Add token approval / spending limits to wallet contract

[Miracle656]

Background

Currently, any transaction signed by the passkey can move any token in any amount. Production DeFi usage requires granular spending controls — e.g., approve a DEX to spend up to 500 USDC without a new biometric prompt for each swap. This is the Soroban equivalent of ERC-20's approve/allowance pattern.

What to build

Add a spending-limits system to the wallet contract: a way to pre-approve a specific spender address for a specific token up to a maximum amount, with an optional expiry.

Key files

• contracts/wallet/src/lib.rs — main wallet contract to extend
• sdk/src/useInvisibleWallet.ts — expose approve() SDK method

Suggested execution

git checkout -b feat/contract-spending-limits

1. Add a StorageKey::Allowance(spender, token) variant to the contract's key enum
2. Implement approve(spender, token, amount, expiry) — requires passkey auth
3. In __check_auth, check allowance before executing and deduct accordingly
4. Add get_allowance(spender, token) view function
5. Write Soroban tests: approve → spend within limit (pass), spend over limit (fail), expired (fail)
6. Expose approve() and getAllowance() in the TypeScript SDK

Example commit message:
feat(contracts): add token approval and spending limits with passkey auth

Acceptance criteria

• approve() requires passkey signature
• Spending over the limit is rejected by the contract
• Expired allowances are rejected
• Soroban tests cover happy path + limit exceeded + expired
• TypeScript SDK exposes approve() and getAllowance()

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Drips Wave · Complexity: High · 200 points
Comment below to request assignment. PR must include Closes #[this issue].

[Tybravo]

@Tybravo has applied to work on this issue as part of the Stellar Wave Program's 4th wave.

Hello, I am a full-stack Software Engineer with 7+ years of experience and a Blockchain Developer. New to open-source contributions and adapting very quickly, and I do like to work on the Issue.

I have strong hands-on experience building advanced, user-friendly and visually engaging frontend interfaces using React, TypeScript, and Next.js, with a focus on reusable component architecture, modern UI patterns, responsive design, state management, and performance optimization. I work across both frontend and backend systems, including backend logic, API design, database architecture, and schema modeling.

I have experience building modern, scalable web applications using React, Typescript, Next.js, Node.js, Java, Rust, and related technologies. Some relevant projects (personal and OPEN SOURCE) I have worked on include:

--> https://www.verilens.xyz/
--> https://repeasy.wal.app/
--> https://docwalrus.vercel.app/
--> https://grainlify.0xo.in/

I am comfortable working within an existing codebase or independently , following project conventions, and delivering clean, maintainable, and well-structured solutions. My GitHub repositories can speak for themselves in demonstrating my experience and consistency across different types of projects.

I am confident I can contribute effectively and deliver high-quality results.

Thank you for your time and considering my application.

Regards,
Michael

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Congratulations, @Tybravo! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on April 29, 2026.

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This issue has been completed by @Tybravo as part of the Stellar Wave Program's 4th Wave 🥳

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