Claude Code VSCode Shows 'Unhandled case: [object Object]' for All MCP Errors

What this error means

Claude Code VSCode v2.1.141 renders 'Unhandled case: [object Object]' instead of MCP server error messages is a Claude Code failure pattern reported for developers trying to fix claude code vscode extension showing [object object] instead of actual error messages. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

v2.1.141 exhaustiveness handler in webview/index.js QB1() function throws with object instead of string. Affects MCP servers: excalidraw, github, W&B, Figma connectors. Multiple duplicate reports.

Common causes

• v2.1.141 regression in the webview exhaustiveness handler. When any MCP server fails to start (misconfigured path, missing env var, OAuth error), the UI shows ‘Unhandled case: [object Object]’ instead of the actual error. Affects all MCP configurations.
• v2.1.141 exhaustiveness handler in webview/index.js QB1() function throws with object instead of string. Affects MCP servers: excalidraw, github, W&B, Figma connectors. Multiple duplicate reports.

Quick fixes

1. Confirm the exact error signature matches Claude Code VSCode v2.1.141 renders 'Unhandled case: [object Object]' instead of MCP server error messages.
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/59188
• https://github.com/anthropics/claude-code/issues/59207

Evidence note: v2.1.141 exhaustiveness handler in webview/index.js QB1() function throws with object instead of string. Affects MCP servers: excalidraw, github, W&B, Figma connectors. Multiple duplicate reports.

Related errors

• Claude Code MCP server connection failed
• Claude Code plugin load error
• Claude Code webview crash

FAQ

What should I check first?

Start with the exact Claude Code VSCode v2.1.141 renders 'Unhandled case: [object Object]' instead of MCP server error messages 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 Claude Code VSCode v2.1.141 renders 'Unhandled case: [object Object]' instead of MCP server error messages.