feat: Add lead-worker model selection and real-time model display in GUI (#2964)

Co-authored-by: jack <jack@deck.local>

crates/goose-cli/src/commands/web.rs

@@ -589,6 +589,10 @@ async fn process_message_streaming(
                         // For now, we'll just log them
                         tracing::info!("Received MCP notification in web interface");
                     }
+                    Ok(AgentEvent::ModelChange { model, mode }) => {
+                        // Log model change
+                        tracing::info!("Model changed to {} in {} mode", model, mode);
+                    }
                     Err(e) => {
                         error!("Error in message stream: {}", e);
                         let mut sender = sender.lock().await;

crates/goose-cli/src/session/mod.rs

@@ -928,6 +928,12 @@ impl Session {
                                 }
                             }
                         }
+                        Some(Ok(AgentEvent::ModelChange { model, mode })) => {
+                            // Log model change if in debug mode
+                            if self.debug {
+                                eprintln!("Model changed to {} in {} mode", model, mode);
+                            }
+                        }
                         Some(Err(e)) => {
                             eprintln!("Error: {}", e);
                             drop(stream);

crates/goose-ffi/src/lib.rs

@@ -266,6 +266,9 @@ pub unsafe extern "C" fn goose_agent_send_message(
                 Ok(AgentEvent::McpNotification(_)) => {
                     // TODO: Handle MCP notifications.
                 }
+                Ok(AgentEvent::ModelChange { .. }) => {
+                    // Model change events are informational, just continue
+                }
                 Err(e) => {
                     full_response.push_str(&format!("\nError in message stream: {}", e));
                 }

crates/goose-scheduler-executor/src/main.rs

@@ -165,6 +165,9 @@ async fn execute_recipe(job_id: &str, recipe_path: &str) -> Result<String> {
             Ok(AgentEvent::McpNotification(_)) => {
                 // Handle notifications if needed
             }
+            Ok(AgentEvent::ModelChange { .. }) => {
+                // Model change events are informational, just continue
+            }
             Err(e) => {
                 return Err(anyhow!("Error receiving message from agent: {}", e));
             }

crates/goose-server/src/routes/config_management.rs

@@ -441,6 +441,26 @@ pub async fn backup_config(
     }
 }
 
+#[utoipa::path(
+    get,
+    path = "/config/current-model",
+    responses(
+        (status = 200, description = "Current model retrieved successfully", body = String),
+    )
+)]
+pub async fn get_current_model(
+    State(state): State<Arc<AppState>>,
+    headers: HeaderMap,
+) -> Result<Json<Value>, StatusCode> {
+    verify_secret_key(&headers, &state)?;
+
+    let current_model = goose::providers::base::get_current_model();
+
+    Ok(Json(serde_json::json!({
+        "model": current_model
+    })))
+}
+
 pub fn routes(state: Arc<AppState>) -> Router {
     Router::new()
         .route("/config", get(read_all_config))
@@ -454,6 +474,7 @@ pub fn routes(state: Arc<AppState>) -> Router {
         .route("/config/init", post(init_config))
         .route("/config/backup", post(backup_config))
         .route("/config/permissions", post(upsert_permissions))
+        .route("/config/current-model", get(get_current_model))
         .with_state(state)
 }
 

crates/goose-server/src/routes/reply.rs

@@ -88,6 +88,10 @@ enum MessageEvent {
     Finish {
         reason: String,
     },
+    ModelChange {
+        model: String,
+        mode: String,
+    },
     Notification {
         request_id: String,
         message: JsonRpcMessage,
@@ -233,6 +237,17 @@ async fn handler(
                                 }
                             });
                         }
+                        Ok(Some(Ok(AgentEvent::ModelChange { model, mode }))) => {
+                            if let Err(e) = stream_event(MessageEvent::ModelChange { model, mode }, &tx).await {
+                                tracing::error!("Error sending model change through channel: {}", e);
+                                let _ = stream_event(
+                                    MessageEvent::Error {
+                                        error: e.to_string(),
+                                    },
+                                    &tx,
+                                ).await;
+                            }
+                        }
                         Ok(Some(Ok(AgentEvent::McpNotification((request_id, n))))) => {
                             if let Err(e) = stream_event(MessageEvent::Notification{
                                 request_id: request_id.clone(),
@@ -352,6 +367,10 @@ async fn ask_handler(
                     }
                 }
             }
+            Ok(AgentEvent::ModelChange { model, mode }) => {
+                // Log model change for non-streaming
+                tracing::info!("Model changed to {} in {} mode", model, mode);
+            }
             Ok(AgentEvent::McpNotification(n)) => {
                 // Handle notifications if needed
                 tracing::info!("Received notification: {:?}", n);

