claude.ai MCP Servers Enabled by Default / Claude Code v2.1.63

The claude.ai MCP server integration has changed from opt-in to enabled by default (still GrowthBook-gated for rollout). Users who previously had to set ENABLE_CLAUDEAI_MCP_SERVERS=true no longer need to. To opt out, set ENABLE_CLAUDEAI_MCP_SERVERS=false.

Evidence

Changed message from "require ENABLE_CLAUDEAI_MCP_SERVERS=true" (v2.1.62) to "enabled by default (GrowthBook-gated). To opt out, set ENABLE_CLAUDEAI_MCP_SERVERS=false" (v2.1.63)

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

How sure we are

One source agreesOne thing we can check says the same as this entry.

Anthropic's release notes agreeAdded ENABLE_CLAUDEAI_MCP_SERVERS=false env var to opt out from making claude.ai MCP servers available

See this entry in the whole of v2.1.63 →

The build it came inv2.1.63

28 Feb 2026 · 25 entries, this one is #10.

Either side of it

v2.1.62Older
v2.1.64Newer

Open the release →

Names in this entry

envENABLE_CLAUDEAI_MCP_SERVERS
Eval sandboxes force claude.ai MCP servers off so they can't reach real servers.

Anthropic's note

Upstream's own release notes for v2.1.63 name something this entry names, so the two are probably about the same change. Probably: the pairing is made on a shared name rather than on the words around it.

Added ENABLE_CLAUDEAI_MCP_SERVERS=false env var to opt out from making claude.ai MCP servers available

Is this right?