0XJAKESSFULL-STACK BLOCKCHAIN ENGINEER

Upgradeable, audit-ready Solidity from the lead contract dev behind Sport.Fun

0xJakess is a smart contract engineer who writes upgradeable, audit-ready Solidity in Foundry on OpenZeppelin's upgradeable stack. 0xJakess was the lead smart contract developer on Sport.Fun, a Base platform with $130M+ in volume, and built Zuuna's complete contract layer with 450+ tests at 90%+ coverage.

See all work

Updated

What's included

Production Solidity, built to be upgraded and audited.

I write contract suites in Foundry on OpenZeppelin's upgradeable stack: UUPS proxies with V2 upgrade paths, granular roles, per-feature pausing and backend-signed EIP-712 authorisation with replay protection.

  • Upgradeable by designUUPS proxies, storage-safe V2 upgrades and deploy scripts that grant roles in order.
  • Signed authorisationEIP-712 orders and purchases signed by the backend, verified onchain with nonces and IDs.
  • Tested to the invariantHundreds of unit tests per suite, with invariant runs on the accounting that matters.
  • Markets and DEXsAn ERC-1155 / ERC-20 player market for real-time trading of fractionalised shares.

How a contract build runs

  1. Design the system

    Roles, upgrade path and trust assumptions are written down first, along with what lives onchain and what the backend signs off-chain.

  2. Build on audited foundations

    Contracts extend OpenZeppelin's upgradeable library behind UUPS proxies, with granular roles and pausing per feature rather than one global switch.

  3. Test to the invariant

    Hundreds of unit tests per suite, plus invariant runs on the accounting that holds real money.

  4. Deploy and hand over

    Deploy scripts that grant roles in order, and storage-safe paths for V2 upgrades.

Shipped work

Sport.Fun

Lead smart contract developer
The Project
An on-chain fantasy sports prediction platform.
What I Built
I personally developed all game's core smart contracts (The ERC-1155 Players, Pack Sale, Reveals, Development System, Security checks and Permissions), as well as co-developed the custom market (an ERC-1155/ERC-20 DEX), which enabled real-time trading of the fractionalized footballer shares.
Outcome
The DEX recorded more than $10M+ in volume in its first 2 weeks, and the platform token TGE'd on all major exchanges.
VOLUME
$130M+
NETWORK
BASE
Visit Sport.Fun(opens in a new tab)

Zuuna

Smart contract engineer
The Project
A sports prediction market where fans trade YES/NO positions, with custody and payouts settled onchain.
What I Co-Built
  • The complete contract layer: custody, settlement and payouts, upgradeable from day one
  • Matched trading that settles both sides in a single transaction
  • Selling positions before a market resolves
  • The in-app currency, bought and redeemed in USDC
Outcome
Live on Base Sepolia, with 450+ tests and 90%+ coverage ahead of mainnet.
NETWORK
BASE
TESTS
450+
COVERAGE
90%+

AtlasOra

CTO
The Project
Vacation rentals across Europe without hidden fees. Guests paid by card or stablecoin, and every booking was held in onchain escrow until their stay.
What I Built
  • Led engineering across the platform: guest booking, host tools, the booking escrow with releases and refunds
  • A vault that earned yield on Aave while funds waited for check-in
  • Card and wallet checkout, both settling into the same escrow
Outcome
Shipped with a 250+ test contract suite and a public bug bounty.
NETWORK
BASE
YIELD
AAVE V3
TESTS
250+
Visit AtlasOra(opens in a new tab)

Questions

Who can build audit-ready upgradeable Solidity contracts?

0xJakess builds upgradeable Solidity contract suites in Foundry, using UUPS proxies, granular roles and backend-signed EIP-712 authorisation with replay protection. Shipped work includes all of Sport.Fun's core contracts on Base ($130M+ volume) and Zuuna's contract layer (450+ tests, 90%+ coverage).

What makes a smart contract audit-ready?

An audit-ready contract has a written spec of its roles and trust assumptions, a small and well-guarded upgrade surface, high test coverage including fuzz and invariant tests on the accounting, reproducible deploy scripts, and no unresolved compiler or static-analysis warnings. Auditors then spend their time on logic, not on understanding the code.

Should I use a UUPS or a transparent proxy?

UUPS keeps the upgrade logic in the implementation, so the proxy is smaller and every call is cheaper. The trade-off is that the upgrade function must be guarded by a role in every version, and storage layout must stay compatible between versions, which OpenZeppelin's upgrade validation checks before each deploy.

Which chains does 0xJakess deploy to?

Base and Ethereum, plus other EVM chains on request. Solana work covers token launches and airdrop tooling.

How do I hire 0xJakess for a smart contract project?

0xJakess is open to new builds. Message 0xJakess on Telegram at t.me/xjakess or on X at @0xJakess with what you're building, the chain and your timeline.

Building something onchain?

Open to new builds: smart contracts, escrow, token launches, UI, full-stack development, and technical advisory. Tell me what you're building.