Stabilize multi-agent feature flag (#14622)

- make multi_agent stable and enabled by default
- update feature and tool-spec coverage to match the new default

---------

Co-authored-by: Codex <noreply@openai.com>

codex-rs/core/src/features.rs

@@ -711,12 +711,8 @@ pub const FEATURES: &[FeatureSpec] = &[
     FeatureSpec {
         id: Feature::Collab,
         key: "multi_agent",
-        stage: Stage::Experimental {
-            name: "Subagents",
-            menu_description: "Ask Codex to spawn subagents to parallelize the work and move faster.",
-            announcement: "NEW: Subagents can now be spawned by Codex. Enable in /experimental and restart Codex!",
-        },
-        default_enabled: false,
+        stage: Stage::Stable,
+        default_enabled: true,
     },
     FeatureSpec {
         id: Feature::SpawnCsv,

codex-rs/core/src/features_tests.rs

@@ -145,6 +145,12 @@ fn collab_is_legacy_alias_for_multi_agent() {
     assert_eq!(feature_for_key("collab"), Some(Feature::Collab));
 }
 
+#[test]
+fn multi_agent_is_stable_and_enabled_by_default() {
+    assert_eq!(Feature::Collab.stage(), Stage::Stable);
+    assert_eq!(Feature::Collab.default_enabled(), true);
+}
+
 #[test]
 fn enable_fanout_is_under_development() {
     assert_eq!(Feature::SpawnCsv.stage(), Stage::UnderDevelopment);

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

@@ -459,6 +459,11 @@ fn test_full_toolset_specs_for_gpt5_codex_unified_exec_web_search() {
             search_content_types: None,
         },
         create_view_image_tool(config.can_request_original_image_detail),
+        create_spawn_agent_tool(&config),
+        create_send_input_tool(),
+        create_resume_agent_tool(),
+        create_wait_tool(),
+        create_close_agent_tool(),
     ] {
         expected.insert(tool_name(&spec).to_string(), spec);
     }
@@ -1184,6 +1189,11 @@ fn test_build_specs_gpt5_codex_default() {
             "apply_patch",
             "web_search",
             "view_image",
+            "spawn_agent",
+            "send_input",
+            "resume_agent",
+            "wait",
+            "close_agent",
         ],
     );
 }
@@ -1202,6 +1212,11 @@ fn test_build_specs_gpt51_codex_default() {
             "apply_patch",
             "web_search",
             "view_image",
+            "spawn_agent",
+            "send_input",
+            "resume_agent",
+            "wait",
+            "close_agent",
         ],
     );
 }
@@ -1222,6 +1237,11 @@ fn test_build_specs_gpt5_codex_unified_exec_web_search() {
             "apply_patch",
             "web_search",
             "view_image",
+            "spawn_agent",
+            "send_input",
+            "resume_agent",
+            "wait",
+            "close_agent",
         ],
     );
 }
@@ -1242,6 +1262,11 @@ fn test_build_specs_gpt51_codex_unified_exec_web_search() {
             "apply_patch",
             "web_search",
             "view_image",
+            "spawn_agent",
+            "send_input",
+            "resume_agent",
+            "wait",
+            "close_agent",
         ],
     );
 }
@@ -1260,6 +1285,11 @@ fn test_gpt_5_1_codex_max_defaults() {
             "apply_patch",
             "web_search",
             "view_image",
+            "spawn_agent",
+            "send_input",
+            "resume_agent",
+            "wait",
+            "close_agent",
         ],
     );
 }
@@ -1278,6 +1308,11 @@ fn test_codex_5_1_mini_defaults() {
             "apply_patch",
             "web_search",
             "view_image",
+            "spawn_agent",
+            "send_input",
+            "resume_agent",
+            "wait",
+            "close_agent",
         ],
     );
 }
@@ -1295,6 +1330,11 @@ fn test_gpt_5_defaults() {
             "request_user_input",
             "web_search",
             "view_image",
+            "spawn_agent",
+            "send_input",
+            "resume_agent",
+            "wait",
+            "close_agent",
         ],
     );
 }
@@ -1313,6 +1353,11 @@ fn test_gpt_5_1_defaults() {
             "apply_patch",
             "web_search",
             "view_image",
+            "spawn_agent",
+            "send_input",
+            "resume_agent",
+            "wait",
+            "close_agent",
         ],
     );
 }
@@ -1333,6 +1378,11 @@ fn test_gpt_5_1_codex_max_unified_exec_web_search() {
             "apply_patch",
             "web_search",
             "view_image",
+            "spawn_agent",
+            "send_input",
+            "resume_agent",
+            "wait",
+            "close_agent",
         ],
     );
 }

codex-rs/core/tests/suite/prompt_caching.rs

@@ -177,6 +177,11 @@ async fn prompt_tools_are_consistent_across_requests() -> anyhow::Result<()> {
         "apply_patch",
         "web_search",
         "view_image",
+        "spawn_agent",
+        "send_input",
+        "resume_agent",
+        "wait",
+        "close_agent",
     ]);
     let body0 = req1.single_request().body_json();
 

codex-rs/tui/src/app.rs

@@ -5074,6 +5074,7 @@ mod tests {
     #[tokio::test]
     async fn open_agent_picker_prompts_to_enable_multi_agent_when_disabled() -> Result<()> {
         let (mut app, mut app_event_rx, _op_rx) = make_test_app_with_channels().await;
+        let _ = app.config.features.disable(Feature::Collab);
 
         app.open_agent_picker().await;
         app.chat_widget