diff --git a/.bazelci/presubmit.yml b/.bazelci/presubmit.yml
index f3811b0ee..ee53f1c6b 100644
--- a/.bazelci/presubmit.yml
+++ b/.bazelci/presubmit.yml
@@ -40,10 +40,25 @@ x_defaults:
       - "-//test:output_file_map_default"
   windows_common: &windows_common
     platform: windows
+    environment:
+      SWIFT_VERSION: 6.1.0
+      PATH: "%LOCALAPPDATA%\\Programs\\Swift\\Toolchains\\%SWIFT_VERSION%+Asserts\\usr\\bin;%LOCALAPPDATA%\\Programs\\Swift\\Runtimes\\%SWIFT_VERSION%\\usr\\bin;%Path%"
+      SDKROOT: "%LOCALAPPDATA%\\Programs\\Swift\\Platforms\\%SWIFT_VERSION%\\Windows.platform\\Developer\\SDKs\\Windows.sdk"
+    batch_commands:
+      - echo --- Installing Windows SDK
+      - curl.exe -L https://go.microsoft.com/fwlink/?linkid=2342616 -o %TEMP%\winsdkinstaller.exe
+      - PowerShell Start-Process -FilePath ${env:TEMP}\winsdkinstaller.exe -ArgumentList(\"/quiet\", \"/norestart\") -Wait -PassThru -Verb RunAs
+      - PowerShell Start-Process -FilePath "C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Auxiliary\Build\vcvarsall.bat" -ArgumentList(\"/amd64\") -Wait -PassThru -Verb RunAs
+      - echo --- Downloading and installing Swift %SWIFT_VERSION%
+      - curl.exe -L https://download.swift.org/swift-6.1-release/windows10/swift-6.1-RELEASE/swift-6.1-RELEASE-windows10.exe -o %TEMP%\installer.exe
+      - PowerShell Start-Process -FilePath ${env:TEMP}\installer.exe -ArgumentList(\"/install\", \"/passive\", \"/norestart\", \"/log log.txt\") -Wait -PassThru -Verb RunAs
     build_flags:
       # Override 'sandboxed' strategy set in .bazelrc because it's not
       # available on Windows
       - "--strategy=SwiftCompile="
+      - "--repo_env=CC=clang-cl"
+      - "--repo_env=SDKROOT=%LOCALAPPDATA%\\Programs\\Swift\\Platforms\\%SWIFT_VERSION%\\Windows.platform\\Developer\\SDKs\\Windows.sdk"
+      - "--repo_env=Path=%LOCALAPPDATA%\\Programs\\Swift\\Toolchains\\%SWIFT_VERSION%+Asserts\\usr\\bin;%LOCALAPPDATA%\\Programs\\Swift\\Runtimes\\%SWIFT_VERSION%\\usr\\bin;%Path%"
     build_targets:
       - "//tools/..."
 
@@ -131,11 +146,10 @@ tasks:
       - .bazelci/update_workspace_to_deps_heads.sh
     <<: *linux_common
 
-  # TODO: re-enable when Windows in Bazel CI is properly configured for Swift.
-  # windows_last_green:
-  #   name: "Last Green Bazel"
-  #   bazel: last_green
-  #   <<: *windows_common
+  windows_last_green:
+    name: "Latest Bazel"
+    bazel: latest
+    <<: *windows_common
 
   doc_tests:
     name: "Doc tests"
diff --git a/swift/internal/swift_autoconfiguration.bzl b/swift/internal/swift_autoconfiguration.bzl
index 46f1f3746..b1dfbc820 100644
--- a/swift/internal/swift_autoconfiguration.bzl
+++ b/swift/internal/swift_autoconfiguration.bzl
@@ -315,10 +315,10 @@ def _create_windows_toolchain(*, repository_ctx):
     """
     path_to_swiftc = repository_ctx.which("swiftc.exe")
     if not path_to_swiftc:
-        return """\
+        fail("""\
 # No 'swiftc.exe' executable found in $PATH. Not auto-generating a Windows \
 Swift toolchain.
-"""
+""")
 
     root = path_to_swiftc.dirname.dirname
     enabled_features = [
@@ -341,7 +341,7 @@ Swift toolchain.
 
     env = {
         "Path": repository_ctx.os.environ["Path"] if "Path" in repository_ctx.os.environ else repository_ctx.os.environ["PATH"],
-        "ProgramData": repository_ctx.os.environ["ProgramData"],
+        # "ProgramData": repository_ctx.os.environ["ProgramData"],
     }
 
     return """\
@@ -364,7 +364,10 @@ toolchain(
         "@platforms//os:windows",
         "@platforms//cpu:x86_64",
     ],
-    target_compatible_with = APPLE_PLATFORMS_CONSTRAINTS[arch],
+    target_compatible_with = [
+        "@platforms//os:windows",
+        "@platforms//cpu:x86_64",
+    ],
     toolchain = ":windows-toolchain",
     toolchain_type = "{toolchain_type}",
     visibility = ["//visibility:public"],