Google ships Antigravity Agent 09-2026, a breaking update to its Gemini API coding agent

Google's Gemini API changelog recorded a new build of its Antigravity coding agent on September 17, 2026: antigravity-preview-09-2026, which replaces and deprecates the prior antigravity-preview-05-2026 build and ships with a materially different tool-calling interface for anyone running the agent locally.

What's new

According to the Gemini API changelog, Google "released antigravity-preview-09-2026, which replaces and deprecates antigravity-preview-05-2026." For most integrations the change is trivial: developers running the agent in Google's remote sandbox (environment: "remote") who only read output_text or model_output steps just need to swap the agent string and nothing else changes.

The more consequential change hits anyone running tools locally or parsing function_call steps directly. The built-in tool set was redesigned: parameters moved from snake_case to PascalCase, and file edits switched from full-file rewrites to line-range replacements. The changelog's comparison table lays out the specifics — file creation moved from write_file(path, content) to write_to_file(TargetFile, CodeContent, Overwrite, Description); file editing moved from a full-rewrite write_file call to replace_file_content(TargetFile, StartLine, EndLine, TargetContent, ReplacementContent); file reading moved from byte-offset read_file(path, offset, limit) to view_file(AbsolutePath, StartLine, EndLine, ContentOffset); directory listing moved from list_files(path) to list_dir(DirectoryPath); and file/code search, which previously didn't exist as a built-in (agents fell back to shell commands), now ships as dedicated find_by_name and grep_search tools. Shell execution and web search tool signatures are unchanged.

Google set a hard cutover date: antigravity-preview-05-2026 shuts down on October 5, 2026, and the deprecation is tracked on the Gemini API's deprecations page alongside Google's other managed-agent sunsets.

Context

Antigravity is Google's agentic coding tool built on the Gemini API, competing directly with OpenAI's Codex and Anthropic's Claude Code as an AI system that can read, write, and execute code changes across a real file system rather than just chat about them. Google has been iterating on the underlying agent model roughly every few months, and each iteration has quietly changed the tool contract that the agent uses to interact with a developer's machine — this is at least the second such tool-schema rewrite in the antigravity-preview line this year.

Moving from snake_case to PascalCase parameters and from full-file rewrites to line-range edits brings Antigravity's local tool interface closer to the conventions used by other coding-agent harnesses, and the switch to targeted line-range edits in particular should reduce token usage and merge-conflict risk for large files compared to rewriting an entire file on every edit.

Why it matters

This is a breaking change with a fixed deadline, not an optional upgrade: any developer or product that built local tool-execution logic against antigravity-preview-05-2026's snake_case, full-rewrite tool schema has three weeks from the September 17 release before that agent string stops working on October 5. Teams running Antigravity purely through Google's remote sandbox are insulated from the tool-schema change and only need to update a version string, which is a meaningfully lower migration cost and likely by design — Google is pushing integrators toward the managed remote environment rather than local tool execution, where it controls both sides of the interface and can make breaking changes like this one without third-party coordination.