fix(bedrock): sanitize tool_use IDs in pass-through messages

Bedrock requires tool_use IDs to match ^[a-zA-Z0-9_-]+$ but the
Anthropic native API allows broader characters. When clients like
Claude Code send requests through the /v1/messages pass-through
endpoint, IDs containing dots, plus signs, or other special characters
cause Bedrock to return 400 Bad Request errors.

Added _sanitize_tool_use_ids() to AmazonAnthropicClaudeMessagesConfig
that replaces invalid characters with underscores in both tool_use.id
and tool_result.tool_use_id fields during Bedrock-specific request
transformation.

Fixes #21114

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

litellm/llms/bedrock/messages/invoke_transformations/anthropic_claude3_transformation.py

@@ -1,3 +1,4 @@
+import re
 from typing import (
     TYPE_CHECKING,
     Any,
@@ -372,6 +373,49 @@ class AmazonAnthropicClaudeMessagesConfig(
         schema_text = {"type": "text", "text": json.dumps(schema)}
         content.append(schema_text)
 
+
+    _VALID_TOOL_ID_PATTERN = re.compile(r"^[a-zA-Z0-9_-]+$")
+    _INVALID_TOOL_ID_CHARS = re.compile(r"[^a-zA-Z0-9_-]")
+
+    def _sanitize_tool_use_ids(
+        self, anthropic_messages_request: Dict
+    ) -> None:
+        """
+        Sanitize tool_use IDs to match Bedrock's required pattern.
+
+        Bedrock requires tool_use IDs to match ``^[a-zA-Z0-9_-]+$`` but the
+        Anthropic native API allows broader characters. Clients like Claude Code
+        send requests through the pass-through endpoint with IDs that Bedrock
+        rejects with 400 Bad Request.
+
+        Replaces any invalid characters with underscores in both ``tool_use.id``
+        and ``tool_result.tool_use_id`` fields.
+
+        Fixes: https://github.com/BerriAI/litellm/issues/21114
+        """
+        messages = anthropic_messages_request.get("messages")
+        if not isinstance(messages, list):
+            return
+
+        for message in messages:
+            if not isinstance(message, dict):
+                continue
+            content = message.get("content")
+            if not isinstance(content, list):
+                continue
+            for block in content:
+                if not isinstance(block, dict):
+                    continue
+                block_type = block.get("type")
+                if block_type == "tool_use" and "id" in block:
+                    tool_id = block["id"]
+                    if isinstance(tool_id, str) and not self._VALID_TOOL_ID_PATTERN.match(tool_id):
+                        block["id"] = self._INVALID_TOOL_ID_CHARS.sub("_", tool_id)
+                elif block_type == "tool_result" and "tool_use_id" in block:
+                    tool_use_id = block["tool_use_id"]
+                    if isinstance(tool_use_id, str) and not self._VALID_TOOL_ID_PATTERN.match(tool_use_id):
+                        block["tool_use_id"] = self._INVALID_TOOL_ID_CHARS.sub("_", tool_use_id)
+
     def transform_anthropic_messages_request(
         self,
         model: str,
@@ -429,6 +473,12 @@ class AmazonAnthropicClaudeMessagesConfig(
         # Ref: https://github.com/BerriAI/litellm/issues/22847
         remove_custom_field_from_tools(anthropic_messages_request)
 
+        # 7. Sanitize tool_use IDs (Bedrock requires ^[a-zA-Z0-9_-]+$)
+        # The Anthropic native API allows broader characters in tool_use IDs,
+        # but Bedrock rejects them with 400 Bad Request.
+        # Fixes: https://github.com/BerriAI/litellm/issues/21114
+        self._sanitize_tool_use_ids(anthropic_messages_request)
+
         # 6. AUTO-INJECT beta headers based on features used
         anthropic_model_info = AnthropicModelInfo()
         tools = anthropic_messages_optional_request_params.get("tools")

tests/test_litellm/llms/bedrock/messages/invoke_transformations/test_anthropic_claude3_transformation.py

