diff --git a/apps/ai-game-creator-shell/src-tauri/src/agent/design_runtime.rs b/apps/ai-game-creator-shell/src-tauri/src/agent/design_runtime.rs
index 0f6b61662..36e32fdff 100644
--- a/apps/ai-game-creator-shell/src-tauri/src/agent/design_runtime.rs
+++ b/apps/ai-game-creator-shell/src-tauri/src/agent/design_runtime.rs
@@ -767,6 +767,7 @@ pub(crate) async fn continue_design_agent_at(
     input: DesignInput,
     emit: impl FnMut(DesignEvent) + Send,
 ) -> Result<DesignView, String> {
+    ensure_design_runtime_active(root)?;
     let project_id = design_project_id(root)?;
     ensure_design_workspace(root)?;
     let active = try_open_game_creator_agent_runtime_task_lock_file(root, DESIGN_ACTIVE_LOCK)?
@@ -798,6 +799,7 @@ pub(crate) async fn decide_design_phase_at(
     approved: bool,
     emit: impl FnMut(DesignEvent) + Send,
 ) -> Result<DesignView, String> {
+    ensure_design_runtime_active(root)?;
     let project_id = design_project_id(root)?;
     ensure_design_workspace(root)?;
     let active = try_open_game_creator_agent_runtime_task_lock_file(root, DESIGN_ACTIVE_LOCK)?
@@ -810,6 +812,16 @@ pub(crate) async fn decide_design_phase_at(
     finish_design_command(root, resources, session, active, run, emit).await
 }
 
+fn ensure_design_runtime_active(root: &Path) -> Result<(), String> {
+    if read_design_runtime_mode(root)?
+        .as_ref()
+        .is_some_and(|mode| mode.active_runtime == "game")
+    {
+        return Err("当前项目已切换到游戏运行态，不能继续策划 Agent".into());
+    }
+    Ok(())
+}
+
 #[tauri::command]
 pub(crate) fn hydrate_design_agent_session(
     project_path: String,
@@ -961,6 +973,16 @@ mod fake_provider {
 #[cfg(test)]
 mod tests {
     use super::*;
+
+    #[test]
+    fn design_runtime_rejects_design_execution_in_game_mode() {
+        let temporary = tempfile::tempdir().expect("create runtime mode root");
+        let root = temporary.path();
+        write_design_runtime_mode(root, "game").expect("write game runtime mode");
+
+        let error = ensure_design_runtime_active(root).expect_err("game mode must reject design");
+        assert!(error.contains("游戏运行态"));
+    }
     use serde_json::json;
     use std::fs;
 
diff --git a/apps/ai-game-creator-shell/src/features/app-shell/WorkspaceLauncher.tsx b/apps/ai-game-creator-shell/src/features/app-shell/WorkspaceLauncher.tsx
index 8ee4cde5c..bca56303b 100644
--- a/apps/ai-game-creator-shell/src/features/app-shell/WorkspaceLauncher.tsx
+++ b/apps/ai-game-creator-shell/src/features/app-shell/WorkspaceLauncher.tsx
@@ -383,6 +383,7 @@ export function WorkspaceLauncherShell({
                 orchestrationMode="single-supervisor"
                 projectSupervisorOnly
                 planningStartMode={
+                  agentRuntimeMode === 'design' &&
                   currentProjectContext.startMode === 'planning'
                 }
                 playRequest={playRequest}