Payload Experimental Reverts

Payload Experimental Reverts

This skill experimentally tests medium-confidence candidate PRs by opening draft revert PRs, triggering payload jobs, and evaluating results. It operates in two phases separated by a CI wait period. All state is tracked in the payload results YAML file via the payload-results-yaml skill — no separate tracking file is created.

When to Use This Skill

Use this skill when the /ci:payload-experiment command identifies candidate PRs with medium confidence (score 60-84) that cannot be conclusively attributed to a failure through static analysis alone. The experiment creates real tests to determine causality.

Inputs (passed in-context by the caller):

• results_yaml_path: Path to the payload results YAML file (e.g., ./payload-results-{tag}.yaml)
• candidates: List of medium-confidence PRs to test experimentally, each with:
  • pr_url, pr_number, component, title, confidence_score
  • failing_jobs: List of {job_name, prow_url, is_aggregated, underlying_job_name}

Required Skills

Before starting, you MUST load the following skills (they define output schemas used when updating results):

1. payload-results-yaml — schema for the payload results YAML file
2. payload-autodl-json — schema for the autodl JSON data file

Prerequisites

1. GitHub CLI (gh): Installed and authenticated
2. JIRA MCP: Configured for creating TRT issues (needed in Phase 2 for confirmed causes)
3. Repository Access: User must have push access to their fork of each target repository

Implementation Steps

Phase 1: Set Up Experiments

For each medium-confidence candidate, launch a parallel subagent (do NOT set the model parameter):

1.1: Check for Merge Conflicts

Before opening a revert PR, preemptively check whether the revert will have merge conflicts:

# Clone the repo (shallow for speed)
git clone -b <base_branch> --depth 50 "https://github.com/<org>/<repo>.git" /tmp/experiment-check-<pr_number>
cd /tmp/experiment-check-<pr_number>

# Attempt the revert without committing
git revert -m1 --no-commit <merge_sha>

# Check for conflicts
git status --porcelain

If conflicts exist:

• Append an action entry with type: "experiment", status: "skipped_conflict" to this candidate's actions array
• Skip to the next candidate
• Do NOT attempt to resolve conflicts for experimental reverts

If no conflicts, abort the dry-run revert and proceed:

git revert --abort 2>/dev/null || git checkout -- .

1.2: Open Draft Revert PR

Load the revert-pr skill and follow its workflow with --draft:

• PR URL: the candidate PR
• JIRA ticket: use a placeholder like NO-JIRA (real ticket is created in Phase 2 only for confirmed causes)
• --draft: Create as a draft PR
• --context: "Experimental revert for {stream} {architecture} payload {payload_tag}. Testing whether reverting this PR resolves blocking job failures."
• Do NOT prompt the user for any input

Record the draft revert PR URL.

1.3: Trigger Payload Jobs and Collect Run URLs

Use the trigger-payload-job skill (plugins/ci/skills/trigger-payload-job/SKILL.md) to trigger payload validation jobs on the draft revert PR and collect the resulting URLs. Pass:

• pr_url: The draft revert PR URL
• jobs: The failing_jobs list for this candidate (includes job_name, is_aggregated, underlying_job_name for each job)

1.4: Record Experiment

Use the payload-results-yaml skill to append an action entry to the candidate's actions array:

• type: "experiment"
• status: "pending"
• revert_pr_url, revert_pr_state: "draft", payload_jobs, result_summary: "", jira_key: "", jira_url: ""

See the payload-results-yaml skill for the full schema.

Throttling: Never test more than 5 candidates. If there are more than 5, test only the top 5 by confidence score.

Job triggering limits: Across all experiments combined: trigger at most 5 non-aggregated jobs and at most 1 aggregated job. Prioritize jobs from higher-confidence candidates.

When a candidate is processed but all of its jobs were skipped due to these limits (i.e., none were actually triggered), do NOT leave it with status: "pending". Instead set:

• status: "deferred"
• payload_jobs: one entry per skipped job with command set and test_url, test_prow_url all set to "skipped_due_to_limits"
• result_summary: "All jobs skipped due to cross-experiment triggering limits"

When a candidate has some jobs triggered and some skipped, mark the triggered jobs normally and add entries for skipped jobs with the "skipped_due_to_limits" marker so the record is complete. The action's status should be "pending" in this case (it has real jobs to check).

