yvgude--lean-ctx/README.en.md

<div align="center">

<pre>
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</pre>

### **Control what your AI can see.**

**LeanCTX — Lean Context Engineering for AI agents**

LeanCTX — short for **Lean Context** — is the context engineering layer for
AI agents. It runs as a single local binary between your agents and everything
they touch — your code, shell, data, and the model itself: it **decides** what
they read, **compresses** what they send (an optional local proxy shrinks every
request — system prompt, history and tool results — prompt-cache-safe),
**remembers** what they learn, **guards** what they touch — and **proves** what
they save with a signed, verifiable savings ledger. The result: 60–90% fewer
tokens. 
Zero config required.
Local-first.

| Problem | With LeanCTX |
|---------|-------------|
| Repeated file reads: ~2000 tokens each | Cached re-reads: **~13 tokens** |
| Raw `git status`: ~800 tokens | Compressed: **~120 tokens** |
| Every turn re-sends the whole history | Proxy compresses each request, **prompt-cache-safe** |
| Context resets every chat | Session memory persists across chats |
| No visibility into context usage | Real-time dashboard + budget control |

---

<p>
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  <a href="https://crates.io/crates/lean-ctx"><img src="https://img.shields.io/crates/d/lean-ctx?color=%23e6522c" alt="Downloads"></a>
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</p>

<p>
  <a href="https://leanctx.com">Website</a>&nbsp;&nbsp;·&nbsp;&nbsp;<a href="https://leanctx.com/docs/getting-started">Docs</a>&nbsp;&nbsp;·&nbsp;&nbsp;<a href="#get-started-60-seconds">Install</a>&nbsp;&nbsp;·&nbsp;&nbsp;<a href="#use-it-from-your-own-code-sdks">SDKs</a>&nbsp;&nbsp;·&nbsp;&nbsp;<a href="#real-world-scenarios">Scenarios</a>&nbsp;&nbsp;·&nbsp;&nbsp;<a href="#demo">Demo</a>&nbsp;&nbsp;·&nbsp;&nbsp;<a href="#benchmarks">Benchmarks</a>&nbsp;&nbsp;·&nbsp;&nbsp;<a href="cookbook/README.md">Cookbook</a>&nbsp;&nbsp;·&nbsp;&nbsp;<a href="SECURITY.md">Security</a>&nbsp;&nbsp;·&nbsp;&nbsp;<a href="CHANGELOG.md">Changelog</a>
</p>

</div>

---

> **Control what your AI can see.** LeanCTX — short for **Lean Context** — is the **context engineering layer** for AI agents: one local Rust binary that decides what your agents read, compresses what they send to the model, remembers what they learn, guards what they touch — and proves what they save.

> Token savings are the receipt. Intelligence is the product. Works with **Cursor, Claude Code, Copilot, Windsurf, Codex, Gemini** and 30+ other agents — no config needed.

<p align="center"><strong>See it in action:</strong></p>

<table>
  <tr>
    <td align="center" width="33%">
      <img src="assets/leanctx-demo.gif" width="320" alt="Map-mode file read + compressed git output demo">
      <br/>
      <strong>Read + Shell</strong>
      <br/>
      Map-mode reads + compressed CLI output
    </td>
    <td align="center" width="33%">
      <img src="assets/leanctx-gain.gif" width="320" alt="lean-ctx gain live dashboard demo">
      <br/>
      <strong>Gain (live)</strong>
      <br/>
      Tokens + USD savings in real time
    </td>
    <td align="center" width="33%">
      <img src="assets/leanctx-benchmark.gif" width="320" alt="lean-ctx benchmark report demo">
      <br/>
      <strong>Benchmark proof</strong>
      <br/>
      Measure compression by language + mode
    </td>
  </tr>
</table>

<p align="center"><sub>All GIFs are generated from reproducible VHS tapes in <code>demo/</code>.</sub></p>

## Why developers use LeanCTX

- **Longer useful coding sessions** — less context waste = more room for actual code reasoning
- **Lower API costs** — 60–90% fewer tokens on reads and shell output, cached re-reads cost ~13 tokens
- **No more "I already showed you this file"** — session memory persists across chats
- **Works with your existing setup** — one `lean-ctx setup` command, no config changes needed
- **Full visibility** — see exactly where your context window budget goes
- **Model-agnostic & yours** — swap OpenAI/Anthropic/Gemini freely; your context and memory stay local and portable, never locked in a vendor's black box

