From 782bbf2a2c8e57602277627b0b9e77dc19706440 Mon Sep 17 00:00:00 2001
From: Michael Lively <milively@microsoft.com>
Date: Tue, 20 Oct 2026 17:34:41 -0700
Subject: [PATCH 01/10] ci: move PR checks to GitHub-hosted 8-core runners

Replace the 1ES self-hosted pools in pr.yml, pr-win32-test.yml and
pr-node-modules.yml with the vscode-large-runners-ubuntu-8-core and
vscode-large-runners-windows-8-core pools, and move the Linux test and
CLI jobs from the standard 4-core runners to the 8-core pool.

The Electron cache version includes the absolute cache path, so update
the runner home directories in detect-missing-caches to the GitHub-hosted
ones (/home/runner, C:\Users\runneradmin).

Refs: microsoft/vscode-engineering#4273

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .github/actions/detect-missing-caches/detect.ts |  4 ++--
 .github/workflows/pr-linux-cli-test.yml         |  2 +-
 .github/workflows/pr-linux-test.yml             |  2 +-
 .github/workflows/pr-node-modules.yml           | 10 +++++-----
 .github/workflows/pr-win32-test.yml             |  3 +--
 .github/workflows/pr.yml                        | 10 +++++-----
 build/lib/test/detectMissingCaches.test.ts      |  4 ++--
 7 files changed, 17 insertions(+), 18 deletions(-)

diff --git a/.github/actions/detect-missing-caches/detect.ts b/.github/actions/detect-missing-caches/detect.ts
index 85bdb8ed4bf88f..120706ee11677f 100644
--- a/.github/actions/detect-missing-caches/detect.ts
+++ b/.github/actions/detect-missing-caches/detect.ts
@@ -110,9 +110,9 @@ export const cacheWarmingJobs: Readonly<Record<string, ICacheWarmingJob>> = {
  * depends on the home directory of the runners and is part of the cache version.
  */
 const electronCachePaths: Readonly<Record<RunnerOs, string>> = {
-	Linux: '/home/cloudtest/.cache/electron',
+	Linux: '/home/runner/.cache/electron',
 	macOS: '/Users/runner/Library/Caches/electron',
-	Windows: 'C:\\Users\\cloudtest\\AppData\\Local\\electron\\Cache',
+	Windows: 'C:\\Users\\runneradmin\\AppData\\Local\\electron\\Cache',
 };
 
 /**
diff --git a/.github/workflows/pr-linux-cli-test.yml b/.github/workflows/pr-linux-cli-test.yml
index b266f440049fee..0c1ad94f122ce0 100644
--- a/.github/workflows/pr-linux-cli-test.yml
+++ b/.github/workflows/pr-linux-cli-test.yml
@@ -34,7 +34,7 @@ jobs:
     # Skip this job rather than the calling job: a skipped job still reports
     # "<caller> / <job name>", which satisfies required status checks.
     if: ${{ inputs.affected }}
-    runs-on: ubuntu-24.04
+    runs-on: vscode-large-runners-ubuntu-8-core
     env:
       RUSTUP_TOOLCHAIN: ${{ inputs.rustup_toolchain }}
     steps:
diff --git a/.github/workflows/pr-linux-test.yml b/.github/workflows/pr-linux-test.yml
index 40b8b644d6eae1..716dd03c487eb0 100644
--- a/.github/workflows/pr-linux-test.yml
+++ b/.github/workflows/pr-linux-test.yml
@@ -34,7 +34,7 @@ on:
 jobs:
   linux-test:
     name: ${{ inputs.job_name }}
-    runs-on: ubuntu-24.04
+    runs-on: vscode-large-runners-ubuntu-8-core
     env:
       ARTIFACT_NAME: ${{ (inputs.electron_tests && 'electron') || (inputs.browser_tests && 'browser') || (inputs.remote_tests && 'remote') || 'unknown' }}${{ (inputs.unit_tests && !inputs.integration_tests && '-unit') || (!inputs.unit_tests && !inputs.integration_tests && inputs.smoke_tests && '-smoke') || '' }}${{ inputs.smoke_shard_total > 1 && format('-shard{0}', inputs.smoke_shard_index) || '' }}
       NPM_ARCH: x64
diff --git a/.github/workflows/pr-node-modules.yml b/.github/workflows/pr-node-modules.yml
index 9eb1561b03d334..1cf2895d9e305e 100644
--- a/.github/workflows/pr-node-modules.yml
+++ b/.github/workflows/pr-node-modules.yml
@@ -48,7 +48,7 @@ jobs:
     name: Compile
     needs: caches
     if: ${{ !cancelled() && (needs.caches.result != 'success' || needs.caches.outputs.compile == 'true') }}
-    runs-on: [ self-hosted, 1ES.Pool=1es-vscode-oss-ubuntu-22.04-x64, "JobId=compile-${{ github.run_id }}-${{ github.run_number }}-${{ github.run_attempt }}" ]
+    runs-on: vscode-large-runners-ubuntu-8-core
     steps:
       - name: Checkout microsoft/vscode
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
@@ -119,7 +119,7 @@ jobs:
     name: Linux
     needs: caches
     if: ${{ !cancelled() && (needs.caches.result != 'success' || needs.caches.outputs.linux == 'true') }}
-    runs-on: [ self-hosted, 1ES.Pool=1es-vscode-oss-ubuntu-22.04-x64, "JobId=linux-${{ github.run_id }}-${{ github.run_number }}-${{ github.run_attempt }}" ]
+    runs-on: vscode-large-runners-ubuntu-8-core
     env:
       NPM_ARCH: x64
       VSCODE_ARCH: x64
@@ -284,7 +284,7 @@ jobs:
     name: Windows
     needs: caches
     if: ${{ !cancelled() && (needs.caches.result != 'success' || needs.caches.outputs.windows == 'true') }}
-    runs-on: [ self-hosted, 1ES.Pool=1es-vscode-oss-windows-2022-x64, "JobId=windows-${{ github.run_id }}-${{ github.run_number }}-${{ github.run_attempt }}" ]
+    runs-on: vscode-large-runners-windows-8-core
     env:
       NPM_ARCH: x64
       VSCODE_ARCH: x64
@@ -368,7 +368,7 @@ jobs:
     name: Copilot (Linux)
     needs: caches
     if: ${{ !cancelled() && (needs.caches.result != 'success' || needs.caches.outputs.copilot-linux == 'true') }}
-    runs-on: [ self-hosted, 1ES.Pool=1es-vscode-oss-ubuntu-22.04-x64, "JobId=copilot-linux-${{ github.run_id }}-${{ github.run_number }}-${{ github.run_attempt }}" ]
+    runs-on: vscode-large-runners-ubuntu-8-core
     steps:
       - name: Checkout microsoft/vscode
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
@@ -403,7 +403,7 @@ jobs:
     name: Copilot (Windows)
     needs: caches
     if: ${{ !cancelled() && (needs.caches.result != 'success' || needs.caches.outputs.copilot-windows == 'true') }}
-    runs-on: [ self-hosted, 1ES.Pool=1es-vscode-oss-windows-2022-x64, "JobId=copilot-windows-${{ github.run_id }}-${{ github.run_number }}-${{ github.run_attempt }}" ]
+    runs-on: vscode-large-runners-windows-8-core
     steps:
       - name: Checkout microsoft/vscode
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
diff --git a/.github/workflows/pr-win32-test.yml b/.github/workflows/pr-win32-test.yml
index 8086a9302ee1b4..8079faeb488f60 100644
--- a/.github/workflows/pr-win32-test.yml
+++ b/.github/workflows/pr-win32-test.yml
@@ -34,8 +34,7 @@ on:
 jobs:
   windows-test:
     name: ${{ inputs.job_name }}
-    # JobId must be unique per job, so smoke test shards and the browser unit tests part add a suffix
-    runs-on: [ self-hosted, 1ES.Pool=1es-vscode-oss-windows-2022-x64, "JobId=windows-test-${{ inputs.job_name }}${{ (inputs.unit_tests && !inputs.integration_tests && '-unit') || '' }}${{ inputs.smoke_shard_total > 1 && format('-shard{0}', inputs.smoke_shard_index) || '' }}-${{ github.run_id }}-${{ github.run_number }}-${{ github.run_attempt }}" ]
+    runs-on: vscode-large-runners-windows-8-core
     env:
       ARTIFACT_NAME: ${{ (inputs.electron_tests && 'electron') || (inputs.browser_tests && 'browser') || (inputs.remote_tests && 'remote') || 'unknown' }}${{ (inputs.unit_tests && !inputs.integration_tests && '-unit') || (!inputs.unit_tests && !inputs.integration_tests && inputs.smoke_tests && '-smoke') || '' }}${{ inputs.smoke_shard_total > 1 && format('-shard{0}', inputs.smoke_shard_index) || '' }}
       NPM_ARCH: x64
diff --git a/.github/workflows/pr.yml b/.github/workflows/pr.yml
index 2245995803c7a7..41228cefb3f536 100644
--- a/.github/workflows/pr.yml
+++ b/.github/workflows/pr.yml
@@ -49,7 +49,7 @@ jobs:
 
