CLI: write the run log file synchronously

tests/test_run/test_logging.py

@@ -57,6 +57,13 @@ def test_path_contains_run_title(self):
             result = configure_logger_for_run("special_run_title")
         assert "special_run_title" in result
 
+    def test_log_file_sink_is_not_enqueued(self):
+        with patch("th_cli.test_run.logging.logger") as mock_logger:
+            result = configure_logger_for_run("run")
+        mock_logger.add.assert_called_once()
+        assert mock_logger.add.call_args.args[0] == result
+        assert mock_logger.add.call_args.kwargs["enqueue"] is False
+
     def test_log_handler_remains_none_when_streaming_disabled(self):
         with patch("th_cli.test_run.logging.logger"):
             configure_logger_for_run("run", enable_log_streaming=False)

th_cli/test_run/logging.py

@@ -54,7 +54,12 @@ def configure_logger_for_run(title: str, enable_log_streaming: bool = False) ->
         f"test_run_{title}_{timestamp}.log",
     )
 
-    logger.add(log_path, enqueue=True, format=config.log_config.format, mode="w")
+    # enqueue=False: write the file synchronously. With enqueue=True every
+    # line is pickled onto a multiprocessing queue and handed to a worker
+    # thread, which costs ~3x more per line than the write itself and is what
+    # limits how fast the CLI can drain a large run's log records. Loguru
+    # still serialises concurrent writers with a per-handler lock.
+    logger.add(log_path, enqueue=False, format=config.log_config.format, mode="w")
 
     # Add streaming sink if enabled
     if enable_log_streaming: