Inject a controlled incident response failure

Add executable validation at the trust boundaries of correctness incident for invalid RAG citations (SEV2). Reject unknown fields where they matter, bound string sizes, and coerce only after auth/signature checks when raw bytes are security-relevant. Invariant under test: declare early; preserve evidence; mitigation scoped; no blame in channel. A TypeScript type or Python annotation is not runtime validation — pair them with parsers.

Automate the fixtures from setup, including a recreation of INC-RAG-CIT-2201. Assert both the visible error and the absence of side effects (no provider call, no queue write, no flag flip). Where metrics matter, assert label enums stay bounded.

Document which failures are client mistakes (4xx) versus operator/config mistakes (5xx/503). Oracle still stands: INC-RAG-CIT-2201: feature flag off in 8m; customer update sent; groundedness restored. Validation should make accidental “success with empty body” impossible for incident commander coordinating mitigate → communicate → verify.

Property ideas: shuffled field order, Unicode edges, maximum-length strings, and replayed timestamps. Where money, identity, or citations matter, assertion messages should cite the field name. Do not snapshot entire provider payloads in tests; assert semantically. If validation fails open “to keep the demo working,” you have inverted the lab. Tie at least one CI job to the INC-RAG-CIT-2201 fixture so main cannot regress silently. Re-read declare early; preserve evidence; mitigation scoped; no blame in channel after each new parser — convenience helpers love to bypass it.

Table-drive status codes and error codes so reviewers see coverage at a glance. Include a Unicode normalization case if user text is accepted. Verify that oversized bodies fail before CPU-heavy work. Where digests or versions are pinned, assert mismatch behavior. Keep golden files small enough to read in review. CI should fail on skipped tests that mark the incident fixture as xfail without a ticket link. In this chapter the product is correctness incident for invalid RAG citations (SEV2), the human stakeholder is incident commander coordinating mitigate → communicate → verify, and the incident id you design against is INC-RAG-CIT-2201. Re-state the oracle in your notes — INC-RAG-CIT-2201: feature flag off in 8m; customer update sent; groundedness restored — and keep the invariant visible: declare early; preserve evidence; mitigation scoped; no blame in channel. Track time_to_declare_m, time_to_mitigate_m, customer_update_sent as the scoreboard. Surface under change control: POST /v1/rag/answer. If you only have forty minutes, finish the fixture for team debugs for an hour without declaring — customers keep seeing wrong policy cites before polishing UI. Promotion language stays ternary: promote, hold, or roll back based on evidence, not hope.