   compile:
     name: Compile & Hygiene
-    runs-on: [ self-hosted, 1ES.Pool=1es-vscode-oss-ubuntu-22.04-x64, "JobId=compile-${{ github.run_id }}-${{ github.run_number }}-${{ github.run_attempt }}" ]
+    runs-on: vscode-large-runners-ubuntu-8-core
     steps:
       - name: Checkout microsoft/vscode
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
@@ -480,7 +480,7 @@ jobs:
     name: Copilot - Check Test Cache
     needs: changes
     if: ${{ !cancelled() && (needs.changes.result != 'success' || needs.changes.outputs.copilot == 'true') }}
-    runs-on: [ self-hosted, 1ES.Pool=1es-vscode-oss-ubuntu-22.04-x64, "JobId=copilot-check-test-cache-${{ github.run_id }}-${{ github.run_number }}-${{ github.run_attempt }}" ]
+    runs-on: vscode-large-runners-ubuntu-8-core
     permissions:
       contents: read
       pull-requests: read
@@ -527,7 +527,7 @@ jobs:
     name: Copilot - Check Telemetry
     needs: changes
     if: ${{ !cancelled() && (needs.changes.result != 'success' || needs.changes.outputs.copilot == 'true') }}
-    runs-on: [ self-hosted, 1ES.Pool=1es-vscode-oss-ubuntu-22.04-x64, "JobId=copilot-check-telemetry-${{ github.run_id }}-${{ github.run_number }}-${{ github.run_attempt }}" ]
+    runs-on: vscode-large-runners-ubuntu-8-core
     permissions:
       contents: read
     steps:
@@ -548,7 +548,7 @@ jobs:
     name: Copilot - Test (Linux)
     needs: changes
     if: ${{ !cancelled() && (needs.changes.result != 'success' || needs.changes.outputs.copilot == 'true') }}
-    runs-on: [ self-hosted, 1ES.Pool=1es-vscode-oss-ubuntu-22.04-x64, "JobId=copilot-linux-tests-${{ github.run_id }}-${{ github.run_number }}-${{ github.run_attempt }}" ]
+    runs-on: vscode-large-runners-ubuntu-8-core
     permissions:
       contents: read
     steps:
@@ -648,7 +648,7 @@ jobs:
     name: Copilot - Test (Windows)
     needs: changes
     if: ${{ !cancelled() && (needs.changes.result != 'success' || needs.changes.outputs.copilot == 'true') }}
-    runs-on: [ self-hosted, 1ES.Pool=1es-vscode-oss-windows-2022-x64, "JobId=copilot-windows-tests-${{ github.run_id }}-${{ github.run_number }}-${{ github.run_attempt }}" ]
+    runs-on: vscode-large-runners-windows-8-core
     permissions:
       contents: read
     steps:
diff --git a/build/lib/test/detectMissingCaches.test.ts b/build/lib/test/detectMissingCaches.test.ts
index 8ceba9876b0ad9..c0cf030ffa1cfc 100644
--- a/build/lib/test/detectMissingCaches.test.ts
+++ b/build/lib/test/detectMissingCaches.test.ts
@@ -45,8 +45,8 @@ function readRepositoryFile(relativePath: string): Buffer {
  * The runners of the cache warming jobs, as the cache keys see them.
  */
 const runners: Record<string, { platform: string; arch: string; os: ICacheWarmingJob['os'] }> = {
-	'1ES.Pool=1es-vscode-oss-ubuntu-22.04-x64': { platform: 'linux', arch: 'x64', os: 'Linux' },
-	'1ES.Pool=1es-vscode-oss-windows-2022-x64': { platform: 'win32', arch: 'x64', os: 'Windows' },
+	'vscode-large-runners-ubuntu-8-core': { platform: 'linux', arch: 'x64', os: 'Linux' },
+	'vscode-large-runners-windows-8-core': { platform: 'win32', arch: 'x64', os: 'Windows' },
 	'macos-26-xlarge': { platform: 'darwin', arch: 'arm64', os: 'macOS' },
 };
 

From f3ef5841cf25b9bf28fa7a4fec4468017bb97870 Mon Sep 17 00:00:00 2001
From: Michael Lively <milively@microsoft.com>
Date: Tue, 20 Oct 2026 18:29:10 -0700
Subject: [PATCH 02/10] ci: TEMP add Windows runner disk diagnostics

Temporary; will be removed before the PR is ready.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .../workflows/tmp-runner-disk-diagnostics.yml | 75 +++++++++++++++++++
 1 file changed, 75 insertions(+)
 create mode 100644 .github/workflows/tmp-runner-disk-diagnostics.yml

diff --git a/.github/workflows/tmp-runner-disk-diagnostics.yml b/.github/workflows/tmp-runner-disk-diagnostics.yml
new file mode 100644
index 00000000000000..d9b199371e426f
--- /dev/null
+++ b/.github/workflows/tmp-runner-disk-diagnostics.yml
@@ -0,0 +1,75 @@
+name: TEMP Runner Disk Diagnostics
+
+on: pull_request
+
+permissions:
+  contents: read
+
+jobs:
+  diagnose:
+    name: Diagnose (${{ matrix.name }})
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - name: large-8-core
+            runner: vscode-large-runners-windows-8-core
+          - name: windows-latest
+            runner: windows-latest
+          - name: 1es
+            runner: 1es
+    runs-on: ${{ matrix.runner == '1es' && fromJSON(format('["self-hosted", "1ES.Pool=1es-vscode-oss-windows-2022-x64", "JobId=diag-{0}-{1}"]', github.run_id, github.run_attempt)) || matrix.runner }}
+    steps:
+      - name: System
+        shell: pwsh
+        run: |
+          Get-CimInstance Win32_Processor | Select-Object Name, NumberOfCores, NumberOfLogicalProcessors | Format-List
+          Get-CimInstance Win32_ComputerSystem | Select-Object Model, TotalPhysicalMemory | Format-List
+          Get-Volume | Where-Object DriveLetter | Format-Table DriveLetter, FileSystem, FileSystemLabel, Size, SizeRemaining -AutoSize
+          Get-PhysicalDisk | Format-Table DeviceId, FriendlyName, MediaType, BusType, Size -AutoSize
+          Get-PhysicalDisk | ForEach-Object { Get-StorageAdvancedProperty -PhysicalDisk $_ } | Format-Table -AutoSize
+          Get-Partition | Where-Object DriveLetter | Format-Table DiskNumber, DriveLetter, Size -AutoSize
+          Get-MpComputerStatus | Select-Object AMRunningMode, AntivirusEnabled, RealTimeProtectionEnabled, OnAccessProtectionEnabled, IoavProtectionEnabled, BehaviorMonitorEnabled | Format-List
+          (Get-MpPreference).ExclusionPath
+          fltmc
+          "GITHUB_WORKSPACE=$env:GITHUB_WORKSPACE RUNNER_TEMP=$env:RUNNER_TEMP TEMP=$env:TEMP LOCALAPPDATA=$env:LOCALAPPDATA USERPROFILE=$env:USERPROFILE"
+
+      - name: Benchmark
+        shell: pwsh
+        run: |
+          function Test-Directory([string] $Root) {
+            $dir = Join-Path $Root "fsbench-$([guid]::NewGuid().ToString('N'))"
+            New-Item -ItemType Directory -Path $dir | Out-Null
+            $bytes = [byte[]]::new(4096)
+            $sw = [Diagnostics.Stopwatch]::StartNew()
+            for ($i = 0; $i -lt 300; $i++) {
+              $fs = [IO.File]::Open("$dir\s$i", 'Create')
+              $fs.Write($bytes, 0, 4096)
+              $fs.Flush($true)
+              $fs.Dispose()
+            }
+            $fsync = $sw.Elapsed.TotalMilliseconds / 300
+            $sw.Restart()
+            for ($i = 0; $i -lt 10000; $i++) { [IO.File]::WriteAllBytes("$dir\f$i", $bytes) }
+            $create = $sw.Elapsed.TotalMilliseconds / 10000
+            $sw.Restart()
+            $big = [byte[]]::new(1GB)
+            $fs = [IO.File]::Open("$dir\big", 'Create')
+            $fs.Write($big, 0, $big.Length)
+            $fs.Flush($true)
+            $fs.Dispose()
+            $seq = 1024 / $sw.Elapsed.TotalSeconds
+            $sw.Restart()
+            Remove-Item -LiteralPath $dir -Recurse -Force
+            $delete = $sw.Elapsed.TotalMilliseconds
+            '{0,-45} fsync {1,7:N2} ms/file | create {2,6:N3} ms/file | 1 GB write+flush {3,6:N0} MB/s | delete 10301 files {4,6:N0} ms' -f $Root, $fsync, $create, $seq, $delete
+          }
+          foreach ($root in @($env:GITHUB_WORKSPACE, $env:RUNNER_TEMP, $env:TEMP, 'C:\', 'D:\') | Select-Object -Unique) {
+            if (Test-Path -LiteralPath $root) { Test-Directory $root }
+          }
+          $sw = [Diagnostics.Stopwatch]::StartNew()
+          for ($i = 0; $i -lt 50; $i++) { cmd.exe /c exit 0 }
+          'spawn cmd.exe: {0:N1} ms' -f ($sw.Elapsed.TotalMilliseconds / 50)
+          $sw.Restart()
+          for ($i = 0; $i -lt 20; $i++) { node -e 0 }
+          'spawn node.exe: {0:N1} ms' -f ($sw.Elapsed.TotalMilliseconds / 20)

From b7475af2ed72938c913817bca8de16c37e481bb6 Mon Sep 17 00:00:00 2001
From: Michael Lively <milively@microsoft.com>
Date: Tue, 20 Oct 2026 18:33:14 -0700
Subject: [PATCH 03/10] ci: TEMP run Agent Host E2E experiments on Windows
 runners

Temporary; will be removed before the PR is ready.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 ...tmp-agent-host-e2e-windows-experiments.yml | 118 ++++++++++++++++++
 .../workflows/tmp-runner-disk-diagnostics.yml |  75 -----------
 2 files changed, 118 insertions(+), 75 deletions(-)
 create mode 100644 .github/workflows/tmp-agent-host-e2e-windows-experiments.yml
 delete mode 100644 .github/workflows/tmp-runner-disk-diagnostics.yml

