UMBR is live on Tempo testnet

UMBR does one job. It lets you move stablecoins on a public chain without publishing your balance, your counterparties and every amount you send. Settlement stays on the public chain and anyone can confirm the pool adds up. What they cannot do is read your finances off a block explorer.

Why Tempo

Most chains were designed around a volatile native token, and payments came later. Tempo starts from the other end. It is a payments chain where stablecoins are the main asset, and there is no separate gas token to buy: network fees are paid in a supported stablecoin. For someone sending a salary or an invoice, that removes a step that never made sense to them.

Payments are also exactly where public ledgers hurt the most. A trader can live with a visible wallet. A business that pays suppliers, or a person who gets paid, cannot. So putting a private balance on a payments-first chain is the obvious pairing.

What works today

On Moderato, with test stablecoins, you can:

• Shield a public stablecoin balance into your private balance. Your wallet stops showing it; the app shows it to you alone.
• Send privately to another UMBR user. On the explorer the payment appears as a call to the pool, with no visible amount and no visible recipient.
• Pay with a link. Make a payment link and send it however you like. Whoever opens it at /claim can take the funds into a balance only they control.
• Run payroll as one batch from your private balance, without publishing the payroll.
• Prove a single fact, such as a payment you made or a balance above a threshold, to one reader. They can check it at /verify without connecting a wallet.
• Unshield back to a public address whenever you want the money public again.

What it costs

On Tempo you pay the network fee in a stablecoin, just as you would for any other transaction there. UMBR does not add a fee on testnet. When a relayer submits a private payment for you, so your own address does not appear next to it, the relayer pays that network fee and any relayer fee is designed to be bound into your proof, so it cannot be raised after the fact. The relayer is optional: you can always submit from your own wallet instead.

How to try it

1. Add Tempo Moderato to an injected browser wallet and pick Tempo in the network menu of the app.
2. Get test stablecoins from Tempo's faucet. The testnet guide links it and lists the tokens the pool accepts.
3. Open Private balance, shield a small amount, then send part of it to a friend or to a payment link.
4. Look the transaction up on the explorer. You will see that the pool was called and a fee was paid. You will not see who was paid or how much.

Honest status

This is a testnet with test money. Contracts can be redeployed, and when that happens old test balances may be left behind. The proving keys come from a development setup, not a public ceremony, and no independent security review has been completed yet. Both are conditions for mainnet, not afterthoughts. A new pool is also a small crowd, and privacy grows with the number of people using it, so treat the link between a deposit and a withdrawal as easier to guess for now.

UMBR runs the same private core on Robinhood Chain testnet, so the app, the proofs and the SDK work the same way on both chains. If something breaks, we want to hear about it.