Google has upgraded its Gemini Managed Agents framework with the antigravity-preview-09-2026 harness, powered by Gemini 3.8 Flash, to address latency on extended tasks and secure integration with external enterprise tools. The release introduces intelligent model switching, context caching gains, and two dedicated APIs for data ingestion and authorization. The harness orchestrates long-running multi-step tasks, system instructions, and dynamic tool calls, delivering faster token throughput without sacrificing reasoning quality. Context caching efficiency increased, producing a 22% hit rate improvement on long, multi-step tasks and a 9% boost on complex coding workflows, reducing redundant token processing, latency, and API costs. Dynamic model switching lets agents pivot between task-specific model variants by execution step, such as lightweight mode for basic text extraction and high-reasoning execution for data analysis or code generation. Streamlined agent loops minimize redundant state serialization between steps, preventing "agent drift" during long-running background tasks. The Files API lets developers stream large datasets, media files, and unstructured documents directly into an agent's working context, avoiding custom pre-processing pipelines or complex vector indexing; an agent can consume a raw Q3 sales spreadsheet and generate a dashboard displaying metrics like $2.67 million in Q3 revenue by region and product tier. The Credentials API acts as a secure vault for external integrations, allowing agents to call third-party services while protecting API keys, OAuth tokens, and database secrets.