Drill: performance regression bisect

Overview

Module	ops.07 · drill · ops, docs · Pass 11 · 1 to 2 h
You build	docs/runbooks/PerformanceRegression.md
Tests	course/tests/ops.07 (named below, with why each exists)
Needs	none
Used by	no code call site; this is an independent artifact
Milestone	MS-P11

Key Takeaways

• Tie each claim to the exact platform evidence that Drill: performance regression bisect produces.
• State the owner, success condition, and recovery action before declaring the work complete.
• Record unresolved assumptions so the next review can test them.

How to work this chapter

ol start ops.07
ol tests ops.07
ol check ops.07

---

1. Why now

A performance regression can consume headroom gradually and evade functional tests. A controlled bisect narrows the change while preserving a stable workload.

2. Principles

Use the same machine class, model, request mix, warmup, and sample count. Set a threshold and rerun the candidate commit before declaring it bad.

3. Worked example

Inject the seeded regression, run the saved load profile, identify the first bad revision with git bisect, and repeat base/head/candidate measurements.

4. The artifact and its check

Test	KIND	Checks	Why it matters downstream
test_artifact_paths_are_declared	artifact	Confirms the submitted paths and required evidence exist, so a plausible narrative cannot pass without the reviewable deliverable.

5. Pitfalls

#	Pitfall	Symptom	Caught by
1	The canary advances before the rollback trigger is recorded	The exercise reports success without proving the old format or route can be restored.	test_artifact_paths_are_declared
2	The team watches request errors but omits the migration-specific signal	A partial rollout can corrupt or strand work while the generic health check stays green.	test_artifact_paths_are_declared
3	No owner records the decision and verification evidence	The next on-call cannot tell whether the incident is contained.	test_artifact_paths_are_declared

6. Where it’s used next

Direction	Module	Connection
Back	craft.16	Read this declared prerequisite before producing the artifact; use it to verify the relevant contract or evidence.
Back	ops.06	Read this declared prerequisite before producing the artifact; use it to verify the relevant contract or evidence.

Going further

Resource	What to inspect
Incident drill catalog	Compare this inject with the adjacent failure drills and use the same containment and verification fields.