diff --git a/.gitea/workflows/cicd.yaml b/.gitea/workflows/cicd.yaml
index 0f15fe7..d65abbc 100644
--- a/.gitea/workflows/cicd.yaml
+++ b/.gitea/workflows/cicd.yaml
@@ -804,6 +804,113 @@ jobs:
 
           exit 0
 
+  source-lanes-postmortem:
+    name: Source Lanes Failure Postmortem
+    # Capture follow-up diagnostics when any source lane dies during platform
+    # setup before step logging is available.
+    runs-on: ubuntu-act-8gb
+    needs: [backend-tests, precommit-tests, frontend-tests, xdoctest]
+    if: always() && (needs['backend-tests'].result == 'failure' || needs['precommit-tests'].result == 'failure' || needs['frontend-tests'].result == 'failure' || needs.xdoctest.result == 'failure')
+    timeout-minutes: 10
+    steps:
+      - name: Identify runner
+        run: |
+          echo "=== Runner Identity ==="
+          echo "runner_name=${RUNNER_NAME:-}"
+          echo "runner_name_hint=${GITEA_RUNNER_NAME:-${ACT_RUNNER_NAME:-${RUNNER_NAME:-unknown}}}"
+          echo "runner_hostname_env=${HOSTNAME:-unknown}"
+          echo "runner_uname_n=$(uname -n 2>/dev/null || echo unknown)"
+          echo "runner_etc_hostname=$(cat /etc/hostname 2>/dev/null || echo unknown)"
+          echo "runner_os=${RUNNER_OS:-unknown}"
+          echo "runner_arch=${RUNNER_ARCH:-unknown}"
+          echo "timestamp_utc=$(date -u +%Y-%m-%dT%H:%M:%SZ)"
+
+      - name: Collect source lane postmortem context
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          set +e
+
+          echo "=== Postmortem Context ==="
+          echo "workflow=${GITHUB_WORKFLOW:-unknown}"
+          echo "run_id=${GITHUB_RUN_ID:-unknown}"
+          echo "run_number=${GITHUB_RUN_NUMBER:-unknown}"
+          echo "run_attempt=${GITHUB_RUN_ATTEMPT:-unknown}"
+          echo "repository=${GITHUB_REPOSITORY:-unknown}"
+          echo "server_url=${GITHUB_SERVER_URL:-unknown}"
+          echo "backend_tests_result=${{ needs['backend-tests'].result }}"
+          echo "precommit_tests_result=${{ needs['precommit-tests'].result }}"
+          echo "frontend_tests_result=${{ needs['frontend-tests'].result }}"
+          echo "xdoctest_result=${{ needs.xdoctest.result }}"
+
+          echo "=== Local Runner Telemetry (postmortem job host) ==="
+          uname -a || true
+          cat /etc/os-release 2>/dev/null || true
+          df -h || true
+          free -h || true
+          if command -v docker >/dev/null 2>&1; then
+            docker version || true
+            docker info || true
+          fi
+
+          echo "=== Registry Reachability Probe ==="
+          timeout 10 curl -fsSIL "https://${GITEA_REGISTRY}/v2/" || true
+
+          if [ -z "${GITHUB_TOKEN:-}" ]; then
+            echo "No GITHUB_TOKEN available for API diagnostics"
+            exit 0
+          fi
+
+          API_BASE="${GITHUB_API_URL:-${GITHUB_SERVER_URL}/api/v1}"
+          JOBS_URL="${API_BASE}/repos/${GITHUB_REPOSITORY}/actions/runs/${GITHUB_RUN_ID}/jobs?limit=200"
+
+          echo "=== Actions API Job Summary ==="
+          echo "jobs_url=${JOBS_URL}"
+          if ! curl -fsSL -H "Authorization: token ${GITHUB_TOKEN}" -H "Accept: application/json" "${JOBS_URL}" -o /tmp/actions-jobs.json; then
+            echo "Could not fetch job metadata from Actions API"
+            exit 0
+          fi
+
+          if command -v python3 >/dev/null 2>&1; then
+            python3 -c "$(printf '%s\n' \
+              'import json' \
+              'from pathlib import Path' \
+              '' \
+              'path = Path("/tmp/actions-jobs.json")' \
+              'payload = json.loads(path.read_text())' \
+              'jobs = payload.get("jobs") or payload.get("data") or []' \
+              '' \
+              'print("job_count=", len(jobs))' \
+              '' \
+              'def _g(job, *keys):' \
+              '    for key in keys:' \
+              '        if key in job and job[key] not in (None, ""):' \
+              '            return job[key]' \
+              '    return "unknown"' \
+              '' \
+              'targets = {' \
+              '    "Backend Tests",' \
+              '    "Pre-commit Checks",' \
+              '    "Frontend Tests",' \
+              '    "Backend Doctests",' \
+              '}' \
+              '' \
+              'for job in jobs:' \
+              '    name = str(_g(job, "name", "job_name"))' \
+              '    if name in targets:' \
+              '        status = _g(job, "status")' \
+              '        conclusion = _g(job, "conclusion", "result")' \
+              '        runner = _g(job, "runner_name", "runner")' \
+              '        started = _g(job, "started_at", "start_time")' \
+              '        completed = _g(job, "completed_at", "end_time")' \
+              '        print(f"job={name} status={status} conclusion={conclusion} runner={runner} started={started} completed={completed}")')"
+          else
+            echo "python3 unavailable; emitting raw jobs payload head"
+            sed -n '1,120p' /tmp/actions-jobs.json || true
+          fi
+
+          exit 0
+
   integration-tests:
     name: Runtime Black-Box Integration Tests
     # Pin integration tests to high-memory worker to reduce setup-stage runner churn.