diff --git a/.github/workflows/push.yml b/.github/workflows/push.yml
index 2be5811c93..077adc5dd6 100644
--- a/.github/workflows/push.yml
+++ b/.github/workflows/push.yml
@@ -129,6 +129,83 @@ jobs:
               name: macos
 
     steps:
+      # Mount a ReFS Dev Drive on Windows BEFORE the checkout so the checkout's
+      # files land on ReFS directly. The default C: drive on GH runners is
+      # ~4.3k IOPS; a Dev Drive is ~127k. Two access paths on the same volume:
+      #   - $GITHUB_WORKSPACE for the checkout (mounted as folder, not a
+      #     junction, so the runner's open handle on that dir is irrelevant)
+      #   - C:\dd for TEMP and Go caches (separate namespace so it doesn't
+      #     pollute the workspace tree)
+      # All paths start with C:\, so older databricks-bundles tests under
+      # bundle/python/* don't trip os.path.commonpath across drives.
+      - name: Mount ReFS Dev Drive (Windows)
+        if: runner.os == 'Windows'
+        shell: pwsh
+        run: |
+          $ErrorActionPreference = 'Stop'
+
+          # --- Volume A: workspace ---
+          $vhdA = "$env:RUNNER_TEMP\devdrive-ws.vhdx"
+          New-VHD -Path $vhdA -SizeBytes 15GB -Dynamic | Out-Null
+          $diskA = Mount-VHD -Path $vhdA -Passthru |
+            Initialize-Disk -PartitionStyle GPT -Passthru
+          $partA = New-Partition -DiskNumber $diskA.Number -UseMaximumSize -DriveLetter Y
+          try {
+            Format-Volume -DriveLetter Y -FileSystem ReFS -DevDrive `
+              -NewFileSystemLabel DevDriveWS -Confirm:$false -Force | Out-Null
+          } catch {
+            Format-Volume -DriveLetter Y -FileSystem ReFS `
+              -NewFileSystemLabel DevDriveWS -Confirm:$false -Force | Out-Null
+          }
+
+          $ws = $env:GITHUB_WORKSPACE
+          if ((Get-ChildItem -Force $ws | Measure-Object).Count -gt 0) {
+            throw "GITHUB_WORKSPACE ($ws) is not empty; this step must run before actions/checkout."
+          }
+          Add-PartitionAccessPath -DiskNumber $diskA.Number `
+            -PartitionNumber $partA.PartitionNumber -AccessPath $ws
+          Remove-PartitionAccessPath -DiskNumber $diskA.Number `
+            -PartitionNumber $partA.PartitionNumber -AccessPath 'Y:\'
+
+          # ReFS auto-creates "System Volume Information" at the volume root;
+          # it has restrictive ACLs that make scandir fail with EPERM, which
+          # trips actions/checkout. Take ownership and remove it.
+          $svi = Join-Path $ws 'System Volume Information'
+          if (Test-Path $svi) {
+            cmd /c "takeown /F `"$svi`" /A /R" | Out-Null
+            cmd /c "icacls `"$svi`" /grant Administrators:F /T /C" | Out-Null
+            Remove-Item -Path $svi -Recurse -Force -ErrorAction SilentlyContinue
+          }
+
+          # --- Volume B: TEMP + Go caches ---
+          $vhdB = "$env:RUNNER_TEMP\devdrive-cache.vhdx"
+          New-VHD -Path $vhdB -SizeBytes 10GB -Dynamic | Out-Null
+          $diskB = Mount-VHD -Path $vhdB -Passthru |
+            Initialize-Disk -PartitionStyle GPT -Passthru
+          $partB = New-Partition -DiskNumber $diskB.Number -UseMaximumSize -DriveLetter Z
+          try {
+            Format-Volume -DriveLetter Z -FileSystem ReFS -DevDrive `
+              -NewFileSystemLabel DevDriveCache -Confirm:$false -Force | Out-Null
+          } catch {
+            Format-Volume -DriveLetter Z -FileSystem ReFS `
