agent_base/engine/
builder.rs

1use std::sync::Arc;
2
3use crate::llm::{ReasoningConfig, StreamClient};
4use crate::tool::{Tool, ToolPolicy, ToolRegistry};
5use crate::types::{
6    AgentConfig, AtomicU64SessionIdGenerator, ConvertToLlmFn, ResponseFormat, RetryConfig,
7    SessionIdGenerator,
8};
9
10use super::AgentRuntime;
11use super::approval::ApprovalHandler;
12use super::context::ContextWindowManager;
13use super::middleware::{Middleware, MiddlewareRef};
14use super::recovery::{StopOnError, ToolErrorRecovery};
15use super::session_store::{InMemorySessionStore, SessionStore};
16
17pub struct AgentBuilder {
18    client: Arc<dyn StreamClient>,
19    config: AgentConfig,
20    tools: ToolRegistry,
21    approval_handler: Option<Arc<dyn ApprovalHandler>>,
22    tool_policy: Option<Arc<dyn ToolPolicy>>,
23    middlewares: Vec<MiddlewareRef>,
24    context_manager: Option<ContextWindowManager>,
25    session_store: Option<Arc<dyn SessionStore>>,
26    error_recovery: Option<Arc<dyn ToolErrorRecovery>>,
27    event_bus_capacity: usize,
28    session_id_generator: Option<Arc<dyn SessionIdGenerator>>,
29    convert_to_llm: Option<ConvertToLlmFn>,
30}
31
32impl AgentBuilder {
33    pub fn new(client: Arc<dyn StreamClient>) -> Self {
34        Self {
35            client,
36            config: AgentConfig::default(),
37            tools: ToolRegistry::default(),
38            approval_handler: None,
39            tool_policy: None,
40            middlewares: Vec::new(),
41            context_manager: None,
42            session_store: None,
43            error_recovery: None,
44            event_bus_capacity: 2048,
45            session_id_generator: None,
46            convert_to_llm: None,
47        }
48    }
49
50    pub fn event_bus_capacity(mut self, capacity: usize) -> Self {
51        self.event_bus_capacity = capacity;
52        self
53    }
54
55    pub fn session_id_generator(mut self, generator: Arc<dyn SessionIdGenerator>) -> Self {
56        self.session_id_generator = Some(generator);
57        self
58    }
59
60    /// Set a callback to transform messages before they are sent to the LLM.
61    ///
62    /// The default behavior (when `None`) is to filter out
63    /// [`ChatMessage::Custom`] variants, which most providers don't understand.
64    /// Override this to inject custom serialization logic for application-specific
65    /// message types.
66    pub fn convert_to_llm(mut self, cb: ConvertToLlmFn) -> Self {
67        self.convert_to_llm = Some(cb);
68        self
69    }
70
71    pub fn system_prompt(mut self, system_prompt: impl Into<String>) -> Self {
72        self.config.system_prompt = Some(system_prompt.into());
73        self
74    }
75
76    /// Set whether to include the reasoning content in LLM responses.
77    ///
78    /// Controls whether the `reasoning_content` field from the LLM is forwarded
79    /// to consumers (i.e., "show the thinking process").
80    /// See [`AgentConfig::enable_thought`] for the distinction from `enable_thinking()`.
81    pub fn enable_thought(mut self, enable: bool) -> Self {
82        self.config.enable_thought = enable;
83        self
84    }
85
86    pub fn reasoning(mut self, config: ReasoningConfig) -> Self {
87        self.config.reasoning = Some(config);
88        self
89    }
90
91    /// Set whether to enable the model's extended thinking / reasoning mode.
92    ///
93    /// Controls whether the model performs deep reasoning (i.e., "enable thinking mode").
94    /// See [`AgentConfig::enable_thought`] for the distinction from `enable_thought()`.
