Add Neo namespace and CAIP-2 profile

[erikzhang]

Summary

• Add the base neo namespace documentation for blockchains implementing the Neo N3 protocol.
• Define a CAIP-2 profile using the canonical unsigned decimal representation of Neo Network Magic.
• Document JSON-RPC resolution, well-known Neo and NeoFS networks, private-network collision behavior, validation cases, and security considerations.

Motivation

Neo N3 does not currently have a canonical CAIP-2 identifier, which limits interoperability with chain-agnostic wallets, SDKs, payment protocols, and other multi-chain infrastructure.

This proposal was discussed with the Neo community in neo-project/proposals#238. The discussion supported using neo as the namespace and the existing Network Magic value as the CAIP-2 reference.

Specification

The profile defines Neo chain IDs in the following form:

neo:<network-magic>

The reference is the Network Magic encoded as a canonical unsigned decimal string. It must:

• match ^(0|[1-9][0-9]{0,9})$;
• be within the uint32 range 0..4294967295;
• contain no sign, base prefix, separator, surrounding whitespace, or leading zeroes.

Clients can resolve the identifier through the standard Neo JSON-RPC getversion method by reading result.protocol.network.

The profile includes identifiers for these well-known networks:

Network	CAIP-2 chain ID
Neo N3 MainNet	neo:860833102
Neo N3 TestNet T5	neo:894710606
NeoFS MainNet	neo:91414437
NeoFS TestNet	neo:735783775

Because Network Magic is operator-selected and not globally allocated for private networks, the profile explicitly documents collision behavior and operator responsibilities. It also notes that a CAIP-2 identifier obtained from an RPC endpoint is not, by itself, proof of endpoint authenticity.

CAIP-10 account identifiers and CAIP-19 asset identifiers are intentionally left for follow-up proposals.

Verification

• The uint32 Network Magic type is defined by ProtocolSettings.Network.
• The Neo N3 MainNet and TestNet T5 values match the official config.json and config.testnet.json.
• The NeoFS values match the well-known constants in neo-go.
• The resolution procedure matches the official getversion JSON-RPC documentation.
• The CAIP-2 profile includes positive and negative test vectors covering canonical decimal encoding and both uint32 boundaries.

Related discussion

• Neo community discussion: register a CAIP namespace and CAIP-2 profile for Neo N3