The estimator is a config value

apps/functions/src/providers/ holds one file per provider behind a single provider interface. Quota, caching and the app never know which one ran. Adding a third is a new file plus one line in providers/index.ts, never a branch inside a call site.

Free tier by default

VISION_PROVIDER defaults to gemini: vision, roughly 1,500 requests a day, no card. That is enough to run the harness and an early beta at zero cost.

It is also why FREE_TRIAL_SCANS is a lifetime allowance rather than per-day: a free user who never converts costs real tokens here. See plus-subscription and scan-cost.