[BUG] Claude Desktop MCP prompts fail account-wide: "Failed to attach prompt"

Preflight Checklist

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

What's Wrong?

Environment:

• Platform: Claude Desktop (Windows)
• Claude Version: [check Help → About]
• MCP Server: BigQuery-Assets (npx q1x3nl4g)

Bug Description:
MCP prompts suddenly stopped working on [today's date] for my account only. 4 other test accounts work fine with identical configuration.

Symptoms:

• Error: "Failed to attach prompt. You can try again."
• MCP tools: ✅ Working perfectly
• MCP prompts: ❌ Failing
• MCP resources: ❌ Failing
• Tested on multiple computers: Same result
• Worked yesterday, broke today
• No code or config changes

What Should Happen?

Expected Behavior:
Prompts should attach and generate messages like they do for other accounts.

Actual Behavior:
Prompt attachment fails with generic error. Backend appears to be rejecting prompt requests for this specific account.

Additional Context:
This appears to be an account-level backend state corruption issue, as:

• Same MCP server works for other accounts
• Same computer works for other accounts
• Multiple computers fail for this account

Error Messages/Logs

- Failed to attach prompt. You can try again.
- Failed to attach resources. You can try again.

and here in Claude > logs > window:

2025-10-03 17:33:41 [error] Potential permissions policy violation: payment is not allowed in this document.
2025-10-03 17:33:43 [error] Potential permissions policy violation: payment is not allowed in this document.

Steps to Reproduce

1. Publish my MCP server to npm.
2. Called it in claude_desktop_config.

{
"mcpServers": {
"BigQuery-Assets": {
"command": "npx",
"args": [
"-y",
"server-name"
],
"env": {
"BIGQUERY_PROJECT": "My biguquery project",
"BIGQUERY_KEY_FILE": "path to service account key"
}
}
}

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

claude desktop latest version

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_