pi-lean-ctx

Pi Coding Agent extension that routes all tool output through lean-ctx for 60–90% token savings.

What it does

Overrides Pi's built-in tools to route them through lean-ctx:

| Tool | Compression | |------|------------| | bash | All shell commands compressed via lean-ctx's 90+ patterns | | read | Smart mode selection (full/map/signatures) based on file type and size | | grep | Results grouped and compressed via ripgrep + lean-ctx | | find | File listings compressed and .gitignore-aware | | ls | Directory output compressed |

Install

# 1. Install lean-ctx (if not already installed)
cargo install lean-ctx
# or: brew tap yvgude/lean-ctx && brew install lean-ctx

# 2. Install the Pi package
pi install npm:pi-lean-ctx

Binary Resolution

The extension locates the lean-ctx binary in this order:

1. LEAN_CTX_BIN environment variable
2. ~/.cargo/bin/lean-ctx
3. ~/.local/bin/lean-ctx (Linux) or %APPDATA%\Local\lean-ctx\lean-ctx.exe (Windows)
4. /usr/local/bin/lean-ctx (macOS/Linux)
5. lean-ctx on PATH

Smart Read Modes

The read tool automatically selects the optimal lean-ctx mode:

| File Type | Size | Mode | |-----------|------|------| | .md, .json, .toml, .yaml, etc. | Any | full | | Code files (55+ extensions) | < 24 KB | full | | Code files | 24–160 KB | map (deps + API signatures) | | Code files | > 160 KB | signatures (AST extraction) | | Other files | < 48 KB | full | | Other files | > 48 KB | map |

Code extensions include: .rs, .ts, .tsx, .js, .jsx, .py, .go, .java, .c, .cpp, .cs, .rb, .php, .swift, .kt, .vue, .svelte, .astro, .html, .css, .scss, .lua, .zig, .dart, .scala, .sql, .graphql, .proto, .tf, .sh, .bash, .zsh, .fish, .ps1, and more.

Partial reads (with offset/limit) are also routed through lean-ctx using lines:N-M mode for compression.

Slash Command

Use /lean-ctx in Pi to check which binary is being used.

Links

• lean-ctx — The Cognitive Filter for AI Engineering
• GitHub
• Discord