🐛 Ensure GridMetrics are sent with msgpack

Author: kzscisoft

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Change Log
 
+## Unreleased
+
+- Ensures `GridMetrics` are sent via `msgpack` the same as `Metrics`.
+
 ## [v2.2.2](https://github.com/simvue-io/client/releases/tag/v2.2.2) - 2025-10-14
 
 - Enforced use of UTC for all datetime recording.

simvue/api/objects/grids.py

@@ -258,6 +258,9 @@ def __init__(
         self._run_id = self._staging.get("run")
         self._is_set = True
 
+    def _post_single(self, **kwargs) -> dict[str, typing.Any]:
+        return super()._post_single(is_json=False, **kwargs)
+
     @staticmethod
     def run_grids_endpoint(run: str | None = None) -> URL:
         """Returns the URL for grids for a specific run."""