diff --git a/MODULE.bazel b/MODULE.bazel
index b4bcc6f994..3ffde1809c 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -807,25 +807,36 @@ inject_repo(crate, "alsa_lib")
     ]
 ]
 
-bazel_dep(name = "v8", version = "15.2.124.1")
 bazel_dep(name = "rules_license", version = "1.0.0")
 
-archive_override(
-    module_name = "v8",
+engine_repository = use_repo_rule("//third_party/v8:engine_repository.bzl", "engine_repository")
+
+engine_repository(
+    name = "v8",
     integrity = "sha256-aNN5G427qQbP/5o+NXONgXR8ZvS6mjf6mfAI6jtxyzI=",
     patch_strip = 3,
     patches = [
-        "//patches:v8_module_deps.patch",
-        "//patches:v8_bazel_rules.patch",
         "//patches:v8_source_portability.patch",
         "//patches:v8_array_sort_elements_kind.patch",
+        "//third_party/v8:v8_defs.patch",
     ],
     strip_prefix = "v8-15.2.124.1",
     urls = ["https://github.com/v8/v8/archive/refs/tags/15.2.124.1.tar.gz"],
 )
 
-# The dependency repos and their BUILD files belong to Codex. V8 only needs
-# its original apparent repo names to resolve to these same imports.
+# All V8 inputs are owned here, including the pinned Python generator inputs.
+pip.parse(
+    extra_pip_args = ["--require-hashes"],
+    hub_name = "v8_python_deps",
+    python_version = "3.11",
+    requirements_lock = "@v8//:bazel/requirements.txt",
+    simpleapi_skip = [
+        "jinja2",
+        "markupsafe",
+    ],
+)
+use_repo(pip, "v8_python_deps")
+
 v8_dependencies = use_extension("//third_party/v8:dependencies.bzl", "dependencies")
 use_repo(
     v8_dependencies,
@@ -838,19 +849,6 @@ use_repo(
     "v8_simdutf",
 )
 
-v8_dependency_bridge = use_extension("@v8//:bazel/codex_deps.bzl", "codex_deps")
-
-inject_repo(
-    v8_dependency_bridge,
-    dragonbox = "v8_dragonbox",
-    fast_float = "v8_fast_float",
-    fp16 = "v8_fp16",
-    highway = "v8_highway",
-    icu = "v8_icu",
-    simdutf = "v8_simdutf",
-    v8_abseil = "v8_abseil",
-)
-
 http_archive(
     name = "v8_crate_152_2_0",
     build_file = "//third_party/v8:v8_crate.BUILD.bazel",
diff --git a/patches/BUILD.bazel b/patches/BUILD.bazel
index 039167a738..1c62ed89f2 100644
--- a/patches/BUILD.bazel
+++ b/patches/BUILD.bazel
@@ -25,8 +25,6 @@ exports_files([
     "tikv-jemalloc-sys_make_env.patch",
     "tikv-jemalloc-sys_dependency_flags.patch",
     "v8_array_sort_elements_kind.patch",
-    "v8_bazel_rules.patch",
-    "v8_module_deps.patch",
     "v8_source_portability.patch",
     "webrtc-sys_hermetic_darwin_sysroot.patch",
     "windows-link.patch",
diff --git a/patches/v8_bazel_rules.patch b/patches/v8_bazel_rules.patch
deleted file mode 100644
index bcdb9deab5..0000000000
--- a/patches/v8_bazel_rules.patch
+++ /dev/null
@@ -1,456 +0,0 @@
-# What: adapt upstream V8 Bazel rules to this workspace's hermetic toolchains
-# and externally provided dependencies.
-# Scope: Bazel BUILD/defs integration only, including dependency
-# wiring, generated sources, and visibility; no standalone V8 source patching.
-
-diff --git a/orig/v8-15.2.124.1/bazel/defs.bzl b/mod/v8-15.2.124.1/bazel/defs.bzl
---- a/orig/v8-15.2.124.1/bazel/defs.bzl
-+++ b/mod/v8-15.2.124.1/bazel/defs.bzl
-@@ -42,12 +42,30 @@
- )
-
- def v8_flag(name, default = False):
--    _create_option_flag(name = name, build_setting_default = default, scope = "universal")
--    native.config_setting(name = "is_" + name, flag_values = {name: "True"})
--    native.config_setting(name = "is_not_" + name, flag_values = {name: "False"})
--
--def v8_string(name, default = ""):
--    _create_option_string(name = name, build_setting_default = default, scope = "universal")
-+    _create_option_flag(
-+        name = name,
-+        build_setting_default = default,
-+        scope = "universal",
-+        visibility = ["//visibility:public"],
-+    )
-+    native.config_setting(
-+        name = "is_" + name,
-+        flag_values = {name: "True"},
-+        visibility = ["//visibility:public"],
-+    )
-+    native.config_setting(
-+        name = "is_not_" + name,
-+        flag_values = {name: "False"},
-+        visibility = ["//visibility:public"],
-+    )
-+
-+def v8_string(name, default = "", visibility = None):
-+    _create_option_string(
-+        name = name,
-+        build_setting_default = default,
-+        scope = "universal",
-+        visibility = visibility,
-+    )
-
- def v8_int(name, default = 0):
-     _create_option_int(name = name, build_setting_default = default, scope = "universal")
-@@ -106,7 +124,13 @@
-
- def _default_args():
-     return struct(
--        deps = [":define_flags", "@libcxx//:libc++"],
-+        deps = [":define_flags"] + select({
-+            "@v8//:is_v8_use_rusty_v8_custom_libcxx": [
-+                "@@//third_party/v8:rusty_v8_custom_libcxx_headers",
-+                "@@//third_party/v8:rusty_v8_custom_libcxx_runtime",
-+            ],
-+            "//conditions:default": [],
-+        }),
-         defines = select({
-             "@v8//bazel/config:is_windows": [
-                 "UNICODE",
-@@ -136,12 +160,15 @@
-             ],
-             "//conditions:default": [],
-         }) + select({
--            "@v8//bazel/config:is_clang": [
--                "-Wno-invalid-offsetof",
--                "-Wno-deprecated-this-capture",
--                "-Wno-deprecated-declarations",
--                "-std=c++20",
--            ],
-+            "@v8//:is_v8_use_rusty_v8_custom_libcxx": [
-+                "-nostdinc++",
-+                "-D_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS",
-+                "-D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_EXTENSIVE",
-+                "-D_LIBCPP_INSTRUMENTED_WITH_ASAN=0",
-+                "-D_LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS",
-+            ],
-+            "//conditions:default": [],
-+        }) + select({
-             "@v8//bazel/config:is_gcc": [
-                 "-Wno-extra",
-                 "-Wno-array-bounds",
-@@ -161,9 +188,17 @@
-                 "-std=gnu++2a",
-             ],
-             "@v8//bazel/config:is_windows": [
--                "/std:c++20",
--            ],
--            "//conditions:default": [],
-+                "-Wno-invalid-offsetof",
-+                "-Wno-deprecated-this-capture",
-+                "-Wno-deprecated-declarations",
-+                "-std=c++20",
-+            ],
-+            "//conditions:default": [
-+                "-Wno-invalid-offsetof",
-+                "-Wno-deprecated-this-capture",
-+                "-Wno-deprecated-declarations",
-+                "-std=c++20",
-+            ],
-         }) + select({
-             "@v8//bazel/config:is_gcc_fastbuild": [
-                 # Non-debug builds without optimizations fail because
-@@ -187,12 +222,12 @@
-         includes = ["include"],
-         linkopts = select({
-             "@v8//bazel/config:is_windows": [
--                "Winmm.lib",
--                "DbgHelp.lib",
--                "Advapi32.lib",
-+                "-lwinmm",
-+                "-ldbghelp",
-+                "-ladvapi32",
-             ],
-             "@v8//bazel/config:is_macos": ["-pthread"],
--            "//conditions:default": ["-Wl,--no-as-needed -ldl -latomic -pthread"],
-+            "//conditions:default": ["-Wl,--no-as-needed -ldl -pthread"],
-         }) + select({
-             ":should_add_rdynamic": ["-rdynamic"],
-             "//conditions:default": [],
-@@ -466,6 +501,11 @@
- def _mksnapshot(ctx):
-     prefix = ctx.attr.prefix
-     suffix = ctx.attr.suffix
-+    # Windows cross-builds use Linux for the exec configuration, but the
-+    # snapshot generator must match the target ABI and run on the Windows
-+    # runner. Action strategies only choose where an action runs; they cannot
-+    # change this executable from the exec to the target configuration.
-+    tool = ctx.executable.target_tool if ctx.attr.target_os == "win" else ctx.executable.tool
-     outs = [
-         ctx.actions.declare_file(prefix + "/snapshot" + suffix + ".cc"),
-         ctx.actions.declare_file(prefix + "/embedded" + suffix + ".S"),
-@@ -483,7 +523,7 @@
-             "--embedded_src",
-             outs[1].path,
-         ] + ctx.attr.args,
--        executable = ctx.executable.tool,
-+        executable = tool,
-         progress_message = "Running mksnapshot",
-     )
-     return [DefaultInfo(files = depset(outs))]
-@@ -498,6 +538,12 @@
-             executable = True,
-             cfg = "exec",
-         ),
-+        "target_tool": attr.label(
-+            mandatory = True,
-+            allow_files = True,
-+            executable = True,
-+            cfg = "target",
-+        ),
-         "target_os": attr.string(mandatory = True),
-         "prefix": attr.string(mandatory = True),
-         "suffix": attr.string(mandatory = True),
-@@ -511,6 +557,7 @@
-         args = args,
-         prefix = "noicu",
-         tool = ":noicu/mksnapshot" + suffix,
-+        target_tool = ":noicu/mksnapshot" + suffix,
-         suffix = suffix,
-         target_os = select({
-             "@v8//bazel/config:is_macos": "mac",
-@@ -523,6 +570,7 @@
-         args = args,
-         prefix = "icu",
-         tool = ":icu/mksnapshot" + suffix,
-+        target_tool = ":icu/mksnapshot" + suffix,
-         suffix = suffix,
-         target_os = select({
-             "@v8//bazel/config:is_macos": "mac",
-diff --git a/orig/v8-15.2.124.1/BUILD.bazel b/mod/v8-15.2.124.1/BUILD.bazel
---- a/orig/v8-15.2.124.1/BUILD.bazel
-+++ b/mod/v8-15.2.124.1/BUILD.bazel
-@@ -154,6 +154,10 @@
-
- v8_flag(name = "v8_enable_v8_checks")
-
-+v8_flag(name = "v8_enable_sandbox")
-+
-+v8_flag(name = "v8_use_rusty_v8_custom_libcxx")
-+
- v8_flag(name = "v8_enable_verify_csa")
-
- v8_flag(name = "v8_enable_verify_heap")
-@@ -319,7 +323,8 @@
- # If no explicit value for v8_enable_pointer_compression, we set it to 'none'.
