diff --git a/.jules/bolt.md b/.jules/bolt.md
new file mode 100644
index 0000000..a3e2a14
--- /dev/null
+++ b/.jules/bolt.md
@@ -0,0 +1,3 @@
+## 2025-02-28 - Replace O(n) Array Filtering with Binary Search on Timeseries Data
+**Learning:** During backtesting, `priceOverride` and `vnindexAt` functions were evaluating closures at every turn in a loop. Both were using O(n) `Array.prototype.filter()` over long chronologically-sorted price arrays simply to find the last item prior to `asOf`, constantly allocating arrays.
+**Action:** Always prefer binary search O(log n) lookups over array filtering on chronologically sorted timeseries datasets (like OHLCV arrays), especially when fetching historical state repeatedly. Added `findLastBarIndex` to abstract this logic out.
diff --git a/package.json b/package.json
index dd2a5c4..860866e 100644
--- a/package.json
+++ b/package.json
@@ -55,13 +55,13 @@
   "dependencies": {
     "@anthropic-ai/claude-agent-sdk": "^0.1.0",
     "better-sqlite3": "^11.5.0",
-    "cheerio": "^1.0.0",
+    "cheerio": "^1.2.0",
     "ink": "^5.0.1",
     "ink-spinner": "^5.0.0",
     "ink-text-input": "^6.0.0",
     "react": "^18.3.1",
     "technicalindicators": "^3.1.0",
-    "undici": "^6.20.0",
+    "undici": "^6.27.0",
     "yaml": "^2.6.0",
     "zod": "^3.23.8"
   },
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 8e3f135..96ba374 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -15,7 +15,7 @@ importers:
         specifier: ^11.5.0
         version: 11.10.0
       cheerio:
-        specifier: ^1.0.0
+        specifier: ^1.2.0
         version: 1.2.0
       ink:
         specifier: ^5.0.1
@@ -33,8 +33,8 @@ importers:
         specifier: ^3.1.0
         version: 3.1.0
       undici:
-        specifier: ^6.20.0
-        version: 6.25.0
+        specifier: ^6.27.0
+        version: 6.27.0
       yaml:
         specifier: ^2.6.0
         version: 2.8.3
@@ -1516,12 +1516,12 @@ packages:
   undici-types@6.21.0:
     resolution: {integrity: sha512-iwDZqg0QAGrg9Rav5H4n0M64c3mkR59cJ6wQp+7C4nI0gsmExaedaYLNO44eT4AtBBwjbTiGPMlt2Md0T9H9JQ==}
 
-  undici@6.25.0:
-    resolution: {integrity: sha512-ZgpWDC5gmNiuY9CnLVXEH8rl50xhRCuLNA97fAUnKi8RRuV4E6KG31pDTsLVUKnohJE0I3XDrTeEydAXRw47xg==}
+  undici@6.27.0:
+    resolution: {integrity: sha512-YmfV3YnEDzXRC5lZ2jWtWWHKGUm1zIt8AhesR1tens+HTNv+YZlN/dp6G727LOvMJ8xjP9Be7Y2Sdr96LDm+pg==}
     engines: {node: '>=18.17'}
 
-  undici@7.25.0:
-    resolution: {integrity: sha512-xXnp4kTyor2Zq+J1FfPI6Eq3ew5h6Vl0F/8d9XU5zZQf1tX9s2Su1/3PiMmUANFULpmksxkClamIZcaUqryHsQ==}
+  undici@7.28.0:
+    resolution: {integrity: sha512-cRZYrTDwWznlnRiPjggAGxZXanty6M8RV1ff8Wm4LWXBp7/IG8v5DnOm74DtUBp9OONpK75YlPnIjQqX0dBDtA==}
     engines: {node: '>=20.18.1'}
 
   universalify@0.1.2:
@@ -1622,8 +1622,8 @@ packages:
   wrappy@1.0.2:
     resolution: {integrity: sha512-l4Sp/DRseor9wL6EvV2+TuQn63dMkPjZ/sp9XkghTEbV9KlPS1xUsZ3u7/IQO4wxtcFB4bgpQPRcR3QCvezPcQ==}
 
