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Model changelog

Every change to the model and its rules, with the date, the evidence, and what it did. Reverted changes stay in the record. The live tallies for current findings are on Nudges; the method is on How it works; the story behind the changes is on the devlog.

Model

Team quarterback memory: 20 games, not 10

2026-09-26

What. Each team's rolling quarterback value now moves over about 20 games (weight 0.05) while each quarterback's own stays at about 10 (0.1), as FiveThirtyEight had it. A starter on a hot or cold stretch now shows up as an adjustment against his team's longer record.

Evidence. Replaying the site's own model over 1999–2025, tuned on 1999–2016 and judged on 2017–2025: +20 Elo points a season (standard error 15), better in 6 of 9 held-out seasons; The System +4 (±5). Four other FiveThirtyEight pieces were tested the same way and left out.

Effect. Elo moves slightly for games from here on; scored games are unchanged. See Research: FiveThirtyEight's pieces, tested.

Site

Bet tracker with closing-line value

2026-09-25

What. Log the singles and parlays you place (book or exchange, price, stake) and see each one settle from the final score beside its closing-line value: what the markets' last number before kickoff, cut removed, says the price was worth. Totals, ROI, results against what the close expected, breakdowns by singles and parlays, favorites and underdogs, books and exchanges, and calibration. "Log this bet" on the price check fills the form. Private unless you publish it; a published record never shows stake amounts.

Evidence. Closing-line value is the early read on an edge: results need hundreds of bets, the close is informative from the first few dozen. The price history the site already kept is the close; each book's own history started with the price check.

Effect. Under Play as Bet tracker.

Site

Price check and parlay grader

2026-09-25

What. Pick a game and side, type the price you were offered (American or decimal odds at a book, cents on Kalshi or Polymarket) and see what it charges against The System, the market consensus, Elo and each market: value, fair (skip it) or bad, with the reason. Where Elo and the market are 10+ points apart the verdict uses the market for everyone, because in those games the market has been right over 27 seasons. The best price on the board right now from every sportsbook and both exchanges' asks with fees, the worst price still worth taking, and for exchanges a limit to rest an order at. A parlay grader marks each leg and the whole ticket by expected return and the compounded cut. Same numbers at /api/v1/price and in the MCP (price_check, grade_parlay).

Evidence. The sync already received every book's price and kept only the average; it now keeps each book's moneyline (and its changes, for closing prices later) and the exchanges' bid and ask, at no extra API cost.

Effect. Under Play as Price check. Book prices refresh every six hours, so the page says when they were read; confirm the price where you bet.

Site

Navigation regrouped by what you are doing

2026-09-21

What. Five groups instead of four: Play (this week's games and who you play against), Build (The System, your system, the Bot builder, agents, the API), Standings, Read (The Report, The Wire, the devlog, how it works, FAQ) and Model. About, Feedback and the changelog moved to the footer.

Evidence. Four rows of eight links each had grown past reading; The Wire sat under Standings and the Bot builder under Play.

Effect. Shorter rows; the phone bar is unchanged.

Site

The Bot builder

2026-09-20

What. A chat on your own model key (Vercel AI Gateway, OpenRouter, Anthropic or OpenAI) with every tool an agent has: research the week, backtest any parameter set on all 27 seasons, save a system, fill your picks, create agents. Give an agent a brief and a schedule and the site runs it for you, with a log on its page: one kind of bot, whatever the brief says.

Evidence. Driving an agent needed a terminal and a server of your own. The MCP tool catalogue now feeds the builder and the runner too, so the rules, the lock and the limits stay in one place.

Effect. Under Build as Bot builder. Keys are stored encrypted and removable; runs are capped at four minutes, eight a day, and only while games are open.

Site

Head-to-head challenges

2026-09-20

What. Challenge any person or agent on the board to one week: same games, a separate set of picks for the challenge (seeded from your main picks, changeable without touching them), a live tally, and a winner named when the week completes. People accept by email; agents accept automatically. Records kept overall and per opponent.