- v8_string(
-     name = "v8_enable_pointer_compression",
--    default = "none",
-+    default = "False",
-+    visibility = ["//visibility:public"],
- )
-
- # Default setting for v8_enable_pointer_compression.
-@@ -520,6 +525,7 @@
-         "v8_enable_slow_dchecks": "ENABLE_SLOW_DCHECKS",
-         "v8_enable_runtime_call_stats": "V8_RUNTIME_CALL_STATS",
-         "v8_enable_snapshot_native_code_counters": "V8_SNAPSHOT_NATIVE_CODE_COUNTERS",
-+        "v8_enable_sandbox": "V8_ENABLE_SANDBOX",
-         "v8_enable_trace_maps": "V8_TRACE_MAPS",
-         "v8_enable_turbofan": "V8_ENABLE_TURBOFAN",
-         "v8_enable_v8_checks": "V8_ENABLE_CHECKS",
-@@ -4170,28 +4176,14 @@
-     }),
- )
-
--v8_library(
--  name = "lib_dragonbox",
--  srcs = ["third_party/dragonbox/src/include/dragonbox/dragonbox.h"],
--  hdrs = [
--    "third_party/dragonbox/src/include/dragonbox/dragonbox.h",
--  ],
--  includes = [
--    "third_party/dragonbox/src/include",
--  ],
--)
--
--v8_library(
--  name = "lib_fp16",
--  srcs = ["third_party/fp16/src/include/fp16.h"],
--  hdrs = [
--    "third_party/fp16/src/include/fp16/fp16.h",
--    "third_party/fp16/src/include/fp16/bitcasts.h",
--    "third_party/fp16/src/include/fp16/macros.h",
--  ],
--  includes = [
--    "third_party/fp16/src/include",
--  ],
-+alias(
-+    name = "lib_dragonbox",
-+    actual = "@dragonbox//:dragonbox",
-+)
-+
-+alias(
-+    name = "lib_fp16",
-+    actual = "@fp16//:fp16",
- )
-
- filegroup(
-@@ -4486,6 +4478,20 @@
-     srcs = [
-         "include/js_protocol.pdl",
-         "src/inspector/inspector_protocol_config.json",
-+        "third_party/inspector_protocol/code_generator.py",
-+        "third_party/inspector_protocol/pdl.py",
-+        "third_party/inspector_protocol/lib/Forward_h.template",
-+        "third_party/inspector_protocol/lib/Object_cpp.template",
-+        "third_party/inspector_protocol/lib/Object_h.template",
-+        "third_party/inspector_protocol/lib/Protocol_cpp.template",
-+        "third_party/inspector_protocol/lib/ValueConversions_cpp.template",
-+        "third_party/inspector_protocol/lib/ValueConversions_h.template",
-+        "third_party/inspector_protocol/lib/Values_cpp.template",
-+        "third_party/inspector_protocol/lib/Values_h.template",
-+        "third_party/inspector_protocol/templates/Exported_h.template",
-+        "third_party/inspector_protocol/templates/Imported_h.template",
-+        "third_party/inspector_protocol/templates/TypeBuilder_cpp.template",
-+        "third_party/inspector_protocol/templates/TypeBuilder_h.template",
-     ],
-     outs = [
-         "include/inspector/Debugger.h",
-@@ -4507,15 +4513,19 @@
-         "src/inspector/protocol/Schema.cpp",
-         "src/inspector/protocol/Schema.h",
-     ],
--    cmd = "$(location :code_generator) --jinja_dir . \
--           --inspector_protocol_dir third_party/inspector_protocol \
-+    cmd = "INSPECTOR_PROTOCOL_DIR=$$(dirname $(execpath third_party/inspector_protocol/code_generator.py)); \
-+           PYTHONPATH=$$INSPECTOR_PROTOCOL_DIR:external/rules_python++pip+v8_python_deps_311_jinja2/site-packages:external/rules_python++pip+v8_python_deps_311_markupsafe/site-packages:$${PYTHONPATH-} \
-+           $(execpath @rules_python//python/bin:python) $(execpath third_party/inspector_protocol/code_generator.py) --jinja_dir . \
-+           --inspector_protocol_dir $$INSPECTOR_PROTOCOL_DIR \
-            --config $(location :src/inspector/inspector_protocol_config.json) \
-            --config_value protocol.path=$(location :include/js_protocol.pdl) \
-+           --config_value crdtp.dir=third_party/inspector_protocol/crdtp \
-            --output_base $(@D)/src/inspector",
--    local = 1,
-     message = "Generating inspector files",
-     tools = [
--        ":code_generator",
-+        "@rules_python//python/bin:python",
-+        requirement("jinja2"),
-+        requirement("markupsafe"),
-     ],
- )
-
-@@ -4527,6 +4537,35 @@
-         ":v8_libsampler_files",
-         ":v8_shared_internal_headers",
-     ],
-+)
-+
-+cc_library(
-+    name = "rusty_v8_internal_headers",
-+    hdrs = [
-+        "src/libplatform/default-platform.h",
-+    ],
-+    strip_include_prefix = "",
-+    visibility = ["//visibility:public"],
-+)
-+
-+cc_library(
-+    name = "rusty_v8_crdtp_headers",
-+    hdrs = [
-+        "third_party/inspector_protocol/crdtp/cbor.h",
-+        "third_party/inspector_protocol/crdtp/dispatch.h",
-+        "third_party/inspector_protocol/crdtp/error_support.h",
-+        "third_party/inspector_protocol/crdtp/export.h",
-+        "third_party/inspector_protocol/crdtp/find_by_first.h",
-+        "third_party/inspector_protocol/crdtp/frontend_channel.h",
-+        "third_party/inspector_protocol/crdtp/json.h",
-+        "third_party/inspector_protocol/crdtp/parser_handler.h",
-+        "third_party/inspector_protocol/crdtp/protocol_core.h",
-+        "third_party/inspector_protocol/crdtp/serializable.h",
-+        "third_party/inspector_protocol/crdtp/span.h",
-+        "third_party/inspector_protocol/crdtp/status.h",
-+    ],
-+    strip_include_prefix = "",
-+    visibility = ["//visibility:public"],
- )
-
- filegroup(
-@@ -4609,11 +4648,9 @@
-     strip_include_prefix = "noicu",
- )
-
--cc_library(
-+alias(
-     name = "llvm_libc_headers",
--    hdrs = glob(["third_party/llvm-libc/src/shared/**/*.h"]),
--    includes = ["third_party/llvm-libc/src"],
--    defines = ["LIBC_NAMESPACE=__llvm_libc_cr"],
-+    actual = "@@//third_party/v8:rusty_v8_llvm_libc_headers",
- )
-
- v8_library(
-@@ -4625,9 +4662,9 @@
-     copts = ["-Wno-implicit-fallthrough"],
-     deps = [
-         ":llvm_libc_headers",
--        "@abseil-cpp//absl/synchronization",
--        "@abseil-cpp//absl/time",
--        "@abseil-cpp//absl/functional:overload",
-+        "@v8_abseil//:synchronization",
-+        "@v8_abseil//:time",
-+        "@v8_abseil//:overload",
-     ],
- )
-
-@@ -4655,21 +4692,14 @@
-     deps = [
-         ":torque_base_headers",
-         ":v8_libbase",
--        "@abseil-cpp//absl/container:node_hash_map",
--        "@abseil-cpp//absl/container:node_hash_set",
--    ],
--)
--
--cc_library(
--  name = "simdutf",
--  srcs = ["third_party/simdutf/simdutf.cpp"],
--  hdrs = ["third_party/simdutf/simdutf.h"],
--  copts = select({
--        "@v8//bazel/config:is_clang": ["-std=c++20"],
--        "@v8//bazel/config:is_gcc": ["-std=gnu++2a"],
--        "@v8//bazel/config:is_windows": ["/std:c++20"],
--        "//conditions:default": [],
--    }),
-+        "@v8_abseil//:node_hash_map",
-+        "@v8_abseil//:node_hash_set",
-+    ],
-+)
-+
-+alias(
-+    name = "simdutf",
-+    actual = "@simdutf//:simdutf",
- )
-
- v8_library(
-@@ -4686,7 +4716,7 @@
-     copts = ["-Wno-implicit-fallthrough"],
-     icu_deps = [
-         ":icu/generated_torque_definitions_headers",
--        "//external:icu",
-+        "@icu//:icu",
-     ],
-     icu_srcs = [
-         ":generated_regexp_special_case",
-@@ -4701,14 +4731,14 @@
-     ],
-     deps = [
-         ":lib_dragonbox",
--        "//third_party/fast_float/src:fast_float",
-+        "@fast_float//:fast_float",
-         ":lib_fp16",
-         ":simdutf",
-         ":v8_libbase",
--        "@abseil-cpp//absl/container:btree",
--        "@abseil-cpp//absl/container:flat_hash_map",
--        "@abseil-cpp//absl/container:flat_hash_set",
--        "@abseil-cpp//absl/functional:overload",
-+        "@v8_abseil//:btree",
-+        "@v8_abseil//:flat_hash_map",
-+        "@v8_abseil//:flat_hash_set",
-+        "@v8_abseil//:overload",
-         "@highway//:hwy",
-     ],
- )
-@@ -4757,6 +4787,7 @@
- alias(
-     name = "core_lib_icu",
-     actual = "icu/v8",
-+    visibility = ["//visibility:public"],
- )
-
- v8_library(
-@@ -4808,7 +4839,7 @@
-     ],
-     deps = [
-         ":v8_libbase",
--        "//external:icu",
-+        "@icu//:icu",
-     ],
- )
-
-@@ -4830,8 +4861,8 @@
-     }),
-     deps = [
-         "v8_libbase",
--        "@abseil-cpp//absl/container:node_hash_map",
--        "@abseil-cpp//absl/container:node_hash_set",
-+        "@v8_abseil//:node_hash_map",
-+        "@v8_abseil//:node_hash_set",
-     ],
- )
-
-@@ -4852,9 +4883,20 @@
-         ":icu/generated_torque_initializers",
-         ":icu/v8_initializers_files",
-     ],
-+    # Match GN's mksnapshot `disable_icf` config. If the linker folds distinct
-+    # external-reference helpers together while producing the snapshot, the
-+    # final embedder binary may not fold the same pair and startup
-+    # deserialization will reject the snapshot.
