churnmap

Coupling heatmap generator — visualize co-change risk in any git repo.

churnmap is a dead-simple CLI that analyzes any git repository's co-change history and generates a two-tab interactive HTML report — a coupling heatmap and a D3 force graph — plus a machine-readable JSON file. It is the open-source CodeScene replacement for local, ad-hoc coupling audits.

One command, two files. No signup, no external service, no Kubernetes.

Install

pip install churnmap

Or with uv:

uv tool install churnmap

Usage

# Analyze the current directory
churnmap

# Analyze a specific repo with custom settings
churnmap \
  --repo /path/to/repo \
  --output-dir ./my-report \
  --lookback-days 180 \
  --min-occurrences 5 \
  --heatmap-limit 30 \
  --format both \
  --open

Output is written to ./coupling-report/:

coupling-report/
├── index.html    # Two-tab interactive report (Heatmap + Force Graph + Table)
└── report.json   # Machine-readable JSON with meta + pairs envelope

Flags

Output

• index.html — self-contained, three-tab D3-powered report. Heatmap tab shows top-N files by max coupling score with color-coded cells. Force Graph tab shows file relationships with node size = churn and edge thickness = coupling score. Table tab lists top pairs.
• report.json — envelope with meta (repo name, generation date, lookback days, total commits analyzed, churnmap version) and pairs (all coupling pairs above min_occurrences, sorted by score descending).

Config file

Drop a .churnmap.yml in your repo root to set defaults:

lookback_days: 90
min_occurrences: 3
heatmap_limit: 50
top_files: 100
format: both
low_threshold: 0.3
high_threshold: 0.7
open: false
exclude:
  - "docs/**"
  - "*.md"
  - "migrations/**"

CLI flags override config file values.

How it works

1. coupling-core parses the git history, builds a co-change matrix, normalizes scores into the 0–1 range, and returns a RepoAnalysis.
2. DataPreparer turns the analysis into a heatmap matrix, force-graph nodes/links, and a table-pairs list.
3. HtmlRenderer renders a Jinja2 template containing embedded JSON data and D3.js (loaded from CDN).
4. JsonWriter emits the machine-readable envelope.
5. OutputWriter creates the output directory and writes both files.

Report screenshot

┌──────────────────────────────────────────────────────────────┐
│  ChurnMap — Meru143/churnmap                                  │
│  Total pairs: 42  •  Max score: 0.91  •  Commits: 342         │
│                                                                │
│  [ Heatmap ]  [ Force Graph ]  [ Table ]                       │
│  ─────────                                                     │
│                                                                │
│       src/  src/  src/  ...                                    │
│       a.py  b.py  c.py                                         │
│  a.py  ▓▓   ░░    ▒▒                                           │
│  b.py  ░░   ▓▓    ▓▓                                           │
│  c.py  ▒▒   ▓▓    ▓▓                                           │
│                                                                │
└──────────────────────────────────────────────────────────────┘

Used alongside

• couplingguard — PR-time coupling warning as a GitHub Action. Same coupling-core engine, complementary surface.

License

MIT