace v8 {
+ namespace internal {
+@@ -32,6 +31,7 @@ static const int kOSPageSize = 4096;
+  */
+ bool CanEmitUnwindInfoForBuiltins();
+ 
++#if defined(V8_OS_WIN64)
+ /**
+  * Returns true if V8 if we can register unwinding data for the whole code range
+  * of an isolate or Wasm module. The first page of the code range is reserved
+@@ -50,6 +50,7 @@ void SetUnhandledExceptionCallback(
+ 
+ void RegisterNonABICompliantCodeRange(void* start, size_t size_in_bytes);
+ void UnregisterNonABICompliantCodeRange(void* start);
++#endif  // V8_OS_WIN64
+ 
+ /**
+  * Default count of RUNTIME_FUNCTION needed. For Windows X64, 1 RUNTIME_FUNCTION
+@@ -61,7 +62,7 @@ void UnregisterNonABICompliantCodeRange(void* start);
+  */
+ static const uint32_t kDefaultRuntimeFunctionCount = 1;
+ 
+-#if defined(V8_OS_WIN_X64)
++#if defined(V8_TARGET_OS_WIN_X64)
+ 
+ static const int kPushRbpInstructionLength = 1;
+ static const int kMovRbpRspInstructionLength = 3;
+@@ -107,7 +108,7 @@ class XdataEncoder {
+   int current_frame_code_offset_;
+ };
+ 
+-#elif defined(V8_OS_WIN_ARM64)
++#elif defined(V8_TARGET_OS_WIN_ARM64)
+ 
+ /**
+  * Base on below doc, unwind record has 18 bits (unsigned) to encode function
+@@ -182,6 +183,6 @@ class XdataEncoder {
+ }  // namespace internal
+ }  // namespace v8
+ 
+-#endif  // V8_OS_WIN64
++#endif  // V8_TARGET_OS_WIN64
+ 
+ #endif  // V8_DIAGNOSTICS_UNWINDING_INFO_WIN64_H_
+diff --git a/src/execution/isolate.cc b/src/execution/isolate.cc
+index 6d8c9927b433e9be772065fd6993b5849640ae33..e360ba9d839469c4406be300ed48fbe5955657e5 100644
+--- a/src/execution/isolate.cc
++++ b/src/execution/isolate.cc
+@@ -170,9 +170,9 @@
+ #include "src/diagnostics/etw-jit-win.h"
+ #endif  // V8_ENABLE_ETW_STACK_WALKING
+ 
+-#if defined(V8_OS_WIN64)
++#if defined(V8_TARGET_OS_WIN64)
+ #include "src/diagnostics/unwinding-info-win64.h"
+-#endif  // V8_OS_WIN64
++#endif  // V8_TARGET_OS_WIN64
+ 
+ #if USE_SIMULATOR
+ #include "src/execution/simulator-base.h"
+@@ -7276,7 +7276,7 @@ void Isolate::PrepareBuiltinSourcePositionMap() {
+   }
+ }
+ 
+-#if defined(V8_OS_WIN64)
++#if defined(V8_TARGET_OS_WIN64)
+ void Isolate::SetBuiltinUnwindData(
+     Builtin builtin,
+     const win64_unwindinfo::BuiltinUnwindInfo& unwinding_info) {
+@@ -7284,7 +7284,7 @@ void Isolate::SetBuiltinUnwindData(
+     embedded_file_writer_->SetBuiltinUnwindData(builtin, unwinding_info);
+   }
+ }
+-#endif  // V8_OS_WIN64
++#endif  // V8_TARGET_OS_WIN64
+ 
+ void Isolate::SetPrepareStackTraceCallback(PrepareStackTraceCallback callback) {
+   prepare_stack_trace_callback_ = callback;
+diff --git a/src/execution/isolate.h b/src/execution/isolate.h
+index e11bb4083042e2b6fd4101eed0f0d06cae1b0ef1..6b02e13d4e5acceb976676b0dd0eb090e1e08ab5 100644
+--- a/src/execution/isolate.h
++++ b/src/execution/isolate.h
+@@ -190,9 +190,11 @@ class WasmRevecVerifier;
+ }  // namespace turboshaft
+ }  // namespace compiler
+ 
++#if defined(V8_TARGET_OS_WIN64)
+ namespace win64_unwindinfo {
+ class BuiltinUnwindInfo;
+ }  // namespace win64_unwindinfo
++#endif  // V8_TARGET_OS_WIN64
+ 
+ namespace metrics {
+ class Recorder;
+@@ -2033,11 +2035,11 @@ class V8_EXPORT_PRIVATE Isolate final : private HiddenFactory {
+   // annotate the builtin blob with debugging information.
