Bet (app)
1 language| Type | Prediction market |
|---|---|
| Replica of | Polymarket |
| Developer | David |
| Written in | Next.js, Hanson's LMSR pricing engine, fast-check property-based tests, in-memory store |
| Tests | ~664 unit/property/route tests |
| Built with | A 14-task plan: implementer + independent reviewer + fix loop per task |
| Repository | ../bet |
| Website | https://bet-david.vercel.app |
Bet is a play-money prediction-market application, developed in the bet folder of the Replicates repository, scoped to a friend group rather than the general public. Each market carries an embedded group chat, alongside a public, read-only Explore surface styled after a Polymarket/Kalshi hybrid.
Unauthorized reads of a market return a 404 status rather than a 403, because a 403 response would confirm the market's existence.
Overview
The store is in-memory and resets on a cold start. The application has no password authentication.
Pricing engine
Markets are priced with Robin Hanson's logarithmic market scoring rule (LMSR),[1] expressed as C(q) = b·ln Σ exp(qᵢ/b), rather than an order book. The project describes the rationale as: “a CLOB with six friends is an empty book.” Three pricing engines use a single shared interface: LMSR, fixed odds, and parimutuel.
Development
The replica carries ~664 unit/property/route tests, guarded in part by property-based tests written with fast-check that check pricing invariants; one round-trip property was strengthened after a bug was found in which Math.abs had been masking a sign-flip. It was built from a 14-task plan: implementer + independent reviewer + fix loop per task.
See also
References
- Software replicas
- Prediction markets