project-brain-mcp

Standalone MCP server that gives CLI coding agents (Claude Code, Cline, Cursor, opencode) persistent decision memory, codebase dependency-graph awareness, plan validation against architectural constraints, and a self-bootstrapping constraints.md file — backed by a local SQLite database (.project-brain/decisions.db) in each project it's wired into.

CLI agent support status

If you try this with Cline, Cursor, or opencode, please open an issue with what worked / didn't — that feedback directly shapes which agent gets verified next.

Related MCP server: anchor-mcp

Use case scenarios

These are real flows this server enables once wired into a project (the examples below are from testing against a Laravel/PHP codebase, but the same flows apply to any supported language):

• Onboarding into an unfamiliar codebase. Run index_codebase once, then run_bootstrap — the agent walks every module, records its inferred purpose/constraints/caveats via log_module_intent, and generates a draft constraints.md (Architectural Boundaries, Technology Constraints) for you to review and correct.

• "What breaks if I change this?" Before editing a shared model or service, the agent calls get_dependents / get_blast_radius to see every file that transitively depends on it — e.g. confirming that changing app/Models/User.php only affects database/seeders/DatabaseSeeder.php, not half the app.

• Don't repeat past mistakes. When an approach fails (a library doesn't fit, a migration breaks under load, etc.), the agent logs it with log_failure. In a later session, get_context(topic) surfaces that failure before the agent tries the same thing again.

• Plan review against architectural rules. Before executing a multi-step plan, validate_plan(task, steps) checks each step against logged hard constraints and graph-derived boundaries, returning PLAN: blocked with specific fixes if a step would violate one.

• "Where do I even start?" For a feature request described in plain English, find_entry_points(intent) does a semantic search over indexed modules — e.g. intent="HTTP request entry point for the web application" returned the relevant controllers in a Laravel app.

• Tracking structural drift over time. diff_graph(since_commit) shows which dependency edges were added/removed since a given commit — useful after pulling a large set of changes before continuing work.

Supported languages

The code-graph indexer (index_codebase) parses these file types via tree-sitter:

Other file types are indexed as plain nodes but produce no dependency edges.

Prerequisites

• Node.js ^20 || ^22 || >=24

• A git working tree for the project you want to wire this into (most tools work without git, but diff_graph and the incremental CLI ingest path use the current commit hash)

Install & build

git clone <this-repo>
cd code-brain-mcp
npm install
npm run build

This produces dist/src/index.js (the MCP server entry point) and dist/cli/index.js (the project-brain CLI for remote ingest, see below).

Setup in a project

Option A — automated install script (recommended)

From the root of the project you want to add code-brain-mcp to:

/path/to/code-brain-mcp/scripts/install.sh

The script:

1. Detects which agent(s) you use, based on marker files in your project:

   • Claude Code: CLAUDE.md or .claude/

   • Cline: .clinerules or .cline/

   • Cursor: .cursorrules or .cursor/

   • opencode: AGENTS.md or .opencode/

2. Installs/merges the matching skill package from skills/<agent>/ into your project (project-memory instructions + a bootstrap flow), preserving any existing content in those files (code-brain-mcp's block is wrapped in <!-- code-brain-mcp:start/end --> markers).

3. Registers the MCP server in your agent's config (.mcp.json, .cursor/mcp.json, opencode.json). Cline stores MCP config outside the repo — the script prints the entry to add manually via the Cline "MCP Servers" panel.

4. Creates .project-brain/ (the local SQLite database directory) if it doesn't already exist.

5. Installs a .git/hooks/post-commit hook (for the optional remote-ingest workflow, see below).

If no marker file is detected, the script exits with instructions for adding one manually.

Option B — manual config (Claude Code)

Add to .mcp.json (or your global ~/.claude.json under mcpServers):

{
  "mcpServers": {
    "code-brain": {
      "command": "node",
      "args": ["/path/to/code-brain-mcp/dist/src/index.js"]
    }
  }
}

Then copy skills/claude-code/CLAUDE.md and skills/claude-code/bootstrap.md into your project so Claude Code knows how/when to call the tools.