+   void PrepareBuiltinSourcePositionMap();
+ 
+-#if defined(V8_OS_WIN64)
++#if defined(V8_TARGET_OS_WIN64)
+   void SetBuiltinUnwindData(
+       Builtin builtin,
+       const win64_unwindinfo::BuiltinUnwindInfo& unwinding_info);
+-#endif  // V8_OS_WIN64
++#endif  // V8_TARGET_OS_WIN64
+ 
+   void SetPrepareStackTraceCallback(PrepareStackTraceCallback callback);
+   MaybeDirectHandle<Object> RunPrepareStackTraceCallback(
+diff --git a/src/snapshot/embedded/embedded-file-writer-interface.h b/src/snapshot/embedded/embedded-file-writer-interface.h
+index 3d43baad83ceef8c03384473522c7c8ddb904081..fec1b47b96c9a68a4e2986f2f00a7d7288036c65 100644
+--- a/src/snapshot/embedded/embedded-file-writer-interface.h
++++ b/src/snapshot/embedded/embedded-file-writer-interface.h
+@@ -14,11 +14,11 @@ namespace internal {
+ 
+ class Builtins;
+ 
+-#if defined(V8_OS_WIN64)
++#if defined(V8_TARGET_OS_WIN64)
+ namespace win64_unwindinfo {
+ class BuiltinUnwindInfo;
+ }
+-#endif  // V8_OS_WIN64
++#endif  // V8_TARGET_OS_WIN64
+ 
+ static constexpr char kDefaultEmbeddedVariant[] = "Default";
+ 
+@@ -40,11 +40,11 @@ class EmbeddedFileWriterInterface {
+   // compiled builtin InstructionStream objects with trampolines.
+   virtual void PrepareBuiltinSourcePositionMap(Builtins* builtins) = 0;
+ 
+-#if defined(V8_OS_WIN64)
++#if defined(V8_TARGET_OS_WIN64)
+   virtual void SetBuiltinUnwindData(
+       Builtin builtin,
+       const win64_unwindinfo::BuiltinUnwindInfo& unwinding_info) = 0;
+-#endif  // V8_OS_WIN64
++#endif  // V8_TARGET_OS_WIN64
+ };
+ 
+ }  // namespace internal
+diff --git a/src/snapshot/embedded/embedded-file-writer.cc b/src/snapshot/embedded/embedded-file-writer.cc
+index 21a5abd275097bac4221686641b962a8c57c4a46..f93ab3c058ebfb3f886bd4a9ff45019971f5c856 100644
+--- a/src/snapshot/embedded/embedded-file-writer.cc
++++ b/src/snapshot/embedded/embedded-file-writer.cc
+@@ -193,7 +193,7 @@ void EmbeddedFileWriter::WriteFileEpilogue(PlatformEmbeddedFileWriterBase* w,
+     w->Newline();
+   }
+ 
+-#if defined(V8_OS_WIN64)
++#if defined(V8_TARGET_OS_WIN64)
+   {
+     base::EmbeddedVector<char, kTemporaryStringLength> unwind_info_symbol;
+     base::SNPrintF(unwind_info_symbol, "%s_Builtins_UnwindInfo",
+@@ -203,7 +203,7 @@ void EmbeddedFileWriter::WriteFileEpilogue(PlatformEmbeddedFileWriterBase* w,
+                            EmbeddedBlobCodeSymbol().c_str(), blob,
+                            reinterpret_cast<const void*>(&unwind_infos_[0]));
+   }
+-#endif  // V8_OS_WIN64
++#endif  // V8_TARGET_OS_WIN64
+ 
+   w->FileEpilogue();
+ }
+diff --git a/src/snapshot/embedded/embedded-file-writer.h b/src/snapshot/embedded/embedded-file-writer.h
+index 40f22006041d930fedd133e03359b00c0fecff47..9cc61310aef9c7f9b722fd84a26e4c08c86fde44 100644
+--- a/src/snapshot/embedded/embedded-file-writer.h
++++ b/src/snapshot/embedded/embedded-file-writer.h
+@@ -17,9 +17,9 @@
+ #include "src/snapshot/embedded/embedded-file-writer-interface.h"
