Weasley Subagents is an open-source Pi extension for coordinating specialized child agents. It supports foreground and background delegation, parallel review, sequential chains, saved workflows, bounded execution, worktree isolation, lifecycle artifacts, and a terminal fleet view.

Why use it?

• Keep the parent agent focused while specialists investigate, implement, or review.
• Run independent reviewers concurrently and combine their findings.
• Chain agents with explicit handoffs and output contracts.
• Track long-running work through stable JSON lifecycle artifacts.
• Enforce tool, model, turn, usage, and concurrency boundaries.
• Keep orchestration local by default; session sharing is always explicit.

Requirements

• Node.js 22.19 or newer
• Pi from @earendil-works/pi-coding-agent
• Access to at least one model configured in Pi

Install

Use Pi's package manager:

pi install npm:weasley-subagents

Or use the package CLI. The CLI asks Pi to install the exact npm version that invoked it, so installation never follows an unpinned Git branch:

npx weasley-subagents

Project-local installation:

npx weasley-subagents --project

Remove the managed package while preserving user configuration and run artifacts:

npx weasley-subagents --remove

The removal command delegates to pi remove; it does not recursively delete extension directories.

Start delegating

Ask Pi naturally:

Use scout to map the authentication flow, then ask planner for a safe change plan.

Run three reviewers in parallel: correctness, tests, and unnecessary complexity.

Have worker implement the approved plan, then ask reviewer to inspect the diff.

The extension also exposes a structured subagent tool for precise automation:

subagent({ agent: "reviewer", task: "Review the current diff for correctness." })

subagent({
  tasks: [
    { agent: "reviewer", task: "Check correctness." },
    { agent: "reviewer", task: "Check test coverage." }
  ],
  concurrency: 2
})

subagent({
  chain: [
    { agent: "scout", task: "Map the data flow." },
    { agent: "planner", task: "Use {previous} to produce an implementation plan." }
  ]
})

For background work, pass async: true. Inspect it with subagent({ action: "status" }) or wait for completion with subagent_wait when the current turn requires the result.

Built-in roles

| Role | Purpose | | --- | --- | | scout | Fast codebase reconnaissance and risk mapping | | researcher | Source-backed documentation and web research | | planner | Concrete implementation planning without edits | | worker | Scoped implementation and validation | | reviewer | Diff review, tests, edge cases, and small fixes | | context-builder | Deeper context assembly for complex work | | oracle | Read-only second opinion and assumption challenge | | delegate | Lightweight general delegation |

Agents can be defined at package, user, or project scope. Project definitions can live in .pi/agents/; user definitions can live in ~/.pi/agent/agents/.

Configuration

Primary settings live in Pi's user or project settings under subagents. Extension runtime controls live here:

~/.pi/agent/extensions/weasley-subagents/config.json

Example:

{
  "asyncByDefault": false,
  "fleetView": true,
  "fleetViewPlacement": "belowEditor",
  "maxSubagentDepth": 1,
  "globalConcurrencyLimit": 4,
  "artifactDir": "project",
  "parallel": {
    "maxTasks": 8,
    "concurrency": 4
  },
  "scheduledRuns": {
    "enabled": false
  }
}

Older ~/.pi/agent/extensions/subagent/config.json files are read as a migration fallback. The next configuration update is written to the Weasley path; the legacy file is never deleted automatically.

Common settings include:

• defaultModel, defaultThinking, and agentOverrides
• modelScope for provider/model allowlists
• watchdog for opt-in adversarial review
• turnBudget, toolBudget, and usageBudget
• parallel, chain, and globalConcurrencyLimit
• artifactDir, fleetView, and fleetViewPlacement
• intercomBridge for parent/child coordination

Invalid safety-critical limits fail closed instead of silently becoming unbounded.

Writer budget guidance

As a conservative orchestration policy, do not pass turnBudget, a hard toolBudget, or a tight usageBudget to mutation-capable workers. The default tool budget blocks read/search tools rather than mutation tools, so a hard cap can interrupt the evidence-gathering needed to finish safely. Ask a writer to checkpoint after the current tool returns and report changed files, build/test state, and commit or PR state. An elapsed timeout is not a mutation-safe boundary.

When a hard turn limit is reached during a tool-using turn, termination occurs at the next assistant boundary. The lifecycle state reports termination-deferred until that safe boundary is reached.

Session sharing

Sharing is off unless a tool call explicitly passes share: true. That action exports the child session to HTML and creates a secret GitHub Gist through an authenticated gh CLI. Without additional configuration, the returned link is the Gist URL itself.

An optional viewer is supported only through an explicit HTTPS template:

export WEASLEY_SUBAGENTS_SHARE_VIEWER_URL='https://viewer.example/session/{gistId}'

The template must contain {gistId}, use HTTPS, and contain no embedded credentials. No third-party viewer endpoint is hardcoded.

Artifacts and observability

Project-scoped runs write under .weasley-subagents/ by default. Async runs expose stable lifecycle files such as:

• status.json — current state and step summaries
• events.jsonl — append-only lifecycle events
• output-<index>.log — bounded child output
• subagent-log-<runId>.md — human-readable run summary

Treat these files as local operational data. They are ignored by this repository and should not be committed unless deliberately sanitized.

Safety model

• Child agents do not automatically become orchestrators.
• Tool and extension access can be narrowed per agent.
• Worktree mode isolates parallel writers and records their diffs.
• Completion and acceptance guards distinguish attempted work from verified work.
• Spawn, depth, concurrency, turn, tool, and usage budgets can constrain runs.
• Scheduled execution is disabled by default.
• Sharing requires an explicit per-run request.

Subagents still execute model-generated actions. Review requested permissions, keep credentials out of prompts and repositories, and use the narrowest useful tool set.

Public APIs

The package exports:

import weasleySubagents from "weasley-subagents";
import { registerBackgroundWorkProvider } from "weasley-subagents/background-work";
import { registerSubagentCapabilityCeiling } from "weasley-subagents/capability-ceiling";

It also exposes delegation and preflight APIs for integrations that need programmatic orchestration and launch validation.

Development

npm ci
npm test
npm run test:integration
npm run test:e2e
npm run typecheck
npm run pack:check

Before opening a pull request, run the smallest relevant test first, then npm run test:all and npm run typecheck.

Community

• Read CONTRIBUTING.md before proposing changes.
• Report vulnerabilities privately using SECURITY.md.
• Participate under the Code of Conduct.
• Use GitHub issues for reproducible bugs and scoped feature requests.

License

Copyright 2026 Weasley Open Source.

Licensed under the Apache License 2.0. See NOTICE for attribution information.