Reuse exact GPU validation on draft promotion

.github/workflows/trainer-rank-gpu.yml

@@ -15,15 +15,70 @@ concurrency:
 jobs:
   classify:
     runs-on: ubuntu-latest
+    permissions:
+      actions: read
+      contents: read
     outputs:
       required: ${{ steps.changes.outputs.required }}
       head_sha: ${{ steps.changes.outputs.head_sha }}
+      reused: ${{ steps.reuse.outputs.reused }}
+      reused_run: ${{ steps.reuse.outputs.run_id }}
     steps:
       - uses: actions/checkout@v4
         with:
           ref: ${{ github.event.pull_request.head.sha || github.sha }}
           fetch-depth: 0
 
+      - id: reuse
+        name: Find exact prior GPU validation
+        if: github.event_name == 'pull_request' && github.event.action == 'ready_for_review'
+        continue-on-error: true
+        timeout-minutes: 2
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const pull = context.payload.pull_request;
+            const runs = await github.rest.actions.listWorkflowRuns({
+              ...context.repo,
+              workflow_id: 'trainer-rank-gpu.yml',
+              event: 'pull_request',
+              head_sha: pull.head.sha,
+              status: 'success',
+              per_page: 100,
+            });
+            const candidates = runs.data.workflow_runs.filter(run =>
+              run.id !== context.runId &&
+              run.head_sha === pull.head.sha &&
+              run.path === '.github/workflows/trainer-rank-gpu.yml' &&
+              (run.pull_requests ?? []).some(previous => previous.number === pull.number)
+            ).slice(0, 10);
+            for (const run of candidates) {
+              const jobs = await github.rest.actions.listJobsForWorkflowRun({
+                ...context.repo,
+                run_id: run.id,
+                filter: 'latest',
+                per_page: 100,
+              });
+              const artifacts = await github.rest.actions.listWorkflowRunArtifacts({
+                ...context.repo,
+                run_id: run.id,
+                per_page: 100,
+              });
+              const passed = jobs.data.jobs.some(job =>
+                job.name === 'Run on 2x H200' && job.conclusion === 'success'
+              );
+              const base = artifacts.data.artifacts.some(artifact =>
+                !artifact.expired && artifact.name ===
+                  `trainer-rank-result-${run.id}-${run.run_attempt}-${pull.base.sha}`
+              );
+              if (passed && base) {
+                core.setOutput('reused', 'true');
+                core.setOutput('run_id', String(run.id));
+                core.info(`Reusing successful workflow run ${run.id}.`);
+                return;
+              }
+            }
+
       - id: changes
         name: Classify changed files
         env:
@@ -65,7 +120,7 @@ jobs:
   validate:
     name: Run on 2x H200
     needs: classify
-    if: needs.classify.outputs.required == 'true'
+    if: needs.classify.outputs.required == 'true' && needs.classify.outputs.reused != 'true'
     runs-on: ubuntu-latest
     timeout-minutes: 45
     environment: trainer-rank-gpu-validation
@@ -154,7 +209,7 @@ jobs:
         if: always()
         uses: actions/upload-artifact@v4
         with:
-          name: trainer-rank-result-${{ github.run_id }}-${{ github.run_attempt }}
+          name: trainer-rank-result-${{ github.run_id }}-${{ github.run_attempt }}-${{ github.event.pull_request.base.sha || 'manual' }}
           path: ${{ runner.temp }}/trainer-rank-result
           if-no-files-found: warn
 
@@ -167,17 +222,26 @@ jobs:
       - env:
           CLASSIFY_RESULT: ${{ needs.classify.result }}
           REQUIRED: ${{ needs.classify.outputs.required }}
+          REUSED: ${{ needs.classify.outputs.reused }}
+          REUSED_RUN: ${{ needs.classify.outputs.reused_run }}
           RESULT: ${{ needs.validate.result }}
         run: |
+          set -euo pipefail
           if [ "${CLASSIFY_RESULT}" != "success" ]; then
             echo "TrainerRank GPU classification failed." >&2
             exit 1
           fi
-          if [ "${REQUIRED}" = "true" ] && [ "${RESULT}" != "success" ]; then
+          if [ "${REQUIRED}" = "true" ] \
+            && [ "${REUSED}" != "true" ] \
+            && [ "${RESULT}" != "success" ]; then
             echo "TrainerRank GPU validation required but result was ${RESULT}." >&2
             exit 1
           fi
-          if [ "${REQUIRED}" = "true" ]; then
+          if [ "${REUSED}" = "true" ]; then
+            test -n "${REUSED_RUN}"
+            echo "TrainerRank GPU validation reused from exact run ${REUSED_RUN}." \
+              | tee -a "${GITHUB_STEP_SUMMARY}"
+          elif [ "${REQUIRED}" = "true" ]; then
             echo "TrainerRank GPU validation passed."
           else
             echo "TrainerRank GPU validation was not required."