Summary

• Metaculus: public forecasting platform, no auth, GET-based. Added to pm-api-latency + pm-rate-limits (price + list classes, ramp 5/10/20 per 10s, conservative)
• Betfair: UK FCA-regulated exchange, auth required, POST-based Exchange API. Added to pm-api-latency + pm-rate-limits (book + price + list, ramp 10/25/50, stop on 429)
• Harness changes: added Method/BodyFn to Class struct + RequestMutator to Venue struct so probeOnce handles POST venues — fully backwards-compatible
• New betfair_auth.go: session management (login → keepalive loop, or pre-supplied token), triggered by BETFAIR_APP_KEY + BETFAIR_USERNAME/PASSWORD or BETFAIR_SESSION_TOKEN
• venues() now takes Config; Betfair only wired when credentials are present, Metaculus always wired
• YAMLs: rank_matrix_query, dimensions, metric_panels, providers, per_chain_explainer all updated
• pm-venue-context.ts: metaculus + betfair added to PM_VENUE_META

Notes

• Betfair data only appears when Railway env has Betfair creds set. Metaculus starts immediately (public API)
• Betfair uses binary market (2 runners) with >48h horizon as the pin
• Metaculus uses open binary question with >24h close_time as the pin