4563940792
User decision: save, Test Connect, live browse and the deploy gate keep refusing out-of-namespace credential references, but an ALREADY-DEPLOYED driver must not fault at the upgrade restart or (Galaxy) at the next gateway reconnect, since ReopenAsync re-resolves Gateway.ApiKeySecretRef. - LegacyCredentialReferenceTracker (Core.Abstractions): the one, deprecated, call-site-chosen compatibility path. Running Galaxy (InitializeAsync, ReopenAsync, ack fallback) and OpcUaClient (session open) pass it and keep the pre-#815 semantics (case-insensitive prefixes, Galaxy file:, OpcUaClient literal pass-through) with a rate-limited Warning (driver/field/allowed form, never the value) and a credential-compat:<field> diagnostics entry (both drivers now implement IDriverDiagnostics). Browsers and probes pass none and stay hard-fail; Heidenhain has none. - Deploy-gate message names the migration. - Upgrade preflight: CredentialReferencePreflightService (admin nodes, once after ApplicationStarted, ConfigDb only, resolves nothing) logs a Warning per Draft row / Deployed-artifact finding; the /raw banner shows them plus Running drivers reporting warn-only use (driver-health diagnostics). - docs/security.md: exact replacement table (incl. the old form default env:MX_API_KEY, file:, un-namespaced secret:, casing changes), the ReopenAsync reconnect behaviour, the warn-only window and its removal. Co-Authored-By: Claude <noreply@anthropic.com>