feat: spawn v2 make task name as mandatory (#15986)

codex-rs/core/src/tools/handlers/multi_agents_tests.rs

@@ -321,6 +321,40 @@ async fn spawn_agent_returns_agent_id_without_task_name() {
     assert_eq!(success, Some(true));
 }
 
+#[tokio::test]
+async fn multi_agent_v2_spawn_requires_task_name() {
+    let (mut session, mut turn) = make_session_and_context().await;
+    let manager = thread_manager();
+    let root = manager
+        .start_thread((*turn.config).clone())
+        .await
+        .expect("root thread should start");
+    session.services.agent_control = manager.agent_control();
+    session.conversation_id = root.thread_id;
+    let mut config = (*turn.config).clone();
+    config
+        .features
+        .enable(Feature::MultiAgentV2)
+        .expect("test config should allow feature update");
+    turn.config = Arc::new(config);
+
+    let invocation = invocation(
+        Arc::new(session),
+        Arc::new(turn),
+        "spawn_agent",
+        function_payload(json!({
+            "message": "inspect this repo"
+        })),
+    );
+    let Err(err) = SpawnAgentHandlerV2.handle(invocation).await else {
+        panic!("missing task_name should be rejected");
+    };
+    let FunctionCallError::RespondToModel(message) = err else {
+        panic!("missing task_name should surface as a model-facing error");
+    };
+    assert!(message.contains("missing field `task_name`"));
+}
+
 #[tokio::test]
 async fn spawn_agent_errors_when_manager_dropped() {
     let (session, turn) = make_session_and_context().await;

codex-rs/core/src/tools/handlers/multi_agents_v2/spawn.rs

@@ -83,7 +83,7 @@ impl ToolHandler for Handler {
                     &turn.session_source,
                     child_depth,
                     role_name,
-                    args.task_name.clone(),
+                    Some(args.task_name.clone()),
                 )?),
                 SpawnAgentOptions {
                     fork_parent_spawn_call_id: args.fork_context.then(|| call_id.clone()),
@@ -132,7 +132,6 @@ impl ToolHandler for Handler {
             .and_then(|snapshot| snapshot.reasoning_effort)
             .unwrap_or(args.reasoning_effort.unwrap_or_default());
         let nickname = new_agent_nickname.clone();
-        let task_name = new_agent_path.clone();
         session
             .send_event(
                 &turn,
@@ -150,16 +149,21 @@ impl ToolHandler for Handler {
                 .into(),
             )
             .await;
-        let new_thread_id = result?.thread_id;
+        let _ = result?;
         let role_tag = role_name.unwrap_or(DEFAULT_ROLE_NAME);
         turn.session_telemetry.counter(
             "codex.multi_agent.spawn",
             /*inc*/ 1,
             &[("role", role_tag)],
         );
+        let task_name = new_agent_path.ok_or_else(|| {
+            FunctionCallError::RespondToModel(
+                "spawned agent is missing a canonical task name".to_string(),
+            )
+        })?;
 
         Ok(SpawnAgentResult {
-            agent_id: task_name.is_none().then(|| new_thread_id.to_string()),
+            agent_id: None,
             task_name,
             nickname,
         })
@@ -170,7 +174,7 @@ impl ToolHandler for Handler {
 struct SpawnAgentArgs {
     message: Option<String>,
     items: Option<Vec<UserInput>>,
-    task_name: Option<String>,
+    task_name: String,
     agent_type: Option<String>,
     model: Option<String>,
     reasoning_effort: Option<ReasoningEffort>,
@@ -181,7 +185,7 @@ struct SpawnAgentArgs {
 #[derive(Debug, Serialize)]
 pub(crate) struct SpawnAgentResult {
     agent_id: Option<String>,
-    task_name: Option<String>,
+    task_name: String,
     nickname: Option<String>,
 }
 

codex-rs/core/src/tools/spec.rs

@@ -157,10 +157,10 @@ fn spawn_agent_output_schema_v2() -> JsonValue {
         "properties": {
             "agent_id": {
                 "type": ["string", "null"],
-                "description": "Thread identifier for the spawned agent when no task name was assigned."
+                "description": "Legacy thread identifier for the spawned agent."
             },
             "task_name": {
-                "type": ["string", "null"],
+                "type": "string",
                 "description": "Canonical task name for the spawned agent."
             },
             "nickname": {
@@ -1215,13 +1215,13 @@ fn create_spawn_agent_tool_v1(config: &ToolsConfig) -> ToolSpec {
 
 fn create_spawn_agent_tool_v2(config: &ToolsConfig) -> ToolSpec {
     let available_models_description = spawn_agent_models_description(&config.available_models);
-    let return_value_description = "Returns the canonical task name when the spawned agent was named, otherwise the agent id, plus the user-facing nickname when available.";
+    let return_value_description = "Returns the canonical task name for the spawned agent, plus the user-facing nickname when available.";
     let mut properties = spawn_agent_common_properties(config);
     properties.insert(
         "task_name".to_string(),
         JsonSchema::String {
             description: Some(
-                "Optional task name for the new agent. Use lowercase letters, digits, and underscores."
+                "Task name for the new agent. Use lowercase letters, digits, and underscores."
                     .to_string(),
             ),
         },
@@ -1237,7 +1237,7 @@ fn create_spawn_agent_tool_v2(config: &ToolsConfig) -> ToolSpec {
         defer_loading: None,
         parameters: JsonSchema::Object {
             properties,
-            required: None,
+            required: Some(vec!["task_name".to_string()]),
             additional_properties: Some(false.into()),
         },
         output_schema: Some(spawn_agent_output_schema_v2()),

codex-rs/core/src/tools/spec_tests.rs

@@ -454,7 +454,7 @@ fn test_build_specs_multi_agent_v2_uses_task_names_and_hides_resume() {
         panic!("spawn_agent should use object params");
     };
     assert!(properties.contains_key("task_name"));
-    assert_eq!(required.as_ref(), None);
+    assert_eq!(required.as_ref(), Some(&vec!["task_name".to_string()]));
     let output_schema = output_schema
         .as_ref()
         .expect("spawn_agent should define output schema");