CLAUDE_CODE_MCP_ALLOWLIST_ENV
Updated by Alex Sorokoletov
CLAUDE_CODE_MCP_ALLOWLIST_ENV is a Claude Code environment variable: Specifies an allowlist of environment variables that MCP servers can access. MCP servers run as subprocesses and inherit the parent environment by default, which is a security concern — API keys, database credentials, and cloud tokens all leak into every MCP server process. Added in v2.1.94 and still present in v2.1.294. It is listed in the official reference.
| Status | Present in v2.1.294 |
|---|---|
| Added | Added in v2.1.94 |
| 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_ALLOWLIST_ENV=<value>
claudeTo apply it to every session, add it to the env object of a settings file:
// ~/.claude/settings.json
{
"env": {
"CLAUDE_CODE_MCP_ALLOWLIST_ENV": "<value>"
}
}Release notes that mention it
- Claude Code v2.1.94 — 5 New Environment Variables: Mantle Authentication, MCP Sandboxing, and Team Onboarding
- Claude Code Version Tracker: Undocumented Env Vars, Feature Gates & Models
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_LENGTHCLAUDE_CODE_MCP_AUTO_BACKGROUND_MSCLAUDE_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_MSENABLE_CLAUDEAI_MCP_SERVERS: Enable Claude.ai-hosted MCP servers.ENABLE_MCP_LARGE_OUTPUT_FILES: Enable large output files for MCP.
Frequently asked questions
What does CLAUDE_CODE_MCP_ALLOWLIST_ENV do?
Specifies an allowlist of environment variables that MCP servers can access. MCP servers run as subprocesses and inherit the parent environment by default, which is a security concern — API keys, database credentials, and cloud tokens all leak into every MCP server process.
Which Claude Code version has CLAUDE_CODE_MCP_ALLOWLIST_ENV?
Added in v2.1.94 and still present in v2.1.294.
How do I set CLAUDE_CODE_MCP_ALLOWLIST_ENV?
Export it before starting Claude Code (export CLAUDE_CODE_MCP_ALLOWLIST_ENV=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.