---

<p align="center">
  <strong>Saves you tokens?</strong> <a href="https://github.com/yvgude/lean-ctx">Give it a star</a> — it helps others discover LeanCTX.
</p>

---

## Why now — own your context

Models are converging on commodity. The durable edge isn't *which* model you call — it's your **context**: what your agents read, what they remember, and what you can prove. And the layer that optimizes and *owns* that context can't come from the vendor that bills per token or keeps your memory in a black box — it has to sit on your side.

That's the shift behind "agent entities" that live in your chat and remember your company (Claude in Slack, ClickUp Brain): a **context login, not a model login** — you end up renting your own company knowledge back. LeanCTX is the opposite layer. It keeps the moat yours: local-first, portable (`.ctxpkg`), and model-agnostic — swap OpenAI, Anthropic or Gemini without losing context or cache. **Own your context; don't rent it back.**

---

## What it does — the four dimensions of context

LeanCTX treats context as a managed resource, not an afterthought. One binary
covers the four dimensions that decide how well an AI agent actually performs:

### 1. Compression — input efficiency

Your AI agent reads files and runs commands. LeanCTX compresses both automatically.

- **File reads**: 10 read modes (`full`, `map`, `signatures`, `diff`, `lines:N-M`, `density:X`, …) — cached re-reads cost ~13 tokens
- **Target density** (`density:0.4`): SDE-style budget compression — keeps the highest-entropy lines until ~40% of the original tokens remain, deterministic
- **JIT disclosure**: `signatures` carries line spans and points at `lines:N-M` for targeted expansion — outline first, bodies on demand
- **Shell output**: 95+ shell-output patterns compress git, npm, cargo, docker, kubectl, terraform and more (270 passthrough rules)
- **Tree-sitter AST**: structural understanding for 27 languages — not just text compression
- **Reversible by design (CCR)**: compression never *discards* content — pruned or truncated payloads move to a content-addressed store with a deterministic handle, so the model can pull the original bytes back on demand via `ctx_expand`, `ctx_retrieve`, an in-band marker, or `GET /v1/references/{id}`. [Five recovery paths →](docs/comparisons/vs-headroom.md#reversibility)

### 2. Routing — the right fidelity per read

Not every file needs the same depth. LeanCTX sends the signal, not the noise.

- **10 read modes**: from full content down to AST signatures and entropy-filtered views
- **Adaptive `ModePredictor`**: learns the optimal read mode per file type from past sessions
- **`IntentEngine`**: classifies query complexity so simple lookups stay cheap

### 3. Memory — context that persists

Context doesn't disappear between chats anymore.

- **Session memory (CCP)**: persist task/facts/decisions across chats — structured recovery queries survive compaction
- **Knowledge graph**: temporal facts with validity windows, episodic + procedural memory
- **Property Graph**: multi-edge code graph (imports, calls, exports, type_ref) powers impact analysis and search ranking
- **Yours, not the vendor's**: memory stays local and portable — export it as a `.ctxpkg` package and move it across machines or models, instead of locking it in a vendor's black box

### 4. Verification — control what reaches the model

Performance is accuracy, not just speed. You stay in control of the window.

- **Context Manager**: browser dashboard with real-time token tracking, compression stats, utilization gauge
- **Budgets & SLOs**: profiles, roles, per-agent budgets, and throttling policies
- **Context Proof** (`ctx_proof`, `ctx_verify`): 4-layer verification engine with CI drift gates

