CLAUDE_CODE_MCP_AUTO_BACKGROUND_MS

Updated October 13, 2026 by Alex Sorokoletov

CLAUDE_CODE_MCP_AUTO_BACKGROUND_MS is a Claude Code environment variable. Added between v2.1.143 and v2.1.212 and still present in v2.1.294. It is listed in the official reference.

Status	Present in v2.1.294
Added	Added between v2.1.143 and v2.1.212
Category	MCP
Official docs	Listed

How to set it

For one session, export it in the shell that starts Claude Code:

export CLAUDE_CODE_MCP_AUTO_BACKGROUND_MS=<value>
claude

To apply it to every session, add it to the env object of a settings file:

// ~/.claude/settings.json
{
  "env": {
    "CLAUDE_CODE_MCP_AUTO_BACKGROUND_MS": "<value>"
  }
}

Release notes that mention it

Related variables

CLAUDE_CODE_DISABLE_MCP_TASK_BACKGROUND
CLAUDE_CODE_ENABLE_REFRESH_MCP_TOOLS: Enables an on-demand MCP-tool refresh capability, grouped with CLAUDE_CODE_ENABLE_TASKS and CLAUDE_CODE_ENABLE_REMOTE_RECAP.
CLAUDE_CODE_MAX_MCP_DESCRIPTION_LENGTH
CLAUDE_CODE_MCP_ALLOWLIST_ENV: Specifies an allowlist of environment variables that MCP servers can access.
CLAUDE_CODE_MCP_INSTR_DELTA: Delta/incremental MCP instruction updates.
CLAUDE_CODE_MCP_SERVER_NAME: Added in v2.1.85 to identify which MCP server a helper process was acting on behalf of.
CLAUDE_CODE_MCP_STARTUP_WAIT_MS
ENABLE_CLAUDEAI_MCP_SERVERS: Enable Claude.ai-hosted MCP servers.

Frequently asked questions

Which Claude Code version has CLAUDE_CODE_MCP_AUTO_BACKGROUND_MS?

Added between v2.1.143 and v2.1.212 and still present in v2.1.294.

How do I set CLAUDE_CODE_MCP_AUTO_BACKGROUND_MS?

Export it before starting Claude Code (export CLAUDE_CODE_MCP_AUTO_BACKGROUND_MS=value), or add it to the "env" object in ~/.claude/settings.json to apply it to every session.

All variables, searchable: Claude Code environment variables.