A market is {id, question, resolution rule, close height, resolve height}. Prices are ticks from 1 to 99 cents. A matched YES/NO pair locks exactly 1 unit of collateral and pays 1 unit to the winning side. Each rule is a plugin implementing the Resolver trait from packages/oracle; a new market type is a new plugin.
Chain-data markets
Resolved from Zcash mainnet blocks, read by each relayer from its own lightwalletd connection (zec.rocks:443 on the demo). Anyone can recompute them.
| Plugin | Question | Rule |
|---|---|---|
nu7-activation | Will NU7 activate at height H? | YES iff block H's coinbase carries the NU7 consensus branch ID |
ironwood-pool | Will the Ironwood pool hold ≥ N notes at H? | The Ironwood commitment tree size at the end of block H |
shielded-actions | Will block H contain ≥ N shielded actions? | Sapling spends + outputs + Orchard + Ironwood actions in the compact block |
Hourly rolling market
rolling.rs makes a new market every hour of nominal block time: "Will mainnet block H contain ≥ N shielded actions?", with H one hour ahead (48 blocks at 75 s; 144 blocks at 25 s from NU7 at 3,543,405), trading closing 5 minutes before H, and N the median of the 24 blocks before the window, so YES and NO are about even. Ids are 1,000,000 + window, derived from heights only, so all three relayers make the same market without talking. Resolved rolling markets stay listed for 24 h.
Mirrored Polymarket markets
packages/plugins/polymarket mirrors a binary Yes/No Polymarket market: the same question, traded on zPredict's own private book. Each relayer reads gamma-api.polymarket.com/markets/slug/<slug> itself, checks the conditionId and that the outcomes are exactly ["Yes","No"], and resolves once the market is closed and umaResolutionStatus is "resolved": YES iff the Yes outcome price is exactly 1 (a 50-50 settlement is NO). A proposed or disputed UMA answer leaves it unresolved.
The oracle for these markets is Polymarket (UMA), not chain data. The relayers attest what Polymarket published (each fetches it on its own, and the outcome is signed only if all three read the same), but nobody can recompute it from a block. A wrong or disputed Polymarket resolution is zPredict's resolution. Trading stays exactly as private as on any other market.
The relayers also fetch Polymarket's Yes price and a week of hourly history, at most every 5 minutes (reference.rs), and serve it as reference in /markets. The browser never contacts Polymarket; the app shows the market page only as a plain outbound link.
Signed outcomes
Only a resolution all three relayers computed identically is signed, FROST 2-of-3 with the escrow's key shares, as an ordinary RedPallas signature under the group key. The signed bytes are "zPredict outcome v1\n" followed by compact JSON:
{"market":1,"outcome":"yes","height":3543405,"blockHash":"…"}
{"market":11,"outcome":"no","source":"polymarket","conditionId":"0x…"}The two forms have disjoint keys, so one can never verify as the other. verifyOutcome checks them in the browser; outcome-vectors.json pins the format for Rust and TypeScript. Without a sealed key share a relayer still resolves, and the app shows "Resolved (unsigned)"; nothing is ever signed with a stand-in key.
Capacity
One clearing run has DEFAULT_MARKETS = 6 market slots. The demo uses all six: NU7 activation, Ironwood ≥ 900,000 notes, three mirrored markets on the US midterms (two House-control rows of one event and the Texas Senate race), and the hourly rolling market. The rolling generator never opens a market past the cap; a seventh open market would need a second MPC run per window. The live list is in deploy/production/relayer.toml and at GET /markets.