Use Dev Drive for Windows CI

Configure Windows Rust CI jobs and the shared Bazel CI setup to put temp, repository-cache, and output-root paths on the runner's fast work drive when available. Fall back to C: if no secondary drive or Dev Drive provisioning path is available.

Co-authored-by: Codex <noreply@openai.com>

.github/actions/setup-bazel-ci/action.yml

@@ -35,6 +35,11 @@ runs:
     - name: Set up Bazel
       uses: bazel-contrib/setup-bazel@c5acdfb288317d0b5c0bbd7a396a3dc868bb0f86 # 0.19.0
 
+    - name: Configure Dev Drive (Windows)
+      if: runner.os == 'Windows'
+      shell: pwsh
+      run: ./.github/scripts/setup-dev-drive.ps1
+
     - name: Configure Bazel repository cache
       id: configure_bazel_repository_cache
       shell: pwsh
@@ -42,7 +47,12 @@ runs:
         # Keep the repository cache under HOME on all runners. Windows `D:\a`
         # cache paths match `.bazelrc`, but `actions/cache/restore` currently
         # returns HTTP 400 for that path in the Windows clippy job.
-        $repositoryCachePath = Join-Path $HOME '.cache/bazel-repo-cache'
+        $cacheRoot = if ($env:RUNNER_OS -eq 'Windows' -and $env:DEV_DRIVE) {
+          $env:DEV_DRIVE
+        } else {
+          $HOME
+        }
+        $repositoryCachePath = Join-Path $cacheRoot '.cache/bazel-repo-cache'
         "repository-cache-path=$repositoryCachePath" | Out-File -FilePath $env:GITHUB_OUTPUT -Encoding utf8 -Append
         "BAZEL_REPOSITORY_CACHE=$repositoryCachePath" | Out-File -FilePath $env:GITHUB_ENV -Encoding utf8 -Append
 
@@ -50,11 +60,10 @@ runs:
       if: runner.os == 'Windows'
       shell: pwsh
       run: |
-        # Use the shortest available drive to reduce argv/path length issues,
-        # but avoid the drive root because some Windows test launchers mis-handle
-        # MANIFEST paths there.
-        $hasDDrive = Test-Path 'D:\'
-        $bazelOutputUserRoot = if ($hasDDrive) { 'D:\b' } else { 'C:\b' }
+        # Keep Bazel on the fast Windows work drive, but avoid the drive root
+        # because some Windows test launchers mis-handle MANIFEST paths there.
+        $driveRoot = if ($env:DEV_DRIVE) { $env:DEV_DRIVE } elseif (Test-Path 'D:\') { 'D:' } else { 'C:' }
+        $bazelOutputUserRoot = Join-Path $driveRoot 'b'
         $repoContentsCache = Join-Path $env:RUNNER_TEMP "bazel-repo-contents-cache-$env:GITHUB_RUN_ID-$env:GITHUB_JOB"
         "BAZEL_OUTPUT_USER_ROOT=$bazelOutputUserRoot" | Out-File -FilePath $env:GITHUB_ENV -Encoding utf8 -Append
         "BAZEL_REPO_CONTENTS_CACHE=$repoContentsCache" | Out-File -FilePath $env:GITHUB_ENV -Encoding utf8 -Append

.github/scripts/setup-dev-drive.ps1

@@ -0,0 +1,62 @@
+# Configure a fast drive for Windows CI jobs.
+#
+# GitHub-hosted Windows runners do not always expose a secondary D: volume. When
+# they do not, try to create a Dev Drive VHD and fall back to C: if the runner
+# image does not allow that provisioning path.
+
+function Use-FallbackDrive {
+    param([string]$Reason)
+
+    Write-Warning "$Reason Falling back to C:"
+    return "C:"
+}
+
+function Invoke-BestEffort {
+    param([scriptblock]$Script, [string]$Description)
+
+    try {
+        & $Script
+    } catch {
+        Write-Warning "$Description failed: $($_.Exception.Message)"
+    }
+}
+
+if (Test-Path "D:\") {
+    Write-Output "Using existing drive at D:"
+    $Drive = "D:"
+} else {
+    try {
+        $VhdPath = Join-Path $env:RUNNER_TEMP "codex-dev-drive.vhdx"
+        $SizeBytes = 64GB
+
+        if (Test-Path $VhdPath) {
+            Remove-Item -Path $VhdPath -Force
+        }
+
+        New-VHD -Path $VhdPath -SizeBytes $SizeBytes -Dynamic -ErrorAction Stop | Out-Null
+        $Mounted = Mount-VHD -Path $VhdPath -Passthru -ErrorAction Stop
+        $Disk = $Mounted | Get-Disk -ErrorAction Stop
+        $Disk | Initialize-Disk -PartitionStyle GPT -ErrorAction Stop
+        $Partition = $Disk | New-Partition -AssignDriveLetter -UseMaximumSize -ErrorAction Stop
+        $Volume = $Partition | Format-Volume -FileSystem ReFS -NewFileSystemLabel "CodexDevDrive" -DevDrive -Confirm:$false -Force -ErrorAction Stop
+
+        $Drive = "$($Volume.DriveLetter):"
+
+        Invoke-BestEffort { fsutil devdrv trust $Drive } "Trusting Dev Drive $Drive"
+        Invoke-BestEffort { fsutil devdrv enable /disallowAv } "Disabling AV filter attachment for Dev Drives"
+        Invoke-BestEffort { fsutil devdrv query $Drive } "Querying Dev Drive $Drive"
+
+        Write-Output "Using Dev Drive at $Drive"
+    } catch {
+        $Drive = Use-FallbackDrive "Failed to create Dev Drive: $($_.Exception.Message)"
+    }
+}
+
+$Tmp = "$Drive\codex-tmp"
+New-Item -Path $Tmp -ItemType Directory -Force | Out-Null
+
+@(
+    "DEV_DRIVE=$Drive"
+    "TMP=$Tmp"
+    "TEMP=$Tmp"
+) | Out-File -FilePath $env:GITHUB_ENV -Encoding utf8 -Append

.github/workflows/rust-ci-full.yml

@@ -245,6 +245,10 @@ jobs:
 
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+      - name: Configure Dev Drive (Windows)
+        if: ${{ runner.os == 'Windows' }}
+        shell: pwsh
+        run: ../.github/scripts/setup-dev-drive.ps1
       - name: Install Linux build dependencies
         if: ${{ runner.os == 'Linux' }}
         shell: bash
@@ -573,6 +577,10 @@ jobs:
 
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+      - name: Configure Dev Drive (Windows)
+        if: ${{ runner.os == 'Windows' }}
+        shell: pwsh
+        run: ../.github/scripts/setup-dev-drive.ps1
       - name: Install Linux build dependencies
         if: ${{ runner.os == 'Linux' }}
         shell: bash