Tape

Tape: returns you can't fake

Copy trading for tokenized stocks, where every return is proven on-chain. Managers run public vaults of Robinhood Stock Tokens. A Rust engine on Arbitrum Stylus stamps every return on an append-only tape. Followers copy with USDG and can leave in kind at any time.

🔗 Live app: tape-verified.vercel.app.
💻 Code: github.com/codeswithroh/tape-verified

The problem

Stock tips are sold on screenshots. Anyone can post "+312% this quarter" and nobody can check it. Regulators across Asia are now acting on this:

• India: SEBI bars unregistered finfluencers from making return claims, and launched PaRRVA, an agency whose job is to verify past returns.

• Singapore: MAS rules on digital advertising now reach the content creators who promote financial products.

• Robinhood: verified, copyable trades (Robinhood Social) exist, but only inside its US app. Robinhood Stock Tokens reach 120+ countries where that app isn't available.

The demand for verified returns is real, and it isn't met where stock tokens are actually sold.

The solution

On Tape, the chain is the verification agency.

• Public portfolio vaults. A manager runs a portfolio of stock tokens and USDG. Every trade goes through the vault, so nothing can be hidden, backdated or cherry-picked.

• The tape (Rust on Stylus). Every checkpoint appends the vault's net-of-fee share price to an append-only record. Total return, max drawdown, volatility and Sharpe are computed on-chain, so any contract can gate on them.

• Copy in one click. Followers deposit USDG and receive shares at the Chainlink-priced value.

• Leave anytime, in kind. Redemption pays a pro-rata slice of every holding. It reads no oracle and needs no manager, even on a weekend.

Why followers can trust a stranger's vault

Built with Arbitrum

• Arbitrum Stylus: the track-record engine is 13.4 KB of Rust. Its metrics() is up to 1.6× cheaper than a bit-identical Solidity reference, and the advantage grows with history length.

• Robinhood Chain (an Arbitrum Orbit chain) and Arbitrum Sepolia: the same contracts are deployed at the same addresses on both.

• Paxos USDG is the deposit asset, the quote asset for every trade, the cash leg of every portfolio and the unit of every fee.

• Chainlink stock feeds price everything, and the vault trades through Uniswap v3.

Proof

• Same code, real market: the testnet contracts also ran against Robinhood Chain mainnet state (real USDG, NVDA/AAPL/TSLA tokens, Chainlink feeds and Uniswap pools). Buying $18k of stock cost 19 bps vs the oracle.

• 32 Foundry tests (unit, fuzz, invariant) plus 5 Rust tests. The invariants held across 65,536 random calls.

• Four demo vaults replayed 69 trading days of real mainnet prices through the contracts, and are labelled "Replay" in the app.

Key contracts (identical on Robinhood Chain testnet 46630 and Arbitrum Sepolia 421614)

• Stylus PerfEngine: 0xEF9611533407D99e9c287480955A2923d8d6cC96

• TapeFactory: 0x031cBa7db6325aaA1D81533573D2A33B0fcC16Db

• AssetRegistry: 0x7fc05a6FE237D5690886EC95BEFdaeFD3cAaF136

Everything in Tape was written during the buildathon, from an empty repository.

1. Research and de-risking (before any code)

• Read the Robinhood Chain docs, the buildathon terms and every project in the gallery to avoid overlap.

• Checked every dependency against live chain state:

  • Stylus deploys on Robinhood Chain.

  • Robinhood Stock Tokens transfer freely to contracts.

  • Chainlink stock feeds update 24/5 and already include the ERC-8056 multiplier.

  • Uniswap v3 stock/USDG pools have real depth: a $5k round trip cost 0.1%.

2. Smart contracts and the Stylus engine

• Contracts: TapeVault, TapeFactory and AssetRegistry in Solidity, plus the PerfEngine in Rust on Arbitrum Stylus and a bit-identical Solidity reference.

• Tests: 32 Foundry tests (unit, fuzz, invariant) and 5 Rust tests.

• Mainnet fork suite: runs against real USDG, stock tokens, Chainlink and Uniswap; measured 19 bps execution cost.

• Security fix found in testing: keeping entry fees inside the vault let a manager inflate their own track record by churning deposits. Fees now go to a treasury, and an invariant enforces it.

3. Deployment

• Deployed to Robinhood Chain testnet and Arbitrum Sepolia at identical addresses.

• Robinhood testnet has no stock tokens, feeds or Uniswap, so I deployed stand-ins with the mainnet interfaces. A serverless relay copies live mainnet Chainlink prices into them in one batched transaction.

• Seeded four manager vaults on each chain by replaying 69 trading days of real mainnet prices through the contracts.

4. Product

• Built a landing page and an app with five screens: Discover, Vault, Portfolio, Manage and Launch.

• Charts include an equity curve with one tick per on-chain checkpoint, an underwater drawdown chart, a risk/return map, and a look-through portfolio view.

• Added a one-click Demo wallet funded by a server-side faucet, so judges can try the full flow without bridging.

• Deployed on Vercel and tested every flow end to end on the live site: copy, exit in kind, launch a vault, trade, stamp a checkpoint.

5. Benchmarks and materials

• Stylus vs Solidity gas benchmark: metrics() is 1.11× cheaper at 30 checkpoints and 1.60× at 300.

• Demo video, README with screenshots and an architecture diagram, and submission assets.

Not raised. Self-funded and pre-seed. Tape was built from scratch during the buildathon and has taken no outside capital so far.