diff --git a/.github/workflows/tmp-agent-host-e2e-windows-experiments.yml b/.github/workflows/tmp-agent-host-e2e-windows-experiments.yml
new file mode 100644
index 00000000000000..8f9a367ea236ab
--- /dev/null
+++ b/.github/workflows/tmp-agent-host-e2e-windows-experiments.yml
@@ -0,0 +1,118 @@
+name: TEMP Agent Host E2E Windows Experiments
+
+on: pull_request
+
+permissions:
+  contents: read
+
+jobs:
+  experiment:
+    name: AH E2E (${{ matrix.name }})
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - name: large-control
+            runner: vscode-large-runners-windows-8-core
+            devdrive: false
+            jobs: ''
+          - name: large-devdrive-temp
+            runner: vscode-large-runners-windows-8-core
+            devdrive: true
+            jobs: ''
+          - name: large-jobs3
+            runner: vscode-large-runners-windows-8-core
+            devdrive: false
+            jobs: '--jobs 3'
+          - name: 1es-control
+            runner: 1es
+            devdrive: false
+            jobs: ''
+    runs-on: ${{ matrix.runner == '1es' && fromJSON(format('["self-hosted", "1ES.Pool=1es-vscode-oss-windows-2022-x64", "JobId=ahexp-{0}-{1}"]', github.run_id, github.run_attempt)) || matrix.runner }}
+    env:
+      VSCODE_ARCH: x64
+      VSCODE_SKIP_PRELAUNCH: '1'
+    steps:
+      - name: Checkout microsoft/vscode
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          lfs: true
+
+      - name: Create Dev Drive for TEMP
+        if: ${{ matrix.devdrive }}
+        shell: pwsh
+        run: |
+          $sw = [Diagnostics.Stopwatch]::StartNew()
+          $script = Join-Path $env:RUNNER_TEMP 'devdrive.txt'
+          "create vdisk file=`"C:\devdrive.vhdx`" maximum=61440 type=expandable`nattach vdisk`ncreate partition primary`nassign letter=R" | Out-File -Encoding ascii $script
+          diskpart /s $script
+          try {
+            Format-Volume -DriveLetter R -DevDrive -Confirm:$false -Force | Out-Null
+            'Formatted R: as a Dev Drive'
+          } catch {
+            "Dev Drive format failed ($_); falling back to ReFS"
+            Format-Volume -DriveLetter R -FileSystem ReFS -Confirm:$false -Force | Out-Null
+          }
+          fsutil devdrv query R: 2>&1
+          New-Item -ItemType Directory -Path R:\tmp | Out-Null
+          Add-Content -Path $env:GITHUB_ENV -Value "TEMP=R:\tmp"
+          Add-Content -Path $env:GITHUB_ENV -Value "TMP=R:\tmp"
+          "Dev Drive ready in $([int]$sw.Elapsed.TotalSeconds)s"
+          Get-Volume -DriveLetter R | Format-Table -AutoSize
+
+      - name: Setup Node.js
+        uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v7.0.0
+        with:
+          node-version-file: .nvmrc
+
+      - name: Restore node_modules cache
+        id: cache-node-modules
+        uses: ./.github/actions/restore-node-modules
+        with:
+          key-prefix: node_modules-windows
+          key-args: "win32 ${{ env.VSCODE_ARCH }} $(node -p process.arch)"
+
+      - name: Fail on node_modules cache miss
+        if: steps.cache-node-modules.outputs.cache-hit != 'true'
+        run: exit 1
+
+      - name: Transpile client and extensions
+        shell: pwsh
+        run: npm run gulp "transpile-client-esbuild" "transpile-extensions"
+
+      - name: Setup Electron
+        uses: ./.github/actions/setup-electron
+        with:
+          arch: ${{ env.VSCODE_ARCH }}
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Run Agent Host E2E tests with performance counters
+        timeout-minutes: 45
+        shell: pwsh
+        run: |
+          $csv = Join-Path $env:RUNNER_TEMP 'perf.csv'
+          $counters = @('\PhysicalDisk(_Total)\Avg. Disk sec/Write', '\PhysicalDisk(_Total)\Avg. Disk sec/Read', '\PhysicalDisk(_Total)\Disk Transfers/sec', '\PhysicalDisk(_Total)\Current Disk Queue Length', '\Processor(_Total)\% Processor Time', '\Memory\Available MBytes', '\System\Processor Queue Length')
+          $perf = Start-Process typeperf -ArgumentList (@($counters | ForEach-Object { "`"$_`"" }) + @('-si', '5', '-f', 'CSV', '-o', "`"$csv`"", '-y')) -PassThru -WindowStyle Hidden
+          "TEMP=$env:TEMP"
+          $sw = [Diagnostics.Stopwatch]::StartNew()
+          .\scripts\test-agent-host-e2e.bat --tfs "Integration Tests" $(if ($env:EXTRA_ARGS) { $env:EXTRA_ARGS -split ' ' })
+          $exitCode = $LASTEXITCODE
+          "Agent Host E2E exit code $exitCode after $([math]::Round($sw.Elapsed.TotalMinutes, 1)) min"
+          Stop-Process -Id $perf.Id -Force -ErrorAction SilentlyContinue
+          Start-Sleep -Seconds 2
+          $rows = Import-Csv $csv
+          $columns = $rows[0].PSObject.Properties.Name | Select-Object -Skip 1
+          foreach ($column in $columns) {
+            $values = @($rows | ForEach-Object { $_.$column } | Where-Object { $_ -and $_.Trim() } | ForEach-Object { [double]$_ } | Sort-Object)
+            if ($values.Count -eq 0) { continue }
+            $avg = ($values | Measure-Object -Average).Average
+            $p95 = $values[[math]::Min($values.Count - 1, [math]::Floor($values.Count * 0.95))]
+            '{0,-70} avg {1,12:N4}  p95 {2,12:N4}  max {3,12:N4}' -f ($column -replace '^\\\\[^\\]+', ''), $avg, $p95, $values[-1]
+          }
+          exit $exitCode
+        env:
+          EXTRA_ARGS: ${{ matrix.jobs }}
+          VSCODE_SKIP_AGENT_HOST_E2E: '0'
+          AGENT_HOST_TEST_PROFILE: full
+          AGENT_HOST_TEST_PROFILE_REASON: Windows runner experiment
diff --git a/.github/workflows/tmp-runner-disk-diagnostics.yml b/.github/workflows/tmp-runner-disk-diagnostics.yml
deleted file mode 100644
index d9b199371e426f..00000000000000
--- a/.github/workflows/tmp-runner-disk-diagnostics.yml
+++ /dev/null
@@ -1,75 +0,0 @@
-name: TEMP Runner Disk Diagnostics
-
-on: pull_request
-
-permissions:
-  contents: read
-
-jobs:
-  diagnose:
-    name: Diagnose (${{ matrix.name }})
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          - name: large-8-core
-            runner: vscode-large-runners-windows-8-core
-          - name: windows-latest
-            runner: windows-latest
-          - name: 1es
-            runner: 1es
-    runs-on: ${{ matrix.runner == '1es' && fromJSON(format('["self-hosted", "1ES.Pool=1es-vscode-oss-windows-2022-x64", "JobId=diag-{0}-{1}"]', github.run_id, github.run_attempt)) || matrix.runner }}
-    steps:
-      - name: System
-        shell: pwsh
-        run: |
-          Get-CimInstance Win32_Processor | Select-Object Name, NumberOfCores, NumberOfLogicalProcessors | Format-List
-          Get-CimInstance Win32_ComputerSystem | Select-Object Model, TotalPhysicalMemory | Format-List
-          Get-Volume | Where-Object DriveLetter | Format-Table DriveLetter, FileSystem, FileSystemLabel, Size, SizeRemaining -AutoSize
-          Get-PhysicalDisk | Format-Table DeviceId, FriendlyName, MediaType, BusType, Size -AutoSize
-          Get-PhysicalDisk | ForEach-Object { Get-StorageAdvancedProperty -PhysicalDisk $_ } | Format-Table -AutoSize
-          Get-Partition | Where-Object DriveLetter | Format-Table DiskNumber, DriveLetter, Size -AutoSize
-          Get-MpComputerStatus | Select-Object AMRunningMode, AntivirusEnabled, RealTimeProtectionEnabled, OnAccessProtectionEnabled, IoavProtectionEnabled, BehaviorMonitorEnabled | Format-List
-          (Get-MpPreference).ExclusionPath
-          fltmc
-          "GITHUB_WORKSPACE=$env:GITHUB_WORKSPACE RUNNER_TEMP=$env:RUNNER_TEMP TEMP=$env:TEMP LOCALAPPDATA=$env:LOCALAPPDATA USERPROFILE=$env:USERPROFILE"
-
-      - name: Benchmark
-        shell: pwsh
-        run: |
-          function Test-Directory([string] $Root) {
-            $dir = Join-Path $Root "fsbench-$([guid]::NewGuid().ToString('N'))"
-            New-Item -ItemType Directory -Path $dir | Out-Null
-            $bytes = [byte[]]::new(4096)
-            $sw = [Diagnostics.Stopwatch]::StartNew()
-            for ($i = 0; $i -lt 300; $i++) {
-              $fs = [IO.File]::Open("$dir\s$i", 'Create')
-              $fs.Write($bytes, 0, 4096)
-              $fs.Flush($true)
-              $fs.Dispose()
-            }
-            $fsync = $sw.Elapsed.TotalMilliseconds / 300
-            $sw.Restart()
-            for ($i = 0; $i -lt 10000; $i++) { [IO.File]::WriteAllBytes("$dir\f$i", $bytes) }
-            $create = $sw.Elapsed.TotalMilliseconds / 10000
-            $sw.Restart()
-            $big = [byte[]]::new(1GB)
-            $fs = [IO.File]::Open("$dir\big", 'Create')
-            $fs.Write($big, 0, $big.Length)
-            $fs.Flush($true)
-            $fs.Dispose()
-            $seq = 1024 / $sw.Elapsed.TotalSeconds
-            $sw.Restart()
-            Remove-Item -LiteralPath $dir -Recurse -Force
-            $delete = $sw.Elapsed.TotalMilliseconds
-            '{0,-45} fsync {1,7:N2} ms/file | create {2,6:N3} ms/file | 1 GB write+flush {3,6:N0} MB/s | delete 10301 files {4,6:N0} ms' -f $Root, $fsync, $create, $seq, $delete
-          }
-          foreach ($root in @($env:GITHUB_WORKSPACE, $env:RUNNER_TEMP, $env:TEMP, 'C:\', 'D:\') | Select-Object -Unique) {
-            if (Test-Path -LiteralPath $root) { Test-Directory $root }
-          }
-          $sw = [Diagnostics.Stopwatch]::StartNew()
-          for ($i = 0; $i -lt 50; $i++) { cmd.exe /c exit 0 }
-          'spawn cmd.exe: {0:N1} ms' -f ($sw.Elapsed.TotalMilliseconds / 50)
-          $sw.Restart()
-          for ($i = 0; $i -lt 20; $i++) { node -e 0 }
-          'spawn node.exe: {0:N1} ms' -f ($sw.Elapsed.TotalMilliseconds / 20)

From 3f0b418246e99138f454e9163a513b236a9a27bc Mon Sep 17 00:00:00 2001
From: Michael Lively <milively@microsoft.com>
Date: Tue, 20 Oct 2026 19:13:39 -0700
Subject: [PATCH 04/10] ci: TEMP add Windows runner spawn diagnostics

Temporary; will be removed before the PR is ready.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .../tmp-runner-spawn-diagnostics.yml          | 49 +++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 .github/workflows/tmp-runner-spawn-diagnostics.yml

diff --git a/.github/workflows/tmp-runner-spawn-diagnostics.yml b/.github/workflows/tmp-runner-spawn-diagnostics.yml
new file mode 100644
index 00000000000000..a213a5e31ac697
--- /dev/null
+++ b/.github/workflows/tmp-runner-spawn-diagnostics.yml
@@ -0,0 +1,49 @@
+name: TEMP Runner Spawn Diagnostics
+
+on: pull_request
+
+permissions:
+  contents: read
+
+jobs:
+  diagnose:
+    name: Spawn (${{ matrix.name }})
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - name: large-8-core
+            runner: vscode-large-runners-windows-8-core
+          - name: windows-latest
+            runner: windows-latest
+          - name: 1es
+            runner: 1es
+    runs-on: ${{ matrix.runner == '1es' && fromJSON(format('["self-hosted", "1ES.Pool=1es-vscode-oss-windows-2022-x64", "JobId=spawn-{0}-{1}"]', github.run_id, github.run_attempt)) || matrix.runner }}
+    steps:
+      - name: Diagnose
+        shell: pwsh
+        run: |
+          $dg = Get-CimInstance -ClassName Win32_DeviceGuard -Namespace root\Microsoft\Windows\DeviceGuard
+          "VBS status: $($dg.VirtualizationBasedSecurityStatus) (0 off, 1 enabled, 2 running)"
+          "Security services running: $($dg.SecurityServicesRunning -join ',') (1 Credential Guard, 2 HVCI)"
+          "Security services configured: $($dg.SecurityServicesConfigured -join ',')"
+          "Hypervisor present: $((Get-CimInstance Win32_ComputerSystem).HypervisorPresent)"
+          (Get-CimInstance Win32_ComputerSystem).Model
+          $node = (Get-Command node).Source
+          "node: $node"
+          foreach ($target in @('cmd.exe', $node)) {
+            for ($round = 0; $round -lt 2; $round++) {
+              $times = @(for ($i = 0; $i -lt 20; $i++) {
+                $sw = [Diagnostics.Stopwatch]::StartNew()
+                if ($target -eq 'cmd.exe') { cmd.exe /c exit 0 } else { & $target -e 0 }
+                $sw.Elapsed.TotalMilliseconds
+              }) | Sort-Object
+              '{0} round {1}: median {2:N1} ms, min {3:N1} ms' -f (Split-Path -Leaf $target), $round, $times[10], $times[0]
+            }
+          }
+          $sw = [Diagnostics.Stopwatch]::StartNew()
+          $x = 0; for ($i = 0; $i -lt 20000000; $i++) { $x += $i }
+          'CPU loop: {0:N0} ms' -f $sw.Elapsed.TotalMilliseconds
+          $sw = [Diagnostics.Stopwatch]::StartNew()
+          node -e "let s=0; for (let i=0;i<3e8;i++) s+=i; console.log(s)" | Out-Null
+          'node CPU loop: {0:N0} ms' -f $sw.Elapsed.TotalMilliseconds

