diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 0000000..aa8cb63
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1 @@
+bcr/** text eol=lf
diff --git a/.github/workflows/bazel.yml b/.github/workflows/bazel.yml
index 9f9ed85..f1a98e7 100644
--- a/.github/workflows/bazel.yml
+++ b/.github/workflows/bazel.yml
@@ -116,10 +116,12 @@ jobs:
           path: artifacts/x86_64-windows-gnu/watchman.exe
           if-no-files-found: error
 
-  build-windows-host:
-    name: Build Windows binary on Windows
+  smoke-windows-msvc:
+    name: Smoke test (x86_64-windows-msvc)
     runs-on: windows-2022
     timeout-minutes: 120
+    env:
+      USE_BAZEL_VERSION: 9.2.0
     steps:
       - uses: actions/checkout@d23441a48e516b6c34aea4fa41551a30e30af803 # v6
 
@@ -127,11 +129,46 @@ jobs:
         with:
           bazelisk-cache: true
           cache-save: ${{ github.event_name != 'pull_request' }}
-          disk-cache: ${{ github.workflow }}-windows-x64
+          disk-cache: ${{ github.workflow }}-windows-msvc
           repository-cache: true
 
-      - name: Build Windows distribution
-        run: bazel build //:watchman-x86_64-windows-gnu
+      - name: Build and smoke test with MSVC
+        shell: pwsh
+        run: |
+          $registry = "file:///" + $env:GITHUB_WORKSPACE.Replace("\", "/") + "/bcr"
+          $bazelArgs = @(
+            "--registry=$registry"
+            "--registry=https://bcr.bazel.build"
+            "--incompatible_autoload_externally=+@rules_cc"
+          )
+
+          Push-Location tests/bcr
+          try {
+            bazel build @bazelArgs "@watchman//:watchman"
+            if ($LASTEXITCODE -ne 0) {
+              throw "MSVC build failed with code $LASTEXITCODE"
+            }
+
+            $outputs = bazel cquery @bazelArgs --output=files "@watchman//:watchman"
+            if ($LASTEXITCODE -ne 0) {
+              throw "MSVC output query failed with code $LASTEXITCODE"
+            }
+
+            $relativeBinary = @($outputs | Where-Object { $_ -like "*.exe" })
+            if ($relativeBinary.Count -ne 1) {
+              throw "expected one Watchman executable, got $($relativeBinary.Count)"
+            }
+
+            $executionRoot = bazel info execution_root
+            if ($LASTEXITCODE -ne 0) {
+              throw "Bazel execution-root query failed with code $LASTEXITCODE"
+            }
+            $watchman = Join-Path $executionRoot $relativeBinary[0]
+          } finally {
+            Pop-Location
+          }
+
+          ./tests/watchman_smoke_test.ps1 -Watchman $watchman
 
   smoke:
     name: Smoke test (${{ matrix.triple }})
diff --git a/bcr/modules/watchman/2026.07.06.00/overlay/BUILD.bazel b/bcr/modules/watchman/2026.07.06.00/overlay/BUILD.bazel
index 92d73f1..31861ee 100644
--- a/bcr/modules/watchman/2026.07.06.00/overlay/BUILD.bazel
+++ b/bcr/modules/watchman/2026.07.06.00/overlay/BUILD.bazel
@@ -204,9 +204,11 @@ watchman_binary(
         ["watchman/**/*.h"],
         exclude = ["watchman/thirdparty/deelevate_binding/**"],
     ),
-    copts = [
-        "-Wall",
-        "-Wextra",
+    copts = select({
