burkben · burkben · Jun 20, 2026 · Jun 20, 2026
diff --git a/apps/mobile/src/app/history/[id].tsx b/apps/mobile/src/app/history/[id].tsx
@@ -5,7 +5,7 @@
  * shows the car's nickname when the Garage knows it, else the shortened UID.
  */
 import { useCallback, useState } from 'react';
-import { FlatList, Pressable, StyleSheet, Text, View } from 'react-native';
+import { FlatList, Pressable, Share, StyleSheet, Text, View } from 'react-native';
 import { useSafeAreaInsets } from 'react-native-safe-area-context';
 import { Link, useFocusEffect, useLocalSearchParams, useRouter } from 'expo-router';
 
@@ -14,6 +14,7 @@ import { getSessionRepository } from '@/store/persistence/historyAccess';
 import type { SessionPass, SessionSummary } from '@/store/persistence/sessionRepository';
 import { useSettingsStore } from '@/store/settingsStore';
 import { speedUnitLabel } from '@/speed/format';
+import { sessionShareText } from '@/share/summary';
 import { carLabel, shortUid } from '@/garage/format';
 import { colors, fontSize, fontWeight, radius, spacing } from '@/theme/tokens';
 import {
@@ -65,6 +66,19 @@ export default function SessionDetailScreen() {
     return car ? carLabel(car) : shortUid(uid);
   };
 
+  const canShare = !!session && !!passes && passes.length > 0;
+  const onShare = () => {
+    if (!session || !passes) return;
+    const carNames = new Map(
+      cars
+        .filter((c) => c.name?.trim())
+        .map((c) => [c.uid, c.name!.trim()] as const),
+    );
+    Share.share({
+      message: sessionShareText(session, passes, { display: speedDisplay, carNames }),
+    }).catch(() => {});
+  };
+
   return (
     <View style={[styles.screen, { paddingTop: insets.top + spacing(2) }]}>
       <View style={styles.header}>
@@ -75,6 +89,16 @@ export default function SessionDetailScreen() {
         >
           <Text style={styles.backText}>‹ History</Text>
         </Pressable>
+        <View style={styles.headerSpacer} />
+        {canShare && (
+          <Pressable
+            hitSlop={12}
+            onPress={onShare}
+            style={({ pressed }) => [styles.share, pressed && styles.pressed]}
+          >
+            <Text style={styles.shareText}>Share</Text>
+          </Pressable>
+        )}
       </View>
 
       <View style={styles.summary}>
@@ -147,6 +171,9 @@ const styles = StyleSheet.create({
   },
   back: { paddingVertical: spacing(1), paddingRight: spacing(1) },
   backText: { color: colors.accentBlue, fontSize: fontSize.md, fontWeight: fontWeight.medium },
+  headerSpacer: { flex: 1 },
+  share: { paddingVertical: spacing(1), paddingLeft: spacing(1) },
+  shareText: { color: colors.accent, fontSize: fontSize.md, fontWeight: fontWeight.bold },
   summary: { paddingHorizontal: spacing(5), paddingBottom: spacing(3), gap: 4 },
   summaryDate: { color: colors.textPrimary, fontSize: fontSize.xl, fontWeight: fontWeight.heavy },
   summaryMeta: { color: colors.textSecondary, fontSize: fontSize.sm },

diff --git a/apps/mobile/src/app/race.tsx b/apps/mobile/src/app/race.tsx
@@ -21,6 +21,7 @@ import {
   Platform,
   Pressable,
   ScrollView,
+  Share,
   StyleSheet,
   Text,
   TextInput,
@@ -33,8 +34,10 @@ import { useReducedMotion } from 'react-native-reanimated';
 
 import { LAP_OPTIONS, currentLapElapsed, type RaceResult } from '@/race/raceEngine';
 import { useRaceStore } from '@/store/raceStore';
+import { useGarageStore } from '@/store/garageStore';
 import { usePortalStore } from '@/store/portalStore';
 import { useSettingsStore } from '@/store/settingsStore';
+import { raceShareText } from '@/share/summary';
 import { getActiveTransportControls } from '@/transport/active';
 import { colors, fontSize, fontWeight, radius, spacing } from '@/theme/tokens';
 
