Fan out codebase work across parallel AI subagents

pi-dynamic-workflows

Claude-Code-style dynamic workflows for Pi.

A Pi extension that adds a workflow tool. Instead of one assistant doing everything sequentially, the model writes a small JavaScript script that fans out the work across many isolated subagents, then synthesizes the results.

Great for codebase audits, multi-perspective review, large refactors, and fan-out research.

Inspired by Anthropic's dynamic workflows in Claude Code.

Install

pi install npm:pi-dynamic-workflows
# or from a local checkout
pi install /path/to/pi-dynamic-workflows

Then in Pi:

/reload

That's it. The extension registers a workflow tool and activates it on session start.

Usage

Just ask Pi for a workflow in plain language:

Run a workflow to inspect this repository and summarize the main modules.

The model will write a workflow script and call the workflow tool. Live progress shows up inline:

◆ Workflow: inspect_project (3/3 done)
  ✓ Scan 1/1
    #1 ✓ repo inventory
  ✓ Analyze 2/2
    #2 ✓ source modules
    #3 ✓ final summary

Press Esc to cancel a running workflow. Active subagents are aborted and surfaced as skipped.

Workflow script shape

A workflow is plain JavaScript. The first statement must export literal metadata. name and description are required; phases is optional documentation for an expected outline. The live progress view is driven by phase(...) calls at runtime:

export const meta = {
  name: 'inspect_project',
  description: 'Inspect a repository and summarize the main modules',
  phases: [
    { title: 'Scan' },
    { title: 'Analyze' },
  ],
}

phase('Scan')
const inventory = await agent('Inspect the repository structure.', {
  label: 'repo inventory',
})

phase('Analyze')
const summary = await agent(
  'Summarize the main modules from this inventory:\n' + inventory,
  { label: 'module summary' },
)

return { inventory, summary }

Phases are discovered as the script runs, so conditional and loop-created phases work naturally. If a branch is skipped, its phase does not show up as an empty progress row.

Editor IntelliSense

Reusable workflow files can opt into editor hints for workflow globals:

/// <reference types="pi-dynamic-workflows/workflow" />

This declares agent, parallel, pipeline, phase, log, args, cwd, and budget for TypeScript-aware editors.

Available globals

Determinism rules

Workflow scripts are evaluated inside a Node vm sandbox. The following are intentionally unavailable:

• Date.now(), new Date()
• Math.random()
• require, import, fs, network APIs
• spreads, computed keys, template interpolation, function calls inside meta

This keeps meta parseable, runs reproducible, and the surface area small.

Structured subagent output

Pass a JSON Schema via opts.schema and the subagent will return a validated object:

const finding = await agent('Find security-sensitive files.', {
  label: 'security scan',
  schema: {
    type: 'object',
    properties: {
      paths: { type: 'array', items: { type: 'string' } },
      reason: { type: 'string' },
    },
    required: ['paths', 'reason'],
  },
})

Under the hood this is a Pi structured_output tool with terminate: true, so the subagent ends on that call without an extra assistant turn.

How it works

user prompt
  → Pi model writes a workflow script
  → workflow tool parses + runs script in a vm sandbox
  → script calls agent(), parallel(), pipeline()
  → each agent() spawns an in-memory Pi subagent session
  → snapshots stream back as compact progress
  → final structured result returned to the parent assistant

Subagents run in fresh in-memory Pi sessions with the standard coding tools, so they can read files, run shell commands, and call structured output exactly like a normal Pi turn.

Library modules

Development

npm install
npm test     # biome check + tsc + unit tests
npm run dev

Parser unit tests live in tests/workflow-parser.test.ts and cover both accepted and rejected script shapes.

Status

This is a prototype. It implements the core workflow primitive (script, subagents, parallel/pipeline, phases, abort, structured output) but does not yet implement persisted or resumable runs, or a /workflows manager.