+              -NewFileSystemLabel DevDriveCache -Confirm:$false -Force | Out-Null
+          }
+
+          $mount = 'C:\dd'
+          New-Item -ItemType Directory -Force -Path $mount | Out-Null
+          Add-PartitionAccessPath -DiskNumber $diskB.Number `
+            -PartitionNumber $partB.PartitionNumber -AccessPath $mount
+          Remove-PartitionAccessPath -DiskNumber $diskB.Number `
+            -PartitionNumber $partB.PartitionNumber -AccessPath 'Z:\'
+
+          New-Item -ItemType Directory -Path C:\dd\tmp,C:\dd\go-build,C:\dd\go-mod,C:\dd\go-tmp | Out-Null
+
+          "TMP=C:\dd\tmp"           | Out-File -Append -Encoding utf8 $env:GITHUB_ENV
+          "TEMP=C:\dd\tmp"          | Out-File -Append -Encoding utf8 $env:GITHUB_ENV
+          "GOCACHE=C:\dd\go-build"  | Out-File -Append -Encoding utf8 $env:GITHUB_ENV
+          "GOMODCACHE=C:\dd\go-mod" | Out-File -Append -Encoding utf8 $env:GITHUB_ENV
+          "GOTMPDIR=C:\dd\go-tmp"   | Out-File -Append -Encoding utf8 $env:GITHUB_ENV
+
       - name: Checkout repository and submodules
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
@@ -208,6 +285,83 @@ jobs:
         #     labels: windows-server-latest-large
 
     steps:
+      # Mount a ReFS Dev Drive on Windows BEFORE the checkout so the checkout's
+      # files land on ReFS directly. The default C: drive on GH runners is
+      # ~4.3k IOPS; a Dev Drive is ~127k. Two access paths on the same volume:
+      #   - $GITHUB_WORKSPACE for the checkout (mounted as folder, not a
+      #     junction, so the runner's open handle on that dir is irrelevant)
+      #   - C:\dd for TEMP and Go caches (separate namespace so it doesn't
+      #     pollute the workspace tree)
+      # All paths start with C:\, so older databricks-bundles tests under
+      # bundle/python/* don't trip os.path.commonpath across drives.
+      - name: Mount ReFS Dev Drive (Windows)
+        if: runner.os == 'Windows'
+        shell: pwsh
+        run: |
+          $ErrorActionPreference = 'Stop'
+
+          # --- Volume A: workspace ---
+          $vhdA = "$env:RUNNER_TEMP\devdrive-ws.vhdx"
+          New-VHD -Path $vhdA -SizeBytes 15GB -Dynamic | Out-Null
+          $diskA = Mount-VHD -Path $vhdA -Passthru |
+            Initialize-Disk -PartitionStyle GPT -Passthru
+          $partA = New-Partition -DiskNumber $diskA.Number -UseMaximumSize -DriveLetter Y
+          try {
+            Format-Volume -DriveLetter Y -FileSystem ReFS -DevDrive `
+              -NewFileSystemLabel DevDriveWS -Confirm:$false -Force | Out-Null
+          } catch {
+            Format-Volume -DriveLetter Y -FileSystem ReFS `
+              -NewFileSystemLabel DevDriveWS -Confirm:$false -Force | Out-Null
+          }
+
+          $ws = $env:GITHUB_WORKSPACE
+          if ((Get-ChildItem -Force $ws | Measure-Object).Count -gt 0) {
+            throw "GITHUB_WORKSPACE ($ws) is not empty; this step must run before actions/checkout."
+          }
+          Add-PartitionAccessPath -DiskNumber $diskA.Number `
+            -PartitionNumber $partA.PartitionNumber -AccessPath $ws
+          Remove-PartitionAccessPath -DiskNumber $diskA.Number `
+            -PartitionNumber $partA.PartitionNumber -AccessPath 'Y:\'
+
+          # ReFS auto-creates "System Volume Information" at the volume root;
+          # it has restrictive ACLs that make scandir fail with EPERM, which
+          # trips actions/checkout. Take ownership and remove it.