@@ -342,3 +342,139 @@ def test_bedrock_messages_strips_output_config_with_output_format():
 
     assert "output_config" not in result
     assert "output_format" not in result
+
+
+class TestSanitizeToolUseIds:
+    """Tests for _sanitize_tool_use_ids in AmazonAnthropicClaudeMessagesConfig.
+
+    Bedrock requires tool_use IDs to match ^[a-zA-Z0-9_-]+$ but the Anthropic
+    native API allows broader characters.
+    Fixes: https://github.com/BerriAI/litellm/issues/21114
+    """
+
+    def test_sanitize_tool_use_id_with_invalid_chars(self):
+        """tool_use.id with invalid characters should be sanitized."""
+        cfg = AmazonAnthropicClaudeMessagesConfig()
+        request = {
+            "messages": [
+                {
+                    "role": "assistant",
+                    "content": [
+                        {
+                            "type": "tool_use",
+                            "id": "toolu_abc.123+xyz/foo",
+                            "name": "test_tool",
+                            "input": {},
+                        }
+                    ],
+                }
+            ]
+        }
+        cfg._sanitize_tool_use_ids(request)
+        assert request["messages"][0]["content"][0]["id"] == "toolu_abc_123_xyz_foo"
+
+    def test_sanitize_tool_result_id_with_invalid_chars(self):
+        """tool_result.tool_use_id with invalid characters should be sanitized."""
+        cfg = AmazonAnthropicClaudeMessagesConfig()
+        request = {
+            "messages": [
+                {
+                    "role": "user",
+                    "content": [
+                        {
+                            "type": "tool_result",
+                            "tool_use_id": "toolu_abc.123+xyz/foo",
+                            "content": "result",
+                        }
+                    ],
+                }
+            ]
+        }
+        cfg._sanitize_tool_use_ids(request)
+        assert (
+            request["messages"][0]["content"][0]["tool_use_id"]
+            == "toolu_abc_123_xyz_foo"
+        )
+
+    def test_valid_ids_unchanged(self):
+        """IDs that already match the Bedrock pattern should not be modified."""
+        cfg = AmazonAnthropicClaudeMessagesConfig()
+        request = {
+            "messages": [
+                {
+                    "role": "assistant",
+                    "content": [
+                        {
+                            "type": "tool_use",
+                            "id": "toolu_valid-id_123",
+                            "name": "test_tool",
+                            "input": {},
+                        }
+                    ],
+                },
+                {
+                    "role": "user",
+                    "content": [
+                        {
+                            "type": "tool_result",
+                            "tool_use_id": "toolu_valid-id_123",
+                            "content": "result",
+                        }
+                    ],
+                },
+            ]
+        }
+        cfg._sanitize_tool_use_ids(request)
+        assert request["messages"][0]["content"][0]["id"] == "toolu_valid-id_123"
+        assert (
+            request["messages"][1]["content"][0]["tool_use_id"] == "toolu_valid-id_123"
+        )
+
+    def test_no_messages_key(self):
+        """Should handle request without messages key gracefully."""
+        cfg = AmazonAnthropicClaudeMessagesConfig()
+        request = {"max_tokens": 1024}
+        cfg._sanitize_tool_use_ids(request)  # Should not raise
+
+    def test_string_content_ignored(self):
+        """Messages with string content (not list) should be skipped."""
+        cfg = AmazonAnthropicClaudeMessagesConfig()
+        request = {
+            "messages": [{"role": "user", "content": "hello"}]
+        }
+        cfg._sanitize_tool_use_ids(request)  # Should not raise
+
+    def test_consistent_sanitization_across_pairs(self):
+        """tool_use.id and matching tool_result.tool_use_id should sanitize identically."""
+        cfg = AmazonAnthropicClaudeMessagesConfig()
+        original_id = "toolu_01A.B+C/D:E"
+        request = {
+            "messages": [
+                {
+                    "role": "assistant",
+                    "content": [
+                        {
+                            "type": "tool_use",
+                            "id": original_id,
+                            "name": "test",
+                            "input": {},
+                        }
+                    ],
+                },
+                {
+                    "role": "user",
+                    "content": [
+                        {
+                            "type": "tool_result",
+                            "tool_use_id": original_id,
+                            "content": "result",
+                        }
+                    ],
+                },
+            ]
+        }
+        cfg._sanitize_tool_use_ids(request)
+        sanitized_tool_use = request["messages"][0]["content"][0]["id"]
+        sanitized_tool_result = request["messages"][1]["content"][0]["tool_use_id"]
+        assert sanitized_tool_use == sanitized_tool_result
+        assert sanitized_tool_use == "toolu_01A_B_C_D_E"