Question 1

Does it work with my AI coding agent?

Accepted Answer

That's the point. Refactron verifies a diff whoever authored it: Cursor, Claude Code, Copilot, Codex, a codemod, or you. The MCP server ships today, so your agent can call verify_change on its own work before it lands.

Question 2

What does UNPROVEN mean?

Accepted Answer

Your tests pass, but the changed lines aren't actually exercised by any test, so “green” proves nothing. We say so explicitly and list the tests to add, instead of hand-waving.

Question 3

Does my code leave my machine?

Accepted Answer

No. Refactron runs locally against your real test suite in an isolated shadow tree. Nothing is sent to an external service to make the verdict.

Question 4

How is this different from just running my tests in CI?

Accepted Answer

CI tells you the suite went green. It does not tell you whether a single test executed the lines you changed. Refactron checks that after the suite runs, and returns UNPROVEN when the answer is no, so a green run on untested code stops reading as proof.

Question 5

What ships today vs. what's coming?

Accepted Answer

Shipping today: the CLI (npm install -g refactron) and the MCP server, which exposes one tool, verify_change. Changed-line coverage is proved on Python today; a TypeScript diff runs every gate and caps at UNPROVEN. In early access: the hosted CI gate. Verification needs a token, so join early access to get one.

Blog

Your tests passed. That is not the same as your change being safe.

Rebranding Refactron

Latest posts

Your tests passed. That is not the same as your change being safe.

What five real codebases taught us about verifying other people's diffs

We spent two weeks trying to make our own verifier lie

We asked an AI agent to plant bugs in real codebases. Our gate caught both in under a minute.

Rebranding Refactron

Introducing Refactron: the verification layer for AI code change