# CommitBrief v1.9.0

> An opt-in `commitbrief mcp` subcommand runs a Model Context Protocol server over stdio so an AI agent or host can call CommitBrief as a self-review gate before it submits code. It exposes one `review` tool that runs the exact same pipeline as `commitbrief --json` and returns the structured findings. Stdlib-only — no MCP SDK, no new dependency.

Released June 20, 2026

Canonical URL: https://commitbrief.com/changelog/v1.9.0/

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## Added

- **MCP server: `commitbrief mcp` (ADR-0028).** A new opt-in subcommand runs a
  **Model Context Protocol** server over stdio (JSON-RPC 2.0) so an AI agent or
  host — Claude Desktop, an agent runtime, an MCP-aware IDE — can invoke
  CommitBrief as a tool. The typical use is a **self-review gate the agent runs
  before it submits code**. It is **stdlib-only** (`encoding/json` + `bufio`
  line framing; no MCP SDK, no new dependency) and implements `initialize`,
  `tools/list`, `tools/call`, and `ping`.
- It exposes one tool, **`review`**, that runs the *same* review pipeline as
  `commitbrief --json` — diff acquisition, filtering, the pre-send guard and
  secret scanner, the cost preflight, the cache, the flaky-test pre-pass, and
  signal control — and returns the **structured findings (JSON schema v1)** plus
  a short text summary. The tool arguments expose the meaningful knobs
  (`staged` / `unstaged` / `diff` / `provider` / `model` / `fail_on` /
  `min_severity` / `no_flaky`).
- A `fail_on` gate is reported in the summary (the findings are still returned);
  a genuine failure — no repo or changes, a provider error, an aborted guard —
  comes back as an MCP tool error. The path **reuses `runReview`** rather than
  re-implementing the review, so there is zero behavioral drift from a terminal
  review. Fully additive — existing commands are unchanged.