MCP_SDK_GENERATION

Updated October 13, 2026 by Alex Sorokoletov

MCP_SDK_GENERATION is a Claude Code environment variable. Its release history is not tracked here. It is listed in the official reference.

Status	Present in v2.1.294
Category	MCP
Official docs	Listed

How to set it

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

export MCP_SDK_GENERATION=<value>
claude

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

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

Related variables

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_AUTO_BACKGROUND_MS
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 MCP_SDK_GENERATION?

Its release history is not tracked here.

How do I set MCP_SDK_GENERATION?

Export it before starting Claude Code (export MCP_SDK_GENERATION=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.