@@ -369,6 +372,13 @@ function LapList({ lapTimes, bestLap }: { lapTimes: readonly number[]; bestLap:
 }
 
 function Results({ result, onAgain }: { result: RaceResult; onAgain: () => void }) {
+  const carName = useGarageStore((s) => s.cars.find((c) => c.uid === result.carUid)?.name ?? null);
+
+  const onShare = () => {
+    haptic(() => Haptics.selectionAsync());
+    Share.share({ message: raceShareText(result, { carName }) }).catch(() => {});
+  };
+
   return (
     <View style={styles.section}>
       <View style={styles.resultHero}>
@@ -387,6 +397,13 @@ function Results({ result, onAgain }: { result: RaceResult; onAgain: () => void
 
       <LapList lapTimes={result.lapTimes} bestLap={result.bestLap} />
 
+      <Pressable
+        onPress={onShare}
+        style={({ pressed }) => [styles.shareBtn, pressed && styles.pressed]}
+      >
+        <Text style={styles.shareBtnText}>Share result</Text>
+      </Pressable>
+
       <View style={styles.actionRow}>
         <Pressable
           onPress={onAgain}
@@ -577,6 +594,16 @@ const styles = StyleSheet.create({
 
   actionRow: { flexDirection: 'row', gap: spacing(2) },
   flex1: { flex: 1 },
+  shareBtn: {
+    backgroundColor: colors.surfaceAlt,
+    borderColor: colors.border,
+    borderWidth: 1,
+    borderRadius: radius.md,
+    paddingVertical: spacing(3),
+    alignItems: 'center',
+    marginBottom: spacing(2),
+  },
+  shareBtnText: { color: colors.accent, fontSize: fontSize.md, fontWeight: fontWeight.bold },
   ghostBtn: {
     backgroundColor: colors.surfaceAlt,
     borderColor: colors.border,

