CLAUDE_CODE_MCP_STARTUP_WAIT_MS
A Claude Code environment variable, read out of the shipped bundle. It has been in the build since v2.1.274, including the newest one read.
How long in milliseconds the first turn of a non-interactive session waits for MCP servers that are still connecting, in place of the default first-turn wait. When set, the wait covers every pending server. Set to 0 to skip the wait. A --permission-prompt-tool server keeps its own MCP_TIMEOUT wait regardless of the value. Requires Claude Code v2.1.274 or later
Anthropic's own wording. Read off Environment variables, captured 2026-09-28.
In the changelogs
3Releases whose published page names CLAUDE_CODE_MCP_STARTUP_WAIT_MS.
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v2.1.286
Relay workers wait for MCP servers when their relay is no longer usable
A relay-marked worker whose relay can no longer be used now makes its first command wait for MCP servers like an ordinary worker
found in this entry's text
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v2.1.284
Non-interactive runs wait for required MCP servers before the first turn
In
-pand SDK sessions, Claude Code now waits for MCP servers it deems required before the first turn, even when loading is deferredfound in this entry's text
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v2.1.274
New env var caps/controls MCP connector startup wait
New CLAUDE_CODE_MCP_STARTUP_WAIT_MS env var controls how long Claude Code waits for MCP servers to start
named in this entry, found in this entry's text
First cited
1The earliest release whose published evidence quoted CLAUDE_CODE_MCP_STARTUP_WAIT_MS was v2.1.274, 16 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
42One 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.