Google releases Gemini 3.5 Flash to GA and launches Managed Agents in the Gemini API with the Antigravity Agent

Google made three connected announcements on May 19, 2026: Gemini 3.5 Flash reached general availability, Managed Agents launched in the Gemini API as a public preview, and Google shipped Antigravity — its first general-purpose managed agent — alongside the infrastructure to run it. Together the releases position the Gemini API as a full-stack platform for agentic application development.

What's new

Gemini 3.5 Flash (GA)

• Model ID: gemini-3.5-flash
• Google describes it as "our most intelligent model for sustained frontier performance on agentic and coding tasks"
• Promoted from preview to general availability — suitable for production workloads
• Replaces gemini-2.0-flash models, which were shut down June 1, 2026

Managed Agents in the Gemini API (public preview)

• Developers can build and deploy autonomous, stateful agents in secure, isolated Google-hosted Linux sandbox environments
• Agents have access to code execution, file management, and web browsing within the sandbox
• Available under public preview — no waitlist required

Antigravity Agent (antigravity-preview-05-2026)

• A general-purpose managed agent released alongside the Managed Agents platform
• Capable of autonomous planning, reasoning, code writing and execution, file management, and web browsing
• Runs entirely inside the Google-hosted sandbox
• Google's first first-party general-purpose agent shipped through the Gemini API

Supporting infrastructure (released earlier in May)

• May 4: Event-driven webhooks in the Gemini API, replacing polling for Batch API and long-running operations
• May 5: Multimodal File Search supporting image embedding and search via gemini-embedding-2, with visual citations in grounding metadata

Context

Gemini 3.5 Flash was in preview ahead of this announcement. Its GA timing alongside Managed Agents is deliberate: Google is releasing both the model and the execution layer as a bundled offering. The pattern parallels what Anthropic did with Claude Managed Agents — provide the model, the sandboxed runtime, and a reference agent together so developers can evaluate the full stack.

The Gemini API's move to managed agents follows a busy May for Google. Gemini 3.1 Flash Image and 3 Pro Image reached GA on May 28. Gemini 3.1 Flash-Lite was promoted to GA on May 7. Google is systematically graduating its preview model lineup while simultaneously extending the platform surface with agentic infrastructure.

The Antigravity Agent name echoes Google's internal project naming conventions and suggests the agent will expand beyond preview into a productized offering. Its capability set — plan, reason, code, browse — is the same core loop that Anthropic's Managed Agents and OpenAI's agentic products target.

Why it matters

Gemini 3.5 Flash GA gives developers a stable, production-grade model at what Google positions as the frontier of intelligence-per-cost for agentic tasks. Unlike preview models, GA models carry SLA commitments and deprecation notice requirements, which matters for production deployments.

The Managed Agents platform is more significant in the medium term. Running agents requires not just a model but an execution environment — compute, sandboxing, state management, tool access. Developers who build on the Gemini Managed Agents API offload all of that to Google. The competitive implication: Google is not just a model provider for agents, it is an agent runtime.

Antigravity is the proof-of-concept. A first-party agent that codes, browses, and manages files inside a sandbox signals that Google will operate above the API layer — shipping ready-made agents alongside the platform they run on.