<details>
<summary><strong>Full feature list (81 MCP tools)</strong></summary>

- **Web & Research** (`ctx_url_read`): pull a public web page, PDF, or YouTube transcript into context as compressed, citation-backed text — `facts`/`quotes` return claims with a confidence score + source URL, relevance-ranked research-compression distils to a token budget, SSRF-guarded (http/https only)
- **Graph-Powered Intelligence**: hybrid search (BM25 + embeddings + graph proximity via RRF), incremental git-diff updates
- **LSP Refactoring** (`ctx_refactor`): language-server-powered rename, references, go-to-definition via rust-analyzer, typescript-language-server, pylsp, gopls
- **Multi-Agent** (`ctx_agent`, `ctx_handoff`): agent handoff with context transfer bundles, diary system, synchronized shared state
- **Archive Full-Text Search** (`ctx_expand search_all`): FTS5-powered cross-archive search over all previously archived tool outputs
- **PR Context Packs**: `lean-ctx pack --pr` builds a PR-ready context pack (changed files, related tests, impact, artifacts)
- **Context Packages**: `lean-ctx pack create` bundles Knowledge + Graph + Session into portable `.ctxpkg` files with SHA-256 integrity
- **Context Time Machine**: `lean-ctx snapshot create|list|show|verify|restore|publish|import` — git-anchored, ed25519-signed snapshots of the layer state (lineage, ledger Φ, ROI, session) on an append-only timeline; replay them in the dashboard, `restore` to resume a session (and `--git` to check out the commit), or `publish`/`import` a signed snapshot to share it ([concept →](docs/concepts/context-time-machine.md))
- **Observability**: `lean-ctx gain --live` for real-time savings, `lean-ctx wrapped` for weekly/monthly summaries (`gain --svg`/`--share` for a shareable card or self-hostable page), `lean-ctx watch` for TUI monitoring
- **Verified savings**: `lean-ctx savings` is an auditable, per-event ledger (tokenizer transparency, bounce-netting, tamper-evident SHA-256 chain) — local-only, on by default
- **HTTP mode**: `lean-ctx serve` for Streamable HTTP MCP + `/v1/tools/call` (used by the Cookbook + SDK)

</details>

## Addons — run the ecosystem through one gateway

You don't have to choose between LeanCTX and the other context tools you already
like. An **addon** wraps any MCP server in a tiny `lean-ctx-addon.toml` manifest;
LeanCTX runs it behind its gateway with one command, then treats what it returns
like your own reads instead of just proxying it.

```bash
lean-ctx addon search memory   # browse the registry by category
lean-ctx addon add headroom    # installs the upstream package + wires the MCP server, on add
lean-ctx addon list            # what's wired into your gateway
```

- **One command to add** — `addon add <name>` installs the upstream package via its native manager (uv, pip, cargo, npm, brew, dotnet) and wires the MCP server into your gateway. No fork, no recompile.
- **Folded in, not just proxied** — opt-in post-processing runs addon output through the same pipeline as your code: compress to a budget, spill oversized blobs to a `ctx_expand` handle, index into BM25 / graph / knowledge. Typed adapters route specific tools straight into `ctx_expand`, `ctx_callgraph` and `ctx_knowledge`.
- **Untrusted by default** — every addon's output is scrubbed for secrets and tagged untrusted before it reaches the model. Always on, not a flag.
- **You stay in control** — pin a machine or fleet to verified-only, an allowlist, or off entirely via one `[addons]` policy a single repo can't override.

The registry spans compression (Headroom, Sophon), code intelligence (Repomix,
Serena), memory (Mem0, Cognee, Letta) and reasoning (Sequential Thinking). See the
**[addon guide](docs/guides/addons.md)** or [browse them all](https://leanctx.com/addons/).

## Where it's going

LeanCTX is growing from a single context *layer* into a full **cognitive context
layer** for whole teams: version-controlled context strategy, one unified graph, and a
governance layer across many agents.

- **Context Time Machine → hosted history** — the snapshot engine, dashboard replay, restore, and signed file-based share/import have shipped (see above); next is a `ctxpkg.com` registry for hosted, versioned context history and a side-by-side model-view ｜ git-diff replay. The temporal axis through everything LeanCTX does — it *decides, remembers, guards, proves, and replays*. ([concept →](docs/concepts/context-time-machine.md))
- **Context as Code** — declarative pipelines, profiles, and policies in TOML, versioned like infrastructure
- **Unified Context Graph** — code, tests, commits, CI runs, and knowledge entries in a single semantic graph
- **Agent Harness** — roles, budgets, and tool permissions for multi-agent governance
- **Context Observability** — SLOs on context consumption, anomaly detection, OpenTelemetry / Prometheus export

The full roadmap lives in **[VISION.md](VISION.md)**.

