Summary: CAIP-27 is best understood as the post-authorization execution envelope in the CAIP-25 wallet-session stack rather than as another connect-wallet handshake. Its core move is to wrap a previously authorized JSON-RPC request inside a wallet_invokeMethod envelope that names the target chainId, optionally ties the call to a sessionId, and can attach capability metadata announced by the wallet during session creation. That makes it a useful comparison class for CAIP-25, CAIP-316, and wallet-provider conventions like EIP-1193: those standards negotiate or describe authority, while CAIP-27 standardizes how an app actually spends that authority against a specific chain or namespace after the session exists.
What it does:
Defines a wallet_invokeMethod JSON-RPC envelope for sending a previously authorized request to a specific CAIP-2 chain identifier
Nests the downstream RPC method and params inside a request object instead of sending bare provider calls directly
Makes sessionId conditional rather than universal, so invocation can work across both identifier-based and no-identifier CAIP-25 / CAIP-316 session models
Lets callers attach optional capabilities metadata tied to features the wallet exposed during session negotiation
Preserves routing context in the response by returning the target chainId and, when applicable, the sessionId alongside the nested RPC result
Distinguishes top-level connection or session failures from nested target-method errors, so transport problems do not get conflated with chain- or namespace-specific authorization failures
Key claims:
The most important design move is making post-connect execution a first-class standardized layer. CAIP-27 says wallet authorization is not complete when a session is granted; there also needs to be a portable way to route later calls to the right target network.
The target-routing envelope matters because the same RPC method names can exist across multiple chains or namespaces. CAIP-27 turns chain choice into explicit session-scoped metadata instead of leaving it to wallet-specific heuristics.
The optional capabilities object is analytically important because it shows session negotiation is not just an up-front yes/no gate. Wallet-advertised features can keep shaping individual method invocations after authorization has already been granted.
The response design is also part of the mechanism. By preserving chainId and separating top-level transport/session failures from nested method errors, the spec keeps routing state and target-specific failure semantics legible to middleware.
CAIP-27 becomes more useful when read with CAIP-316: once sessionId is no longer mandatory in every flow, invocation semantics depend on how the session is being tracked, which means transport assumptions quietly affect execution behavior.
In corpus terms, CAIP-27 helps unbundle wallet UX into distinct layers: create a session, invoke an authorized method against a chosen target, receive notifications, query current state, and revoke the relationship.
Whitepaper: No standalone CAIP-27 whitepaper or litepaper surfaced in this pass. The clearest primary materials were the official draft text, the raw CAIP markdown, and the adjacent CAIP-25 / CAIP-316 standards that define how the invocation envelope inherits session authority; see ../../whitepapers/caip-27-primary-sources-2026-05-14.md.
Keep it on the narrow thing it actually does: spend previously granted wallet-session authority against a chosen target chain. Not the handshake, not the lifecycle bundle, and not a generic wallet-connectivity hub.