+          $svi = Join-Path $ws 'System Volume Information'
+          if (Test-Path $svi) {
+            cmd /c "takeown /F `"$svi`" /A /R" | Out-Null
+            cmd /c "icacls `"$svi`" /grant Administrators:F /T /C" | Out-Null
+            Remove-Item -Path $svi -Recurse -Force -ErrorAction SilentlyContinue
+          }
+
+          # --- Volume B: TEMP + Go caches ---
+          $vhdB = "$env:RUNNER_TEMP\devdrive-cache.vhdx"
+          New-VHD -Path $vhdB -SizeBytes 10GB -Dynamic | Out-Null
+          $diskB = Mount-VHD -Path $vhdB -Passthru |
+            Initialize-Disk -PartitionStyle GPT -Passthru
+          $partB = New-Partition -DiskNumber $diskB.Number -UseMaximumSize -DriveLetter Z
+          try {
+            Format-Volume -DriveLetter Z -FileSystem ReFS -DevDrive `
+              -NewFileSystemLabel DevDriveCache -Confirm:$false -Force | Out-Null
+          } catch {
+            Format-Volume -DriveLetter Z -FileSystem ReFS `
+              -NewFileSystemLabel DevDriveCache -Confirm:$false -Force | Out-Null
+          }
+
+          $mount = 'C:\dd'
+          New-Item -ItemType Directory -Force -Path $mount | Out-Null
+          Add-PartitionAccessPath -DiskNumber $diskB.Number `
+            -PartitionNumber $partB.PartitionNumber -AccessPath $mount
+          Remove-PartitionAccessPath -DiskNumber $diskB.Number `
+            -PartitionNumber $partB.PartitionNumber -AccessPath 'Z:\'
+
+          New-Item -ItemType Directory -Path C:\dd\tmp,C:\dd\go-build,C:\dd\go-mod,C:\dd\go-tmp | Out-Null
+
+          "TMP=C:\dd\tmp"           | Out-File -Append -Encoding utf8 $env:GITHUB_ENV
+          "TEMP=C:\dd\tmp"          | Out-File -Append -Encoding utf8 $env:GITHUB_ENV
+          "GOCACHE=C:\dd\go-build"  | Out-File -Append -Encoding utf8 $env:GITHUB_ENV
+          "GOMODCACHE=C:\dd\go-mod" | Out-File -Append -Encoding utf8 $env:GITHUB_ENV
+          "GOTMPDIR=C:\dd\go-tmp"   | Out-File -Append -Encoding utf8 $env:GITHUB_ENV
+
       - name: Checkout repository and submodules
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
@@ -260,6 +414,83 @@ jobs:
               labels: macos-latest
 
     steps:
+      # Mount a ReFS Dev Drive on Windows BEFORE the checkout so the checkout's
+      # files land on ReFS directly. The default C: drive on GH runners is
+      # ~4.3k IOPS; a Dev Drive is ~127k. Two access paths on the same volume:
+      #   - $GITHUB_WORKSPACE for the checkout (mounted as folder, not a
+      #     junction, so the runner's open handle on that dir is irrelevant)
+      #   - C:\dd for TEMP and Go caches (separate namespace so it doesn't
+      #     pollute the workspace tree)
+      # All paths start with C:\, so older databricks-bundles tests under
+      # bundle/python/* don't trip os.path.commonpath across drives.
+      - name: Mount ReFS Dev Drive (Windows)
+        if: runner.os == 'Windows'
+        shell: pwsh
+        run: |
+          $ErrorActionPreference = 'Stop'
+
+          # --- Volume A: workspace ---
+          $vhdA = "$env:RUNNER_TEMP\devdrive-ws.vhdx"
+          New-VHD -Path $vhdA -SizeBytes 15GB -Dynamic | Out-Null
+          $diskA = Mount-VHD -Path $vhdA -Passthru |
+            Initialize-Disk -PartitionStyle GPT -Passthru
+          $partA = New-Partition -DiskNumber $diskA.Number -UseMaximumSize -DriveLetter Y
+          try {
+            Format-Volume -DriveLetter Y -FileSystem ReFS -DevDrive `
+              -NewFileSystemLabel DevDriveWS -Confirm:$false -Force | Out-Null
+          } catch {
+            Format-Volume -DriveLetter Y -FileSystem ReFS `
+              -NewFileSystemLabel DevDriveWS -Confirm:$false -Force | Out-Null
+          }
+
+          $ws = $env:GITHUB_WORKSPACE
+          if ((Get-ChildItem -Force $ws | Measure-Object).Count -gt 0) {
+            throw "GITHUB_WORKSPACE ($ws) is not empty; this step must run before actions/checkout."
