---
title: "Pi Adapter"
description: "Native Pi runtime adapter — the full governed harness with lifecycle hooks."
---

## Why Pi is the native runtime

Pi is the first supported host because it exposes the hooks RStack needs for a real governed harness:

| RStack need | Pi support |
|---|---|
| Custom SDLC tools | `pi.registerTool()` |
| Slash commands | `pi.registerCommand()` |
| Lifecycle hooks | `pi.on(...)` |
| Safety gates | `tool_call` hook |
| Tool evidence logging | `tool_result` hook |
| Skill/prompt discovery | `resources_discover` hook |
| Installable package | `pi install` |
| Isolated worker delegation | `pi --mode json` subprocesses |

## Installation

```bash
# From npm (after publishing)
pi install npm:rstack-agents

# From local checkout
pi install /path/to/SDLC-rstack

# One-off test without installing
pi -e /path/to/SDLC-rstack/extensions/rstack-sdlc.ts
```

## Hook lifecycle

| Pi hook | RStack behavior |
|---|---|
| `resources_discover` | Exposes package/project skills and prompts to Pi |
| `session_start` | Creates `.rstack/` state roots and sets the RStack status line |
| `before_agent_start` | Injects orchestrator/builder/validator instructions when prompt mentions RStack/SDLC |
| `tool_call` | Logs tool calls; blocks destructive actions without approval |
| `tool_result` | Logs bounded tool result summaries to the active run event stream |
| `session_shutdown` | Appends a shutdown event to the active run |

## Native Pi tools

```text
sdlc_orchestrate   Load orchestrator, builder, validator for a goal
sdlc_start         Create run state directory
sdlc_clarify       Capture product-owner decisions
sdlc_plan          Generate plan, tasks, specs, traceability
sdlc_spec          Read or update spec artifacts
sdlc_approve       Record human approval/rejection gates
sdlc_agents        List available agents, skills, plugins
sdlc_delegate      Spawn isolated Pi worker agents
sdlc_build_next    Prepare the next gated builder task packet
sdlc_validate      Validate builder output; write validation.json
sdlc_status        Show run status and next recommended action
sdlc_memory        Search or append cross-run learnings
```

## Native Pi slash commands

```text
/sdlc              Start or continue an SDLC run
/sdlc-agents       List available agents for the current run
```

## Delegated workers

`sdlc_delegate` spawns isolated Pi workers for bounded tasks. Validators default to read-only tools:

```text
sdlc_delegate(role="validator", task="review auth implementation")
# → Spawns a Pi worker with read, grep, find, ls only
# → Returns validation.json summary
```