Expose rating uncertainty in frontmatter

src/domain/matchmaking/Matchmaker.ts

@@ -1,10 +1,9 @@
 import type { TFile } from 'obsidian';
 
-import { DEFAULT_SIGMA } from '../rating/GlickoEngine';
 import type { ScoredPlayer } from './InfoGain';
 import { pickMaxInfoGainPair } from './InfoGain';
 
-export type RatingStats = { rating: number; sigma?: number };
+export type RatingStats = { rating: number; sigma: number };
 
 export function pickNextPairIndices(
   files: TFile[],
@@ -28,7 +27,7 @@ export function pickNextPairIndices(
 
   const players: ScoredPlayer[] = files.map((f, i) => {
     const s = getStats(f);
-    return { index: i, rating: s.rating, sigma: s.sigma ?? DEFAULT_SIGMA };
+    return { index: i, rating: s.rating, sigma: s.sigma };
   });
 
   const result = pickMaxInfoGainPair(players, rng, { lastPairIndices });

src/domain/report/TemplatePlaceholders.ts

@@ -184,7 +184,7 @@ export function computePlaceholders(
   if (cohort) {
     const allWithSigma = Object.entries(cohort.players)
       .filter(([, p]) => p.sigma != null)
-      .map(([id, p]) => ({ id, sigma: p.sigma! }));
+      .map(([id, p]) => ({ id, sigma: p.sigma }));
 
     const sessionWithSigma = allWithSigma.filter(({ id }) => uniquePlayerIds.has(id));
 
@@ -221,7 +221,7 @@ export function computePlaceholders(
     }
 
     // Leaderboard tables
-    const buildLeaderboard = (entries: { id: string; rating: number; sigma?: number }[]) => {
+    const buildLeaderboard = (entries: { id: string; rating: number; sigma: number }[]) => {
       if (entries.length === 0) return '';
       const rows: string[] = [];
       rows.push('| Rank | Note | Rating |');
@@ -229,7 +229,7 @@ export function computePlaceholders(
       for (let i = 0; i < entries.length; i++) {
         const e = entries[i];
         const name = idToName(e.id, data.idToPath);
-        const sigma = e.sigma != null ? ` (σ ${Math.round(e.sigma)})` : '';
+        const sigma = ` (σ ${Math.round(e.sigma)})`;
         rows.push(`| ${i + 1} | ${name} | ${Math.round(e.rating)}${sigma} |`);
       }
       return rows.join('\n');

src/settings/SettingsTab.ts

@@ -188,7 +188,7 @@ export default class GlickoSettingsTab extends PluginSettingTab {
     new Setting(containerEl)
       .setName('Stability threshold')
       .setDesc(
-        `Sigma value at which the progress bar reaches 100%. Lower values require more matches. Default: ${DEFAULT_SETTINGS.stabilityThreshold}.`,
+        `Uncertainty value at which the progress bar reaches 100%. Lower values require more matches. Default: ${DEFAULT_SETTINGS.stabilityThreshold}.`,
       )
       .addSlider((sl) => {
         const current =
@@ -530,7 +530,7 @@ export default class GlickoSettingsTab extends PluginSettingTab {
       newProp?: string;
     }> = [];
 
-    const keys: PropKey[] = ['rating', 'rank', 'matches', 'wins'];
+    const keys: PropKey[] = ['rating', 'uncertainty', 'rank', 'matches', 'wins'];
     for (const key of keys) {
       const oldCfg = oldEffective[key];
       const newCfg = newEffective[key];
@@ -566,6 +566,8 @@ export default class GlickoSettingsTab extends PluginSettingTab {
         for (const [id, rank] of rankMap) map.set(id, rank);
       } else if (key === 'rating') {
         for (const [id, p] of Object.entries(cohort.players)) map.set(id, Math.round(p.rating));
+      } else if (key === 'uncertainty') {
+        for (const [id, p] of Object.entries(cohort.players)) map.set(id, Math.round(p.sigma));
       } else if (key === 'matches') {
         for (const [id, p] of Object.entries(cohort.players)) map.set(id, p.matches);
       } else if (key === 'wins') {