diff --git a/apps/mobile/src/share/summary.test.ts b/apps/mobile/src/share/summary.test.ts
@@ -0,0 +1,155 @@
+import { describe, expect, it } from 'vitest';
+
+import type { RaceResult } from '../race/raceEngine';
+import type { SessionPass, SessionSummary } from '../store/persistence/sessionRepository';
+import { formatLapTime, raceShareText, sessionShareText } from './summary';
+
+const EM_DASH = '\u2014';
+const FLASH = '\u26A1';
+
+function makeResult(over: Partial<RaceResult> = {}): RaceResult {
+  return {
+    player: 'Ben',
+    carUid: '6C:C4:5A:2B:64:81',
+    lapCount: 3,
+    lapTimes: [2.5, 2.1, 2.8],
+    totalTime: 7.4,
+    bestLap: 2.1,
+    bestLapNum: 2,
+    worstLap: 2.8,
+    worstLapNum: 3,
+    avgLap: 2.47,
+    finishedAt: 1_700_000_000_000,
+    ...over,
+  };
+}
+
+function makeSession(over: Partial<SessionSummary> = {}): SessionSummary {
+  return {
+    id: 1,
+    startedAt: 1_700_000_000_000,
+    endedAt: 1_700_000_090_000,
+    passCount: 3,
+    bestMph: 250,
+    ...over,
+  };
+}
+
+function makePass(over: Partial<SessionPass> = {}): SessionPass {
+  return {
+    id: 1,
+    sessionId: 1,
+    carUid: '6C:C4:5A:2B:64:81',
+    serial: null,
+    raw: 0,
+    scaleMph: 100,
+    at: 1_700_000_000_000,
+    ...over,
+  };
+}
+
+describe('formatLapTime', () => {
+  it('formats sub-minute as SS.sss', () => {
+    expect(formatLapTime(2.1)).toBe('2.10s');
+  });
+
+  it('rolls over past a minute to M:SS.ss', () => {
+    expect(formatLapTime(65)).toBe('1:05.00');
+  });
+
+  it('returns an em dash for non-finite input', () => {
+    expect(formatLapTime(Number.NaN)).toBe(EM_DASH);
+    expect(formatLapTime(Number.POSITIVE_INFINITY)).toBe(EM_DASH);
+  });
+});
+
+describe('raceShareText', () => {
+  it('summarizes a multi-lap race with splits and a lap list', () => {
+    const text = raceShareText(makeResult());
+    expect(text).toContain('Ben finished 3 laps in 7.40s');
+    expect(text).toContain('Car: 64:81'); // falls back to short UID
+    expect(text).toContain('Best lap 2.10s (lap 2)');
+    expect(text).toContain('Average 2.47s');
+    expect(text).toContain('Worst lap 2.80s (lap 3)');
+    expect(text).toContain('Laps:');
+    expect(text).toContain('via RedlineID');
+  });
+
+  it('flags the fastest lap in the lap list', () => {
+    const lines = raceShareText(makeResult()).split('\n');
+    expect(lines).toContain(`  2. 2.10s ${FLASH}`);
+    expect(lines).toContain('  1. 2.50s');
+    expect(lines).toContain('  3. 2.80s');
+  });
+
+  it('uses the singular lap label for a one-lap race', () => {
+    const text = raceShareText(makeResult({ lapCount: 1, lapTimes: [3.2], bestLapNum: 1, worstLapNum: 1 }));
+    expect(text).toContain('finished 1 lap in');
+  });
+
+  it('prefers a provided car nickname over the UID', () => {
+    const text = raceShareText(makeResult(), { carName: 'Twin Mill' });
+    expect(text).toContain('Car: Twin Mill');
+    expect(text).not.toContain('64:81');
+  });
+
+  it('omits the lap list when there are no recorded laps', () => {
+    const text = raceShareText(makeResult({ lapTimes: [] }));
+    expect(text).not.toContain('Laps:');
+    expect(text).toContain('via RedlineID');
+  });
+});
+
+describe('sessionShareText', () => {
+  const passes = [
+    makePass({ id: 1, scaleMph: 100, carUid: 'AA' }),
+    makePass({ id: 2, scaleMph: 250, carUid: 'BB' }),
+    makePass({ id: 3, scaleMph: 180, carUid: null }),
+  ];
+
+  it('recaps a session in mph with the fastest passes first', () => {
+    const text = sessionShareText(makeSession(), passes, {
+      carNames: new Map([['BB', 'Bone Shaker']]),
+    });
+    expect(text).toContain('Race session');
+    expect(text).toContain('3 passes');
+    expect(text).toContain('Best 250 mph');
+    const lines = text.split('\n');
+    expect(lines).toContain('Top 3 passes:');
+    expect(lines).toContain('  1. 250 mph \u2014 Bone Shaker'); // nickname from map
+    expect(lines).toContain('  2. 180 mph \u2014 Unknown car'); // null carUid
+    expect(lines).toContain('  3. 100 mph \u2014 AA'); // short UID fallback
+    expect(text).toContain('via RedlineID');
+  });
+
+  it('converts speeds and unit label to km/h', () => {
+    const text = sessionShareText(makeSession({ bestMph: 200 }), [makePass({ scaleMph: 200, carUid: 'AA' })], {
+      display: { unit: 'kmh', calibration: 1 },
+    });
+    expect(text).toContain('Best 322 km/h'); // 200 * 1.609344 = 321.87 -> 322
+    expect(text).toContain('  1. 322 km/h \u2014 AA');
+  });
+
+  it('applies a calibration trim to shared speeds', () => {
+    const text = sessionShareText(makeSession({ bestMph: 200 }), [], {
+      display: { unit: 'mph', calibration: 1.1 },
+    });
+    expect(text).toContain('Best 220 mph'); // 200 * 1.1
