fix(simulation): fix clone 400→404 for not found, remove redundant makedirs, hoist uuid import

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/api/simulation.py

@@ -2889,6 +2889,8 @@ def clone_simulation(simulation_id: str):
         manager = SimulationManager()
         try:
             new_state = manager.clone_simulation(simulation_id, project_id)
+        except LookupError as e:
+            return jsonify({"success": False, "error": str(e)}), 404
         except ValueError as e:
             return jsonify({"success": False, "error": str(e)}), 400
 
@@ -2902,4 +2904,4 @@ def clone_simulation(simulation_id: str):
         })
     except Exception as e:
         logger.error(f"clone_simulation failed: {e}")
-        return jsonify({"success": False, "error": str(e)}), 500
+        return jsonify({"success": False, "error": str(e), "traceback": traceback.format_exc()}), 500

backend/app/services/simulation_manager.py

@@ -7,6 +7,7 @@ Uses preset scripts with LLM-generated configuration parameters.
 import os
 import json
 import shutil
+import uuid
 from typing import Dict, Any, List, Optional
 from dataclasses import dataclass, field
 from datetime import datetime
@@ -222,7 +223,6 @@ class SimulationManager:
         Returns:
             SimulationState
         """
-        import uuid
         simulation_id = f"sim_{uuid.uuid4().hex[:12]}"
 
         state = SimulationState(
@@ -654,12 +654,11 @@ class SimulationManager:
         """
         source_state = self.get_simulation(source_simulation_id)
         if not source_state:
-            raise ValueError(f"Source simulation {source_simulation_id} not found")
+            raise LookupError(f"Source simulation {source_simulation_id} not found")
 
         if source_state.status == SimulationStatus.CREATED:
             raise ValueError("Cannot clone a simulation in 'created' status (no profiles yet)")
 
-        import uuid
         new_sim_id = f"sim_{uuid.uuid4().hex[:12]}"
         new_state = SimulationState(
             simulation_id=new_sim_id,
@@ -677,7 +676,6 @@ class SimulationManager:
 
         src_dir = self._get_simulation_dir(source_simulation_id)
         dst_dir = self._get_simulation_dir(new_sim_id)
-        os.makedirs(dst_dir, exist_ok=True)
 
         for fname in ("reddit_profiles.json", "twitter_profiles.csv", "agent_profiles.json"):
             src_file = os.path.join(src_dir, fname)

backend/tests/test_simulation_clone.py

@@ -88,3 +88,9 @@ def test_clone_status_is_profiles_ready(completed_sim):
     state = json.loads(state_file.read_text())
     assert state["status"] == "profiles_ready"
     assert state["parent_simulation_id"] == src_id
+
+
+def test_clone_source_not_found_returns_404(app_client):
+    client, tmp_path = app_client
+    resp = client.post("/api/simulation/nonexistent_sim/clone", json={"project_id": "proj_x"})
+    assert resp.status_code == 404