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, FanDuel, and Circa print live from The Odds API (ESPN as backup). We never invent a second book by shading DraftKings. Edge is true probability minus market implied. Green cells on Markets are +EV. 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 the posted Under is not the number on the card (8.0 or 8.5 when that is the total), we sit. We do not lock an 11.5 alternate as an official ticket. 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 or posted 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 or posted 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
Logged out: official 80% tickets, sit count, W–L summary, and the CSV. Signup is free. 65% rows and Beta stay hidden until the desk is granted. The desk pass is $39/month or $299/year and unlocks the full 65% list, Markets True row, game lab, snapshots, and alerts. Desk only after Stripe confirms plan=desk for that email, or when Jay grants desk to the email. Same four pages. Operated by Jay. The ledger is append-only and is not edited after lock.
11. Dual engine
Alpha is the public 80% ledger. It sits when the market is priced. That record is the product. Beta is a subscriber feed of 53–57% true plays with a 1.5-pt edge vs the posted or template price — NRFI, F5, and tight sides. Hitting ~55% at volume is the sports-model living. Beta never writes the Alpha ledger.
12. Invisible context
Travel-fatigue scores road clubs on rest, extras, time-zone shift, and early getaways. Umpire cards now shift in high leverage (RISP, two outs, late innings) and carry a catcher-framing proxy. Weather uses density altitude plus humidity and barometric pressure so Coors air is not Tropicana air even at the same wind reading. Carry is reported in inches.
13. Derivative markets
NRFI, first-five moneyline and total, and first-15-pitch strikeouts are priced off the same plate-appearance sim. Books often shade those off a static template. That is where Beta lives.
14. Bankroll Shield and the lab
When an Alpha or Beta ticket prints, the Shield writes a small recreational MLB parlay to sit next to it so the betting signature does not look like a model. No NFL. The lab lets you shift wind and humidity and re-run 800 worlds. Locked 80% tickets do not move.
Live inputs: MLB Stats API (schedule, officials, weather, standings, pitcher season lines), The Odds API (DraftKings / FanDuel / Circa), ESPN scoreboard as backup. Research only. Not a sportsbook. 21+. Operated by Jay.