-+    # GN also increases the x64 Windows stack reserve because constructing the
-+    # snapshot overflows the linker's 1 MiB default.
-     linkopts = select({
-         "@v8//bazel/config:is_android": ["-llog"],
--        "//conditions:default": [],
-+        "@v8//bazel/config:is_macos": ["-Wl,-no_deduplicate"],
-+        "@v8//bazel/config:is_windows": [
-+            "-Wl,/OPT:NOICF",
-+            "-Wl,/STACK:2097152",
-+        ],
-+        "//conditions:default": ["-Wl,--icf=none"],
-     }),
-     noicu_deps = [":v8_libshared_noicu"],
-     noicu_srcs = [
diff --git a/patches/v8_module_deps.patch b/patches/v8_module_deps.patch
deleted file mode 100644
index b0ce2f6298..0000000000
--- a/patches/v8_module_deps.patch
+++ /dev/null
@@ -1,231 +0,0 @@
-# What: remove Chromium's checkout-only toolchain bootstrapping and expose one
-# module-extension bridge for dependency imports owned by Codex.
-# Scope: V8 MODULE and the small ingress extension only. Versions, BUILD files,
-# and dependency build policy live in //third_party/v8.
-
-diff --git a/orig/v8-15.2.124.1/MODULE.bazel b/mod/v8-15.2.124.1/MODULE.bazel
---- a/orig/v8-15.2.124.1/MODULE.bazel
-+++ b/mod/v8-15.2.124.1/MODULE.bazel
-@@ -7,13 +7,13 @@
- bazel_dep(name = "rules_cc", version = "0.2.17")
- bazel_dep(name = "rules_python", version = "1.7.0")
- bazel_dep(name = "platforms", version = "1.0.0")
--bazel_dep(name = "abseil-cpp", version = "20250814.1")
--bazel_dep(name = "highway", version = "1.2.0")
-
- pip = use_extension("@rules_python//python/extensions:pip.bzl", "pip")
- pip.parse(
-     hub_name = "v8_python_deps",
-     python_version = "3.11",
-+    # Use the pip resolver to preserve V8's hashes and repository names.
-+    simpleapi_skip = ["jinja2", "markupsafe"],
-     requirements_lock = "//:bazel/requirements.txt",
-     extra_pip_args = [
-         "--require-hashes",
-@@ -22,179 +22,15 @@
- )
- use_repo(pip, "v8_python_deps")
-
--# Define the local LLVM toolchain repository
--llvm_toolchain_repository = use_repo_rule("//bazel/toolchain:llvm_repository.bzl", "llvm_toolchain_repository")
--
--llvm_toolchain_repository(
--    name = "llvm_toolchain",
--    path = "third_party/llvm-build/Release+Asserts",
--    config_file_content = """
--load("@rules_cc//cc:defs.bzl", "CcToolchainConfigInfo", "cc_common")
--load("@bazel_tools//tools/cpp:cc_toolchain_config_lib.bzl", "feature", "flag_group", "flag_set", "tool_path")
--
--def _impl(ctx):
--    tool_paths = [
--        tool_path(name = "gcc", path = "bin/clang"),
--        tool_path(name = "ld", path = "bin/lld"),
--        tool_path(name = "ar", path = "bin/llvm-ar"),
--        tool_path(name = "cpp", path = "bin/clang++"),
--        tool_path(name = "gcov", path = "/bin/false"),
--        tool_path(name = "nm", path = "bin/llvm-nm"),
--        tool_path(name = "objdump", path = "bin/llvm-objdump"),
--        tool_path(name = "strip", path = "bin/llvm-strip"),
--    ]
--
--    features = [
--        feature(
--            name = "default_compile_flags",
--            enabled = True,
--            flag_sets = [
--                flag_set(
--                    actions = [
--                        "c-compile",
--                        "c++-compile",
--                        "c++-header-parsing",
--                        "c++-module-compile",
--                        "c++-module-codegen",
--                        "linkstamp-compile",
--                        "assemble",
--                        "preprocess-assemble",
--                    ],
--                    flag_groups = [
--                        flag_group(
--                            flags = [
--                                "--sysroot={WORKSPACE_ROOT}/build/linux/debian_bullseye_amd64-sysroot",
--                                "-nostdinc++",
--                                "-isystem",
--                                "{WORKSPACE_ROOT}/buildtools/third_party/libc++",
--                                "-isystem",
--                                "{WORKSPACE_ROOT}/third_party/libc++/src/include",
--                                "-isystem",
--                                "{WORKSPACE_ROOT}/third_party/libc++abi/src/include",
--                                "-isystem",
--                                "{WORKSPACE_ROOT}/third_party/libc++/src/src",
--                                "-isystem",
--                                "{WORKSPACE_ROOT}/third_party/llvm-libc/src",
--                                "-D_LIBCPP_HARDENING_MODE_DEFAULT=_LIBCPP_HARDENING_MODE_NONE",
--                                "-DLIBC_NAMESPACE=__llvm_libc_cr",
--                            ],
--                        ),
--                    ],
--                ),
--            ],
--        ),
--        feature(
--            name = "default_linker_flags",
--            enabled = True,
--            flag_sets = [
--                flag_set(
--                    actions = [
--                        "c++-link-executable",
--                        "c++-link-dynamic-library",
--                        "c++-link-nodeps-dynamic-library",
--                    ],
--                    flag_groups = [
--                        flag_group(
--                            flags = [
--                                "--sysroot={WORKSPACE_ROOT}/build/linux/debian_bullseye_amd64-sysroot",
--                                "-fuse-ld=lld",
--                                "-lm",
--                                "-lpthread",
--                            ],
--                        ),
--                    ],
--                ),
--            ],
--        ),
--    ]
--
--    return cc_common.create_cc_toolchain_config_info(
--        ctx = ctx,
--        toolchain_identifier = "local_clang",
--        features = features,
--        cxx_builtin_include_directories = [
--            "{WORKSPACE_ROOT}/buildtools/third_party/libc++",
--            "{WORKSPACE_ROOT}/third_party/libc++/src/include",
--            "{WORKSPACE_ROOT}/third_party/libc++abi/src/include",
--            "{WORKSPACE_ROOT}/third_party/libc++/src/src",
--            "{WORKSPACE_ROOT}/third_party/llvm-libc/src",
--            "{WORKSPACE_ROOT}/third_party/llvm-build/Release+Asserts/lib/clang/22/include",
--            "{WORKSPACE_ROOT}/third_party/llvm-build/Release+Asserts/lib/clang/23/include",
--            "{WORKSPACE_ROOT}/build/linux/debian_bullseye_amd64-sysroot/usr/include",
--            "{WORKSPACE_ROOT}/build/linux/debian_bullseye_amd64-sysroot/usr/local/include",
--        ],
--        host_system_name = "local",
--        target_system_name = "local",
--        target_cpu = "k8",
--        target_libc = "unknown",
--        compiler = "clang",
--        abi_version = "unknown",
--        abi_libc_version = "unknown",
--        tool_paths = tool_paths,
--    )
--
--cc_toolchain_config = rule(
--    implementation = _impl,
--    attrs = {},
--    provides = [CcToolchainConfigInfo],
-+# Codex supplies the dependency repositories used by its V8 builds.
-+codex_deps = use_extension("//:bazel/codex_deps.bzl", "codex_deps")
-+use_repo(
-+    codex_deps,
-+    "v8_abseil",
-+    "dragonbox",
-+    "fast_float",
-+    "fp16",
-+    "highway",
-+    "icu",
-+    "simdutf",
- )
--""",
--    build_file_content = """
--load("@rules_cc//cc:defs.bzl", "cc_toolchain")
--load(":cc_toolchain_config.bzl", "cc_toolchain_config")
--
--package(default_visibility = ["//visibility:public"])
--
--filegroup(
--    name = "all_files",
--    srcs = glob(["**/*"]),
--)
--
--filegroup(name = "empty")
--
--cc_toolchain_config(name = "k8_toolchain_config")
--
--cc_toolchain(
--    name = "k8_toolchain",
--    all_files = ":all_files",
--    ar_files = ":all_files",
--    compiler_files = ":all_files",
--    dwp_files = ":empty",
--    linker_files = ":all_files",
--    objcopy_files = ":all_files",
--    strip_files = ":all_files",
--    supports_param_files = 0,
--    toolchain_config = ":k8_toolchain_config",
--    toolchain_identifier = "local_clang",
--)
--
--toolchain(
--    name = "cc_toolchain_k8",
--    exec_compatible_with = [
--        "@platforms//cpu:x86_64",
--        "@platforms//os:linux",
--    ],
--    target_compatible_with = [
--        "@platforms//cpu:x86_64",
--        "@platforms//os:linux",
--    ],
--    toolchain = ":k8_toolchain",
--    toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",
--)
--""",
--)
--
--register_toolchains("@llvm_toolchain//:cc_toolchain_k8")
--
--# Define local repository for libc++ from third_party sources
--libcxx_repository = use_repo_rule("//bazel/toolchain:libcxx_repository.bzl", "libcxx_repository")
--
--libcxx_repository(
--    name = "libcxx",
--)
--
--single_version_override(
--    module_name = "highway",
--    patches = ["//bazel/patches:highway_rules_cc.patch"],
--    patch_strip = 1,
--)
-
-diff --git a/orig/v8-15.2.124.1/bazel/codex_deps.bzl b/mod/v8-15.2.124.1/bazel/codex_deps.bzl
-new file mode 100644
---- /dev/null
-+++ b/mod/v8-15.2.124.1/bazel/codex_deps.bzl
-@@ -0,0 +1,10 @@
-+"""Dependency ingress for V8 when built by Codex.
