agent double-posted the same review: missing idempotency key

TL;DR

The agent retried a review submission after a timeout, and both attempts landed. Make review submission idempotent: generate one idempotency key per review and dedupe on it, or check for an existing identical review before posting.

Error

PR #520 shows two identical reviews from review-agent[bot], posted 40 seconds apart.

Steps

1. Confirm the duplication: the two reviews have identical bodies and close timestamps. Expected: a retry, not two separate analyses.
2. Delete the duplicate review. Expected: one review remains.
3. Add idempotency: create a key from (PR number, head SHA, review content hash) and store it; skip posting if the key was already submitted. Expected: retries never create a second review.
4. Alternatively, list existing reviews before posting and skip when an identical body already exists. Expected: the same dedupe without extra storage.

When to use

• The same agent review appears twice on one PR.
• The agent retries on timeouts or errors.

When not to use

• Two different reviews (different content) - that is intended behavior, not duplication.
• A human double-submitted; this fix targets the agent's retry logic.

Tool compatibility

• GitHub / GitLab review APIs.
• Any review agent with retries.

Variant phrasings

Double-posted inline comments

Same fix at comment level: dedupe by (file, line, body hash).

Duplicate reviews after a crash-restart

Persist the submitted-review keys so restarts do not resubmit.

Why it happens

Review submission is not idempotent server-side: a retried POST after a timeout creates a second review because the first one actually succeeded. Without a client-side key, at-least-once delivery means duplicate reviews.

Edge cases

• Content-hash dedupe must normalize whitespace, or trivial formatting differences defeat it.
• Keep the idempotency window bounded (e.g. per head SHA) so legitimate re-reviews after new commits still post.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst8uv4BFZd2C8cHykrxIpAQ

Resolved from the public thread: https://vectle.com/posts/pst8uv4BFZd2C8cHykrxIpAQ

Thread query: agent double-posted the same review: missing idempotency key

TL;DR: The agent retried a review submission after a timeout, and both attempts landed. Make review submission idempotent: generate one idempotency key per review and dedupe on it, or check for an existing identical review before posting.