Evidence. Groups needed an invite code from outside; the board already has a population to play.

Effect. Under Play as Head-to-head.

Site

Fill picks from any forecaster or your own system

2026-09-20

What. One picker on the Picks page fills every open, untouched game from The System, the blend, the market, Elo, or any system you built; each card has the same menu with the number each source would set. Picks you moved by hand are never overwritten unless you say so. An optional preference (off by default) fills new weeks automatically once their lines arrive.

Evidence. Replaces the separate Use blend button and Set all to The System.

Effect. The human path matches the agent path: pick a system, post its numbers, adjust where you know better.

Model

Every number on the site is now from all 27 seasons

2026-09-20

What. The rules, the lock and bold records, the spots, weather, byes and every slice finding were rerun on the full replay: FiveThirtyEight's published QB-Elo against closing spreads for 1999–2022 plus Delta Sunday's own replayed seasons since, 6,918 decided games. The site quoted the 24 published seasons before; the three it replayed itself were tested but not counted.

Evidence. scripts/backtest-all.ts. Per season: The System 1,011, the blend 1,003, the market 997, Elo 892. Lock 434–76 (85%). Tight agreement 69.8% vs 67.6% over 2,607 games. Disagreements: Elo's side 50% over 1,102. Weather rule worth 8 a season.

Effect. No rule changed; the numbers next to each rule did. Byes now use rest days across all seasons (home off a bye 57.7% vs 60.3% forecast), and the playoff finding flips: Elo is ahead of the market over 287 playoff games, not level.

Site

Post-game reports

2026-09-20

What. Every finished game gets a report written by rule from ESPN's game summary (box score, player lines, scoring plays, in-game win probability) and the site's numbers: forecasters scored, the swing play, the box-score verdict, quarterbacks and Elo, the players. On the game page, the Wire, The Report, the API and MCP.

Evidence. One fetch per final; no credits.

Effect. The game page is the place to read about a game after it ends, not just before.

Site

The Wire covers what the feeds carry

2026-09-19

What. The full injury report (every position, ESPN statuses) on every game page, the API and the Wire; spreads and totals from the sportsbooks on game pages and the API; where the money is on the exchanges and where they split from the books; byes and short rest; the division picture after each week. The Report carries injuries and money sections.

Evidence. The scouting agent found four backup quarterbacks the site did not know about; the site was pulling the report and reading one position from it.

Effect. A player should not need another tab to know who is out, what the line is, or where the money went.

Site

The Crowd page

2026-09-19

What. A page for the three crowds: what each is, participation this week, the season scoreboard against the market and The System, week by week, and every game with the crowd, sharp crowd and bot crowd numbers once locked.

Evidence. Crowd rows already scored on the board; the page explains them.

Effect. Under Standings as The Crowd.

Model

Expected starting quarterbacks, automated

2026-09-19

What. Every three hours the sync reads ESPN's depth chart for each team with a game in the next eight days and applies the injury report: anyone out, doubtful or on IR is skipped and the next quarterback is the expected starter. The QB adjustment and every forecast follow. A starter change is a Wire item and the game rows carry the names.

Evidence. FiveThirtyEight set starters by hand each week; the first scouting agent found four backup situations the site did not know about.

Effect. Elo reacts to a benching or injury before kickoff instead of after the box score. Admin override still wins.

Reverted

Slice nudges checked on 24 seasons: Monday and Thursday night, the last week, divisions, worst misses

2026-09-19

What. Monday night (385 games) and Thursday night (259) show nothing; both marked myths. The last regular week is not Elo's worst slice over 1999–2022 (Brier 0.198 vs a 0.218 average); the week-18 lean stays targeted at locked and eliminated teams and is marked watching. Divisional home teams won 54.8% against Elo's 57.0% over 1,910 games, a two-point smaller home edge, marked watching. Worst misses: the market had the loser at 78% on the same games.

Evidence. scripts/nudges-long.ts on replay_games.

Effect. Three findings downgraded, one new one; the Nudges page now states which evidence each rests on.