-+
-+The root module injects the repositories; this extension declares no defaults
-+that could silently select a different dependency from the one Codex builds.
-+"""
-+
-+def _codex_deps_impl(module_ctx):
-+    return module_ctx.extension_metadata(reproducible = True)
-+
-+codex_deps = module_extension(implementation = _codex_deps_impl)
diff --git a/third_party/v8/BUILD.bazel b/third_party/v8/BUILD.bazel
index 333a608f37..ebc2a802be 100644
--- a/third_party/v8/BUILD.bazel
+++ b/third_party/v8/BUILD.bazel
@@ -10,11 +10,15 @@ exports_files([
     "dependencies.bzl",
     "dependency_config.bzl",
     "dragonbox.BUILD.bazel",
+    "engine.BUILD.bazel",
+    "engine_repository.bzl",
+    "engine_rules.bzl",
     "fast_float.BUILD.bazel",
     "fp16.BUILD.bazel",
     "highway.BUILD.bazel",
     "icu.BUILD.bazel",
     "simdutf.BUILD.bazel",
+    "v8_defs.patch",
 ])
 
 config_setting(
diff --git a/third_party/v8/README.md b/third_party/v8/README.md
index b9659d957e..9c60403e98 100644
--- a/third_party/v8/README.md
+++ b/third_party/v8/README.md
@@ -35,6 +35,10 @@ Use this as the maintainer flow for a version bump:
 2. Update the Bazel versioned inputs in `MODULE.bazel` and the source pins
    in `third_party/v8/dependencies.bzl` and `abseil_repository.bzl` using
    [the source dependency update procedure](#updating-source-dependencies).
+   Verify the imported source groups by querying the source archive and generating Torque
+   and snapshots for each supported platform. If V8 changes its BUILD section
+   layout, the importer fails instead of silently using an old inventory;
+   update that boundary and review its fixed feature and CPU selections.
    Then refresh the matching checksum manifest and generated checksums below.
 3. Publish a release-candidate PR and validate that `v8-canary` passes.
 4. If the canary is green, publish the release tag and release build.
@@ -147,10 +151,20 @@ here declare the targets V8 uses. Abseil, Highway and simdutf apply their C++ ru
 settings through `dependency_config.bzl`; ICU defines its settings in its own
 overlay.
 
-V8's module has a small dependency ingress. The root `MODULE.bazel` injects
-the seven Codex repositories there, so V8's `@highway`, `@icu`, etc. resolve to
-the same repositories Codex declares. The bridge has no fallback downloads.
-V8's BUILD patch still wires these targets into its generator and library graph.
+`engine_repository.bzl` fetches the V8 source pin and installs Codex's engine
+BUILD into `@v8`. Source filegroups are read from the pinned upstream BUILD
+each fetch, including added, removed or reordered groups. The importer rejects
+missing boundaries, malformed or empty sections, and new compiled targets. Only
+the two known Dragonbox and FP16 declarations are skipped, since the dependency
+overlays already supply them. `v8_binary` is valid V8 syntax, but compiled targets
+must be reviewed against the owned engine BUILD on an upgrade. The
+upstream `bazel/config` platform and CPU package is reused unchanged.
+`v8_defs.patch` records just the Codex differences to upstream's
+`bazel/defs.bzl`: release flag visibility, libc++ headers/runtime, Windows
+compiler and linker settings, and snapshot generation. All engine rules,
+including Torque and V8's test configuration helpers, load from that file.
+The engine BUILD owns feature policy and dependency targets; the remaining V8
+ABI, runtime and CPU settings still support the existing release commands.
 
 V8's private Abseil is built from the pinned 20250814.1 sources and uses
 `codex_v8_lts_20250814` for its supported inline-namespace option. Protobuf
@@ -165,9 +179,12 @@ autoupdater: the prebuilt checksum commands above and their CI check validate
 published archive/binding pairs, not these source revisions. Bazel verifies
 the declared download hashes and Git revisions; it does not choose them for us.
 
-Use the V8 tag in the root `MODULE.bazel` `archive_override(module_name = "v8")`
+Use the V8 tag in the root `MODULE.bazel` `engine_repository(name = "v8")`
 (currently `15.2.124.1`) as the input. Read that tag's **unpatched** `DEPS`
-and `MODULE.bazel`; the fetched `@v8` MODULE has Codex's bridge applied.
+and `MODULE.bazel`; `@v8` deliberately does not include upstream's MODULE.
+On an upgrade, also review `v8_defs.patch` against the new `bazel/defs.bzl`
+and run the V8 source canary. A cleanly applying patch does not by itself
+verify new upstream defaults or code-generation behavior.
 
 ```bash
 v8_tag=15.2.124.1 # Replace with the V8 source tag selected for this upgrade.
diff --git a/third_party/v8/engine.BUILD.bazel b/third_party/v8/engine.BUILD.bazel
new file mode 100644
index 0000000000..dba5eca64d
--- /dev/null
+++ b/third_party/v8/engine.BUILD.bazel
@@ -0,0 +1,933 @@
+# Copyright 2021 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+load("@@//third_party/v8:engine_rules.bzl", "v8_fixed_source_features")
+load("@bazel_skylib//lib:selects.bzl", "selects")
+load("@rules_cc//cc:cc_library.bzl", "cc_library")
+load("@rules_python//python:defs.bzl", "py_binary", "py_test")
+load(
+    "@v8//:bazel/defs.bzl",
+    "v8_binary",
+    "v8_build_config",
+    "v8_config",
+    "v8_flag",
+    "v8_library",
+    "v8_mksnapshot",
+    "v8_string",
+    "v8_torque_files",
+)
+load("@v8//:bazel/v8-non-pointer-compression.bzl", "v8_binary_non_pointer_compression")
+load("@v8_python_deps//:requirements.bzl", "requirement")
+
+# Used by the Codex-owned pip hub; pin changes travel with the V8 source.
+exports_files(["bazel/requirements.txt"])
+
+# Codex V8 source policy. Only ABI, runtime and target CPU vary; these still
+# accept the existing release inputs. CPU selection lives in bazel/config.
+# Upstream experiments, profiling and debug flags use their pinned 15.2 defaults.
+# ICU and no-ICU remain separate targets for the engine and its generators.
+v8_flag(name = "v8_enable_sandbox")
+
+v8_flag(name = "v8_use_rusty_v8_custom_libcxx")
+
+# Maglev is supported on the two architectures shipped by Codex. Keep the
+# architecture tests separate from feature policy for host-tool transitions.
+selects.config_setting_group(
+    name = "enable_maglev",
+    match_any = [
+        "@v8//bazel/config:v8_target_x64",
+        "@v8//bazel/config:v8_target_arm64",
+    ],
+)
+
+selects.config_setting_group(
+    name = "enable_maglev_x64",
+    match_all = [
+        ":enable_maglev",
+        "@v8//bazel/config:v8_target_x64",
+    ],
+)
+
+selects.config_setting_group(
+    name = "enable_maglev_arm64",
+    match_all = [
+        ":enable_maglev",
+        "@v8//bazel/config:v8_target_arm64",
+    ],
+)
+
+# WebAssembly remains enabled; its source implementation still depends on OS.
+selects.config_setting_group(
+    name = "webassembly_on_posix",
+    match_any = ["@v8//bazel/config:is_posix"],
+)
+
+selects.config_setting_group(
+    name = "webassembly_on_windows",
+    match_any = ["@v8//bazel/config:is_windows"],
+)
+
+# Artifact transitions set True or False, never the upstream "none" auto mode.
+# The 32-bit Torque helper can also force this off.
+v8_string(
+    name = "v8_enable_pointer_compression",
+    default = "False",
+    visibility = ["//visibility:public"],
+)
+
+config_setting(
+    name = "is_v8_enable_pointer_compression",
+    flag_values = {":v8_enable_pointer_compression": "True"},
+)
+
+# V8's pinned default short-call policy differs on x64 and arm64. In particular
+# the legacy arm64 non-pointer-compressed profile still uses short calls.
+selects.config_setting_group(
+    name = "v8_target_x64_default_short_builtin_calls",
+    match_all = [
+        "@v8//bazel/config:v8_target_x64",
+        ":is_v8_enable_pointer_compression",
+    ],
+)
+
+selects.config_setting_group(
+    name = "v8_target_arm64_default_short_builtin_calls",
+    match_all = [
+        "@v8//bazel/config:v8_target_arm64",
+        "@v8//bazel/config:is_not_android",
+    ],
+)
+
+selects.config_setting_group(
+    name = "is_v8_enable_short_builtin_calls",
+    match_any = [
+        ":v8_target_x64_default_short_builtin_calls",
+        ":v8_target_arm64_default_short_builtin_calls",
+    ],
+)
+
+# Fixed V8 15.2 Codex feature contract: TurboFan and WebAssembly enabled;
+# experiments, VTune and profiling disabled. Do not hard-code ABI-sensitive
+# values such as sandbox, pointer compression or target CPU into this baseline.
