fix(middleware): fix present_files thread id fallback (#2181)

* fix present files thread id fallback

* fix: resolve present_files thread id from runtime config

backend/tests/test_present_file_tool_core_logic.py

@@ -10,6 +10,7 @@ def _make_runtime(outputs_path: str) -> SimpleNamespace:
     return SimpleNamespace(
         state={"thread_data": {"outputs_path": outputs_path}},
         context={"thread_id": "thread-1"},
+        config={},
     )
 
 
@@ -50,6 +51,34 @@ def test_present_files_keeps_virtual_outputs_path(tmp_path, monkeypatch):
     assert result.update["artifacts"] == ["/mnt/user-data/outputs/summary.json"]
 
 
+def test_present_files_uses_config_thread_id_when_context_missing(tmp_path, monkeypatch):
+    outputs_dir = tmp_path / "threads" / "thread-from-config" / "user-data" / "outputs"
+    outputs_dir.mkdir(parents=True)
+    artifact_path = outputs_dir / "summary.json"
+    artifact_path.write_text("{}")
+
+    monkeypatch.setattr(
+        present_file_tool_module,
+        "get_paths",
+        lambda: SimpleNamespace(resolve_virtual_path=lambda thread_id, path: artifact_path),
+    )
+
+    runtime = SimpleNamespace(
+        state={"thread_data": {"outputs_path": str(outputs_dir)}},
+        context={},
+        config={"configurable": {"thread_id": "thread-from-config"}},
+    )
+
+    result = present_file_tool_module.present_file_tool.func(
+        runtime=runtime,
+        filepaths=["/mnt/user-data/outputs/summary.json"],
+        tool_call_id="tc-config",
+    )
+
+    assert result.update["artifacts"] == ["/mnt/user-data/outputs/summary.json"]
+    assert result.update["messages"][0].content == "Successfully presented files"
+
+
 def test_present_files_rejects_paths_outside_outputs(tmp_path):
     outputs_dir = tmp_path / "threads" / "thread-1" / "user-data" / "outputs"
     workspace_dir = tmp_path / "threads" / "thread-1" / "user-data" / "workspace"