CLAUDE_CODE_MCP_ALWAYS_LOAD_JOIN_BEFORE_INPUT
A Claude Code environment variable, read out of the shipped bundle. It has been in the build since v2.1.299, including the newest one read.
A new environment variable, CLAUDE_CODE_MCP_ALWAYS_LOAD_JOIN_BEFORE_INPUT, affects always-load MCP servers when set to exactly true
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.299.
In the changelogs
3Releases whose published page names CLAUDE_CODE_MCP_ALWAYS_LOAD_JOIN_BEFORE_INPUT.
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v2.1.299
New setting for always-load MCP servers at startup
A new environment variable,
CLAUDE_CODE_MCP_ALWAYS_LOAD_JOIN_BEFORE_INPUT, affects always-load MCP servers when set to exactlytruefound in this entry's text, named in this entry
-
v2.1.299
Five more environment variables are passed on to remote sessions
Five new Claude Code environment variables are now on the list passed to remote sessions, with no other use in this build
found in this entry's text
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v2.1.299
Five new environment variables passed through to remote sessions
Five new CLAUDE_CODE_* environment variables now appear on the lists of settings passed through to remote (CCR) sessions
found in this entry's text
First cited
1The earliest release whose published evidence quoted CLAUDE_CODE_MCP_ALWAYS_LOAD_JOIN_BEFORE_INPUT was v2.1.299, 14 Oct 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
10One 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.