Free-tier limits: the monthly inference ceiling and 2 free premium 3D generations
The Free plan gives you the full engine at $0, with sensible caps on HIIE-managed resources. Here's exactly what those limits are.
The $2/month managed-inference ceiling
Free accounts have a hard managed-inference ceiling of $2 USD per month (200 credits). Once you reach it, you can't run more managed inference that month — you'd need to subscribe to a paid plan, buy a top-up, or bring your own key. This ceiling is enforced server-side and can't be changed from the browser.
2 free premium 3D generations per month
The premium Meshy text-to-3D path (realistic, textured, print-ready models) is the most expensive managed resource, so the Free tier includes 2 premium generations per month, counted across all your projects and tracked server-side in a CAD jobs registry. Each generation also debits 75 credits from your balance; a failed job does not count against the cap and its debit is refunded automatically.
The HIIE Engine has no count cap
The HIIE Engine CAD path (the build123d vision-quality loop that produces STEP, STL, and GLB) has no monthly count cap — each generation meters a small flat rate (about 10 credits), and it remains Camelia's default, preferred CAD tool. So you can keep generating engine designs even after using both monthly premium generations.
Bringing your own keys
If you add an OpenRouter key, your inference runs are unmetered ($0 in the ledger) and the $2 managed ceiling doesn't apply, since your own key carries the cost. If you add a Meshy key, premium 3D generations run on your own Meshy account — no 75-credit debit and no 2-per-month cap. HIIE Engine generations still meter their small flat rate, since that service runs on HIIE infrastructure.