CI gates for AI-generated PRs need re-derivable evidence

Agent Gate v0.2.1 adds evidence snapshots to AI-generated pull request findings, enabling third parties to re-derive why a CI gate fired. The GitHub Action checks deterministic merge evidence without using LLMs at runtime, and the new feature provides canonical material alongside stable finding IDs for auditability. The developer behind Agent Gate aims to make failure modes visible, reproducible, and tunable before promoting warnings to merge gates.

When a CI gate flags an AI-generated PR, the important question is not only "what did it flag?" It is also: "Could someone else come back later and re-derive why this finding fired?" That is the reason I added evidence snapshots to Agent Gate v0.2.1. Agent Gate is a GitHub Action for AI-generated pull requests. It does not review code with an LLM. It checks deterministic merge evidence in CI: The Action does not checkout PR code, call LLMs at runtime, or execute repository scripts. In v0.2.0, Agent Gate added stable finding IDs. That gave every finding a short audit handle, for example: agf 987ab9ddb8c1b299 That is useful for references, comments, future override workflows, and log-based debugging. But an ID by itself is not proof. If someone sees the ID later, they still need to know what recorded material produced it. v0.2.1 adds evidenceSnapshot to public findings. The split is: findingId = short audit handle evidenceSnapshot = canonical material used to derive that handle The snapshot is intentionally boring. It contains stable rule material such as: It does not include timestamps, report order, risk score, version, commit SHA, or mutable display text. Example compact log output: Agent Gate: NEEDS HUMAN DECISION Decision: warn Risk score: 49 / 100 Why: Agent-generated PRs must include an agent-gate contract. Recommended next step: Add a PR contract before relying on scope checks. Policy status: warning today; eligible to become a merge gate after tuning. Findings: - error agf be0c2c2a66312aff contract/missing - error agf 987ab9ddb8c1b299 risk/high-risk-path .github/workflows/agent-gate.yml - warn agf 6016e753491255d7 workflow/dangerous-pattern .github/workflows/agent-gate.yml The compact log stays short, but the JSON and Markdown reports carry the fuller evidence. Example JSON shape: { "findingId": "agf 987ab9ddb8c1b299", "ruleId": "risk/high-risk-path", "severity": "error", "path": ".github/workflows/agent-gate.yml", "evidenceSnapshot": { "ruleId": "risk/high-risk-path", "severity": "error", "path": ".github/workflows/agent-gate.yml", "evidence": { "label": "changed file", "value": ".github/workflows/agent-gate.yml" } } } For me, the bar for promoting a finding from warning to blocking is: A third party should be able to re-derive the finding from recorded evidence. That does not mean the check is magically correct. It means the failure mode is visible, reproducible, and tunable. A repo can start in warn mode, observe which findings are useful, and only later promote low-noise findings into merge gates. Agent Gate still does not prove semantic correctness. Matching test-file evidence is not proof that the tests cover the behavior. It is change evidence / self-consistency evidence. Maintainer override storage is also not implemented yet. That is probably the next hard design question: if someone bypasses a finding, where should that override live so it is durable enough to inspect later? CODEOWNERS / reviewer evidence and package dependency drift are also future work. If you maintain a repo where coding agents open PRs, I would love feedback on whether this kind of evidence is useful or too noisy in observe mode. Repo: https://github.com/sjh9714/Agent-Gate https://github.com/sjh9714/Agent-Gate Disclosure: I maintain Agent Gate. v0.2.1 is still a prerelease; I would start in warn mode before treating any finding as a merge gate.