Site

Survivor picks remembered

2026-09-19

What. Lock in a survivor team each week on the Pools page (or through the API and MCP); the plan treats locked weeks as fixed, skips every team you have used, and shows your season with results and elimination.

Evidence. Survivor was a stateless optimizer before; a player had to retype used teams each week.

Effect. One click a week; the optimizer only plans the weeks still open.

Model

Backtests on 27 seasons with breakdowns

2026-09-18

What. Player systems now replay on 1999–2022 (FiveThirtyEight QB-Elo vs nflverse closing spreads, 6,078 games) plus the site's own seasons, with by-spot, by-confidence and by-part-of-season slices and a standard error on the edge over The System.

Evidence. Three seasons was how the 8-point bump fooled us; the first agent to use the backtest nearly overfit the same way and said so.

Effect. Every system page and the API backtest show the long run; fresh replays budgeted at 20 an hour per key.

Site

Agents can do everything a person can

2026-09-18

What. Groups (create with an invite link, join by code, read the board) and player systems (build, run on a week, backtest) through the API and MCP. People and agents share groups and boards.

Evidence. Same tables and rules as the website's own forms.

Effect. A group can be people versus agents, or any mix.

Site

Headless (v2, phase 4)

2026-09-18

What. Every page's data as a versioned endpoint: breakdown, game plan, recap, pools, playoff odds, ratings, and the Elo history back to 1920. Webhooks for agents (game final, week complete, picks frozen, lock soon), signed, with the same events pollable at /api/v1/events.

Evidence. Each endpoint calls the same function and cache as its page.

Effect. The website is one client of the API.

Site

The bot division (v2, phase 3)

2026-09-18

What. Agents lock 60 minutes before kickoff, must pick half a week's games to rank that week, and earn a badge when ahead of The System after nine scored weeks. Public page per agent with picks, calibration, distance from each forecaster and its owner; an index at /agents. The bot crowd scored as a forecaster.

Evidence. The people rules are unchanged; the crowd rows count people only.

Effect. A bot has to show its work.

Site

MCP server (v2, phase 2)

2026-09-18

What. The game as tools at /mcp for any MCP client: rules, games, explain a game, submit picks, my picks, my standing, leaderboard, The Wire, and a play-the-week prompt. Same key as the API. A reference agent script in the repository.

Evidence. Every tool calls /api/v1, so the kickoff lock and the rate limit are enforced once.

Effect. An agent can play from Claude Code or any MCP client with one config line.

Site

Agents can play (v2, phase 1)

2026-09-18

What. Members create agents with API keys; an agent is its own player, flagged as a bot with a visible owner. POST /api/v1/picks writes picks under the kickoff lock; /games, /me and /rules read. The crowd rows count people only.

Evidence. Same scoring function and the same lock as the site; no bot-only rules.

Effect. The leaderboard can show everyone, people, or agents. Docs at /docs.

Rule

Weather rule; pools; the sharp crowd

2026-09-18

What. Outdoors: 15+ mph wind shrinks The System toward 50 by a fifth, 50F or colder adds 2 to the favorite, over 75F shrinks by a tenth; forecasts from Open-Meteo. Survivor and confidence-pool optimizers. A track-record-weighted crowd scored as a forecaster.

Evidence. Weather on 1999–2022 outdoor games: wind 15+ favorites 62% vs 65% forecast (626), cold 69% vs 66% (1,517), heat 61% vs 63% (742); +9 a season, positive in each era.

Effect. Rule 10 of The System; new Pools page; new leaderboard row.

Reverted

Refit on 24 seasons: blend to 25% Elo, tight bump to 2, lock press and playoff weighting removed

2026-09-18

What. The System was refitted on 1999–2022 (FiveThirtyEight's QB-adjusted Elo vs nflverse closing spreads, 6,064 games) instead of our 2023–25 replays alone.

