Replace the loose-EventType grep with a strict-sentinel filter pipeline
per RESEARCH Q3 Code Example Pattern 3:
- Import IncrementalSource from @rrweb/types (new binding alongside the
existing EventType import)
- Filter events for (e.type === EventType.IncrementalSnapshot &&
e.data?.source === IncrementalSource.Mutation)
- Descend into each filtered event's data.adds[*].node.textContent and
search for the page-side-injected 'a29-mutation-sentinel' string
- A29.2: assert sentinelEvents.length >= 1 — proves the captured
mutation came from OUR injection, not from iana.org leftovers
Defense-in-depth preserved:
- A29.3: rrweb emitted at least one Meta event (renumbered)
- A29.4: rrweb emitted at least one FullSnapshot (renumbered)
The previous A29.5 (loose IncrementalSnapshot >=1) is subsumed by the
A29.2 strict-sentinel check (which requires IncrementalSnapshot AND
Mutation source AND injected sentinel — strictly stronger).
Empirical verification (all 33/33 GREEN preserved, A29 flake closed):
- npx tsc --noEmit → 0
- npm test → 183/183 GREEN preserved (Plan 04-02 baseline)
- npm run test:uat → 33/33 GREEN × 5 consecutive runs
- A29 mutationEvents=1 + sentinelEvents=1 in ALL 5 runs (no flake)
A29 historical flake rate of ~2/3 (documented Plan 03-02 + 03-03
SUMMARYs) is closed end-to-end: the iana.org leftover DOM mutations
no longer satisfy A29 because the strict-sentinel filter requires the
EXACT string 'a29-mutation-sentinel' that only the page-side
chrome.scripting.executeScript injection produces.
Pre-checkpoint bundle gates verified (per feedback-pre-checkpoint-
bundle-gates.md):
- Gate 1: Tier-1 FORBIDDEN_HOOK_STRINGS — 13/13 sub-tests PASS, count
unchanged at 12
- Gate 2: SW CSP-safety — new Function=0, eval=0 (Plan 04-02 baseline)
- Gate 3+4: Buffer / window / document counts unchanged from Plan 04-02
(Plan 04-03 modifies tests/ only)
- Gate 5: manifest validates clean against locked DEC-011 Amendment 1
Mark
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