+ #include "src/snapshot/embedded/platform-embedded-file-writer-base.h"
+ 
+-#if defined(V8_OS_WIN64)
++#if defined(V8_TARGET_OS_WIN64)
+ #include "src/diagnostics/unwinding-info-win64.h"
+-#endif  // V8_OS_WIN64
++#endif  // V8_TARGET_OS_WIN64
+ 
+ namespace v8 {
+ namespace internal {
+@@ -40,14 +40,14 @@ class EmbeddedFileWriter : public EmbeddedFileWriterInterface {
+ 
+   void PrepareBuiltinSourcePositionMap(Builtins* builtins) override;
+ 
+-#if defined(V8_OS_WIN64)
++#if defined(V8_TARGET_OS_WIN64)
+   void SetBuiltinUnwindData(
+       Builtin builtin,
+       const win64_unwindinfo::BuiltinUnwindInfo& unwinding_info) override {
+     DCHECK_LT(static_cast<int>(builtin), Builtins::kBuiltinCount);
+     unwind_infos_[static_cast<int>(builtin)] = unwinding_info;
+   }
+-#endif  // V8_OS_WIN64
++#endif  // V8_TARGET_OS_WIN64
+ 
+   void SetEmbeddedFile(const char* embedded_src_path) {
+     embedded_src_path_ = embedded_src_path;
+@@ -186,9 +186,9 @@ class EmbeddedFileWriter : public EmbeddedFileWriterInterface {
+   std::vector<uint8_t> source_positions_[Builtins::kBuiltinCount];
+   std::vector<LabelInfo> label_info_[Builtins::kBuiltinCount];
+ 
+-#if defined(V8_OS_WIN64)
++#if defined(V8_TARGET_OS_WIN64)
+   win64_unwindinfo::BuiltinUnwindInfo unwind_infos_[Builtins::kBuiltinCount];
+-#endif  // V8_OS_WIN64
++#endif  // V8_TARGET_OS_WIN64
+ 
+   std::map<const char*, int> external_filenames_;
+   std::vector<const char*> external_filenames_by_index_;
+diff --git a/src/snapshot/embedded/platform-embedded-file-writer-win.cc b/src/snapshot/embedded/platform-embedded-file-writer-win.cc
+index bf76435717cf63f6f7be288c9b7e963c14b29425..b2319b9fea8b8ba8189ab577cbcf6982c3733bc0 100644
+--- a/src/snapshot/embedded/platform-embedded-file-writer-win.cc
++++ b/src/snapshot/embedded/platform-embedded-file-writer-win.cc
+@@ -8,7 +8,7 @@
+ 
+ #include "src/common/globals.h"  // For V8_OS_WIN64
+ 
+-#if defined(V8_OS_WIN64)
++#if defined(V8_TARGET_OS_WIN64)
+ #include "src/builtins/builtins.h"
+ #include "src/diagnostics/unwinding-info-win64.h"
+ #include "src/snapshot/embedded/embedded-data-inl.h"
+@@ -59,7 +59,7 @@ namespace internal {
+ 
+ namespace {
+ 
+-#if defined(V8_OS_WIN_X64)
++#if defined(V8_TARGET_OS_WIN_X64)
+ 
+ void WriteUnwindInfoEntry(PlatformEmbeddedFileWriterWin* w,
+                           const char* unwind_info_symbol,
+@@ -175,7 +175,7 @@ void EmitUnwindData(PlatformEmbeddedFileWriterWin* w,
+   w->Newline();
+ }
+ 
+-#elif defined(V8_OS_WIN_ARM64)
++#elif defined(V8_TARGET_OS_WIN_ARM64)
+ 
+ void EmitUnwindData(PlatformEmbeddedFileWriterWin* w,
+                     const char* unwind_info_symbol,
+@@ -318,13 +318,13 @@ void PlatformEmbeddedFileWriterWin::MaybeEmitUnwindData(
+     const EmbeddedData* blob, const void* unwind_infos) {
+ // Windows ARM64 supports cross build which could require unwind info for
+ // host_os. Ignore this case because it is only used in build time.