+        "@rules_cc//cc/compiler:clang-cl": ["/W4"],
+        "@rules_cc//cc/compiler:msvc-cl": ["/W4"],
+        "//conditions:default": ["-Wall", "-Wextra"],
+    }) + [
         "-DGLOG_NO_ABBREVIATED_SEVERITIES",
         "-I.",
     ] + select({
@@ -302,7 +304,6 @@ watchman_binary(
         "@folly//folly/chrono:conv",
         "@folly//folly/concurrency:unbounded_queue",
         "@folly//folly/concurrency/container:lock_free_ring_buffer",
-        "@folly//folly/debugging/symbolizer",
         "@folly//folly/executors:cpu_thread_pool_executor",
         "@folly//folly/futures:core",
         "@folly//folly/init",
@@ -311,7 +312,6 @@ watchman_binary(
         "@folly//folly/portability:fcntl",
         "@folly//folly/portability:filesystem",
         "@folly//folly/portability:sockets",
-        "@folly//folly/portability:sys_mman",
         "@folly//folly/portability:sys_stat",
         "@folly//folly/portability:sys_time",
         "@folly//folly/portability:sys_types",
@@ -322,6 +322,12 @@ watchman_binary(
         "@folly//folly/system:thread_name",
         "@glog",
     ] + select({
+        ":windows": [],
+        "//conditions:default": [
+            "@folly//folly/debugging/symbolizer",
+            "@folly//folly/portability:sys_mman",
+        ],
+    }) + select({
         ":linux": ["@openssl//:crypto"],
         "//conditions:default": [],
     }),
diff --git a/bcr/modules/watchman/2026.07.06.00/patches/watchman-bazel.patch b/bcr/modules/watchman/2026.07.06.00/patches/watchman-bazel.patch
index e473b51..5e446e5 100644
--- a/bcr/modules/watchman/2026.07.06.00/patches/watchman-bazel.patch
+++ b/bcr/modules/watchman/2026.07.06.00/patches/watchman-bazel.patch
@@ -3,7 +3,7 @@ diff --git a/watchman_binary.bzl b/watchman_binary.bzl
 new file mode 100644
 --- /dev/null
 +++ b/watchman_binary.bzl
-@@ -0,0 +1,9 @@
+@@ -0,0 +1,13 @@
 +"""Watchman binary rule with required transitive C++ settings."""
 +
 +load("@rules_cc//cc:defs.bzl", "cc_binary")
@@ -11,7 +11,11 @@ new file mode 100644
 +
 +_watchman_builder = with_cfg(cc_binary)
 +_watchman_builder.extend("copt", ["-O2"])
-+_watchman_builder.extend("cxxopt", ["-std=gnu++20"])
++_watchman_builder.extend("cxxopt", select({
++    "@rules_cc//cc/compiler:clang-cl": ["/std:c++20", "/utf-8"],
++    "@rules_cc//cc/compiler:msvc-cl": ["/std:c++20", "/utf-8"],
++    "//conditions:default": ["-std=gnu++20"],
++}))
 +watchman_binary, _watchman_binary_internal = _watchman_builder.build()
 diff --git a/watchman/ClientContext.h b/watchman/ClientContext.h
 --- a/watchman/ClientContext.h
diff --git a/bcr/modules/watchman/2026.07.06.00/source.json b/bcr/modules/watchman/2026.07.06.00/source.json
index 7107b56..079cd51 100644
--- a/bcr/modules/watchman/2026.07.06.00/source.json
+++ b/bcr/modules/watchman/2026.07.06.00/source.json
@@ -3,7 +3,7 @@
     "integrity": "sha256-5G72uY4OpCAe9gPmKOrHgWVXOozEusEsdM2rgTxF+fc=",
     "strip_prefix": "watchman-2026.07.06.00",
     "overlay": {
-        "BUILD.bazel": "sha256-NVQROyGBD58UdLnZLQ0TdTduVYIdHaL8zW+nQvAB9uE=",
+        "BUILD.bazel": "sha256-NbEbc5UUuRl18tle9i9ht3bi6eC+nR8jh5ruZdW/LGc=",
