Page 8 of 8~112 min topic

A/B test lab

Run acceptance tests and make the ship call

A second person can reproduce after 20k sessions, v2 groundedness +2.1pp, p95 latency +80ms within budget from a clean checkout and name the owner for AB-SRM-FAIL-27.

~14 min this pageProduction ship gate

1Try it yourself

Decision drill

A/B test lab

Split traffic and measure quality — not every change needs an experiment, but behavior shifts do.

Experiment rigor71%

1/3New system prompt — 50/50 traffic.

2Learn the idea

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Clean-room demo

From a fresh clone/directory, run the commands that prove after 20k sessions, v2 groundedness +2.1pp, p95 latency +80ms within budget. A second person plays experiment owner measuring groundedness lift with SRM checks and follows your script without coaching. The demo includes limitations: what support-answer service comparing retriever_v1 vs reranking retriever_v2 still will not do.

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Evidence pack

Bundle: contract snippet, passing tests, metric snapshot for groundedness_lift_pp and srm_pvalue, security negative probe, rollback note, owner name. Reference AB-SRM-FAIL-27 as the drill you rehearsed. If any item is missing, the ship gate fails even if the happy path dazzles.

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Implementation artifact

python analyze_ab.py --exp retriever_ab_2026q3 --min-n 20000 --srm-guard

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Ownership and next review

For A/B test lab, name the human who gets paged, the review date for thresholds, and the condition that triggers reevaluation. Endpoint POST /v1/support/answer remains the production surface you operate for support-answer service comparing retriever_v1 vs reranking retriever_v2 — not a slide. Keep AB-SRM-FAIL-27 in the handoff template so the next owner inherits the drill.

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Stage depth

After the peer demo, schedule the next threshold review date. File a short changelog that mentions AB-SRM-FAIL-27 and the control that addresses it. Archive the evidence pack where your team already stores launch records. Resist rewriting everything “for real production” in one weekend — operate this slice until the metrics bore you, then widen. Final self-check: if telemetry vanished, would you still know to hold? If yes, you learned the operating posture this lane teaches.

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Field notes for `ab-test-lab` / `mastery-ship`

Trim the demo script until every command is necessary. Record a peer signature line: name, date UTC, pass/fail. File known limitations as bullets, not apologies. Link the evidence pack from the README. Schedule the next game day on a calendar, even if it is solo. Archive the branch tag or release digest you actually shipped. In this chapter the product is support-answer service comparing retriever_v1 vs reranking retriever_v2, the human stakeholder is experiment owner measuring groundedness lift with SRM checks, and the incident id you design against is AB-SRM-FAIL-27. Re-state the oracle in your notes — after 20k sessions, v2 groundedness +2.1pp, p95 latency +80ms within budget — and keep the invariant visible: assignment sticky by user_id; analysis gated on sample ratio mismatch (SRM) p>0.001 fail. Track groundedness_lift_pp and srm_pvalue as the scoreboard. Surface under change control: POST /v1/support/answer. If you only have forty minutes, finish the fixture for reassignment every request → users flicker; metrics uninterpretable before polishing UI. Promotion language stays ternary: promote, hold, or roll back based on evidence, not hope.

Go deeper

Before you start

Why this matters

Draft a two-minute demo script that proves after 20k sessions, v2 groundedness +2.1pp, p95 latency +80ms within budget from a clean directory. Include the failure rehearsal for reassignment every request → users flicker; metrics uninterpretable and the rollback/owner line. If the script needs tribal knowledge, the lab is not shipped.

Check your understanding

Page assessment

Answer from memory. Completion is saved from this evidence, not from opening the next page.

1. Can a peer reproduce without coaching?
2. Does the pack include groundedness_lift_pp and srm_pvalue and rollback?
3. Is ownership for AB-SRM-FAIL-27-class events explicit?

All responses are required.