+          }
+          Add-PartitionAccessPath -DiskNumber $diskA.Number `
+            -PartitionNumber $partA.PartitionNumber -AccessPath $ws
+          Remove-PartitionAccessPath -DiskNumber $diskA.Number `
+            -PartitionNumber $partA.PartitionNumber -AccessPath 'Y:\'
+
+          # ReFS auto-creates "System Volume Information" at the volume root;
+          # it has restrictive ACLs that make scandir fail with EPERM, which
+          # trips actions/checkout. Take ownership and remove it.
+          $svi = Join-Path $ws 'System Volume Information'
+          if (Test-Path $svi) {
+            cmd /c "takeown /F `"$svi`" /A /R" | Out-Null
+            cmd /c "icacls `"$svi`" /grant Administrators:F /T /C" | Out-Null
+            Remove-Item -Path $svi -Recurse -Force -ErrorAction SilentlyContinue
+          }
+
+          # --- Volume B: TEMP + Go caches ---
+          $vhdB = "$env:RUNNER_TEMP\devdrive-cache.vhdx"
+          New-VHD -Path $vhdB -SizeBytes 10GB -Dynamic | Out-Null
+          $diskB = Mount-VHD -Path $vhdB -Passthru |
+            Initialize-Disk -PartitionStyle GPT -Passthru
+          $partB = New-Partition -DiskNumber $diskB.Number -UseMaximumSize -DriveLetter Z
+          try {
+            Format-Volume -DriveLetter Z -FileSystem ReFS -DevDrive `
+              -NewFileSystemLabel DevDriveCache -Confirm:$false -Force | Out-Null
+          } catch {
+            Format-Volume -DriveLetter Z -FileSystem ReFS `
+              -NewFileSystemLabel DevDriveCache -Confirm:$false -Force | Out-Null
+          }
+
+          $mount = 'C:\dd'
+          New-Item -ItemType Directory -Force -Path $mount | Out-Null
+          Add-PartitionAccessPath -DiskNumber $diskB.Number `
+            -PartitionNumber $partB.PartitionNumber -AccessPath $mount
+          Remove-PartitionAccessPath -DiskNumber $diskB.Number `
+            -PartitionNumber $partB.PartitionNumber -AccessPath 'Z:\'
+
+          New-Item -ItemType Directory -Path C:\dd\tmp,C:\dd\go-build,C:\dd\go-mod,C:\dd\go-tmp | Out-Null
+
+          "TMP=C:\dd\tmp"           | Out-File -Append -Encoding utf8 $env:GITHUB_ENV
+          "TEMP=C:\dd\tmp"          | Out-File -Append -Encoding utf8 $env:GITHUB_ENV
+          "GOCACHE=C:\dd\go-build"  | Out-File -Append -Encoding utf8 $env:GITHUB_ENV
+          "GOMODCACHE=C:\dd\go-mod" | Out-File -Append -Encoding utf8 $env:GITHUB_ENV
+          "GOTMPDIR=C:\dd\go-tmp"   | Out-File -Append -Encoding utf8 $env:GITHUB_ENV
+
       - name: Checkout repository and submodules
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
@@ -312,6 +543,83 @@ jobs:
               labels: macos-latest
 
     steps:
+      # Mount a ReFS Dev Drive on Windows BEFORE the checkout so the checkout's
+      # files land on ReFS directly. The default C: drive on GH runners is
+      # ~4.3k IOPS; a Dev Drive is ~127k. Two access paths on the same volume:
+      #   - $GITHUB_WORKSPACE for the checkout (mounted as folder, not a
+      #     junction, so the runner's open handle on that dir is irrelevant)
+      #   - C:\dd for TEMP and Go caches (separate namespace so it doesn't
+      #     pollute the workspace tree)
+      # All paths start with C:\, so older databricks-bundles tests under
+      # bundle/python/* don't trip os.path.commonpath across drives.
