Claude Code / AI Coding Tools
Claude Code MCP proxy returns -32600 Invalid content from server on session-404
Fix MCP proxy -32600 invalid content error in Claude Code when session expires or server returns unexpected response Includes evidence for Claude Code troubleshooting demand.
- Category
- AI Coding Tools
- Error signature
MCP proxy surfaces `-32600 "Invalid content from server"` instead of reinitializing on session-404- Quick fix
- Compare the failing environment with a known working setup, then change one configuration value at a time.
- Updated
What this error means
MCP proxy surfaces -32600 “Invalid content from server” instead of reinitializing on session-404 is a Claude Code failure pattern reported for developers trying to fix mcp proxy -32600 invalid content error in claude code when session expires or server returns unexpected response. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.
Why this happens
GitHub issue anthropics/claude-code#59410 (2026-05-15) reports MCP proxy returning -32600 JSON-RPC error on session-404 instead of gracefully reinitializing. Bug with has-repro label. Category mapping: Claude Code MCP errors → AI Coding Tools.
Common causes
- GitHub issue anthropics/claude-code#59410 (2026-05-15) reports MCP proxy returning -32600 JSON-RPC error on session-404 instead of gracefully reinitializing. Bug with has-repro label. Category mapping: Claude Code MCP errors → AI Coding Tools.
Quick fixes
- Confirm the exact error signature matches
MCP proxy surfaces-32600 “Invalid content from server”instead of reinitializing on session-404. - Check the Claude Code account, local tool state, and provider configuration involved in the failing workflow.
- 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
- Capture the exact error message and the command, editor action, or request that triggered it.
- Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
- Review the source evidence below and compare it with your environment.
- Apply one change at a time and rerun the smallest failing action.
- 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
Evidence note: GitHub issue anthropics/claude-code#59410 (2026-05-15) reports MCP proxy returning -32600 JSON-RPC error on session-404 instead of gracefully reinitializing. Bug with has-repro label. Category mapping: Claude Code MCP errors → AI Coding Tools.
Related errors
- AI Coding Tools
FAQ
What should I check first?
Start with the exact MCP proxy surfaces -32600 “Invalid content from server” instead of reinitializing on session-404 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 MCP proxy surfaces -32600 “Invalid content from server” instead of reinitializing on session-404.