Essay

The Stock Exchange That Had No Building

For decades, New York's second stock market traded in the open street. Curbstone is that market on-chain, where it never has to close.

Go to Broad Street in Manhattan and look up. The windows above the pavement are ordinary office windows now. A century ago, clerks hung out of them and threw hand signals down to the men standing in the road.

Those men were the curbstone brokers. They had no exchange floor, no building, no roof. They traded standing on the curb, in the rain and the snow, shouting across traffic. The street was so loud that they invented a sign language to get orders from the clerks in the windows above: fingers for price, palms for buy and sell, a whole grammar worked out in the air because nobody could hear a thing.

It was not a sideshow. The curb market listed what the big exchange would not touch. Young industrials, oil wildcatters, mining ventures, the companies that were too new or too strange to pass the committee upstairs. It traded for decades in the open, organized itself formally in 1911, and finally moved indoors in 1921. It kept the name anyway. The New York Curb Exchange only became the American Stock Exchange in 1953.

The lesson of the curb is not that the street was romantic. It is that a market forms wherever people want to trade, and the building arrives afterwards, if it arrives at all.

Robinhood Chain just put US equities on-chain. Curbstone is the market that forms around them.

What is actually on this chain

Robinhood Chain is an Arbitrum Orbit network, chain id 4663. On it sit Robinhood Stock Tokens: ERC-20 tokens, eighteen decimals, issued by Robinhood Assets (Jersey) Limited against the real underlying shares. Corporate actions are handled on-chain. A split or a dividend adjustment moves a multiplier on the token contract rather than silently changing anyone's balance.

There are 195 of them in the official registry today. Apple, NVIDIA, Microsoft, Tesla. ETFs like SPY, QQQ, GLD and SGOV. And a handful of things you cannot buy in a normal brokerage account at all, including SpaceX.

That is a real primitive. But owning a theme with it is tedious. If you want the seven American mega caps, you make seven purchases, you hold seven positions, and every time you want to add to the position you do it seven more times. Every rebalance is seven transactions. Nobody does this for long.

One token, seven companies

A Curbstone vault holds a fixed list of stock tokens in fixed amounts and issues a single ERC-20 share against them.

You hand the vault the underlying tokens, it mints you a share. You hand back the share, it returns the exact underlying. That is the whole mechanism. There is no NAV calculated by a server, no manager deciding what to sell, no redemption queue and no promise to honour later. The basket is a claim on tokens that are sitting in the contract right now, and the contract hands them over on demand.

Composition is set when the vault is created and cannot be changed afterwards. Not by us, not by a vote, not by anyone. If you buy cCHIP you know exactly what you are holding this year and next year.

Six baskets at launch:

cFRNT is the one worth staring at. SpaceX, Rocket Lab, IonQ, CoreWeave, Rigetti and Nebius in a single token. There is no brokerage on earth where you can buy that sleeve in one click.

Every component has a price feed, or it does not get in

Here is the rule that shaped the entire protocol: a stock token cannot enter a Curbstone vault unless it has a Chainlink price feed on Robinhood Chain. The factory checks for the feed and reverts if it is missing. There is no override.

That is a hard constraint. Of the 195 assets in the registry, 37 have a feed today. We built six baskets out of 37 assets instead of 195, and we think that was the right trade.

Because of it, a vault can answer the question "what are you worth" from inside the contract. navPerShare() reads the feeds, checks each one for staleness, and returns the value of one share in dollars. Nothing about that number comes from a website, an API or a backend that could go down or lie. If a feed is stale, the call reverts rather than returning a number that looks fine and is not.

Most on-chain index products quote a price their own front end calculated. Curbstone quotes a price its own contract calculated, and you can read it yourself with any node.

The oracle does one more thing worth saying out loud: it never prices a mint or a redeem. Those are settled in units of the actual tokens, one for one. The oracle exists so you can value a position, not so a contract can decide what to charge you. An oracle that cannot move your money cannot be manipulated into moving your money.

The fee that reads the room

Every automated market maker charges the same fee whether the market is asleep or on fire. That is backwards, and it is the reason liquidity providers lose money on quiet days and lose more on violent ones.

Curbstone ships a Uniswap v4 hook.

Before every swap, the hook looks at how far the pool has moved since the previous trade and sets the fee from it. A calm market pays the base rate of 0.30%. A market that just jumped pays more, scaled to the size of the move, up to a ceiling of 1.00%. Then it decays back to base over ten minutes. Nobody votes, nobody files a proposal. The fee is a function of what just happened.

The people who get charged the surge are the ones trading into a dislocation. The people who receive it are the ones providing the liquidity that absorbs it. That is the correct direction for that money to flow.

The hook also takes 0.10% of swap output to the protocol treasury, in the same transaction, with no separate claim step.

Uniswap v4 reads a hook's permissions from the bits of its address, so the deployment script mines a CREATE2 salt until it finds an address that encodes exactly the four permissions this hook needs and nothing else. You can verify from the address alone that it cannot do anything it has not declared.

$CURB, and what locking actually buys

$CURB is the protocol token. Fixed supply, created on Pons.

It is not a governance badge and it does not sit in your wallet doing nothing. You lock it, for anywhere between one week and fifty two, and the lock length decides its weight:

weight = amount × (1 + 3 × weeks / 52)

One week counts once. Fifty two weeks counts four times. Two things follow from your weight:

It cuts your fees. Minting and redeeming a basket costs 0.50%. Weight takes up to half of that off, in three tiers.

It pays you. Protocol revenue flows to the treasury, and 70% of it is pushed to lockers, split by weight. Not in freshly printed tokens. In whatever the treasury actually collected, which is the stock tokens and the swap output the protocol took in. If nothing is earned, nothing is paid. There is no emission schedule to inflate your way out of a quiet month.

The accounting is the standard accumulator pattern, so a deposit made after revenue arrives earns nothing from it. You are paid for the period you were actually locked.

Where it stands

The site is live at curbstone.finance, showing all 195 assets with live Chainlink prices and the current value of every basket, refreshed every minute. The prices on that page are read from the chain in your browser, not served from a database.

Six contracts carry the protocol: an oracle, a vault, a factory, staking, a treasury and the hook. They are written, they compile, and the test suite covers oracle staleness, basket value, mint, redeem, the fee ceiling, feed-gated listing, lock weights, discounts, lock enforcement and revenue splitting. They go on-chain alongside the token.

Curbstone is independent. It is not affiliated with Robinhood Markets, Inc., Uniswap, Chainlink, Pons Labs or any company whose logo appears on the site. Logos are used for identification only.

One more thing about the curb

When the curb brokers finally moved indoors in 1921, they did not stop using the hand signals. The windows were gone, the street was gone, but the language came inside with them and stayed in use on the floor for years.

Markets do that. The venue changes, the behavior survives. The curb was never the curbstone. It was the people who showed up to trade whatever the building would not list.

The building is on-chain now. Everything else is the same.

$CURB launching soon on @ponsdotfamily