From 215eab0683e88a3420ae9155c13929f5cc56ce57 Mon Sep 17 00:00:00 2001
From: Michael Lively <milively@microsoft.com>
Date: Tue, 20 Oct 2026 19:18:10 -0700
Subject: [PATCH 05/10] ci: TEMP try Dev Drive workspace and flush suppression
 on Windows

Temporary; will be removed before the PR is ready.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 ...tmp-agent-host-e2e-windows-experiments.yml | 97 +++++++++++++------
 .../tmp-runner-spawn-diagnostics.yml          | 49 ----------
 2 files changed, 69 insertions(+), 77 deletions(-)
 delete mode 100644 .github/workflows/tmp-runner-spawn-diagnostics.yml

diff --git a/.github/workflows/tmp-agent-host-e2e-windows-experiments.yml b/.github/workflows/tmp-agent-host-e2e-windows-experiments.yml
index 8f9a367ea236ab..c6e19aebc14c86 100644
--- a/.github/workflows/tmp-agent-host-e2e-windows-experiments.yml
+++ b/.github/workflows/tmp-agent-host-e2e-windows-experiments.yml
@@ -12,53 +12,94 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - name: large-control
+          - name: large-devdrive-workspace
             runner: vscode-large-runners-windows-8-core
-            devdrive: false
+            variant: devdrive
             jobs: ''
-          - name: large-devdrive-temp
+          - name: large-noflush
             runner: vscode-large-runners-windows-8-core
-            devdrive: true
+            variant: noflush
             jobs: ''
-          - name: large-jobs3
-            runner: vscode-large-runners-windows-8-core
-            devdrive: false
-            jobs: '--jobs 3'
-          - name: 1es-control
-            runner: 1es
-            devdrive: false
-            jobs: ''
-    runs-on: ${{ matrix.runner == '1es' && fromJSON(format('["self-hosted", "1ES.Pool=1es-vscode-oss-windows-2022-x64", "JobId=ahexp-{0}-{1}"]', github.run_id, github.run_attempt)) || matrix.runner }}
+    runs-on: ${{ matrix.runner }}
     env:
       VSCODE_ARCH: x64
       VSCODE_SKIP_PRELAUNCH: '1'
     steps:
-      - name: Checkout microsoft/vscode
-        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-        with:
-          lfs: true
-
-      - name: Create Dev Drive for TEMP
-        if: ${{ matrix.devdrive }}
+      - name: Mount Dev Drive at the workspace and TEMP
+        if: ${{ matrix.variant == 'devdrive' }}
         shell: pwsh
         run: |
           $sw = [Diagnostics.Stopwatch]::StartNew()
           $script = Join-Path $env:RUNNER_TEMP 'devdrive.txt'
-          "create vdisk file=`"C:\devdrive.vhdx`" maximum=61440 type=expandable`nattach vdisk`ncreate partition primary`nassign letter=R" | Out-File -Encoding ascii $script
+          "create vdisk file=`"C:\devdrive.vhdx`" maximum=102400 type=expandable`nattach vdisk`ncreate partition primary`nassign letter=R" | Out-File -Encoding ascii $script
           diskpart /s $script
-          try {
-            Format-Volume -DriveLetter R -DevDrive -Confirm:$false -Force | Out-Null
-            'Formatted R: as a Dev Drive'
-          } catch {
-            "Dev Drive format failed ($_); falling back to ReFS"
-            Format-Volume -DriveLetter R -FileSystem ReFS -Confirm:$false -Force | Out-Null
-          }
+          Format-Volume -DriveLetter R -DevDrive -Confirm:$false -Force | Out-Null
           fsutil devdrv query R: 2>&1
+          New-Item -ItemType Directory -Force -Path $env:GITHUB_WORKSPACE | Out-Null
+          if (Get-ChildItem -Force -LiteralPath $env:GITHUB_WORKSPACE) { throw 'Workspace is not empty' }
+          Add-PartitionAccessPath -DriveLetter R -AccessPath $env:GITHUB_WORKSPACE
           New-Item -ItemType Directory -Path R:\tmp | Out-Null
           Add-Content -Path $env:GITHUB_ENV -Value "TEMP=R:\tmp"
           Add-Content -Path $env:GITHUB_ENV -Value "TMP=R:\tmp"
           "Dev Drive ready in $([int]$sw.Elapsed.TotalSeconds)s"
           Get-Volume -DriveLetter R | Format-Table -AutoSize
+          Get-Item -LiteralPath $env:GITHUB_WORKSPACE | Format-List FullName, Attributes, LinkType, Target
+
+      - name: Suppress disk cache flushes
+        if: ${{ matrix.variant == 'noflush' }}
+        shell: pwsh
+        run: |
+          Add-Type -TypeDefinition @'
+          using System;
+          using System.ComponentModel;
+          using System.Runtime.InteropServices;
+          using Microsoft.Win32.SafeHandles;
+          public static class DiskCache {
+            [StructLayout(LayoutKind.Sequential)]
+            public struct DISK_CACHE_SETTING { public uint Version; public int State; [MarshalAs(UnmanagedType.U1)] public bool IsPowerProtected; }
+            [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
+            static extern SafeFileHandle CreateFile(string name, uint access, uint share, IntPtr sa, uint disposition, uint flags, IntPtr template);
+            [DllImport("kernel32.dll", SetLastError = true)]
+            static extern bool DeviceIoControl(SafeFileHandle h, uint code, ref DISK_CACHE_SETTING inBuf, int inSize, ref DISK_CACHE_SETTING outBuf, int outSize, out int returned, IntPtr overlapped);
+            public static string SetPowerProtected(int disk) {
+              using (var h = CreateFile(@"\\.\PhysicalDrive" + disk, 0xC0000000, 3, IntPtr.Zero, 3, 0, IntPtr.Zero)) {
+                if (h.IsInvalid) { throw new Win32Exception(); }
+                var s = new DISK_CACHE_SETTING();
+                int size = Marshal.SizeOf(typeof(DISK_CACHE_SETTING));
+                int r;
+                if (!DeviceIoControl(h, 0x740E0, ref s, 0, ref s, size, out r, IntPtr.Zero)) { throw new Win32Exception(); }
+                string before = "version=" + s.Version + " state=" + s.State + " powerProtected=" + s.IsPowerProtected;
+                s.Version = (uint)size;
+                s.IsPowerProtected = true;
+                if (!DeviceIoControl(h, 0x7C0E4, ref s, size, ref s, 0, out r, IntPtr.Zero)) { throw new Win32Exception(); }
+                return before;
+              }
+            }
+          }
+          '@
+          function Test-Fsync([string] $Root) {
+            $dir = Join-Path $Root "fsbench-$([guid]::NewGuid().ToString('N'))"
+            New-Item -ItemType Directory -Path $dir | Out-Null
+            $bytes = [byte[]]::new(4096)
+            $sw = [Diagnostics.Stopwatch]::StartNew()
+            for ($i = 0; $i -lt 300; $i++) { $fs = [IO.File]::Open("$dir\s$i", 'Create'); $fs.Write($bytes, 0, 4096); $fs.Flush($true); $fs.Dispose() }
+            $fsync = $sw.Elapsed.TotalMilliseconds / 300
+            $sw.Restart()
+            for ($i = 0; $i -lt 5000; $i++) { [IO.File]::WriteAllBytes("$dir\f$i", $bytes) }
+            $create = $sw.Elapsed.TotalMilliseconds / 5000
+            Remove-Item -LiteralPath $dir -Recurse -Force
+            'fsync {0:N2} ms/file, create {1:N3} ms/file' -f $fsync, $create
+          }
+          "Before: $(Test-Fsync $env:RUNNER_TEMP)"
+          $disk = (Get-Partition -DriveLetter C).DiskNumber
+          "Disk $disk cache setting before: $([DiskCache]::SetPowerProtected($disk))"
+          Get-PhysicalDisk | ForEach-Object { Get-StorageAdvancedProperty -PhysicalDisk $_ } | Format-Table -AutoSize
+          "After: $(Test-Fsync $env:RUNNER_TEMP)"
+
+      - name: Checkout microsoft/vscode
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          lfs: true
 
