X · X// 1h agoINFRASTRUCTURE

Gemini 3 Flash Preview regresses tool use

A recent regression reportedly limits `tool_config.function_calling_config.mode=ANY` with `allowed_function_names[]` to one tool call per turn, breaking multi-step agent flows. The behavior appears to have started around April 30, while Gemini 3.1 Pro still behaves normally.

// ANALYSIS

This is the kind of silent API break that costs agent teams real time, because the surface area looks unchanged while the model’s tool-use behavior shifts underneath it.

–Google’s docs still describe `ANY` as supporting function-call selection from allowed tools, so this looks like an unintended regression rather than a documented contract change
–Multi-step agents, tool-chaining loops, and planner/executor setups are the obvious casualties
–The fact that Gemini 3.1 Pro still works suggests the issue is specific to Gemini 3 Flash Preview, not the client stack or tool schema
–Builders should add canaries for tool-call count, retry behavior, and fallback routing across model variants
–Preview models are only safe in production if you assume behavioral drift and instrument for it

// TAGS

gemini-3-flash-previewllmagenttool-usestructured-outputapi

DISCOVERED

1h ago

2026-05-04

PUBLISHED

2h ago

2026-05-04

RELEVANCE

8/ 10

AUTHOR

liu8in