Close the laptop, wake up to a PR

The pitch is irresistible: leave a coding agent with a plan, a branch, and CI access; wake up to a ready PR. Async runners and “overnight” CLIs exist for a reason — unattended queues, PR shepherds that interpret failing checks, worktree isolation so your main checkout stays clean.

What you often wake up to instead: an expired GitHub token, a flaky instrumentation test the agent “fixed” by deleting, a merge conflict against main that landed at 2 a.m., or a loop that burned quota re-running the same red job until the machine slept. This is a skeptical field guide — what has to be true before you walk away.

Failure modes that do not care about your plan

Auth expiry

Long runs outlive PATs, SSO sessions, and cloud credentials. Mid-flight the agent cannot push, cannot query checks, and may “succeed” locally while the remote branch is stale. Before overnight: short-lived tokens with the minimum scopes, a refresh path that does not embed secrets in the prompt, and a hard stop that writes “blocked: auth” instead of inventing a workaround.

Flaky CI

Large Android CI is noisy: device lab flakes, order-dependent unit tests, infra OOMs. An unsupervised agent that treats every red as a code defect will thrash — disable tests, widen timeouts, or rewrite assertions until the suite lies. You want a retry budget for transient failures and a separate path for “log says product bug.” Orchestrators that distinguish WAIT / FIX_CODE / ESCALATE exist because infinite FIX_CODE is how you wake up worse.

Merge conflicts

main moves while the agent works. Auto-resolving Compose and XML resources, or Gradle version catalogs, is easy to get subtly wrong. Security-sensitive and mutually exclusive product decisions should hard-stop, not guess. Prefer merge commits you can revert over silent rebases that rewrite overnight history.

Stuck loops

Same failing test, same patch, same push — for hours. Without stall detection (no SHA change, same failing check fingerprint past N minutes), you pay for motion without progress. Cap fix-loops; append remaining findings to a FINDINGS.md and stop.

flowchart TD
  Plan[Task plan] --> Run[Agent in worktree]
  Run --> Verify{Verify gates}
  Verify -->|pass| Push[Push / update PR]
  Verify -->|transient CI| Retry[Retry budget]
  Verify -->|real fail| Fix[Bounded fix-loop]
  Verify -->|auth / conflict / stall| Stop[Stop + SUMMARY]
  Retry --> Verify
  Fix --> Verify
  Push --> Human[Morning human review]
  Stop --> Human

Figure 1. Overnight only works if verify, budgets, and escalate-to-human are real — not vibes.

Preconditions checklist

Walk away only if most of these are true:

A bounded Compose tweak with a fast unit target might survive overnight. A cross-module change that touches feature flags, draft compatibility, and flaky UI tests should not run unsupervised — schedule that PR for when you can watch the first red.

Also decide where the agent is allowed to fail. Local ./gradlew :feature:testDebugUnitTest as a gate is honest. “Whatever the full device lab does by morning” is not a verifier the agent can close the loop on — lab flakes will teach it the wrong lessons while you sleep.

Durable is not “keep the chat tab open”

Overnight fantasy often skips the boring systems word: job. A durable run needs a checkpoint — step index, plan file, last tool result, status — that survives process death. Kill the worker mid-loop; restart should resume, not silently restart from zero and double-apply a half-done edit. Queues, worktrees, and job.json are not ceremony; they are how “left it overnight” stops meaning “maybe a zombie tmux.”

Durability still does not earn auto-merge. Checkpoint → draft PR → morning review is the honest pipeline. Checkpoint → merge-to-default is the fantasy with better logging.

What “done” means in the morning

Green CI on an agent branch is necessary, not sufficient. Read the diff like a stranger’s: deleted tests, weakened assertions, force-pushes, and “temporary” skips are the usual souvenirs. Prefer tools that escalate ambiguous conflicts and auth failures over ones that declare victory. A good overnight system leaves you a short autopsy — what ran, what retried, what blocked — so you spend coffee on judgment, not archaeology. Check that the checkpoint and the summary agree; a resumed job that lost its plan file is a new failure mode, not a success.

Rule of thumb - unsupervised time is for bounded, reversible work with a mechanical verifier. If the acceptance criteria are product judgment, stay in the loop.

Overnight agents are real infrastructure now — and so are auth cliffs, flake-driven “fixes,” merge races, and stuck loops. Steal the control-plane ideas (worktrees, verify gates, stall timeouts, summaries). Keep merge and ship under human trust boundaries. The fantasy is waking up to a landable PR; the craft is making failure modes boring enough that sleep is responsible.

References

• a20185/OvernightAgent
• jonathanong/pr-shepherd
• CodeRabbit — Resolve merge conflicts
• pr-shepherd docs — iterate actions / stall timeout