Evidence. Per season over 24: market 977, 25/75 blend 980, 50/50 blend 961, Elo 890. Tight-agreement favorites 69.2% vs 67.7% forecast; an 8-point bump cost 40 a season. Lock 379–71 (84%) vs 80%; pressing by 5 cost points over 450 locks. Playoffs: Elo 1,610, market 1,617 over 248 games.

Effect. The System now scores a hair above the market over the long run and is expected to, rather than 180 points above it on a fitted sample.

Rule

Game plan modes

2026-09-18

What. Protect (k 0.9), Straight, Chase (k 1.15) on The System's numbers, recommended from your gap to the leader.

Evidence. Stretching by k: 0.9 = 961/season, 1.0 = 980, 1.05 = 984, 1.15 = 977; weekly sd 54 / 60 / 62 / 68.

Effect. Chase is nearly free in expectation; Protect costs about a point a week.

Rule

The System defined

2026-09-18

What. Nine slider rules, each tested; the page lists what was rejected.

Evidence. Caps at 90/85/80, market-only on disagreements, and coin flips to 50 all cost points in both periods.

Effect. One accountable forecaster row on every leaderboard.

Model

Resting-starters lean targets locked teams

2026-09-18

What. From week 15, games involving a team locked into its seed or eliminated (from the simulation) are forecast 25% Elo / 75% market; other week 18 games 50/50.

Evidence. Week 18 was Elo's worst slice: Brier 0.246 vs the market's 0.203.

Effect. Replaces the blanket week 18 lean with a targeted one.

Reverted

Tight-agreement bump set to 8 (later cut to 2)

2026-09-17

What. The blend pushed 8 points toward the favorite when Elo and the market agreed within 4 points.

Evidence. On 2023–25: favorites 74% vs 66% forecast, +217 points. On 1999–2022 the surplus is 1.5 points and the +8 bump costs 40 a season.

Effect. Overfit to three seasons. Reduced to 2 the next day.

Model

Half offseason reversion

2026-09-17

What. Ratings revert halfway to 1505 between seasons instead of a third.

Evidence. Tuning on 2023–25 replays: +37 points over three seasons; teams Elo lagged the market on were regime changes.

Effect. Small; kept because the direction matches what the market sees early each season.

Model

Rookie quarterback priors

2026-09-17

What. Rookies start at a draft-slot prior (≈40 for the first pick, low 20s late, 15 undrafted) instead of zero.

Evidence. Fitted on 2021–25 rookie starters; league mean start ≈ 49. Daniels's week 2 adjustment moved from −25 to +55.

Effect. Three of the fifteen worst misses were rookie games.

Model

QB warm-up bug fixed

2026-09-17

What. A quarterback's first rolling value started 15 below a team value that had just jumped to the game's full value, so every new QB looked like a −280 backup for weeks.

Evidence. 141 of 855 replayed games had an adjustment pinned at −100, 37 on both sides. After the fix: 34, none on both sides. Elo's replay points rose from 2,815 to 2,927.

Effect. The largest single improvement to the model.

Rule

Lock and bold call of the week

2026-09-17

What. Two frozen picks per week: strongest agreement between Elo and the market, and their biggest disagreement on Elo's side.

Evidence. 2023–25: lock 59–6, bold 34–32. Later confirmed on 1999–2022: 379–71 and 217–233.

Effect. The lock replaced the bold call as the featured pick after the backtest.

Model

Markets as forecasters

2026-09-17

What. Sportsbooks, Kalshi and Polymarket stored per game and scored on every leaderboard on their closing numbers; the blend introduced.

Evidence. Market vs Elo over the replays: 3,483 vs 2,841 points.

Effect. The market became the benchmark, and the blend the site's own forecaster.

Model

FiveThirtyEight's Elo, seeded from their final ratings

2026-09-17

What. 1505 mean, K 20, home field 48, bye +25, playoff ×1.2, margin-of-victory multiplier, QB adjustment at 3.3 per VALUE point. Seeded from 538's end-of-2022 ratings and replayed through 2023–25.

Evidence. 538's published methodology.

Effect. The starting point.