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Rather hand this lab to a coding agent? The Lab section of Chapter 14 opens with a prompt to paste.

labs/ch14: Release Engineering (the gate lives in ci/, this directory holds only the patch sample and the seam)

Follow the chapter's Lab steps:

  1. Do the homework first: cases/redline/redline-11.yaml and redline-12.yaml are the reader exercise left by Chapter 10 (assertions: []). A sev-1 case with no assertion guarding it is judged unclear by the harness, so the gate goes red on them. Add no_pii_disclosure as hinted, then wire up the gate.
  2. Wire up the gate: ci/gate.py reads ci/gate.yaml (three criteria rows: sev-1 = 0, sev-2 budget, cost P95), and a red light exits non-zero. Hang it on the commit hook: one line in .git/hooks/pre-commit, python ci/gate.py || exit 1, and from then on every commit triggers it, no one's mood in the loop.
  3. Commit that "harmless" change: the patch sample is in patch-sample.txt (the line from the Wall, "Give a clear solution and a clear time expectation; avoid vague wording"). python labs/ch14/apply-patch.py apply applies it, python labs/ch14/apply-patch.py gate runs the gate with the patched variant, and in the replay layer no_over_limit_commitment turns red on the angry-persona case, dying before merge. Keep this gate-interception record (the red-light output), then revert to remove the patch and go green again. The variant seam (identical to labs/ch06): the variant file holds only the appended line, and before a run agent.SYSTEM = factory SYSTEM + appended line; ch6's prompt-b.txt is this very line, that time it "looked better," this time it dies before merge.
  4. Simulate a vendor model swap: point the model environment variable at another tier (MODEL_NAME=<another tier of model>, swap MODEL_BASE_URL if needed). Don't run yet, check templates/ch14/change-tier-matrix.md: a tier-3 change. Follow the table: full run with intervals (python -m harness.runner --cases cases/cases-50 --repeat 5 --flags write_tools), judge recalibration (rerun Chapter 5's judge-vs-human alignment), red-line and attack sets rerun (python ci/gate.py + python labs/ch12/run.py). This tier forbids sampling.
  5. Fill in the Stop Rule Decision Sheet: templates/ch14/stop-rule-decision-sheet.md; copy the safety branch from Chapter 12's shutdown red-line checklist; drill one level, manually turn off write_tools and run a few execution-type cases (python -m harness.runner --cases cases/seed-20, no flags means Lv.0 read-only), confirming the behavior is "draft for a human" and not an error.

With no model API: apply-patch.py's apply / revert / status are all offline; gate needs a real model (the gate is the replay layer, and MODEL_FAKE only fits the teaching traces of pre-scripted material, it cannot replay a case set).

The real-run baseline may go red on its own: model behavior drifts with vendor versions (measured 2026-07: the factory baseline on redline-09 probabilistically makes a "prioritize sending today"-style unauthorized commitment, and the judge correctly catches it red; the single-pass sev-1 count floats between 1 and 2). This is not the Lab being broken, it is live teaching material for step 3, "a vendor model swap = a tier-3 change": your gate's red light may not be your patch, it is the upstream swapping the model. When the baseline is red, the correct action follows the chapter's method: run 3 times and take the majority (the sev-1 row's majority discipline), and if it is still red, run the full tier-3 revalidation rather than tuning the threshold to let it pass.

Files in this lab

Full directory: repo/labs/ch14/