Auto-close stale Known Build Error issues with zero monthly hits

.github/workflows/stale.yml

@@ -3,6 +3,11 @@ on:
   schedule:
     - cron: '19 4,16 * * *' # Twice daily at 19 minutes after the hour (random/uncommon time)
 
+env:
+  KBE_LABEL: 'Known Build Error'
+  STALE_LABEL: 'stale'
+  KEEP_OPEN_LABEL: 'keep-open'
+
 permissions:
   actions: write # For managing the operation state cache
   issues: write
@@ -23,4 +28,66 @@ jobs:
           days-before-issue-close: 30
           days-before-pr-stale: 180 # 6 months
           days-before-pr-close: 7
+          exempt-issue-labels: ${{ env.KBE_LABEL }}
           operations-per-run: 4000
+
+  # Known Build Error issues with 0 hits for a month get labeled Stale,
+  # then actions/stale closes them after 7 days.
+  stale-known-build-errors:
+    if: github.repository_owner == 'dotnet' # Do not run on forks
+
+    runs-on: ubuntu-latest
+    steps:
+      # Step 1: Label/unlabel based on hit counts
+      - uses: actions/github-script@v7
+        with:
+          script: |
+            const issues = await github.paginate(
+              github.rest.issues.listForRepo,
+              { owner: context.repo.owner, repo: context.repo.repo,
+                labels: process.env.KBE_LABEL, state: 'open', per_page: 100 });
+
+            for (const issue of issues) {
+              if (issue.pull_request) continue;
+              if (issue.labels.some(l => l.name === process.env.KEEP_OPEN_LABEL)) continue;
+
+              // Parse the hit count summary table from the issue body.
+              // Format: |24-Hour Hit Count|7-Day Hit Count|1-Month Count|
+              //         |---|---|---|
+              //         |N|N|N|
+              const match = issue.body?.match(
+                /\|24-Hour Hit Count\|.*\n\|[-| ]+\n\|(\d+)\|(\d+)\|(\d+)\|/);
+              if (!match) continue;
+              const monthCount = parseInt(match[3], 10);
+
+              const hasStale = issue.labels.some(l => l.name === process.env.STALE_LABEL);
+
+              if (monthCount === 0 && !hasStale) {
+                // Zero hits for a month: mark as stale
+                await github.rest.issues.addLabels({
+                  ...context.repo, issue_number: issue.number,
+                  labels: [process.env.STALE_LABEL] });
+                await github.rest.issues.createComment({
+                  ...context.repo, issue_number: issue.number,
+                  body: 'This Known Build Error has had **0 hits in the past month** and has been labeled `stale`. ' +
+                    'It will be auto-closed in 7 days if the hit count remains at 0. ' +
+                    'Add the `' + process.env.KEEP_OPEN_LABEL + '` label to prevent auto-closure.' });
+              } else if (monthCount > 0 && hasStale) {
+                // Hits resumed: remove the stale label
+                await github.rest.issues.removeLabel({
+                  ...context.repo, issue_number: issue.number,
+                  name: process.env.STALE_LABEL }).catch(() => {});
+              }
+            }
+
+      # Step 2: Close KBE issues that have been Stale for 7+ days
+      - uses: actions/stale@v9
+        with:
+          only-labels: ${{ env.KBE_LABEL }}
+          stale-issue-label: ${{ env.STALE_LABEL }}
+          close-issue-message: 'Closed automatically — this Known Build Error has had 0 hits for over a month.'
+          days-before-issue-stale: -1 # Don't auto-stale; step 1 handles that
+          days-before-issue-close: 7
+          days-before-pr-stale: -1
+          days-before-pr-close: -1
+          operations-per-run: 100