Google Gemini Interactions API Breaking Structural Change Now Default (outputs→steps); Legacy Removed on 6/8 L1
Confidence: High
Key Points: A breaking change to the Google Gemini Interactions API request/response structure became the default on 2026-05-26. Announced on 5/6: the response field has changed from 'outputs' to 'steps', with corresponding adjustments to the 'response_format' output configuration; the legacy structure will be completely removed on 2026-06-08. Google has provided a migration guide. Any application that has integrated the Gemini Interactions API must update its parsing and request code before 6/8, or service will be disrupted.
Impact: Starting today, developers using the Gemini Interactions API without specifying legacy mode will receive responses in the new structure. Migration must be completed before 6/8, after which unupdated services will break immediately. This is a breaking API change that requires immediate scheduling.
Detailed Analysis
Trade-offs
Pros:
- The new structure ('steps') has clearer semantics, benefiting multi-step agent workflows
- An official migration guide is provided with a clear path forward
Cons:
- Breaking change — unmigrated services will break after 6/8
- Requires rewriting response parsing and 'response_format' configuration
- Short migration window (approximately one month from announcement to removal)
Quick Start (5-15 minutes)
- Search your codebase for any parsing of the Interactions API 'outputs' field
- Update to read 'steps' and revise the 'response_format' configuration
- Follow the official migration guide and run regression tests — must be completed before 2026-06-08
Recommendation
Immediately audit all services using the Gemini Interactions API and schedule migration — do not delay until the 6/8 removal date. After migrating, run regression tests on critical workflows to confirm the output structure is correct.
Sources: Google AI for Developers — Gemini API changelog (Documentation)