Find and revoke old unlimited token approvals
Intermediate12h1–2
ViemWagmiNext.js
17/20Transaction Simulation Before Signing
See exactly which tokens leave your wallet before you sign.
Advanced24h2–3 people17/20 fit
Build Transaction Simulation Before Signing for everyday wallet users in ~24h with 2–3 people. Stack: Foundry + Viem + Next.js.
Why it wins: Protects users from the most common web3 scam.
Build flow
01 · Problem
Users sign malicious transactions that drain wallets.
02 · Solution
Fork the chain locally, simulate the transaction and show token movements and approvals with warnings for risky patterns.
03 · Build
- 1Run a forked node
- 2Simulate the tx
- 3Diff balances
- 4Show warnings
04 · Demo
Simulate a drainer transaction and show the red warning.
MVP checklist
- Local fork
- Token diff
- Approval warnings
- Plain summary
Tech stack
| Tech | Role | |
|---|---|---|
| Foundry | Contract testing + deploy | Chain |
| Viem | Ethereum client | Chain |
| Next.js | Frontend + API routes | Web |
Reference repos
Open-source projects you can build on. Links checked 2026-10-31.
Related ideas
More Web3Explain what an off-chain signature request actually allows
Intermediate12h1ViemLLMNext.js17/20Recover a wallet through trusted friends instead of a seed phrase
Advanced28h2–3Account AbstractionSolidityWagmi17/20