Claude Code Session Stopped Responding on Long MCP Tool Calls

What this error means

The session stopped responding. Send your message again to resume with a fresh process. is a Claude Code failure pattern reported for developers trying to fix claude code ui watchdog killing sessions on long-running synchronous mcp tool calls. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

Long-running synchronous MCP tool calls (>10-12 min) trigger UI watchdog with message ‘The session stopped responding. Send your message again to resume with a fresh process.’ Not an API timeout (API_TIMEOUT_MS=900000), but a UI-level health check. Reported May 12, 2026.

Common causes

• When a synchronous MCP tool call blocks Claude Code’s worker for ~10-15 minutes, the UI watchdog declares the session dead and shows ‘The session stopped responding’ — even though the MCP call may still be processing. This orphans MCP server processes and breaks long-running workflows.
• Long-running synchronous MCP tool calls (>10-12 min) trigger UI watchdog with message ‘The session stopped responding. Send your message again to resume with a fresh process.’ Not an API timeout (API_TIMEOUT_MS=900000), but a UI-level health check. Reported May 12, 2026.

Quick fixes

1. Confirm the exact error signature matches The session stopped responding. Send your message again to resume with a fresh process..
2. Check the Claude Code account, local tool state, and provider configuration involved in the failing workflow.
3. Compare the failing environment with a known working setup, then change one configuration value at a time.

Platform/tool-specific checks

• Verify the command, editor, extension, or API client that produced the error.
• Compare local settings with CI, deployment, or editor-level settings when the error appears in only one environment.
• Avoid deleting credentials, local model data, or project settings until the failing scope is clear.

Step-by-step troubleshooting

1. Capture the exact error message and the command, editor action, or request that triggered it.
2. Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
3. Review the source evidence below and compare it with your environment.
4. Apply one change at a time and rerun the smallest failing action.
5. Keep the working fix documented for the team or deployment environment.

How to prevent it

• Keep provider/tool configuration documented.
• Record non-secret diagnostics such as tool version, provider name, model name, and command path.
• Add a lightweight check before CI or production workflows depend on the tool.

Sources checked

• https://github.com/anthropics/claude-code/issues/58480

Evidence note: Long-running synchronous MCP tool calls (>10-12 min) trigger UI watchdog with message ‘The session stopped responding. Send your message again to resume with a fresh process.’ Not an API timeout (API_TIMEOUT_MS=900000), but a UI-level health check. Reported May 12, 2026.

Related errors

• Claude Code MCP tool call timeout configuration
• Claude Code orphaned MCP server processes

FAQ

What should I check first?

Start with the exact The session stopped responding. Send your message again to resume with a fresh process. text and the smallest action that reproduces it.

Can I ignore this error?

No. Treat it as a failed Claude Code workflow until the root cause is understood.

Is this guaranteed to have one fix?

No. The imported evidence supports the troubleshooting path above, but tool behavior can vary by account, plan, version, provider, and local configuration.

How do I know the fix worked?

Rerun the same command, editor action, or request. The fix is working when that action completes without The session stopped responding. Send your message again to resume with a fresh process..