feat: lead/worker model (#2719)

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

@@ -7,6 +7,7 @@ use goose::session;
 use goose::session::Identifier;
 use mcp_client::transport::Error as McpClientError;
 use std::process;
+use std::sync::Arc;
 
 use super::output;
 use super::Session;
@@ -55,6 +56,22 @@ pub async fn build_session(session_config: SessionBuilderConfig) -> Session {
     // Create the agent
     let agent: Agent = Agent::new();
     let new_provider = create(&provider_name, model_config).unwrap();
+
+    // Keep a reference to the provider for display_session_info
+    let provider_for_display = Arc::clone(&new_provider);
+
+    // Log model information at startup
+    if let Some(lead_worker) = new_provider.as_lead_worker() {
+        let (lead_model, worker_model) = lead_worker.get_model_info();
+        tracing::info!(
+            "🤖 Lead/Worker Mode Enabled: Lead model (first 3 turns): {}, Worker model (turn 4+): {}, Auto-fallback on failures: Enabled",
+            lead_model,
+            worker_model
+        );
+    } else {
+        tracing::info!("🤖 Using model: {}", model);
+    }
+
     agent
         .update_provider(new_provider)
         .await
@@ -217,6 +234,12 @@ pub async fn build_session(session_config: SessionBuilderConfig) -> Session {
         session.agent.override_system_prompt(override_prompt).await;
     }
 
-    output::display_session_info(session_config.resume, &provider_name, &model, &session_file);
+    output::display_session_info(
+        session_config.resume,
+        &provider_name,
+        &model,
+        &session_file,
+        Some(&provider_for_display),
+    );
     session
 }

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

@@ -10,6 +10,7 @@ use std::cell::RefCell;
 use std::collections::HashMap;
 use std::io::Error;
 use std::path::Path;
+use std::sync::Arc;
 use std::time::Duration;
 
 // Re-export theme for use in main
@@ -536,7 +537,13 @@ fn shorten_path(path: &str, debug: bool) -> String {
 }
 
 // Session display functions
-pub fn display_session_info(resume: bool, provider: &str, model: &str, session_file: &Path) {
+pub fn display_session_info(
+    resume: bool,
+    provider: &str,
+    model: &str,
+    session_file: &Path,
+    provider_instance: Option<&Arc<dyn goose::providers::base::Provider>>,
+) {
     let start_session_msg = if resume {
         "resuming session |"
     } else if session_file.to_str() == Some("/dev/null") || session_file.to_str() == Some("NUL") {
@@ -544,14 +551,42 @@ pub fn display_session_info(resume: bool, provider: &str, model: &str, session_f
     } else {
         "starting session |"
     };
-    println!(
-        "{} {} {} {} {}",
-        style(start_session_msg).dim(),
-        style("provider:").dim(),
-        style(provider).cyan().dim(),
-        style("model:").dim(),
-        style(model).cyan().dim(),
-    );
+
+    // Check if we have lead/worker mode
+    if let Some(provider_inst) = provider_instance {
+        if let Some(lead_worker) = provider_inst.as_lead_worker() {
+            let (lead_model, worker_model) = lead_worker.get_model_info();
+            println!(
+                "{} {} {} {} {} {} {}",
+                style(start_session_msg).dim(),
+                style("provider:").dim(),
+                style(provider).cyan().dim(),
+                style("lead model:").dim(),
+                style(&lead_model).cyan().dim(),
+                style("worker model:").dim(),
+                style(&worker_model).cyan().dim(),
+            );
+        } else {
+            println!(
+                "{} {} {} {} {}",
+                style(start_session_msg).dim(),
+                style("provider:").dim(),
+                style(provider).cyan().dim(),
+                style("model:").dim(),
+                style(model).cyan().dim(),
+            );
+        }
+    } else {
+        // Fallback to original behavior if no provider instance
+        println!(
+            "{} {} {} {} {}",
+            style(start_session_msg).dim(),
+            style("provider:").dim(),
+            style(provider).cyan().dim(),
+            style("model:").dim(),
+            style(model).cyan().dim(),
+        );
+    }
 
     if session_file.to_str() != Some("/dev/null") && session_file.to_str() != Some("NUL") {
         println!(