Ownership boundaries

SDK-Rust owns

• generic primitives and domain values;
• reusable cryptographic operations and bounded representations;
• protocol-neutral ports and validation contracts;
• conformance and compatibility evidence attached to those surfaces.

Chain and identity repositories own

• DID method semantics and operation construction;
• ledger clients, indexing, submission, synchronization, and finality;
• Compact contracts, proving systems, and chain-native cryptosuites;
• chain deployment and operational policy.

Wallet and application products own

• key custody, secure storage, consent, account recovery, and authorization;
• trust decisions, credential selection, user experience, and telemetry;
• backend deployment, availability, privacy, and regulatory controls;
• the decision to adopt an SDK revision or release.

An SDK abstraction is reusable only when these product and chain decisions can remain outside it.