Google releases antigravity-preview-09-2026, deprecating the May build on 5 October 2026
Google's new Antigravity harness brings PascalCase tool parameters and line-range file edits. Here's who needs to act before 5 October 2026.
Google has released antigravity-preview-09-2026, a new harness version for the Gemini Antigravity agent, and with it comes a firm end date for the previous build. antigravity-preview-05-2026 will stop accepting requests on 5 October 2026, at which point the platform will redirect traffic to the updated harness. If you are running anything in production against the May preview, you have a fixed deadline to work with.
The new version is live now in the Interactions API and Google AI Studio. To opt in, update your agent string to "agent": "antigravity-preview-09-2026".
What Antigravity actually does
For anyone coming to this fresh: Antigravity is Google’s platform for orchestrating autonomous AI agents. A single API call spins up a Gemini model inside an isolated Linux sandbox. The agent reasons over your prompt, executes code, manages files, browses the web, and repeats that loop until the task is complete. You interact with it through the Interactions API and can run tools either inside Google’s remote sandbox or locally in your own environment.
The September 2026 release brings the agent’s tooling closer in line with the full Antigravity Coding Agent experience, upgrades the runtime with improved prompt caching, and introduces two companion APIs described further below.
The two breaking changes
Most of the update is additive, but two changes will break existing code if you run tools locally or parse function_call steps directly.
1. Built-in tool parameters now use PascalCase
Previously, built-in tool parameters followed snake_case naming conventions, for example file_path or start_line. In antigravity-preview-09-2026, those parameters use PascalCase: FilePath, StartLine. If your local tool handler maps parameter names to variables or passes them through to downstream functions, those mappings will need updating before 5 October 2026.
2. File edits now use line-range replacements
The May build sent full file rewrites when the agent needed to modify a file. The September build switches to line-range replacements, specifying exactly which lines to change rather than resending the entire file. This is faster and significantly cheaper on tokens for large files, but it means any code that reconstructs file state from agent output, or that implements the edit step locally, needs to account for the new format.
Two new search tools also land alongside these changes: find_by_name() and grep_search(), which give the agent native file and code search without requiring a separate tool definition.
What this means for you
The answer depends on how you are using the API.
If you use a remote sandbox and only read output_text or model_output steps, your migration is minimal. Update the agent string and you are done. The harness handles all the tool execution on Google’s infrastructure, so the parameter and file-editing changes do not surface in your integration.
If you run tools locally or inspect function_call steps, you have real work to do. Rename your parameter bindings from snake_case to PascalCase, update any file-editing logic to handle line-range replacements rather than full rewrites, and add support for the new find_by_name and grep_search tools if you want the agent to be able to call them in your environment. The official deprecations page tracks the 5 October 2026 hard shutdown, so put that date in your team’s calendar now.
Pricing is unchanged, and the new harness is available on the free tier in Google AI Studio, which makes it straightforward to test your updated integration before committing to a production rollout.
Two new APIs worth knowing about
The September release ships two companion APIs that make building with managed agents more practical.
The Files API gives you a proper mechanism for getting data in and out of the agent’s sandbox. Previously, agent environments were largely transient, and moving files in or out often meant full rewrites that were both inefficient and token-heavy. The Files API lets you upload, list, and download files directly into a persistent sandbox environment.
The Credentials API lets the agent use services you already have access to, from MCP servers to third-party APIs, in a way that keeps credentials out of your interaction payload. You store a credential server-side and reference it by ID in an allowlist rule. The proxy resolves that ID per request, so a credential’s value is never frozen into the interaction at submit time. For teams handling sensitive credentials, this is a meaningful security improvement over the previous approach.
Getting the update
Switch to antigravity-preview-09-2026 using the Python SDK, the JavaScript SDK, or REST. The official changelog has the full list of changes, and the Antigravity agent guide covers the updated tool definitions in detail.
The hard shutdown for antigravity-preview-05-2026 is 5 October 2026. If you are a local-tool user, that is your deadline for the parameter renaming and file-edit logic changes. If you are on a remote sandbox reading output only, a single string update is all that stands between you and the new harness.