feat(predictions): add Kalshi as prediction market data source

[Rau1CS]

Summary

• Add Kalshi (CFTC-regulated exchange) as a second prediction market source alongside Polymarket
• Both sources fetched in parallel with separate Redis caching and graceful degradation
• Kalshi markets routed to the finance variant with source badge displayed on each market item

Test plan

• Run npm run typecheck — no new errors
• Run npm run dev (full variant) — predictions panel loads with Polymarket markets
• Run npm run dev:finance — predictions panel shows Kalshi + economy Polymarket markets
• Verify source badge ("Polymarket" / "Kalshi") renders on each prediction item
• Verify tooltip mentions both sources
• Test with Kalshi API down — should degrade gracefully to Polymarket-only

Closes #1285

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[koala73]

Thanks for adding Kalshi as a second prediction source, @Rau1CS! Great work on the parallel fetch pattern and graceful degradation. A few items to address:

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BLOCKING

1. list-prediction-markets.ts:190 — Kalshi fetch fires unconditionally, even when not needed
   kalshiFetch starts on every request, including tech-scoped ones where includeKalshi (line 278) will be false. This wastes a network call + Redis read for every tech panel load. Restructure so the category check happens before kicking off the fetch.

2. list-prediction-markets.ts:214 — Bootstrap source detection is fragile

   (m as unknown as { source?: string }).source === 'kalshi'

   Double cast through unknown is a code smell. Define a BootstrapMarket interface and use it for the bootstrap type instead.

3. PredictionPanel.ts:48 — Source comparison uses raw string, not the enum value

   const sourceLabel = p.source === 'kalshi' ? 'Kalshi' : 'Polymarket';

   The proto sends MarketSource enum values (MARKET_SOURCE_KALSHI), but the panel compares against 'kalshi'. This will likely always show "Polymarket". Verify which format the client actually receives.

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SUGGESTION

4. seed-prediction-markets.mjs:108 — Kalshi volume filtering threshold is low.
   volume <= 1000 is very permissive compared to Polymarket's minVolume: 5000 in the Gamma API params. Consider raising for signal quality parity.

5. list-prediction-markets.ts:162-170 vs seed-prediction-markets.mjs:108-118 — Different market selection logic.
   The seed script picks the highest-volume market per event (via reduce), but the RPC handler picks the first active binary market (break after first match). These should use the same selection logic.

6. seed-prediction-markets.mjs:117 — Falsy zero-price bug

   const yesPrice = +(parseFloat(topMarket.last_price_dollars) * 100).toFixed(1) || 50;

   If last_price_dollars is "0", this evaluates to 0 (falsy), falling back to 50. A zero-price market would incorrectly show 50%. Use ?? 50 instead of || 50.

7. No CSS for .prediction-source badge. The panel adds <span class="prediction-source"> but no styles are included in the diff. Will render as unstyled inline text.

8. FINANCE_TAGS duplicated across seed-prediction-markets.mjs, list-prediction-markets.ts (inline check), and src/services/prediction/index.ts. Consider a shared constant.

9. Kalshi API URL uses api.elections.kalshi.com, which is the elections-specific subdomain. Verify this returns non-election markets too, or use the general trading-api.kalshi.com endpoint.

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NITPICK

10. open_interest is added to the proto but always 0 for Polymarket and never displayed. Consider deferring this proto field if it's not used yet.

11. Generated files (service_client.ts, service_server.ts) appear committed manually. Confirm these match buf generate output.

[Rau1CS]

Thanks for the thorough review! All items addressed in e767132 — here's the rundown:

BLOCKING (all fixed)

1. Kalshi fetch gated behind includeKalshi check before kickoff — tech-scoped requests no longer fire the call
2. Bootstrap typing replaced with explicit BootstrapMarket / BootstrapData interfaces, double cast removed
3. Panel source comparison verified correct — protoToMarket normalizes enum to 'kalshi'/'polymarket' before it reaches the panel

SUGGESTIONS (all fixed)
4. Kalshi volume threshold raised to 5000
5. RPC handler now uses same highest-volume reduce logic as seed script (single-pass loop)
6. Zero-price bug fixed with Number.isFinite guard instead of ||/?? — "0" now correctly yields 0, not 50
7. Added .prediction-source CSS with per-source color variants (blue for Kalshi, purple for Polymarket)

Items 8-11 (shared constants, Kalshi API subdomain, open_interest proto field, generated files) not addressed in this pass — happy to follow up if you'd like.