       - name: Setup Node.js
         uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v7.0.0
diff --git a/.github/workflows/tmp-runner-spawn-diagnostics.yml b/.github/workflows/tmp-runner-spawn-diagnostics.yml
deleted file mode 100644
index a213a5e31ac697..00000000000000
--- a/.github/workflows/tmp-runner-spawn-diagnostics.yml
+++ /dev/null
@@ -1,49 +0,0 @@
-name: TEMP Runner Spawn Diagnostics
-
-on: pull_request
-
-permissions:
-  contents: read
-
-jobs:
-  diagnose:
-    name: Spawn (${{ matrix.name }})
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          - name: large-8-core
-            runner: vscode-large-runners-windows-8-core
-          - name: windows-latest
-            runner: windows-latest
-          - name: 1es
-            runner: 1es
-    runs-on: ${{ matrix.runner == '1es' && fromJSON(format('["self-hosted", "1ES.Pool=1es-vscode-oss-windows-2022-x64", "JobId=spawn-{0}-{1}"]', github.run_id, github.run_attempt)) || matrix.runner }}
-    steps:
-      - name: Diagnose
-        shell: pwsh
-        run: |
-          $dg = Get-CimInstance -ClassName Win32_DeviceGuard -Namespace root\Microsoft\Windows\DeviceGuard
-          "VBS status: $($dg.VirtualizationBasedSecurityStatus) (0 off, 1 enabled, 2 running)"
-          "Security services running: $($dg.SecurityServicesRunning -join ',') (1 Credential Guard, 2 HVCI)"
-          "Security services configured: $($dg.SecurityServicesConfigured -join ',')"
-          "Hypervisor present: $((Get-CimInstance Win32_ComputerSystem).HypervisorPresent)"
-          (Get-CimInstance Win32_ComputerSystem).Model
-          $node = (Get-Command node).Source
-          "node: $node"
-          foreach ($target in @('cmd.exe', $node)) {
-            for ($round = 0; $round -lt 2; $round++) {
-              $times = @(for ($i = 0; $i -lt 20; $i++) {
-                $sw = [Diagnostics.Stopwatch]::StartNew()
-                if ($target -eq 'cmd.exe') { cmd.exe /c exit 0 } else { & $target -e 0 }
-                $sw.Elapsed.TotalMilliseconds
-              }) | Sort-Object
-              '{0} round {1}: median {2:N1} ms, min {3:N1} ms' -f (Split-Path -Leaf $target), $round, $times[10], $times[0]
-            }
-          }
-          $sw = [Diagnostics.Stopwatch]::StartNew()
-          $x = 0; for ($i = 0; $i -lt 20000000; $i++) { $x += $i }
-          'CPU loop: {0:N0} ms' -f $sw.Elapsed.TotalMilliseconds
-          $sw = [Diagnostics.Stopwatch]::StartNew()
-          node -e "let s=0; for (let i=0;i<3e8;i++) s+=i; console.log(s)" | Out-Null
-          'node CPU loop: {0:N0} ms' -f $sw.Elapsed.TotalMilliseconds

From 186e38463121cf6f1c2f46e8ce859e62577acb7f Mon Sep 17 00:00:00 2001
From: Michael Lively <milively@microsoft.com>
Date: Tue, 20 Oct 2026 19:24:12 -0700
Subject: [PATCH 06/10] ci: TEMP mount the Dev Drive above the workspace

Temporary; will be removed before the PR is ready.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .../workflows/tmp-agent-host-e2e-windows-experiments.yml | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/tmp-agent-host-e2e-windows-experiments.yml b/.github/workflows/tmp-agent-host-e2e-windows-experiments.yml
index c6e19aebc14c86..1ca5cc1702a793 100644
--- a/.github/workflows/tmp-agent-host-e2e-windows-experiments.yml
+++ b/.github/workflows/tmp-agent-host-e2e-windows-experiments.yml
@@ -37,13 +37,18 @@ jobs:
           fsutil devdrv query R: 2>&1
           New-Item -ItemType Directory -Force -Path $env:GITHUB_WORKSPACE | Out-Null
           if (Get-ChildItem -Force -LiteralPath $env:GITHUB_WORKSPACE) { throw 'Workspace is not empty' }
-          Add-PartitionAccessPath -DriveLetter R -AccessPath $env:GITHUB_WORKSPACE
+          # Mount the volume above the workspace so that actions/checkout does not try to clean the volume root.
+          $parent = Split-Path -Parent $env:GITHUB_WORKSPACE
+          if (@(Get-ChildItem -Force -LiteralPath $parent).Count -ne 1) { throw 'Workspace parent has other entries' }
+          Remove-Item -LiteralPath $env:GITHUB_WORKSPACE
+          Add-PartitionAccessPath -DriveLetter R -AccessPath $parent
+          New-Item -ItemType Directory -Path $env:GITHUB_WORKSPACE | Out-Null
           New-Item -ItemType Directory -Path R:\tmp | Out-Null
           Add-Content -Path $env:GITHUB_ENV -Value "TEMP=R:\tmp"
           Add-Content -Path $env:GITHUB_ENV -Value "TMP=R:\tmp"
           "Dev Drive ready in $([int]$sw.Elapsed.TotalSeconds)s"
           Get-Volume -DriveLetter R | Format-Table -AutoSize
-          Get-Item -LiteralPath $env:GITHUB_WORKSPACE | Format-List FullName, Attributes, LinkType, Target
+          Get-Item -LiteralPath $parent | Format-List FullName, Attributes, LinkType, Target
 
       - name: Suppress disk cache flushes
         if: ${{ matrix.variant == 'noflush' }}

From b82e2ae6e000988534612199335cb9073e194ab9 Mon Sep 17 00:00:00 2001
From: Michael Lively <milively@microsoft.com>
Date: Tue, 20 Oct 2026 19:49:40 -0700
Subject: [PATCH 07/10] ci: TEMP attribute Agent Host E2E disk I/O on Windows

Temporary; will be removed before the PR is ready.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 ...tmp-agent-host-e2e-windows-experiments.yml | 131 +++++++-----------
 1 file changed, 53 insertions(+), 78 deletions(-)

diff --git a/.github/workflows/tmp-agent-host-e2e-windows-experiments.yml b/.github/workflows/tmp-agent-host-e2e-windows-experiments.yml
index 1ca5cc1702a793..b9662533c1d97d 100644
--- a/.github/workflows/tmp-agent-host-e2e-windows-experiments.yml
+++ b/.github/workflows/tmp-agent-host-e2e-windows-experiments.yml
@@ -12,94 +12,45 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - name: large-devdrive-workspace
+          - name: large-devdrive-temp
             runner: vscode-large-runners-windows-8-core
-            variant: devdrive
-            jobs: ''
-          - name: large-noflush
+            variant: devdrive-temp
+          - name: large-devdrive-workspace
             runner: vscode-large-runners-windows-8-core
-            variant: noflush
-            jobs: ''
-    runs-on: ${{ matrix.runner }}
+            variant: devdrive-workspace
+          - name: 1es-control
+            runner: 1es
+            variant: control
+    runs-on: ${{ matrix.runner == '1es' && fromJSON(format('["self-hosted", "1ES.Pool=1es-vscode-oss-windows-2022-x64", "JobId=ahexp3-{0}-{1}"]', github.run_id, github.run_attempt)) || matrix.runner }}
     env:
       VSCODE_ARCH: x64
       VSCODE_SKIP_PRELAUNCH: '1'
     steps:
-      - name: Mount Dev Drive at the workspace and TEMP
-        if: ${{ matrix.variant == 'devdrive' }}
+      - name: Create Dev Drive
+        if: ${{ matrix.variant != 'control' }}
+        working-directory: ${{ runner.temp }}
         shell: pwsh
         run: |
           $sw = [Diagnostics.Stopwatch]::StartNew()
           $script = Join-Path $env:RUNNER_TEMP 'devdrive.txt'
           "create vdisk file=`"C:\devdrive.vhdx`" maximum=102400 type=expandable`nattach vdisk`ncreate partition primary`nassign letter=R" | Out-File -Encoding ascii $script
-          diskpart /s $script
+          diskpart /s $script | Out-Null
           Format-Volume -DriveLetter R -DevDrive -Confirm:$false -Force | Out-Null
-          fsutil devdrv query R: 2>&1
-          New-Item -ItemType Directory -Force -Path $env:GITHUB_WORKSPACE | Out-Null
-          if (Get-ChildItem -Force -LiteralPath $env:GITHUB_WORKSPACE) { throw 'Workspace is not empty' }
-          # Mount the volume above the workspace so that actions/checkout does not try to clean the volume root.
-          $parent = Split-Path -Parent $env:GITHUB_WORKSPACE
-          if (@(Get-ChildItem -Force -LiteralPath $parent).Count -ne 1) { throw 'Workspace parent has other entries' }
-          Remove-Item -LiteralPath $env:GITHUB_WORKSPACE
-          Add-PartitionAccessPath -DriveLetter R -AccessPath $parent
-          New-Item -ItemType Directory -Path $env:GITHUB_WORKSPACE | Out-Null
           New-Item -ItemType Directory -Path R:\tmp | Out-Null
           Add-Content -Path $env:GITHUB_ENV -Value "TEMP=R:\tmp"
           Add-Content -Path $env:GITHUB_ENV -Value "TMP=R:\tmp"
-          "Dev Drive ready in $([int]$sw.Elapsed.TotalSeconds)s"
-          Get-Volume -DriveLetter R | Format-Table -AutoSize
-          Get-Item -LiteralPath $parent | Format-List FullName, Attributes, LinkType, Target
-
-      - name: Suppress disk cache flushes
-        if: ${{ matrix.variant == 'noflush' }}
-        shell: pwsh
-        run: |
-          Add-Type -TypeDefinition @'
-          using System;
-          using System.ComponentModel;
-          using System.Runtime.InteropServices;
-          using Microsoft.Win32.SafeHandles;
-          public static class DiskCache {
-            [StructLayout(LayoutKind.Sequential)]
-            public struct DISK_CACHE_SETTING { public uint Version; public int State; [MarshalAs(UnmanagedType.U1)] public bool IsPowerProtected; }
-            [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
-            static extern SafeFileHandle CreateFile(string name, uint access, uint share, IntPtr sa, uint disposition, uint flags, IntPtr template);
-            [DllImport("kernel32.dll", SetLastError = true)]
-            static extern bool DeviceIoControl(SafeFileHandle h, uint code, ref DISK_CACHE_SETTING inBuf, int inSize, ref DISK_CACHE_SETTING outBuf, int outSize, out int returned, IntPtr overlapped);
-            public static string SetPowerProtected(int disk) {
-              using (var h = CreateFile(@"\\.\PhysicalDrive" + disk, 0xC0000000, 3, IntPtr.Zero, 3, 0, IntPtr.Zero)) {
-                if (h.IsInvalid) { throw new Win32Exception(); }
-                var s = new DISK_CACHE_SETTING();
-                int size = Marshal.SizeOf(typeof(DISK_CACHE_SETTING));
-                int r;
-                if (!DeviceIoControl(h, 0x740E0, ref s, 0, ref s, size, out r, IntPtr.Zero)) { throw new Win32Exception(); }
-                string before = "version=" + s.Version + " state=" + s.State + " powerProtected=" + s.IsPowerProtected;
-                s.Version = (uint)size;
-                s.IsPowerProtected = true;
-                if (!DeviceIoControl(h, 0x7C0E4, ref s, size, ref s, 0, out r, IntPtr.Zero)) { throw new Win32Exception(); }
-                return before;
-              }
-            }
+          if ($env:VARIANT -eq 'devdrive-workspace') {
+            # Mount the volume above the workspace so that actions/checkout does not clean the volume root.
+            $parent = Split-Path -Parent $env:GITHUB_WORKSPACE
+            Get-ChildItem -Force -LiteralPath $parent | Format-Table FullName
+            Remove-Item -LiteralPath $env:GITHUB_WORKSPACE
+            if (Get-ChildItem -Force -LiteralPath $parent) { throw 'Workspace parent is not empty' }
+            Add-PartitionAccessPath -DriveLetter R -AccessPath $parent
+            New-Item -ItemType Directory -Path $env:GITHUB_WORKSPACE | Out-Null
           }
-          '@
-          function Test-Fsync([string] $Root) {
-            $dir = Join-Path $Root "fsbench-$([guid]::NewGuid().ToString('N'))"
-            New-Item -ItemType Directory -Path $dir | Out-Null
-            $bytes = [byte[]]::new(4096)
-            $sw = [Diagnostics.Stopwatch]::StartNew()
-            for ($i = 0; $i -lt 300; $i++) { $fs = [IO.File]::Open("$dir\s$i", 'Create'); $fs.Write($bytes, 0, 4096); $fs.Flush($true); $fs.Dispose() }
-            $fsync = $sw.Elapsed.TotalMilliseconds / 300
-            $sw.Restart()
-            for ($i = 0; $i -lt 5000; $i++) { [IO.File]::WriteAllBytes("$dir\f$i", $bytes) }
-            $create = $sw.Elapsed.TotalMilliseconds / 5000
-            Remove-Item -LiteralPath $dir -Recurse -Force
-            'fsync {0:N2} ms/file, create {1:N3} ms/file' -f $fsync, $create
-          }
-          "Before: $(Test-Fsync $env:RUNNER_TEMP)"
-          $disk = (Get-Partition -DriveLetter C).DiskNumber
-          "Disk $disk cache setting before: $([DiskCache]::SetPowerProtected($disk))"
-          Get-PhysicalDisk | ForEach-Object { Get-StorageAdvancedProperty -PhysicalDisk $_ } | Format-Table -AutoSize
-          "After: $(Test-Fsync $env:RUNNER_TEMP)"
+          "Dev Drive ready in $([int]$sw.Elapsed.TotalSeconds)s"
+        env:
+          VARIANT: ${{ matrix.variant }}
 
