Under the hoodTier: how much it should matter to you
1Useful: my rating, 1 to 5
2Signal: worth watching, 1 to 5
ElsewhereArea: what it touches
Internal ChangesKind: in v2.1.267,
Internal ChangesSection of the release
Unclear The finding doesn't say which beta names are on the new exclusion list or why they're excluded.
What
When Claude Code builds its list of beta headers from the ANTHROPIC_BETAS environment variable (used to opt into experimental Anthropic API features), each entry is now also checked against a new exclusion list. Entries that match are dropped, on top of the existing trimming of blank entries.
Why
Some beta names can now be blocked outright from being applied via ANTHROPIC_BETAS, regardless of what the user sets, beyond the earlier org-compliance-based blocking of the whole variable.
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
Confirmed sinceAnthropic's documentation has since written up ANTHROPIC_BETAS, on Claude Code gateway compatibility guide.* Header values and body fields developers add themselves through [`ANTHROPIC_BETAS`](/docs/en/env-vars) or [`CLAUDE_CODE_EXTRA_BODY`](/docs/en/env-vars)llm-gateway-protocolsee the edit
How sure we are
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubtThe finding doesn't say which beta names are on the new exclusion list or why they're excluded.
Anthropic's documentation agreesAnthropic's documentation has since written up ANTHROPIC_BETAS, on Claude Code gateway compatibility guide.