[koala73]

Sorry for the delay on this review, @Rau1CS. Nice work adding Kalshi as a second source. The parallel fetch pattern and graceful degradation are well done. A few issues to address:

P1: Live Kalshi path missing curation filters (seed/RPC divergence)

The seed script applies isExcluded() and a volume <= 5000 threshold, but fetchKalshiMarkets() in list-prediction-markets.ts applies neither. Users hitting the live RPC fallback (cache miss or stale bootstrap) will see unfiltered, low-volume, and potentially sports/entertainment markets that the seed path would have excluded.

Files: server/worldmonitor/prediction/v1/list-prediction-markets.ts (around line 184), scripts/seed-prediction-markets.mjs (line 113)

P2: FINANCE_TAGS includes markets but seed never fetches it

allTags in the seed script is [...GEOPOLITICAL_TAGS, ...TECH_TAGS]. The markets tag from FINANCE_TAGS is never fetched from the Gamma API, so finance bootstrap is missing those Polymarket events entirely.

File: scripts/seed-prediction-markets.mjs (line 148)

P2: Kalshi title mapping differs between seed and RPC

Seed uses topMarket.title || event.title (line 134), but the RPC handler uses market.yes_sub_title || market.title (line 150). The same contract can render with a different label depending on which code path served it, which also affects query filtering behavior.

Files: scripts/seed-prediction-markets.mjs (line 134), server/worldmonitor/prediction/v1/list-prediction-markets.ts (line 150)

P2: Finance variant falls back to geopolitical on cache miss

Both src/services/prediction/index.ts (line 64) and list-prediction-markets.ts (line 220) fall back to bootstrap.geopolitical when bootstrap.finance is absent. Older cached payloads without a finance key will silently serve geopolitical data to finance-variant users instead of falling through to the RPC path.

Files: src/services/prediction/index.ts (line 64), server/worldmonitor/prediction/v1/list-prediction-markets.ts (line 220)

[Rau1CS]

Sorry for the delay — all P1/P2 items from the latest review are addressed in the last two commits. Ready for another look when you get a chance!

[koala73]

Thanks a lot for the solid work on this, @Rau1CS! The parallel fetch pattern, graceful degradation, and seed/RPC parity fixes from the last two rounds are all looking great. This is almost ready to merge.

Three suggestions before we close it out:

1. Kalshi API subdomain: Both the seed script and RPC handler use api.elections.kalshi.com, which is the elections-specific endpoint. Verify it returns non-election markets (economy, crypto, etc.) too, or switch to trading-api.kalshi.com. If elections-only data is coming through, the finance variant will have gaps.

2. FINANCE_TAGS is defined in 3 places: seed-prediction-markets.mjs, list-prediction-markets.ts, and src/services/prediction/index.ts. If any one drifts, seed/RPC/frontend will disagree on what counts as "finance." Consider extracting to a shared constant (can be a follow-up PR if you prefer).

3. open_interest proto field: Currently always 0 for Polymarket and not displayed anywhere in the UI. If it's not wired up yet, consider deferring the field to keep the proto lean (also fine as a follow-up).

Items 1 is the most important. 2 and 3 can be follow-up PRs if you'd rather not block on them. Let me know!

[Rau1CS]

Thanks for the review!

1. Kalshi API subdomain — Fixed in ce0e16a. Both seed and RPC now use trading-api.kalshi.com instead of the elections-specific subdomain.
2. FINANCE_TAGS shared constant — Happy to extract in a follow-up PR.
3. open_interest proto field — Agreed it's dead weight for now, will clean up in a follow-up.

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Project	Deployment	Actions	Updated (UTC)
worldmonitor	Ready	Preview, Comment	Mar 12, 2026 7:53pm