A Claude Code environment variable, read out of the shipped bundle.
It has been in the build since v2.1.187, including the newest one read.
Idle timeout in milliseconds for MCP tool calls. When a stdio, HTTP, SSE, WebSocket, or claude.ai connector 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
The earliest release whose published evidence quoted CLAUDE_CODE_MCP_TOOL_IDLE_TIMEOUT was v2.1.187, 23 Jun 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.
ReleaseDateThe span that was quoted
v2.1.18723 Jun 2026CLAUDE_CODE_MCP_TOOL_IDLE_TIMEOUT
v2.1.2905 Oct 2026set CLAUDE_CODE_MCP_TOOL_IDLE_TIMEOUT (ms) globally (0 disables).
Presence across releases
1
BuildsHow manyDatesReading
v2.1.187 – v2.1.308106 builds23 Jun 2026 → 22 Oct 2026 ◆in the build
Build by build
106
One 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.
