SAGEMAKER_REGION, SAGEMAKER_ACCESS_KEY and SAGEMAKER_SECRET_KEY survive
only as a fallback for the S3_* credentials. They carry
Field(deprecated=...) now, so any read emits a DeprecationWarning naming
the replacement and the generated reference shows the notice. The S3
store is the one sanctioned reader; it silences that warning locally
because it already logs its own operator-facing one when the fallback
is actually used.
DEFAULT_MAX_HISTORY was referenced nowhere. RETRIEVERS_ENABLED was read by
no code at all, while two docs pages described it as an enforced
allow-list; both the setting and those claims are removed.
arc53-machine