+v8_config(
+    name = "define_flags",
+    conditional_defines = {"v8_enable_sandbox": "V8_ENABLE_SANDBOX"},
+    defines = [
+        "V8_DEPRECATION_WARNINGS",
+        "V8_IMMINENT_DEPRECATION_WARNINGS",
+        "V8_ENABLE_LAZY_SOURCE_POSITIONS",
+        "V8_ENABLE_TURBOFAN",
+        "V8_ENABLE_WEBASSEMBLY",
+        "V8_ENABLE_UNDEFINED_DOUBLE",
+        "V8_USE_HOST_CPU_ARM_FEATURES",
+        "V8_TYPED_ARRAY_MAX_SIZE_IN_HEAP=64",
+    ] + [
+        "GOOGLE3",
+        "V8_ADVANCED_BIGINT_ALGORITHMS",
+        "V8_CONCURRENT_MARKING",
+        "V8_ENABLE_SPARKPLUG",
+        "V8_ENABLE_EXTENSIBLE_RO_SNAPSHOT",
+        "V8_ENABLE_CONTINUATION_PRESERVED_EMBEDDER_DATA",
+        "V8_TLS_USED_IN_LIBRARY",
+    ] + select({
+        "@v8//bazel/config:is_debug": [
+            "DEBUG",
+            "V8_ENABLE_CHECKS",
+        ],
+        "//conditions:default": [],
+    }) + select({
+        "@v8//bazel/config:asan_enabled": ["V8_USE_ADDRESS_SANITIZER"],
+        "//conditions:default": [],
+    }) + select({
+        "@v8//bazel/config:hwasan_enabled": ["V8_USE_HWADDRESS_SANITIZER"],
+        "//conditions:default": [],
+    }) + select({
+        "@v8//bazel/config:msan_enabled": ["V8_USE_MEMORY_SANITIZER"],
+        "//conditions:default": [],
+    }) + select({
+        "@v8//bazel/config:ubsan_enabled": ["V8_USE_UNDEFINED_BEHAVIOR_SANITIZER"],
+        "//conditions:default": [],
+    }) + select(
+        {
+            "@v8//bazel/config:v8_target_ia32": ["V8_TARGET_ARCH_IA32"],
+            "@v8//bazel/config:v8_target_x64": [
+                "V8_TARGET_ARCH_X64",
+                "V8_ENABLE_SPARKPLUG_PLUS",
+            ],
+            "@v8//bazel/config:v8_target_arm": [
+                "V8_TARGET_ARCH_ARM",
+                "CAN_USE_ARMV7_INSTRUCTIONS",
+                "CAN_USE_VFP3_INSTRUCTIONS",
+            ],
+            "@v8//bazel/config:v8_target_arm64": [
+                "V8_TARGET_ARCH_ARM64",
+                "V8_ENABLE_SPARKPLUG_PLUS",
+            ],
+            "@v8//bazel/config:v8_target_s390x": [
+                "V8_TARGET_ARCH_S390X",
+            ],
+            "@v8//bazel/config:v8_target_riscv64": [
+                # NOTE: Bazel rules for riscv64 weren't tested on a real system.
+                "V8_TARGET_ARCH_RISCV64",
+                "CAN_USE_FPU_INSTRUCTIONS",
+            ],
+            "@v8//bazel/config:v8_target_ppc64le": [
+                # NOTE: Bazel rules for ppc64le weren't tested on a real system.
+                "V8_TARGET_ARCH_PPC64",
+            ],
+        },
+        no_match_error = "Please specify a target cpu supported by v8",
+    ) + select({
+        "@v8//bazel/config:is_android": [
+            "V8_HAVE_TARGET_OS",
+            "V8_TARGET_OS_ANDROID",
+        ],
+        "@v8//bazel/config:is_linux": [
+            "V8_HAVE_TARGET_OS",
+            "V8_TARGET_OS_LINUX",
+        ],
+        "@v8//bazel/config:is_macos": [
+            "V8_HAVE_TARGET_OS",
+            "V8_TARGET_OS_MACOS",
+        ],
+        "@v8//bazel/config:is_windows": [
+            "V8_HAVE_TARGET_OS",
+            "V8_TARGET_OS_WIN",
+            "UNICODE",
+            "_UNICODE",
+            "_CRT_RAND_S",
+            "_WIN32_WINNT=0x0A00",
+        ],
+    }) + select({
+        ":is_v8_enable_pointer_compression": [
+            "V8_COMPRESS_POINTERS",
+            "V8_31BIT_SMIS_ON_64BIT_ARCH",
+            "V8_CONTIGUOUS_COMPRESSED_RO_SPACE",
+            "V8_CONTIGUOUS_COMPRESSED_RO_SPACE_SIZE_MB=8",
+        ],
+        "//conditions:default": [],
+    }) + select({
+        ":is_v8_enable_pointer_compression": [
+            "V8_COMPRESS_POINTERS_IN_SHARED_CAGE",
+        ],
+        "//conditions:default": [],
+    }) + select({
+        ":is_v8_enable_short_builtin_calls": [
+            "V8_SHORT_BUILTIN_CALLS",
+        ],
+        "//conditions:default": [],
+    }) + select({
+        ":is_v8_enable_pointer_compression": [
+            "V8_EXTERNAL_CODE_SPACE",
+        ],
+        "//conditions:default": [],
+    }) + select({
+        ":is_v8_enable_pointer_compression": [
+            "V8_STATIC_ROOTS",
+        ],
+        "//conditions:default": [],
+    }) + select({
+        ":enable_maglev": [
+            "V8_ENABLE_MAGLEV",
+        ],
+        "//conditions:default": [],
+    }) + [] + [],
+    deps = [],
+)
+
+# Source inventory and dependency aliases.
+
+# The imported groups retain upstream select names. They express our pinned
+# feature contract here; only CPU, ABI and the C++ runtime actually vary.
+v8_fixed_source_features(
+    name = "pinned_source_features",
+    build_setting_default = True,
+)
+
+config_setting(
+    name = "is_v8_enable_webassembly",
+    flag_values = {":pinned_source_features": "True"},
+)
+
+config_setting(
+    name = "disabled_pinned_source_feature",
+    flag_values = {":pinned_source_features": "False"},
+)
+
+alias(
+    name = "enable_drumbrake_arm64",
+    actual = ":disabled_pinned_source_feature",
+)
+
+alias(
+    name = "enable_drumbrake_x64",
+    actual = ":disabled_pinned_source_feature",
+)
+
+alias(
+    name = "enable_maglev_arm",
+    actual = ":disabled_pinned_source_feature",
+)
+
+alias(
+    name = "enable_maglev_riscv",
+    actual = ":disabled_pinned_source_feature",
+)
+
+alias(
+    name = "is_v8_enable_drumbrake",
+    actual = ":disabled_pinned_source_feature",
+)
+
+alias(
+    name = "is_v8_enable_experimental_tq_to_tsa",
+    actual = ":disabled_pinned_source_feature",
+)
+
+alias(
+    name = "is_v8_wasm_random_fuzzers",
+    actual = ":disabled_pinned_source_feature",
+)
+
+# @CODEX_V8_UPSTREAM_FILEGROUPS@
+
+alias(
+    name = "lib_dragonbox",
+    actual = "@v8_dragonbox//:dragonbox",
+)
+
+alias(
+    name = "lib_fp16",
+    actual = "@v8_fp16//:fp16",
+)
+
+# Generated files
+
+# Define file groups for torque definitions and initializers. Both are
+# generated together, but we can use output_group to split them.
+filegroup(
+    name = "icu/generated_torque_definitions",
+    srcs = [":icu/generated_torque_files"],
+    output_group = "definitions",
+)
+
+filegroup(
+    name = "noicu/generated_torque_definitions",
+    srcs = [":noicu/generated_torque_files"],
+    output_group = "definitions",
+)
+
+filegroup(
+    name = "icu/generated_torque_initializers",
+    srcs = [":icu/generated_torque_files"],
+    output_group = "initializers",
+)
+
+filegroup(
+    name = "noicu/generated_torque_initializers",
+    srcs = [":noicu/generated_torque_files"],
+    output_group = "initializers",
+)
+
+# TODO(victorgomes): Add support to tools/debug_helper,
+# which needs class-debug-readers and debug-macros.
