How coins work

Coins are what you spend on the platform. They do not pay for client runtime.

Running a client costs a plan slot, not coins. A client starts if your plan has a free slot and is refused if it does not. There is no hourly meter, no activation fee, no per-action charge, and no way to pay your way past the slot count.

What coins buy

Purchase	What you get
A flow from the Flow library	A permanent licence to a paid flow, attachable to as many of your clients as you like.
Listing a flow	A one-time fee that keeps your own flow, or a bundle of flows, in the Flow library for good.
A sponsorship slot	One of a handful of front-page positions, won at the weekly auction or booked by the day.
A flow request reward	Held when you post a flow request, paid to the author you pick.
A dedicated IP	An address of your own for a month. See dedicated IPs.
A rented client slot	One more running client for a fixed number of days. See slots.
A collaborator	Inviting a second or later person to something you share. See what sharing costs.
Avatar items	Items, sets and event gifts for your avatar.

That is the whole list. If something is not on it, coins are not involved.

Where coins come from

Source	Kind
Your plan's monthly allowance, on a plan that includes one	Plan grant
A bundle you buy	Purchased
The daily streak	Free
Offers on the Overview	Free
Badges, gifts you open, and coupon codes	Free
Invites: when someone you invited takes a paid plan and keeps it through a short hold, you both get coins, up to a cap per account	Earned
Your share of what people paid for your flows	Earned

The three kinds

Coins are not all the same, because the platform owes something different for each.

Kind	Where it comes from	Expires
Free	The daily streak, offers, badges, gifts and coupon codes. Minted, not bought.	After a long stretch of inactivity
Earned	Invite rewards, and your share of what people paid for your flows.	After a long stretch of inactivity
Purchased	Bought with real money, plus coins CubeMind sends you directly.	Never

Spending always takes the most perishable first: free, then earned, then this cycle's plan grant, then purchased. You never lose coins you paid for while coins you were given sit unused.

A refund puts coins back in the same kind they came from. Buying a flow with streak coins and getting a refund gives you streak coins back, not permanent ones.

Expiry

Free and earned coins expire after a long period with no sign-in. Purchased coins never do: you paid for those, and taking them back would be taking payment for nothing. You get a warning well before anything expires, and signing in is enough to reset the clock.

Running out

Nothing stops. A zero balance means you cannot buy or rent anything on the list above until you top up. Your clients carry on running, because their slots are paid for by the plan and have nothing to do with this balance.

Frozen accounts

If a card payment is disputed after coins were issued for it, those coins are pulled back, even if they have been spent, which can leave the purchased balance negative. While it is negative the marketplace side of the account is frozen: no buying, listing or bidding. Running clients and licences you already hold are untouched. Topping up enough to clear the negative balance lifts the freeze.