how it actually works
reading the bill
the photo is shrunk on your phone before it goes anywhere — long side 1,400 pixels, which is enough to read thermal print and a tenth of the cost of sending the raw camera file. it goes to a vision model once, comes back as lines, and is thrown away. nothing keeps the image.
then hissa makes you look at it. the model is good, not perfect, and one wrong digit becomes a real argument at the table. correcting three fields is cheap; disputing a settled bill is not.
when the lines don't add up to the printed subtotal, hissa says so instead of pretending.
claiming by portion
a line for seven wraps at 6,790 tapped by seven people is 970 each. tapped by two people where one had two wraps, it's split by portions, not heads.
rounding always resolves: the last claimer on a line absorbs the remainder, so the parts add back to exactly what was printed. a group can't accidentally under-cover a line, whoever tapped it.
tax, service, discount, tip
your own number is your share of the subtotal, scaled up to the final total — so gst, service charge, discount and tip all ride along in proportion to what you ordered.
bills disagree about the order: some take the discount before tax, some after, some put service on top of both. hissa tries every order against the total printed on the bill and keeps the one that matches, down to the rupee. when a bill doesn't add up by any reading, it keeps the closest and adds the gap as its own "difference" line, so what gets split is what you actually paid — and says so.
one phone, or everyone's
five or more of you: share the link and everyone taps on their own phone at once. a smaller table can pass the phone — each person takes a turn, and the tally at the end goes to the group chat as text or a picture.
entering a bill, splitting it equally and passing the phone all work offline. reading a photo, sharing a link and joining a split need a connection.
who you are
your name, lowercased and trimmed. Faraz, faraz and FARAZ are one person, which is what makes rejoining from a second phone or after a refresh free.
the catch is honest and visible: two real people called faraz at the same table will land on one record, and you'll see it happen rather than find out later.
what the code can and can't do
let anyone at the table open the split and claim their own items.
keep out someone who has the code. treat it like the bill itself — it's on the table, not in a safe.
twenty-four hours, then the code stops working and the bill is gone.
once a split is open the bill can't be edited. a forgotten item means a second split.