crates/goose/src/agents/agent.rs

@@ -65,6 +65,7 @@ pub struct Agent {
 pub enum AgentEvent {
     Message(Message),
     McpNotification((String, JsonRpcMessage)),
+    ModelChange { model: String, mode: String },
 }
 
 impl Agent {
@@ -582,6 +583,26 @@ impl Agent {
                     &toolshim_tools,
                 ).await {
                     Ok((response, usage)) => {
+                        // Emit model change event if provider is lead-worker
+                        let provider = self.provider().await?;
+                        if let Some(lead_worker) = provider.as_lead_worker() {
+                            // The actual model used is in the usage
+                            let active_model = usage.model.clone();
+                            let (lead_model, worker_model) = lead_worker.get_model_info();
+                            let mode = if active_model == lead_model {
+                                "lead"
+                            } else if active_model == worker_model {
+                                "worker"
+                            } else {
+                                "unknown"
+                            };
+
+                            yield AgentEvent::ModelChange {
+                                model: active_model,
+                                mode: mode.to_string(),
+                            };
+                        }
+
                         // record usage for the session in the session file
                         if let Some(session_config) = session.clone() {
                             Self::update_session_metrics(session_config, &usage, messages.len()).await?;

crates/goose/src/providers/base.rs

@@ -152,6 +152,9 @@ use async_trait::async_trait;
 pub trait LeadWorkerProviderTrait {
     /// Get information about the lead and worker models for logging
     fn get_model_info(&self) -> (String, String);
+
+    /// Get the currently active model name
+    fn get_active_model(&self) -> String;
 }
 
 /// Base trait for AI providers (OpenAI, Anthropic, etc)
@@ -207,6 +210,17 @@ pub trait Provider: Send + Sync {
     fn as_lead_worker(&self) -> Option<&dyn LeadWorkerProviderTrait> {
         None
     }
+
+    /// Get the currently active model name
+    /// For regular providers, this returns the configured model
+    /// For LeadWorkerProvider, this returns the currently active model (lead or worker)
+    fn get_active_model_name(&self) -> String {
+        if let Some(lead_worker) = self.as_lead_worker() {
+            lead_worker.get_active_model()
+        } else {
+            self.get_model_config().model_name
+        }
+    }
 }
 
 #[cfg(test)]

crates/goose/src/providers/lead_worker.rs

@@ -291,6 +291,16 @@ impl LeadWorkerProviderTrait for LeadWorkerProvider {
         let worker_model = self.worker_provider.get_model_config().model_name;
         (lead_model, worker_model)
     }
+
+    /// Get the currently active model name
+    fn get_active_model(&self) -> String {
+        // Read from the global store which was set during complete()
+        use super::base::get_current_model;
+        get_current_model().unwrap_or_else(|| {
+            // Fallback to lead model if no current model is set
+            self.lead_provider.get_model_config().model_name
+        })
+    }
 }
 
 #[async_trait]
@@ -336,19 +346,31 @@ impl Provider for LeadWorkerProvider {
             "worker"
         };
 
+        // Get the active model name and update the global store
+        let active_model_name = if turn_count < self.lead_turns || in_fallback {
+            self.lead_provider.get_model_config().model_name.clone()
+        } else {
+            self.worker_provider.get_model_config().model_name.clone()
+        };
+
+        // Update the global current model store
+        super::base::set_current_model(&active_model_name);
+
         if in_fallback {
             tracing::info!(
-                "🔄 Using {} provider for turn {} (FALLBACK MODE: {} turns remaining)",
+                "🔄 Using {} provider for turn {} (FALLBACK MODE: {} turns remaining) - Model: {}",
                 provider_type,
                 turn_count + 1,
-                fallback_remaining
+                fallback_remaining,
+                active_model_name
             );
         } else {
             tracing::info!(
-                "Using {} provider for turn {} (lead_turns: {})",
+                "Using {} provider for turn {} (lead_turns: {}) - Model: {}",
                 provider_type,
                 turn_count + 1,
-                self.lead_turns
+                self.lead_turns,
+                active_model_name
             );
         }
 

crates/goose/src/scheduler.rs

@@ -1114,6 +1114,9 @@ async fn run_scheduled_job_internal(
                         Ok(AgentEvent::McpNotification(_)) => {
                             // Handle notifications if needed
                         }
+                        Ok(AgentEvent::ModelChange { .. }) => {
+                            // Model change events are informational, just continue
+                        }
                         Err(e) => {
                             tracing::error!(
                                 "[Job {}] Error receiving message from agent: {}",

crates/goose/tests/agent.rs

@@ -136,6 +136,9 @@ async fn run_truncate_test(
             Ok(AgentEvent::McpNotification(n)) => {
                 println!("MCP Notification: {n:?}");
             }
+            Ok(AgentEvent::ModelChange { .. }) => {
+                // Model change events are informational, just continue
+            }
             Err(e) => {
                 println!("Error: {:?}", e);
                 return Err(e);