diff --git a/.bazelrc b/.bazelrc
index de01a87443f..93fcb0c1645 100644
--- a/.bazelrc
+++ b/.bazelrc
@@ -190,7 +190,7 @@ common:ci-windows-cross --strategy=TestRunner=local
 # V8 embeds IsolateData offsets in snapshot builtins; Windows snapshots must be
 # generated by a Windows mksnapshot binary rather than the Linux RBE host tool.
 common:ci-windows-cross --strategy=V8Mksnapshot=local
-common:ci-windows-cross --local_test_jobs=4
+common:ci-windows-cross --local_test_jobs=8
 common:ci-windows-cross --test_env=RUST_TEST_THREADS=1
 # Native Windows CI still covers the PowerShell parser-process tests. The
 # cross-built gnullvm binaries currently hang in those tests when run on the
diff --git a/.github/scripts/measure-windows-bazel.ps1 b/.github/scripts/measure-windows-bazel.ps1
new file mode 100644
index 00000000000..339c9c6c2ad
--- /dev/null
+++ b/.github/scripts/measure-windows-bazel.ps1
@@ -0,0 +1,200 @@
+<#
+Collect lightweight host telemetry around Windows Bazel CI runs.
+
+The monitor mode intentionally uses built-in Windows performance counters so
+the workflow does not need to install a profiler on the runner. The summarize
+mode keeps the useful aggregate in the job log while the raw CSV remains
+available as an artifact for deeper analysis.
+#>
+
+[CmdletBinding()]
+param(
+  [Parameter(Mandatory = $true)]
+  [ValidateSet('monitor', 'summarize')]
+  [string]$Mode,
+
+  [Parameter(Mandatory = $true)]
+  [string]$OutputPath,
+
+  [string]$StopFile,
+
+  [ValidateRange(1, 60)]
+  [int]$IntervalSeconds = 15
+)
+
+Set-StrictMode -Version Latest
+$ErrorActionPreference = 'Stop'
+
+function Get-SingleCounterValue {
+  param(
+    [Parameter(Mandatory = $true)]
+    [object]$CounterSample,
+
+    [Parameter(Mandatory = $true)]
+    [string]$PathPattern
+  )
+
+  $sample = $CounterSample.CounterSamples |
+    Where-Object { $_.Path -like $PathPattern } |
+    Select-Object -First 1
+  if ($null -eq $sample) {
+    return 0
+  }
+  return [double]$sample.CookedValue
+}
+
+function Get-SummedCounterValue {
+  param(
+    [Parameter(Mandatory = $true)]
+    [object]$CounterSample,
+
+    [Parameter(Mandatory = $true)]
+    [string]$PathPattern
+  )
+
+  $samples = $CounterSample.CounterSamples |
+    Where-Object { $_.Path -like $PathPattern }
+  if ($null -eq $samples) {
+    return 0
+  }
+  return [double](($samples | Measure-Object -Property CookedValue -Sum).Sum)
+}
+
+function Get-Percentile {
+  param(
+    [Parameter(Mandatory = $true)]
+    [double[]]$Values,
+
+    [Parameter(Mandatory = $true)]
+    [ValidateRange(0, 100)]
+    [int]$Percentile
+  )
+
+  if ($Values.Count -eq 0) {
+    return 0
+  }
+  $sorted = $Values | Sort-Object
+  $index = [math]::Ceiling(($Percentile / 100) * $sorted.Count) - 1
+  return [double]$sorted[[math]::Max(0, $index)]
+}
+
+function Get-NumericColumn {
+  param(
+    [Parameter(Mandatory = $true)]
+    [object[]]$Rows,
+
+    [Parameter(Mandatory = $true)]
+    [string]$Name
+  )
+
+  return [double[]]@($Rows | ForEach-Object { [double]$_.$Name })
+}
+
+function Format-BytesPerSecond {
+  param([double]$Value)
+
+  return '{0:N1} MiB/s' -f ($Value / 1MB)
+}
+
+function Write-Summary {
+  if (-not (Test-Path -LiteralPath $OutputPath)) {
+    Write-Output "No Windows Bazel telemetry file found at $OutputPath."
+    return
+  }
+
+  $rows = @(Import-Csv -LiteralPath $OutputPath)
+  if ($rows.Count -eq 0) {
+    Write-Output "Windows Bazel telemetry file at $OutputPath had no samples."