## How it works (30 seconds)

LeanCTX works on **two planes** — what your agents *read* and what they *send to the model*:

```
read path:   AI tool  →  (MCP tools + shell)  →  lean-ctx  →  your repo + CLI
wire path:   AI tool  →  lean-ctx proxy        →  model provider   (every request, compressed)
```

- **MCP server** *(read path)*: exposes `ctx_*` tools (read modes, caching, deltas, search, memory, multi-agent)
- **Shell hook** *(read path)*: transparently compresses common commands so the LLM sees less noise
- **Request proxy** *(wire path, opt-in)*: `lean-ctx proxy enable` puts a local proxy between your agent and the model that compresses **every request** — system prompt, full history and tool results — prompt-cache-safe, with measured USD spend. It can also pin **one reasoning-effort level across OpenAI, Anthropic & Gemini** (`proxy.effort`) without breaking that cache, cut **output** tokens with a cache-safe verbosity steer plus a measured holdout, and **relocate volatile fields** (dates, UUIDs, commit SHAs) out of the cacheable prefix so a stable system prompt finally caches. Every rewrite is reversible (content-addressed recovery) and byte-stable by contract. Same layer as a standalone request-compression proxy (e.g. Headroom) — you don't need one on top.
- **Property Graph**: multi-edge code graph powers impact analysis, related file discovery, and search ranking
- **Session memory**: persists state with structured recovery so long-running work never "cold starts"
- **Context Manager**: browser dashboard for real-time visibility into what's in your context window

## Get started (30 seconds)

```bash
# 1) Install (pick one)
curl -fsSL https://leanctx.com/install.sh | sh      # universal (no Rust needed)
brew tap yvgude/lean-ctx && brew install lean-ctx    # macOS / Linux
npm install -g lean-ctx-bin                          # Node.js
cargo install lean-ctx                               # Rust
pi install npm:pi-lean-ctx                           # Pi Coding Agent

# 2) One-command setup for your agent
lean-ctx wrap cursor      # or: wrap claude / wrap codex / wrap vscode

# Done. Savings appear after your AI's first lean-ctx call.
lean-ctx gain
```

`lean-ctx wrap` installs shell hooks, registers the MCP server, sets up agent hooks, starts the daemon, and verifies the connection — all in one command. Undo anytime with `lean-ctx unwrap cursor`.

<details>
<summary><strong>Alternative: full control</strong></summary>

```bash
lean-ctx onboard          # connect all detected AI tools (zero prompts)
lean-ctx setup            # interactive wizard with every option
```

</details>

**Building from source on Windows?** Clone the repo and run `./install.ps1` in PowerShell — it builds the release binary and installs it into Cargo's bin directory (pass `-BuildOnly` to build without installing).

<details>
<summary><strong>Troubleshooting / Safety</strong></summary>

- Disable immediately (current shell): `lean-ctx-off`
- Run a single command uncompressed: `lean-ctx -c --raw "git status"`
- Only activate in AI agent sessions: set `shell_activation = "agents-only"` in `~/.config/lean-ctx/config.toml`
- Per-project config override: create `.lean-ctx.toml` in your project root (auto-merged with global config)
- Docker projects sharing `/workspace`: create `.lean-ctx-id` with a unique name to prevent context collisions
- Update: `lean-ctx update`
- Diagnose (shareable): `lean-ctx doctor --json`

</details>

## Use it from your own code (SDKs)

Beyond the CLI, lean-ctx ships published libraries so you can call it directly from your app.

**Drop-in prompt compression — [`lean-ctx-sdk`](https://pypi.org/project/lean-ctx-sdk/) ([npm](https://www.npmjs.com/package/lean-ctx-sdk)).** Compress a chat-style `messages` array before it reaches any model — deterministic and prompt-cache friendly; images, tool-calls and ids pass through untouched.

```python
# pip install lean-ctx-sdk
from lean_ctx import compress
messages = compress(messages, model="claude-sonnet-4")
```

```ts
// npm install lean-ctx-sdk
import { compress } from "lean-ctx-sdk";
messages = await compress(messages, { model: "gpt-4o" });
```

Framework adapters included (LiteLLM, LangChain, Vercel AI SDK). → **[compress() cookbook](docs/guides/compress-sdk.md)**

**Thin `/v1` contract clients — [`lean-ctx-client`](https://pypi.org/project/lean-ctx-client/) ([npm](https://www.npmjs.com/package/lean-ctx-client) · [crates.io](https://crates.io/crates/lean-ctx-client)).** Wrap the full `/v1` tool, event and session API over the process boundary — never links the engine, so it stays stable as lean-ctx evolves.

```bash
pip install lean-ctx-client     # Python (imports as `leanctx`)
npm install lean-ctx-client     # TypeScript / Node
cargo add lean-ctx-client       # Rust
```

Start the server with `lean-ctx serve`, then point a client at it. → **[API reference](https://leanctx.com/docs/api-reference/)**

## Real-world scenarios

LeanCTX grows with you. Below are the journeys most people actually take — each
links to a complete, function-by-function walkthrough in the
**[Reference](docs/reference/README.md)** (every CLI command and all 79 MCP
tools are documented there).

<table>
<tr>
<td width="50%" valign="top">

### 🟢 Your first 30 seconds
*"I just installed it — now what?"*

```bash
lean-ctx wrap cursor  # one-command setup for your agent
lean-ctx doctor       # confirm you're wired up
```
One command installs hooks, MCP registration, and verifies the connection.
→ **[Journey 1 — Setup & Onboarding](docs/reference/01-setup-and-onboarding.md)**

</td>
<td width="50%" valign="top">

### 📖 Coding every day
*"Stop re-reading the same files."*

```bash
lean-ctx read src/server.rs -m map   # API surface, ~13 tok on re-read
lean-ctx -c "git status"             # compressed shell output
```
Your agent reads less and searches smarter — automatically.
→ **[Journey 2 — Daily Use](docs/reference/02-daily-use.md)**

</td>
</tr>
<tr>
<td width="50%" valign="top">

### 🧠 Resume where you left off
*"My new chat forgot everything."*

```bash
lean-ctx overview                    # task-aware project recap
lean-ctx knowledge recall "auth"     # facts that survive resets
lean-ctx knowledge consolidate       # import session + compact lifecycle
lean-ctx knowledge consolidate --all # compact every project store
```
Session memory + a project knowledge graph persist across chats.
→ **[Journey 3 — Memory & Knowledge](docs/reference/03-memory-and-knowledge.md)**

</td>
<td width="50%" valign="top">

### 🗺️ Understand a new codebase
*"Where does this function ripple to?"*

```bash
lean-ctx graph impact src/auth.rs    # blast radius
lean-ctx smells scan                 # code-smell hotspots
```
A multi-edge property graph powers impact analysis + ranked search.
→ **[Journey 4 — Code Intelligence](docs/reference/04-code-intelligence.md)**

</td>
</tr>
<tr>
<td width="50%" valign="top">

### 🔌 Providers & multi-repo
*"Pull in GitHub issues and our Postgres schema."*

```bash
lean-ctx provider list
lean-ctx serve --root ./api --root ./web   # multi-repo
```
External data flows through the same consolidation pipeline.
→ **[Journey 5 — Advanced & Integrations](docs/reference/05-advanced.md)**

</td>
<td width="50%" valign="top">

### 🛠️ Keep it healthy
*"Update, fix, or cleanly remove."*

```bash
lean-ctx doctor --fix
lean-ctx update
```
Self-healing diagnostics; surgical uninstall that only removes its own blocks.
→ **[Journey 6 — Lifecycle & Troubleshooting](docs/reference/06-lifecycle.md)**

</td>
</tr>
<tr>
<td width="50%" valign="top">

### 🎛️ Take control of the window
*"Budget my context like a pro."*

```bash
lean-ctx plan "refactor billing" --budget 8000
lean-ctx compile --mode balanced
```
Phi-scored planning + knapsack compilation + a context ledger.
→ **[Journey 7 — Context Engineering](docs/reference/07-context-engineering.md)**

</td>
<td width="50%" valign="top">

### 🤝 Run a team of agents
*"Planner + coder + reviewer on one repo."*

```text
ctx_agent action=register role=dev
ctx_handoff action=create        # baton-pass with full context
```
Shared message bus, diaries, knowledge, and deterministic handoffs.
→ **[Journey 8 — Multi-Agent Collaboration](docs/reference/08-multi-agent.md)**

