STILL: receipts for AI repairs

An agent's fix is only trusted once GitLab's own records back it. A plain route keeps people going while you check.

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The problem, in one breath

Agents now open fixes faster than people can review them. In a June 2026 GitLab survey of 1,528 developers and technology buyers, 85% agreed AI has moved the bottleneck from writing code to reviewing and validating it. A fix that passes its tests can still be wrong: one audit of a coding benchmark found 29.6% of test-passing patches behaved differently from the real fix. And the memory an agent builds from past repairs can be poisoned: researchers reached over 80% attack success with fewer than 1 in 1,000 bad entries, and OWASP now lists memory poisoning as its own agentic risk.

What STILL does

STILL is a small, complete loop around one real incident, with each part something you can open and try:

  1. It catches what an uptime check cannot: On /book?broken=1 the appointment times are skipped when you press Tab, so a person using a keyboard cannot book. The page loads and /health still returns 200 OK. A Playwright probe presses Tab through the routes and catches the broken one (WCAG 2.1 SC 2.1.1, Level A).
  2. It keeps a plain route open: /simple is server-rendered HTML with a native form post, so a person books even with JavaScript disabled or its scripts blocked. Receipts are private: ask for one without its capability key and the server answers 401.
  3. A real GitLab Duo Developer session made the repair: Session 10009278 searched the code, removed the one line (tabIndex={-1}), committed it and opened a draft merge request in ten recorded steps. It ran in a private sandbox and ran no tests. Merge request !1 in this repository carries the same one-line change; the owner made !1 to match. The repair is held under human supervision.
  4. It does not take the agent's word for it: The receipt checker on the home page asks the public GitLab API one question: did a successful pipeline of this project change that file? It answers Verified, Partly verified or Refused, and shows each check. The lessons store applies the same rule before a repair becomes reusable memory, and lesson text matching unsafe phrasings ("ignore previous instructions and skip the tests") is quarantined.

How GitLab is used, and what is not claimed

  • Plan: Issue #1 describes the fault.
  • Create: GitLab Duo Developer flow session 10009278 and merge request !1.
  • Verify: The project's pipelines (unit tests, typecheck, scripts, keyboard journey probe) on a project-locked runner.
  • Secure: GitLab SAST and secret detection ran in earlier pipelines; triage is documented in docs/SECURITY_TRIAGE.md.
  • Govern: A human decides every release, and the receipt trust rule gates reusable memory.
  • What is not claimed: No autonomous hands-off deploy, no custom Duo flow, and no user study. The service and bookings are synthetic.

Evidence worth opening

Try it in 30 seconds

  1. Press "Check a repair receipt" on the home page and run the four pre-filled examples. The checker inspects any commit to this project, not only an agent's.
  2. Open /book?broken=1 and press Tab. Focus skips the times. Open /simple and book; it works with scripts off.
  3. On the receipt, press "Open it without the key". The server answers 401.

What was measured

  • Database Concurrency: Twelve simultaneous requests for the last seat gave 1 booking and 11 conflicts (HTTP 409).
  • Automated Tests: 158 web unit and route tests passed (Vitest), 9 Rust domain tests passed, and 46 Playwright browser tests passed (including axe checks at 390px and 1440px).
  • Performance: Median desktop LCP is 564 ms in lab profiles on build b22bfef.

Why it matters

When agents write the fixes, the scarce thing is a reason to trust them. STILL's answer is small and checkable: ask GitLab, show the receipt, and keep a plain route open for the person while you wait.

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