fix(anthropic): resolve tool-id sanitize provider from model prefix

azure_ai/claude-sonnet-4-5 and github_copilot/claude-sonnet-4-5 with only
api_base set were treated as anthropic pass-through and skipped the rewrite.

Read the provider from custom_llm_provider, else the model prefix. Do not call
get_llm_provider (github_copilot that path prompts device login).

litellm/llms/anthropic/common_utils.py

@@ -1244,12 +1244,30 @@ def _sanitize_tool_use_id_content_block(block: object) -> object:
 _ANTHROPIC_TOOL_ID_CHARSET_HOSTNAME: Final = "api.anthropic.com"
 
 
+def _llm_provider_for_tool_id_sanitize(
+    *,
+    custom_llm_provider: str | None,
+    model: str | None,
+) -> str | None:
+    if custom_llm_provider is not None and custom_llm_provider.strip():
+        return custom_llm_provider.casefold()
+    if model is None or "/" not in model:
+        return None
+    prefix: Final = model.split("/", 1)[0].casefold()
+    return prefix or None
+
+
 def _should_sanitize_anthropic_tool_use_ids(
     *,
     api_base: str | None,
     custom_llm_provider: str | None,
+    model: str | None,
 ) -> bool:
-    if custom_llm_provider is not None and custom_llm_provider.casefold() != "anthropic":
+    provider: Final = _llm_provider_for_tool_id_sanitize(
+        custom_llm_provider=custom_llm_provider,
+        model=model,
+    )
+    if provider is not None and provider != "anthropic":
         return True
     if api_base is None or not api_base.strip():
         return True
@@ -1264,18 +1282,20 @@ def sanitize_tool_use_ids_in_anthropic_messages(
     *,
     api_base: str | None = None,
     custom_llm_provider: str | None = None,
+    model: str | None = None,
 ) -> list[Any]:
     """
     Rewrite ``tool_use`` / ``server_tool_use`` ``id`` and ``tool_result``
     ``tool_use_id`` values to Anthropic's ``^[a-zA-Z0-9_-]+$`` pattern.
 
-    No-op when ``custom_llm_provider`` is ``anthropic`` and ``api_base`` is a
+    No-op when the resolved provider is ``anthropic`` and ``api_base`` is a
     non-Anthropic host. vLLM/Kimi echo the original ids; rewriting them breaks
     the next tool_result turn. See #32214.
     """
     if not _should_sanitize_anthropic_tool_use_ids(
         api_base=api_base,
         custom_llm_provider=custom_llm_provider,
+        model=model,
     ):
         return messages
     out: Final[list[Any]] = []

litellm/llms/anthropic/experimental_pass_through/messages/handler.py

@@ -264,7 +264,10 @@ async def anthropic_messages(
     # Replay of cross-provider tool history (e.g. kimi -> Anthropic) may carry
     # ids like ``functions.Bash:0`` that violate Anthropic's id pattern.
     messages = sanitize_tool_use_ids_in_anthropic_messages(
-        messages, api_base=api_base, custom_llm_provider=custom_llm_provider
+        messages,
+        api_base=api_base,
+        custom_llm_provider=custom_llm_provider,
+        model=model,
     )
     messages = flatten_unencrypted_web_search_results_in_anthropic_messages(messages)
 
@@ -463,7 +466,10 @@ def anthropic_messages_handler(
     if not kwargs.pop("_litellm_messages_presanitized", False):
         messages = strip_empty_content_blocks_from_anthropic_messages(messages)
         messages = sanitize_tool_use_ids_in_anthropic_messages(
-            messages, api_base=api_base, custom_llm_provider=custom_llm_provider
+            messages,
+            api_base=api_base,
+            custom_llm_provider=custom_llm_provider,
+            model=model,
         )
         messages = flatten_unencrypted_web_search_results_in_anthropic_messages(messages)
 

tests/test_litellm/llms/anthropic/experimental_pass_through/messages/test_anthropic_experimental_pass_through_messages_handler.py

@@ -263,6 +263,48 @@ async def test_anthropic_messages_keeps_tool_use_ids_for_non_anthropic_api_base(
     assert msgs[0]["content"][0]["id"] == "functions.Bash:0"
 
 
+@pytest.mark.asyncio
+async def test_anthropic_messages_sanitizes_azure_ai_model_prefix_without_provider():
+    from litellm.llms.anthropic.experimental_pass_through.messages import handler
+
+    msgs = [
+        {
+            "role": "assistant",
+            "content": [
+                {
+                    "type": "tool_use",
+                    "id": "functions.Bash:0",
+                    "name": "Bash",
+                    "input": {},
+                }
+            ],
+        }
+    ]
+    captured = {}
+
+    def fake_handler(*args, **kwargs):
+        captured["messages"] = kwargs.get("messages")
+        return "stub"
+
+    fake_loop = MagicMock()
+    fake_loop.run_in_executor = lambda _e, func: _async_return(func())
+
+    with (
+        patch.object(handler, "anthropic_messages_handler", side_effect=fake_handler),
+        patch("asyncio.get_event_loop", return_value=fake_loop),
+    ):
+        await handler.anthropic_messages(
+            max_tokens=100,
+            messages=msgs,
+            model="azure_ai/claude-sonnet-4-5",
+            api_key="k",
+            api_base="https://myres.services.ai.azure.com/anthropic",
+        )
+
+    assert captured["messages"][0]["content"][0]["id"] == "functions_Bash_0"
+    assert msgs[0]["content"][0]["id"] == "functions.Bash:0"
+
+
 async def _async_return(value):
     return value
 

tests/test_litellm/llms/anthropic/test_anthropic_common_utils.py

@@ -1874,18 +1874,23 @@ class TestAnthropicThinkingSignatureSelfHeal:
             }
         ]
         still_sanitize = (
-            ("anthropic", ""),
-            ("anthropic", "https://api.anthropic.com"),
-            ("azure_ai", "https://myres.services.ai.azure.com/anthropic"),
-            ("github_copilot", "https://api.githubcopilot.com"),
-            ("bedrock", "https://bedrock-runtime.us-east-1.amazonaws.com"),
-            ("vertex_ai", "https://us-east5-aiplatform.googleapis.com"),
+            ("anthropic", "", None),
+            ("anthropic", "https://api.anthropic.com", None),
+            ("azure_ai", "https://myres.services.ai.azure.com/anthropic", None),
+            ("github_copilot", "https://api.githubcopilot.com", None),
+            ("bedrock", "https://bedrock-runtime.us-east-1.amazonaws.com", None),
+            ("vertex_ai", "https://us-east5-aiplatform.googleapis.com", None),
+            (None, "https://myres.services.ai.azure.com/anthropic", "azure_ai/claude-sonnet-4-5"),
+            (None, "https://api.githubcopilot.com", "github_copilot/claude-sonnet-4-5"),
         )
-        for custom_llm_provider, api_base in still_sanitize:
+        for custom_llm_provider, api_base, model in still_sanitize:
             out = sanitize_tool_use_ids_in_anthropic_messages(
-                msgs, api_base=api_base, custom_llm_provider=custom_llm_provider
+                msgs,
+                api_base=api_base,
+                custom_llm_provider=custom_llm_provider,
+                model=model,
             )
-            assert out[0]["content"][0]["id"] == "functions_Bash_0", (custom_llm_provider, api_base)
+            assert out[0]["content"][0]["id"] == "functions_Bash_0", (custom_llm_provider, api_base, model)
             assert msgs[0]["content"][0]["id"] == "functions.Bash:0"
 
     def test_normalize_anthropic_tool_use_id_strips_thought_signature(self):