</td>
</tr>
<tr>
<td width="50%" valign="top">

### 🏢 Share across a team / CI
*"One shared index, headless in pipelines."*

```bash
lean-ctx team serve --config team.toml
lean-ctx bootstrap            # zero-prompt CI setup
```
Scoped tokens, optional cloud sync, verifiable context gates.
→ **[Journey 9 — Team, Cloud & CI](docs/reference/09-team-cloud-ci.md)**

</td>
<td width="50%" valign="top">

### 🎚️ Tune & govern
*"Make it behave exactly how we want."*

```bash
lean-ctx compression standard
lean-ctx harden               # enforce token discipline
```
Compression levels, tool profiles, themes, and rules governance.
→ **[Journey 10 — Customization & Governance](docs/reference/10-customization-and-governance.md)**

</td>
</tr>
<tr>
<td width="50%" valign="top">

### 📊 Prove the payoff
*"Show me the numbers."*

```bash
lean-ctx gain --deep          # savings, cost, per-agent, heatmap
lean-ctx wrapped              # shareable recap (also: gain --svg / gain --share)
lean-ctx savings              # verified per-event ledger (auditable; savings verify)
```
All analytics live in the CLI/dashboard — never burning agent tokens.
→ **[Journey 11 — Analytics & Insights](docs/reference/11-analytics-and-insights.md)**

</td>
<td width="50%" valign="top">

### 📚 The full reference
*"I want to read everything."*

Every command and all 81 MCP tools, organized as user journeys, plus
appendices for the [CLI map](docs/reference/appendix-cli-map.md),
[MCP tools](docs/reference/appendix-mcp-tools.md), and
[paths & config](docs/reference/appendix-paths-and-config.md).
→ **[Reference index](docs/reference/README.md)**

</td>
</tr>
</table>

## Supported IDEs & AI tools

LeanCTX is a standard **MCP server**, so it works with any MCP-compatible client. Two integration modes are auto-selected per agent:

| Mode | How it works | Best for |
|---|---|---|
| **Hybrid** | MCP for cached reads (~13 tokens) + shell hooks for command compression | Agents with shell access (Cursor, Claude Code, Codex, ...) |
| **MCP** | All 80 tools via MCP protocol, no shell hooks | Protocol-only agents (JetBrains, VS Code, Zed, ...) |

### Agent compatibility matrix

| Agent | Hybrid | MCP | Setup |
|---|:---:|:---:|---|
| Cursor | ● | | `lean-ctx init --agent cursor` |
| Claude Code | ● | | `lean-ctx init --agent claude` |
| CodeBuddy | ● | | `lean-ctx init --agent codebuddy` |
| Augment CLI / VS Code | ● | | `lean-ctx init --agent augment` |
| Codex CLI | ● | | `lean-ctx init --agent codex` |
| Gemini CLI | ● | | `lean-ctx init --agent gemini` |
| Windsurf | ● | | `lean-ctx init --agent windsurf` |
| GitHub Copilot | ● | | `lean-ctx init --agent copilot` |
| CRUSH | ● | | `lean-ctx init --agent crush` |
| Hermes | ● | | `lean-ctx init --agent hermes` |
| OpenCode | ● | | `lean-ctx init --agent opencode` |
| Pi | ● | | `lean-ctx init --agent pi` |
| Qoder | ● | | `lean-ctx init --agent qoder` |
| Amp | ● | | `lean-ctx init --agent amp` |
| Cline | ● | | `lean-ctx init --agent cline` |
| Roo Code | ● | | `lean-ctx init --agent roo` |
| Kiro | ● | | `lean-ctx init --agent kiro` |
| Antigravity | ● | | `lean-ctx init --agent antigravity` |
| Amazon Q | ● | | `lean-ctx init --agent amazonq` |
| Qwen | ● | | `lean-ctx init --agent qwen` |
| Trae | ● | | `lean-ctx init --agent trae` |
| Verdent | ● | | `lean-ctx init --agent verdent` |
| Aider | | ● | `lean-ctx init --agent aider` |
| Continue | | ● | `lean-ctx init --agent continue` |
| JetBrains IDEs | | ● | `lean-ctx init --agent jetbrains` |
| QoderWork | | ● | `lean-ctx init --agent qoderwork` |
| VS Code | | ● | `lean-ctx init --agent vscode` |
| Zed | | ● | `lean-ctx init --agent zed` |
| Neovim | | ● | `lean-ctx init --agent neovim` |
| Emacs | | ● | `lean-ctx init --agent emacs` |
| Sublime Text | | ● | `lean-ctx init --agent sublime` |

> **Any MCP-compatible client** works out of the box — the table above shows agents with first-class auto-setup.

