fix(anthropic): support Claude 4.x models and mixed-content tool calls#1500
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ming-hsien wants to merge 1 commit into
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fix(anthropic): support Claude 4.x models and mixed-content tool calls#1500ming-hsien wants to merge 1 commit into
ming-hsien wants to merge 1 commit into
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- Add omitempty to temperature field in messagePayload and MessageRequest so that unset temperature (0.0) is not serialized into the request body. Claude 4.x models (e.g. claude-opus-4-7) have deprecated the temperature parameter and return HTTP 400 when it is present. - Rewrite handleAIMessage to iterate over all Parts instead of only Parts[0]. When Claude returns a response containing both a text block and tool_use blocks, processAnthropicResponse produces one ContentChoice per block. The caller reassembles them into a single MessageContent with mixed Parts (TextContent followed by ToolCall). The original implementation only inspected Parts[0], so ToolCall entries were silently dropped from the assistant message written to history. On the next turn Anthropic rejected the request with "tool_result block has no corresponding tool_use block".
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Problem
Two bugs that prevent langchaingo from working correctly with Claude 4.x models (e.g.
claude-opus-4-7,claude-sonnet-4-6):1.
temperaturefield causes HTTP 400 on Claude 4.xmessagePayloadandMessageRequestboth declareTemperature float64 \json:"temperature"`withoutomitempty. This means every API request serializes"temperature": 0even when the caller never set a temperature. Claude 4.x models have deprecated thetemperature` parameter and return:400: temperature is deprecated for this model.
2. Mixed text + tool_use responses break conversation history
When Claude returns a response that contains both a text block and one or more
tool_useblocks,processAnthropicResponsecorrectly produces oneContentChoiceper content block. However,handleAIMessageonly inspectedParts[0]of the reassembledMessageContent. If the first part wasTextContent, all subsequentToolCallparts were silently dropped when writing the assistant message back to history.On the next turn, the
tool_resultblock referenced atool_useID that no longer existed in the assistant message, causing Anthropic to reject the request with:400: Each tool_result block must have a corresponding tool_use block in the previous message.
Fix
omitemptytoTemperatureinmessagePayloadandMessageRequestso the field is omitted when not explicitly set.handleAIMessageto iterate over allPartsinstead of onlyParts[0], correctly emitting bothtextandtool_usecontent blocks in a single assistant message.Tested with
claude-opus-4-7claude-sonnet-4-6