diff --git a/codex-rs/core/config.schema.json b/codex-rs/core/config.schema.json
index c9711688ef..7c3c0edd75 100644
--- a/codex-rs/core/config.schema.json
+++ b/codex-rs/core/config.schema.json
@@ -723,6 +723,9 @@
             "secret_auth_storage": {
               "type": "boolean"
             },
+            "send_async_message": {
+              "type": "boolean"
+            },
             "shell_snapshot": {
               "type": "boolean"
             },
@@ -5582,6 +5585,9 @@
         "secret_auth_storage": {
           "type": "boolean"
         },
+        "send_async_message": {
+          "type": "boolean"
+        },
         "shell_snapshot": {
           "type": "boolean"
         },
diff --git a/codex-rs/features/src/lib.rs b/codex-rs/features/src/lib.rs
index 7a25605246..61bbc3dd3e 100644
--- a/codex-rs/features/src/lib.rs
+++ b/codex-rs/features/src/lib.rs
@@ -262,6 +262,8 @@ pub enum Feature {
     MentionsV2,
     /// Allow request_user_input in Default collaboration mode.
     DefaultModeRequestUserInput,
+    /// Allow sending a user-visible message without ending the current turn.
+    SendAsyncMessage,
     /// Enable automatic review for approval prompts.
     GuardianApproval,
     /// Reuse encrypted parent compaction when restarting Guardian review sessions.
@@ -1350,6 +1352,12 @@ pub const FEATURES: &[FeatureSpec] = &[
         stage: Stage::UnderDevelopment,
         default_enabled: false,
     },
+    FeatureSpec {
+        id: Feature::SendAsyncMessage,
+        key: "send_async_message",
+        stage: Stage::UnderDevelopment,
+        default_enabled: false,
+    },
     FeatureSpec {
         id: Feature::TerminalVisualizationInstructions,
         key: "terminal_visualization_instructions",