RTK
Why. Intercepts every bash tool call and pipes the command through rtk rewrite — a Rust CLI that strips noise, groups output, deduplicates, and truncates. 60-90% token savings on common dev commands (git, cargo, ls, grep, test runners, linters, docker, kubectl). Sub-10ms overhead per rewrite.
How it works. Hooks tool_call: narrows to bash events, calls pi.exec("rtk", ["rewrite", cmd]), mutates event.input.command in-place if a rewrite exists. RTK binary decides which commands to rewrite and how — all logic lives in the Rust binary, not the extension. Fail-open on errors (never blocks execution). Version guard at load time (requires rtk >= 0.23.0). Respects RTK_DISABLED=1 env var.
Location: .pi/extensions/rtk/
Installation
Binary
curl -fsSL https://raw.githubusercontent.com/rtk-ai/rtk/refs/heads/master/install.sh | sh
Installs to ~/.local/bin/rtk. Verify: rtk --version (expect >= 0.23.0).
Extension
The extension lives project-local at .pi/extensions/rtk/index.ts. Pi loads it automatically when the project is trusted. No --extension flag or config needed.
Docker (container setup)
Add one line to the Dockerfile:
RUN curl -fsSL https://raw.githubusercontent.com/rtk-ai/rtk/refs/heads/master/install.sh | sh
The .pi/extensions/rtk/index.ts is already in the project — mounted into the container automatically.
Details
Architecture
bash "git status"
→ tool_call event
→ RTK: pi.exec("rtk", ["rewrite", "git status"])
→ rtk binary: "rtk git status" (or pass-through if no rewrite)
→ event.input.command = "rtk git status"
→ execution
What gets rewritten
RTK’s rewrite registry covers the most token-heavy commands. The registry is defined in the upstream Rust crate (src/discover/registry.rs) — add new rules there, not in the extension.
Common rewrites:
git status→rtk git status(groups files by status, hides unchanged)git diff→rtk git diff(hides unchanged hunks, shows only changed)git log→rtk git log(compact format, one line per commit)cargo build→rtk cargo build(hides “Compiling” lines, shows only warnings+errors)cargo test→rtk cargo test(hides passing tests, shows only failures)npm test→rtk npm test(hides passing, shows failures)docker ps→rtk docker ps(compact table)kubectl get pods→rtk kubectl get pods(compact table)ps aux→rtk ps aux(hides kernel threads)lsof -i→rtk lsof -i(compact columns)ls -la→rtk ls -la(hides./.., compact timestamps)
See rtk-ai/rtk#command-registry for full list.
Fail-open behavior
| Scenario | Behavior |
|---|---|
| rtk binary not in PATH | Console warning at load time, extension disabled |
| rtk < 0.23.0 | Console warning at load time, extension disabled |
rtk rewrite returns error |
Pass-through — original command unchanged |
rtk rewrite times out |
Pass-through (2s timeout) |
| Extension throws | Pass-through, console warning |
RTK_DISABLED=1 set |
Extension loaded but skips all rewrites |
Command starts with rtk |
Skipped — prevents recursion |
No conflict with other extensions
RTK only touches tool_call → bash → event.input.command. Extensions that also register tool_call:
| Extension | Interaction |
|---|---|
| worktree-sandbox | Prepends cd /sandbox && after RTK rewrite — safe order: RTK first, sandbox wraps |
| agent-harness | Validates tool calls, blocks grep/rg/cat/head/tail — RTK-rewritten commands (prefix rtk) bypass the filter |
| piignore | Only checks read/write, ignores bash |
| session-logger | Read-only observer |
Analytics
rtk gain --history
Shows per-command token savings. Data stored in ~/.local/share/rtk/. Reset with rtk gain --reset.
Updating the extension
The extension file is a one-time copy from RTK upstream. Check for changes:
curl -fsSL https://raw.githubusercontent.com/rtk-ai/rtk/develop/hooks/pi/rtk.ts \
| diff - .pi/extensions/rtk/index.ts
Overwrite if changed:
curl -fsSL -o .pi/extensions/rtk/index.ts \
https://raw.githubusercontent.com/rtk-ai/rtk/develop/hooks/pi/rtk.ts
The binary is updated independently — new rewrite rules land in the Rust binary, not the extension.