[BUG] claude mcp add doesn't work with environment variables for stdio transport

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?

When you try to add a new MCP server (stdio transport) with an environment variable, you get this error:

Invalid environment variable format: my-server, environment variables should be added as: -e KEY1=value1 -e KEY2=value2

Even when running the default stdio examples (from claude mcp add --help):

claude mcp add -e API_KEY=xxx my-server -- npx my-mcp-server

So it looks like something is broken.

What Should Happen?

The MCP server should be added, without errors related to environment variables.

Error Messages/Logs

Invalid environment variable format: my-server, environment variables should be added as: -e KEY1=value1 -e KEY2=value2

Steps to Reproduce

Run the default claude mcp add example:

claude mcp add -e API_KEY=xxx my-server -- npx my-mcp-server

It seems something changed between v2.0.77 and v2.1.0.

The pattern went from

claude mcp add --transport stdio airtable --env AIRTABLE_API_KEY=YOUR_KEY -- npx -y airtable-mcp-server

to

claude mcp add --transport stdio --env AIRTABLE_API_KEY=YOUR_KEY airtable -- npx -y airtable-mcp-server

but I couldn't find a single version that worked with this new pattern.

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

v2.0.77

Claude Code Version

2.1.31

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

It's currently not possible to add a new MCP server with stdio transport and an environment variable (even using the default CLI examples). Please prioritize this issue because it's probably affecting a lot of MCP servers 🙏