diff --git a/src/gateway/agent_factory.rs b/src/gateway/agent_factory.rs
index 43922fe..c14e7aa 100644
--- a/src/gateway/agent_factory.rs
+++ b/src/gateway/agent_factory.rs
@@ -15,6 +15,8 @@ pub(crate) struct AgentFactory {
     skills: Arc<SkillRuntime>,
     reinject_every: usize,
     prompt_repository: Arc<dyn PromptInjectionRepository>,
+    /// 实例创建时间戳（用于区分新旧 AgentFactory 实例）
+    instance_id: u64,
 }
 
 pub(crate) struct AgentBuildRequest<'a> {
@@ -37,17 +39,36 @@ impl AgentFactory {
         reinject_every: usize,
         prompt_repository: Arc<dyn PromptInjectionRepository>,
     ) -> Self {
+        // 使用 Arc 指针地址作为实例标识符，用于区分新旧 AgentFactory 实例
+        let instance_id = Arc::as_ptr(&tools) as u64;
+        tracing::info!(
+            instance_id = instance_id,
+            tool_count = tools.tool_names().len(),
+            "AgentFactory::new created"
+        );
         Self {
             tools,
             skills,
             reinject_every,
             prompt_repository,
+            instance_id,
         }
     }
 
     pub(crate) fn create(&self, request: AgentBuildRequest<'_>) -> Result<AgentLoop, AgentError> {
         let session_id = persistent_session_id(request.channel_name, request.session_chat_id);
 
+        // 诊断日志：记录 agent 实际使用的配置和实例 ID
+        tracing::info!(
+            instance_id = self.instance_id,
+            channel = %request.channel_name,
+            session_id = %session_id,
+            provider = %request.provider_config.name,
+            model_id = %request.provider_config.model_id,
+            tool_count = self.tools.tool_names().len(),
+            "AgentFactory: creating agent with config"
+        );
+
         // 创建组合的系统提示词提供者
         let system_prompt_provider = Arc::new(CompositeSystemPromptProvider::new(vec![
             Box::new(AgentPromptProvider::new(
diff --git a/src/gateway/agent_prompt_provider.rs b/src/gateway/agent_prompt_provider.rs
index e825904..3aee796 100644
--- a/src/gateway/agent_prompt_provider.rs
+++ b/src/gateway/agent_prompt_provider.rs
@@ -55,6 +55,15 @@ impl SystemPromptProvider for AgentPromptProvider {
             return None;
         }
 
+        // 诊断日志：记录系统提示词实际使用的模型配置（用于排查"配置不生效"问题）
+        tracing::info!(
+            session_id = ?context.session_id,
+            chat_id = %context.chat_id,
+            provider = %self.provider_config.name,
+            model_id = %self.provider_config.model_id,
+            "AgentPromptProvider: building system prompt with model config"
+        );
+
         // 加载 Agent 提示词（AGENT.md + builtin + MEMORY_SUMMARY.md）
         let agent_prompt = load_agent_prompt().ok().flatten()?;
 
diff --git a/src/gateway/mod.rs b/src/gateway/mod.rs
index b127707..f8ab7d5 100644
--- a/src/gateway/mod.rs
+++ b/src/gateway/mod.rs
@@ -104,6 +104,12 @@ impl GatewayState {
             Some(bus.clone()),
         )?;
 
+        // 诊断日志：记录新 GatewayState 的创建（用于排查重启后是否使用了新状态）
+        tracing::info!(
+            mcp_manager_present = mcp_manager.is_some(),
+            "GatewayState::from_config: new GatewayState created"
+        );
+
         let cancel_manager = CancelManager::new();
 
         Ok(Self {
diff --git a/src/gateway/runtime.rs b/src/gateway/runtime.rs
index cbd3638..e609267 100644
--- a/src/gateway/runtime.rs
+++ b/src/gateway/runtime.rs
@@ -224,6 +224,15 @@ pub(crate) fn build_session_manager_with_sender(
     // Build base tools
     let tools = factory.build();
 
+    // 诊断日志：记录 MCP 初始化状态和基础工具数量
+    tracing::info!(
+        mcp_enabled = mcp_initializer.is_enabled(),
+        mcp_tools_collected = mcp_tools_for_subagents.len(),
+        base_tool_count = tools.tool_names().len(),
+        base_tools = ?tools.tool_names(),
+        "build_session_manager: base tools built (before MCP registration)"
+    );
+
     // Register MCP tools to main agent (async)
     // Note: MCP tools for subagents are already collected above
     if mcp_initializer.is_enabled() {
@@ -240,6 +249,13 @@ pub(crate) fn build_session_manager_with_sender(
 
     let tools = Arc::new(tools);
 
+    // 诊断日志：记录最终工具数量（含 MCP 工具，如果启用）
+    tracing::info!(
+        final_tool_count = tools.tool_names().len(),
+        final_tools = ?tools.tool_names(),
+        "build_session_manager: final tools registered to main agent"
+    );
+
     let prompt_repository: Arc<dyn PromptInjectionRepository> = store.clone();
     let agent_factory = AgentFactory::new(
         tools.clone(),