BUILT ON MONAD  ·  SPARK HACKATHON 2026

Send tokens.
Change your mind.

Every transfer holds in a safety window.
Cancel before the recipient claims — full refund, no questions asked.

Native MON ERC-20 tokens 15 min – 24 hr windows
Outbox
3 pending
↗ 0.25 MON · 14m left
callback://transfers
Your Transfers + New
2.5000 MON
→ 0x9f3a…4B2c
Pending
100.0 USDC
→ 0xAb2f…9E1d
Claimed
0.8200 MON
→ 0x7c4E…2Fa0
Pending
Safety Window
23m 14s
remaining · can cancel
HOW IT WORKS

Three steps to
safer transfers.

No more panic after hitting send. CallBack gives you a window to course-correct.

01

Send with a window

Tokens lock in the contract — not sent directly. Pick 15 min to 24 hrs.

02

Cancel anytime

Made a mistake? Cancel before the recipient claims — tokens return instantly.

03

Recipient claims

Right address? The recipient claims from their inbox. Window closes, transfer finalises.

WHY CALLBACK

Built for real people
making real mistakes.

Full refund on cancel

Cancel before the recipient claims and every token comes back. No fees, no slippage.

Configurable windows

15 min for small transfers. 24 hrs for large amounts. Or set any custom duration.

MON + any ERC-20

Works with the native gas token and any ERC-20 on Monad. One contract handles all.

Non-custodial

The smart contract holds your tokens. No admin keys, no upgradeable proxy, fully on-chain.

Monad fast

~0.5s block time. Your cancel lands before you second-guess it. Cheap gas too.

Inbox for recipients

Recipients see incoming transfers in their inbox. Claim on their own time, before it expires.

Protocol transfers
~0.5s Monad block time
100% Non-custodial
2 Tokens supported
GET STARTED

Ready to send
with confidence?

Connect your wallet and make your first
cancellable transfer in under a minute.

Launch App