LeanToken

Code intelligence for agents: find the code that matters and keep your context window and tokens lean.

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• MCP Registry name: mcp-name: io.github.morluto/leantoken

Install · Why LeanToken · Tools · CLI · How it works · Docs

Measured token savings: In a controlled 60-run study, LeanToken used 20.1% fewer model input tokens than the agent's built-in tools with limited repository exploration, and 37.6% fewer than those tools with broad exploration. See exactly how it was measured in the measurement methodology.

Quick start

Add LeanToken to Claude Code, Cursor, OpenCode, Codex, Gemini CLI, or Antigravity:

npx leantoken setup

Restart or reload the configured clients, then verify the connection and first retrieval from a repository:

npx leantoken doctor

Try a broad task such as: Find the code related to request cancellation before editing. LeanToken helps the agent start with leantoken.context, while its normal tools remain available for edits, builds, and tests.

Inspect LeanToken's observed repository-local token accounting:

npx leantoken savings

npx leantoken setup --claude --codex --yes
npx leantoken setup --all --yes

npx leantoken setup --codex --cursor --dry-run

npx leantoken remove

npx leantoken runtime list
npx leantoken runtime prune --dry-run
npx leantoken runtime prune --yes

npx --yes leantoken@latest setup --refresh --yes
npx --yes leantoken@0.1.8 setup --refresh --yes --allow-outdated

Common agent workflows

LeanToken works best as a small evidence loop rather than a one-shot repository dump:

1. Orient autonomous triage in one call. Start an uncertain broad task with context and plan_only: false, then use the materialized evidence directly. Make at most one focused follow-up only when coverage identifies a concrete missing implementation or regression-test owner.
2. Continue without resending source. Pass the prior receipt_id on the next context call, or pass returned fragment hashes as known_hashes. The response reports exact and overlapping omissions instead of silently charging the same evidence again.
3. Investigate an observed failure. Use the investigation workflow and provide only directly observed failure_traces, paths, symbols, or test intent in workflow_evidence. Follow with exact search, outline, or read calls for the owners the evidence identifies.
4. Review a change. Use the review workflow with base_revision set to BASE..HEAD and strict_changed_paths: true. Request a handoff when another agent needs a compact manifest of selected hashes, changed paths, assumptions, and completed validations without copied source bodies.

This one-call contract is for autonomous repository triage, not a limit on implementation agents. Human review and control-plane flows can still preview expensive or high-risk retrieval with plan_only: true before materializing. The repeated multi-agent context suite found that an iterative LeanToken profile used 50.9% more total input than thin native, while the frozen one-context-plus-optional-one-search profile saved 20.1% and had 15/20 path-set successes. Those results cover four pinned triage tasks; they do not prove a universal implementation workflow.

Explicit focus constraints are contracts. When a request supplies focus_paths, exact focus_symbols, and minimum_fragments_per_focus_path, LeanToken generates candidates within the documented per-file bounds and reports a coverage failure when distinct ranges cannot satisfy the minimum. Explain-profile plans and materialized responses also identify the bounded allocation boundary that generated, reserved, selected, or suppressed each focus candidate without changing ranking.

Why LeanToken

Most agents start by searching widely and reading whole files. LeanToken narrows that work in stages:

Your coding agent still handles editing, commands, tests, and conversation. LeanToken finds and returns the code those tasks need.

LeanToken does not create one giant prompt file. It answers focused searches and reads as the agent needs them.

Example

For a task like fix request cancellation during shutdown, an illustrative bounded result might look like this:

Budget: 1,200 source tokens

Selected evidence:
  src/services/executor.rs        lines 137-147, 251-259
  src/services/reconciliation.rs lines 148-175, 257-272

The agent receives these ranges instead of both full files. If the budget is too small, the response also says what was left out. Paths, scores, receipts, JSON, and MCP transport wrappers are not part of this source-token budget; see token accounting for the measured boundaries.

Available tools

The catalog stays intentionally small because every tool description and schema also consumes model context.

