fix(anthropic): filter Converse body betas, keep Foundry auto betas, read the bundled beta config for row checks

litellm/anthropic_beta_headers_manager.py

@@ -242,7 +242,10 @@ def get_provider_name(provider: str) -> str:
 
 
 def has_beta_headers_config(provider: str) -> bool:
-    return get_provider_name(provider) in _load_beta_headers_config()
+    config: Final = _bundled_beta_headers_config()
+    aliases: Final = config.get("provider_aliases", {})
+    canonical_provider: Final = (aliases.get(provider) if isinstance(aliases, Mapping) else None) or provider
+    return canonical_provider in config
 
 
 def filter_and_transform_beta_headers(

litellm/llms/azure_ai/anthropic/transformation.py

@@ -110,7 +110,8 @@ class AzureAnthropicConfig(AnthropicConfig):
             thinking=optional_params.get("thinking"),  # pyright: ignore[reportUnknownMemberType, reportUnknownArgumentType]  # optional_params is the base config's bare dict
         )
         # Merge headers - Azure auth (api-key or Authorization) takes precedence
-        headers = {**anthropic_headers, **headers}
+        merged_beta_header: Final = {k: v for k, v in anthropic_headers.items() if k == "anthropic-beta"}
+        headers = {**anthropic_headers, **headers, **merged_beta_header}
 
         # Ensure anthropic-version header is set
         if "anthropic-version" not in headers:

litellm/llms/bedrock/chat/converse_transformation.py

@@ -18,6 +18,7 @@ from typing_extensions import ReadOnly, TypedDict
 import litellm
 from litellm._logging import verbose_logger
 from litellm.anthropic_beta_gated_fields import active_beta_values, log_beta_gated_strips, strip_beta_gated_thinking
+from litellm.anthropic_beta_headers_manager import filter_and_transform_beta_headers
 from litellm.constants import (
     BEDROCK_MIN_THINKING_BUDGET_TOKENS,
     RESPONSE_FORMAT_TOOL_NAME,
@@ -1830,11 +1831,14 @@ class AmazonConverseConfig(BaseConfig):
 
         base_model: Final = BedrockModelInfo.get_base_model(model)
         header_beta_list: Final = get_anthropic_beta_from_headers(headers or {})
-        client_beta_list: Final = header_beta_list or sorted(
-            active_beta_values(
-                {},
-                additional_request_params.get("anthropic_beta"),  # pyright: ignore[reportUnknownMemberType, reportUnknownArgumentType]  # additional_request_params is a bare dict
-            )
+        client_beta_list: Final = header_beta_list or filter_and_transform_beta_headers(
+            sorted(
+                active_beta_values(
+                    {},
+                    additional_request_params.get("anthropic_beta"),  # pyright: ignore[reportUnknownMemberType, reportUnknownArgumentType]  # additional_request_params is a bare dict
+                )
+            ),
+            provider="bedrock_converse",
         )
         eager_beta: Final = (
             (ANTHROPIC_FINE_GRAINED_TOOL_STREAMING_BETA_HEADER,)

tests/unit/llms/anthropic/messages/native/test_anthropic_messages_transformation.py

@@ -7,9 +7,11 @@ from unittest.mock import patch
 
 import httpx
 import pytest
+import respx
 from pydantic import JsonValue
 
 import litellm
+from litellm import anthropic_beta_headers_manager
 from litellm.litellm_core_utils.litellm_logging import Logging
 from litellm.llms.anthropic.messages.native.transformation import (
     AnthropicMessagesConfig,
@@ -521,3 +523,29 @@ def test_a_provider_without_a_beta_headers_row_forwards_beta_gated_fields_under_
     )
     assert request["thinking"] == thinking
     assert request["messages"][-1]["output_config"] == {"effort": "low"}
+
+
+def test_a_first_party_messages_request_never_fetches_the_remote_beta_headers_config(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    monkeypatch.delenv("LITELLM_LOCAL_ANTHROPIC_BETA_HEADERS", raising=False)
+    monkeypatch.setattr(anthropic_beta_headers_manager, "_BETA_HEADERS_CONFIG", None)
+
+    with respx.mock(assert_all_called=False) as router:
+        remote_config: Final = router.get(litellm.anthropic_beta_headers_url).mock(
+            return_value=httpx.Response(200, json={})
+        )
+        request: Final = AnthropicMessagesConfig().transform_anthropic_messages_request(
+            model="claude-opus-4-8",
+            messages=[
+                {"role": "user", "content": "hi"},
+                {"role": "system", "content": "be terse", "clear_at": "end_turn"},
+                {"role": "user", "content": "go"},
+            ],
+            anthropic_messages_optional_request_params={"max_tokens": 64},
+            litellm_params=GenericLiteLLMParams(drop_params=True),
+            headers={},
+        )
+
+    assert request["messages"][1] == {"role": "system", "content": "be terse"}
+    assert not remote_config.called

tests/unit/llms/azure_ai/claude/test_azure_anthropic_handler.py

@@ -310,3 +310,34 @@ def test_completion_adds_the_binding_beta_so_block_binding_is_kept(
     sent: Final = json.loads(route.calls.last.request.content)
     assert sent["thinking"] == {"type": "enabled", "budget_tokens": 1024, "block_binding": block_binding}
     assert "thinking-binding-controls-2026-08-01" in route.calls.last.request.headers["anthropic-beta"].split(",")
+
+
+@respx.mock
+def test_completion_sends_the_binding_beta_next_to_the_callers_own_betas(local_beta_headers_config: None) -> None:
+    route: Final = respx.post("https://example-resource.services.ai.azure.com/anthropic/v1/messages").mock(
+        return_value=Response(
+            200,
+            json={
+                "id": "msg_bound",
+                "type": "message",
+                "role": "assistant",
+                "model": "claude-sonnet-4-6",
+                "content": [{"type": "text", "text": "Hello"}],
+                "stop_reason": "end_turn",
+                "stop_sequence": None,
+                "usage": {"input_tokens": 1, "output_tokens": 1},
+            },
+        )
+    )
+
+    litellm.completion(
+        model="azure_ai/claude-sonnet-4-6",
+        messages=[{"role": "user", "content": "hi"}],
+        api_base="https://example-resource.services.ai.azure.com/anthropic",
+        api_key="azure-test-key",
+        thinking={"type": "enabled", "budget_tokens": 1024, "block_binding": {"prefix_mismatch_behavior": "error"}},
+        extra_headers={"anthropic-beta": "context-1m-2025-08-07"},
+    )
+
+    sent_betas: Final = set(route.calls.last.request.headers["anthropic-beta"].split(","))
+    assert {"context-1m-2025-08-07", "thinking-binding-controls-2026-08-01"} <= sent_betas

tests/unit/llms/bedrock/chat/test_converse_transformation.py

@@ -10884,6 +10884,19 @@ def test_converse_keeps_beta_gated_thinking_fields_the_body_anthropic_beta_carri
     }
 
 
+def test_converse_drops_body_betas_the_bedrock_converse_row_rejects_when_adding_thinking_betas(
+    local_beta_headers_config: None,
+) -> None:
+    fields: Final = _converse_bound_thinking_request(
+        None, body_betas=("per-turn-control-2026-07-01", "context-1m-2025-08-07")
+    )
+    assert sorted(fields["anthropic_beta"]) == [
+        "context-1m-2025-08-07",
+        "thinking-binding-controls-2026-08-01",
+        "thinking-display-updates-2026-08-18",
+    ]
+
+
 def test_converse_sends_only_the_header_betas_when_header_and_body_both_carry_betas(
     monkeypatch: pytest.MonkeyPatch,
 ) -> None: