The app
Credit
Top up with USDG on Robinhood Chain to open every model of both lanes, and pay each chat at the price of its model.
Credit opens every model of both lanes. You pay for it in the dashboard at dash.thinkr.sh, with USDG on Robinhood Chain, and spend it in the chat app. One credit covers both lanes.
Top up
Pick an amount
In the chat app, press Top up and pick $1, $5, or $20. The app makes your vouchers in your browser, one for each dollar.
Pay in the dashboard
The dashboard opens in the same tab. Pay in USDG on Robinhood Chain from a wallet in your browser, or from a wallet on your phone through WalletConnect.
Go back to the chat
Thinkr confirms the payment on the chain and signs your vouchers. The dashboard then brings you back to the chat app, which adds them to your credit.
A payment on a blockchain is public: anyone can see the wallet that paid, the amount, and the time. Thinkr stores the transaction hash of each payment, with the number of vouchers that it paid for and a hash of their blinded requests, and never the address of your wallet.
Blind vouchers
Your credit comes as blind vouchers, signed with the RSA blind signatures of RFC 9474. Your browser makes each voucher and blinds it before it goes to Thinkr for signing. Thinkr signs each voucher without seeing it, so a spent voucher does not show which payment bought it. The time of a purchase and of a spend, or your IP address, can still link the two in some cases.
How a chat is paid
The app trades a voucher for a balance at Thinkr's proxy, and each chat takes its cost from that balance, at the price of its model for each token in and out. Before a chat starts, the balance must cover its input and 4,096 tokens of output. When the balance runs low, the app trades the next voucher.
For your chats, Thinkr stores only a hash of the key of your balance, with its amount, and a hash of each spent voucher. It keeps no record of each chat.
Your vouchers stay in this browser
Your vouchers and the key to your balance stay in the browser where you bought them. They do not move to another browser or device.
If you clear the site data of chat.thinkr.sh, you lose your vouchers and your balance, and Thinkr cannot restore them.
Prices
The price of each model, per million tokens of input and output, is on thinkr.sh/pricing and in the model picker of the app.