+    return
+  }
+
+  $cpu = Get-NumericColumn -Rows $rows -Name cpu_percent
+  $processorQueue = Get-NumericColumn -Rows $rows -Name processor_queue_length
+  $diskRead = Get-NumericColumn -Rows $rows -Name disk_read_bytes_per_sec
+  $diskWrite = Get-NumericColumn -Rows $rows -Name disk_write_bytes_per_sec
+  $diskLatency = Get-NumericColumn -Rows $rows -Name disk_seconds_per_transfer
+  $diskQueue = Get-NumericColumn -Rows $rows -Name disk_queue_length
+  $networkReceived = Get-NumericColumn -Rows $rows -Name network_received_bytes_per_sec
+  $networkSent = Get-NumericColumn -Rows $rows -Name network_sent_bytes_per_sec
+  $memory = Get-NumericColumn -Rows $rows -Name available_memory_mib
+
+  $sampledSeconds = $rows.Count * $IntervalSeconds
+  $networkBytes = (($networkReceived | Measure-Object -Average).Average + ($networkSent | Measure-Object -Average).Average) * $sampledSeconds
+  $diskBytes = (($diskRead | Measure-Object -Average).Average + ($diskWrite | Measure-Object -Average).Average) * $sampledSeconds
+
+  Write-Output 'Windows Bazel host telemetry summary:'
+  Write-Output ('  samples: {0} (~{1:N0}s)' -f $rows.Count, $sampledSeconds)
+  Write-Output ('  cpu: avg {0:N1}%, p95 {1:N1}%, max {2:N1}%; processor queue max {3:N1}' -f
+    ($cpu | Measure-Object -Average).Average,
+    (Get-Percentile -Values $cpu -Percentile 95),
+    ($cpu | Measure-Object -Maximum).Maximum,
+    ($processorQueue | Measure-Object -Maximum).Maximum)
+  Write-Output ('  disk: read avg {0}, write avg {1}, p95 latency {2:N1}ms, queue max {3:N1}, sampled total {4:N2} GiB' -f
+    (Format-BytesPerSecond (($diskRead | Measure-Object -Average).Average)),
+    (Format-BytesPerSecond (($diskWrite | Measure-Object -Average).Average)),
+    ((Get-Percentile -Values $diskLatency -Percentile 95) * 1000),
+    ($diskQueue | Measure-Object -Maximum).Maximum,
+    ($diskBytes / 1GB))
+  Write-Output ('  network: receive avg {0}, send avg {1}, sampled total {2:N2} GiB' -f
+    (Format-BytesPerSecond (($networkReceived | Measure-Object -Average).Average)),
+    (Format-BytesPerSecond (($networkSent | Measure-Object -Average).Average)),
+    ($networkBytes / 1GB))
+  Write-Output ('  memory: minimum {0:N0} MiB available' -f ($memory | Measure-Object -Minimum).Minimum)
+}
+
+if ($Mode -eq 'summarize') {
+  Write-Summary
+  exit 0
+}
+
+if ([string]::IsNullOrWhiteSpace($StopFile)) {
+  throw 'monitor mode requires -StopFile.'
+}
+
+$outputDirectory = Split-Path -Parent $OutputPath
+if (-not [string]::IsNullOrWhiteSpace($outputDirectory)) {
+  New-Item -ItemType Directory -Path $outputDirectory -Force | Out-Null
+}
+
+$counterPaths = @(
+  '\Processor(_Total)\% Processor Time',
+  '\System\Processor Queue Length',
+  '\PhysicalDisk(_Total)\Disk Read Bytes/sec',
+  '\PhysicalDisk(_Total)\Disk Write Bytes/sec',
+  '\PhysicalDisk(_Total)\Avg. Disk sec/Transfer',
+  '\PhysicalDisk(_Total)\Avg. Disk Queue Length',
+  '\Network Interface(*)\Bytes Received/sec',
+  '\Network Interface(*)\Bytes Sent/sec',
+  '\Memory\Available MBytes'
+)
+
+while (-not (Test-Path -LiteralPath $StopFile)) {
+  try {
+    $sample = Get-Counter -Counter $counterPaths -ErrorAction Stop
+    $row = [pscustomobject]@{
+      timestamp = (Get-Date).ToUniversalTime().ToString('o')
+      cpu_percent = Get-SingleCounterValue -CounterSample $sample -PathPattern '*\processor(_total)\% processor time'
+      processor_queue_length = Get-SingleCounterValue -CounterSample $sample -PathPattern '*\system\processor queue length'
+      disk_read_bytes_per_sec = Get-SingleCounterValue -CounterSample $sample -PathPattern '*\physicaldisk(_total)\disk read bytes/sec'
+      disk_write_bytes_per_sec = Get-SingleCounterValue -CounterSample $sample -PathPattern '*\physicaldisk(_total)\disk write bytes/sec'
+      disk_seconds_per_transfer = Get-SingleCounterValue -CounterSample $sample -PathPattern '*\physicaldisk(_total)\avg. disk sec/transfer'
+      disk_queue_length = Get-SingleCounterValue -CounterSample $sample -PathPattern '*\physicaldisk(_total)\avg. disk queue length'
+      network_received_bytes_per_sec = Get-SummedCounterValue -CounterSample $sample -PathPattern '*\network interface(*)\bytes received/sec'
+      network_sent_bytes_per_sec = Get-SummedCounterValue -CounterSample $sample -PathPattern '*\network interface(*)\bytes sent/sec'
+      available_memory_mib = Get-SingleCounterValue -CounterSample $sample -PathPattern '*\memory\available mbytes'
+    }
+    $row | Export-Csv -LiteralPath $OutputPath -Append -NoTypeInformation
+  }
+  catch {
+    Write-Warning "Windows Bazel telemetry sample failed: $($_.Exception.Message)"
+  }
+
+  # Check the stop file once a second so the monitor does not add up to one
+  # full sampling interval to the measured workflow step during cleanup.
