Does it work with my AI coding agent?

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.

What does UNPROVEN mean?

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.

Does my code leave my machine?

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.

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

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.

What ships today vs. what's coming?

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.

All releases

Aug 6, 2026 · v0.4.0

Only the Verification Layer

Breaking, despite being a minor. The refactoring product this package grew out of has been removed: six commands, the 20 AST transforms, the interactive TUI, blast-radius scoring and the tier taxonomy. They were the demo of the verification engine, not the product. verify-diff and the MCP tool are untouched.

Om Sherikar

Refactron is now only a verification layer. verify-diff and the verify_change MCP tool are exactly what they were in 0.3.0, down to the report shape. Everything that surrounded them, the refactoring product this package grew out of, has been removed from it.

Under semver a 0.x release may carry breaking changes in a minor, and this one does. Read the Removed section before upgrading: there is no major-version bump to warn you, so ^0.3.0 will not pull this in but refactron@latest will. The 0.3.0 entry below says nothing was renamed, removed, or redefined. That was true of 0.3.0 and is explicitly untrue of this release.

Removed

Six commands, the transforms behind them, and the interactive UI.

Removed	Was
`refactron analyze`	scan for transform patterns, blast radius, tier
`refactron run`	plan, verify and apply transforms
`refactron document`	generate docstrings and changelog prose
`refactron rollback`	undo the last applied refactor
`refactron preflight`	SQLAlchemy 1.x to 2.0 safety report
`refactron init`	scaffold `.refactronrc.json`
bare `refactron`	the interactive Ink REPL

Also removed: the 20 AST transforms and their LibCST sidecars, the autofix fixers, blast-radius scoring, the tier taxonomy, the .refactron/ session store, the legacy verification engine, the language-adapter layer, and the src/core/models.ts and src/adapters/interface.ts locked contracts.

Why: they were the demo of the verification engine, not the product. They were also most of the package. What remains is about a sixth of the source and all of what people install it for.

Changed

Bare `refactron` prints help and exits 2 instead of opening the TUI.
An unknown command exits 2 and says so, rather than failing to resolve a module.
`refactron login` is a real command. Previously only login --print-token was dispatched, and it discarded the status callback, so the device code and verification URL were never displayed. Status now goes to stderr, which keeps --print-token pipeable.
`--help` describes this product. It advertised six departed commands and called Refactron “safety-first refactoring”, the pre-pivot positioning.

Added

A library entry point. main and types have pointed at dist/index.js since before 0.2.0, but no such file existed, so import { verifyDiff } from 'refactron' never resolved. src/index.ts now exports verifyDiff, RefactronVerifier, checkPythonSyntax, checkTypescriptSyntax, reportCoverage, the VerdictReport type and the contracts.ts surface.
A help-drift test. tests/unit/cli/help-drift.test.ts asserts that every verb the help advertises is actually dispatched, against the built binary.

Fixed

`build:copy-py` could fail silently. Its trailing || true bound to the whole && chain, so a failure to copy the *verification* sidecars exited 0: green build, green CI, then every Python verdict failing at runtime against a missing sidecar. The build now asserts all three sidecars reach dist/.

Internal

18 unused runtime dependencies dropped, including ink, react, ts-morph and the three tree-sitter packages. Five remain.
The pre-merge gate no longer runs analyze src/ against this repo. It gates the shipped artifact instead. It deliberately does not run verify-diff against this repo either: coverage attestation is Python-only, so a TypeScript repo verifying itself caps at UNPROVEN permanently.

TransformId still lists the 20 transform literals. Narrowing a locked contract in the same release that restructures the repo would make any regression un-bisectable, so it waits for a later major.