Sourcebook

What is Sourcebook?

Sourcebook is a safety layer for code changes that analyzes git diffs for completeness — it flags files that should have been modified but weren't. It uses rules-based structural detection plus optional AI-powered semantic analysis, with a claim of zero false positives on clean diffs. It is designed for developers and AI agents working in version-controlled repositories.

How to use Sourcebook?

Sourcebook can be used via CLI, as a Claude Code hook, or as an MCP server. For MCP usage, run npx sourcebook serve and add the server configuration to your MCP client. To analyze a diff, run npx sourcebook check with optional flags like --ai (requires ANTHROPIC_API_KEY), --quiet (exit code only), --json, or --branch <branch>. Run npx sourcebook init to set up Claude Code hooks and generate context files.

Key features of Sourcebook

• Detects missing test files when a source file changes
• Identifies sibling modules that import or are imported by changed files
• Flags co-change companions based on historical git commit patterns
• Warns about hub file blast radius (files with many dependents)
• AI analysis catches semantic relationships like field renames needing migrations
• Supports TypeScript/JavaScript, Python, Go, and Rust with full import graph analysis

Use cases of Sourcebook

• Catching missing test updates when a source file is modified
• Ensuring sibling modules and related configuration files are updated together
• Scanning recent commits for previously missed file changes (scan-history)
• Using as a pre-commit hook via Claude Code integration to prevent incomplete commits

FAQ from Sourcebook

What does Sourcebook catch?

Sourcebook detects missing test files, unchanged sibling modules, files that historically co-change, and hub files with wide blast radius. With the --ai flag, it also finds cross-module semantic relationships, field renames needing migrations, and stale validation logic.

Does Sourcebook require an AI model?

No. The rules-based analysis (co-change, test detection, import graph, hub detection) works without an LLM and runs in under one second. The --ai option adds semantic analysis using Claude Sonnet at about $0.012 per run.

What runtime or API keys are needed?

No configuration is needed for rules-based analysis. The --ai flag requires the ANTHROPIC_API_KEY environment variable. Sourcebook reads your repo’s git history and file structure directly.

Which languages are supported?

TypeScript/JavaScript, Python, Go, and Rust have full import graph and git analysis. Rust has partial convention detection. Other languages may work for co-change and test detection but without import graph support.

What is the license for Sourcebook?

Sourcebook is licensed under BSL-1.1 — source-available and free to use, but cannot be offered as a hosted service. It converts to MIT on 2030-03-25.