CLI usage

Run LeanToken directly through npx:

npx leantoken status
npx leantoken savings
npx leantoken doctor
npx leantoken --root /path/to/repo search handle_request

Or use a globally installed binary:

npm install --global leantoken@latest

leantoken --root /path/to/repo index
leantoken --root /path/to/repo search handle_request --mode identifier --max-tokens 800
leantoken --root /path/to/repo context \
  --task "fix request cancellation during shutdown" \
  --budget 2000

Audit an existing redacted experiment or host report without opening a repository index:

leantoken episode audit \
  --adapter multi-agent-suite-v1 \
  --input benchmarks/reports/multi-agent-context-suite-v1-codex-0.144.1.json

The default projection is Markdown; add global --json for the stable normalized JSON schema. The auditor is local, bounded, and read-only with respect to its input. It retains artifact hashes, not raw prompts, source, tool arguments, or tool outputs.

npm install leantoken installs the command in the current project's node_modules/.bin; it does not add leantoken to the shell PATH. Invoke a project-local install through npx leantoken, a package script, or ./node_modules/.bin/leantoken.

Run the MCP server manually over stdio:

leantoken --root /path/to/repo mcp

{
  "mcpServers": {
    "leantoken": {
      "command": "leantoken",
      "args": ["--root", "/path/to/repo", "mcp"]
    }
  }
}

For the Cargo distribution, install the published crate and point your MCP client at the resulting executable:

cargo install leantoken --version VERSION
leantoken --root /path/to/repo mcp

The official MCP Registry entry is io.github.morluto/leantoken. Registry clients that support Cargo packages can install the matching leantoken version and use the mcp command shown above.

Installation options

The npm package includes native binaries for:

• macOS on ARM64 and x64
• glibc Linux on ARM64 and x64
• Windows on x64

Installation does not run lifecycle scripts or download an executable from a postinstall hook. Other targets, including musl Linux, must build from source. Install Rust 1.95 or later and a native C/C++ toolchain, then run:

cargo install --locked --git https://github.com/morluto/leantoken leantoken

Updating

MCP entries created through npx stay pinned to the exact LeanToken version that configured them. Update existing client integrations explicitly:

npx --yes leantoken@latest setup --refresh --yes

For a globally installed CLI or a CLI installed with Cargo:

leantoken upgrade --check
leantoken upgrade --yes

update is an alias for upgrade. For a project-local npm installation:

npm install leantoken@latest

Pinned MCP entries never silently move to @latest. If the exact package is not available locally or online, startup fails rather than selecting another version. Updating the CLI does not change existing MCP entries. See the usage guide for rollbacks, cache management, and version details.

Cache management

Inspect local repository caches or preview cleanup before applying it:

leantoken cache list
leantoken cache list --summary
leantoken cache list --incompatible-with-current
leantoken cache prune --incompatible-with-current
leantoken cache prune --older-than 30 --dry-run
leantoken cache prune --max-total-bytes 1073741824 --yes

See the usage guide for cache states, pagination, and cleanup safety rules.

How it works

repository
    │
    ▼
file discovery ──► code structure extraction ──► local search index
                                                    │
                                                    ▼
agent request ──► ranked / exact retrieval ──► focused code within a token budget

LeanToken indexes source once, then serves compact paths, ranked matches, structural outlines, exact source ranges, and task-specific context. It avoids resending unchanged evidence across turns.

Dependency-heavy workspaces can opt into a separate, cache-identified first-party index without changing the default whole-repository behavior:

leantoken --index-include 'src/**' --index-include 'tests/**' index

Status and every retrieval disclose whether the active index is full or scoped, so an empty scoped result is never presented as whole-repository absence. See the usage guide for bounds, cache identity, and MCP registration examples.

LeanToken's goal is to return the code an agent needs with fewer input tokens.

Documentation

License

Licensed under either of the following, at your option:

• Apache License, Version 2.0
• MIT License