95    pub fn enable_thinking(mut self, enable: bool) -> Self {
96        let mut config = self.config.reasoning.take().unwrap_or_default();
97        config.enabled = Some(enable);
98        self.config.reasoning = Some(config);
99        self
100    }
101
102    pub fn thinking_budget(mut self, budget: u64) -> Self {
103        let mut config = self.config.reasoning.take().unwrap_or_default();
104        config.budget_tokens = Some(budget);
105        self.config.reasoning = Some(config);
106        self
107    }
108
109    pub fn tool_timeout(mut self, timeout_ms: u64) -> Self {
110        self.config.tool.tool_timeout_ms = Some(timeout_ms);
111        self
112    }
113
114    pub fn max_tool_output_chars(mut self, max_chars: usize) -> Self {
115        self.config.tool.max_tool_output_chars = Some(max_chars);
116        self
117    }
118
119    pub fn register_tool(mut self, tool: impl Tool + 'static) -> Self {
120        self.tools.register(tool);
121        self
122    }
123
124    pub fn register_tool_arc(mut self, tool: Arc<dyn Tool>) -> Self {
125        self.tools.register_arc(tool);
126        self
127    }
128
129    pub fn approval_handler(mut self, handler: Arc<dyn ApprovalHandler>) -> Self {
130        self.approval_handler = Some(handler);
131        self
132    }
133
134    pub fn tool_policy(mut self, policy: Arc<dyn ToolPolicy>) -> Self {
135        self.tool_policy = Some(policy);
136        self
137    }
138
139    pub fn middleware(mut self, mw: impl Middleware + 'static) -> Self {
140        self.middlewares.push(Arc::new(mw));
141        self
142    }
143
144    pub fn context_window(mut self, max_tokens: usize) -> Self {
145        self.context_manager = Some(ContextWindowManager::new(max_tokens));
146        self
147    }
148
149    pub fn context_window_manager(mut self, manager: ContextWindowManager) -> Self {
150        self.context_manager = Some(manager);
151        self
152    }
153
154    pub fn response_format(mut self, format: ResponseFormat) -> Self {
155        self.config.llm.response_format = Some(format);
156        self
157    }
158
159    pub fn llm_retry(mut self, retry: RetryConfig) -> Self {
160        self.config.llm.llm_retry = Some(retry);
161        self
162    }
163
164    pub fn session_store(mut self, store: Arc<dyn SessionStore>) -> Self {
165        self.session_store = Some(store);
166        self
167    }
168
169    pub fn error_recovery(mut self, recovery: Arc<dyn ToolErrorRecovery>) -> Self {
170        self.error_recovery = Some(recovery);
171        self
172    }
173
174    pub fn max_sessions(mut self, max: usize) -> Self {
175        self.config.session.max_sessions = Some(max);
176        self
177    }
178
179    pub fn max_turns_per_session(mut self, max: usize) -> Self {
180        self.config.session.max_turns_per_session = Some(max);
181        self
182    }
183
184    /// Cap the number of react-loop iterations allowed for a *single* run (one user
185    /// input). Distinct from [`Self::max_turns_per_session`], which caps turns across
186    /// the whole session. When unset, falls back to `DEFAULT_MAX_TURNS` (50).
187    pub fn execution_max_turns(mut self, max: u32) -> Self {
188        self.config.execution.max_turns = Some(max);
189        self
190    }
191
192    pub fn max_message_tokens(mut self, max: usize) -> Self {
193        self.config.session.max_message_tokens = Some(max);
194        self
195    }
196
197    pub fn tool_error_retry_prompt(mut self, prompt: impl Into<String>) -> Self {
198        self.config.tool.tool_error_retry_prompt = Some(prompt.into());
199        self
200    }
201
202    pub fn language(mut self, language: crate::types::Language) -> Self {
203        self.config.language = language;
204        self
205    }
206
207    /// Conditionally chain a builder call: apply `f` only when `value` is `Some`.
