# LLM 调用周期控制 — 实施方案

> 参考实现: [HKUDS/OpenHarness](https://github.com/HKUDS/OpenHarness)

## 目标

实现大模型基础调用周期控制，作为 agcore 的核心底层件。

## 范围

- 仅支持 OpenAI-compatible API (`POST /v1/chat/completions`)
- 仅非流式调用（后续可扩展流式）
- 支持传入 tool definitions 和解析 tool_use response，但**不含 tool 自动执行循环**
- 单次请求-响应周期控制

## 领域模块结构

所有 LLM 调用周期相关代码归入 `llm` 领域目录，未来其他功能（工具、记忆、提示词等）以同样方式组织。

```
src/
  lib.rs                # crate 根
  llm.rs                # mod llm — 领域根（声明 + 重导出）
  llm/
    types.rs            # llm::types — Message, ContentBlock, ChatRequest/Response, ToolDefinition
    error.rs            # llm::error — LlmError
    provider.rs         # llm::provider — LlmProvider trait（仅接口）
    provider/
      openai.rs         # llm::provider::openai — OpenaiProvider 实现
    cycle.rs            # llm::cycle — 生命周期引擎（子模块根）
    cycle/
      retry.rs          # llm::cycle::retry — 重试策略
      usage.rs          # llm::cycle::usage — Token 用量

# 未来领域示例（占位）：
# tools.rs + tools/        # 工具调用、MCP
# memory.rs + memory/      # 记忆系统
# prompt.rs + prompt/      # 提示词工程
# agent.rs + agent/        # Agent 运行时
```

`llm.rs` 根模块声明:

```rust
// llm.rs
pub mod types;
pub mod error;
pub mod provider;
pub mod cycle;
```

## 模块设计

### 1. llm/types.rs — 核心数据类型

```rust
pub enum Role { User, Assistant, System, Tool }

pub enum ContentBlock {
    Text { text: String },
    ToolUse { id: String, name: String, input: serde_json::Value },
    ToolResult { tool_use_id: String, content: String, is_error: bool },
}

pub struct Message { pub role: Role, pub content: Vec<ContentBlock> }
pub struct ToolDefinition { pub name: String, pub description: String, pub input_schema: Value }

pub struct ChatRequest {
    pub model: String,
    pub messages: Vec<Message>,
    pub system_prompt: Option<String>,
    pub tools: Vec<ToolDefinition>,
    pub max_tokens: Option<u32>,
    pub temperature: Option<f32>,
}

pub struct ChatResponse {
    pub message: Message,
    pub usage: Usage,
    pub stop_reason: Option<StopReason>,
}

pub enum StopReason { Stop, ToolUse, MaxTokens, ContentFilter, Other(String) }
```

### 2. llm/error.rs — 错误体系

```rust
#[derive(thiserror::Error)]
pub enum LlmError {
    Authentication(String),
    RateLimit { retry_after: Option<Duration> },
    Request { status: u16, body: String },
    Timeout { duration: Duration },
    Stream(String),
    ContextLength { actual: u32, limit: u32 },
}
```

### 3. llm/provider.rs — Provider 接口

trait 单独存放，具体实现在 `provider/` 子模块。

```rust
// llm/provider.rs
pub mod openai;

#[async_trait]
pub trait LlmProvider: Send + Sync {
    async fn chat(&self, request: ChatRequest) -> Result<ChatResponse, LlmError>;
}
```

#### 3.1 llm/provider/openai.rs — OpenAI 兼容实现

```rust
// llm/provider/openai.rs
use super::LlmProvider;

pub struct OpenaiProvider {
    http_client: reqwest::Client,
    base_url: String,
    api_key: String,
    model: String,
}

impl LlmProvider for OpenaiProvider {
    async fn chat(&self, request: ChatRequest) -> Result<ChatResponse, LlmError> {
        // POST {base_url}/chat/completions
        // 解析 response → ChatResponse
        todo!()
    }
}
```

后续新增实现: `provider/anthropic.rs`、`provider/azure.rs` 等。

### 4. llm/cycle.rs — 生命周期引擎

```rust
mod retry;
mod usage;

pub use retry::RetryConfig;
pub use usage::{CostTracker, Usage};

pub struct CycleConfig {
    pub model: String,
    pub max_tokens: Option<u32>,
    pub temperature: Option<f32>,
    pub max_turns: Option<u32>,
    pub retry: RetryConfig,
}

pub struct LlmCycle {
    provider: Box<dyn LlmProvider>,
    config: CycleConfig,
    usage: CostTracker,
    messages: Vec<Message>,
    system_prompt: Option<String>,
}
```

`submit()` 完整流程:

```
submit(prompt, tools)
  │
  ├─ ① push Message(user, [Text(prompt)])
  ├─ ② 构建 ChatRequest { messages, system, tools, max_tokens, temperature }
  ├─ ③ [重试循环] provider.chat(request)
  │     ├─ Ok  → 解析 ChatResponse
  │     └─ Err(可重试) → compute_delay → sleep → retry
  ├─ ④ push Message(assistant, [Text(...) | ToolUse(...)])
  ├─ ⑤ usage.add(response.usage)
  └─ ⑥ return ChatResponse
```

#### 4.1 llm/cycle/retry.rs — 重试策略

```rust
pub struct RetryConfig {
    pub max_retries: u32,        // 默认 3
    pub base_delay: Duration,    // 默认 1s
    pub max_delay: Duration,     // 默认 30s
    pub jitter_factor: f64,      // 默认 0.25
}
```

指数退避 + jitter: `delay = min(base * 2^attempt, max_delay) + random(0, delay * jitter_factor)`

可重试错误: RateLimit, Timeout, 5xx

#### 4.2 llm/cycle/usage.rs — Token 用量

```rust
#[derive(Default)]
pub struct Usage { pub input_tokens: u32, pub output_tokens: u32 }

pub struct CostTracker { accumulated: Usage }
impl CostTracker {
    pub fn add(&mut self, usage: &Usage);
    pub fn total(&self) -> &Usage;
    pub fn reset(&mut self);
}
```

## 依赖

```toml
[dependencies]
tokio = { version = "1", features = ["full"] }
reqwest = { version = "0.12", features = ["json"] }
serde = { version = "1", features = ["derive"] }
serde_json = "1"
thiserror = "2"
async-trait = "0.1"
tracing = "0.1"
```

## 测试

- Unit: types 序列化、retry 退避计算、usage 累计
- Mock: HTTP mock server 测试 provider 请求/响应/错误处理
- Integration (可选): Ollama 本地真实调用验证

## 后续扩展

- 流式接口 (`Stream<CycleEvent>`)
- Tool 自动执行循环 (参考 OpenHarness `run_query()`)
- 多 Provider 注册发现 (参考 OpenHarness `ProviderRegistry`)
- 上下文压缩 (auto-compaction)
- 生命周期钩子 (pre/post tool use hooks)