         "MODULE.bazel": "sha256-cofDyYwAbnAzhvgElmk6d7CJReE/v45MtgnN4lQJCNg=",
         "bazel/patches/BUILD.bazel": "sha256-bMzIuyOaQOqAyg7TZ36UZjp0iHUaT9KAqHDuhenE56Q=",
         "bazel/patches/edencommon-mingw.patch": "sha256-013B4B2vvHTG4aiKntIFuneADC/fIQA+2fxGargtaI4=",
@@ -13,6 +13,6 @@
     },
     "patch_strip": 1,
     "patches": {
-        "watchman-bazel.patch": "sha256-ikaVrXCDr8YpYQHPqfUNAwbm7nrlkORtosQL2Z0NG/Q="
+        "watchman-bazel.patch": "sha256-U+ckNjBVifZu0d7iXtoCzR4lI6A3yya7QMTnbXIuus8="
     }
 }
diff --git a/tests/bcr/BUILD.bazel b/tests/bcr/BUILD.bazel
index ffd0fb0..d0d43b3 100644
--- a/tests/bcr/BUILD.bazel
+++ b/tests/bcr/BUILD.bazel
@@ -1 +1,6 @@
 package(default_visibility = ["//visibility:public"])
+
+exports_files([
+    "folly-windows.patch",
+    "libevent-windows.patch",
+])
diff --git a/tests/bcr/MODULE.bazel b/tests/bcr/MODULE.bazel
index 4df4341..7ce7eeb 100644
--- a/tests/bcr/MODULE.bazel
+++ b/tests/bcr/MODULE.bazel
@@ -4,3 +4,18 @@ bazel_dep(
     name = "watchman",
     version = "2026.07.06.00",
 )
+
+# libevent's Windows backend includes event2/rpc.h from event_core, but the
+# BCR BUILD file only declares that header on event_extra.
+single_version_override(
+    module_name = "libevent",
+    patch_strip = 1,
+    patches = ["//:libevent-windows.patch"],
+)
+
+# Folly's init target only uses its Unix symbolizer on Linux and macOS.
+single_version_override(
+    module_name = "folly",
+    patch_strip = 1,
+    patches = ["//:folly-windows.patch"],
+)
diff --git a/tests/bcr/folly-windows.patch b/tests/bcr/folly-windows.patch
new file mode 100644
index 0000000..0a8ea73
--- /dev/null
+++ b/tests/bcr/folly-windows.patch
@@ -0,0 +1,111 @@
+diff --git a/folly/debugging/symbolizer/BUILD.bazel b/folly/debugging/symbolizer/BUILD.bazel
+index 853a9f2..d97ff3a 100644
+--- a/folly/debugging/symbolizer/BUILD.bazel
++++ b/folly/debugging/symbolizer/BUILD.bazel
+@@ -32 +31,0 @@ cpp_library(
+-        "//folly/portability/provide:libdwarf",
+@@ -33 +32,4 @@ cpp_library(
+-    ],
++    ] + select({
++        "@platforms//os:windows": [],
++        "//conditions:default": ["//folly/portability/provide:libdwarf"],
++    }),
+diff --git a/folly/BUILD.bazel b/folly/BUILD.bazel
+index d39b8ea..691e80c 100644
+--- a/folly/BUILD.bazel
++++ b/folly/BUILD.bazel
+@@ -275,18 +275,11 @@ cmake_configure_file(
+     defines = [
+         "FOLLY_HAVE_LIBGLOG",
+         "FOLLY_HAVE_LIBGFLAGS",
+-        "FOLLY_HAVE_PTHREAD",
+-        "FOLLY_HAVE_PTHREAD_ATFORK",
+-        "FOLLY_HAVE_PREADV",
+-        "FOLLY_HAVE_PWRITEV",
+         "FOLLY_HAVE_CLOCK_GETTIME",
+         "FOLLY_HAVE_UNALIGNED_ACCESS",
+         "FOLLY_HAVE_VLA",
+         "FOLLY_HAVE_WCHAR_SUPPORT",
+         "HAVE_VSNPRINTF_ERRORS",
+-        "FOLLY_HAVE_DWARF",
+-        "FOLLY_HAVE_SWAPCONTEXT",
+-        "FOLLY_HAVE_BACKTRACE",
+         "FOLLY_HAVE_SHADOW_LOCAL_WARNINGS",
+         "FOLLY_HAVE_LIBLZ4",
+         "FOLLY_HAVE_LIBLZMA",
+@@ -298,11 +291,26 @@ cmake_configure_file(
+         "@platforms//os:windows": [
+             # TODO(kgk): What defines should be set here?
