diff --git a/EvoScientist/cli/commands.py b/EvoScientist/cli/commands.py
index b5a0fd1..b870bad 100644
--- a/EvoScientist/cli/commands.py
+++ b/EvoScientist/cli/commands.py
@@ -306,12 +306,22 @@ async def compact_conversation(agent: Any, thread_id: str | None) -> CompactResu
     # Generate summary (LLM call)
     summary = await middleware._acreate_summary(to_summarize)
 
+    # Inject thread_id into LangGraph contextvar so _get_thread_id() finds it
+    # (compact runs outside a runnable context, so get_config() would fail
+    # and the middleware would generate a random "session_xxx" filename instead
+    # of reusing the real thread_id).
+    from langgraph.config import var_child_runnable_config
+
+    _token = var_child_runnable_config.set(config)
+
     # Offload old messages to backend
     file_path: str | None = None
     try:
         file_path = await middleware._aoffload_to_backend(backend, to_summarize)
     except Exception:
         pass  # non-fatal — proceed without offloaded history
+    finally:
+        var_child_runnable_config.reset(_token)
 
     summary_msg = middleware._build_new_messages_with_path(summary, file_path)[0]