fix(anthropic): sanitize tool_use ids on native /v1/messages path

litellm/llms/anthropic/common_utils.py

@@ -3,6 +3,7 @@
 """
 
 import copy
+import re
 from typing import Any, Dict, List, Optional, Union
 
 import httpx
@@ -11,6 +12,9 @@
 from litellm.litellm_core_utils.prompt_templates.common_utils import (
     get_file_ids_from_messages,
 )
+from litellm.litellm_core_utils.prompt_templates.factory import (
+    THOUGHT_SIGNATURE_SEPARATOR,
+)
 from litellm.llms.base_llm.base_utils import BaseLLMModelInfo, BaseTokenCounter
 from litellm.llms.base_llm.chat.transformation import BaseLLMException
 from litellm.types.llms.anthropic import (
@@ -999,6 +1003,67 @@ def _is_empty_text_block(block: Any) -> bool:
     return not isinstance(text, str) or not text.strip()
 
 
+def normalize_anthropic_tool_use_id(raw_id: str) -> str:
+    """
+    Normalize a tool_use / tool_result id for Anthropic's ``^[a-zA-Z0-9_-]+$``
+    pattern.
+
+    Strips Gemini thought-signature suffixes (``__thought__``) first, then
+    replaces any remaining invalid characters with underscores.
+    """
+    base_id = (
+        raw_id.split(THOUGHT_SIGNATURE_SEPARATOR, 1)[0]
+        if THOUGHT_SIGNATURE_SEPARATOR in raw_id
+        else raw_id
+    )
+    sanitized = re.sub(r"[^a-zA-Z0-9_-]", "_", base_id)
+    return sanitized or "tool_use_id"
+
+
+def _sanitize_tool_use_id_content_block(block: Any) -> Any:
+    if not isinstance(block, dict):
+        return block
+    block_type = block.get("type")
+    if block_type in ("tool_use", "server_tool_use"):
+        raw_id = block.get("id")
+        if isinstance(raw_id, str):
+            normalized = normalize_anthropic_tool_use_id(raw_id)
+            if normalized != raw_id:
+                return {**block, "id": normalized}
+    elif block_type == "tool_result":
+        raw_id = block.get("tool_use_id")
+        if isinstance(raw_id, str):
+            normalized = normalize_anthropic_tool_use_id(raw_id)
+            if normalized != raw_id:
+                return {**block, "tool_use_id": normalized}
+    return block
+
+
+def sanitize_tool_use_ids_in_anthropic_messages(messages: list[Any]) -> list[Any]:
+    """
+    Return a new message list with ``tool_use`` / ``server_tool_use`` ``id`` and
+    ``tool_result`` ``tool_use_id`` values rewritten to satisfy Anthropic's
+    ``^[a-zA-Z0-9_-]+$`` requirement.
+
+    Cross-provider clients (e.g. Claude Code routed through kimi) may replay
+    conversation history containing ids like ``functions.Bash:0`` with ``.``
+    and ``:`` — valid on the upstream provider but rejected by Anthropic when
+    the session is switched to a native Anthropic deployment.
+    """
+    out: list[Any] = []
+    for m in messages:
+        if not isinstance(m, dict) or not isinstance(m.get("content"), list):
+            out.append(m)
+            continue
+        content = m["content"]
+        new_content = [_sanitize_tool_use_id_content_block(b) for b in content]
+        if new_content == content:
+            out.append(m)
+        else:
+            out.append({**m, "content": new_content})
+    return out
+
+
 def process_anthropic_headers(headers: Union[httpx.Headers, dict]) -> dict:
     openai_headers = {}
     if "anthropic-ratelimit-requests-limit" in headers:

litellm/llms/anthropic/experimental_pass_through/adapters/transformation.py

@@ -76,6 +76,7 @@ def create_tool_name_mapping(
 from litellm.litellm_core_utils.prompt_templates.factory import (
     THOUGHT_SIGNATURE_SEPARATOR,
 )
+from litellm.llms.anthropic.common_utils import normalize_anthropic_tool_use_id
 from litellm.llms.anthropic.experimental_pass_through.context_management import (
     PolyfillResult,
 )
@@ -1363,18 +1364,12 @@ def _translate_openai_content_to_anthropic(
                         else truncated_name
                     )
 
-                    # Strip Gemini thought-signature suffix from id (mirrors streaming
-                    # path below); base64 chars (+ / =) violate Anthropic's
-                    # `^[a-zA-Z0-9_-]+$` tool_use.id pattern when replayed.
+                    # Strip Gemini thought-signature suffix and normalize id chars
+                    # (e.g. ``functions.Bash:0`` from cross-provider clients).
                     raw_id = tool_call.id or ""
-                    base_id = (
-                        raw_id.split(THOUGHT_SIGNATURE_SEPARATOR, 1)[0]
-                        if THOUGHT_SIGNATURE_SEPARATOR in raw_id
-                        else raw_id
-                    )
                     tool_use_block = AnthropicResponseContentBlockToolUse(
                         type="tool_use",
-                        id=base_id,
+                        id=normalize_anthropic_tool_use_id(raw_id),
                         name=original_name,
                         input=parse_tool_call_arguments(
                             tool_call.function.arguments,
@@ -1501,15 +1496,13 @@ def _translate_streaming_openai_chunk_to_anthropic_content_block(
             ):
                 raw_id = choice.delta.tool_calls[0].id or str(uuid.uuid4())
                 tool_name = choice.delta.tool_calls[0].function.name or ""
-                base_id = raw_id
                 thought_sig: Optional[str] = None
                 if THOUGHT_SIGNATURE_SEPARATOR in raw_id:
                     parts = raw_id.split(THOUGHT_SIGNATURE_SEPARATOR, 1)
-                    base_id = parts[0]
                     thought_sig = parts[1] if len(parts) > 1 else None
                 tool_block: Dict[str, Any] = {
                     "type": "tool_use",
-                    "id": base_id,
+                    "id": normalize_anthropic_tool_use_id(raw_id),
                     "name": tool_name,
                     "input": {},
                 }

