> ## Documentation Index
> Fetch the complete documentation index at: https://docs.artbucket.io/llms.txt
> Use this file to discover all available pages before exploring further.

# 0010: v1 is frozen by a test, not a promise in prose

> Accepted, v1.0.

## Context

"We won't break the API" is a sentence. Breaks happen through small edits
nobody flags: a field made optional, a max length lowered, an enum value
dropped.

## Decision

The surface is kept as data in `contract/`: the OpenAPI paths and every MCP
tool's input schema at the moment they were frozen. lib/contract.ts compares
the current surface with it by the rules in
[Stability](/developers/stability): inputs may only accept more, outputs may
only promise more. The test suite checks the branch's own copy; CI checks the
base branch's, so re-freezing in the same change can't hide a break.

## Consequences

* Additions have to be frozen too (`pnpm contract:freeze`), so what ships in
  1.1 is as fixed as what shipped in 1.0.
* The comparison is structural. A change of meaning with the same shape is
  still caught only in review.