LeanCTX MCP Server

Content

LeanCTX MCP Server connects Claude and other coding agents to a local context-engineering layer. The server exposes ctx_* tools for compact file reads, shell-output compression, code search, code graph analysis, context packages, persistent session memory, multi-agent handoffs, token accounting, verification, and context-budget control.

The project is local-first and runs as the user. Its security documentation describes project-root path jailing, explicit allow roots, secret-like path checks, output caps, deterministic redaction, JSON-RPC size limits, optional update checks, and opt-in anonymous stats sharing.

Source Review

• https://github.com/yvgude/lean-ctx
• https://github.com/yvgude/lean-ctx/blob/main/README.md
• https://leanctx.com/docs/getting-started
• https://registry.npmjs.org/lean-ctx-bin
• https://github.com/yvgude/lean-ctx/releases/tag/v3.7.5
• https://github.com/yvgude/lean-ctx/blob/main/rust/src/mcp_stdio.rs
• https://github.com/yvgude/lean-ctx/blob/main/rust/src/server/registry.rs
• https://github.com/yvgude/lean-ctx/blob/main/docs/reference/generated/mcp-tools.md
• https://github.com/yvgude/lean-ctx/blob/main/SECURITY.md
• https://github.com/yvgude/lean-ctx/blob/main/docs/guides/claude-code.md
• https://github.com/yvgude/lean-ctx/blob/main/docs/guides/codex-cli.md
• https://github.com/yvgude/lean-ctx/blob/main/LICENSE

These sources were reviewed on 2026-06-06. Prefer the live repository, README, getting-started docs, npm registry metadata, release page, stdio transport implementation, tool registry, generated MCP tool reference, security policy, and license for current install paths, tool counts, transport behavior, security boundaries, optional network activity, and licensing.

Features

• Local Rust binary distributed through release archives, npm lean-ctx-bin, Homebrew, Cargo, AUR, and other upstream-supported install paths.
• MCP server configured by lean-ctx onboard or lean-ctx setup.
• Stdio transport implementation for MCP clients.
• Context tools for file reads, directory maps, code search, deltas, shell compression, cache operations, token accounting, and context retrieval.
• Graph and architecture tools for symbols, call graphs, impact analysis, route discovery, code smells, and project overviews.
• Session memory, knowledge, task, handoff, multi-agent, and workflow tools.
• Context package, verification, proof, feedback, metrics, and budgeting tools.
• Security controls for project-boundary path jailing, allow roots, secret-like paths, output caps, redaction, message limits, and role-based restrictions.
• Apache-2.0 license.

Installation

Install the binary through npm:

npm install -g lean-ctx-bin

Run the guided setup:

lean-ctx onboard

Or configure a compatible MCP client manually:

{
    "mcpServers": {
      "lean-ctx": {
        "command": "lean-ctx"
      }
    }
  }

Review the generated MCP client config, shell hooks, and per-project settings before enabling LeanCTX across all AI clients. Run lean-ctx doctor after setup and restart your shell and AI tool once so MCP tools and hooks load cleanly.

Use Cases

• Let Claude read large source files through compact map, signature, diff, task, or cached full modes.
• Compress noisy shell output from git, npm, cargo, Docker, kubectl, Terraform, and similar tools before it reaches the model.
• Search a codebase, inspect symbols, trace call graphs, and estimate impact without repeatedly dumping full files into context.
• Persist task facts, decisions, handoffs, and session memory across long coding sessions.
• Build context packs for pull requests, reviews, debugging, or multi-agent handoffs.
• Track token savings, context utilization, and tool-level cost attribution.

Safety and Privacy

LeanCTX runs locally, but it sits directly between an AI agent and the user's repository. Treat it as a privileged developer tool. Its MCP tools can read files, summarize directories, search code, compress command output, persist session data, and execute shell commands that the user or agent invokes.

Keep project-boundary enforcement on unless you intentionally allow more roots. Review role settings before enabling unsafe I/O, ignored-file search, command execution, team-server access, or context-package export. For sensitive repositories, disable optional update checks and any opt-in stats sharing, and store session data and context packages under the same controls as source code.

Even compressed outputs can disclose source code, secrets, filenames, incident details, architecture, customer names, or unreleased product plans if sent to an MCP client and model. Do not ask the agent to read credentials, private keys, tokens, .env files, ignored files, or unrelated directories unless that access is explicitly approved and scoped.

Duplicate Check

Existing MCP content includes code-search, repository-context, and coding-agent helpers, but no dedicated LeanCTX, lean-ctx, lean-ctx-bin, or yvgude/lean-ctx MCP entry was found in content/mcp. LeanCTX MCP Server is distinct because it documents the local Rust binary's context compression, stdio MCP server, code graph, session memory, shell-output compression, verification, and token-accounting workflows.