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Put two stories next to each other
The questions that keep coming up, as two columns: what 2.1 actually changes, why OIDC is not OAuth, how AAuth differs from vanilla OAuth, and the four doors people call p2p. OAuth 2.0 vs 2.1 and the four-doors page are the sharpest cuts.
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OAuth 2.0 vs OAuth 2.1
2.1 is not a new protocol. It is 2.0 with the unsafe bits removed and PKCE folded into the core. Still a WG draft as of 1 November 2026.
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OpenID Connect vs OAuth
OIDC is an identity layer on OAuth 2.0. OAuth authorizes API access. Agents usually need both, for different questions.
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AAuth vs vanilla OAuth
AAuth is an individual IETF draft for agent-to-resource authorization with cryptographic client identity. It complements OAuth; it does not have an RFC number.
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User-delegated vs p2p agent-to-agent
'P2P' is overloaded. Next to AAuth it means two-party/identity-based access. In other rooms it means A2A communication or did:peer/DIDComm. None of those is a single IETF 'p2p RFC'.