## Summary
Synthesise QUEUED/FAILED responses from the mollifier buffer when a
TaskRun row hasn't landed in Postgres yet. Wires the synthesis into:
- `ApiRetrieveRunPresenter`
- v1 trace GET route
- v1 spans GET route
- attempts route gains a GET loader (fixes pre-existing Remix "no
loader" 400)
The `readFallback` infra itself lives on the trigger PR (consumed by
`IdempotencyKeyConcern`); this PR adds the route-level
synthetic-rendering primitives.
Stacked on the replay PR.
## Test plan
- [x] \`pnpm run typecheck --filter webapp\` passes
- [x] \`pnpm run test --filter webapp
test/mollifierSyntheticRedirectInfo.test.ts\` passes
- [x] \`pnpm run test --filter webapp
test/mollifierSyntheticSpanRun.test.ts\` passes
---------
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
## Summary
The trigger hot path's mollifier integration:
- `mollifyTrigger`: when the gate trips, write the engine.trigger
snapshot to the buffer and return a synthesised QUEUED response.
Postgres write is deferred to drainer-replay (next PR in the stack).
- Pre-gate idempotency-key claim: same-key triggers serialise through
Redis so a burst lands in PG / buffer exactly once.
- Read-fallback extensions: `findRunByIdWithMollifierFallback` for the
trigger-time idempotency lookup that must see buffered runs.
- Gate bypasses: `debounce`, `oneTimeUseToken`,
`parentTaskRunId`/`triggerAndWait` skip the mollify path entirely.
- `triggerTask` + `IdempotencyKeyConcern` wired to the above.
All behaviour gated by the master `TRIGGER_MOLLIFIER_ENABLED` switch;
off-state hot path is unchanged (the gate is not even consulted).
Stacked on the buffer extensions PR.
## Test plan
- [x] \`pnpm run typecheck --filter webapp\` passes
- [x] \`pnpm run test --filter webapp test/mollifierMollify.test.ts\`
passes
- [x] \`pnpm run test --filter webapp
test/mollifierIdempotencyClaim.test.ts\` passes
- [x] \`pnpm run test --filter webapp
test/mollifierReadFallback.test.ts\` passes
- [x] \`pnpm run test --filter webapp test/mollifierGate.test.ts\`
passes
- [x] \`pnpm run test --filter webapp test/engine/triggerTask.test.ts\`
passes
---
## Ship-gate follow-up fixes
- **Batch items bypass the mollifier gate** — fixes
`BatchTaskRunItem_taskRunId_fkey` FK violation on batch triggers when
the gate trips. End-state is a drainer-side `BatchTaskRunItem`
create-on-materialise; batch traffic passes through the gate until that
lands.
- **IdempotencyKeyConcern honours buffered-run TTL on expiry** —
buffered path now clears expired idempotency claims (read-side) and
resets the buffer's `mollifier:idempotency:*` SETNX binding (write-side)
so a re-trigger past the customer's TTL lands as a fresh run instead of
echoing the stale buffered runId.
---------
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Chris Arderne