src/settings/settings.ts

@@ -8,6 +8,7 @@ export interface FrontmatterPropertyConfig {
 
 export interface FrontmatterPropertiesSettings {
   rating: FrontmatterPropertyConfig;
+  uncertainty: FrontmatterPropertyConfig;
   rank: FrontmatterPropertyConfig;
   matches: FrontmatterPropertyConfig;
   wins: FrontmatterPropertyConfig;
@@ -42,6 +43,7 @@ export const DEFAULT_SETTINGS: GlickoSettings = {
   sessionLayout: 'new-tab',
   frontmatterProperties: {
     rating: { property: 'glickoRating', enabled: false },
+    uncertainty: { property: 'glickoUncertainty', enabled: false },
     rank: { property: 'glickoRank', enabled: false },
     matches: { property: 'glickoMatches', enabled: false },
     wins: { property: 'glickoWins', enabled: false },
@@ -68,6 +70,7 @@ export function effectiveFrontmatterProperties(
 ): FrontmatterPropertiesSettings {
   return {
     rating: overrides?.rating ?? base.rating,
+    uncertainty: overrides?.uncertainty ?? base.uncertainty,
     rank: overrides?.rank ?? base.rank,
     matches: overrides?.matches ?? base.matches,
     wins: overrides?.wins ?? base.wins,

src/storage/PluginDataStore.ts

@@ -60,6 +60,12 @@ function mergeSettings(raw?: Partial<GlickoSettings>): GlickoSettings {
 
   const out: GlickoSettings = { ...base, ...raw };
 
+  // Deep-merge frontmatterProperties so new keys (e.g. uncertainty) get defaults
+  out.frontmatterProperties = {
+    ...DEFAULT_SETTINGS.frontmatterProperties,
+    ...raw.frontmatterProperties,
+  };
+
   if (noIdPropertyName) {
     out.idPropertyName = 'eloId';
   }
@@ -183,13 +189,20 @@ export class PluginDataStore {
   resetPlayer(cohortKey: string, playerId: string): boolean {
     const cohort = this.store.cohorts[cohortKey];
     if (!cohort?.players[playerId]) return false;
-    cohort.players[playerId] = { rating: 1500, matches: 0, wins: 0 };
+    cohort.players[playerId] = { rating: 1500, matches: 0, wins: 0, sigma: DEFAULT_SIGMA };
     return true;
   }
 
   ensurePlayer(cohortKey: string, id: string) {
     const cohort = (this.store.cohorts[cohortKey] ??= { players: {} } as CohortData);
-    const player = (cohort.players[id] ??= { rating: 1500, matches: 0, wins: 0 });
+    const player = (cohort.players[id] ??= {
+      rating: 1500,
+      matches: 0,
+      wins: 0,
+      sigma: DEFAULT_SIGMA,
+    });
+    // Backfill legacy players that predate sigma tracking
+    if (player.sigma === undefined) (player as { sigma: number }).sigma = DEFAULT_SIGMA;
     return { cohort, player };
   }
 
@@ -201,8 +214,8 @@ export class PluginDataStore {
   ): { winnerId?: string; undo: UndoFrame } {
     const cohort = (this.store.cohorts[cohortKey] ??= { players: {} });
 
-    const a = (cohort.players[aId] ??= { rating: 1500, matches: 0, wins: 0 });
-    const b = (cohort.players[bId] ??= { rating: 1500, matches: 0, wins: 0 });
+    const a = (cohort.players[aId] ??= { rating: 1500, matches: 0, wins: 0, sigma: DEFAULT_SIGMA });
+    const b = (cohort.players[bId] ??= { rating: 1500, matches: 0, wins: 0, sigma: DEFAULT_SIGMA });
 
     const now = Date.now();
 
@@ -220,8 +233,8 @@ export class PluginDataStore {
     // accommodate preference drift. This also prevents the stability progress
     // bar from regressing after long gaps between sessions.
     const cap = this.settings.stabilityThreshold ?? 150;
-    const preSigmaA = inflateSigma(a.sigma ?? DEFAULT_SIGMA, now - (a.lastMatchAt ?? now), cap);
-    const preSigmaB = inflateSigma(b.sigma ?? DEFAULT_SIGMA, now - (b.lastMatchAt ?? now), cap);
+    const preSigmaA = inflateSigma(a.sigma, now - (a.lastMatchAt ?? now), cap);
+    const preSigmaB = inflateSigma(b.sigma, now - (b.lastMatchAt ?? now), cap);
 
     const sA = result === 'A' ? 1 : result === 'D' ? 0.5 : 0;
     const resA = glickoUpdate(a.rating, b.rating, preSigmaA, preSigmaB, sA);
@@ -327,7 +340,7 @@ function snapshot(
   rating: number,
   matches: number,
   wins: number,
-  sigma?: number,
+  sigma: number,
   lastMatchAt?: number,
 ): PlayerSnapshot {
   return { id, rating, matches, wins, sigma, lastMatchAt };

src/types.ts

@@ -6,7 +6,7 @@ export interface Player {
   rating: number;
   matches: number;
   wins: number;
-  sigma?: number;
+  sigma: number;
   lastMatchAt?: number;
 }
 
