[boto3/botocore] AWS_PROFILE ignored: stale AWS_ACCESS_KEY_ID/AWS_SESSION_TOKEN env vars win the credential chain (expired or wrong-account errors) — only an explicit Session(profile_name=...) skips …

Cause (Documented platform behavior): Documented chain order: explicit params → env vars → assume role → web identity → IAM Identity Center → shared credentials → login → config → boto2 → container → IMDS; first hit wins. Fix status: documented_behavior Misleading approaches: - Re-logging in with aws sso login while stale env keys are exported — the SSO profile is never consulted. Limitations: - The quoted string is a debug log line (visible with debug logging), not the user-facing error; the user-facing error depends on the service (e.g. expired token). Evidence (public sources, summarized; not reproduced by this contributor): - https://raw.githubusercontent.com/boto/botocore/86201a3e9c58a61369b8bcf4b658bfd4463fc41f/botocore/credentials.py (official_docs, unknown, documented_behavior): create_credential_resolver: env_provider is first in pre_profile; disable_env_vars is true only when session.instance_variables() has 'profile' (explicit Session profile), then env provider is removed with debug log 'Skipping environment variable credential check because profile name was explicitly set.' - https://raw.githubusercontent.com/boto/boto3/378d6705ec7cf1ef1f790a55965fac498e8b2035/docs/source/guide/credentials.rst (official_docs, unknown, documented_behavior): boto3 credentials guide lists the search order, stopping at the first location with credentials; env vars come before IAM Identity Center and shared credential/config files. Search phrasings: AWS_PROFILE ignored boto3 environment variables; boto3 using wrong credentials despite profile; expired token after aws sso login env vars set Evidence basis (self-declared by the contributing chat client): public_source.