bratch

For agents that risk regressing prior work. bratch reads a revision pair (the change about to be made vs the prior baseline) against a regression-signature taxonomy and emits a tri-state verdict: HISTORICAL-BUG (this change matches a pattern that broke things before), CLEAN, or MALFORMED. The signature taxonomy is closed (9 variants at v0.1); the prompt library evolves continuously via empirical-lift evaluation, so the same bratch verify invocation gets stricter at catching regression-signatures as the corpus matures.

Prompt lookup tool. Agent names a regression signature from a fixed list; bratch returns the prompt for that regression signature. The prompt tells the agent how to check the diff against a baseline for that regression.

Built for agentic loops. Reads a diff buffer, matches against a closed regression-signature taxonomy, writes a verdict directive on stdout, exits with a discriminating code so the calling agent can branch on whether a regression was found.

bratch compare       check a diff against a baseline for regression signatures; exit 0 / 1 / 2 / 64
bratch signatures    list the supported regression-signature identifiers
bratch init          scaffold a manifest in the current directory
bratch update        self-update to the latest published version
bratch tail          stream recent verdict transcripts
bratch explain       print taxonomy and exit-code reference

Exit code contract: 0 no regression, 1 regression detected, 2 internal error, 64 malformed input.

Install

cargo install --git https://github.com/bvasilenko/bRatch

Use

bratch compare --signature null-check-removed --diff ./PR-feature-x.diff
# stdout: REGRESSION-DETECTED: null-check-removed. ...
# exit: 1

Optional flags: --diff <path>, --history <path-or-name>, --manifest <path>, --json, --quiet, --reason <text>. Subcommands consume the same flag set; defaults are sane.

Regression-signature taxonomy

Closed RegressionSignature enum. The taxonomy is fixed at this version; widening lands in a later version.

| Category | Variants | |---|---| | Engineering | null-check-removed, error-handling-narrowed, test-assertion-weakened, scope-boundary-broken, invariant-violated | | CMS-context | brand-voice-loosened, banned-term-re-introduced, disclosure-line-deleted, approved-fact-replaced |

bratch signatures prints the full list.

The v0 corpus shipped with this release is hand-authored fixture material. An empirically evolved corpus ships in a later cycle; upgrading is handled automatically via bratch update once the signed-manifest endpoint is live.

Configuration

| Environment variable | Purpose | Default | |---|---|---| | BSUITE_UPDATE_BASE_URL | Base URL for the bratch update manifest fetch | https://updates.example.invalid/bratch/v1 (deliberately non-resolving; production URL ships with the first signed-manifest release) | | BSUITE_TRANSCRIPT_DIR | Override the per-OS default transcript directory | OS default (Linux: $XDG_STATE_HOME; macOS: ~/Library/Application Support; Windows: %LOCALAPPDATA%) | | BSUITE_TRANSCRIPT_RETENTION_DAYS | Days of transcript history to retain | 90 |

License

MIT.