@@ -71,7 +71,7 @@ export interface PlayerSnapshot {
   rating: number;
   matches: number;
   wins: number;
-  sigma?: number;
+  sigma: number;
   lastMatchAt?: number;
 }
 

src/ui/ArenaSession.ts

@@ -321,7 +321,7 @@ export default class ArenaSession {
 
     let playedSum = 0;
     for (const p of players) {
-      playedSum += p.sigma ?? DEFAULT_SIGMA;
+      playedSum += p.sigma;
     }
 
     // Files not yet in the player table carry full uncertainty
@@ -739,7 +739,7 @@ export default class ArenaSession {
 
   // ---- Matchmaking helpers ----
 
-  private getStatsForFile(file: TFile): { rating: number; sigma?: number } {
+  private getStatsForFile(file: TFile): { rating: number; sigma: number } {
     const id = this.idByPath.get(file.path);
     const cohort = this.plugin.dataStore.store.cohorts[this.cohortKey];
 
@@ -748,7 +748,7 @@ export default class ArenaSession {
       if (p) return { rating: p.rating, sigma: p.sigma };
     }
 
-    return { rating: 1500 };
+    return { rating: 1500, sigma: DEFAULT_SIGMA };
   }
 
   private pickNextPair() {

src/ui/CohortOptionsModal.ts

@@ -106,6 +106,7 @@ export class CohortOptionsModal extends BasePromiseModal<CohortOptionsResult | u
 
     this.working = {
       rating: mk('rating'),
+      uncertainty: mk('uncertainty'),
       rank: mk('rank'),
       matches: mk('matches'),
       wins: mk('wins'),

src/ui/FrontmatterPropertyRow.ts

@@ -1,8 +1,14 @@
 import type { TextComponent, ToggleComponent } from 'obsidian';
 import { Setting } from 'obsidian';
 
-export type FmPropKey = 'rating' | 'rank' | 'matches' | 'wins';
-export const FM_PROP_KEYS: readonly FmPropKey[] = ['rating', 'rank', 'matches', 'wins'] as const;
+export type FmPropKey = 'rating' | 'uncertainty' | 'rank' | 'matches' | 'wins';
+export const FM_PROP_KEYS: readonly FmPropKey[] = [
+  'rating',
+  'uncertainty',
+  'rank',
+  'matches',
+  'wins',
+] as const;
 
 type Meta = { label: string; desc: string };
 
@@ -11,6 +17,10 @@ const META: Record<FmPropKey, Meta> = {
     label: 'Rating',
     desc: 'Write the current Glicko rating to this property.',
   },
+  uncertainty: {
+    label: 'Uncertainty',
+    desc: 'Write how uncertain the rating is. Starts high and decreases as more comparisons are made.',
+  },
   rank: {
     label: 'Rank',
     desc: 'Write the cohort rank (1 = highest) to this property.',

src/utils/FrontmatterStats.ts

@@ -7,13 +7,20 @@ import { getNoteId } from './NoteIds';
 
 type PlayerStats = {
   rating: number;
+  uncertainty: number;
   matches: number;
   wins: number;
   rank: number;
 };
 
 function anyEnabled(fm: FrontmatterPropertiesSettings): boolean {
-  return !!fm.rating.enabled || !!fm.rank.enabled || !!fm.matches.enabled || !!fm.wins.enabled;
+  return (
+    !!fm.rating.enabled ||
+    !!fm.uncertainty.enabled ||
+    !!fm.rank.enabled ||
+    !!fm.matches.enabled ||
+    !!fm.wins.enabled
+  );
 }
 
 // Standard competition ranking ("1224" style)
@@ -71,6 +78,9 @@ function buildProps(fm: FrontmatterPropertiesSettings, stats: PlayerStats): Reco
   if (fm.rating.enabled && fm.rating.property) {
     out[fm.rating.property] = Math.round(stats.rating);
   }
+  if (fm.uncertainty.enabled && fm.uncertainty.property) {
+    out[fm.uncertainty.property] = Math.round(stats.uncertainty);
+  }
   if (fm.rank.enabled && fm.rank.property) {
     out[fm.rank.property] = stats.rank;
   }
@@ -304,6 +314,7 @@ export async function writeFrontmatterStatsForPlayer(
   const rankMap = precomputedRankMap;
   const props = buildProps(fm, {
     rating: p.rating,
+    uncertainty: p.sigma,
     matches: p.matches,
     wins: p.wins,
     rank: rankMap.get(playerId) ?? rankMap.size,