+-#if defined(V8_OS_WIN_ARM64)
++#if defined(V8_TARGET_OS_WIN_ARM64)
+   if (target_arch_ != EmbeddedTargetArch::kArm64) {
+     return;
+   }
+ #endif  // V8_OS_WIN_ARM64
+ 
+-#if defined(V8_OS_WIN64)
++#if defined(V8_TARGET_OS_WIN64)
+   if (win64_unwindinfo::CanEmitUnwindInfoForBuiltins()) {
+     EmitUnwindData(this, unwind_info_symbol, embedded_blob_data_symbol, blob,
+                    reinterpret_cast<const win64_unwindinfo::BuiltinUnwindInfo*>(

patches/v8/fix_use_clang_x64_v8_arm64_snapshot_toolchain_for_win-arm64_on.patch

@@ -0,0 +1,45 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Sam Attard <sattard@anthropic.com>
+Date: Wed, 8 Apr 2026 03:08:36 +0000
+Subject: fix: use clang_x64_v8_arm64 snapshot toolchain for win-arm64 on
+ non-Windows hosts
+
+snapshot_toolchain.gni special-cases is_win && v8_current_cpu == arm64
+to use host_toolchain. is_win is true whenever the *target* is Windows,
+but the special case only makes sense on a Windows host (where there is
+no //build/toolchain/win:clang_x64_v8_arm64). On a Linux host,
+host_toolchain is //build/toolchain/linux:clang_x64 which has
+v8_current_cpu == x64, so mksnapshot is built with V8_TARGET_ARCH_X64
+and emits an x64 builtins blob into the win-arm64 build.
+
+Restrict the special case to host_os == win so non-Windows hosts fall
+through to clang_x64_v8_arm64 (the arm64-simulator toolchain), matching
+how every other linux->arm64 cross-compile works.
+
+diff --git a/gni/snapshot_toolchain.gni b/gni/snapshot_toolchain.gni
+index 37ed262640d048a6fa5923279ae0388c1c0ae766..c2d36dbcd5f84d9d5cf99266dca85b1f036fa215 100644
+--- a/gni/snapshot_toolchain.gni
++++ b/gni/snapshot_toolchain.gni
+@@ -83,9 +83,11 @@ if (v8_snapshot_toolchain == "") {
+       _cpus = v8_current_cpu
+     } else if (v8_current_cpu == "arm64" || v8_current_cpu == "mips64el" ||
+                v8_current_cpu == "riscv64" || v8_current_cpu == "loong64") {
+-      if (is_win && v8_current_cpu == "arm64") {
++      if (is_win && v8_current_cpu == "arm64" && host_os == "win") {
+         # set _cpus to blank for Windows ARM64 so host_toolchain could be
+-        # selected as snapshot toolchain later.
++        # selected as snapshot toolchain later. Only applies on a Windows
++        # host; a non-Windows host needs the clang_x64_v8_arm64 simulator
++        # toolchain so mksnapshot is built with V8_TARGET_ARCH_ARM64.
+         _cpus = ""
+       } else {
+         _cpus = "x64_v8_${v8_current_cpu}"
+@@ -100,7 +102,7 @@ if (v8_snapshot_toolchain == "") {
+ 
+     if (_cpus != "") {
+       v8_snapshot_toolchain = "//build/toolchain/${host_os}:clang_${_cpus}"
+-    } else if (is_win && v8_current_cpu == "arm64") {
++    } else if (is_win && v8_current_cpu == "arm64" && host_os == "win") {
+       # cross compile Windows arm64 with host toolchain.
