Design notes

These pages preserve implementation plans, migrations, and known product gaps. They are contributor context, not stable user-facing contracts.

• OAuth provider identity changes — current gap and target behavior for enforcing a stable provider account during reauthentication.
• Unified key-model migration — migration history, data model, provider behavior, and implementation sequencing for logical keys and data-encryption keys.

Stable behavior belongs in the public concept, integration, operations, or security guides. Move a design note into those sections only after the behavior has shipped and the page has been rewritten as user documentation.