Google ships new Gemini managed agents runtime with 30% cost cut, Files and Credentials APIs

On Sept 18 Google released antigravity-preview-09-2026, a major update to Gemini managed agents. According to Google's Phil Schmid, the release centers on cost efficiency and two new interfaces: cache hit rate improves by up to 22% and costs drop by as much as 30%, while multi-turn coding task completion rises 8%. Antigravity itself continues to iterate, with the new version supporting remote deployment and interaction with remote Antigravity agents.

Confirmed

• The new runtime ships an updated agent harness whose tools and behavior are closer to Antigravity, as also described in Google AI Studio's official post
• The runtime defaults to Gemini 3.8 Flash with a configurable default model
• The sandbox is a persistent Linux environment supporting bash execution and file tools
• Files API: handles data in and out of the agent sandbox; files.upload() feeds files inline or in conversation, files.list() lists them; clmt notes it also supports file exchange with live agent sandboxes
• Credentials API: credentials.create() registers secrets once, supporting bearertoken, environment variables and more; credentials are never exposed, an egress proxy blocks unauthorized requests, and exposure-free OAuth is supported
• The new harness performs better, and Antigravity can be deployed remotely and interact with remote agents

Why it matters

• Combined cost and completion gains lower the barrier to building long-task agents, especially in multi-turn coding
• The Credentials API's design (secrets never touch the app, egress proxy blocks unauthorized access) addresses the most sensitive concern when agents call external APIs and is worth referencing for similar agent platforms

2026-09-18 ~ 2026-09-18 · 6 related posts

• [source] Google's Gemini managed agents update: 30% lower costs, new Files and Credentials APIs — _philschmid · 2026-09-18
• Antigravity agent runtime upgrade: 30% cheaper multi-turn coding, 8% higher task completion — _philschmid · 2026-09-18
• Gemini Credentials API deep dive: zero plaintext secrets and egress-proxy exfiltration blocking — _philschmid · 2026-09-18
• Google adds Files API and secret-safe Credentials API to Gemini managed agents — _philschmid · 2026-09-18
• [source] Google updates Gemini managed agents: new harness, Files API, managed credentials — osanseviero · 2026-09-18
• [source] Antigravity adds remote agent deploys, Files API and credential-safe OAuth — clmt · 2026-09-18