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n8n AI Agent node bug causes Anthropic Claude 400 errors

By PulseAugur Editorial · [1 sources] ·

A bug in n8n's AI Agent node, specifically the Tools Agent V3, causes a 400 error when interacting with Anthropic's Claude models. This error occurs when Claude generates a 'thinking' block followed by two or more 'tool_use' blocks in a single turn, leading to a signature mismatch. The issue arises because the agent rebuilds chat history, and replaying a thinking block with additional tool calls causes Anthropic to reject the request. Several fixes are available, ranging from quick workarounds to more surgical solutions, to address this intermittent problem. AI

IMPACT This bug can disrupt workflows relying on Anthropic's models via n8n, potentially causing intermittent failures in AI-powered agents.

RANK_REASON The item describes a bug fix for a specific software component (n8n AI Agent node) interacting with an AI model provider (Anthropic), rather than a new release or core research.

Read on dev.to — Anthropic tag →

AI-generated summary · Google Gemini · from 1 sources. How we write summaries →

n8n AI Agent node bug causes Anthropic Claude 400 errors

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The item describes a bug fix for a specific software component (n8n AI Agent node) interacting with an AI model provider (Anthropic), rather than a new release or core research.
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COVERAGE [1]

  1. dev.to — Anthropic tag TIER_1 English(EN) · CortexFlow ·

    Fix Anthropic 'Invalid signature in thinking block' 400 Error in n8n AI Agent (GH #41152)

    <p>Your support-ticket agent runs fine all morning, then randomly throws <code>Bad request - please check your parameters</code> on the AI Agent node. No credentials expired, nothing changed in the workflow, and re-running the same prompt sometimes works. Underneath that generic …

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