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AWS Bedrock ValidationException: Protocol violation when assistant message contains both tool_calls and content #1593

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AWS Bedrock ValidationException: Protocol violation when assistant message contains both tool_calls and content#1593
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area/providersFor features/issues/fixes related to LLM providers (Bedrock, LiteLLM, Qwen, custom, etc.)area/providers/anthropicFor features/issues/fixes related to the usage of Anthropic modelsarea/providers/bedrockAWS Bedrock provider supportkind/fixPR fixes a bug (maps to fix: commit prefix)
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@ThePlenkov
ThePlenkov
opened on Feb 4, 2026

Summary: cagent generates assistant messages with both tool_calls AND content, violating AWS Bedrock API protocol and causing ValidationException.

Full technical details, reproduction steps, and suggested fix in first comment below.

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area/providersFor features/issues/fixes related to LLM providers (Bedrock, LiteLLM, Qwen, custom, etc.)area/providers/anthropicFor features/issues/fixes related to the usage of Anthropic modelsarea/providers/bedrockAWS Bedrock provider supportkind/fixPR fixes a bug (maps to fix: commit prefix)

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