Backend Adapter Contract v1

Status: frozen for TKT-P3-39
Goal: keep wallet/covenant callers stable while allowing a real prover backend to replace the mock backend.

Scope

The adapter contract defines typed prove/verify requests and deterministic serialization surfaces.

Normative implementation:

• packages/zk-backend/src/adapter.ts
• packages/zk-backend/src/fixture_builder_v1.ts

Compatibility implementation:

• packages/zk-backend-mock/src/mock_backend_v1.ts

Typed contract

Public inputs:

• encoding = piv1_bytes
• piv1Bytes is the canonical PIv1 byte payload

Witness payload (optional):

• encoding = opaque_bytes_v1
• witnessBytes is backend-private and transport-neutral

Prove request:

• publicInputs
• optional proofSections (encryptedPayloadBytes, hintsBytes)
• optional witness
• optional determinism

Verify request:

• publicInputs
• pbv1Bytes
• optional witness

Benchmark report:

• optional proveMs, verifyMs, witnessBytes, proofBytes, proofBlobBytes, notes

Deterministic serialization

The adapter exports deterministic serializers for:

• prove request
• verify request
• benchmark report

These serializers are used for fixtures and regression checks so backend swaps do not silently drift byte-level request encoding.

Compatibility

• Legacy flat args remain accepted via normalizers.
• mockBackendV1 consumes both legacy and typed requests through the same adapter methods.
• Existing wallet/covenant call sites do not require API changes for this ticket.