208    ///
209    /// # Example
210    /// ```ignore
211    /// let builder = AgentBuilder::new(client)
212    ///     .apply_if(config.timeout, |b, t| b.tool_timeout(t))
213    ///     .apply_if(config.max_chars, |b, c| b.max_tool_output_chars(c));
214    /// ```
215    pub fn apply_if<T>(self, value: Option<T>, f: impl FnOnce(Self, T) -> Self) -> Self {
216        match value {
217            Some(v) => f(self, v),
218            None => self,
219        }
220    }
221
222    pub fn build(self) -> crate::types::AgentResult<AgentRuntime> {
223        self.config.validate()?;
224
225        tracing::info!(
226            tool_count = self.tools.len(),
227            middleware_count = self.middlewares.len(),
228            has_approval = self.approval_handler.is_some(),
229            has_context_window = self.context_manager.is_some(),
230            "building agent runtime"
231        );
232
233        let event_bus = super::runtime::EventBus::new(self.event_bus_capacity);
234
235        // Inject EventBus into framework-provided tools that need it
236        // (e.g., UpdatePlanTool via FrameworkTool::set_event_bus)
237        self.tools.inject_event_bus(&event_bus);
238
239        let session_store = self
240            .session_store
241            .unwrap_or_else(|| Arc::new(InMemorySessionStore::new()));
242        let error_recovery = self.error_recovery.unwrap_or_else(|| Arc::new(StopOnError));
243        let session_id_generator = self
244            .session_id_generator
245            .unwrap_or_else(|| Arc::new(AtomicU64SessionIdGenerator::default()));
246
247        let session_manager = super::runtime::SessionManager::new(
248            session_id_generator,
249            session_store,
250            self.config.session.clone(),
251        );
252
253        let llm_engine = super::runtime::LlmEngine::new(self.client.clone(), event_bus.clone());
254
255        let tool_engine = super::runtime::ToolEngine::new(
256            self.tools,
257            self.approval_handler,
258            self.tool_policy,
259            error_recovery,
260            event_bus.clone(),
261        );
262
263        let runner = Arc::new(super::runtime::RuntimeCore::new(
264            self.config,
265            llm_engine,
266            tool_engine,
267            session_manager,
268            event_bus,
269            self.context_manager,
270            self.middlewares,
271            self.convert_to_llm,
272        ));
273
274        Ok(AgentRuntime { runner })
275    }
276}
277
278#[cfg(test)]
279mod tests {
280    use super::*;
281    use crate::llm::LlmClient;
282    use crate::llm::StreamChunk;
283    use crate::types::{AgentResult, ChatMessage, ResponseFormat};
284    use async_trait::async_trait;
285    use futures_core::Stream;
286    use serde_json::Value;
287    use std::pin::Pin;
288
289    struct DummyClient;
290
291    #[async_trait]
292    impl LlmClient for DummyClient {
293        async fn chat(
294            &self,
295            _messages: &[ChatMessage],
296            _tools: &[Value],
297            _reasoning: Option<&ReasoningConfig>,
298            _response_format: Option<&ResponseFormat>,
299        ) -> AgentResult<Value> {
300            Ok(Value::Null)
301        }
302
303        async fn chat_stream(
304            &self,
305            _messages: &[ChatMessage],
306            _tools: &[Value],
307            _reasoning: Option<&ReasoningConfig>,
308            _response_format: Option<&ResponseFormat>,
309        ) -> AgentResult<Pin<Box<dyn Stream<Item = AgentResult<StreamChunk>> + Send>>> {
310            unimplemented!("not used in builder tests")
311        }
312
313        fn capabilities(&self) -> crate::llm::LlmCapabilities {
314            crate::llm::LlmCapabilities::default()
315        }
316    }
317
318    #[test]
319    fn execution_max_turns_writes_per_run_config() {
320        let client = crate::llm::adapt(Arc::new(DummyClient));
321        let builder = AgentBuilder::new(client).execution_max_turns(200);
322        // The `config` field is private to this module, so the test can assert directly.
323        assert_eq!(builder.config.execution.max_turns, Some(200));
324    }
325
326    #[test]
327    fn execution_max_turns_defaults_to_none() {
328        let client = crate::llm::adapt(Arc::new(DummyClient));
329        let builder = AgentBuilder::new(client);
330        assert_eq!(builder.config.execution.max_turns, None);
331    }
332}
agent_base/engine/builder.rs

agent_base/engine/
builder.rs
