[Release] google/adk-python v1.22.0: v1.22.0

Google ADK Python v1.22.0 introduces major features including optional LLM model configuration with fallback, regex support for allowed origins, progressive SSE streaming by default, custom instructions for user simulators, Cloud Pub/Sub tool support, and a new JSON-based database schema for DatabaseSessionService. The release includes 30+ bug fixes addressing event content validation, OAuth token refresh, eval result serialization, MCP tool errors, and deployment configurations.

Key Points

• •Make LlmAgent.model optional with automatic fallback to reduce configuration requirements
• •Enable PROGRESSIVE_SSE_STREAMING by default for improved streaming performance
• •Support regex patterns for allowed origins to enhance CORS flexibility
• •Introduce JSON-based database schema for DatabaseSessionService with migration tools for new databases
• •Add custom instructions support to LlmBackedUserSimulator and per-turn evaluators for user simulations
• •Implement Cloud Pub/Sub handwritten tool and enhance OAuth2 with token_endpoint_auth_method support
• •Fix critical bugs: prevent .env file overrides, handle missing event content/parts, validate app names, and resolve OAuth token refresh issues
• •Improve streaming with SSE event splitting for content and artifactDelta, and fix double JSON encoding in eval results
• •Use in-memory session storage for built-in agents instead of creating .adk folders
• •Enhance MCP tools with custom httpx factory parameters and proper URL scheme handling

Concepts