### When to use (and when not to)

**Great fit if you...**
- use AI coding tools daily and your sessions are shell-heavy (git/tests/builds)
- work in medium/large repos (50+ files / monorepos)
- want a local-first layer with **no telemetry by default**

**Skip it if you...**
- mostly work in tiny repos and rarely call the shell from your AI tool
- always need raw/unfiltered logs (you can still use `--raw`, but ROI is lower)

The honest fine print: the payoff depends on three levers — **reach** (own the
window via the proxy/engine, not just the `ctx_*` tool layer), **context
lifetime** (one long-lived session vs. a fresh process per phase), and
**provider pricing** (prompt-cache-priced vs. re-billed every turn). They stack
into a clear win where they line up and net to **break-even** where they don't.
See the [win vs. break-even matrix](docs/reference/14-performance-tuning.md#win-vs-break-even-at-a-glance)
for the full breakdown and how to tune for each case.

<a id="demo"></a>

## Demo

Try these in any repo:

```bash
lean-ctx read rust/src/server/mod.rs -m map
lean-ctx -c "git log -n 5 --oneline"
lean-ctx gain --live
lean-ctx dashboard                              # Context Manager (browser)
lean-ctx watch                                  # TUI monitor
lean-ctx benchmark report .
```

- The repo ships the exact tapes used to render the GIFs in `demo/`
- Regenerate locally:

```bash
vhs demo/leanctx.tape
vhs demo/gain.tape
vhs demo/benchmark.tape
```

<a id="benchmarks"></a>

## Benchmarks

Real, reproduced numbers — never estimated. Measured on this repo with the GPT-4o
tokenizer (`o200k_base`); a tool that isn't installed is reported as such, never
guessed.

| Read mode | Compression | Tokens (50 files) | Quality |
|---|---:|---:|---:|
| Raw read | 0% | 533.2K | 100% |
| `map` | **98.1%** | 8.0K | 78% |
| `signatures` | **96.7%** | 14.0K | 96% |
| Cached re-read | ~99.99% | ~13 tok | 100% |

lean-ctx's **own cost is measured too**: the fixed per-session footprint it
injects (advertised tool schemas + MCP instructions) is ~2.1K tokens and
CI-gated via `lean-ctx doctor overhead --gate`, so it can only shrink. And the
long-lived proxy rail has a deterministic self-verify —
`lean-ctx benchmark dual-arm --json` replays a 15-turn session and prices it per
model (digest `f5ed145e61ce3689`, 99.4% input-side saving on cache-priced rails;
methodology: [bench/agent-task/r2](bench/agent-task/r2/README.md)).

Accuracy isn't a vibe: the lossy stages are **CI-gated**. A model-free A/B gate
proves the JSON crusher keeps *every* gold answer while cutting tokens, and proxy
rewrites are byte-stable by contract, so Anthropic (90%) / OpenAI (50%) prompt-cache
discounts survive compression. A deterministic **off-vs-on testbench**
(`lean-ctx eval testbench`) extends the proof to *answers*: it runs pinned real repos
through a raw-dump baseline and through lean-ctx at an identical token budget, grades
free-form QA with an LLM judge and code with each repo's own tests, and emits
`FINDINGS.md` (tokens / turns / walltime / quality) plus a regressions file — with a
committed recorded subset that blocks CI on any regression.

