claude-code - 💡(How to fix) Fix [BUG] MCP server env block in ~/.claude.json not passed to spawned MCP servers inside Dev Container [1 comments, 2 participants]

Preflight Checklist

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

What's Wrong?

Environment Claude Code: 2.1.119 VS Code: 1.116.0 Dev Containers extension: 0.454.0 Host: macOS, Docker Desktop 4.67.0, image mcr.microsoft.com/devcontainers/go:1.25 Steps to reproduce On host, configure an MCP server in ~/.claude.json with an env block containing a credential, e.g.:

"mcpServers": { "codex": { "type": "stdio", "command": "codex", "args": ["mcp-server"], "env": { "OPENAI_API_KEY": "sk-proj-..." } } } Bind-mount ~/.claude.json into a Dev Container so Claude Code in the container reads the same file. Open a Claude session inside the container and call a tool routed through the codex MCP server. Expected The MCP server starts with OPENAI_API_KEY set in its environment (same behavior as host).

Actual The MCP server starts but the env var is empty. API calls fail with 401 Unauthorized — Missing bearer or basic authentication in header.

Verified manually in the container:

echo '{"jsonrpc":"2.0","id":1,"method":"initialize",...}'
| OPENAI_API_KEY="$KEY" codex mcp-server …returns a normal init response. So the codex binary honors env-var auth fine — Claude Code just isn't passing the configured env block.

Workaround Add the env var to the Dev Container's remoteEnv (e.g. "OPENAI_API_KEY": "${localEnv:OPENAI_API_KEY}") so it's set process-wide and inherited by the spawned MCP server.

What Should Happen?

The MCP server starts with OPENAI_API_KEY set in its environment (same behavior as host).

Error Messages/Logs

The MCP server starts but the env var is empty. API calls fail with 401 Unauthorized — Missing bearer or basic authentication in header.

Verified manually in the container:


echo '{"jsonrpc":"2.0","id":1,"method":"initialize",...}' \
  | OPENAI_API_KEY="$KEY" codex mcp-server
…returns a normal init response. So the codex binary honors env-var auth fine — Claude Code just isn't passing the configured env block.

Steps to Reproduce

On host, configure an MCP server in ~/.claude.json with an env block containing a credential, e.g.:

"mcpServers": { "codex": { "type": "stdio", "command": "codex", "args": ["mcp-server"], "env": { "OPENAI_API_KEY": "sk-proj-..." } } } Bind-mount ~/.claude.json into a Dev Container so Claude Code in the container reads the same file. Open a Claude session inside the container and call a tool routed through the codex MCP server.

Claude Model

None

Is this a regression?

I don't know

Last Working Version

No response

Claude Code Version

2.1.119

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Terminal.app (macOS)

Additional Information

No response