fix(compact_20260112): propagate allowed_model_region to summary subrequest

The router enforces region restrictions by reading allowed_model_region
from top-level request kwargs (Router._common_checks_available_deployment),
but the compact_20260112 summary subrequest only forwarded litellm_metadata.
A region-restricted caller could trigger compaction and have their conversation
summarized by a deployment outside the permitted region.

Extract allowed_model_region from user_api_key_auth and pass it through
_call_summary_model as a top-level kwarg so the router applies the same
region constraints the parent request would.

litellm/llms/anthropic/experimental_pass_through/context_management/editors/compact.py

@@ -525,6 +525,7 @@ async def _call_summary_model(
     summary_messages: List[Dict[str, Any]],
     metadata: Dict[str, Any],
     llm_router: Any,
+    allowed_model_region: Optional[str] = None,
 ) -> Any:
     """Invoke the configured summary model.
 
@@ -541,12 +542,19 @@ async def _call_summary_model(
     # post-call spend hooks read for budget attribution. The provider-level
     # ``metadata`` kwarg corresponds to the upstream API request body and would
     # not flow into spend tracking.
+    # ``allowed_model_region`` must travel as a top-level kwarg because the
+    # router enforces region restrictions by reading ``request_kwargs`` directly
+    # (see ``Router._common_checks_available_deployment``); without this the
+    # summary subrequest could be routed to a deployment outside the caller's
+    # permitted region.
     call_kwargs: Dict[str, Any] = {
         "model": summary_model,
         "messages": summary_messages,
         "max_tokens": COMPACT_SUMMARY_MAX_TOKENS,
         "litellm_metadata": metadata,
     }
+    if allowed_model_region is not None:
+        call_kwargs["allowed_model_region"] = allowed_model_region
     if llm_router is not None and hasattr(llm_router, "acompletion"):
         return await llm_router.acompletion(**call_kwargs)
     return await litellm.acompletion(**call_kwargs)
@@ -754,6 +762,7 @@ async def apply_compact_20260112(  # noqa: PLR0915
         effective_messages, prompt, system=augmented_system
     )
     propagated_metadata = _propagate_metadata(litellm_metadata)
+    allowed_model_region = getattr(user_api_key_auth, "allowed_model_region", None)
 
     try:
         response = await _call_summary_model(
@@ -761,6 +770,7 @@ async def apply_compact_20260112(  # noqa: PLR0915
             summary_messages=summary_messages,
             metadata=propagated_metadata,
             llm_router=llm_router,
+            allowed_model_region=allowed_model_region,
         )
     except Exception as e:
         verbose_logger.warning("compact_20260112: summary call failed: %s", e)

tests/test_litellm/llms/anthropic/experimental_pass_through/context_management/test_compact.py

@@ -1194,6 +1194,90 @@ async def test_summary_model_allowed_when_no_user_api_key_auth():
     assert result.compaction_block is not None
 
 
+async def test_summary_call_propagates_allowed_model_region():
+    """``allowed_model_region`` from ``user_api_key_auth`` is propagated to the
+    summary subrequest as a top-level kwarg so the router applies the same
+    region restriction the parent request would.
+    """
+    messages = _simple_messages()
+    mock_call = AsyncMock(return_value=_make_mock_response("<summary>ok</summary>"))
+
+    auth = _fake_user_api_key_auth(key_models=["all-proxy-models"])
+    auth.allowed_model_region = "eu"
+
+    with (
+        patch(
+            "litellm.llms.anthropic.experimental_pass_through.context_management.editors.compact._read_summary_model_setting",
+            return_value="claude-haiku-4-5",
+        ),
+        patch("litellm.token_counter", return_value=200_000),
+        patch(
+            "litellm.llms.anthropic.experimental_pass_through.context_management.editors.compact._call_summary_model",
+            mock_call,
+        ),
+    ):
+        await apply_compact_20260112(
+            model=MODEL,
+            messages=messages,
+            tools=None,
+            system=None,
+            edit_spec=_EDIT_SPEC_DEFAULT,
+            user_api_key_auth=auth,
+        )
+
+    mock_call.assert_awaited_once()
+    assert mock_call.await_args.kwargs.get("allowed_model_region") == "eu"
+
+
+async def test_summary_call_omits_allowed_model_region_when_unset():
+    """Callers without a region restriction must not get an ``allowed_model_region=None``
+    kwarg, which would otherwise force the router to evaluate region filtering.
+    """
+    from litellm.llms.anthropic.experimental_pass_through.context_management.editors.compact import (
+        _call_summary_model,
+    )
+
+    captured_kwargs: dict = {}
+
+    class _FakeRouter:
+        async def acompletion(self, **kwargs):
+            captured_kwargs.update(kwargs)
+            return _make_mock_response("<summary>x</summary>")
+
+    await _call_summary_model(
+        summary_model="claude-haiku-4-5",
+        summary_messages=[{"role": "user", "content": "hi"}],
+        metadata={},
+        llm_router=_FakeRouter(),
+    )
+
+    assert "allowed_model_region" not in captured_kwargs
+
+
+async def test_summary_call_forwards_allowed_model_region_when_set():
+    """When the caller is region-restricted, the kwarg reaches the router."""
+    from litellm.llms.anthropic.experimental_pass_through.context_management.editors.compact import (
+        _call_summary_model,
+    )
+
+    captured_kwargs: dict = {}
+
+    class _FakeRouter:
+        async def acompletion(self, **kwargs):
+            captured_kwargs.update(kwargs)
+            return _make_mock_response("<summary>x</summary>")
+
+    await _call_summary_model(
+        summary_model="claude-haiku-4-5",
+        summary_messages=[{"role": "user", "content": "hi"}],
+        metadata={},
+        llm_router=_FakeRouter(),
+        allowed_model_region="eu",
+    )
+
+    assert captured_kwargs.get("allowed_model_region") == "eu"
+
+
 # ---------------------------------------------------------------------------
 # Dispatcher integration: compact_20260112 via apply_context_management
 # ---------------------------------------------------------------------------