The internal function that checks whether a user is on a first-party provider (Anthropic direct, Anthropic AWS, or Foundry) was split into two: a pure provider check and a combined provider-plus-env-var check. Two code paths were updated to use the provider-only check, meaning:
One specific SDK beta flag (used in API request construction) is now always included for first-party provider sessions, even when CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS=1 is set.
The SDK beta filter function, which decides whether to pass all beta strings through or restrict to a known set, now passes all betas for first-party providers regardless of the env var.
Other uses of CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS (e.g., gating thinking summaries, context management beta, tool schema betas) remain unchanged and continue to respect the environment variable.
Evidence
Provider check refactoring — an8() at line ~148770 no longer includes CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS; new bp() at line ~148774 preserves the old combined behavior for other call sites (search for "CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS")
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 agreeFixed OAuth authentication failing with a 401 retry loop when CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS=1 is set
