读懂 Pi（原 pi-mono）源码

// 消费 EventStream，实时渲染到终端
for await (const event of agentLoop(config)) {
  switch (event.type) {
    case 'message_update':
      tui.appendText(event.delta)
      break
    case 'tool_execution_start':
      tui.showSpinner(`Running ${event.toolCall.name}...`)
      break
    case 'tool_execution_end':
      tui.hideSpinner()
      tui.showResult(event.result)
      break
  }
}

// 两个入口，返回同一种 EventStream
export async function* agentLoop(config: AgentConfig): AsyncGenerator<AgentEvent> {
  yield { type: 'agent_start' }

  const messages: Message[] = [
    { role: 'system', content: config.systemPrompt }
  ]

  // 外层循环：处理多轮用户输入
  while (true) {
    const userMessage = await config.getNextMessage()
    if (!userMessage) break

    messages.push({ role: 'user', content: userMessage })
    yield { type: 'turn_start' }

    // 内层循环：处理工具调用链
    while (true) {
      const response = await config.llm.chat(messages, { tools: config.tools })
      messages.push(response)

      yield { type: 'message_end', content: response }

      if (!response.toolCalls?.length) break

      // 并行执行所有工具
      const results = await Promise.all(
        response.toolCalls.map(async (tc) => {
          yield { type: 'tool_execution_start', toolCall: tc }
          const result = await executeToolCall(tc, config)
          yield { type: 'tool_execution_end', result }
          return result
        })
      )

      // 工具结果追加到 messages
      messages.push(...results.map(r => ({ role: 'tool', ...r })))
    }

    yield { type: 'turn_end' }
  }

  yield { type: 'agent_end' }
}

export async function* agentLoopContinue(
  config: AgentConfig,
  transcript: AgentEvent[]
): AsyncGenerator<AgentEvent> {
  // 从 transcript 重建 messages 状态
  const messages = rebuildMessagesFromTranscript(transcript)

  // 然后进入和 agentLoop 一样的循环
  // ...（同上）
}

// packages/ai/src/unified-api.ts
export interface LlmProvider {
  chat(request: ChatRequest): Promise<ChatResponse>
  stream(request: ChatRequest): AsyncGenerator<ChatChunk>
  countTokens(text: string): number
}

export interface ChatRequest {
  messages: Message[]
  tools?: ToolDefinition[]
  maxTokens?: number
  temperature?: number
}

export interface ChatResponse {
  role: 'assistant'
  content: string
  toolCalls?: ToolCall[]
  usage: { inputTokens: number; outputTokens: number }
}

// 按配置选择 Provider
export function createProvider(config: ProviderConfig): LlmProvider {
  switch (config.provider) {
    case 'openai': return new OpenAIProvider(config)
    case 'anthropic': return new AnthropicProvider(config)
    case 'google': return new GoogleProvider(config)
    case 'bedrock': return new BedrockProvider(config)
  }
}

// AsyncGenerator 的优势：背压控制
for await (const event of agentLoop(config)) {
  // 消费者慢了，生产者自动暂停
  await slowRender(event)
}

// 不是 readFile 整个文件
const content = await readTool.execute({
  path: 'src/main.ts',
  offset: 50,   // 从第 50 行开始
  limit: 30     // 只读 30 行
})

function truncateToolResult(result: string, maxChars: number = 10000): string {
  if (result.length <= maxChars) return result
  const half = maxChars / 2
  return `${result.slice(0, half)}\n\n[... ${result.length - maxChars} chars omitted ...]\n\n${result.slice(-half)}`
}

// 用户可以选择性分享 session transcript
sessionSharing:
  enabled: false           // 默认关闭
  anonymize: true          // 开启时自动脱敏
  excludeTools: ['Bash']   // 排除 shell 命令（可能含敏感信息）