ctxmap

A self-maintaining context map for AI coding assistants.

ctxmap solves one problem: AI coding assistants re-read your entire codebase from scratch every session.

It generates a single CONTEXT.md — a compressed, always-current map of your repo — that any AI reads at session start instead of scanning files. Updated automatically on every git commit, rewriting only the sections that actually changed.

pip install ctxmap
ctxmap install    # adds CONTEXT.md reference to CLAUDE.md, sets git hook
ctxmap build      # first run — generates CONTEXT.md (~500 tokens)
# from now on: auto-updates on every git commit

The problem

Every time you start a Claude Code session, Claude re-reads the same files to understand your project. Your API layer hasn't changed in months. Your Redux pattern hasn't changed. Your test setup hasn't changed. But Claude re-scans everything anyway — spending thousands of tokens on context that was stable yesterday and will be stable tomorrow.

/init makes this worse: it regenerates your entire CLAUDE.md from scratch every run, overwrites your manual notes, and produces a file that's either too long or missing what actually matters.

How it works

git commit
  → diff file hashes          (instant, no LLM)
  → identify stale sections   (instant)
  → rewrite only those        (~300–600 tokens)
  → Claude reads CONTEXT.md next session (~500 tokens, fixed)

CONTEXT.md has six sections, each independently tracked:

## Project        ← written once, updated only when README changes
## Architecture   ← updated when file/module structure changes
## Conventions    ← updated when code patterns change
## Hot files      ← updated each commit (most-connected files)
## Recent         ← rolling 7-day git log, auto-rotated
## Notes          ← your manual section, NEVER touched by ctxmap

Each section has a hash of its source inputs stored in .ctxmap/section_hashes.json. On every ctxmap update, only sections whose inputs changed get rewritten. A typical commit touching 3 files: recent updates in ~200 tokens, everything else stays cached.

What CONTEXT.md looks like

# myapp — context map
*Generated by ctxmap. Last updated: 2026-04-21.*

## Project
**Repo:** `myapp`
**Language:** TypeScript/React
**Scale:** 47 files · 612 symbols · 2,341 relationships
**About:** Brand management dashboard for enterprise clients.

## Architecture
**Module map:**
- `PrivateAPI.js` (12 fns) → auth, config
- `store/index.js` (8 fns) → reducers, middleware
- `components/Dashboard.jsx` (6 fns) → api, hooks

**Key classes:**
- `AuthManager` in `auth/manager.js` L14
- `APIClient` in `PrivateAPI.js` L8

## Conventions
- Private functions use `_prefix` convention
- Tests use `test_*` naming (34 test functions detected)
- Test files: `src/__tests__/unit/`, `src/__tests__/integration/`
- NOTE: MemoPromise used for API deduplication
- WHY: isSuccess() checks response.metadata.status not HTTP status

## Hot files
- `PrivateAPI.js` — 41 connections
- `store/reducers.js` — 28 connections
- `auth/manager.js` — 19 connections

## Recent
**2026-04-21** — fix: resolve auth token refresh race condition
  - `PrivateAPI.js`
  - `auth/tokenManager.js`

## Notes
<!-- This section is yours. ctxmap never touches it. -->
- Use renderWithProviders from testUtils.jsx for all component tests
- MUI v4 for old components, v5 for new — don't mix in same file
- allowAuthHeaders is dead code in PrivateAPI.js, ignore it

How it works

Real-world benchmark

Tested on gstin-health, a Next.js/TypeScript project:

Token counts measured with tiktoken (cl100k_base). Real savings depend on how much of your codebase a given session would otherwise scan — smaller repos see smaller absolute savings, larger repos see larger.

More importantly: answer quality. Same question, two sessions:

Without CONTEXT.md — generic Next.js boilerplate guess: package.json, app/page.tsx, app/layout.tsx.

With CONTEXT.md — specific, accurate, prioritised: lib/gstApi.ts (31 connections, core of everything), lib/scoreEngine.ts (business logic), app/api/gstin/[gstin]/route.ts (API layer) — in the right order, with the right reasons.

Token economics

Why CONTEXT.md beats CLAUDE.md

CLI reference

ctxmap build              # full build: structural graph + CONTEXT.md
ctxmap update             # incremental: re-parse changed files, patch sections
ctxmap context            # regenerate CONTEXT.md only
ctxmap context --force    # rewrite all sections unconditionally
ctxmap status             # graph stats + token count
ctxmap install            # configure CLAUDE.md + git hook
ctxmap serve              # start MCP server for deep queries

# Deep graph queries (optional)
ctxmap query "auth flow"
ctxmap explain UserService
ctxmap path LoginHandler Response
ctxmap semantic           # LLM extraction on docs/images (needs ANTHROPIC_API_KEY)
ctxmap watch              # auto-update on file changes

Platform support

ctxmap install auto-detects your AI tool and writes the correct config:

Or target a specific platform:

ctxmap install --platform cursor
ctxmap install --platform claude-code

Optional MCP server

For deep queries during a session, ctxmap also runs as an MCP server:

ctxmap serve   # stdio transport — add to .mcp.json

Available tools: get_blast_radius, query_graph, get_node, get_path, get_god_nodes, get_surprising_connections, get_architecture_overview, run_semantic, export_graph.

MCP is optional depth — CONTEXT.md handles the common case without any tooling.

Optional dependencies

pip install ctxmap[semantic]     # LLM extraction for docs/images (Anthropic)
pip install ctxmap[video]        # video/audio transcription (Whisper + yt-dlp)
pip install ctxmap[communities]  # Leiden community detection
pip install ctxmap[embeddings]   # vector similarity search
pip install ctxmap[all]          # everything

Privacy

• Code files: processed locally via Tree-sitter — nothing leaves your machine
• Docs/images: sent to Anthropic API only when you explicitly run ctxmap semantic
• Video/audio: transcribed locally with faster-whisper — never leaves your machine
• No telemetry, no analytics, no tracking of any kind

Architecture

ctxmap/
├── context.py     CONTEXT.md generator — section-level diff updates  ← core
├── parser.py      Tree-sitter AST extraction (structural, no LLM)
├── store.py       SQLite + NetworkX unified store
├── builder.py     SHA-256 incremental build/update/watch
├── semantic.py    LLM extraction with per-file hash cache
├── analysis.py    God nodes, blast radius, surprising connections
├── server.py      FastMCP server + MCP tools
├── installer.py   Platform auto-detection + git hook installation
└── cli.py         CLI entry point

See ARCHITECTURE.md for full details.

Contributing

git clone https://github.com/avstrix/ctxmap
cd ctxmap
python -m venv .venv && source .venv/bin/activate
pip install -e ".[dev]"
pytest tests/ -q

To improve a section: each _build_*_section() in context.py is independent and easy to extend.

Worked examples are the most useful contribution — run ctxmap on a real project, save CONTEXT.md output, write notes on what was useful vs missing, submit a PR.

MIT License.