- **Latest snapshot**: [BENCHMARKS.md](BENCHMARKS.md)
- **Reproduce**: `lean-ctx benchmark report .`

## By the numbers

- **3,000+ GitHub stars** — and counting
- **280+ forks** — active community contributions
- **200+ releases** — shipped near-daily since launch
- **30+ supported AI coding agents** — broadest MCP compatibility
- **81 MCP tools** — from simple file reads to multi-agent orchestration
- Used in production by teams running Claude Code, Cursor, and Codex daily
- **Live adoption metrics**: [leanctx.com/metrics](https://leanctx.com/metrics/) — installs, stars and savings, updated continuously

## Docs

- **Reference (every function, by user journey)**: [docs/reference/](docs/reference/README.md) — 11 journeys + CLI/MCP/config appendices
- **For AI agents / LLMs**: [llms.txt](llms.txt) — a curated, machine-readable map of lean-ctx (per the [llms.txt](https://llmstxt.org) convention)
- Getting started: https://leanctx.com/docs/getting-started
- Tools reference: https://leanctx.com/docs/tools/
- CLI reference: https://leanctx.com/docs/cli-reference/
- What is LeanCTX: https://leanctx.com/what-is-leanctx/
- Comparison (vs RTK, Context+, MemGPT): https://leanctx.com/compare/
- Pricing & Cloud (local use is free forever): https://leanctx.com/pricing/
- FAQ: [discord-faq.md](discord-faq.md)
- Feature catalog (SSOT snapshot): [LEANCTX_FEATURE_CATALOG.md](LEANCTX_FEATURE_CATALOG.md)
- Monorepo guide: [docs/guides/monorepo.md](docs/guides/monorepo.md)
- Architecture: [ARCHITECTURE.md](ARCHITECTURE.md)
- Vision: [VISION.md](VISION.md)

## Privacy & security

- **No telemetry by default**
- **Optional anonymous stats sharing** (opt-in during setup)
- **Disableable update check** (config `update_check_disabled = true` or `LEAN_CTX_NO_UPDATE_CHECK=1`)
- **40+ security hardening fixes** in v3.5.16 (path traversal, injection, CSPRNG, CSP, resource limits — [details](CHANGELOG.md))
- **Context Governance Benchmark self-assessment**: graded **C2 — Managed** against the 32-control [CGB v1.0-draft](https://github.com/yvgude/context-governance-benchmark) spec, gaps declared — [docs/compliance/cgb-self-assessment.md](docs/compliance/cgb-self-assessment.md)
- Runs locally; your code never leaves your machine unless you explicitly enable cloud sync

See [SECURITY.md](SECURITY.md).

## Uninstall

One command removes **everything** — it stops all processes, then deletes hooks,
editor configs, rules, autostart (LaunchAgent/systemd), the data dir, **and the
binary itself**:

```bash
lean-ctx uninstall                 # full clean removal
lean-ctx uninstall --dry-run       # preview every change, write nothing
lean-ctx uninstall --keep-config   # keep MCP configs + rules (for reinstall)
lean-ctx-off                       # or just disable for the current shell session
```

No binary on PATH (or you used the curl installer)? Run the same removal from the installer:

```bash
curl -fsSL https://leanctx.com/install.sh | sh -s -- --uninstall
```

If you installed via a package manager, `uninstall` removes everything it wrote and
tells you the one command to finish removing the binary:

```bash
brew uninstall lean-ctx        # Homebrew
cargo uninstall lean-ctx       # cargo install
npm uninstall -g lean-ctx-bin  # npm
pi uninstall npm:pi-lean-ctx   # Pi Coding Agent
```

## Star History

<a href="https://star-history.com/#yvgude/lean-ctx&Date">
  <picture>
    <source media="(prefers-color-scheme: dark)" srcset="https://api.star-history.com/svg?repos=yvgude/lean-ctx&type=Date&theme=dark" />
    <source media="(prefers-color-scheme: light)" srcset="https://api.star-history.com/svg?repos=yvgude/lean-ctx&type=Date" />
    <img alt="Star History Chart" src="https://api.star-history.com/svg?repos=yvgude/lean-ctx&type=Date" />
  </picture>
</a>

## Contributing

Start with [CONTRIBUTING.md](CONTRIBUTING.md). Easy first PR: propose a new CLI compression pattern via the [issue template](.github/ISSUE_TEMPLATE/compression_pattern.md).

## License

Apache License 2.0 — see [LICENSE](LICENSE).


--- lean-ctx: ctx_compose bundles search+read+symbols in one call ---