线程模型
Thread 表示持久化会话。Thread 本身只保存 thread 元信息；消息和 run 历史通过存储 trait 单独管理。
Thread
pub struct Thread {
pub id: String,
pub metadata: ThreadMetadata,
}构造函数
fn new() -> Self
fn with_id(id: impl Into<String>) -> SelfBuilder 方法
fn with_title(self, title: impl Into<String>) -> SelfThreadMetadata
pub struct ThreadMetadata {
pub created_at: Option<u64>,
pub updated_at: Option<u64>,
pub title: Option<String>,
pub custom: HashMap<String, Value>,
}存储
消息不直接嵌在 Thread 里，而是通过 ThreadStore 读写：
#[async_trait]
pub trait ThreadStore: Send + Sync {
async fn load_thread(&self, thread_id: &str) -> Result<Option<Thread>, StorageError>;
async fn save_thread(&self, thread: &Thread) -> Result<(), StorageError>;
async fn delete_thread(&self, thread_id: &str) -> Result<(), StorageError>;
async fn list_threads(&self, offset: usize, limit: usize) -> Result<Vec<String>, StorageError>;
async fn load_messages(&self, thread_id: &str) -> Result<Option<Vec<Message>>, StorageError>;
async fn save_messages(&self, thread_id: &str, messages: &[Message]) -> Result<(), StorageError>;
async fn delete_messages(&self, thread_id: &str) -> Result<(), StorageError>;
async fn update_thread_metadata(&self, id: &str, metadata: ThreadMetadata) -> Result<(), StorageError>;
}ThreadRunStore
ThreadRunStore 在 ThreadStore + RunStore 基础上增加了原子 checkpoint：
#[async_trait]
pub trait ThreadRunStore: ThreadStore + RunStore + Send + Sync {
async fn checkpoint(
&self,
thread_id: &str,
messages: &[Message],
run: &RunRecord,
) -> Result<(), StorageError>;
}RunStore
#[async_trait]
pub trait RunStore: Send + Sync {
async fn create_run(&self, record: &RunRecord) -> Result<(), StorageError>;
async fn load_run(&self, run_id: &str) -> Result<Option<RunRecord>, StorageError>;
async fn latest_run(&self, thread_id: &str) -> Result<Option<RunRecord>, StorageError>;
async fn list_runs(&self, query: &RunQuery) -> Result<RunPage, StorageError>;
}RunRecord
pub struct RunRecord {
pub run_id: String,
pub thread_id: String,
pub agent_id: String,
pub parent_run_id: Option<String>,
pub status: RunStatus,
pub termination_code: Option<String>,
pub created_at: u64,
pub updated_at: u64,
pub steps: usize,
pub input_tokens: u64,
pub output_tokens: u64,
pub state: Option<PersistedState>,
}