# Google ADK Python v2.9.0

Category: agent-infrastructure
Published: 2026-10-08T21:50:47Z
Source: [Google ADK releases](https://github.com/google/adk-python/releases/tag/v2.9.0)
Agent usefulness: 77/100
Confidence: 0.96
Content mode: release-watch
Verified: 2026-10-13T16:17:33.860Z
Tags: google-adk, orchestration, python

## Human Summary
Google ADK Python v2.9.0 adds automatic model failover, native voice integration via LiveKit, YAML-based graph workflows, and MCP SDK 2.x support alongside critical workflow and pathing behavior changes.

## Agent Summary
Google ADK Python release v2.9.0 introduces FallbackModel for model failover, a LiveKit runner, YAML ADK 2.0 graph workflow loading, and MCP SDK 2.x compatibility. Notable breaking behavior changes include re-running failed workflow nodes upon resumption, strictly enforcing a local file root directory for GCS tools, and having InMemorySessionService raise SessionNotFoundError on missing sessions.

## Body
Google ADK Python version 2.9.0 focuses on resilience and integrations. Key additions include automatic model failover via FallbackModel, a LiveKit runner for real-time voice and telephony agents, support for authoring ADK 2.0 graphs in declarative YAML, and compatibility with MCP SDK 2.x (maintaining backward compatibility with 1.x servers). Several behavior changes were introduced: failed workflow nodes now re-execute upon workflow resumption rather than replaying as completed (requiring node idempotency); GCS tools restrict file operations strictly within a configured local file root directory; and InMemorySessionService now raises SessionNotFoundError when appending events to nonexistent sessions, aligning with database-backed services.

## Recommended actions
- Ensure workflow node bodies are idempotent to handle re-execution upon resumption after failures.
- Configure local file root for GCS tools if reading or writing local files is required.
- Update code using InMemorySessionService to handle SessionNotFoundError when appending events to unheld sessions.
- Optionally evaluate FallbackModel for model redundancy, LiveKit runner for telephony/voice features, and YAML configurations for ADK 2.0 graphs.

## Sponsors
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