phx-watch-pr

name	phx:watch-pr
description	Watch an Elixir/Phoenix PR for new review comments (bot + human) and CI results via a background watcher that wakes Claude only on real events. Use after opening a PR or pushing, while waiting on CI or reviewers.
effort	medium
argument-hint	<PR number or URL> [--checks-only] [--fix]

Watch PR (Token-Conscious)

Watch a PR's reviews, comments, and CI with a background watcher that wakes Claude ONLY on real events — no foreground sleep loops, no context bloat. The watcher polls quietly in its own process; nothing enters context until something genuinely changed.

Usage

/phx:watch-pr 42                 # watch reviews + comments + checks
/phx:watch-pr 42 --checks-only   # CI only (delegates to gh pr checks --watch)
/phx:watch-pr 42 --fix           # on actionable review, draft fixes too
/phx:watch-pr 42 --codex         # + request Codex cloud review, loop until clean
/phx:watch-pr 42 --codex --codex-rounds 2   # cap re-review rounds (default 3)

Iron Laws

1. NEVER foreground-poll with sleep in the session — use the background watcher (Monitor / run_in_background). Foreground polling bloats context and straddles the 5-min cache TTL
2. Deltas ONLY enter context — never dump full gh JSON. The watcher emits one-line events; read .claude/watch/pr-{n}.jsonl on demand
3. Silence is not success — the watcher MUST emit on PR closed/merged, CI failure, repeated gh errors, and watchdog timeout — not just "new comment". A silent watcher looks identical to a hung one
4. NEVER auto-post replies or auto-push — hand off to /phx:pr-review for responses; show drafts and get approval. ONE exception: passing --codex IS the consent to post the @codex review trigger comment (and its per-round re-requests) — nothing else is ever auto-posted
5. Bound every watch — default MAX_DURATION 3600s (7200s with --codex); always stop on terminal state. Codex rounds are bounded by --codex-rounds (default 3) — each round costs cloud quota

Workflow

Step 1: Parse Arguments

Extract PR number (from number or URL — URL also yields the repo). Detect --checks-only / --fix / --codex / --codex-rounds N. Baseline timestamp = now; events are "new since baseline", so old reviews don't re-fire.

With --codex, preflight first: the PR's repo needs the Codex GitHub connector (not detectable upfront — the codex_timeout event reports its absence). Codex auto-registers PRs when they go ready, so check the PR body's bot reactions BEFORE posting a redundant trigger:

HEAD_AT=$(gh api "repos/{owner}/{repo}/commits/$(gh pr view {n} --json headRefOid -q .headRefOid)" --jq .commit.committer.date)
BOT=$(gh api "repos/{owner}/{repo}/issues/{n}/reactions" | jq -r --arg t "$HEAD_AT" \
  '[.[] | select(.user.login == "chatgpt-codex-connector[bot]" and .created_at >= $t) | .content] | unique | join(",")')

(gh api --jq accepts no --arg — pipe through standalone jq.)

Definitive check first: a bot comment or review containing Reviewed commit: {sha} that matches the current head sha means that state IS reviewed (clean if it says "Didn't find any major issues") — trust it over timestamps, which are client-set and can skew. Then:

Bot reaction since head commit	Action
+1	Current head already reviewed clean — no trigger, no codex round; watch CI/humans only
eyes + a codex review already submitted since $HEAD_AT	Findings already posted — skip the watch; run the codex_review action (Step 3) now
eyes only	Review in flight — do NOT post; export WATCH_CODEX=1 WATCH_CODEX_SINCE=$HEAD_AT (no trigger id) and watch
none (or reactions predate head)	Post the trigger and capture its id:

TRIGGER_ID=$(gh api --method POST "repos/{owner}/{repo}/issues/${PR}/comments" \
  -f body="@codex review" --jq '.id')

Export WATCH_CODEX=1 WATCH_CODEX_TRIGGER_ID=$TRIGGER_ID to the watcher env and set MAX_DURATION 7200. Round counter starts at 1.

Step 2a: --checks-only Path

No custom poller needed — gh pr checks --watch blocks until all checks finish, then exits. Run via Bash with run_in_background: true:

gh pr checks {n} --watch --fail-fast --interval 10

Exit code is the signal: 0 = pass, 1 = fail, 8 = pending. On exit, report the conclusion; on failure, offer /phx:investigate with the failing job log (gh run view {run-id} --log-failed).

Step 2b: Full Watch Path

Start the Monitor tool (preferred — streams each event line back) on:

${CLAUDE_SKILL_DIR}/scripts/watch-pr.sh {n} reviews,comments,checks

Monitor is a deferred tool — load its schema FIRST via ToolSearch (select:Monitor); calling it blind fails with InputValidationError (params are command, description, timeout_ms, persistent — do not invent others). Set timeout_ms = MAX_DURATION × 1000. Where Monitor is unavailable (Bedrock/Vertex/Foundry), run the same script via Bash run_in_background: true — it exits on the first terminal event instead. Stay idle or keep working until an event lands.

Step 3: React Per Event

Event	Action
review / comment (actionable)	Summarize the delta; with --fix draft fixes + mix compile && mix test; route reply drafting to /phx:pr-review {n}
check conclusion failure	Offer /phx:investigate on the failing job
codex_ack	Note "codex is reviewing (~15–20 min on large PRs)"; keep waiting
codex_review	Stop the watcher. Run /phx:pr-review {n} --bots-only (fix → reply → resolve; user approves and pushes). If rounds < --codex-rounds: post @codex review again, restart watcher with the new trigger id, round+1. Else: report remaining findings, stop
codex_clean	Codex is clean (👍 reaction OR a "Didn't find any major issues" bot comment). If checks also green → terminal success "codex + CI clean"; else keep watching CI
codex_timeout	Inform: repo likely lacks the Codex connector; continue as a plain watch
merged / pr_closed / watchdog / watch_error	Stop, report final state

A codex_review whose /phx:pr-review --bots-only fetch finds zero unresolved codex threads also counts as clean (summary-only review).

Step 4: Stop

The watcher self-terminates on terminal states. To stop early: TaskStop the background task or cancel the monitor.

Integration

push / open PR → /phx:watch-pr {n} ──(new review)──► /phx:pr-review {n}
                              ├──────(CI fail)─────► /phx:investigate
                              ├──(--codex: codex_review)─► /phx:pr-review --bots-only → push → re-request → watch (≤3 rounds)
                              ├──(--codex: codex_clean + CI green)─► done: codex + CI clean
                              └──────(merged)──────► done

References

• ${CLAUDE_SKILL_DIR}/references/watcher-mechanics.md — cache TTL math, Monitor vs run_in_background vs ScheduleWakeup, rate-limit notes