co-mono/packages/agent

@mariozechner/pi-agent-core

Stateful agent abstraction with transport layer for LLM interactions. Provides a reactive Agent class that manages conversation state, emits granular events, and supports pluggable transports for different deployment scenarios.

Installation

npm install @mariozechner/pi-agent-core

Quick Start

import { Agent, ProviderTransport } from '@mariozechner/pi-agent-core';
import { getModel } from '@mariozechner/pi-ai';

// Create agent with direct provider transport
const agent = new Agent({
  transport: new ProviderTransport(),
  initialState: {
    systemPrompt: 'You are a helpful assistant.',
    model: getModel('anthropic', 'claude-sonnet-4-20250514'),
    thinkingLevel: 'medium',
    tools: []
  }
});

// Subscribe to events for reactive UI updates
agent.subscribe((event) => {
  switch (event.type) {
    case 'message_update':
      // Stream text to UI
      const content = event.message.content;
      for (const block of content) {
        if (block.type === 'text') console.log(block.text);
      }
      break;
    case 'tool_execution_start':
      console.log(`Calling ${event.toolName}...`);
      break;
    case 'tool_execution_update':
      // Stream tool output (e.g., bash stdout)
      console.log('Progress:', event.partialResult.content);
      break;
    case 'tool_execution_end':
      console.log(`Result:`, event.result.content);
      break;
  }
});

// Send a prompt
await agent.prompt('Hello, world!');

// Access conversation state
console.log(agent.state.messages);

Core Concepts

Agent State

The Agent maintains reactive state:

interface AgentState {
  systemPrompt: string;
  model: Model<any>;
  thinkingLevel: ThinkingLevel;  // 'off' | 'minimal' | 'low' | 'medium' | 'high' | 'xhigh'
  tools: AgentTool<any>[];
  messages: AppMessage[];
  isStreaming: boolean;
  streamMessage: Message | null;
  pendingToolCalls: Set<string>;
  error?: string;
}

Events

Events provide fine-grained lifecycle information:

Event	Description
agent_start	Agent begins processing
agent_end	Agent completes, contains all generated messages
turn_start	New turn begins (one LLM response + tool executions)
turn_end	Turn completes with assistant message and tool results
message_start	Message begins (user, assistant, or toolResult)
message_update	Assistant message streaming update
message_end	Message completes
tool_execution_start	Tool begins execution
tool_execution_update	Tool streams progress (e.g., bash output)
tool_execution_end	Tool completes with result

Transports

Transports abstract LLM communication:

• ProviderTransport: Direct API calls using @mariozechner/pi-ai
• AppTransport: Proxy through a backend server (for browser apps)

// Direct provider access (Node.js)
const agent = new Agent({
  transport: new ProviderTransport({
    apiKey: process.env.ANTHROPIC_API_KEY
  })
});

// Via proxy (browser)
const agent = new Agent({
  transport: new AppTransport({
    endpoint: '/api/agent',
    headers: { 'Authorization': 'Bearer ...' }
  })
});

Message Queue

Queue messages to inject at the next turn:

// Queue mode: 'all' or 'one-at-a-time'
agent.setQueueMode('one-at-a-time');

// Queue a message while agent is streaming
await agent.queueMessage({
  role: 'user',
  content: 'Additional context...',
  timestamp: Date.now()
});

Attachments

User messages can include attachments:

await agent.prompt('What is in this image?', [{
  id: 'img1',
  type: 'image',
  fileName: 'photo.jpg',
  mimeType: 'image/jpeg',
  size: 102400,
  content: base64ImageData
}]);

Custom Message Types

Extend AppMessage for app-specific messages via declaration merging:

declare module '@mariozechner/pi-agent-core' {
  interface CustomMessages {
    artifact: { role: 'artifact'; code: string; language: string };
  }
}

// Now AppMessage includes your custom type
const msg: AppMessage = { role: 'artifact', code: '...', language: 'typescript' };

API Reference

Agent Methods

Method	Description
prompt(text, attachments?)	Send a user prompt
continue()	Continue from current context (for retry after overflow)
abort()	Abort current operation
waitForIdle()	Returns promise that resolves when agent is idle
reset()	Clear all messages and state
subscribe(fn)	Subscribe to events, returns unsubscribe function
queueMessage(msg)	Queue message for next turn
clearMessageQueue()	Clear queued messages

State Mutators

Method	Description
setSystemPrompt(v)	Update system prompt
setModel(m)	Switch model
setThinkingLevel(l)	Set reasoning level
setQueueMode(m)	Set queue mode ('all' or 'one-at-a-time')
setTools(t)	Update available tools
replaceMessages(ms)	Replace all messages
appendMessage(m)	Append a message
clearMessages()	Clear all messages

License

MIT