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claude-code - 💡(How to fix) Fix [BUG] visualize:read_me and visualize:show_widget return 400 in Claude Desktop (Windows) and don’t register in tool context [1 participants]

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anthropics/claude-code#52598•Fetched 2026-04-24 06:02:51
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Error Message

400 error on both tool calls. Tools do not appear in tool_search results.

Error Messages/Logs

RAW_BUFFERClick to expand / collapse

Preflight Checklist

  • I have searched existing issues and this hasn't been reported yet
  • This is a single bug report (please file separate reports for different bugs)
  • I am using the latest version of Claude Code

What's Wrong?

Severity: Medium — feature completely non-functional Environment:

Client: Claude Desktop app (Windows) Plan: [your plan — /Max] App version: [Help → About] Date/time: April 23, 2026

What happened: Both visualize:read_me and visualize:show_widget tool calls return Tool call failed: 400 in every attempt within this session. Running tool_search for "visualize" returns no results, indicating the tools are not registering in the active tool context despite being defined in the system prompt. Steps to reproduce:

Open Claude Desktop Start a conversation in a Project with a large system prompt Ask Claude to render an inline HTML widget or diagram Claude calls visualize:read_me → returns Tool call failed: 400 Claude calls visualize:show_widget → returns Tool call failed: 400

Expected behavior: Inline rendered widget appears in chat, as it has worked previously in Claude Desktop. Actual behavior: 400 error on both tool calls. Tools do not appear in tool_search results. Additional context:

status.anthropic.com showed All Systems Operational at time of failure The issue appears session or project-specific — not a platform-wide outage Previously worked in Claude Desktop (user confirmed)

What Should Happen?

Claude should render inline editable HTML in the chat not on side pane that I can copy paste. IT USED TO WORK GREAT. SOMETHING BROKE IT

Error Messages/Logs

Steps to Reproduce

Just ask claude to generate a inline editable HTML for any content

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

No response

Claude Code Version

n/a this is on the claude desktop chat

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Terminal.app (macOS)

Additional Information

No response

extent analysis

TL;DR

The issue might be resolved by checking the system prompt definition and the active tool context to ensure the visualize tools are properly registered.

Guidance

  • Verify that the system prompt is correctly defined and the visualize tools are included in the prompt.
  • Check the active tool context to ensure the visualize tools are registered and available for use.
  • Try resetting the conversation or restarting the Claude Desktop app to see if the issue is session-specific.
  • Review the Anthropic API documentation to ensure the visualize:read_me and visualize:show_widget tool calls are correctly formatted and supported.

Notes

The issue appears to be specific to the Claude Desktop app on Windows and may be related to a regression in the Anthropic API or the Claude Code implementation.

Recommendation

Apply workaround: Try resetting the conversation or restarting the Claude Desktop app to see if the issue is session-specific, as the issue appears to be related to a specific project or session.

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claude-code - 💡(How to fix) Fix [BUG] visualize:read_me and visualize:show_widget return 400 in Claude Desktop (Windows) and don’t register in tool context [1 participants]