Price ceiling guard: refuse a $42.65 Seedance 2.5 clip before the POST

A single parameter change can multiply a request's price. On seedance-2.5, a 10-second 720p clip bills $5.778; the same 10 seconds at 1080p bills $14.2155; 1080p at 30 seconds bills $42.6465. A script or agent that picks resolution and duration from user input can turn a typo into a bill. A ceiling check before the POST makes the worst case your choice.

A balance check is not a substitute: 402 insufficient_credits only fires when the balance runs out, and a large balance happily pays for a large mistake.

The guard

It computes the billed amount from the token formula and raises before any network call. Printed output from Python 3.14.7: 720p 10 ok 5.778, then a refusal at $14.22 and one at $42.65.

import math
DIMS = {"480p": (496, 864), "720p": (720, 1280), "1080p": (1080, 1920)}  # 9:16

def seedance_25_micros(res, secs):
    w, h = DIMS[res]
    rate = 23400 if res == "1080p" else 21400  # list micros per 1000 tokens
    tokens = math.ceil(w * h * secs * 24 / 1024)
    return math.ceil(math.ceil(tokens * rate / 1000) * 1.25)

def guard(res, secs, ceiling_usd):
    cost = seedance_25_micros(res, secs) / 1e6
    if cost > ceiling_usd:
        raise SystemExit(f"refused: {res} {secs}s is ${cost:.2f}, ceiling ${ceiling_usd:.2f}")
    return cost

for res, secs in [("720p", 10), ("1080p", 10), ("1080p", 30)]:
    try:
        print(res, secs, "ok", guard(res, secs, 10.0))
    except SystemExit as e:
        print(e)

Where to put it

Call it in the one function that builds the request, not in each caller, and put the ceiling in config. Refusing is a decision for a person or a policy, so report the number and the settings instead of silently downgrading the resolution. For the batch version, sum the guard over the whole list first and compare with your budget.