---
description: Token optimization via lean-ctx Hybrid (Shell Hook + MCP)
globs: **/*
alwaysApply: true
---

# lean-ctx MCP Tools

Always use lean-ctx MCP tools. Never use the standard equivalents.

## Tool Mapping

| Instead of | Use | Why |
|---|-----|-----|
| `Read` | `ctx_read` | Session caching, 6 compression modes, re-reads cost ~13 tokens |
| `Shell` | `ctx_shell` | Pattern-based compression for git, npm, cargo, docker, tsc |
| `Grep` | `ctx_search` | Compact context, token-efficient results |
| `ls`, `find` | `ctx_tree` | Compact directory maps with file counts |

## ctx_read Modes

- `full` — default, cached read (use for files you will edit)
- `map` — dependency graph + exports + API signatures (use for context-only files)
- `signatures` — API surface only (tree-sitter AST for 14 languages)
- `diff` — changed lines only (use after edits)
- `aggressive` — syntax stripped
- `entropy` — Shannon + Jaccard filtering

Re-reads cost ~13 tokens. File refs F1, F2.. persist across the session.

Set `fresh=true` on ctx_read to bypass cache. Use when: spawned as a subagent, after context compaction, or if you see a [cached] response but do not have the file content in your context.

## Default Strategy

- Reading for context → `map`
- Reading to understand API → `signatures`
- Reading to edit → `full`
- Re-reading → just call `full` again (cache returns ~13 tokens)

## v2.3.0 Scientific Features (automatic)

- **Auto-Delta** — re-reading a changed file sends only the diff (98.9% savings)
- **Bayesian Mode Selection** — learns optimal mode per file type over time
- **BPE Entropy** — entropy filtering uses LLM tokenizer for precision
- **Cross-File Dedup** — `ctx_dedup` with `action=apply` replaces shared blocks with references
- **Boltzmann Cache** — evicts least-valuable entries when token budget exceeded
- **LITM Profiles** — context positioned optimally per LLM model (Claude/GPT/Gemini)

## Session Management

- `ctx_compress` at >10 turns — creates memory checkpoint
- `ctx_metrics` — hard numbers on what was saved
- `ctx_benchmark` — find optimal mode for a file
- `ctx_session load` — on new chat, restore previous session
- `ctx_dedup` — analyze or apply cross-file deduplication

## Proactive Tools

Use without being asked:
- `ctx_compress` — when context grows large, create checkpoint
- `ctx_metrics` — periodically verify token savings

## Write, StrReplace, Delete, Glob

These have no lean-ctx equivalent — use them normally.

## CRP v2 — Compact Response Protocol

Every token costs money. This applies to input, output, AND thinking tokens.

### Thinking Reduction (saves 30-60% thinking tokens)

1. Parse task first, then act. Don't explore when you already know the answer.
2. One hypothesis, test it. Don't enumerate 5 approaches — pick the most likely, try it.
3. Stop thinking when you have the answer.
4. Use structured context. lean-ctx headers tell you deps/exports — don't re-read files to find imports.
5. File ref tracking: F1=auth.ts means F1 everywhere in this session.

### Output Reduction (saves 50-80% output tokens)

1. NO prose. Just code and results.
2. NO echoing content that was just read.
3. Summarize tool results: 1 line max.
4. Show edits only — not surrounding unchanged code.
5. Batch tool calls. One message, multiple calls.
6. Never ask "shall I proceed?" — just do it.
7. Bullets > paragraphs. Tables > lists.

### Compact Notation

- `F:path` — reading file
- `+file` = created, `~file` = modified, `!file` = error
- `->` for results: "Built -> 18 pages, 0 errors"

## Model Selection

- Grep/search/explore → `model: "fast"`
- Simple edits (rename, add field, fix typo) → `model: "fast"`
- Multi-file refactors, architecture → default model
