Summary

The A2A Python SDK (a2a-sdk) has released v1.0.0-alpha.0 (2026-03-17) which upgrades to the A2A 1.0 spec with proto-based types.

Currently, ADK 1.28 depends on a2a-sdk 0.3.24 which uses protocol_version: "0.3.0".

Request

Upgrade the a2a-sdk dependency in google-adk[a2a] to support the A2A 1.0 specification, including:

• Proto-based types from a2a-sdk >= 1.0.0
• Updated protocol_version default to 1.0.0
• Any breaking changes in AgentCard, AgentSkill, and related types

References

• A2A SDK release: https://github.com/google/a2a-python/releases/tag/v1.0.0-alpha.0
• Breaking changes commit: spec upgrade SDK to A2A 1.0 spec and use proto-based types (Request for CMEK Support in Vertex AI Agent Engine #572, Error with multiple function calls when token streaming via LiteLLM and adk web #665, VertexAiSessionService list sessions always returns empty list #804, Problem with retrive live conversation using sessions. #765)