Methodology
How TRUELINE thinks.
Baseball is a sequence of plate appearances, not a scoreline. The engine walks every batter against the actual pitcher on the mound, 1,600 times on the board and 8,000 times in the lab, then reads the distribution. We never draw the final from a single regression.
1. Batter vs pitcher
Each PA is a multinomial: strikeout, walk, HBP, single, double, triple, home run, or out. Probabilities are log5 combinations of batter rates and pitcher K/9, BB/9, HR/9, then shifted for platoon (same-hand Ks up, extra-base hits down). Known arsenals — Rodón slider, Gausman splitter, Sánchez sinker/change — weight the matchup toward the pitch types that batter actually sees.
2. Decay
Starters are pulled on pitch count, times-through, and blowout rules. After the hook, the bullpen inherits with a fatigue score from recent run environment. A velocity/spin flag (ERA spike vs season) taxes K rate and inflates HR and walk rates on the way out.
3. Weather physics
Stadium feed temp, wind, and condition go into density altitude. Lower air density, hotter air, and wind out to center field raise the HR multiplier; a 15 mph blow-out at Wrigley is not a 15 mph blow-out at Oracle. Humidor parks (Coors, Chase, Globe Life) cut the coefficient of restitution. Domes ignore wind.
4. The umpire
Home-plate assignment comes off the MLB officials feed. Wide zones add Ks and kill walks (Under lean). Tight zones do the opposite (Over lean). The shadow zone is the highest-leverage inch in the sport and books are slow to fully price it.
5. True vs the window
Fair odds are the no-vig inversion of simulation frequencies. DraftKings numbers are live from the ESPN close when posted. Other books are a realistic shade of that close. Edge is true probability minus market implied. We bet the difference, not the narrative.
6. The 80% desk rule
We will not tell you to bet unless the Monte Carlo says the ticket hits in at least 80% of worlds. Posted moneyline, posted total, and run line are checked first. If those sit under 80%, we walk the score histogram to the tightest Under within 3.5 runs of the posted number that still clears the floor, and that is the bet. Anything else is a sit. Official tickets lock one hour before first pitch, or the moment the game starts — whichever comes first — then freeze. They are graded against the final and cannot be edited. Every ticket is saved with the sim snapshot at lock (mean total, true win, weather, umpire, starters) and kept on the ledger.
7. 65% desk book
If a side is at least 65% but under the 80% floor, it is written into a real book: pick, game, posted %, fair and posted price, close (or “no posted book (alternate)”), grade, units. Stake is 1u default, 0.5u when the fair price is −200 or shorter. The book is append-only — oldest stays, misses stay, running units walk the list. It is never stamped as an official ticket and never enters the 80% win–loss record.
8. Alerts
Three pings only: an official 80% ticket locked, that ticket graded, or a slate with zero 80% tickets (“desk sat today”). Never a 65% lean. Toasts and the tray always fire; a system banner fires if the browser allows it. Alerts sit on the desk pass.
9. Stake
Official tickets and the 65% book. 1u default. 0.5u when the fair price is −200 or shorter. No bankroll dashboard — the desk sits, it does not size a season for you.
10. The public board and the desk pass
Free: Board headlines, official 80% tickets, sit count, and the 65% win–loss plus units summary. The desk pass is $39/month or $299/year and unlocks the full 65% list, Markets True row, game lab, snapshots, and alerts. Checkout is on-site; the pass unlocks only from server subscription status. Same four pages. Operated by Jay. The ledger is append-only and is not edited after lock.
Live inputs: MLB Stats API (schedule, officials, weather, standings, pitcher season lines) and ESPN scoreboard (DraftKings closes). Research only. Not a sportsbook. 21+. Operated by Jay.