Gemini API May 2026 Update: Gemini 3.1 Flash-Lite GA, Interactions API schema migration, multimodal File Search

May 2026 adds three practical Gemini API changes for teams building agentic developer tools: a new GA model SKU (Flash-Lite), a schema migration for Interactions API users, and multimodal File Search for apps doing doc grounding.

TL;DR

• May 7 — gemini-3.1-flash-lite reaches GA (and gemini-3.1-flash-lite-preview is scheduled for deprecation/shutdown).
• May 6 — Interactions API schema migration announced (outputs → steps), with a May 20 default switch and June 6 removal of the legacy schema.
• May 5 — File Search supports multimodal search: embed + search images with gemini-embedding-2, and get improved grounding metadata.

Quick Answer

If you already use Gemini API in production, treat the Interactions API schema change as the urgent one: it has a defined cutover date where the new schema becomes default (May 20) and the old one is removed (June 6). The Flash-Lite GA release is mostly upside (a stable, production-grade “cheap+fast” model option), and multimodal File Search is a clear capability boost for apps that ground responses in PDFs, design docs, screenshots, or diagrams.

gemini-3.1-flash-lite Reaches GA (May 7, 2026)

Google released gemini-3.1-flash-lite as generally available (GA) on May 7, 2026.

• If you avoided preview model IDs in production, this provides a stable, GA-grade “fast and cost-efficient” option in the Gemini 3.1 family.
• Google also announced that gemini-3.1-flash-lite-preview is deprecating on May 11, 2026 and scheduled to shut down on May 25, 2026.

Interactions API: Upcoming Schema Migration (outputs → steps) (Announced May 6, 2026)

On May 6, 2026, Google announced an upcoming breaking change to the Interactions API request/response format.

What’s changing:

• Request/response schema: outputs → steps
• Output format configuration: response_format behavior is changing

Timeline called out in the release notes:

• May 20, 2026 — new schema becomes the default
• June 6, 2026 — legacy schema removed

If your product is an “agent runtime” wrapper over Gemini (chat orchestration, tool calling, eval harness), treat this as a migration project: confirm your serialization format, update tests, and run side-by-side diffing before the May 20 default flip.

File Search Adds Multimodal Search (May 5, 2026)

Google updated File Search on May 5, 2026 to support multimodal search.

What it enables:

• You can embed images with gemini-embedding-2 and search across images natively.
• Grounding metadata now includes media_id for visual citations and page_numbers indicating where information is found.

For AI coding tools, the most direct impact is better retrieval over:

• architecture diagrams
• screenshots (errors, UI states)
• PDFs with figures
• design docs with mixed media

Sources

• Google AI for Developers — Gemini API changelog: https://ai.google.dev/gemini-api/docs/changelog