pi-agent-bus Monorepo

This monorepo contains the core pi-agent-bus components for building and orchestrating Pi coding agents.

Packages

Package	Description
pi-agent-bus-node	The core library (npm install pi-agent-bus-node). Provides the MessageBus, Agent base class (with invokePiTool), TaskQueue, and LLMProvider. Designed to be isolated and reusable in any Node.js/TypeScript project.
pi-agent-bus (Bridge)	A Pi extension (published as pi-agent-bus to NPM). This is the "Pi Integration Layer" that bridges isolated pi-agent-bus-node agents with the pi global object and pi.tools. It also handles pi-link inbound/outbound message translation. This extension must run in a Pi terminal's context.

Getting Started

Quick Install (For Users)

If you simply want to use the agent bus inside your Pi coding environment, install the extension using the pi CLI:

pi install npm:pi-agent-bus

Note: Once installed, use the /pi-agent-bus tools slash commands to configure the available tools.

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Development (For Contributors)

The steps below are for developing within the monorepo.

1. Clone the Monorepo

git clone https://github.com/kylebrodeur/pi-agent-bus.git
cd pi-agent-bus

2. Install Monorepo Dependencies

This will install dependencies for all packages within the monorepo and set up workspace links.

pnpm install

3. Install the Local Extension

For Pi to discover and load the pi-agent-bus-bridge extension, you need to create a symlink from your Pi's extensions directory to the bridge package within this monorepo.

# Create the extensions directory if it doesn't exist
mkdir -p /path/to/your/project/.pi/extensions/

# Create a symlink to the bridge extension
ln -s $(pwd)/packages/pi-agent-bus-bridge /path/to/your/project/.pi/extensions/pi-agent-bus-bridge

After creating the symlink, restart your Pi terminal for the new extension to be loaded.

4. Configure pi-agent-bus-bridge

The pi-agent-bus-bridge extension reads its configuration from a config.json file placed next to its index.ts. This configuration defines which pi.tools are exposed to agents and how pi-link messages are mapped to MessageBus events.

Quick Start (Interactive Configuration)

Upon initial setup, no tools will be exposed to agents. You can interactively configure tools using Pi slash commands:

# List current tools
/pi-agent-bus tools list

# Add essential tools
/pi-agent-bus tools default

# Or add tools individually
/pi-agent-bus tools add append_ledger
/pi-agent-bus tools add query_ledger

# Review and adjust
/pi-agent-bus tools list

# Remove tools if needed
/pi-agent-bus tools remove read

# Reset to secure defaults
/pi-agent-bus tools secure

Note: If no config.json is present, the bridge will initialize with an empty tool list, requiring you to add tools interactively or create a configuration file manually.

Manual Configuration (Advanced)

For more control, you can manually configure the bridge by creating a packages/pi-agent-bus-bridge/config.json file with your desired settings.

Sample configurations are available:

• config.essential.json — Recommended starting point with essential tools
• config.secure.json — Minimal secure configuration with most restrictive access

Create packages/pi-agent-bus-bridge/config.json:

{
  "exposedPiTools": [
    "append_ledger", "query_ledger", "describe_ledger", "ledger_stats",
    "route_model",
    "context_tag", "context_log", "context_checksum",
    "link_send", "link_prompt", "link_list",
    "op_get_secret", "op_load_env",
    "read", "bash", "write", "edit", "ls", "grep", "find"
  ],
  "piLinkEventMappings": [
    {
      "slashCommand": "/start-agent-workflow",
      "busTopic": "orchestration_commands",
      "description": "Starts a complex agent workflow by sending command to MessageBus.",
      "payloadMap": {
        "args.0": "workflowId",
        "args.1": "context"
      }
    },
    {
      "slashCommand": "/agent-message",
      "busTopic": "agent_messages_from_user",
      "description": "Sends a direct message from the user to the MessageBus for agents.",
      "payloadMap": {
        "args.0": "message"
      }
    }
  ],
  "busToPiLinkMappings": [
    {
      "busTopic": "agent_workflow_updates",
      "messageBuilder": "Agent Workflow Update [${payload.workflowId}]: ${payload.status}"
    },
    {
      "busTopic": "agent_alert_critical",
      "piLinkTarget": "*",
      "messageBuilder": "CRITICAL AGENT ALERT from ${payload.agentId}: ${payload.message}"
    }
  ]
}

