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Project	Deployment	Actions	Updated (UTC)
litellm	Ready	Preview, Comment	Mar 5, 2026 9:55pm

Greptile Summary

This PR fixes a regression where Claude Code v2.1.69+ began sending a custom: {defer_loading: true} field on tool definitions. Anthropic's own API accepts this field, but AWS Bedrock rejects it with "Extra inputs are not permitted", causing ~90 % of proxied requests to fail. The fix introduces a small utility remove_custom_field_from_tools() in common_utils.py and calls it in both Bedrock invoke code paths (Chat API and Messages API) immediately before the request body is dispatched to Bedrock.

• litellm/llms/bedrock/common_utils.py — new remove_custom_field_from_tools() strips the top-level custom key from every tool dict in-place; handles None, empty list, and non-list values safely.
• litellm/llms/bedrock/messages/invoke_transformations/anthropic_claude3_transformation.py — step 5a calls the utility after output_format conversion, before beta-header injection; feature-detection (tool_search_used, etc.) correctly continues to read from anthropic_messages_optional_request_params, which is unaffected.
• litellm/llms/bedrock/chat/invoke_transformations/anthropic_claude3_transformation.py — mirrors the messages path; strip happens after model/stream/output_format pops; beta-header feature-detection reads from optional_params, also unaffected.
• Tests — four unit cases for the utility function (happy path, missing key, empty list, None); no network calls, consistent with the mock-only test policy for this directory.

Minor observations:

• A missing blank line exists between test_remove_custom_field_from_tools and test_remove_scope_from_cache_control in the test file (PEP 8 / ruff E302).
• There is no integration-level test for the chat invoke path (AmazonAnthropicClaudeConfig.transform_request) with a custom-bearing tool; only the messages path and the isolated utility are tested.

Confidence Score: 4/5

• Safe to merge; the fix is targeted, non-breaking, and well-tested for the core utility and messages path.
• The change is small and surgical — it only removes a field that Bedrock actively rejects today. Both critical Bedrock invoke paths are covered. The utility handles all edge cases correctly. The only gaps are a missing blank line in the test file and the absence of a chat-path integration test, neither of which affects correctness.
• litellm/llms/bedrock/chat/invoke_transformations/anthropic_claude3_transformation.py — no dedicated test exercises this code path end-to-end with a custom-bearing tool.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Incoming request\nwith tools incl. custom field] --> B{Bedrock invoke path?}
    B -- Chat API --> C[AmazonAnthropicClaudeConfig\n.transform_request]
    B -- Messages API --> D[AmazonAnthropicClaudeMessagesConfig\n.transform_request]
    C --> E[AnthropicConfig.transform_request\nbuilds _anthropic_request]
    E --> F[pop model / stream / output_format]
    F --> G[remove_custom_field_from_tools\n_anthropic_request]
    D --> H[AnthropicMessagesConfig.transform_request\nbuilds anthropic_messages_request]
    H --> I[pop stream / model]
    I --> J[_remove_ttl_from_cache_control]
    J --> K[_convert_output_format_to_inline_schema]
    K --> L[remove_custom_field_from_tools\nanthropic_messages_request]
    G --> M[Beta-header injection\nreads from optional_params — unaffected]
    L --> N[Beta-header injection\nreads from optional_request_params — unaffected]
    M --> O[Request sent to Bedrock\nno custom field → 200 OK]
    N --> O

_{Last reviewed commit: dedc50d}