CLAUDE_CODE_MCP_APPS_HOST
A Claude Code environment variable, read out of the shipped bundle. It has been in the build since v2.1.281, including the newest one read.
With CLAUDE_CODE_MCP_APPS_HOST set to true, Claude Code tells MCP servers it accepts MCP App content
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.281.
In the changelogs
6Releases whose published page names CLAUDE_CODE_MCP_APPS_HOST.
-
v2.1.321
Three new environment variables for bridge and host integrations
Claude Code now passes CLAUDE_CODE_BRIDGE_CHILD_START_DIR, CLAUDE_CODE_BRIDGE_SETTINGS_BINDING and CLAUDE_CODE_NOTIFICATIONS_HOST to child processes
found in this entry's text
-
v2.1.307
Requests to the GitHub Copilot MCP server can carry an extra feature header
With CLAUDE_CODE_MCP_APPS_HOST set to true, Claude Code sends an X-MCP-Features header to the GitHub Copilot MCP server unless you already set one
found in this entry's text
-
v2.1.281
MCP Apps host capability advertised behind CLAUDE_CODE_MCP_APPS_HOST
With CLAUDE_CODE_MCP_APPS_HOST set to true, Claude Code tells MCP servers it accepts MCP App content
found in this entry's text, named in this entry
-
v2.1.281
New env vars CLAUDE_CODE_TETHER_LIVE and CLAUDE_CODE_MCP_APPS_HOST added to the protected env-key set
CLAUDE_CODE_TETHER_LIVE and CLAUDE_CODE_MCP_APPS_HOST join Claude Code's protected set of environment variables
found in this entry's text, named in this entry
-
v2.1.281
CLAUDE_CODE_MCP_APPS_HOST stripped from child env
Claude Code now removes
CLAUDE_CODE_MCP_APPS_HOSTfrom the environment of programs it startsfound in this entry's text, named in this entry
-
v2.1.281
MCP discovery cache now keyed on whether the MCP Apps host is enabled
The MCP discovery cache is now kept separately depending on whether the MCP Apps host is enabled
found in this entry's text, named in this entry
First cited
3The earliest release whose published evidence quoted CLAUDE_CODE_MCP_APPS_HOST was v2.1.281, 23 Sep 2026. That is the oldest release this project wrote about it, so it is a floor on the name's age and not the release that introduced it. It is not a presence reading: which builds carried the name is the table below.
Presence across releases
1Build by build
38One row per release since the first build this name was read out of. Absent means the build was read and the name was not in it, never mined means no bundle for that release was ever archived, and a declared type or a default is only ever what that release's own bundle stated.
Read out of the published npm bundle release by release, and out of Anthropic's own documentation as this site captured it. Nothing on this page is a description anybody here wrote about what the environment variable does. All environment variables.