lovable-ethereum-sepolia

name	lovable-ethereum-sepolia
description	Ship a Lovable app on Ethereum Sepolia — Privy Google/email sign-in with embedded wallet, native Privy gas sponsorship (no ZeroDev), Hardhat deploy + Etherscan verify, optional IPFS via Pinata. Use when the user asks for a Sepolia demo, testnet contract, sponsored-tx UX on Ethereum, or timestamp / provenance / mint flow on Sepolia.

Lovable · Ethereum Sepolia

Everything needed to ship a working Sepolia demo: Google sign-in via Privy, embedded wallet, native Privy gas sponsorship (no ZeroDev, no smart wallets), one Solidity contract deployed + verified on Etherscan, optional IPFS pin via Pinata. Chain id 11155111.

Non-obvious rules (get these wrong and it silently fails)

1. Sepolia does NOT need ZeroDev or smart wallets. Privy's native gas sponsorship covers Sepolia. Enable it in the dashboard and pass sponsor: true per call — that's it. Don't wire SmartWalletsProvider or a paymaster URL.

2. Dashboard config (one-time, user). Privy dashboard → Gas sponsorship → App pays → add chain Ethereum Sepolia → toggle Allow transactions from the client ON. Native sponsorship requires TEE execution, which is the current Privy default. Without any of these, sendTransaction hangs or falls back to user-paid with a non-zero fee.

3. Both fields on every call:

   sendTransaction(
     { to, data, chainId: 11155111 },
     { address: embedded.address, sponsor: true }
   );
   

   Approval sheet still appears — fee reads US$0.00 — user taps Approve once. There is no supported way to skip that sheet on the embedded-EOA path.

4. Do NOT pass uiOptions: { showWalletUIs: false }. Privy aborts the send with signal is aborted without reason. This is the #1 way to waste an hour thinking sponsorship is broken. Just remove the field.

5. Wrap sendTransaction in a 45s Promise.race timeout whose reject message names the exact dashboard toggles. Without it, a misconfigured dashboard hangs the UI forever with no diagnosable error. Reference shape in references/privy-sponsored-tx.md.

6. SSR-safe Privy mount is mandatory. lazy(() => import("./privy-client-entry")) inside <ClientOnly> + <Suspense>. Never import @privy-io/react-auth at module scope of a route file — SSR bundle explodes. See evvm-privy-integration skill for the full mount pattern.

7. Pass chainId: 11155111 on every sendTransaction. Sponsorship is configured per-chain in the dashboard; if you omit chainId the embedded wallet may default to mainnet and the sponsor rule does not match. You do NOT need defaultChain/supportedChains in the PrivyProvider config — if you set them anyway, use viem's sepolia object, never a { id, name } as never stub.

8. viem event reads on the free public RPC rate-limit past ~9000 blocks. Cap getLogs ranges (fromBlock = head - 9000n) or wire an Alchemy URL. For production reliability keep both: import.meta.env.VITE_SEPOLIA_RPC_URL in the browser, SEPOLIA_RPC_URL in Hardhat.

9. Contract deploys use a plain Node EOA, not sponsorship. Hardhat reads METAMASK_PRIVATE_KEY + SEPOLIA_RPC_URL. Fund from https://sepoliafaucet.com or Alchemy's faucet. Sponsorship only covers user-triggered txs at runtime.

10. Etherscan v2 verification for Sepolia uses chainid=11155111 in the URL query string, not the POST body. One ETHERSCAN_API_KEY covers every chain via v2. Unlike Fuji (Snowtrace + Etherscan) there is no second explorer to submit to. See references/hardhat-etherscan-verify.md.

11. x402 / EIP-3009 signing MUST use an external MetaMask EOA, not the Privy embedded wallet. Sepolia's Circle USDC v2.2 uses SignatureChecker, which rejects EIP-7702 delegated EOAs (Privy embedded wallets are delegated by default). Force connectWallet() and sign with the external provider. Full 13-rule recipe + self-hosted facilitator in references/x402-paywall.md.

When to use

User asks for…	Use this skill
A Sepolia demo / testnet dApp	Yes
Gas-sponsored UX on Ethereum L1 (no popup fee)	Yes
Timestamp / event-log / provenance contract on Sepolia	Yes
ERC-721 mint with IPFS-backed metadata on Sepolia	Yes (pair with references/pinata-ipfs.md)
x402 pay-per-call USDC paywall on Sepolia (self-hosted facilitator)	Yes — see references/x402-paywall.md
Sepolia → L2 bridging / CCTP	No — see dance-ucp-arc-circle
Mainnet payments	No — use payments--enable_*
A different testnet (Base Sepolia, Fuji, Amoy, Robinhood, Tempo)	Use the matching chain-specific skill

Required secrets

Name	Purpose	When
PRIVY_APP_ID (+ VITE_PRIVY_APP_ID)	Google/email login + embedded wallet	Always
METAMASK_PRIVATE_KEY	Hardhat deployer EOA	Only if you deploy a contract
SEPOLIA_RPC_URL (+ VITE_SEPOLIA_RPC_URL)	Alchemy HTTPS URL	Recommended; free public RPC works but rate-limits
ETHERSCAN_API_KEY	Etherscan v2 verify	Only if you deploy a contract
PINATA_JWT (+ VITE_PINATA_JWT)	IPFS pinning	Only if the app pins media/metadata
RELAYER_PRIVATE_KEY	x402 facilitator EOA (pays gas, receives USDC)	Only for the x402 paywall demo; fund with Sepolia ETH

Do NOT add any ZeroDev / bundler / paymaster keys — native Privy sponsorship handles it.

Reference index

• references/privy-sponsored-tx.md — canonical privy-client-entry.tsx and privy-root.tsx, dashboard walkthrough, error table
• references/hardhat-etherscan-verify.md — deploy script, verify CLI + curl fallback, src/data/contract.json shape
• references/pinata-ipfs.md — browser upload, gateway URLs, ERC-721 metadata pattern
• references/failure-modes.md — symptom → cause → fix table
• references/x402-paywall.md — self-hosted x402 v2 facilitator, EIP-3009 signing via external MetaMask (embedded wallet is rejected), 13 rules + full symptom table

Related skills

• evvm-privy-integration — SSR-safe Privy mount pattern (deeper coverage of PrivyRoot + ClientOnly)
• robinhood-lovable — Hardhat + Blockscout verify + Pinata + smart-wallet path (use for Robinhood testnet, not Sepolia)
• lovable-avalanche-x402 — Etherscan v2 multi-verifier pattern (Fuji + Routescan)
• lovable-tempo — TIP-20 pay pattern for Tempo, similar Privy sponsorship shape

Canonical minimal src/data/contract.json

{
  "address": "0x…",
  "deployTx": "0x…",
  "chainId": 11155111,
  "network": "Sepolia",
  "explorer": "https://sepolia.etherscan.io"
}

The UI reads contractCfg.address + contractCfg.chainId from this file and links every tx via ${contractCfg.explorer}/tx/${hash}.