About FlashRef.dev
An independent reference site for developers migrating to Gemini 3.5 Flash.
Why this site exists
On May 19, 2026, Google released Gemini 3.5 Flash as a GA model. The release included a silent breaking change: the default thinking_level dropped from high (the previous default in gemini-3-flash-preview) to medium. Developers who swapped the model ID without updating their config got a silently less-capable model — no error, no warning, just worse eval scores days or weeks later.
The Hacker News thread on launch day scored 962 points and 658 comments, with many developers discovering the change the hard way. Existing coverage — while good — is spread across blog posts that require reading several paragraphs to reach the actionable fix.
FlashRef.dev exists to be the single URL you bookmark: a scannable, checklist-first reference with copy-paste configs and an interactive cost calculator.
What's covered
- ✓Migration checklist from gemini-3-flash-preview to gemini-3.5-flash
- ✓thinking_level guide: minimal / low / medium / high
- ✓Parameter changes: temperature/top_p/top_k removed, thought preservation, FunctionResponse schema
- ✓Function calling gotchas: 400 errors, thinking_level + thinking_budget conflict, token blowup
- ✓Interactive pricing calculator
- ✓System prompt examples for 5 use cases
Scope and limitations
This site covers only Gemini 3.5 Flash (model ID: gemini-3.5-flash). It does not cover Gemini 3.5 Pro, Gemini 2.0, or any other model family. It does not compare Gemini to OpenAI or Anthropic models.
All content is based on publicly documented Gemini API parameters. The site is static and does not send your API keys or usage data anywhere. The pricing calculator runs entirely in your browser.
Accuracy and freshness
Content is manually reviewed against the official Gemini API documentation at ai.google.dev. The footer on each page shows the last-verified date. Pricing figures are estimates; verify current rates at ai.google.dev before making cost decisions.
Last verified: 2026-06-18 against Gemini API documentation.
Disclaimer
FlashRef.dev is an independent reference site and is not affiliated with, endorsed by, or sponsored by Google. "Gemini" and "Google" are trademarks of Google LLC. This site exists for educational purposes only. Always verify API behavior against the official Google documentation before making production decisions.