Chisel

Test impact analysis and code intelligence for LLM agents.

Chisel maps tests to code, code to git history, and answers: "what to run, what's risky, who touched it."

The Problem

An LLM agent changes engine.py:store_document(). It then either:

• Runs all 287 tests (slow, wasteful), or
• Guesses with -k "test_store" (misses regressions)

When multiple agents (or agents + humans) work on the same codebase, changes in one area silently break another. Chisel gives agents the intelligence to understand the blast radius of their changes before they commit.

Install

pip install chisel-test-impact

Or from source:

git clone https://github.com/IronAdamant/Chisel.git
cd Chisel
pip install -e .

Use with Claude Code (MCP)

Add to your Claude Code MCP config (~/.claude/settings.json or project .mcp.json):

{
  "mcpServers": {
    "chisel": {
      "command": "chisel-mcp",
      "env": {
        "CHISEL_PROJECT_DIR": "/path/to/your/project"
      }
    }
  }
}

Or run the HTTP server for any MCP-compatible client:

chisel serve --port 8377

Once connected, Claude Code can use all 15 tools directly — analyze, diff_impact, suggest_tests, risk_map, and more. Run analyze first to build the project graph, then diff_impact before each commit to know exactly which tests to run.

Use with Cursor / Other MCP Clients

Chisel exposes a standard MCP interface. For stdio-based clients:

pip install chisel-test-impact[mcp]
chisel-mcp

For HTTP-based clients, point them at http://localhost:8377 after running chisel serve.

Quickstart (CLI)

# Analyze a project (builds all graphs)
chisel analyze .

# What tests are impacted by my current changes?
chisel diff-impact

# What tests should I run for this file?
chisel suggest-tests engine.py

# Who owns this code?
chisel ownership engine.py

# What files always change together?
chisel coupling storage.py

# Which tests are stale?
chisel stale-tests

# Risk heatmap across the project
chisel risk-map

# Incremental update (only re-process changed files)
chisel update

# Find code with no test coverage, sorted by risk
chisel test-gaps

Try It on This Repo

git clone https://github.com/IronAdamant/Chisel.git
cd Chisel
pip install -e .

chisel analyze .
chisel risk-map
chisel diff-impact
chisel test-gaps
chisel stats

15 Tools

Tool	What it does
analyze	Full project scan — code units, tests, git history, edges
update	Incremental re-analysis of changed files only
impact	Which tests cover these files/functions?
diff_impact	Auto-detect changes from git diff, return impacted tests
suggest_tests	Rank tests by relevance + historical failure rate
churn	How often does this file/function change?
ownership	Who wrote this code? (blame-based)
who_reviews	Who maintains this code? (commit-activity-based)
coupling	What files always change together?
risk_map	Risk scores for all files (churn + coupling + coverage gaps)
stale_tests	Tests pointing at code that no longer exists
test_gaps	Code units with zero test coverage, sorted by risk
history	Commit history for a specific file
record_result	Record test pass/fail for future prioritization
stats	Database summary counts

Features

• Zero dependencies — stdlib only, works everywhere Python 3.11+ runs
• Encoding-safe — handles non-UTF-8 content in git history (Latin-1 commits, binary diffs) without crashing
• Multi-language — Python, JavaScript/TypeScript, Go, Rust, C#, Java, Kotlin, C/C++, Swift, PHP, Ruby, Dart
• Framework detection — pytest, Jest, Go test, Rust #[test], Playwright, xUnit/NUnit/MSTest, JUnit, XCTest, PHPUnit, RSpec, Minitest, gtest, Dart test
• Incremental — only re-processes changed files via content hashing
• MCP servers — both stdio and HTTP for LLM agent integration
• Risk scoring — weighted formula: churn, coupling, coverage gaps, author concentration, test instability
• Branch-aware — diff_impact auto-detects feature branch vs main

Ecosystem

Chisel works standalone or alongside Stele for multi-agent code coordination. Chisel handles test intelligence; Stele handles document-level context and conflict prevention.

License

MIT