       - name: Checkout microsoft/vscode
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
@@ -133,19 +84,43 @@ jobs:
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
-      - name: Run Agent Host E2E tests with performance counters
+      - name: Run Agent Host E2E tests with I/O attribution
         timeout-minutes: 45
         shell: pwsh
         run: |
           $csv = Join-Path $env:RUNNER_TEMP 'perf.csv'
-          $counters = @('\PhysicalDisk(_Total)\Avg. Disk sec/Write', '\PhysicalDisk(_Total)\Avg. Disk sec/Read', '\PhysicalDisk(_Total)\Disk Transfers/sec', '\PhysicalDisk(_Total)\Current Disk Queue Length', '\Processor(_Total)\% Processor Time', '\Memory\Available MBytes', '\System\Processor Queue Length')
+          $counters = @('\PhysicalDisk(_Total)\Avg. Disk sec/Write', '\PhysicalDisk(_Total)\Disk Writes/sec', '\PhysicalDisk(_Total)\Disk Write Bytes/sec', '\PhysicalDisk(_Total)\Disk Read Bytes/sec', '\PhysicalDisk(_Total)\Avg. Disk Bytes/Write', '\PhysicalDisk(_Total)\Current Disk Queue Length', '\Processor(_Total)\% Processor Time')
           $perf = Start-Process typeperf -ArgumentList (@($counters | ForEach-Object { "`"$_`"" }) + @('-si', '5', '-f', 'CSV', '-o', "`"$csv`"", '-y')) -PassThru -WindowStyle Hidden
-          "TEMP=$env:TEMP"
+          $stop = Join-Path $env:RUNNER_TEMP 'sampler.stop'
+          $out = Join-Path $env:RUNNER_TEMP 'sampler.csv'
+          $sampler = Join-Path $env:RUNNER_TEMP 'sampler.ps1'
+          @'
+          param($Stop, $Out)
+          $seen = @{}
+          while (-not (Test-Path $Stop)) {
+            foreach ($p in Get-CimInstance Win32_Process -Property ProcessId, Name, CreationDate, WriteTransferCount, WriteOperationCount, ReadTransferCount) {
+              $seen["$($p.ProcessId)|$($p.CreationDate)"] = $p
+            }
+            Start-Sleep -Milliseconds 1000
+          }
+          $seen.Values | Group-Object Name | ForEach-Object {
+            [pscustomobject]@{
+              Name = $_.Name; Processes = $_.Count
+              WriteMB = [math]::Round(($_.Group | Measure-Object WriteTransferCount -Sum).Sum / 1MB)
+              WriteOps = ($_.Group | Measure-Object WriteOperationCount -Sum).Sum
+              ReadMB = [math]::Round(($_.Group | Measure-Object ReadTransferCount -Sum).Sum / 1MB)
+            }
+          } | Sort-Object WriteMB -Descending | Export-Csv -NoTypeInformation $Out
+          '@ | Set-Content -Path $sampler
+          $samplerProcess = Start-Process pwsh -ArgumentList @('-NoProfile', '-File', $sampler, $stop, $out) -PassThru -WindowStyle Hidden
+          "TEMP=$env:TEMP WORKSPACE=$((Get-Item .).FullName)"
           $sw = [Diagnostics.Stopwatch]::StartNew()
-          .\scripts\test-agent-host-e2e.bat --tfs "Integration Tests" $(if ($env:EXTRA_ARGS) { $env:EXTRA_ARGS -split ' ' })
+          .\scripts\test-agent-host-e2e.bat --tfs "Integration Tests"
           $exitCode = $LASTEXITCODE
           "Agent Host E2E exit code $exitCode after $([math]::Round($sw.Elapsed.TotalMinutes, 1)) min"
           Stop-Process -Id $perf.Id -Force -ErrorAction SilentlyContinue
+          New-Item -ItemType File -Path $stop | Out-Null
+          $samplerProcess.WaitForExit(60000) | Out-Null
           Start-Sleep -Seconds 2
           $rows = Import-Csv $csv
           $columns = $rows[0].PSObject.Properties.Name | Select-Object -Skip 1
@@ -154,11 +129,11 @@ jobs:
             if ($values.Count -eq 0) { continue }
             $avg = ($values | Measure-Object -Average).Average
             $p95 = $values[[math]::Min($values.Count - 1, [math]::Floor($values.Count * 0.95))]
-            '{0,-70} avg {1,12:N4}  p95 {2,12:N4}  max {3,12:N4}' -f ($column -replace '^\\\\[^\\]+', ''), $avg, $p95, $values[-1]
+            'COUNTER {0,-60} avg {1,14:N3}  p95 {2,14:N3}  max {3,14:N3}' -f ($column -replace '^\\\\[^\\]+', ''), $avg, $p95, $values[-1]
           }
+          Import-Csv $out | Select-Object -First 15 | ForEach-Object { 'WRITER {0,-30} n={1,5} writeMB={2,8} writeOps={3,10} readMB={4,8}' -f $_.Name, $_.Processes, $_.WriteMB, $_.WriteOps, $_.ReadMB }
           exit $exitCode
         env:
-          EXTRA_ARGS: ${{ matrix.jobs }}
           VSCODE_SKIP_AGENT_HOST_E2E: '0'
           AGENT_HOST_TEST_PROFILE: full
           AGENT_HOST_TEST_PROFILE_REASON: Windows runner experiment

From 4e1b5a41e5db5d96fa237f8b539f320cef306c6b Mon Sep 17 00:00:00 2001
From: Michael Lively <milively@microsoft.com>
Date: Tue, 20 Oct 2026 20:31:59 -0700
Subject: [PATCH 08/10] ci: TEMP check RAM disk feasibility on Windows runners

Temporary; will be removed before the PR is ready.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 ...tmp-agent-host-e2e-windows-experiments.yml | 139 ------------------
 .github/workflows/tmp-ramdisk-feasibility.yml |  62 ++++++++
 2 files changed, 62 insertions(+), 139 deletions(-)
 delete mode 100644 .github/workflows/tmp-agent-host-e2e-windows-experiments.yml
 create mode 100644 .github/workflows/tmp-ramdisk-feasibility.yml

