The Bullpen referral code is bull20. Enter it at sign-up on app.bullpen.fi and it unlocks cashback rebates plus up to 20% of your trading fees back on trades placed through the terminal, whether you're trading Hyperliquid perps and spot, Solana tokens, or Polymarket prediction markets.

Bull20 is tied to a specific invite link, bullpen.fi/@bull20. Sign up through that link and the code fills in automatically, or type bull20 into the referral field yourself during setup. Once it's attached to your account, it stays there permanently, and the platform advertises the fee discount as its headline benefit for this code. Note the wording: 20% is a ceiling the platform advertises, not a flat rate guaranteed on every single trade or market.

Go to app.bullpen.fi or open bullpen.fi/@bull20 directly. Connect your wallet, since Bullpen uses wallet-based sign-in rather than email and password. Look for the referral field in the initial setup flow and type bull20 exactly, lowercase, no spaces, if it hasn't pre-filled. Finish the rest of signup, then fund your account and place a trade to start generating the rebate. The field only appears once, at signup, so don't skip it expecting to add the code from settings later.

Bull20 doesn't unlock features you'd otherwise be blocked from; you get full access to Hyperliquid, Polymarket, and Solana trading with or without a code. What changes is the cost of trading. With bull20 attached, a portion of the fees you'd pay anyway comes back to you as cashback and a fee rebate up to 20%, instead of staying with the platform in full. It's free to enter and adds no cost of its own. Trading also counts toward Bullpen's $BULL points program and related Hyperliquid XP and HyperUnit rewards, whether or not you used a referral code, so bull20 doesn't affect that eligibility either way.

There's no publicly confirmed way to attach bull20 to an account that already exists without a code. Referral attribution happens at the moment of signup, so enter it before you connect a wallet for the first time rather than planning to fix it afterward.

One risk note worth keeping in mind: Bullpen is a non-custodial terminal, so you hold your own wallet and your own responsibility for it, and nothing about a fee rebate or points program reduces the actual financial risk of trading perpetual futures or prediction markets. Cashback lowers your cost of trading; it doesn't guarantee an outcome or protect against losses. Verify the code is still active at bullpen.fi/@bull20 before you sign up, since referral terms on trading platforms can change.

Full walkthrough: Bullpen Referral Code bull20: Cashback Rebates and 20% Fees Back