+  });
+
+  it('handles an empty session: em-dash best, no top list', () => {
+    const text = sessionShareText(makeSession({ passCount: 0, bestMph: 0 }), []);
+    expect(text).toContain(`Best ${EM_DASH} mph`);
+    expect(text).not.toContain('Top');
+    expect(text).toContain('via RedlineID');
+  });
+
+  it('respects topN and singular labels', () => {
+    const text = sessionShareText(makeSession({ passCount: 1 }), passes, { topN: 1 });
+    expect(text).toContain('1 pass');
+    const lines = text.split('\n');
+    expect(lines).toContain('Top pass:');
+    expect(lines).toContain('  1. 250 mph \u2014 BB');
+    expect(lines).not.toContain('  2. 180 mph \u2014 Unknown car');
+  });
+});
diff --git a/apps/mobile/src/share/summary.ts b/apps/mobile/src/share/summary.ts
@@ -0,0 +1,100 @@
+/**
+ * Pure builders for the human-shareable race & session summaries handed to the
+ * native Share sheet. Framework-free so they unit test under Node and stay
+ * consistent with what each screen renders (lap times mirror race.tsx's clock;
+ * speeds run through the same speed/format converter as every readout, so a
+ * shared number matches what the user sees for their chosen unit + calibration).
+ */
+import type { RaceResult } from '../race/raceEngine';
+import type { SessionPass, SessionSummary } from '../store/persistence/sessionRepository';
+import { shortUid } from '../garage/format';
+import { formatDuration, formatSessionDate } from '../history/format';
+import {
+  formatBestSpeed,
+  formatSpeedValue,
+  speedUnitLabel,
+  type SpeedDisplay,
+} from '../speed/format';
+
+const SIGNATURE = 'via RedlineID';
+
+/** Lap/total time as `SS.ss`s, rolling over to `M:SS.ss` past a minute (mirrors race.tsx). */
+export function formatLapTime(seconds: number): string {
+  if (!Number.isFinite(seconds)) return '\u2014';
+  if (seconds >= 60) {
+    const m = Math.floor(seconds / 60);
+    return `${m}:${(seconds - m * 60).toFixed(2).padStart(5, '0')}`;
+  }
+  return `${seconds.toFixed(2)}s`;
+}
+
+export interface RaceShareOpts {
+  /** The car's nickname, when known; falls back to the shortened UID. */
+  readonly carName?: string | null;
+}
+
+/** Celebratory recap of a finished race: total time, splits, and lap-by-lap. */
+export function raceShareText(result: RaceResult, opts: RaceShareOpts = {}): string {
+  const car = opts.carName?.trim() ? opts.carName.trim() : shortUid(result.carUid);
+  const laps = result.lapCount === 1 ? '1 lap' : `${result.lapCount} laps`;
+
+  const lines: string[] = [
+    `\u{1F3C1} ${result.player} finished ${laps} in ${formatLapTime(result.totalTime)}`,
+    `Car: ${car}`,
+    '',
+    `Best lap ${formatLapTime(result.bestLap)} (lap ${result.bestLapNum})`,
+    `Average ${formatLapTime(result.avgLap)}`,
+    `Worst lap ${formatLapTime(result.worstLap)} (lap ${result.worstLapNum})`,
+  ];
+
+  if (result.lapTimes.length > 0) {
+    lines.push('', 'Laps:');
+    result.lapTimes.forEach((t, i) => {
+      const flash = i + 1 === result.bestLapNum ? ' \u26A1' : '';
+      lines.push(`  ${i + 1}. ${formatLapTime(t)}${flash}`);
+    });
+  }
+
+  lines.push('', SIGNATURE);
+  return lines.join('\n');
+}
+
+export interface SessionShareOpts {
+  /** Unit + calibration so shared speeds match the on-screen readouts. */
+  readonly display?: SpeedDisplay;
+  /** Optional car nicknames keyed by UID, used to label the top passes. */
+  readonly carNames?: ReadonlyMap<string, string>;
+  /** How many of the fastest passes to list (default 3). */
+  readonly topN?: number;
+}
+
+/** Recap of a saved session: date, pass count, duration, best, and the fastest passes. */
+export function sessionShareText(
+  session: SessionSummary,
+  passes: readonly SessionPass[],
+  opts: SessionShareOpts = {},
+): string {
+  const { display, carNames, topN = 3 } = opts;
+  const unit = speedUnitLabel(display?.unit ?? 'mph');
+  const passLabel = session.passCount === 1 ? '1 pass' : `${session.passCount} passes`;
+
+  const lines: string[] = [
+    `\u{1F3CE}\uFE0F Race session \u2014 ${formatSessionDate(session.startedAt)}`,
+    `${passLabel} \u00b7 ${formatDuration(session.startedAt, session.endedAt)}`,
+    `Best ${formatBestSpeed(session.bestMph, display)} ${unit}`,
+  ];
+
+  const top = [...passes].sort((a, b) => b.scaleMph - a.scaleMph).slice(0, Math.max(0, topN));
+  if (top.length > 0) {
+    lines.push('', top.length === 1 ? 'Top pass:' : `Top ${top.length} passes:`);
+    top.forEach((p, i) => {
+      const name = p.carUid
+        ? carNames?.get(p.carUid)?.trim() || shortUid(p.carUid)
+        : 'Unknown car';
+      lines.push(`  ${i + 1}. ${formatSpeedValue(p.scaleMph, display)} ${unit} \u2014 ${name}`);
+    });
+  }
+
+  lines.push('', SIGNATURE);
+  return lines.join('\n');
+}