diff --git a/.github/workflows/tmp-agent-host-e2e-windows-experiments.yml b/.github/workflows/tmp-agent-host-e2e-windows-experiments.yml
deleted file mode 100644
index b9662533c1d97d..00000000000000
--- a/.github/workflows/tmp-agent-host-e2e-windows-experiments.yml
+++ /dev/null
@@ -1,139 +0,0 @@
-name: TEMP Agent Host E2E Windows Experiments
-
-on: pull_request
-
-permissions:
-  contents: read
-
-jobs:
-  experiment:
-    name: AH E2E (${{ matrix.name }})
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          - name: large-devdrive-temp
-            runner: vscode-large-runners-windows-8-core
-            variant: devdrive-temp
-          - name: large-devdrive-workspace
-            runner: vscode-large-runners-windows-8-core
-            variant: devdrive-workspace
-          - name: 1es-control
-            runner: 1es
-            variant: control
-    runs-on: ${{ matrix.runner == '1es' && fromJSON(format('["self-hosted", "1ES.Pool=1es-vscode-oss-windows-2022-x64", "JobId=ahexp3-{0}-{1}"]', github.run_id, github.run_attempt)) || matrix.runner }}
-    env:
-      VSCODE_ARCH: x64
-      VSCODE_SKIP_PRELAUNCH: '1'
-    steps:
-      - name: Create Dev Drive
-        if: ${{ matrix.variant != 'control' }}
-        working-directory: ${{ runner.temp }}
-        shell: pwsh
-        run: |
-          $sw = [Diagnostics.Stopwatch]::StartNew()
-          $script = Join-Path $env:RUNNER_TEMP 'devdrive.txt'
-          "create vdisk file=`"C:\devdrive.vhdx`" maximum=102400 type=expandable`nattach vdisk`ncreate partition primary`nassign letter=R" | Out-File -Encoding ascii $script
-          diskpart /s $script | Out-Null
-          Format-Volume -DriveLetter R -DevDrive -Confirm:$false -Force | Out-Null
-          New-Item -ItemType Directory -Path R:\tmp | Out-Null
-          Add-Content -Path $env:GITHUB_ENV -Value "TEMP=R:\tmp"
-          Add-Content -Path $env:GITHUB_ENV -Value "TMP=R:\tmp"
-          if ($env:VARIANT -eq 'devdrive-workspace') {
-            # Mount the volume above the workspace so that actions/checkout does not clean the volume root.
-            $parent = Split-Path -Parent $env:GITHUB_WORKSPACE
-            Get-ChildItem -Force -LiteralPath $parent | Format-Table FullName
-            Remove-Item -LiteralPath $env:GITHUB_WORKSPACE
-            if (Get-ChildItem -Force -LiteralPath $parent) { throw 'Workspace parent is not empty' }
-            Add-PartitionAccessPath -DriveLetter R -AccessPath $parent
-            New-Item -ItemType Directory -Path $env:GITHUB_WORKSPACE | Out-Null
-          }
-          "Dev Drive ready in $([int]$sw.Elapsed.TotalSeconds)s"
-        env:
-          VARIANT: ${{ matrix.variant }}
-
-      - name: Checkout microsoft/vscode
-        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-        with:
-          lfs: true
-
-      - name: Setup Node.js
-        uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v7.0.0
-        with:
-          node-version-file: .nvmrc
-
-      - name: Restore node_modules cache
-        id: cache-node-modules
-        uses: ./.github/actions/restore-node-modules
-        with:
-          key-prefix: node_modules-windows
-          key-args: "win32 ${{ env.VSCODE_ARCH }} $(node -p process.arch)"
-
-      - name: Fail on node_modules cache miss
-        if: steps.cache-node-modules.outputs.cache-hit != 'true'
-        run: exit 1
-
-      - name: Transpile client and extensions
-        shell: pwsh
-        run: npm run gulp "transpile-client-esbuild" "transpile-extensions"
-
-      - name: Setup Electron
-        uses: ./.github/actions/setup-electron
-        with:
-          arch: ${{ env.VSCODE_ARCH }}
-        env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-
-      - name: Run Agent Host E2E tests with I/O attribution
-        timeout-minutes: 45
-        shell: pwsh
-        run: |
-          $csv = Join-Path $env:RUNNER_TEMP 'perf.csv'
-          $counters = @('\PhysicalDisk(_Total)\Avg. Disk sec/Write', '\PhysicalDisk(_Total)\Disk Writes/sec', '\PhysicalDisk(_Total)\Disk Write Bytes/sec', '\PhysicalDisk(_Total)\Disk Read Bytes/sec', '\PhysicalDisk(_Total)\Avg. Disk Bytes/Write', '\PhysicalDisk(_Total)\Current Disk Queue Length', '\Processor(_Total)\% Processor Time')
-          $perf = Start-Process typeperf -ArgumentList (@($counters | ForEach-Object { "`"$_`"" }) + @('-si', '5', '-f', 'CSV', '-o', "`"$csv`"", '-y')) -PassThru -WindowStyle Hidden
-          $stop = Join-Path $env:RUNNER_TEMP 'sampler.stop'
-          $out = Join-Path $env:RUNNER_TEMP 'sampler.csv'
-          $sampler = Join-Path $env:RUNNER_TEMP 'sampler.ps1'
-          @'
-          param($Stop, $Out)
-          $seen = @{}
-          while (-not (Test-Path $Stop)) {
-            foreach ($p in Get-CimInstance Win32_Process -Property ProcessId, Name, CreationDate, WriteTransferCount, WriteOperationCount, ReadTransferCount) {
-              $seen["$($p.ProcessId)|$($p.CreationDate)"] = $p
-            }
-            Start-Sleep -Milliseconds 1000
-          }
-          $seen.Values | Group-Object Name | ForEach-Object {
-            [pscustomobject]@{
-              Name = $_.Name; Processes = $_.Count
-              WriteMB = [math]::Round(($_.Group | Measure-Object WriteTransferCount -Sum).Sum / 1MB)
-              WriteOps = ($_.Group | Measure-Object WriteOperationCount -Sum).Sum
-              ReadMB = [math]::Round(($_.Group | Measure-Object ReadTransferCount -Sum).Sum / 1MB)
-            }
-          } | Sort-Object WriteMB -Descending | Export-Csv -NoTypeInformation $Out
-          '@ | Set-Content -Path $sampler
-          $samplerProcess = Start-Process pwsh -ArgumentList @('-NoProfile', '-File', $sampler, $stop, $out) -PassThru -WindowStyle Hidden
-          "TEMP=$env:TEMP WORKSPACE=$((Get-Item .).FullName)"
-          $sw = [Diagnostics.Stopwatch]::StartNew()
-          .\scripts\test-agent-host-e2e.bat --tfs "Integration Tests"
-          $exitCode = $LASTEXITCODE
-          "Agent Host E2E exit code $exitCode after $([math]::Round($sw.Elapsed.TotalMinutes, 1)) min"
-          Stop-Process -Id $perf.Id -Force -ErrorAction SilentlyContinue
-          New-Item -ItemType File -Path $stop | Out-Null
-          $samplerProcess.WaitForExit(60000) | Out-Null
-          Start-Sleep -Seconds 2
-          $rows = Import-Csv $csv
-          $columns = $rows[0].PSObject.Properties.Name | Select-Object -Skip 1
-          foreach ($column in $columns) {
-            $values = @($rows | ForEach-Object { $_.$column } | Where-Object { $_ -and $_.Trim() } | ForEach-Object { [double]$_ } | Sort-Object)
-            if ($values.Count -eq 0) { continue }
-            $avg = ($values | Measure-Object -Average).Average
-            $p95 = $values[[math]::Min($values.Count - 1, [math]::Floor($values.Count * 0.95))]
-            'COUNTER {0,-60} avg {1,14:N3}  p95 {2,14:N3}  max {3,14:N3}' -f ($column -replace '^\\\\[^\\]+', ''), $avg, $p95, $values[-1]
-          }
-          Import-Csv $out | Select-Object -First 15 | ForEach-Object { 'WRITER {0,-30} n={1,5} writeMB={2,8} writeOps={3,10} readMB={4,8}' -f $_.Name, $_.Processes, $_.WriteMB, $_.WriteOps, $_.ReadMB }
-          exit $exitCode
-        env:
-          VSCODE_SKIP_AGENT_HOST_E2E: '0'
-          AGENT_HOST_TEST_PROFILE: full
-          AGENT_HOST_TEST_PROFILE_REASON: Windows runner experiment
diff --git a/.github/workflows/tmp-ramdisk-feasibility.yml b/.github/workflows/tmp-ramdisk-feasibility.yml
new file mode 100644
index 00000000000000..4c3592473bfb3d
--- /dev/null
+++ b/.github/workflows/tmp-ramdisk-feasibility.yml
@@ -0,0 +1,62 @@
+name: TEMP RAM Disk Feasibility
+
+on: pull_request
+
+permissions:
+  contents: read
+
+jobs:
+  ramdisk:
+    name: RAM disk (large-8-core)
+    runs-on: vscode-large-runners-windows-8-core
+    steps:
+      - name: Create RAM disk
+        shell: pwsh
+        run: |
+          $ErrorActionPreference = 'Stop'
+          $sw = [Diagnostics.Stopwatch]::StartNew()
+          $feature = Install-WindowsFeature -Name FS-iSCSITarget-Server
+          "Install-WindowsFeature: success=$($feature.Success) restart=$($feature.RestartNeeded) after $([int]$sw.Elapsed.TotalSeconds)s"
+          Set-Service -Name MSiSCSI -StartupType Automatic
+          Start-Service -Name MSiSCSI
+          $initiator = (Get-InitiatorPort | Select-Object -First 1).NodeAddress
+          "Initiator: $initiator"
+          New-IscsiVirtualDisk -Path 'ramdisk:vscode-test.vhdx' -Size 16GB | Out-Null
+          New-IscsiServerTarget -TargetName vscode-test -InitiatorIds "IQN:$initiator" | Out-Null
+          Add-IscsiVirtualDiskTargetMapping -TargetName vscode-test -Path 'ramdisk:vscode-test.vhdx'
+          New-IscsiTargetPortal -TargetPortalAddress 127.0.0.1 | Out-Null
+          $target = Get-IscsiTarget | Where-Object NodeAddress -like '*vscode-test*'
+          Connect-IscsiTarget -NodeAddress $target.NodeAddress | Out-Null
+          $disk = $null
+          for ($i = 0; $i -lt 30 -and -not $disk; $i++) { $disk = Get-Disk | Where-Object BusType -eq 'iSCSI'; if (-not $disk) { Start-Sleep 1 } }
+          $disk | Initialize-Disk -PartitionStyle GPT -PassThru | New-Partition -DriveLetter T -UseMaximumSize | Format-Volume -FileSystem NTFS -Confirm:$false -Force | Out-Null
+          "RAM disk ready after $([int]$sw.Elapsed.TotalSeconds)s"
+          Get-Volume -DriveLetter T | Format-Table -AutoSize
+          Get-PhysicalDisk | Format-Table DeviceId, FriendlyName, BusType, Size -AutoSize
+
+      - name: Benchmark
+        shell: pwsh
+        run: |
+          function Test-Directory([string] $Root) {
+            $dir = Join-Path $Root "fsbench-$([guid]::NewGuid().ToString('N'))"
+            New-Item -ItemType Directory -Path $dir | Out-Null
+            $bytes = [byte[]]::new(9000)
+            $jobs = 1..6 | ForEach-Object {
+              Start-ThreadJob -ArgumentList $dir, $_ -ScriptBlock {
+                param($dir, $n)
+                $bytes = [byte[]]::new(9000)
+                $sw = [Diagnostics.Stopwatch]::StartNew()
+                for ($i = 0; $i -lt 300; $i++) { $fs = [IO.File]::Open("$dir\s$n-$i", 'Create'); $fs.Write($bytes, 0, $bytes.Length); $fs.Flush($true); $fs.Dispose() }
+                $sw.Elapsed.TotalMilliseconds / 300
+              }
+            }
+            $fsync = ($jobs | Receive-Job -Wait -AutoRemoveJob | Measure-Object -Average).Average
+            $sw = [Diagnostics.Stopwatch]::StartNew()
+            for ($i = 0; $i -lt 5000; $i++) { [IO.File]::WriteAllBytes("$dir\f$i", $bytes) }
+            $create = $sw.Elapsed.TotalMilliseconds / 5000
+            Remove-Item -LiteralPath $dir -Recurse -Force
+            '{0,-40} 6x parallel write+fsync {1,7:N2} ms/file | create {2,6:N3} ms/file' -f $Root, $fsync, $create
+          }
+          Test-Directory $env:RUNNER_TEMP
+          Test-Directory $env:GITHUB_WORKSPACE
+          Test-Directory 'T:\'

From 4eaff64759439046def2506f088fb25fd3256f59 Mon Sep 17 00:00:00 2001
From: Michael Lively <milively@microsoft.com>
Date: Tue, 20 Oct 2026 20:36:56 -0700
Subject: [PATCH 09/10] ci: TEMP force node_modules cache misses to validate
 npm ci

