Sume video poll usage.cost: reserved while running, captured at end

usage.cost on a Sume /v1/videos poll is in dollars and is the Sume billable amount: list price times 1.25, rounded up to a cent. While the job is in flight it shows the amount reserved at submit, and after the job settles it shows what was captured. Read it as the cost of that clip, not as the account balance.

The arithmetic

Take wan-3.0 at 720p. The catalog lists it at $0.10 per second at that resolution. For a 10-second clip the list is $1.00, Sume bills 1.25 times that, so $1.25, and the cents round up to 125. At 15 seconds the product is $1.875, which rounds up to $1.88 (188 cents).

For models priced per video token, such as Seedance 2.5, the rule is the same (list x 1.25, ceil to cents), but the list amount comes from the token count, so use the grid values in the catalog instead of computing by hand. Seedance 2.5 at 720p, 9:16 and 10 seconds is 578 cents.

Reading it in code

The field can be absent. A submit response never has it, and a poll only carries it once an amount exists. Treat null and a missing key the same way. Keep money as integer cents on your side, so 0.63 does not drift through a float.

from decimal import Decimal

def cents(poll: dict) -> int | None:
    usage = poll.get("usage") or {}
    cost = usage.get("cost")
    if cost is None:
        return None
    return int((Decimal(str(cost)) * 100).to_integral_value())

# {"status": "in_progress", "usage": {"cost": 1.25}}  -> 125 (reserved)
# {"status": "completed",   "usage": {"cost": 1.25}}  -> 125 (captured)

What to show a customer

If your app resells clips, show the amount only when the job is completed. Before that, show nothing or a clearly labelled hold, because an in-flight amount is a reservation. Round for display with the same rule Sume uses (up to the cent), so your invoice lines match the poll.

If you charge a fixed price per clip, compare it with the usage.cost of the cheapest and the most expensive model you allow, and set the price from the high end.

Why the number can move

For a clip that succeeds, the reserved and captured amounts are normally the same, but read the field again after completed instead of caching the first value. Check the usage endpoint or the balance for the settled picture of spend, and use usage.cost for per-clip display only.

Reservation needs enough balance at submit. If the balance is short, the submit fails with 402 insufficient_credits; see the credits table. For the same arithmetic on a different clip, try the Sora replacement price table.

• Do not add up usage.cost of in-flight jobs as spent money.
• Treat a missing usage as unknown, not as zero.
• Show cost only on completed jobs in a customer-facing UI.