Appendix: Interoperability Matrix (CAIP & x402 v2)

This appendix documents the practical interoperability posture for NanoSession Rev 6:

• what is implemented now for x402 v2 wire compatibility,
• what third-party adapters should support for robust integration,
• what remains optional future work for deeper CAIP/SIWx alignment.

Compatibility Matrix

Interoperability Area	NanoSession Rev 6 (Current)	Interop Guidance
Scheme & Proof Model	scheme: "exact" with stateful session binding via extra.nanoSession and payload.proof block hash	Treat NanoSession as an exact mechanism variant, not a new scheme id
x402 V2 Headers	Uses PAYMENT-REQUIRED and PAYMENT-SIGNATURE	Preserve standard headers and base64 JSON transport
Network, Account, Asset Fields	network: "nano:mainnet", payTo: "nano_...", asset: "XNO"	Support current values now; CAIP-normalized profile is future/optional
Payload/Extra Tolerance	payload.proof is canonical; extra.nanoSession required for binding	Adapters SHOULD tolerate shape variants used by ecosystem clients
Session Identity Extensions	Core flow is per-request payment	SIWx-style reusable identity is optional future extension work

Current Baseline (Implemented)

Scheme & Proof Model

NanoSession implements x402 exact and does not introduce a separate protocol scheme name.

• Canonical values:
• scheme: "exact"
• network: "nano:mainnet"
• payload.proof carries the Nano block hash
• extra.nanoSession carries session-binding fields (id, tag, resourceAmountRaw, tagAmountRaw, optional expiresAt)

x402 V2 Headers

NanoSession is aligned with x402 v2 header transport.

• PAYMENT-REQUIRED for 402 negotiation payloads
• PAYMENT-SIGNATURE for retry requests with payment proof

Network, Account, Asset Fields

Current Rev 6 wire values are:

• network: "nano:mainnet"
• payTo: "nano_..."
• asset: "XNO" These are the interoperability baseline for current NanoSession implementations.

Adapter Requirements (Recommended Now)

Payload/Extra Tolerance

To maximize third-party compatibility, adapters SHOULD:

• accept payload.proof as canonical and MAY accept legacy payload.blockHash
• tolerate unknown top-level fields in payment payloads and requirements
• tolerate optional/absent metadata fields such as resource, description, mimeType
• tolerate optional/absent extra.nanoSession.expiresAt and derive expiry from timeout when needed

Session-Binding Invariants

Adapters MUST preserve NanoSession security invariants:

• verify against issued session requirements (not caller-mutated copies)
• enforce exact amount and destination match
• enforce anti-replay via spent-set checks

Future Optional Interoperability Profile

CAIP-2: Chain Identification

Potential future profile:

• namespace/chain normalization (for example, moving from "nano:mainnet" to a formally registered CAIP-2 identifier)
• formal registry process for Nano CAIP namespace and chain references

CAIP-10: Account Identification

Potential future profile:

• CAIP-10-style account identifiers for destination addresses
• compatibility guidance for clients that currently validate only EVM/SVM-style account formats

CAIP-19: Asset Identification

Potential future profile:

• CAIP-19-style asset identifiers in place of or alongside ticker-style identifiers like "XNO"
• dual-field transition strategy to avoid breaking existing clients

CAIP-122: Sign-In With X (SIWx)

Potential future profile:

• wallet identity and reusable access sessions via a Nano-compatible SIWx pattern
• standardized message-signing conventions in Nano wallets for session reuse
• extension-driven rollout without changing core per-request payment semantics