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fix(bedrock): remove remove_custom_field_from_tools — Bedrock now supports custom.defer_loading natively #26143

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fix(bedrock): remove remove_custom_field_from_tools — Bedrock now supports custom.defer_loading natively #26143

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02f3ecc
fix(bedrock): remove remove_custom_field_from_tools — Bedrock now sup…
Anai-Guo Apr 20, 2026
1aab5f7
fix(bedrock): remove remove_custom_field_from_tools call from message…
Anai-Guo Apr 20, 2026
342e1e7
fix(bedrock): remove remove_custom_field_from_tools call from chat tr…
Anai-Guo Apr 20, 2026
afe80d7
test(bedrock): remove test_remove_custom_field_from_tools — function …
Anai-Guo Apr 20, 2026
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3 changes: 0 additions & 3 deletions litellm/llms/bedrock/chat/invoke_transformations/anthropic_claude3_transformation.py
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,6 @@
from litellm.llms.bedrock.common_utils import (
get_anthropic_beta_from_headers,
normalize_tool_input_schema_types_for_bedrock_invoke,
remove_custom_field_from_tools,
)
from litellm.types.llms.anthropic import ANTHROPIC_TOOL_SEARCH_BETA_HEADER
from litellm.types.llms.openai import AllMessageValues
Expand Down Expand Up @@ -173,8 +172,6 @@ def _build_bedrock_anthropic_request_base(
if "anthropic_version" not in anthropic_request:
anthropic_request["anthropic_version"] = self.anthropic_version

# Remove `custom` field from tools (Bedrock doesn't support it)
remove_custom_field_from_tools(anthropic_request)
normalize_tool_input_schema_types_for_bedrock_invoke(anthropic_request)
return anthropic_request

Expand Down
21 changes: 0 additions & 21 deletions litellm/llms/bedrock/common_utils.py
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Original file line number Diff line number Diff line change
Expand Up @@ -49,27 +49,6 @@ def get_cached_model_info():
return _get_model_info


def remove_custom_field_from_tools(request_body: dict) -> None:
"""
Remove ``custom`` field from each tool in the request body.

Claude Code (v2.1.69+) sends ``custom: {defer_loading: true}`` on tool
definitions, which Anthropic's API accepts but Bedrock rejects with
``"Extra inputs are not permitted"``.

Args:
request_body: The request dictionary to modify in-place.

Ref: https://github.com/BerriAI/litellm/issues/22847
"""
tools = request_body.get("tools")
if not tools or not isinstance(tools, list):
return
for tool in tools:
if isinstance(tool, dict):
tool.pop("custom", None)


def normalize_json_schema_custom_types_to_object(schema: dict) -> None:
"""
In-place: replace JSON Schema ``type: \"custom\"`` with ``\"object\"`` (iterative walk).
Expand Down
6 changes: 0 additions & 6 deletions litellm/llms/bedrock/messages/invoke_transformations/anthropic_claude3_transformation.py
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Original file line number Diff line number Diff line change
Expand Up @@ -31,7 +31,6 @@
get_anthropic_beta_from_headers,
is_claude_4_5_on_bedrock,
normalize_tool_input_schema_types_for_bedrock_invoke,
remove_custom_field_from_tools,
)
from litellm.types.llms.anthropic import ANTHROPIC_TOOL_SEARCH_BETA_HEADER
from litellm.types.llms.openai import AllMessageValues
Expand Down Expand Up @@ -504,11 +503,6 @@ def transform_anthropic_messages_request(
# Fixes: https://github.com/BerriAI/litellm/issues/22797
anthropic_messages_request.pop("output_config", None)

# 5a. Remove `custom` field from tools (Bedrock doesn't support it)
# Claude Code sends `custom: {defer_loading: true}` on tool definitions,
# which causes Bedrock to reject the request with "Extra inputs are not permitted"
# Ref: https://github.com/BerriAI/litellm/issues/22847
remove_custom_field_from_tools(anthropic_messages_request)
normalize_tool_input_schema_types_for_bedrock_invoke(anthropic_messages_request)
ensure_bedrock_anthropic_messages_tool_names(anthropic_messages_request)

Expand Down
55 changes: 0 additions & 55 deletions ...llm/llms/bedrock/messages/invoke_transformations/test_anthropic_claude3_transformation.py
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,6 @@
from litellm.llms.bedrock.common_utils import (
ensure_bedrock_anthropic_messages_tool_names,
normalize_tool_input_schema_types_for_bedrock_invoke,
remove_custom_field_from_tools,
)
from litellm.constants import BEDROCK_MIN_THINKING_BUDGET_TOKENS
from litellm.llms.bedrock.messages.invoke_transformations.anthropic_claude3_transformation import (
Expand Down Expand Up @@ -246,60 +245,6 @@ def test_remove_ttl_from_cache_control():
request5 = {}
cfg._remove_ttl_from_cache_control(request5)
assert request5 == {}


def test_remove_custom_field_from_tools():
"""
Ensure the `custom` field is stripped from every tool definition.

Claude Code v2.1.69+ sends `custom: {defer_loading: true}` on tool
objects. Bedrock does not accept this extra field and returns
"Extra inputs are not permitted".

Ref: https://github.com/BerriAI/litellm/issues/22847
"""

# Case 1: tool with `custom` field should have it removed
request = {
"tools": [
{
"name": "Read",
"description": "Read a file",
"input_schema": {"type": "object", "properties": {}},
"custom": {"defer_loading": True},
},
{
"name": "Write",
"description": "Write a file",
"input_schema": {"type": "object", "properties": {}},
},
]
}

remove_custom_field_from_tools(request)

for tool in request["tools"]:
assert "custom" not in tool, f"Tool {tool['name']} still has 'custom' field"
# Other fields should be preserved
assert request["tools"][0]["name"] == "Read"
assert request["tools"][1]["name"] == "Write"

# Case 2: request without tools key (should not raise error)
request2 = {"messages": [{"role": "user", "content": "hi"}]}
remove_custom_field_from_tools(request2)
assert "tools" not in request2

# Case 3: empty tools list (should not raise error)
request3 = {"tools": []}
remove_custom_field_from_tools(request3)
assert request3["tools"] == []

# Case 4: tools with None value (should not raise error)
request4 = {"tools": None}
remove_custom_field_from_tools(request4)
assert request4["tools"] is None


def test_normalize_tool_input_schema_types_for_bedrock_invoke():
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@greptile-apps greptile-apps Bot Apr 20, 2026

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P2 Missing test for preserved custom field passthrough

The deleted test verified that custom fields were stripped; now that the stripping is removed, there is no corresponding test verifying that custom: {defer_loading: true} is actually preserved (not dropped) in the final Bedrock request body. A regression here (e.g., a future developer re-adding the strip or an upstream transform clearing it) would go undetected. Consider adding a test asserting the custom field survives the full transformation pipeline alongside test_normalize_tool_input_schema_types_for_bedrock_invoke.

"""
Claude Code sends ``input_schema.type: \"custom\"`` for custom tools.
Expand Down