diff --git a/src/app/api/fee-compare/route.ts b/src/app/api/fee-compare/route.ts
index 6e64189c2..f79297d36 100644
--- a/src/app/api/fee-compare/route.ts
+++ b/src/app/api/fee-compare/route.ts
@@ -706,7 +706,8 @@ function buildHlWalletData(
 function reconstructHlPositions(fills: HlFill[], cutoffMs: number): PositionSlice[] {
   const state = new Map<string, { sz: number; openTs: number; openPx: number; isLong: boolean }>();
   const slices: PositionSlice[] = [];
-  const sorted = fills.filter((f) => f.time >= cutoffMs).sort((a, b) => a.time - b.time);
+  // Process ALL fills chronologically so positions opened before cutoffMs are visible
+  const sorted = fills.slice().sort((a, b) => a.time - b.time);
 
   for (const f of sorted) {
     const sz = parseFloat(f.sz);
@@ -724,7 +725,12 @@ function reconstructHlPositions(fills: HlFill[], cutoffMs: number): PositionSlic
       const pos = state.get(key);
       if (pos && pos.sz > 0) {
         const closeSz = Math.min(sz, pos.sz);
-        slices.push({ coin: f.coin, notionalUsd: closeSz * pos.openPx, openMs: pos.openTs, closeMs: f.time, isLong });
+        // Cap slice start to cutoffMs so carry is only for the measurement window
+        const sliceOpen = Math.max(pos.openTs, cutoffMs);
+        const sliceClose = f.time;
+        if (sliceClose > cutoffMs) {
+          slices.push({ coin: f.coin, notionalUsd: closeSz * pos.openPx, openMs: sliceOpen, closeMs: sliceClose, isLong });
+        }
         pos.sz -= closeSz;
         if (pos.sz < 0.00001) state.delete(key);
         else state.set(key, pos);
@@ -732,7 +738,7 @@ function reconstructHlPositions(fills: HlFill[], cutoffMs: number): PositionSlic
     }
   }
 
-  // Still-open positions — close at now
+  // Still-open positions — close at now, cap open to cutoffMs
   const now = Date.now();
   for (const [key, pos] of state) {
     if (pos.sz > 0.00001) {
@@ -742,7 +748,7 @@ function reconstructHlPositions(fills: HlFill[], cutoffMs: number): PositionSlic
         slices.push({
           coin,
           notionalUsd: pos.sz * parseFloat(lastFill.px),
-          openMs: pos.openTs,
+          openMs: Math.max(pos.openTs, cutoffMs),
           closeMs: now,
           isLong: pos.isLong,
         });
diff --git a/src/app/sitemap.xml/route.ts b/src/app/sitemap.xml/route.ts
index 69348443c..709354229 100644
--- a/src/app/sitemap.xml/route.ts
+++ b/src/app/sitemap.xml/route.ts
@@ -15,11 +15,15 @@ import { buildSitemap } from "@/lib/sitemap-builder";
 // serialized to XML here and shipped with a real edge cache header.
 export const runtime = "nodejs";
 export const dynamic = "force-dynamic";
-// Hard platform ceiling so Vercel never holds the connection open longer
-// than this when the SRH/Redis fan-out runs over budget. The internal
-// buildSitemap() timeout is 20 s; this gives 40 s of headroom and still
-// replies well within the smoke-test's 90 s limit.
-export const maxDuration = 60;
+// 300 s: the aggregate blob is 4.25 MB — larger than Next.js Data Cache's
+// 2 MB limit, so unstable_cache can never store it and every request must
+// re-fetch from the network. The /api/aggregate ISR proxy responds in
+// 18-65 s on a cold cache. With maxDuration=60 the process received
+// SIGKILL before the fetch resolved, discarding the buffered response and
+// returning 500. 300 s gives the full build time to complete on cold
+// starts; the internal JS timeout (240 s) fires first and falls back to
+// the static sitemap if the full build hangs.
+export const maxDuration = 300;
 
 function escapeXml(s: string): string {
   return s
diff --git a/src/lib/sitemap-builder.ts b/src/lib/sitemap-builder.ts
index 669fae044..957b39f8c 100644
--- a/src/lib/sitemap-builder.ts
+++ b/src/lib/sitemap-builder.ts
@@ -577,11 +577,13 @@ async function buildFullSitemap(): Promise<MetadataRoute.Sitemap> {
 
 export async function buildSitemap(): Promise<MetadataRoute.Sitemap> {
   try {
-    // 20 s: tight enough to reply well within the smoke-test's 90 s window
-    // even if the static fallback itself takes a few seconds. The Vercel
-    // maxDuration on the route is 60 s; this leaves 40 s of headroom.
+    // 240 s: maxDuration on the route is 300 s. The aggregate blob (4.25 MB)
+    // exceeds Next.js Data Cache's 2 MB cap, so every sitemap request
+    // re-fetches from /api/aggregate whose FETCH_TIMEOUT_MS is 65 s. A 240 s
+    // budget covers cold aggregate + HL-builder Prometheus sweeps with 60 s of
+    // headroom for buildStaticFallback() before the 300 s SIGKILL ceiling.
     const timeout = new Promise<never>((_, reject) =>
-      setTimeout(() => reject(new Error("sitemap build timeout")), 20_000),
+      setTimeout(() => reject(new Error("sitemap build timeout")), 240_000),
     );
     // Attach a no-op .catch() to prevent unhandled-rejection crashes if
     // buildFullSitemap() rejects AFTER the race has already settled (via