+v8_torque_files(
+    name = "generated_torque_files",
+    args = [] + select({
+        "@v8//bazel/config:v8_target_is_32_bits": ["-m32"],
+        "//conditions:default": [],
+    }),
+    definition_extras = [
+        "bit-field-asserts.cc",
+        "builtin-definitions.h",
+        # "class-debug-readers.cc",
+        # "class-debug-readers.h",
+        "class-forward-declarations.h",
+        # "debug-macros.cc",
+        # "debug-macros.h",
+        "instance-types.h",
+        "interface-descriptors.inc",
+    ],
+    icu_srcs = [":icu/torque_files"],
+    initializer_extras = [
+        "csa-types.h",
+        "enum-verifiers.cc",
+        "exported-macros-assembler.cc",
+        "exported-macros-assembler.h",
+    ],
+    noicu_srcs = [":noicu/torque_files"],
+)
+
+py_binary(
+    name = "code_generator",
+    srcs = [
+        "third_party/inspector_protocol/code_generator.py",
+        "third_party/inspector_protocol/pdl.py",
+    ],
+    data = [
+        "third_party/inspector_protocol/lib/Forward_h.template",
+        "third_party/inspector_protocol/lib/Object_cpp.template",
+        "third_party/inspector_protocol/lib/Object_h.template",
+        "third_party/inspector_protocol/lib/Protocol_cpp.template",
+        "third_party/inspector_protocol/lib/ValueConversions_cpp.template",
+        "third_party/inspector_protocol/lib/ValueConversions_h.template",
+        "third_party/inspector_protocol/lib/Values_cpp.template",
+        "third_party/inspector_protocol/lib/Values_h.template",
+        "third_party/inspector_protocol/templates/Exported_h.template",
+        "third_party/inspector_protocol/templates/Imported_h.template",
+        "third_party/inspector_protocol/templates/TypeBuilder_cpp.template",
+        "third_party/inspector_protocol/templates/TypeBuilder_h.template",
+    ],
+    imports = ["third_party/inspector_protocol/"],
+    deps = [
+        requirement("jinja2"),
+    ],
+)
+
+genrule(
+    name = "generated_inspector_files",
+    srcs = [
+        "include/js_protocol.pdl",
+        "src/inspector/inspector_protocol_config.json",
+        "third_party/inspector_protocol/code_generator.py",
+        "third_party/inspector_protocol/pdl.py",
+        "third_party/inspector_protocol/lib/Forward_h.template",
+        "third_party/inspector_protocol/lib/Object_cpp.template",
+        "third_party/inspector_protocol/lib/Object_h.template",
+        "third_party/inspector_protocol/lib/Protocol_cpp.template",
+        "third_party/inspector_protocol/lib/ValueConversions_cpp.template",
+        "third_party/inspector_protocol/lib/ValueConversions_h.template",
+        "third_party/inspector_protocol/lib/Values_cpp.template",
+        "third_party/inspector_protocol/lib/Values_h.template",
+        "third_party/inspector_protocol/templates/Exported_h.template",
+        "third_party/inspector_protocol/templates/Imported_h.template",
+        "third_party/inspector_protocol/templates/TypeBuilder_cpp.template",
+        "third_party/inspector_protocol/templates/TypeBuilder_h.template",
+    ],
+    outs = [
+        "include/inspector/Debugger.h",
+        "include/inspector/Runtime.h",
+        "include/inspector/Schema.h",
+        "src/inspector/protocol/Forward.h",
+        "src/inspector/protocol/Protocol.cpp",
+        "src/inspector/protocol/Protocol.h",
+        "src/inspector/protocol/Console.cpp",
+        "src/inspector/protocol/Console.h",
+        "src/inspector/protocol/Debugger.cpp",
+        "src/inspector/protocol/Debugger.h",
+        "src/inspector/protocol/HeapProfiler.cpp",
+        "src/inspector/protocol/HeapProfiler.h",
+        "src/inspector/protocol/Profiler.cpp",
+        "src/inspector/protocol/Profiler.h",
+        "src/inspector/protocol/Runtime.cpp",
+        "src/inspector/protocol/Runtime.h",
+        "src/inspector/protocol/Schema.cpp",
+        "src/inspector/protocol/Schema.h",
+    ],
+    cmd = "INSPECTOR_PROTOCOL_DIR=$$(dirname $(execpath third_party/inspector_protocol/code_generator.py)); \
+           PYTHONPATH=$$INSPECTOR_PROTOCOL_DIR:external/rules_python++pip+v8_python_deps_311_jinja2/site-packages:external/rules_python++pip+v8_python_deps_311_markupsafe/site-packages:$${PYTHONPATH-} \
+           $(execpath @rules_python//python/bin:python) $(execpath third_party/inspector_protocol/code_generator.py) --jinja_dir . \
+           --inspector_protocol_dir $$INSPECTOR_PROTOCOL_DIR \
+           --config $(location :src/inspector/inspector_protocol_config.json) \
+           --config_value protocol.path=$(location :include/js_protocol.pdl) \
+           --config_value crdtp.dir=third_party/inspector_protocol/crdtp \
+           --output_base $(@D)/src/inspector",
+    message = "Generating inspector files",
+    tools = [
+        "@rules_python//python/bin:python",
+        requirement("jinja2"),
+        requirement("markupsafe"),
+    ],
+)
+
+filegroup(
+    name = "v8_common_libshared_files",
+    srcs = [
+        ":torque_runtime_support_files",
+        ":v8_libplatform_files",
+        ":v8_libsampler_files",
+        ":v8_shared_internal_headers",
+    ],
+)
+
+cc_library(
+    name = "rusty_v8_internal_headers",
+    hdrs = [
+        "src/libplatform/default-platform.h",
+    ],
+    strip_include_prefix = "",
+    visibility = ["//visibility:public"],
+)
+
+cc_library(
+    name = "rusty_v8_crdtp_headers",
+    hdrs = [
+        "third_party/inspector_protocol/crdtp/cbor.h",
+        "third_party/inspector_protocol/crdtp/dispatch.h",
+        "third_party/inspector_protocol/crdtp/error_support.h",
+        "third_party/inspector_protocol/crdtp/export.h",
+        "third_party/inspector_protocol/crdtp/find_by_first.h",
+        "third_party/inspector_protocol/crdtp/frontend_channel.h",
+        "third_party/inspector_protocol/crdtp/json.h",
+        "third_party/inspector_protocol/crdtp/parser_handler.h",
+        "third_party/inspector_protocol/crdtp/protocol_core.h",
+        "third_party/inspector_protocol/crdtp/serializable.h",
+        "third_party/inspector_protocol/crdtp/span.h",
+        "third_party/inspector_protocol/crdtp/status.h",
+    ],
+    strip_include_prefix = "",
+    visibility = ["//visibility:public"],
+)
+
+filegroup(
+    name = "d8_files",
+    srcs = [
+        "src/d8/async-hooks-wrapper.cc",
+        "src/d8/async-hooks-wrapper.h",
+        "src/d8/d8.cc",
+        "src/d8/d8.h",
+        "src/d8/d8-console.cc",
+        "src/d8/d8-console.h",
+        "src/d8/d8-js.cc",
+        "src/d8/d8-platforms.cc",
+        "src/d8/d8-platforms.h",
+        "src/d8/d8-posix.cc",
+        "src/d8/d8-test.cc",
+        "src/d8/hardware-watchpoints.cc",
+        "src/d8/hardware-watchpoints.h",
+        "src/d8/memory-access-information.cc",
+        "src/d8/memory-access-information.h",
+    ],
+)
+
+genrule(
+    name = "generated_bytecode_builtins_list",
+    srcs = [],
+    outs = ["builtins-generated/bytecodes-builtins-list.h"],
+    cmd = "$(location :bytecode_builtins_list_generator) $@",
+    cmd_bat = "$(location :bytecode_builtins_list_generator) $@",
+    tools = [":bytecode_builtins_list_generator"],
+)
+
+genrule(
+    name = "generated_regexp_special_case",
+    srcs = [],
+    outs = ["src/regexp/special-case.cc"],
+    cmd = "$(location :regexp_special_case_generator) $@",
+    cmd_bat = "$(location :regexp_special_case_generator) $@",
+    tools = [":regexp_special_case_generator"],
+)
+
+v8_mksnapshot(
+    name = "generated_snapshot_files",
+    args = [] + [] + [] + ["--no-native-code-counters"],
+)
+
+# =================================================
+# Libraries rules
+# =================================================
+
+# NOTE: This allow headers to be accessed without the icu/noicu prefixes.
+cc_library(
+    name = "icu/generated_torque_definitions_headers",
+    hdrs = [":icu/generated_torque_definitions"],
+    copts = ["-Wno-implicit-fallthrough"],
+    strip_include_prefix = "icu",
+)
+
+cc_library(
+    name = "noicu/generated_torque_definitions_headers",
+    hdrs = [":noicu/generated_torque_definitions"],
+    copts = ["-Wno-implicit-fallthrough"],
+    strip_include_prefix = "noicu",
+)
+
+alias(
+    name = "llvm_libc_headers",
+    actual = "@@//third_party/v8:rusty_v8_llvm_libc_headers",
+)
+
+v8_library(
+    name = "v8_libbase",
+    srcs = [
+        ":v8_libbase_files",
+        ":v8_shared_internal_headers",
+    ],
+    copts = ["-Wno-implicit-fallthrough"],
+    deps = [
+        ":llvm_libc_headers",
+        "@v8_abseil//:overload",
+        "@v8_abseil//:synchronization",
+        "@v8_abseil//:time",
+    ],
+)
+
+cc_library(
+    name = "torque_base_headers",
+    hdrs = [
+        "src/torque/kythe-data.h",
+        "src/torque/torque-compiler.h",
+    ],
+    copts = ["-Wno-implicit-fallthrough"],
+    include_prefix = "third_party/v8",
+    includes = ["."],
+)
+
+cc_library(
+    name = "kythe_torque_base",
+    srcs = [
+        ":torque_base_files",
+    ],
+    copts = ["-Wno-implicit-fallthrough"] + select({
+        "@v8//bazel/config:is_posix": ["-fexceptions"],
+        "//conditions:default": [],
+    }),
+    features = ["-use_header_modules"],
+    deps = [
+        ":torque_base_headers",
+        ":v8_libbase",
+        "@v8_abseil//:node_hash_map",
+        "@v8_abseil//:node_hash_set",
+    ],
+)
+
+alias(
+    name = "simdutf",
+    actual = "@v8_simdutf//:simdutf",
+)
+
+v8_library(
+    name = "v8_libshared",
+    srcs = [
+        ":v8_base_without_compiler_files",
+        ":v8_common_libshared_files",
+    ] + [
+        ":v8_compiler_files",
+    ],
+    copts = ["-Wno-implicit-fallthrough"],
+    icu_deps = [
+        ":icu/generated_torque_definitions_headers",
+        "@v8_icu//:icu",
+    ],
+    icu_srcs = [
+        ":generated_regexp_special_case",
+        ":icu/generated_torque_definitions",
+        ":icu/v8_base_without_compiler_files",
+    ],
+    noicu_deps = [
+        ":noicu/generated_torque_definitions_headers",
+    ],
+    noicu_srcs = [
+        ":noicu/generated_torque_definitions",
+    ],
+    deps = [
+        # keep
+        ":lib_dragonbox",
+        "@v8_fast_float//:fast_float",
+        ":lib_fp16",
+        ":simdutf",
+        ":v8_libbase",
+        "@v8_abseil//:btree",
+        "@v8_abseil//:flat_hash_map",
+        "@v8_abseil//:flat_hash_set",
+        "@v8_abseil//:overload",
+        "@v8_highway//:hwy",
+    ],
+)
+
+v8_library(
+    name = "v8",
+    srcs = [
+        ":v8_inspector_files",
+    ] + [],
+    hdrs = [":public_header_files"],
+    copts = ["-Wno-implicit-fallthrough"],
+    icu_deps = [":icu/v8_libshared"],
+    icu_srcs = [":icu/snapshot_files"],
+    noicu_deps = [":noicu/v8_libshared"],
+    noicu_srcs = [":noicu/snapshot_files"],
+    visibility = ["//visibility:public"],
+)
+
+v8_library(
+    name = "wee8",
+    srcs = [":wee8_files"],
+    hdrs = [":public_wasm_c_api_header_files"],
+    copts = ["-Wno-implicit-fallthrough"],
+    strip_include_prefix = "third_party",
+    visibility = ["//visibility:public"],
+    deps = [":noicu/v8"] + [],
+)
+
+alias(
+    name = "core_lib_noicu",
+    actual = "noicu/v8",
+)
+
+alias(
+    name = "core_lib_icu",
+    actual = "icu/v8",
+    visibility = ["//visibility:public"],
+)
+
+v8_library(
+    name = "v8_vtune",
+    srcs = [
+        "third_party/vtune/v8-vtune.h",
+        "third_party/vtune/vtune-jit.cc",
+        "third_party/vtune/vtune-jit.h",
+    ],
+    copts = ["-I"],
+    deps = [
+        ":core_lib_noicu",
+        "@intel_ittapi//:lib_ittapi",
+    ],
+)
+
+# =================================================
+# Binary rules
+# =================================================
+
+v8_binary(
+    name = "bytecode_builtins_list_generator",
+    srcs = [
+        "src/builtins/generate-bytecodes-builtins-list.cc",
+        "src/interpreter/bytecode-operands.cc",
+        "src/interpreter/bytecode-operands.h",
+        "src/interpreter/bytecode-traits.h",
+        "src/interpreter/bytecodes.cc",
+        "src/interpreter/bytecodes.h",
+    ],
+    copts = ["-Wno-implicit-fallthrough"],
+    deps = ["v8_libbase"],
+)
+
+v8_binary(
+    name = "regexp_special_case_generator",
+    srcs = [
+        "src/regexp/gen-regexp-special-case.cc",
+        "src/regexp/special-case.h",
+        ":v8_shared_internal_headers",
+    ],
+    copts = ["-Wno-implicit-fallthrough"],
+    defines = [
+        "V8_INTL_SUPPORT",
+        "ICU_UTIL_DATA_IMPL=ICU_UTIL_DATA_STATIC",
+        # src/regexp/regexp-compiler-tonode.cc uses an unsafe ICU method and
+        # access a character implicitly.