Explanation of Configuration Fields:

• exposedPiTools: A whitelist of tool names that agents are allowed to request via the pi_tool_bridge_requests topic. The bridge controls access, but the actual execution depends on the tool type:

  • Built-in SDK tools (read, bash, write, edit, find, grep, ls): The bridge executes these programmatically (no user interaction required) using createReadTool, createBashTool, etc. and returns the result directly to the agent.

  • Extension tools (append_ledger, link_send, context_tag, op_get_secret, route_model, etc.): Pi's ExtensionAPI does not expose a way for extensions to call another extension's tools programmatically. When an agent requests one of these, the bridge queues a user message (pi.sendUserMessage('/tool_name ...')) so the Pi agent can execute it on the agent's behalf. This means extension tools cannot be called fire-and-forget — they require the Pi agent to be idle and trigger a new turn.

  This distinction is important for designing agent workflows. Data-processing agents should prefer built-in tools; coordination agents should account for the queuing latency of extension tools.

• piLinkEventMappings: Defines Pi slash commands that, when executed, trigger an event on the MessageBus.

  • slashCommand: The Pi command (e.g., /start-agent-workflow).
  • busTopic: The MessageBus topic where the event is published.
  • description: Appears in Pi's help system (/help).
  • payloadMap: (Optional) Maps arguments from the slash command into the payload of the MessageBus event. args.0 refers to the first argument, args.1 the second, etc.

• busToPiLinkMappings: Defines MessageBus topics that, when a message is published to them, trigger a pi-link message to another terminal.

  • busTopic: The MessageBus topic to monitor.
  • piLinkTarget: (Optional) The target terminal (* for broadcast, or a specific terminal ID).
  • messageBuilder: (Optional) A template string or function to build the pi-link message from the MessageBus payload. Uses basic template literal syntax ${payload.field}.

Development

Progressive Enhancement Configs

The bridge supports starting empty and adding tools as you install extensions:

Config File	Tools Exposed	Required Extensions
config.json	None	None (safe to load with no extensions)
config.ledger-only.json	Ledger CRUD	pi-qmd-ledger
config.with-link.json	Ledger + pi-link	pi-qmd-ledger, pi-link
config.with-model-router.json	Ledger + link + routing	pi-qmd-ledger, pi-link, pi-model-router
config.with-context.json	Ledger + link + routing + context	Above + pi-context
config.essential.json	Full ecosystem	All core Pi extensions
config.secure.json	Minimal safe set	Any subset

Copy the appropriate preset to config.json:

cp packages/pi-agent-bus-bridge/config.with-link.json packages/pi-agent-bus-bridge/config.json

Or use the slash commands after installation:

/pi-agent-bus tools discover    # See what's available
/pi-agent-bus tools default   # Load essential preset
/pi-agent-bus tools add append_ledger

pi-subagents Migration

pi-agent-bus replaces the archived pi-subagents package. Key differences:

• Pub/sub instead of spawning: MessageBus topics replace subagent() process creation
• Configurable security: exposedPiTools whitelist instead of all-or-nothing skill injection
• Persistent history: Message history with configurable limits replaces ephemeral agents
• Task ownership: TaskQueue.claim/complete replaces unmanaged concurrent execution

See TODO.md for the full feature comparison and migration guide.ing Packages

pnpm build # Builds all packages in the monorepo

Testing

pnpm test # Runs tests for all packages in the monorepo

Contributing

Contributions are welcome! Please see the individual package README.md files for more details.

License

This monorepo is released under the MIT License.