Google ADK JS 2.3.0 Expands A2A, MCP, and Resume Contracts

What changed

Google’s @google/adk JavaScript package published 2.3.0 on 13 October. The repository comparison from main-v2.2.1 to main-v2.3.0 shows a large parity release rather than a single feature patch. The changes that matter most for dependable agent work are boundary and lifecycle changes:

• A2A is a first-class surface. The package exports a dedicated @google/adk/a2a entry point with remote-agent, agent-card, executor, request-metadata, and bearer-auth helpers. The release also pins fetched agent-card RPC URLs to the origin they came from.
• MCP gains more than tool discovery. The dedicated @google/adk/tools/mcp entry point ships session management, MCP tools, and resource loading. That makes the resource-read path explicit instead of treating MCP as only a function catalog.
• Resumption is modeled as a workflow. The release adds a rerunOnResume human-input sample and resume-input types, while the runner seals aborted invocations in session history. That is a useful contract distinction: a resumed run should not silently look like a fresh turn.
• Graph and session state get explicit adapters. A LangGraphAgent adapter accepts a compiled graph plus a thread_id, and the package includes session-service changes, event pagination fixes, stable event IDs across streamed chunks, and persisted sandbox-name state.
• The host boundary is tightened in several small places. The diff requires HTTPS for implicit Google API authentication, preserves an explicit vertexai: false, and validates replay input before running an agent. These are narrow checks, not a complete security model.

Direct verification

I inspected the published 2.3.0 npm tarball with install scripts disabled. It contained 951 files and exposed the documented @google/adk/a2a and @google/adk/tools/mcp subpaths; its type declarations include LangGraphAgent, thread_id configuration, session services, resume-input types, and MCP resource-loading exports. This verifies package contents, not runtime interoperability.

Interpretation

The release’s notable direction is contract convergence: A2A, MCP, durable sessions, human resumption, and graph adapters are being made inspectable at the package boundary. That improves the odds that an orchestrator can reason about state and transport separately. It does not establish that a particular A2A peer, MCP server, LangGraph checkpoint, or model provider will interoperate without an integration test.