+      - name: Mount ReFS Dev Drive (Windows)
+        if: runner.os == 'Windows'
+        shell: pwsh
+        run: |
+          $ErrorActionPreference = 'Stop'
+
+          # --- Volume A: workspace ---
+          $vhdA = "$env:RUNNER_TEMP\devdrive-ws.vhdx"
+          New-VHD -Path $vhdA -SizeBytes 15GB -Dynamic | Out-Null
+          $diskA = Mount-VHD -Path $vhdA -Passthru |
+            Initialize-Disk -PartitionStyle GPT -Passthru
+          $partA = New-Partition -DiskNumber $diskA.Number -UseMaximumSize -DriveLetter Y
+          try {
+            Format-Volume -DriveLetter Y -FileSystem ReFS -DevDrive `
+              -NewFileSystemLabel DevDriveWS -Confirm:$false -Force | Out-Null
+          } catch {
+            Format-Volume -DriveLetter Y -FileSystem ReFS `
+              -NewFileSystemLabel DevDriveWS -Confirm:$false -Force | Out-Null
+          }
+
+          $ws = $env:GITHUB_WORKSPACE
+          if ((Get-ChildItem -Force $ws | Measure-Object).Count -gt 0) {
+            throw "GITHUB_WORKSPACE ($ws) is not empty; this step must run before actions/checkout."
+          }
+          Add-PartitionAccessPath -DiskNumber $diskA.Number `
+            -PartitionNumber $partA.PartitionNumber -AccessPath $ws
+          Remove-PartitionAccessPath -DiskNumber $diskA.Number `
+            -PartitionNumber $partA.PartitionNumber -AccessPath 'Y:\'
+
+          # ReFS auto-creates "System Volume Information" at the volume root;
+          # it has restrictive ACLs that make scandir fail with EPERM, which
+          # trips actions/checkout. Take ownership and remove it.
+          $svi = Join-Path $ws 'System Volume Information'
+          if (Test-Path $svi) {
+            cmd /c "takeown /F `"$svi`" /A /R" | Out-Null
+            cmd /c "icacls `"$svi`" /grant Administrators:F /T /C" | Out-Null
+            Remove-Item -Path $svi -Recurse -Force -ErrorAction SilentlyContinue
+          }
+
+          # --- Volume B: TEMP + Go caches ---
+          $vhdB = "$env:RUNNER_TEMP\devdrive-cache.vhdx"
+          New-VHD -Path $vhdB -SizeBytes 10GB -Dynamic | Out-Null
+          $diskB = Mount-VHD -Path $vhdB -Passthru |
+            Initialize-Disk -PartitionStyle GPT -Passthru
+          $partB = New-Partition -DiskNumber $diskB.Number -UseMaximumSize -DriveLetter Z
+          try {
+            Format-Volume -DriveLetter Z -FileSystem ReFS -DevDrive `
+              -NewFileSystemLabel DevDriveCache -Confirm:$false -Force | Out-Null
+          } catch {
+            Format-Volume -DriveLetter Z -FileSystem ReFS `
+              -NewFileSystemLabel DevDriveCache -Confirm:$false -Force | Out-Null
+          }
+
+          $mount = 'C:\dd'
+          New-Item -ItemType Directory -Force -Path $mount | Out-Null
+          Add-PartitionAccessPath -DiskNumber $diskB.Number `
+            -PartitionNumber $partB.PartitionNumber -AccessPath $mount
+          Remove-PartitionAccessPath -DiskNumber $diskB.Number `
+            -PartitionNumber $partB.PartitionNumber -AccessPath 'Z:\'
+
+          New-Item -ItemType Directory -Path C:\dd\tmp,C:\dd\go-build,C:\dd\go-mod,C:\dd\go-tmp | Out-Null
+
+          "TMP=C:\dd\tmp"           | Out-File -Append -Encoding utf8 $env:GITHUB_ENV
+          "TEMP=C:\dd\tmp"          | Out-File -Append -Encoding utf8 $env:GITHUB_ENV
+          "GOCACHE=C:\dd\go-build"  | Out-File -Append -Encoding utf8 $env:GITHUB_ENV
+          "GOMODCACHE=C:\dd\go-mod" | Out-File -Append -Encoding utf8 $env:GITHUB_ENV
+          "GOTMPDIR=C:\dd\go-tmp"   | Out-File -Append -Encoding utf8 $env:GITHUB_ENV
+
       - name: Checkout repository and submodules
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2