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

@@ -23,6 +23,7 @@
 import litellm
 from litellm.litellm_core_utils.litellm_logging import Logging as LiteLLMLoggingObj
 from litellm.llms.anthropic.common_utils import (
+    sanitize_tool_use_ids_in_anthropic_messages,
     strip_empty_text_blocks_from_anthropic_messages,
 )
 from litellm.llms.base_llm.anthropic_messages.transformation import (
@@ -214,6 +215,9 @@ async def anthropic_messages(
     # already handles this in anthropic_messages_pt; sanitize the native
     # Anthropic Messages path here for the same guarantee.  See #22930.
     messages = strip_empty_text_blocks_from_anthropic_messages(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)
 
     original_stream = stream or kwargs.get(
         "_websearch_interception_converted_stream", False
@@ -397,6 +401,7 @@ def anthropic_messages_handler(
     # full-messages scan. Pop it so it never leaks into provider params.
     if not kwargs.pop("_litellm_messages_presanitized", False):
         messages = strip_empty_text_blocks_from_anthropic_messages(messages)
+        messages = sanitize_tool_use_ids_in_anthropic_messages(messages)
 
     metadata = validate_anthropic_api_metadata(metadata)
 

tests/test_litellm/llms/anthropic/experimental_pass_through/adapters/test_anthropic_experimental_pass_through_adapters_transformation.py

@@ -508,6 +508,35 @@ def test_translate_openai_content_to_anthropic_strips_gemini_thought_from_tool_c
     assert result[0]["input"] == {"location": "Boston"}
 
 
+def test_translate_openai_content_to_anthropic_sanitizes_colon_dot_tool_call_ids():
+    """Cross-provider ids like ``functions.Bash:0`` must be normalized for Anthropic replay."""
+    openai_choices = [
+        Choices(
+            message=Message(
+                role="assistant",
+                content=None,
+                tool_calls=[
+                    ChatCompletionAssistantToolCall(
+                        id="functions.Bash:0",
+                        type="function",
+                        function=Function(
+                            name="Bash",
+                            arguments='{"command": "ls"}',
+                        ),
+                    )
+                ],
+            )
+        )
+    ]
+
+    adapter = LiteLLMAnthropicMessagesAdapter()
+    result = adapter._translate_openai_content_to_anthropic(choices=openai_choices)
+
+    assert len(result) == 1
+    assert result[0]["type"] == "tool_use"
+    assert result[0]["id"] == "functions_Bash_0"
+
+
 def test_translate_openai_response_to_anthropic_text_and_tool_calls():
     """`translate_openai_response_to_anthropic` should surface assistant text even when tools fire."""
     openai_response = ModelResponse(

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

@@ -105,6 +105,48 @@ def fake_handler(*args, **kwargs):
     assert len(msgs[0]["content"]) == 2  # caller untouched
 
 
+@pytest.mark.asyncio
+async def test_anthropic_messages_sanitizes_tool_use_ids_before_dispatch():
+    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="anthropic/claude-sonnet-4-5-20250929",
+            custom_llm_provider="anthropic",
+            api_key="k",
+        )
+
+    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

@@ -1329,6 +1329,52 @@ def test_strip_empty_text_blocks_treats_non_string_text_value_as_empty(self):
         out = strip_empty_text_blocks_from_anthropic_messages(msgs)
         assert [b["type"] for b in out[0]["content"]] == ["tool_result"]
 
+    def test_sanitize_tool_use_ids_in_anthropic_messages(self):
+        from litellm.llms.anthropic.common_utils import (
+            sanitize_tool_use_ids_in_anthropic_messages,
+        )
+
+        msgs = [
+            {
+                "role": "assistant",
+                "content": [
+                    {
+                        "type": "tool_use",
+                        "id": "functions.Bash:0",
+                        "name": "Bash",
+                        "input": {},
+                    }
+                ],
+            },
+            {
+                "role": "user",
+                "content": [
+                    {
+                        "type": "tool_result",
+                        "tool_use_id": "functions.Bash:0",
+                        "content": "ok",
+                    }
+                ],
+            },
+        ]
+        out = sanitize_tool_use_ids_in_anthropic_messages(msgs)
+        assert out[0]["content"][0]["id"] == "functions_Bash_0"
+        assert out[1]["content"][0]["tool_use_id"] == "functions_Bash_0"
+        assert msgs[0]["content"][0]["id"] == "functions.Bash:0"
+
+    def test_normalize_anthropic_tool_use_id_strips_thought_signature(self):
+        from litellm.litellm_core_utils.prompt_templates.factory import (
+            THOUGHT_SIGNATURE_SEPARATOR,
+        )
+        from litellm.llms.anthropic.common_utils import normalize_anthropic_tool_use_id
+
+        base = "call_abc123"
+        sig = "CiIBDDnWx+/a=="
+        assert (
+            normalize_anthropic_tool_use_id(f"{base}{THOUGHT_SIGNATURE_SEPARATOR}{sig}")
+            == base
+        )
+
     def test_anthropic_messages_config_http_retry_helpers(self):
         import httpx