First run

You don't need to type these calls yourself. Once skills/claude-code/CLAUDE.md is installed in your project root (via scripts/install.sh or copied manually), Claude Code auto-loads it every session and treats the steps below as always-on behavior — it calls these tools on its own as part of normal work, and get_session_health() self-corrects if it skips one. The steps below are what happens under the hood, useful mainly for the very first run or for manual/CLI testing.

In a fresh Claude Code session in your project:

1. start_session()

2. get_context(topic="...") — loads project memory, required before other tool calls per the session-health checker.

3. index_codebase(incremental=false) — builds the initial dependency graph.

4. get_bootstrap_status() — if never_run, run run_bootstrap(path) repeatedly (see skills/<agent>/bootstrap.md for the full multi-turn flow) to populate constraints.md with the project's architectural boundaries and technology constraints.

After that, CLAUDE.md (or the equivalent rule file for your agent) describes the always-on behaviors: calling get_dependents/get_dependencies/ get_blast_radius before changing a module, validate_plan before executing a multi-step plan, log_decision/log_failure to build up project memory, etc.

Transport modes

Remote mode env vars: TRANSPORT_MODE, PROJECT_BRAIN_TOKEN, HOST (default 127.0.0.1), PORT (default 8420), SQLITE_BUSY_TIMEOUT_MS (default 5000).

Remote ingest CLI

For the remote-server setup, the project-brain CLI (dist/cli/index.js) pushes graph updates from a separate machine/CI job:

project-brain index --full --push --url https://your-server --token $PROJECT_BRAIN_TOKEN
project-brain index --since <commit> --push --url https://your-server --token $PROJECT_BRAIN_TOKEN

The installed post-commit git hook runs the --since HEAD~1 --push incremental form automatically if PROJECT_BRAIN_URL is set in your environment.

Project memory file: constraints.md

export_constraints_file() generates a human-readable constraints.md at your project root (YAML frontmatter + Architectural Boundaries / Technology Constraints / Flagged-for-review sections). Edit it by hand, then call ingest_constraints_file() to sync your edits back into the database. See constraints.md in this repo for a live example of the format.

A note on secrets

index_codebase never reads or stores raw file contents — it only parses source files (per the extensions listed above) for import/dependency edges, and stores file paths + module names in .project-brain/decisions.db. It never reads .env files or similar.

The decisions/failures/module_intents/constraints tables store free-text written by your agent via log_decision, log_failure, and log_module_intent — avoid having your agent paste secrets/credentials into those calls, the same way you would with any chat. .project-brain/ is already in .gitignore, so this database stays local and is never committed.

Roadmap

• Verify Cline / Cursor / opencode support. Skill packages and install paths exist for all three (skills/<agent>/), but only Claude Code has been tested end-to-end so far.

• Plugin-based language support. Today, adding a language means adding a tree-sitter grammar dependency and a walker function in src/parser/treesitter.ts (see PHP support as the most recent example). The goal is to make this a drop-in plugin interface so the community can add languages (Java/Kotlin for Android, C#/.NET, etc.) without touching core indexer code.

• Composer autoload beyond PSR-4. PHP support currently resolves use statements via PSR-4 only; classmap/files/psr-0 autoload strategies and multi-composer.json monorepos are not yet covered.

• Non-code / document repos. The dependency-graph model is code-specific today (tree-sitter ASTs). An exploratory direction is a parallel "document graph" mode for non-code repositories (e.g. a folder of legal contracts or policy documents) — same decision-memory/constraints-file mechanics, but relationships derived from document structure/references instead of imports. This is an early idea, not yet scoped into a spec.

Contributions and issue reports toward any of the above are welcome.

Development

npm test        # vitest
npm run build   # tsc
npm run dev      # run the server directly via tsx, stdio mode