+       v8_snapshot_toolchain = host_toolchain
+     }

patches/v8/fix_use_zu_for_size_t_in_arm64_emitunwinddata_snprintf.patch

@@ -0,0 +1,30 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Sam Attard <sattard@anthropic.com>
+Date: Wed, 8 Apr 2026 03:39:01 +0000
+Subject: fix: use %zu for size_t in arm64 EmitUnwindData SNPrintF
+
+The arm64 EmitUnwindData path now compiles on Linux (-Wformat strict)
+since the previous commit re-gated it on V8_TARGET_OS_WIN_ARM64.
+
+diff --git a/src/snapshot/embedded/platform-embedded-file-writer-win.cc b/src/snapshot/embedded/platform-embedded-file-writer-win.cc
+index b2319b9fea8b8ba8189ab577cbcf6982c3733bc0..6d3b3b3fe3e80d40ac71ce69682ea9a26f0d41d3 100644
+--- a/src/snapshot/embedded/platform-embedded-file-writer-win.cc
++++ b/src/snapshot/embedded/platform-embedded-file-writer-win.cc
+@@ -231,7 +231,7 @@ void EmitUnwindData(PlatformEmbeddedFileWriterWin* w,
+         // later.
+         code_chunks.push_back(allowed_chunk_len);
+         fp_adjustments.push_back(xdata_fp_adjustments[j]);
+-        base::SNPrintF(unwind_info_full_symbol, "%s_%u", unwind_info_symbol,
++        base::SNPrintF(unwind_info_full_symbol, "%s_%zu", unwind_info_symbol,
+                        code_chunks.size());
+         w->DeclareRvaToSymbol(embedded_blob_data_symbol,
+                               builtin_start_offset + chunk_start);
+@@ -248,7 +248,7 @@ void EmitUnwindData(PlatformEmbeddedFileWriterWin* w,
+   w->StartXdataSection();
+   {
+     for (size_t i = 0; i < code_chunks.size(); i++) {
+-      base::SNPrintF(unwind_info_full_symbol, "%s_%u", unwind_info_symbol,
++      base::SNPrintF(unwind_info_full_symbol, "%s_%zu", unwind_info_symbol,
+                      i + 1);
+       w->DeclareLabel(unwind_info_full_symbol.begin());
+       std::vector<uint8_t> xdata =

spec/api-crash-reporter-spec.ts

@@ -59,7 +59,6 @@ const startServer = async () => {
   function waitForCrash (): Promise<CrashInfo> {
     return new Promise(resolve => {
       emitter.once('crash', (crash) => {
-        console.log('crash fired', crash);
         resolve(crash);
       });
     });
@@ -70,7 +69,6 @@ const startServer = async () => {
     const fields = {} as Record<string, any>;
     const files = {} as Record<string, Buffer>;
     busboy.on('file', (fieldname, file) => {
-      console.log('Receiving file for :', fieldname);
       const chunks = [] as Array<Buffer>;
       file.on('data', (chunk) => {
         chunks.push(chunk);
@@ -83,12 +81,10 @@ const startServer = async () => {
       fields[fieldname] = val;
     });
     busboy.on('finish', () => {
-      console.log('On finish');
       // breakpad id must be 16 hex digits.
       const reportId = Math.random().toString(16).split('.')[1].padStart(16, '0');
       res.end(reportId, async () => {
         req.socket.destroy();
-        console.log('Emmitting crash:', fields);
         emitter.emit('crash', { ...fields, ...files });
       });
     });
@@ -142,15 +138,10 @@ function waitForNewFileInDir (dir: string): Promise<string[]> {
 ifdescribe(!isLinuxOnArm && !process.mas && !process.env.DISABLE_CRASH_REPORTER_TESTS)('crashReporter module', function () {
   describe('should send minidump', () => {
     it('when renderer crashes', async () => {
-      console.log('starting server for renderer crash test');
       const { port, waitForCrash } = await startServer();
-      console.log('Done starting server for renderer crash test');
       runCrashApp('renderer', port);
-      console.log('Waiting for renderer crash');
       const crash = await waitForCrash();
-      console.log('Renderer crash received');
       checkCrash('renderer', crash);
-      console.log('Renderer crash checked');
       expect(crash.mainProcessSpecific).to.be.undefined();
     });