Model Versioning And Capability Evolution With Backward Compatibility

via “specification versioning and backward compatibility management”

Agent2Agent (A2A) is an open protocol enabling communication and interoperability between opaque agentic applications.

Unique: Embeds versioning as a first-class protocol concern (version in messages and AgentCard) rather than relying on external version management, enabling agents to negotiate compatibility at runtime

vs others: More explicit than implicit versioning and more flexible than single-version protocols, enabling gradual migration across heterogeneous deployments