Hi all,
Has anyone else seen a recent regression with File Search on gemini-3.1-flash-lite?
Since roughly June 1, 2026, we usually get correct answers that clearly use the File Search store, but groundingMetadata is empty (no groundingChunks / groundingSupports). File Search still appears to run (tool_use_prompt_token_count > 0).
Occasionally flash-lite still returns grounding metadata correctly — so it’s not 100% broken, but mostly broken since that date.
Same request on gemini-3.1-flash-preview consistently returns full grounding metadata.
We rolled back our app to a version from ~1 week ago and the issue persists, so it looks server-side / model-route specific, not our code.
Related thread (Google Search grounding, similar symptom): https://discuss.ai.google.dev/t/search-grounding-metadata-is-empty-even-when-search-was-performed/79831
Is anyone else hitting this on flash-lite right now?