Fix Buildkite detective empty event context (#660)

.github/workflows/gh-aw-estc-pr-buildkite-detective.md

@@ -96,22 +96,27 @@ steps:
   - name: Resolve event context
     run: |
       set -euo pipefail
-      echo "BK_EVENT_NAME=$GITHUB_EVENT_NAME" >> "$GITHUB_ENV"
-      if [ "$GITHUB_EVENT_NAME" = "status" ]; then
-        echo "BK_EVENT_ID=$(jq -r '.id' "$GITHUB_EVENT_PATH")" >> "$GITHUB_ENV"
-        echo "BK_FAILURE_STATE=$(jq -r '.state' "$GITHUB_EVENT_PATH")" >> "$GITHUB_ENV"
-        echo "BK_COMMIT_SHA=$(jq -r '.commit.sha' "$GITHUB_EVENT_PATH")" >> "$GITHUB_ENV"
-        echo "BK_TARGET_URL=$(jq -r '.target_url // empty' "$GITHUB_EVENT_PATH")" >> "$GITHUB_ENV"
-        echo "BK_BRANCHES=$(jq -c '[(.branches // [])[].name]' "$GITHUB_EVENT_PATH")" >> "$GITHUB_ENV"
-        echo "BK_PR_NUMBERS=" >> "$GITHUB_ENV"
-      else
-        echo "BK_EVENT_ID=$(jq -r '.check_run.id' "$GITHUB_EVENT_PATH")" >> "$GITHUB_ENV"
-        echo "BK_FAILURE_STATE=$(jq -r '.check_run.conclusion' "$GITHUB_EVENT_PATH")" >> "$GITHUB_ENV"
-        echo "BK_COMMIT_SHA=$(jq -r '.check_run.head_sha' "$GITHUB_EVENT_PATH")" >> "$GITHUB_ENV"
-        echo "BK_TARGET_URL=$(jq -r '.check_run.details_url // empty' "$GITHUB_EVENT_PATH")" >> "$GITHUB_ENV"
-        echo "BK_BRANCHES=" >> "$GITHUB_ENV"
-        echo "BK_PR_NUMBERS=$(jq -rc '[(.check_run.pull_requests // [])[].number] | if length == 0 then "" else . end' "$GITHUB_EVENT_PATH")" >> "$GITHUB_ENV"
-      fi
+      mkdir -p /tmp/gh-aw
+      {
+        echo "event_name: $GITHUB_EVENT_NAME"
+        if [ "$GITHUB_EVENT_NAME" = "status" ]; then
+          echo "event_id: $(jq -r '.id' "$GITHUB_EVENT_PATH")"
+          echo "failure_state: $(jq -r '.state' "$GITHUB_EVENT_PATH")"
+          echo "commit_sha: $(jq -r '.commit.sha' "$GITHUB_EVENT_PATH")"
+          echo "target_url: $(jq -r '.target_url // empty' "$GITHUB_EVENT_PATH")"
+          echo "branches: $(jq -r '[(.branches // [])[].name] | join(", ")' "$GITHUB_EVENT_PATH")"
+          echo "pr_numbers:"
+        else
+          echo "event_id: $(jq -r '.check_run.id' "$GITHUB_EVENT_PATH")"
+          echo "failure_state: $(jq -r '.check_run.conclusion' "$GITHUB_EVENT_PATH")"
+          echo "commit_sha: $(jq -r '.check_run.head_sha' "$GITHUB_EVENT_PATH")"
+          echo "target_url: $(jq -r '.check_run.details_url // empty' "$GITHUB_EVENT_PATH")"
+          echo "branches:"
+          echo "pr_numbers: $(jq -r '[(.check_run.pull_requests // [])[].number | tostring] | join(", ")' "$GITHUB_EVENT_PATH")"
+        fi
+      } > /tmp/gh-aw/buildkite-event.txt
+      echo "Buildkite event context:"
+      cat /tmp/gh-aw/buildkite-event.txt
   - name: Repo-specific setup
     if: ${{ inputs.setup-commands != '' }}
     env:
@@ -128,15 +133,10 @@ Analyze failed Buildkite CI builds for pull requests in ${{ github.repository }}
 ## Context
 
 - **Repository**: ${{ github.repository }}
-- **Event Name**: ${{ env.BK_EVENT_NAME }}
-- **Event ID**: ${{ env.BK_EVENT_ID }}
-- **Failure State**: ${{ env.BK_FAILURE_STATE }}
-- **Commit SHA**: ${{ env.BK_COMMIT_SHA }}
-- **Target URL**: ${{ env.BK_TARGET_URL }}
-- **PR Numbers**: ${{ env.BK_PR_NUMBERS }}
-- **Branches**: ${{ env.BK_BRANCHES }}
 - **Buildkite Organization**: ${{ inputs.buildkite-org }}
 
+**Read `/tmp/gh-aw/buildkite-event.txt` first.** It contains the event context (commit SHA, target URL, PR numbers, branches, failure state) extracted from the GitHub event payload.
+
 ## Constraints
 
 - **CAN**: Read files, search code, run tests and commands, query Buildkite via MCP, comment on PRs
@@ -165,10 +165,10 @@ Classify each failure to guide your investigation:
 
 ### Step 1: Gather Context
 
-1. Use the commit SHA provided in the Context section above. If it is empty, discover it from the PR's commit statuses or check runs.
+1. Read `/tmp/gh-aw/buildkite-event.txt` to get the event context. Use the `commit_sha` value. If it is empty, discover it from the PR's commit statuses or check runs.
 2. Find the associated pull request(s):
-   - If **PR Numbers** in the Context section above is non-empty (e.g., from `check_run` events), use those PR numbers directly with `pull_request_read` method `get`.
-   - Otherwise, use `bash` + `gh api repos/${{ github.repository }}/commits/{commit_sha}/pulls` to find PRs containing the commit SHA. Filter the results to keep only PRs whose `state` is `"open"` and, when **Branches** is available, whose `head.ref` matches one of the listed branches. If no candidates remain, also try searching open PRs whose head branch matches one of the **Branches** listed in the Context section.
+   - If `pr_numbers` is non-empty (from `check_run` events), use those PR numbers directly with `pull_request_read` method `get`.
+   - Otherwise, use `bash` + `gh api repos/${{ github.repository }}/commits/{commit_sha}/pulls` to find PRs containing the commit SHA. Filter the results to keep only PRs whose `state` is `"open"` and, when `branches` is non-empty, whose `head.ref` matches one of the listed branches. If no candidates remain, also try searching open PRs whose head branch matches one of the branches.
    - If no PR is found after all attempts, call `noop` with message "No pull request associated with failed commit status; nothing to do" and stop.
 3. For each matching PR, call `pull_request_read` with method `get` to capture the author, branches, and fork status for downstream analysis.