Fixes#50051 by preserving nested gateway.multiplex_profiles and routing gateway config env reads through the active profile secret scope when present.
This keeps secondary profile adapter startup from inheriting default-profile platform tokens or port-binding enables while preserving legacy single-profile behavior outside a scope.
Constraint: latest upstream main f57ff7aef1 still reproduced both nested-config loss and cross-profile env leakage
Rejected: special-casing API_SERVER_* only | left other profile-scoped tokens vulnerable to the same leak
Confidence: high
Scope-risk: moderate
Directive: keep future gateway/config env reads on the scoped helper path unless a variable is explicitly process-global
Tested: pytest -q tests/gateway/test_multiplex_phase0.py tests/gateway/test_multiplex_credential_isolation.py tests/gateway/test_config.py -k 'multiplex or scope or getenv or api_server or relay'
Not-tested: full gateway startup across live platform adapters
izumi0uu
0f154e780e