+  for ($second = 0; $second -lt $IntervalSeconds; $second += 1) {
+    if (Test-Path -LiteralPath $StopFile) {
+      break
+    }
+    Start-Sleep -Seconds 1
+  }
+}
diff --git a/.github/workflows/bazel.yml b/.github/workflows/bazel.yml
index 3e48b741b76..eae40844c66 100644
--- a/.github/workflows/bazel.yml
+++ b/.github/workflows/bazel.yml
@@ -143,10 +143,14 @@ jobs:
           - 2
           - 3
           - 4
+          - 5
+          - 6
+          - 7
+          - 8
     runs-on:
       group: ${{ github.event.repository.name }}-runners
       labels: ${{ github.event.repository.name }}-windows-x64
-    name: Bazel test on windows-latest for x86_64-pc-windows-gnullvm shard ${{ matrix.shard }}/4
+    name: Bazel test on windows-latest for x86_64-pc-windows-gnullvm shard ${{ matrix.shard }}/8
     environment:
       name: bazel
       deployment: false
@@ -175,12 +179,26 @@ jobs:
       - name: bazel test shard
         env:
           BAZEL_TEST_SHARD: ${{ matrix.shard }}
-          BAZEL_TEST_SHARD_COUNT: 4
+          BAZEL_TEST_SHARD_COUNT: 8
           BUILDBUDDY_API_KEY: ${{ secrets.BUILDBUDDY_API_KEY }}
+          WINDOWS_BAZEL_TELEMETRY_PATH: ${{ runner.temp }}/windows-bazel-telemetry-shard-${{ matrix.shard }}.csv
+          WINDOWS_BAZEL_TELEMETRY_STOP_FILE: ${{ runner.temp }}/windows-bazel-telemetry-stop-shard-${{ matrix.shard }}
         shell: bash
         run: |
           set -euo pipefail
 
+          rm -f "${WINDOWS_BAZEL_TELEMETRY_PATH}" "${WINDOWS_BAZEL_TELEMETRY_STOP_FILE}"
+          pwsh -NoProfile -File .github/scripts/measure-windows-bazel.ps1 \
+            -Mode monitor \
+            -OutputPath "${WINDOWS_BAZEL_TELEMETRY_PATH}" \
+            -StopFile "${WINDOWS_BAZEL_TELEMETRY_STOP_FILE}" &
+          telemetry_pid=$!
+          stop_telemetry() {
+            touch "${WINDOWS_BAZEL_TELEMETRY_STOP_FILE}"
+            wait "${telemetry_pid}" || true
+          }
+          trap stop_telemetry EXIT
+
           bazel_test_query='tests(//...) except tests(//third_party/v8:all) except attr(tags, "manual", tests(//...))'
           mapfile -t bazel_targets < <(
             ./.github/scripts/run-bazel-query-ci.sh --output=label -- "${bazel_test_query}" \
@@ -211,8 +229,13 @@ jobs:
             --skip_incompatible_explicit_targets
             --test_tag_filters=-argument-comment-lint
             --test_verbose_timeout_warnings
+            # Make every uploaded experiment revision execute its selected
+            # tests instead of reusing the prior revision's test action cache.
+            --test_env=CODEX_BAZEL_TEST_CACHE_BUST=${GITHUB_SHA}
             --build_metadata=COMMIT_SHA=${GITHUB_SHA}
             --build_metadata=TAG_windows_test_shard=${BAZEL_TEST_SHARD}
+            --profile=${RUNNER_TEMP}/windows-bazel-profile-shard-${BAZEL_TEST_SHARD}.gz
+            --noslim_profile
           )
 
           ./.github/scripts/run-bazel-ci.sh \
@@ -225,6 +248,24 @@ jobs:
             -- \
             "${selected_targets[@]}"
 
+      - name: Summarize Windows Bazel telemetry
+        if: always() && !cancelled()
+        continue-on-error: true
+        shell: pwsh
+        run: |
+          ./.github/scripts/measure-windows-bazel.ps1 -Mode summarize -OutputPath "${{ runner.temp }}/windows-bazel-telemetry-shard-${{ matrix.shard }}.csv"
+
+      - name: Upload Windows Bazel telemetry
+        if: always() && !cancelled()
+        continue-on-error: true
+        uses: actions/upload-artifact@bbbca2ddaa5d8feaa63e36b76fdaad77386f024f # v7.0.0
+        with:
+          name: windows-bazel-telemetry-shard-${{ matrix.shard }}
+          path: |
+            ${{ runner.temp }}/windows-bazel-telemetry-shard-${{ matrix.shard }}.csv
+            ${{ runner.temp }}/windows-bazel-profile-shard-${{ matrix.shard }}.gz
+          if-no-files-found: warn
+
       - name: Upload Bazel execution logs
         if: always() && !cancelled()
         continue-on-error: true