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Project	Deployment	Actions	Updated (UTC)
docs	Skipped		May 16, 2026 0:18am

PR Summary

Medium Risk
Moderate risk: changes idempotency semantics for webhookIdempotency/pollingIdempotency so duplicate calls may now return undefined instead of a cached body, which could break any hidden callers relying on the replayed result. Stream trimming is a straightforward Redis ZSET maintenance change but affects retention behavior under load.

Overview
Prevents unbounded Redis growth by trimming mothership stream event history on every appendEvents call via ZREMRANGEBYRANK, enforcing the existing COPILOT_STREAM_EVENT_LIMIT.

Adds storeResultBody to IdempotencyService and configures webhookIdempotency and pollingIdempotency to persist only a small completion marker (not the operation result), so duplicates short-circuit without caching large response payloads. Updates the session buffer test to assert trimming occurs on append.

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Greptile Summary

This PR fixes two Redis memory drivers behind the 2026-05-15 OOM incident: it strips the full workflow result from webhook/polling idempotency keys (only a { success, status } marker is stored), and activates the previously-dead ZREMRANGEBYRANK trim inside appendEvents so mothership stream ZSETs are now bounded by COPILOT_STREAM_EVENT_LIMIT.

• service.ts: Introduces storeResultBody config option (defaults to true); both webhookIdempotency and pollingIdempotency singletons set it to false. Duplicate calls still short-circuit; callers of those two instances are verified to discard the return value.
• buffer.ts: Adds pipeline.zremrangebyrank(key, 0, -config.eventLimit - 1) immediately after zadd, trimming the sorted set to the newest eventLimit entries on every append.
• buffer.test.ts: Flips the trim assertion from not.toHaveBeenCalled (reflecting the previous dead-code state) to a positive expectation that zremrangebyrank is called with the correct key and index pair.

Confidence Score: 5/5

Safe to merge — both changes are targeted, well-reasoned, and address a confirmed production OOM.

The ZREMRANGEBYRANK stop index (-eventLimit - 1) is arithmetically correct: when the set is under the limit the resulting rank is negative and Redis returns an empty range (no-op); at and above the limit it evicts the correct surplus. All callers of webhookIdempotency and pollingIdempotency are await-without-capture, so the undefined returned on duplicate calls is silently discarded exactly as intended. The test mock's handling of negative stop indices matches real Redis semantics. No behavioural regressions are visible on any changed path.

No files require special attention.

Important Files Changed

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Incoming webhook or polling event] --> B{atomicallyClaim}
    B -->|first time| C[execute operation]
    C --> D{storeResultBody?}
    D -->|true - default| E[store result + body in Redis]
    D -->|false - webhook/polling| F[store marker only: success + status]
    E --> G[return actual result]
    F --> G

    B -->|duplicate - completed| I[return existingResult.result - undefined if storeResultBody=false]
    B -->|duplicate - in-progress| J[waitForResult polls - returns undefined if storeResultBody=false]
    B -->|duplicate - failed| K[throw or retry]

    subgraph trim [appendEvents buffer.ts]
        L[pipeline.zadd] --> M[pipeline.zremrangebyrank 0 to -eventLimit-1 - keeps newest eventLimit entries]
        M --> N[pipeline.expire and set seq]
    end

_{Reviews (1): Last reviewed commit: "chore(redis): trim verbose comments on i..." | Re-trigger Greptile}