CLAUDE_CODE_MCP_MEMORY_CGROUP
A Claude Code environment variable, read out of the shipped bundle. It has been in the build since v2.1.239, including the newest one read.
What it is
On Linux you can force MCP servers into their own memory cgroup with an environment variable.
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.239.
Presence across releases
| Releases | Reading | Declared type | Default |
|---|---|---|---|
| 2.1.245 – 2.1.250 5 releases | never mined | — | — |
| 2.1.239 – 2.1.243 5 releases | in the build | str | — |
A row reading never mined is a release with no archived bundle behind it. Nothing was read out of it, so nothing here says whether the name was in it. A declared type or a default is only ever what that release's own bundle stated.
Changelog entries naming it
-
v2.1.239MCP servers can be put in their own memory cgroup on Linux
On Linux you can force MCP servers into their own memory cgroup with an environment variable.
named in this entry
Documentation pages
None of Anthropic's documentation pages this site has a copy of carries this name.
Names beside it
Every environment variable in the inventory starting claude_code_mcp, up to twelve of them.
CLAUDE_CODE_MCP_ALLOWLIST_ENVSet to 1 to spawn stdio MCP servers with only a safe baseline environment plus the server's configured env, instead of inheriting your shell environment 2.1.138
CLAUDE_CODE_MCP_AUTO_BACKGROUND_MSElapsed time in milliseconds before a still-running MCP tool call [moves to a background task](/docs/en/mcp#automatic-backgrounding-of-long-tool-calls) (default: 120000, or 2 minutes). Set to 0 to turn automatic backgrounding off. Requires Claude Code v2.1.212 or later 2.1.198
CLAUDE_CODE_MCP_TOOL_IDLE_TIMEOUTIdle timeout in milliseconds for MCP tool calls. When a stdio, HTTP, SSE, WebSocket, or [claude.ai connector](/docs/en/mcp#use-mcp-servers-from-claude-ai) MCP server sends no response and no progress notification for this long, the tool call aborts with an error instead of waiting for the overall MCP_TOOL_TIMEOUT. Overrides the per-transport defaults of 300000 (5 minutes) for network servers and 1800000 (30 minutes) for stdio servers. Set to 0 to disable the idle check. Values below 1000 are raised to one second, and the value is capped at the effective MCP_TOOL_TIMEOUT. A per-server timeout in .mcp.json of at least 1000 raises that server's idle window to at least the timeout value. Doesn't apply to IDE servers or SDK in-process servers. Requires Claude Code v2.1.187 or later. Before v2.1.203, stdio servers were exempt from the idle timeout 2.1.187
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.