diff --git a/.gitea/workflows/runner-probe.yaml b/.gitea/workflows/runner-probe.yaml
new file mode 100644
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+++ b/.gitea/workflows/runner-probe.yaml
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+name: Runner probe (throwaway)
+
+# Temporary diagnostic: discover the silverlabs-runner-win host identity, drives,
+# existing share mounts/stored creds, and whether the base ISO is reachable -
+# so we can pick the simplest path (local path vs persistent SMB mount). Delete
+# once the ISO source is wired. workflow_dispatch only.
+
+on:
+  workflow_dispatch:
+
+jobs:
+  probe:
+    runs-on: windows-latest
+    timeout-minutes: 5
+    steps:
+      - name: Probe
+        shell: pwsh
+        env:
+          ISO_SRC: ${{ vars.SILVERMETAL_BASE_ISO_URL }}
+        run: |
+          Write-Host "host=$env:COMPUTERNAME  user=$(whoami)"
+          Write-Host "--- IPv4 (is the runner itself 10.0.0.60?) ---"
+          (Get-NetIPAddress -AddressFamily IPv4 | Where-Object { $_.IPAddress -ne '127.0.0.1' }).IPAddress
+          Write-Host "--- local filesystem drives ---"
+          Get-PSDrive -PSProvider FileSystem | Format-Table Name, @{n='UsedGB';e={[math]::Round($_.Used/1GB,1)}}, @{n='FreeGB';e={[math]::Round($_.Free/1GB,1)}}, Root -AutoSize
+          Write-Host "--- existing net use mappings ---"; cmd /c "net use"
+          Write-Host "--- stored credentials (cmdkey) ---"; cmd /c "cmdkey /list"
+          Write-Host "--- UNC reachability as SYSTEM ---"
+          Write-Host ("UNC exists = {0}" -f [bool](Test-Path -LiteralPath $env:ISO_SRC))
+          Write-Host "--- top-level dirs on each drive matching ISO/private/SILVERLABS ---"
+          Get-PSDrive -PSProvider FileSystem | ForEach-Object {
+            Get-ChildItem $_.Root -Directory -EA SilentlyContinue |
+              Where-Object Name -match 'ISO|private|SILVERLABS|template' |
+              Select-Object -ExpandProperty FullName
+          }