+        "UNISTR_FROM_CHAR_EXPLICIT=",
+    ],
+    deps = [
+        ":v8_libbase",
+        "@v8_icu//:icu",
+    ],
+)
+
+v8_binary(
+    name = "torque",
+    srcs = [
+        "src/torque/torque.cc",
+        ":torque_base_files",
+    ],
+    copts = ["-Wno-implicit-fallthrough"] + select({
+        "@v8//bazel/config:is_posix": ["-fexceptions"],
+        "//conditions:default": [],
+    }),
+    features = ["-use_header_modules"],
+    icu_defines = ["V8_INTL_SUPPORT"],
+    linkopts = select({
+        "@v8//bazel/config:is_android": ["-llog"],
+        "//conditions:default": [],
+    }),
+    deps = [
+        "v8_libbase",
+        "@v8_abseil//:node_hash_map",
+        "@v8_abseil//:node_hash_set",
+    ],
+)
+
+v8_binary(
+    name = "mksnapshot",
+    srcs = [
+        ":mksnapshot_files",
+    ] + [],
+    copts = ["-Wno-implicit-fallthrough"],
+    icu_deps = [":icu/v8_libshared"],
+    icu_srcs = [
+        ":icu/generated_torque_initializers",
+        ":icu/v8_initializers_files",
+    ],
+    # Match GN's mksnapshot `disable_icf` config. If the linker folds distinct
+    # external-reference helpers together while producing the snapshot, the
+    # final embedder binary may not fold the same pair and startup
+    # deserialization will reject the snapshot.
+    # GN also increases the x64 Windows stack reserve because constructing the
+    # snapshot overflows the linker's 1 MiB default.
+    linkopts = select({
+        "@v8//bazel/config:is_android": ["-llog"],
+        "@v8//bazel/config:is_macos": ["-Wl,-no_deduplicate"],
+        "@v8//bazel/config:is_windows": [
+            "-Wl,/OPT:NOICF",
+            "-Wl,/STACK:2097152",
+        ],
+        "//conditions:default": ["-Wl,--icf=none"],
+    }),
+    noicu_deps = [":v8_libshared_noicu"],
+    noicu_srcs = [
+        ":noicu/generated_torque_initializers",
+        ":noicu/v8_initializers_files",
+    ],
+)
+
+v8_binary(
+    name = "d8",
+    srcs = [":d8_files"],
+    copts = ["-Wno-implicit-fallthrough"],
+    icu_deps = [":icu/v8"],
+    noicu_deps = [":noicu/v8"],
+)
+
+# This target forces torque to be compiled without pointer compression.
+v8_binary_non_pointer_compression(
+    name = "noicu/torque_non_pointer_compression",
+    binary = "noicu/torque",
+)
+
+v8_binary_non_pointer_compression(
+    name = "icu/torque_non_pointer_compression",
+    binary = "icu/torque",
+)
+
+alias(
+    name = "v8ci",
+    actual = "noicu/v8",
+)
+
+# =================================================
+# Tests
+# =================================================
+
+v8_build_config(
+    name = "v8_build_config",
+    arch = select({
+        "@v8//bazel/config:v8_target_arm64": "arm64",
+        "@v8//bazel/config:v8_target_x64": "x64",
+        "//conditions:default": "x64",
+    }),
+)
+
+# Runs mjsunit with d8.
+py_test(
+    name = "noicu/mjsunit",
+    size = "medium",
+    srcs = [
+        "test/mjsunit/testcfg.py",
+        "tools/predictable_wrapper.py",
+        "tools/run-tests.py",
+    ] + glob(["tools/testrunner/**/*.py"]),
+    args = [
+        "--no-sorting",
+        "--nopresubmit",
+        "--variant=google3",
+        "--outdir noicu",
+        "--verbose",
+    ] + select({
+        "@v8//bazel/config:v8_target_arm64": [
+            "--arch=arm64",
+        ],
+        "@v8//bazel/config:v8_target_x64": [
+            "--arch=x64",
+        ],
+        "//conditions:default": [],
+    }) + [
+        "mjsunit",
+    ],
+    data = [
+        "test",
+        ":noicu/d8",
+        ":noicu/v8_build_config",
+        "//testing/pybase",
+    ] + glob(["test/**"]) + glob(["tools/**/*.js"]) + glob(["tools/**/*.mjs"]),
+    main = "tools/run-tests.py",
+    tags = [
+        # Disable sanitizers, as they don't work in general in V8.
+        "nosan",
+    ],
+)
+
+py_test(
+    name = "icu/mjsunit",
+    size = "medium",
+    srcs = [
+        "test/mjsunit/testcfg.py",
+        "tools/predictable_wrapper.py",
+        "tools/run-tests.py",
+    ] + glob(["tools/testrunner/**/*.py"]),
+    args = [
+        "--no-sorting",
+        "--nopresubmit",
+        "--variant=google3",
+        "--outdir icu",
+        "--verbose",
+    ] + select({
+        "@v8//bazel/config:v8_target_arm64": [
+            "--arch=arm64",
+        ],
+        "@v8//bazel/config:v8_target_x64": [
+            "--arch=x64",
+        ],
+        "//conditions:default": [],
+    }) + [
+        "mjsunit",
+    ],
+    data = [
+        "test",
+        ":icu/d8",
+        ":icu/v8_build_config",
+        "//testing/pybase",
+    ] + glob(["test/**"]) + glob(["tools/**/*.js"]) + glob(["tools/**/*.mjs"]),
+    main = "tools/run-tests.py",
+    tags = [
+        # Disable sanitizers, as they don't work in general in V8.
+        "nosan",
+    ],
+)
+
+py_test(
+    name = "icu/intl",
+    size = "medium",
+    srcs = [
+        "test/intl/testcfg.py",
+        "tools/predictable_wrapper.py",
+        "tools/run-tests.py",
+    ] + glob(["tools/testrunner/**/*.py"]),
+    args = [
+        "--no-sorting",
+        "--nopresubmit",
+        "--variant=google3",
+        "--outdir icu",
+        "--verbose",
+    ] + select({
+        "@v8//bazel/config:v8_target_arm64": [
+            "--arch=arm64",
+        ],
+        "@v8//bazel/config:v8_target_x64": [
+            "--arch=x64",
+        ],
+        "//conditions:default": [],
+    }) + [
+        "intl",
+    ],
+    data = [
+        "test",
+        ":icu/d8",
+        ":icu/v8_build_config",
+        "//testing/pybase",
+    ] + glob(["test/**"]) + glob(["tools/**/*.js"]) + glob(["tools/**/*.mjs"]),
+    main = "tools/run-tests.py",
+    tags = [
+        # Disable sanitizers, as they don't work in general in V8.
+        "nosan",
+    ],
+)
diff --git a/third_party/v8/engine_repository.bzl b/third_party/v8/engine_repository.bzl
new file mode 100644
index 0000000000..dd6b966623
--- /dev/null
+++ b/third_party/v8/engine_repository.bzl
@@ -0,0 +1,93 @@
+"""V8 source import with Codex-owned Bazel entry points.
+
+The root package is placed inside the fetched source tree so relative source
+labels and globs have their normal Bazel semantics. Reuse upstream's platform
+and CPU configuration in place, with Codex's narrow patch to bazel/defs.bzl.
+V8's MODULE and toolchain BUILD files are never part of Codex's dependency or
+toolchain graph.
+"""
+
+# Upstream keeps its source groups in BUILD.bazel, which cannot be loaded as
+# a Starlark library. Reuse filegroups, so labels/globs retain their semantics
+# inside @v8. Compiled targets (including valid V8 v8_library/v8_binary calls)
+# belong in engine.BUILD.bazel, where we wire Codex's dependencies and runtime.
+_INVENTORY_SLOT = "# @CODEX_V8_UPSTREAM_FILEGROUPS@"
+_FILE_GROUPS = "# File group rules"
+_GENERATED_FILES = "# Generated files"
+
+def _upstream_filegroups(upstream):
+    before_and_groups = upstream.split(_FILE_GROUPS)
+    if len(before_and_groups) != 2:
+        fail("V8 source import: expected one File group rules section; review the new pin's BUILD.bazel")
+    groups_and_after = before_and_groups[1].split(_GENERATED_FILES)
+    if len(groups_and_after) != 2:
+        fail("V8 source import: expected one Generated files boundary; review the new pin's BUILD.bazel")
+
+    groups = []
+    statement = []
+    for line in groups_and_after[0].split("\n"):
+        if statement:
+            statement.append(line)
+            if line == ")":
+                source = "\n".join(statement)
+                if statement[0] == "filegroup(":
+                    groups.append(source)
+                elif 'name = "lib_dragonbox",' not in source and 'name = "lib_fp16",' not in source:
+                    fail("V8 filegroup import: unexpected library; review and wire it in third_party/v8/engine.BUILD.bazel: " + source)
+                statement = []
+        elif line in ["filegroup(", "v8_library("]:
+            # The pinned section happens to contain two libraries. Both are
+            # already provided by our dependency overlays; skip only those names.