+         ],
+-        "@platforms//os:macos": [],
++        "@platforms//os:macos": [
++            "FOLLY_HAVE_BACKTRACE",
++            "FOLLY_HAVE_DWARF",
++            "FOLLY_HAVE_PTHREAD",
++            "FOLLY_HAVE_PTHREAD_ATFORK",
++            "FOLLY_HAVE_PREADV",
++            "FOLLY_HAVE_PWRITEV",
++            "FOLLY_HAVE_SWAPCONTEXT",
++        ],
+         "@platforms//os:linux": [
+             "FOLLY_HAVE_ACCEPT4",
++            "FOLLY_HAVE_BACKTRACE",
++            "FOLLY_HAVE_DWARF",
+             "FOLLY_HAVE_GETRANDOM",
++            "FOLLY_HAVE_PTHREAD",
++            "FOLLY_HAVE_PTHREAD_ATFORK",
++            "FOLLY_HAVE_PREADV",
++            "FOLLY_HAVE_PWRITEV",
+             "FOLLY_HAVE_PIPE2",
++            "FOLLY_HAVE_SWAPCONTEXT",
+             "FOLLY_HAVE_IFUNC",
+             "FOLLY_HAVE_WEAK_SYMBOLS",
+             "FOLLY_HAVE_LINUX_VDSO",
+@@ -312,11 +320,6 @@ cmake_configure_file(
+             "FOLLY_USE_SYMBOLIZER",
+         ],
+-    }) + select({
+-        "@platforms//cpu:x86_64": [
+-            "FOLLY_HAVE_EXTRANDOM_SFMT19937",
+-        ],
+-        "//conditions:default": [],
+     }) + select({
+         ":with_int128_setting": ["FOLLY_HAVE_INT128_T"],
+         "//conditions:default": [],
+     }),
+diff --git a/folly/Portability.h b/folly/Portability.h
+index f36cb00..fe0184a 100644
+--- a/folly/Portability.h
++++ b/folly/Portability.h
+@@ -25,3 +25,8 @@
++#ifdef _MSC_VER
++#undef FOLLY_HAVE_INT128_T
++#define FOLLY_HAVE_INT128_T 0
++#endif
++
+ #if defined(_MSC_VER)
+ #define FOLLY_CPLUSPLUS _MSVC_LANG
+ #else
+diff --git a/folly/init/BUILD.bazel b/folly/init/BUILD.bazel
+index 8afad13..6d6fd5f 100644
+--- a/folly/init/BUILD.bazel
++++ b/folly/init/BUILD.bazel
+@@ -20,6 +20,7 @@ cpp_library(
+     ] + select({
+         "@platforms//os:linux": ["//folly/debugging/symbolizer:signal_handler"],
+         "@platforms//os:macos": ["//folly/debugging/symbolizer:signal_handler"],
++        "@platforms//os:windows": ["//folly/debugging/symbolizer:signal_handler"],
+         "//conditions:default": [],
+     }),
+ )
+diff --git a/folly/portability/BUILD.bazel b/folly/portability/BUILD.bazel
+index 9c3a4b1..c522440 100644
+--- a/folly/portability/BUILD.bazel
++++ b/folly/portability/BUILD.bazel
+@@ -293,5 +293,6 @@ cpp_library(
+     }),
+     deps = [
++        ":sys_types",
+         ":windows",
+         "//folly:portability",
+     ],
diff --git a/tests/bcr/libevent-windows.patch b/tests/bcr/libevent-windows.patch
new file mode 100644
index 0000000..bc11908
--- /dev/null
+++ b/tests/bcr/libevent-windows.patch
@@ -0,0 +1,12 @@
+diff --git a/BUILD.bazel b/BUILD.bazel
+index 96132f1..5fa50fa 100644
+--- a/BUILD.bazel
++++ b/BUILD.bazel
+@@ -149,6 +149,7 @@ cc_library(
+         # arc4random.c is textually included by evutil_rand.c when
+         # arc4random() is not available. It is not compiled by itself.
+         "arc4random.c",
++        "include/event2/rpc.h",
+     ],
+     visibility = ["//visibility:public"],
+     deps = [