Add Interactions API support to adk-java

[prasadskarmarkar]

Description:

Interactions API ( https://blog.google/innovation-and-ai/technology/developers-tools/interactions-api/) provides a unified interface for interacting with Gemini models and agents with stateful multi-turn conversations and server-side history management.

This feature is already available in adk-python (since v1.21.0) but is currently missing in adk-java, creating a feature parity gap between the two SDKs.

Proposed Solution

Add support for the Interactions API in adk-java, similar to how it's implemented in adk-python with the use_interactions_api=True parameter in the Agent configuration.

Additional context

• https://blog.google/innovation-and-ai/technology/developers-tools/interactions-api/
• https://developers.googleblog.com/building-agents-with-the-adk-and-the-new-interactions-api/
• https://github.com/google/adk-python/tree/main/contributing/samples/interactions_api

[prasadskarmarkar]

Adding a note on dependencies:

Support for the Interactions API in adk-java depends on the availability of the Interactions API in the underlying java-genai SDK.

There is already an upstream feature request for this in java-genai, and I have opened a corresponding implementation PR:

• Feature request: Support for Interactions API googleapis/java-genai#749
• Implementation PR: feat(interactions): Add Interactions API support for Java SDK googleapis/java-genai#792

Once this is available in java-genai, it will unblock adding Interactions API support in adk-java.