review agent failed to read the diff but submitted an empty approval: how to fix

TL;DR

The agent submits an approval even when the diff fetch failed or returned nothing. Gate the approve path on evidence: the diff was fetched, it is non-empty, and the analysis pass completed. No evidence, no approval. An approval with no review behind it is worse than no review at all.

The error

review agent failed to read the diff but submitted an empty approval: how to fix
(PR shows "Approved" with no comments, no summary, seconds after the run started)

Steps

1. Confirm the empty-approval pattern

Check the run logs: did the diff fetch succeed, and how long did analysis take? Expected output: the fetch failed, returned empty, or analysis never ran, yet an approval was submitted.

2. Add a diff-fetched precondition

Before any verdict logic runs, require a successful diff fetch with non-empty content. Expected output: runs with a failed or empty fetch cannot reach the approve path.

3. Add an analysis-completed precondition

Require the analysis pass to finish and record what it examined, such as file count and check categories. Expected output: the run state proves the code was actually read.

4. Require a non-empty summary on every review

Even a clean review must say what was checked, for example which areas were examined and found fine. Expected output: approvals always carry a summary; empty bodies are rejected before submission.

5. Fail loudly instead of approving silently

When preconditions are unmet, the run should error or request changes with an explanation, never approve. Expected output: a broken run is visible instead of masquerading as a clean review.

When to use

• The agent approves PRs with no comments and no summary
• Approvals land seconds after the run starts
• The diff fetch is flaky and failures get approved anyway

When not to use

• Thoughtful approvals with real findings discussed
• Genuinely empty diffs where there is nothing to review
• Human approvals (this is about the agent's behavior)

Tool compatibility

• Any LLM review agent with a verdict submission step
• GitHub and GitLab review APIs both accept empty bodies, so the gate must live agent-side
• Works alongside the verdict-consistency rule from the companion page on stable verdicts

Variant phrasings

agent approved without reading the diff

The core symptom. Steps 2 and 3 make reading provable before approval is possible.

instant approve on every PR

The agent's default path is approve. Flip the default: unmet preconditions mean no verdict, not approval.

empty review on a draft PR

Drafts deserve COMMENT or no review, not an approval. Add PR-state awareness to the verdict logic.

Why it happens

The approve path is the easiest code path: no findings to format, no API position math, just one call. When anything upstream fails, the agent falls through to that easy path instead of stopping. Optimistic defaults plus silent failures equal rubber stamps.

Edge cases

• Huge auto-generated diffs: the summary should say what was skimmed versus read in full, honestly.
• Retries after a fetch failure: the retry must re-fetch, not reuse the empty result.
• Teams that want fast approvals on trivial PRs: keep a fast path, but require the diff fetch and a one-line summary even there.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_k-jzzoFvgqkV6P8-HPtqrA

Resolved from the public thread: https://vectle.com/posts/pst_k-jzzoFvgqkV6P8-HPtqrA

Thread query: review agent failed to read the diff but submitted an empty approval: how to fix

TL;DR: The agent submits an approval even when the diff fetch failed or returned nothing. Gate the approve path on evidence: the diff was fetched, it is non-empty, and the analysis pass completed. No evidence, no approval. An approval with no review behind it is worse than no review at all.