Market data systems · 2026 · Solo — public-API research, financial-model design, safety architecture, interaction design, implementation, verification
Seamline
A paper-only sports-value operator that separates reference marks from executable depth, prices uncertainty explicitly, and makes its trading boundary structural.
The problem
Prediction-market prices look comparable before they are comparable. Venue payloads encode outcomes, books, identifiers, fees, and event groupings differently; discovery prices may be reference marks rather than executable quotes; and apparent cross-venue disagreement can disappear after fair-line uncertainty, depth, costs, or exposure limits. Seamline turns those failure modes into visible gates instead of presenting a dashboard that implies executable edge.
Architecture
Key decisions
Never relabel a reference mark as executable
Gamma outcomePrices remain display-only marks. A selected live contract must hydrate through the venue order-book route, expose a fresh ask and observed size, and cover the requested notional before paper eligibility can pass.
Fail closed on incomplete economics
The fair line requires three valid two-way books. Fees are never silently generalized across products: both venues require an operator estimate verified for the selected market, while model error, slippage, stale data, and cumulative event exposure remain explicit gates.
Make paper-only a missing capability
The application has no credential field, wallet connector, signer, authenticated adapter, order payload, deposit path, withdrawal path, or exchange write route. Its health contract reports paper-only mode and liveExecution false.
Verify the boundary across implementations
The local release gate passed 33 unit/integration tests and 18 production-browser checks across Chromium, Firefox, and mobile WebKit, with lint, TypeScript, production build, automated accessibility, dependency audit, fixed-host review, security headers, live public search/order-book probes, legacy-audit hydration, and temporary-port shutdown checks.