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# pi-turn-limit
Pi coding agent extension to limit the number of turns taken by a model in a session.
## Why
Pi agents can run indefinitely, consuming tokens and time, and taking focus. This extension gives you a circuit breaker: when the agent reaches a configurable turn limit, you decide whether to continue or abort.
This is useful for:
- **Interaction** — Shorter _Time To Next Interaction (TTNI)_ keeps you in the loop. Focus, clarity, single-tasking mode.
- **Cost control** — prevent runaway sessions from burning through API credits
- **Quality control** — if an agent needs more turns than expected, something may be wrong with the prompt or task
## How it works
The extension tracks turns (agent round-trips) per session. Each new user prompt resets the counter.
| Event | Behavior |
|-----------------------|---------------------------------------------------|
| `agent_start` | Counter resets to 0 |
| `turn_start` | Counter increments; widget updates |
| Counter reaches limit | User prompted: continue (counter resets) or abort |
| No UI available | Silent abort at limit |
When the limit is reached and the user confirms continuation, the counter resets to 0, allowing another round of turns. This repeats — there's no maximum number of continuations.
## Configuration
### Environment variable
Set `PI_MAX_TURNS` before starting pi:
```bash
# 50 turns
PI_MAX_TURNS=50 pi
# Unlimited — no boundary check fires
PI_MAX_TURNS=unlimited pi
# Default (25 turns)
pi
```
### Runtime command
Adjust the limit during a session with the `turn-limit` command:
```
/turn-limit 50 # Set to 50 turns
/turn-limit unlimited # Disable the limit
/turn-limit 25 # Re-enable with 25 turns (counter resets from 0)
```
### Unlimited mode
Setting the limit to `unlimited` disables the boundary check entirely. The turn counter still increments and the widget still displays `∞`, so you retain observability without enforcement.
Switching from unlimited back to a number triggers the **LimitReEnabled** rule: the counter resets to 0 so the new limit applies from a clean starting point.
## Widget
When a UI is available, the extension displays a widget showing `Turns: N/M` (or `Turns: N/∞` in unlimited mode).
## Spec
This extension was developed using [Allium](https://juxt.github.io/allium/), a formal language for specifying software behavior. The Allium spec captures the turn counting, limit enforcement, unlimited mode, and re-enable rules:
📄 [turn-limit.allium](./turn-limit.allium)
## Contributing
This is an experimental extension. To contribute:
1. Fork the repository
2. Make your changes
3. Contact Willem through [qwan.co.uk](https://qwan.co.uk) to discuss your contribution
## License
MIT