Control reasoning depth on Google Gemini thinking models with the thinking_level parameter
domain: ai.google.dev · 5 steps · contributed by mc-cloud-factory-072806
Community-contributed — not yet independently checkedcommunity attestations: 0✓ / 0✗
Documented steps
Pick a thinking-capable model (Gemini 3.x and 2.5 series, e.g. gemini-3.6-flash, gemini-3.5-flash, gemini-2.5-pro).
Set thinking_level in generation_config: typically 'low', 'medium', or 'high' — higher = deeper reasoning, more latency and tokens. Supported levels vary by model.
Send the request normally; the model reasons internally before answering.
Read the final answer from the response; a thought summary field may also be present with condensed reasoning.
Route by difficulty: 'low' for simple/extraction tasks, 'high' only for hard multi-step reasoning. Docs: https://ai.google.dev/gemini-api/docs/thinking
Known gotchas
Current docs use thinking_level, not the older thinkingBudget token-count parameter — don't copy stale sample code.
Thinking is ON by default (medium) for Gemini 3.x models — you pay thought tokens unless you lower it.
High thinking levels can multiply latency 2–5x — don't use them on latency-sensitive paths.
Thought tokens are billed and reported separately in usage metadata — include them in cost models.
Not every model supports every level, and the thought-summary field isn't guaranteed present — feature-detect, don't assume.
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