Overview
On-demand usage is a pay-as-you-go option for all AI features in Heptabase. Once your free credits and included plan credits are used up, you can enable on-demand usage to keep using AI features and pay based on actual usage.
Enable on-demand usage
On-demand usage is available to eligible paid subscriptions; it cannot be enabled during a free trial. To use it before your trial ends, start your paid subscription first.
Go to Settings → AI features and enable on-demand usage.
Set a monthly spending limit to activate it.
Set a spending limit
The monthly spending limit caps your additional on-demand charges for the month.
For example, if your limit is set to $10, your pay-as-you-go charges for that month will stay at or close to $10.
Note: usage already in progress can make the final amount slightly exceed your limit. Long-running AI Agent and AI Tutor tasks check available allowance between steps and may stop before completing the whole task. Some tasks may stop slightly before the limit to leave room for their next step. Reaching the limit does not guarantee that an entire interaction will finish.
Understand your bill
On-demand usage is billed based on actual usage. It is not a prepaid package of credits. You do not buy a fixed batch of extra credits in advance. Instead, you use AI first and are charged afterward based on what you actually used.
Unpaid on-demand usage is collected by a scheduled billing process. Around the $10 threshold, usage may be billed during the cycle; any remaining unpaid usage is settled after the cycle ends. Crossing $10 does not cause that AI interaction to charge your card immediately. Collection timing can be delayed by the interval between charges or proximity to the end of the cycle.
An interim payment reduces the unpaid amount that will be settled later; it does not reset your monthly spending allowance. Previously billed usage is deducted from the final settlement so it is not billed twice.
Example: If a period has $12.50 of on-demand usage and an interim invoice already covered $10, the remaining usage to settle is $2.50, before applicable taxes or account balance adjustments. The $10 payment does not give you another $10 of spending allowance.
Common questions
Does on-demand usage expire?
No. On-demand usage is not a monthly bundle that needs to be used up. It is simply pay-as-you-go billing for additional AI usage. You are charged only for what you use, up to your monthly spending limit.
Can I prepay for extra credits?
No. On-demand usage is not a prepaid credit pack — there is no way to buy a bundle of credits ahead of time. You only pay for what you actually use, up to your monthly spending limit.
When do Basic models use on-demand billing?
On Premium and Premium+, after your included AI credits run out:
Basic models can still read, search, and answer for free. A read-only conversation in this mode remains free.
Creating or editing content requires on-demand usage to be enabled with sufficient remaining allowance. That run consumes on-demand usage only if the agent successfully completes a content change. Without available on-demand usage, Basic models cannot create or edit content.
Does the rate depend on my plan?
Yes. Premium+ has a lower on-demand rate than Pro and Premium for the same AI usage—approximately 33% less. A plan change affects subsequent usage; it does not reprice usage already recorded. Check Usage for the charges recorded for your account.