Reviewed 2026-10-10
Inventory the workflow you already rely on
Record the actual provider endpoint and model identifier, input fields, reference files, output formats and billing assumptions. Keep a few representative successful tasks and common failures. Include exact lettering, a product edit and a simple new-image brief so the acceptance set covers different demands.
Save raw outputs and note any manual fixes. Agree which requirements must remain after migration: supported shape, product preservation, complete download or a maximum task cost. This gives you a baseline that can be checked without relying on memory or a demo selected for its appearance.
Test 2.1 with a separate integration
Use the documented 2.1 endpoint and verify its input contract instead of changing only the label in a model menu. Confirm the allowed settings, reference handling and returned files before routing existing work through it. Keep each task's actual model identifier visible in your records.
Run the acceptance set under comparable settings and inspect the same criteria. Record quotes, failed requests and correction effort alongside output quality. If an option differs, adjust the application deliberately and repeat the affected test; do not silently carry an old reference limit or price into the new workflow.
Roll out gradually and define the fallback
Start with a bounded portion of your own workflow or a small group that understands the test. Decide what will stop the rollout: a recurring identity error, incompatible output, or cost beyond the agreed limit. Keep task identifiers so failures can be investigated without creating duplicate requests.
Retain the previous workflow until the new one meets the acceptance criteria. A fallback must identify which model actually produced the image and whether another request has a cost. Returning an older model's output under a 2.1 label would make later review and billing decisions unreliable.
Use official lifecycle notices to schedule the switch
The official Google table reviewed on October 10, 2026 lists Nano Banana 2.1 as the recommended replacement for gemini-3.1-flash-image, but does not announce a shutdown date for that stable model. An October 29 deadline should therefore not drive a forced migration.
Check the current lifecycle documentation and your provider's release notes before changing production use. Keep the review date and acceptance record with the integration. If a confirmed notice changes the deadline or supported options, update the affected tests and tell users which workflow remains available.
Questions before you start
Is a migration required by October 29, 2026?
No such deadline is announced for gemini-3.1-flash-image in the official table reviewed on October 10, 2026. Recheck the linked documentation for later changes.
Can I migrate by renaming the model selector?
No. Verify the endpoint, input fields, output processing, request status and cost. A different display label does not change which model receives a task.
What belongs in a migration acceptance set?
Use representative generation and editing briefs, their original references, expected output settings and explicit pass criteria. Keep all raw results and record corrections and costs.