+            statement = [line]
+        elif line.strip() and not line.startswith("#"):
+            fail("V8 filegroup import: only filegroups can be reused here; review compiled targets (including v8_binary) in third_party/v8/engine.BUILD.bazel. Unexpected statement: " + line)
+
+    # Group count and library order can change without changing the owned graph.
+    # Fail only when the source section is empty, malformed, or unsafe to reuse.
+    if statement:
+        fail("V8 filegroup import: unterminated statement; review the pinned BUILD.bazel: " + "\n".join(statement))
+    if not groups:
+        fail("V8 filegroup import: no filegroups found; review the pinned BUILD.bazel")
+    return "\n\n".join(groups)
+
+def _engine_repository_impl(ctx):
+    ctx.download_and_extract(
+        url = ctx.attr.urls,
+        integrity = ctx.attr.integrity,
+        stripPrefix = ctx.attr.strip_prefix,
+    )
+    inventory = _upstream_filegroups(ctx.read("BUILD.bazel"))
+    template = ctx.read(ctx.attr._engine_build)
+    if template.count(_INVENTORY_SLOT) != 1:
+        fail("Codex V8 BUILD template must contain exactly one upstream filegroup slot")
+
+    for patch in ctx.attr.patches:
+        ctx.patch(patch, strip = ctx.attr.patch_strip)
+
+    # Preserve V8's source layout and the two third-party package boundaries
+    # (disarm and fadec); neither is in the Codex V8 closure. Keep upstream's
+    # platform/CPU package and prevent upstream toolchain discovery.
+    for path in [
+        "MODULE.bazel",
+        "BUILD.bazel",
+        "bazel/toolchain/BUILD.bazel",
+        "bazel/patches/BUILD.bazel",
+    ]:
+        ctx.delete(path)
+    ctx.file("BUILD.bazel", template.replace(_INVENTORY_SLOT, inventory))
+
+engine_repository = repository_rule(
+    implementation = _engine_repository_impl,
+    attrs = {
+        "urls": attr.string_list(mandatory = True),
+        "integrity": attr.string(mandatory = True),
+        "strip_prefix": attr.string(mandatory = True),
+        "patches": attr.label_list(allow_files = True),
+        "patch_strip": attr.int(default = 3),
+        "_engine_build": attr.label(
+            default = Label("//third_party/v8:engine.BUILD.bazel"),
+            allow_single_file = True,
+        ),
+    },
+    doc = "Fetch the pinned V8 source tree and install Codex's engine graph.",
+)
diff --git a/third_party/v8/engine_rules.bzl b/third_party/v8/engine_rules.bzl
new file mode 100644
index 0000000000..87261f33aa
--- /dev/null
+++ b/third_party/v8/engine_rules.bzl
@@ -0,0 +1,13 @@
+"""Codex's fixed selection for branches of the imported V8 source inventory."""
+
+load("@v8//:bazel/defs.bzl", "FlagInfo")
+
+def _options_impl(ctx):
+    return FlagInfo(value = ctx.build_setting_value)
+
+# Source-only features keep upstream select names without adding CLI options.
+# ABI/runtime settings are still V8 release inputs until artifact profiles take over.
+v8_fixed_source_features = rule(
+    implementation = _options_impl,
+    build_setting = config.bool(flag = False),
+)
diff --git a/third_party/v8/v8_defs.patch b/third_party/v8/v8_defs.patch
new file mode 100644
index 0000000000..fea274539d
--- /dev/null
+++ b/third_party/v8/v8_defs.patch
@@ -0,0 +1,176 @@
+# What: adapt the pinned V8 rule helpers to Codex's engine configuration.
+# Scope: bazel/defs.bzl only; the engine graph and dependency choices live in
+# third_party/v8/engine.BUILD.bazel. The platform/CPU config is unmodified V8.
+# Preserve the existing release flags, Chromium libc++ headers/runtime, Clang
+# Windows driver flags, and Windows target-ABI snapshot tool. The optional
+# Linux backtrace link flag is omitted because that feature is fixed off.
+# On a V8 pin change, review these hunks and build the native canary matrix.
+
+--- a/orig/v8-15.2.124.1/bazel/defs.bzl
++++ b/mod/v8-15.2.124.1/bazel/defs.bzl
+@@ -42,12 +42,30 @@
+ )
+
+ def v8_flag(name, default = False):
+-    _create_option_flag(name = name, build_setting_default = default, scope = "universal")
+-    native.config_setting(name = "is_" + name, flag_values = {name: "True"})
+-    native.config_setting(name = "is_not_" + name, flag_values = {name: "False"})
+-
+-def v8_string(name, default = ""):
+-    _create_option_string(name = name, build_setting_default = default, scope = "universal")
++    _create_option_flag(
++        name = name,
++        build_setting_default = default,
++        scope = "universal",
++        visibility = ["//visibility:public"],
++    )
++    native.config_setting(
++        name = "is_" + name,
++        flag_values = {name: "True"},
++        visibility = ["//visibility:public"],
++    )
++    native.config_setting(
++        name = "is_not_" + name,
++        flag_values = {name: "False"},
++        visibility = ["//visibility:public"],
++    )
++
++def v8_string(name, default = "", visibility = None):
++    _create_option_string(
++        name = name,
++        build_setting_default = default,
++        scope = "universal",
++        visibility = visibility,
++    )
+
+ def v8_int(name, default = 0):
+     _create_option_int(name = name, build_setting_default = default, scope = "universal")
+@@ -106,7 +124,13 @@
+
+ def _default_args():
+     return struct(
+-        deps = [":define_flags", "@libcxx//:libc++"],
++        deps = [":define_flags"] + select({
++            "@v8//:is_v8_use_rusty_v8_custom_libcxx": [
++                "@@//third_party/v8:rusty_v8_custom_libcxx_headers",
++                "@@//third_party/v8:rusty_v8_custom_libcxx_runtime",
++            ],
++            "//conditions:default": [],
++        }),
+         defines = select({
+             "@v8//bazel/config:is_windows": [
+                 "UNICODE",
+@@ -136,12 +160,15 @@
+             ],
+             "//conditions:default": [],
+         }) + select({
+-            "@v8//bazel/config:is_clang": [
+-                "-Wno-invalid-offsetof",
+-                "-Wno-deprecated-this-capture",
+-                "-Wno-deprecated-declarations",
+-                "-std=c++20",
+-            ],
++            "@v8//:is_v8_use_rusty_v8_custom_libcxx": [
++                "-nostdinc++",
++                "-D_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS",
++                "-D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_EXTENSIVE",
++                "-D_LIBCPP_INSTRUMENTED_WITH_ASAN=0",
++                "-D_LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS",
++            ],
++            "//conditions:default": [],
++        }) + select({
+             "@v8//bazel/config:is_gcc": [
+                 "-Wno-extra",
+                 "-Wno-array-bounds",
+@@ -161,9 +188,17 @@
+                 "-std=gnu++2a",
+             ],
+             "@v8//bazel/config:is_windows": [
+-                "/std:c++20",
+-            ],
+-            "//conditions:default": [],
++                "-Wno-invalid-offsetof",
++                "-Wno-deprecated-this-capture",
++                "-Wno-deprecated-declarations",
++                "-std=c++20",
++            ],
++            "//conditions:default": [
++                "-Wno-invalid-offsetof",
++                "-Wno-deprecated-this-capture",
++                "-Wno-deprecated-declarations",
++                "-std=c++20",
++            ],
+         }) + select({
+             "@v8//bazel/config:is_gcc_fastbuild": [
+                 # Non-debug builds without optimizations fail because
+@@ -187,15 +222,12 @@
+         includes = ["include"],
+         linkopts = select({
+             "@v8//bazel/config:is_windows": [
+-                "Winmm.lib",
+-                "DbgHelp.lib",
+-                "Advapi32.lib",
++                "-lwinmm",
++                "-ldbghelp",
++                "-ladvapi32",
+             ],
+             "@v8//bazel/config:is_macos": ["-pthread"],
+-            "//conditions:default": ["-Wl,--no-as-needed -ldl -latomic -pthread"],
+-        }) + select({
+-            ":should_add_rdynamic": ["-rdynamic"],
+-            "//conditions:default": [],
++            "//conditions:default": ["-Wl,--no-as-needed -ldl -pthread"],
+         }),
+     )
+
+@@ -466,6 +498,12 @@
+ def _mksnapshot(ctx):
+     prefix = ctx.attr.prefix
+     suffix = ctx.attr.suffix
++
++    # Windows cross-builds use Linux for the exec configuration, but the
++    # snapshot generator must match the target ABI and run on the Windows
++    # runner. Action strategies only choose where an action runs; they cannot
++    # change this executable from the exec to the target configuration.
++    tool = ctx.executable.target_tool if ctx.attr.target_os == "win" else ctx.executable.tool
+     outs = [
+         ctx.actions.declare_file(prefix + "/snapshot" + suffix + ".cc"),
+         ctx.actions.declare_file(prefix + "/embedded" + suffix + ".S"),
+@@ -483,7 +521,7 @@
+             "--embedded_src",
+             outs[1].path,
+         ] + ctx.attr.args,
+-        executable = ctx.executable.tool,
++        executable = tool,
+         progress_message = "Running mksnapshot",
+     )
+     return [DefaultInfo(files = depset(outs))]
+@@ -498,6 +536,12 @@
+             executable = True,
+             cfg = "exec",
+         ),
++        "target_tool": attr.label(
++            mandatory = True,
++            allow_files = True,
++            executable = True,
++            cfg = "target",
++        ),
+         "target_os": attr.string(mandatory = True),
+         "prefix": attr.string(mandatory = True),
+         "suffix": attr.string(mandatory = True),
+@@ -511,6 +555,7 @@
+         args = args,
+         prefix = "noicu",
+         tool = ":noicu/mksnapshot" + suffix,
++        target_tool = ":noicu/mksnapshot" + suffix,
+         suffix = suffix,
+         target_os = select({
+             "@v8//bazel/config:is_macos": "mac",
+@@ -523,6 +568,7 @@
+         args = args,
+         prefix = "icu",
+         tool = ":icu/mksnapshot" + suffix,
++        target_tool = ":icu/mksnapshot" + suffix,
+         suffix = suffix,
+         target_os = select({
+             "@v8//bazel/config:is_macos": "mac",