Remove the temporary diagnostics workflow and change the node_modules
cache key prefixes so that every job installs dependencies on the new
runners. Will be reverted before the PR is ready.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .github/workflows/pr-linux-test.yml           |  2 +-
 .github/workflows/pr-win32-test.yml           |  2 +-
 .github/workflows/pr.yml                      |  8 +--
 .github/workflows/tmp-ramdisk-feasibility.yml | 62 -------------------
 4 files changed, 6 insertions(+), 68 deletions(-)
 delete mode 100644 .github/workflows/tmp-ramdisk-feasibility.yml

diff --git a/.github/workflows/pr-linux-test.yml b/.github/workflows/pr-linux-test.yml
index 716dd03c487eb0..9fbf3e8683e2f7 100644
--- a/.github/workflows/pr-linux-test.yml
+++ b/.github/workflows/pr-linux-test.yml
@@ -84,7 +84,7 @@ jobs:
         id: cache-node-modules
         uses: ./.github/actions/restore-node-modules
         with:
-          key-prefix: node_modules-linux
+          key-prefix: node_modules-linux-validate-miss
           key-args: "linux ${{ env.VSCODE_ARCH }} $(node -p process.arch)"
 
       - name: Install build dependencies
diff --git a/.github/workflows/pr-win32-test.yml b/.github/workflows/pr-win32-test.yml
index 8079faeb488f60..d180259ada985d 100644
--- a/.github/workflows/pr-win32-test.yml
+++ b/.github/workflows/pr-win32-test.yml
@@ -77,7 +77,7 @@ jobs:
         id: cache-node-modules
         uses: ./.github/actions/restore-node-modules
         with:
-          key-prefix: node_modules-windows
+          key-prefix: node_modules-windows-validate-miss
           key-args: "win32 ${{ env.VSCODE_ARCH }} $(node -p process.arch)"
 
       - name: Install dependencies
diff --git a/.github/workflows/pr.yml b/.github/workflows/pr.yml
index 41228cefb3f536..fc1a3d739472a1 100644
--- a/.github/workflows/pr.yml
+++ b/.github/workflows/pr.yml
@@ -63,7 +63,7 @@ jobs:
         id: cache-node-modules
         uses: ./.github/actions/restore-node-modules
         with:
-          key-prefix: node_modules-compile
+          key-prefix: node_modules-compile-validate-miss
           key-args: "compile $(node -p process.arch)"
 
       - name: Install build tools
@@ -498,7 +498,7 @@ jobs:
         id: cache-node-modules
         uses: ./.github/actions/restore-node-modules
         with:
-          key-prefix: copilot-node_modules-linux
+          key-prefix: copilot-node_modules-linux-validate-miss
           key-args: "$(node -p process.platform) $(node -p process.arch)"
 
       - name: Install root dependencies
@@ -585,7 +585,7 @@ jobs:
         id: cache-node-modules
         uses: ./.github/actions/restore-node-modules
         with:
-          key-prefix: copilot-node_modules-linux
+          key-prefix: copilot-node_modules-linux-validate-miss
           key-args: "$(node -p process.platform) $(node -p process.arch)"
 
       - name: Install root dependencies
@@ -680,7 +680,7 @@ jobs:
         id: cache-node-modules
         uses: ./.github/actions/restore-node-modules
         with:
-          key-prefix: copilot-node_modules-windows
+          key-prefix: copilot-node_modules-windows-validate-miss
           key-args: "$(node -p process.platform) $(node -p process.arch)"
 
       - name: Install root dependencies
diff --git a/.github/workflows/tmp-ramdisk-feasibility.yml b/.github/workflows/tmp-ramdisk-feasibility.yml
deleted file mode 100644
index 4c3592473bfb3d..00000000000000
--- a/.github/workflows/tmp-ramdisk-feasibility.yml
+++ /dev/null
@@ -1,62 +0,0 @@
-name: TEMP RAM Disk Feasibility
-
-on: pull_request
-
-permissions:
-  contents: read
-
-jobs:
-  ramdisk:
-    name: RAM disk (large-8-core)
-    runs-on: vscode-large-runners-windows-8-core
-    steps:
-      - name: Create RAM disk
-        shell: pwsh
-        run: |
-          $ErrorActionPreference = 'Stop'
-          $sw = [Diagnostics.Stopwatch]::StartNew()
-          $feature = Install-WindowsFeature -Name FS-iSCSITarget-Server
-          "Install-WindowsFeature: success=$($feature.Success) restart=$($feature.RestartNeeded) after $([int]$sw.Elapsed.TotalSeconds)s"
-          Set-Service -Name MSiSCSI -StartupType Automatic
-          Start-Service -Name MSiSCSI
-          $initiator = (Get-InitiatorPort | Select-Object -First 1).NodeAddress
-          "Initiator: $initiator"
-          New-IscsiVirtualDisk -Path 'ramdisk:vscode-test.vhdx' -Size 16GB | Out-Null
-          New-IscsiServerTarget -TargetName vscode-test -InitiatorIds "IQN:$initiator" | Out-Null
-          Add-IscsiVirtualDiskTargetMapping -TargetName vscode-test -Path 'ramdisk:vscode-test.vhdx'
-          New-IscsiTargetPortal -TargetPortalAddress 127.0.0.1 | Out-Null
-          $target = Get-IscsiTarget | Where-Object NodeAddress -like '*vscode-test*'
-          Connect-IscsiTarget -NodeAddress $target.NodeAddress | Out-Null
-          $disk = $null
-          for ($i = 0; $i -lt 30 -and -not $disk; $i++) { $disk = Get-Disk | Where-Object BusType -eq 'iSCSI'; if (-not $disk) { Start-Sleep 1 } }
-          $disk | Initialize-Disk -PartitionStyle GPT -PassThru | New-Partition -DriveLetter T -UseMaximumSize | Format-Volume -FileSystem NTFS -Confirm:$false -Force | Out-Null
-          "RAM disk ready after $([int]$sw.Elapsed.TotalSeconds)s"
-          Get-Volume -DriveLetter T | Format-Table -AutoSize
-          Get-PhysicalDisk | Format-Table DeviceId, FriendlyName, BusType, Size -AutoSize
-
-      - name: Benchmark
-        shell: pwsh
-        run: |
-          function Test-Directory([string] $Root) {
-            $dir = Join-Path $Root "fsbench-$([guid]::NewGuid().ToString('N'))"
-            New-Item -ItemType Directory -Path $dir | Out-Null
-            $bytes = [byte[]]::new(9000)
-            $jobs = 1..6 | ForEach-Object {
-              Start-ThreadJob -ArgumentList $dir, $_ -ScriptBlock {
-                param($dir, $n)
-                $bytes = [byte[]]::new(9000)
-                $sw = [Diagnostics.Stopwatch]::StartNew()
-                for ($i = 0; $i -lt 300; $i++) { $fs = [IO.File]::Open("$dir\s$n-$i", 'Create'); $fs.Write($bytes, 0, $bytes.Length); $fs.Flush($true); $fs.Dispose() }
-                $sw.Elapsed.TotalMilliseconds / 300
-              }
-            }
-            $fsync = ($jobs | Receive-Job -Wait -AutoRemoveJob | Measure-Object -Average).Average
-            $sw = [Diagnostics.Stopwatch]::StartNew()
-            for ($i = 0; $i -lt 5000; $i++) { [IO.File]::WriteAllBytes("$dir\f$i", $bytes) }
-            $create = $sw.Elapsed.TotalMilliseconds / 5000
-            Remove-Item -LiteralPath $dir -Recurse -Force
-            '{0,-40} 6x parallel write+fsync {1,7:N2} ms/file | create {2,6:N3} ms/file' -f $Root, $fsync, $create
-          }
-          Test-Directory $env:RUNNER_TEMP
-          Test-Directory $env:GITHUB_WORKSPACE
-          Test-Directory 'T:\'

From 6232879fa930746052d20cd962dc41337a31c15c Mon Sep 17 00:00:00 2001
From: Michael Lively <milively@microsoft.com>
Date: Tue, 20 Oct 2026 21:34:30 -0700
Subject: [PATCH 10/10] Revert "ci: TEMP force node_modules cache misses to
 validate npm ci"

The cache-miss path was validated in run 39539559733.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .github/workflows/pr-linux-test.yml | 2 +-
 .github/workflows/pr-win32-test.yml | 2 +-
 .github/workflows/pr.yml            | 8 ++++----
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/.github/workflows/pr-linux-test.yml b/.github/workflows/pr-linux-test.yml
index 9fbf3e8683e2f7..716dd03c487eb0 100644
--- a/.github/workflows/pr-linux-test.yml
+++ b/.github/workflows/pr-linux-test.yml
@@ -84,7 +84,7 @@ jobs:
         id: cache-node-modules
         uses: ./.github/actions/restore-node-modules
         with:
-          key-prefix: node_modules-linux-validate-miss
+          key-prefix: node_modules-linux
           key-args: "linux ${{ env.VSCODE_ARCH }} $(node -p process.arch)"
 
       - name: Install build dependencies
diff --git a/.github/workflows/pr-win32-test.yml b/.github/workflows/pr-win32-test.yml
index d180259ada985d..8079faeb488f60 100644
--- a/.github/workflows/pr-win32-test.yml
+++ b/.github/workflows/pr-win32-test.yml
@@ -77,7 +77,7 @@ jobs:
         id: cache-node-modules
         uses: ./.github/actions/restore-node-modules
         with:
-          key-prefix: node_modules-windows-validate-miss
+          key-prefix: node_modules-windows
           key-args: "win32 ${{ env.VSCODE_ARCH }} $(node -p process.arch)"
 
       - name: Install dependencies
diff --git a/.github/workflows/pr.yml b/.github/workflows/pr.yml
index fc1a3d739472a1..41228cefb3f536 100644
--- a/.github/workflows/pr.yml
+++ b/.github/workflows/pr.yml
@@ -63,7 +63,7 @@ jobs:
         id: cache-node-modules
         uses: ./.github/actions/restore-node-modules
         with:
-          key-prefix: node_modules-compile-validate-miss
+          key-prefix: node_modules-compile
           key-args: "compile $(node -p process.arch)"
 
       - name: Install build tools
@@ -498,7 +498,7 @@ jobs:
         id: cache-node-modules
         uses: ./.github/actions/restore-node-modules
         with:
-          key-prefix: copilot-node_modules-linux-validate-miss
+          key-prefix: copilot-node_modules-linux
           key-args: "$(node -p process.platform) $(node -p process.arch)"
 
       - name: Install root dependencies
@@ -585,7 +585,7 @@ jobs:
         id: cache-node-modules
         uses: ./.github/actions/restore-node-modules
         with:
-          key-prefix: copilot-node_modules-linux-validate-miss
+          key-prefix: copilot-node_modules-linux
           key-args: "$(node -p process.platform) $(node -p process.arch)"
 
       - name: Install root dependencies
@@ -680,7 +680,7 @@ jobs:
         id: cache-node-modules
         uses: ./.github/actions/restore-node-modules
         with:
-          key-prefix: copilot-node_modules-windows-validate-miss
+          key-prefix: copilot-node_modules-windows
           key-args: "$(node -p process.platform) $(node -p process.arch)"
 
       - name: Install root dependencies