The Antigravity SDK is now offered as the official runtime for building custom agent hubs, bringing the same engine that powers Antigravity 2.0 and the Antigravity CLI into user‑controlled applications. It adds declarative safety policies, real‑time telemetry, and built‑in multi‑turn state persistence, and it updates automatically when the core runtime is upgraded. Practitioners who need fine‑grained control over agent behavior, observability, or compliance can replace ad‑hoc logging and fragmented tooling with a single, supported SDK.
Core Runtime and Declarative Policies
The SDK’s agent core handles model interaction (including Gemini 3.1 Pro and Gemini 3.8 Flash), tool execution, and generation of thinking traces. By embedding the runtime, developers gain a predictable execution environment that isolates agents in a sandbox and enforces policies defined declaratively. When the underlying Antigravity runtime receives performance or security improvements, those changes propagate to all SDK‑based agents without manual intervention.
Telemetry Middleware via Lifecycle Hooks
Observability is provided by an event‑driven middleware layer that registers to Antigravity SDK lifecycle hooks. These hooks fire on step start, thinking updates, and tool calls. The middleware streams structured events over WebSockets to a dashboard, delivering a live view of each agent’s actions, loaded skills, and connector usage. This replaces the common practice of tailing disparate console logs or manually inspecting JSON transcripts.
Operational Implications
Adopting the SDK changes several operational patterns:
- Unified monitoring: A single streaming API supplies real‑time metrics for token consumption and latency across all agents.
- Policy enforcement point: Declarative safety policies can be updated centrally, affecting all running sessions without redeploying code.
- State management: Built‑in multi‑turn persistence removes the need for external session stores for simple use cases.
- Upgrade path: Runtime upgrades are automatic, reducing the operational burden of patch management.
Security Considerations
The SDK runs agents in a sandboxed environment and applies safety policies before model calls or tool invocations. While the source does not detail specific access controls, the isolation model suggests a reduced attack surface compared with custom script‑based agents that may execute arbitrary code. Practitioners should still evaluate the policy definitions to ensure they cover required compliance checks and that telemetry channels are protected, as the streaming API uses WebSockets which must be secured in transport.
Related CloudNinjas coverage: Google Cloud.
What This Means For Practitioners
Teams building bespoke agent hubs can replace fragmented logging and manual state handling with the Antigravity SDK’s integrated runtime and observability stack. The primary actions are to adopt the SDK, define safety policies that match organizational requirements, and connect the lifecycle‑hook stream to an existing monitoring dashboard. Ongoing evaluation should focus on policy adequacy, telemetry security, and the impact of automatic runtime upgrades on existing workloads.
