fix: accept metadata without retired capacity fields

README.md

@@ -188,8 +188,10 @@ no real credentials; native API integration is opt-in. See
 [CONTRIBUTING.md](https://github.com/MorphIQ-Labs/morphiq-sdk-python/blob/main/CONTRIBUTING.md) and [RELEASE.md](https://github.com/MorphIQ-Labs/morphiq-sdk-python/blob/main/RELEASE.md).
 
 Clients make no automatic retries and do not follow redirects. A timeout
-may leave work charged. Missing `fcu_charged` means unreported, not zero; internal
-`units_charged` is not a commercial CU charge.
+may leave work charged. Only `fcu_quoted` and `fcu_charged` report commercial CUs.
+Missing `fcu_charged` means unreported, not zero. The retired `units_charged` and
+`compute_schedule_version` fields are optional; they remain accepted from older
+deployments and are never used to calculate a charge.
 
 The SDK preserves server results, numerical diagnostics, request IDs, engine
 provenance and commercial Compute Units (CU). Numerical engines, model selection,

src/morphiq_sdk/models.py

@@ -229,16 +229,17 @@ class _CommercialMetadata(_Response):
 class ResponseMetadata(_CommercialMetadata):
     """Server provenance and optional commercial CU evidence.
 
-    ``units_charged`` is an internal compute weight, not a commercial CU charge.
+    Only ``fcu_quoted`` and ``fcu_charged`` are commercial CU evidence.
+    Retired capacity fields are optional for compatibility with older deployments.
     Missing ``fcu_charged`` means unreported, not zero.
     """
 
     request_id: str
     api_version: str
     engine_version: str
     engines: list[EngineIdentity]
-    units_charged: int = Field(ge=0)
-    compute_schedule_version: str
+    units_charged: int | None = Field(default=None, ge=0, deprecated=True)
+    compute_schedule_version: str | None = Field(default=None, deprecated=True)
 
 
 class ServiceErrorMetadata(_CommercialMetadata):

tests/test_pricing.py

@@ -460,3 +460,16 @@ async def aclose(self):
         assert transport.closed
 
     asyncio.run(run())
+
+
+@pytest.mark.parametrize("mode", ["sync", "async"])
+def test_retired_capacity_fields_are_not_required_or_used_as_cu(mode, cases):
+    body = copy.deepcopy(cases[0]["response"])
+    body["metadata"].pop("units_charged")
+    body["metadata"].pop("compute_schedule_version")
+    body["metadata"].update(fcu_quoted=50, fcu_charged=50)
+    result = invoke(mode, httpx.MockTransport(lambda _: httpx.Response(200, json=body)))
+    assert result.metadata.fcu_quoted == 50
+    assert result.metadata.fcu_charged == 50
+    assert result.model_dump()["metadata"]["units_charged"] is None
+    assert result.model_dump()["metadata"]["compute_schedule_version"] is None