Candidates beyond the top 5 that were never processed at all should get an action entry with:

• type: "experiment"
• status: "deferred"
• result_summary: "Deferred — exceeded maximum of 5 experimental candidates"

Update Payload Results YAML

After all Phase 1 subagents complete, use the payload-results-yaml skill to update the results file at results_yaml_path with the action entries for each candidate that was processed or deferred.

Update autodl JSON

Use the payload-autodl-json skill's "Update Experiment Status" Phase 1 operation to update the autodl JSON file for each candidate that had a draft revert PR created.

Phase 2: Collect Results and Act

Phase 2 is invoked after a CI wait period (typically 1-4 hours). If the results YAML contains any action entry with type: "experiment" and status: "pending", enter Phase 2. Phase 2 processes only pending experiments — candidates with other statuses are left unchanged.

2.1: Read Payload Results YAML

Read the results YAML at results_yaml_path using the payload-results-yaml skill. Find all candidates that have an action entry with type: "experiment" and status: "pending". Skip actions with status: "deferred" — these had no jobs triggered and cannot be evaluated.

2.2: Check Job Results

For each pending experiment action:

1. Fetch the test_url from the action's payload_jobs
2. Check for "AllJobsFinished" status on the page
3. If not finished, leave the action's status as "pending" — do NOT change it. The caller can invoke Phase 2 again later to re-check.
4. If finished, check individual prow job results (pass/fail) by fetching each test_prow_url

2.3: Act on Results

For each completed experiment:

PASS (payload jobs pass with the revert applied — the revert fixed the problem):

The candidate PR is confirmed as the cause. Execute:

1. Create TRT JIRA bug: Same format as stage-payload-reverts Substep 1
2. Promote draft to real PR:

   gh pr ready <draft_pr_url>
   

   Update the PR title to include the JIRA key and remove any "NO-JIRA" placeholder:

   gh pr edit <draft_pr_url> --title "<jira_key>: Revert #<pr_number> \"<pr_title>\""
   

   Update the PR body to include the JIRA reference and full Revertomatic template.
3. Update the action entry: status: "passed", revert_pr_state: "open", jira_key, jira_url

FAIL (payload jobs still fail with the revert applied — the PR is innocent):

1. Post a comment on the draft PR explaining the result:

   Experiment result: payload jobs still fail with this PR reverted. This PR is not the cause of the
   blocking job failures in {payload_tag}. Closing this draft.
   

2. Close the draft PR:

   gh pr close <draft_pr_url>
   

3. Update the action entry: status: "failed", revert_pr_state: "closed"

ALL FAIL (no single revert fixes the problem):

If all experiments fail, close all remaining draft PRs and note in the result summaries that the failures may be caused by an interaction between multiple PRs or by infrastructure issues.

2.4: Update Payload Results YAML

Use the payload-results-yaml skill to update the results file at results_yaml_path:

• For each completed candidate, update the relevant action entry's status, result_summary, revert_pr_state, jira_key, jira_url
• Candidates whose jobs are still running keep their action entry's status: "pending" (unchanged)

2.5: Update autodl JSON

Use the payload-autodl-json skill's "Update Experiment Status" Phase 2 operation to update the autodl JSON file for each completed experiment.

Return results to the caller. If any candidates remain pending, inform the caller that Phase 2 should be re-invoked later to collect remaining results.

Error Handling

• If a revert PR cannot be created (e.g., fork issues), skip that candidate and record the error.
• If payload job triggering fails, record the error but keep the draft PR open for manual testing.
• If the pr-payload-tests URL cannot be extracted, record the draft PR URL and note manual checking is required.
• Do not let one failed experiment block processing of others.

See Also

• Related Skill: payload-results-yaml - Schema and operations for the payload results YAML
• Related Skill: revert-pr - The git revert workflow (plugins/ci/skills/revert-pr/SKILL.md)
• Related Skill: trigger-payload-job - Triggers payload jobs and collects URLs (plugins/ci/skills/trigger-payload-job/SKILL.md)
• Related Skill: stage-payload-reverts - Stages high-confidence reverts (plugins/ci/skills/stage-payload-reverts/SKILL.md)
• Related Command: /ci:payload-experiment - Command for experimental reverts (plugins/ci/commands/payload-experiment.md)