Unclear It is not fully settled that CLAUDE_CODE_MCP_APPS_HOST is the setting that controls whether the header is sent.
MCP (Model Context Protocol) is the standard Claude Code uses to connect to outside servers that give it extra tools. When Claude Code connects to an MCP server at api.githubcopilot.com, it can now add a header to its requests. A header is a short labelled piece of information sent along with each request. This header is X-MCP-Features: mcp_apps_disable_form_deferral.
Claude Code adds this header only when both of these are true:
CLAUDE_CODE_MCP_APPS_HOSTis set totruein your environment.- You have not already set your own
x-mcp-featuresheader for that server. Capital and lowercase letters in the name are treated the same.
Previously Claude Code sent only the default headers and the headers you configured.
This changes what one particular third-party MCP server receives from Claude Code. If you configure your own x-mcp-features header for that server, Claude Code keeps your value and does not add its own.
It is not fully settled that `CLAUDE_CODE_MCP_APPS_HOST` is the setting that controls whether the header is sent.