Under the hood
A no-op false value was added to the API client's custom-header spread, with no apparent effect
What
Where the client's default headers previously spread in only one extra source (the ANTHROPIC_CUSTOM_HEADERS-derived anthropic-beta values), the code now also spreads a literal false value immediately before it.
Why
Spreading a boolean false into an object has no effect, so this appears to be an inert change with no impact on the headers Claude Code sends.