Google has established its Interactions API as the official default interface for Gemini models and autonomous agents, marking a significant architectural shift toward stateful, agentic workflows. Introduced with comprehensive updates since December, the platform replaces the legacy role-based schema with a streamlined, step-oriented structure where every interaction sequence is explicitly defined. This redesign optimizes the API for complex, multi-step agent operations while maintaining full backward compatibility for existing implementations. The updated interface introduces several foundational capabilities for advanced application development. Developers can now provision remote Linux sandboxes for managed agents with a single call, featuring the Antigravity model as the default alongside support for custom agents equipped with specialized instructions, skills, and data integrations. Asynchronous execution is natively supported through a background execution flag, enabling non-blocking task processing. Tool orchestration has also been expanded, allowing seamless integration of built-in services like Google Search and Maps with custom functions, while responses now support concurrent text and image outputs. Advanced reasoning and content generation capabilities have received substantial enhancements. Deep Research now offers configurable speed and depth modes, collaborative planning features, native visualization generation, and multimodal grounding across images, PDFs, and audio. Media generation capabilities have been upgraded to include Nano Banana 2 for image synthesis, Lyria 3 for audio production, and multi-speaker text-to-speech functionality. Developer experience improvements include Flex and Priority tiers for optimizing costs or latency, fifty-five-day interaction retention on paid plans, and precise error targeting that isolates specific schema fields. Google has designated the Interactions API as the primary interface across Google AI Studio, the Gemini API, and all official documentation, providing a configuration toggle to revert legacy code snippets. While the traditional generateContent API remains fully supported for ongoing model deployments, the company indicates that frontier capabilities for long-running and multi-agent systems will increasingly prioritize the Interactions framework. To accelerate adoption, Google released the gemini-interactions-api Skill, a specialized context injector designed to keep autonomous coding agents synchronized with current best practices, including streaming protocols, function calling, structured outputs, and Deep Research implementation patterns. This ecosystem shift establishes a unified standard for next-generation AI application development, reducing integration complexity while expanding autonomous agent capabilities.