diff --git a/crates/runtime-api/src/lib.rs b/crates/runtime-api/src/lib.rs
index ab2a611af..757ab0ee0 100644
--- a/crates/runtime-api/src/lib.rs
+++ b/crates/runtime-api/src/lib.rs
@@ -402,6 +402,8 @@ pub struct WorkingDirectoryStatus {
 #[serde(rename_all = "snake_case")]
 pub enum WorkerInputKind {
     User,
+    /// Agent input accepted only while Idle; never enters the human Submit queue.
+    UserIfIdle,
     Notify,
     Compact,
     ListRewindTargets,
diff --git a/crates/worker-runtime/src/http_server.rs b/crates/worker-runtime/src/http_server.rs
index 1935f023e..9c1a4f7fa 100644
--- a/crates/worker-runtime/src/http_server.rs
+++ b/crates/worker-runtime/src/http_server.rs
@@ -3490,14 +3490,31 @@ mod tests {
         conflicting_request.create_fingerprint = "different-fingerprint".to_string();
         let generated = client.create_worker(generated_request).await.unwrap();
         assert_eq!(generated.worker.worker_id.to_string(), generated_worker_id);
-        let generated_input: runtime_api::WorkerInput = serde_json::from_value(
-            serde_json::to_value(WorkerInput::user("generated client input")).unwrap(),
-        )
-        .unwrap();
-        client
-            .send_worker_input(generated_worker_id.clone(), generated_input)
-            .await
-            .unwrap();
+        for kind in [
+            crate::interaction::WorkerInputKind::User,
+            crate::interaction::WorkerInputKind::UserIfIdle,
+        ] {
+            let mut input = WorkerInput::user("generated client input");
+            input.kind = kind.clone();
+            input.submission_request_id = Some(format!("generated-{kind:?}"));
+            // The remote adapter performs this same conversion before sending.
+            // Both the generated API contract and the HTTP receiver must retain
+            // Idle-only admission rather than silently downgrading it to User.
+            let generated_input: runtime_api::WorkerInput =
+                serde_json::from_value(serde_json::to_value(&input).unwrap()).unwrap();
+            assert_eq!(
+                serde_json::to_value(&generated_input).unwrap(),
+                serde_json::to_value(&input).unwrap()
+            );
+            let response = client
+                .send_worker_input(generated_worker_id.clone(), generated_input)
+                .await
+                .unwrap();
+            assert_eq!(
+                Some(response.ack.submission.unwrap().submission_request_id),
+                input.submission_request_id
+            );
+        }
         client
             .stop_worker(
                 generated_worker_id.clone(),
diff --git a/crates/workspace-server/src/hosts.rs b/crates/workspace-server/src/hosts.rs
index 40ab2b09b..aa903a20f 100644
--- a/crates/workspace-server/src/hosts.rs
+++ b/crates/workspace-server/src/hosts.rs
@@ -6341,6 +6341,28 @@ mod tests {
         assert_eq!(delivered.content, archive.content);
     }
 
+    #[test]
+    fn runtime_input_contract_preserves_every_input_kind() {
+        for kind in [
+            EmbeddedWorkerInputKind::User,
+            EmbeddedWorkerInputKind::UserIfIdle,
+            EmbeddedWorkerInputKind::Notify,
+            EmbeddedWorkerInputKind::Compact,
+            EmbeddedWorkerInputKind::ListRewindTargets,
+            EmbeddedWorkerInputKind::RegisterPeer,
+        ] {
+            let input = EmbeddedWorkerInput {
+                kind,
+                content: "contract test".to_string(),
+                submission_request_id: Some("contract-request".to_string()),
+                segments: Some(vec![protocol::Segment::text("contract test")]),
+            };
+            let wire: runtime_api::WorkerInput = runtime_contract_convert(input.clone()).unwrap();
+            let decoded: EmbeddedWorkerInput = runtime_contract_convert(wire).unwrap();
+            assert_eq!(decoded, input);
+        }
+    }
+
     #[test]
     fn remote_profile_source_uses_workspace_config_archive_reference() {
         let request = embedded_spawn_request();