first reading the start of a map with a 3 minute delay to overcome the transition period from the previous map

discord_verificiation/playtime-frontend/components/MapSessionTimelineChart.tsx

@@ -2,6 +2,7 @@
 
 import { useEffect, useState } from 'react';
 import { useContainerWidth } from '@/lib/useContainerWidth';
+import { START_BASELINE_MIN, START_BASELINE_MS } from '@/lib/populationBaseline';
 
 interface Point {
   t: string;
@@ -91,7 +92,18 @@ export default function MapSessionTimelineChart({ mapId }: { mapId: number }) {
   // right at map start vs. right at map end (or "now" if still running) —
   // same definition as the dumbbell chart, found by nearest bucket to each
   // boundary rather than a separate query.
-  const startPoint = mapStart != null ? findNearestPoint(xForEpoch(mapStart)) : null;
+  //
+  // The "start" reading is taken START_BASELINE_MS after the map begins, not
+  // at the exact change instant: right at the change the population is still
+  // the previous map's (people leaving/reconnecting), so reading it at t=0
+  // would blame this map for the previous one's attrition. Clamped to the
+  // map's end (or latest point, if still running) so short maps still work.
+  const lastPointEpoch = points.length > 0 ? points[points.length - 1].tEpoch : null;
+  const baselineEpoch =
+    mapStart != null
+      ? Math.min(mapStart + START_BASELINE_MS, mapEnd ?? lastPointEpoch ?? mapStart + START_BASELINE_MS)
+      : null;
+  const startPoint = baselineEpoch != null ? findNearestPoint(xForEpoch(baselineEpoch)) : null;
   const endPoint = mapEnd != null ? findNearestPoint(xForEpoch(mapEnd)) : points[points.length - 1] ?? null;
   const delta = startPoint && endPoint ? endPoint.players - startPoint.players : null;
   const deltaColor = delta == null ? '#8A9691' : delta > 0 ? '#3FD37A' : delta < 0 ? '#E0665C' : '#8A9691';
@@ -105,7 +117,7 @@ export default function MapSessionTimelineChart({ mapId }: { mapId: number }) {
         <h2 className="text-lg text-ink">Population during this map</h2>
         {startPoint && endPoint && (
           <p className="text-sm text-ink-muted mt-1">
-            Started with <span className="text-ink">{startPoint.players}</span> players, ended with{' '}
+            Had <span className="text-ink">{startPoint.players}</span> players {START_BASELINE_MIN} min in, ended with{' '}
             <span className="text-ink">{endPoint.players}</span>
             <span style={{ color: deltaColor }}>
               {' '}

discord_verificiation/playtime-frontend/lib/mapImpact.ts

@@ -1,5 +1,6 @@
 import { query } from '@/lib/db';
 import { parseDbDate } from '@/lib/dates';
+import { START_BASELINE_MS } from '@/lib/populationBaseline';
 
 // --- Why this exists ---------------------------------------------------
 //
@@ -120,7 +121,11 @@ async function computeMapImpactStats(): Promise<MapImpactSummary[]> {
     const durationMs = nextStartMs - startMs;
     if (durationMs < MIN_REAL_PERIOD_MS) continue; // tickrate-restart artifact, not a real occurrence
 
-    const startPlayers = populationAt(startMs);
+    // Read the starting population START_BASELINE_MS into the map rather than
+    // at the exact change instant, so players still leaving the previous map
+    // aren't counted against this one. Clamped to the occurrence's end (it is
+    // always >= 2 min long here, but may be shorter than the baseline).
+    const startPlayers = populationAt(Math.min(startMs + START_BASELINE_MS, nextStartMs));
     const endPlayers = populationAt(nextStartMs);
     const netChange = endPlayers - startPlayers;
     const retentionPct = startPlayers > 0 ? (endPlayers / startPlayers) * 100 : null;

discord_verificiation/playtime-frontend/lib/populationBaseline.ts

@@ -0,0 +1,8 @@
+// How long after a map starts we wait before reading its "starting"
+// population. At the exact instant of a map change the player count is still
+// the previous map's (people leaving or reconnecting), so reading it at t=0
+// would blame the new map for attrition that happened before/around the
+// change. Shared by the leaderboard, the population chart SQL and the
+// per-session timeline so all three agree. Safe to import from client code.
+export const START_BASELINE_MIN = 3;
+export const START_BASELINE_MS = START_BASELINE_MIN * 60_000;

discord_verificiation/playtime-frontend/lib/queries.ts

@@ -1,4 +1,5 @@
 import { query } from '@/lib/db';
+import { START_BASELINE_MIN } from '@/lib/populationBaseline';
 
 // map_end_dt was dropped from the schema — it was redundant with (and
 // occasionally got out of sync with) the next row's map_start_dt, since a
@@ -123,8 +124,8 @@ export async function getMapPopulationSeries(limit = 40, before?: string): Promi
           AND (s.session_end_dt IS NULL OR s.session_end_dt > m.map_start_dt)
        ) AS total_players,
        (SELECT COUNT(DISTINCT s.steamid) FROM playtime_display_sessions s
-        WHERE s.session_start_dt <= m.map_start_dt
+        WHERE s.session_start_dt <= LEAST(m.map_start_dt + INTERVAL ${START_BASELINE_MIN} MINUTE, COALESCE(${NEXT_MAP_START('m')}, NOW()))
-          AND (s.session_end_dt IS NULL OR s.session_end_dt > m.map_start_dt)
+          AND (s.session_end_dt IS NULL OR s.session_end_dt > LEAST(m.map_start_dt + INTERVAL ${START_BASELINE_MIN} MINUTE, COALESCE(${NEXT_MAP_START('m')}, NOW())))
        ) AS start_players,
        (SELECT COUNT(DISTINCT s.steamid) FROM playtime_display_sessions s
         WHERE s.session_start_dt <= COALESCE(${NEXT_MAP_START('m')}, NOW())