-  ws@8.20.0:
-    resolution: {integrity: sha512-sAt8BhgNbzCtgGbt2OxmpuryO63ZoDk/sqaB/znQm94T4fCEsy/yV+7CdC1kJhOU9lboAEU7R3kquuycDoibVA==}
+  ws@8.21.0:
+    resolution: {integrity: sha512-Vsp28b7DRcimFQvrqu2Wek3z1iYxDCWqHYB8Qsnk/S4RfaCQzPGPyBNuVjJV3cd6UiKtUtp6sNM77gWvzcCH+g==}
     engines: {node: '>=10.0.0'}
     peerDependencies:
       bufferutil: ^4.0.1
@@ -2281,7 +2281,7 @@ snapshots:
       parse5: 7.3.0
       parse5-htmlparser2-tree-adapter: 7.1.0
       parse5-parser-stream: 7.1.2
-      undici: 7.25.0
+      undici: 7.28.0
       whatwg-mimetype: 4.0.0
 
   chownr@1.1.4: {}
@@ -2590,7 +2590,7 @@ snapshots:
       type-fest: 4.41.0
       widest-line: 5.0.0
       wrap-ansi: 9.0.2
-      ws: 8.20.0
+      ws: 8.21.0
       yoga-layout: 3.2.1
     optionalDependencies:
       '@types/react': 18.3.28
@@ -2986,9 +2986,9 @@ snapshots:
 
   undici-types@6.21.0: {}
 
-  undici@6.25.0: {}
+  undici@6.27.0: {}
 
-  undici@7.25.0: {}
+  undici@7.28.0: {}
 
   universalify@0.1.2: {}
 
@@ -3083,7 +3083,7 @@ snapshots:
 
   wrappy@1.0.2: {}
 
-  ws@8.20.0: {}
+  ws@8.21.0: {}
 
   yaml@2.8.3: {}
 
diff --git a/src/agent/backtestRunner.ts b/src/agent/backtestRunner.ts
index e91de2c..1875970 100644
--- a/src/agent/backtestRunner.ts
+++ b/src/agent/backtestRunner.ts
@@ -2,7 +2,7 @@ import { randomUUID } from "node:crypto";
 import { loadConfig } from "../config/loader.js";
 import { getDb } from "../storage/db.js";
 import { getBacktestBroker } from "../broker/index.js";
-import { getStockOhlcv, getIndexOhlcv, type Bar } from "../data/sources/dnsePublic.js";
+import { getStockOhlcv, getIndexOhlcv, findLastBarIndex, type Bar } from "../data/sources/dnsePublic.js";
 import { DISCOVERY_UNIVERSE, discoverTickers } from "../tools/discover.js";
 import { setActiveAsOf } from "./clock.js";
 import { runTeamAnalysis } from "./team/index.js";
@@ -298,8 +298,9 @@ export async function runBacktestSession(
   );
 
   const vnindexAt = (asOf: number): number | null => {
-    const series = vnindex.filter((b) => b.time <= asOf);
-    return series.length ? series[series.length - 1]!.close : null;
+    if (vnindex.length === 0) return null;
+    const lastIdx = findLastBarIndex(vnindex, asOf);
+    return lastIdx !== -1 ? vnindex[lastIdx]!.close : null;
   };
   const vnindexBaseline = vnindexAt(intervalTurns[0]!);
   if (vnindexBaseline == null) throw new Error(`no VNINDEX data at first ${interval.label} turn`);
@@ -312,8 +313,10 @@ export async function runBacktestSession(
       throwIfAborted(cb.signal);
       const dateIso = ictLabel(asOf);
       const priceOverride = (sym: string): number | null => {
-        const series = bars[sym]?.filter((b) => b.time <= asOf) ?? [];
-        return series.length ? series[series.length - 1]!.close : null;
+        const series = bars[sym];
+        if (!series || series.length === 0) return null;
+        const lastIdx = findLastBarIndex(series, asOf);
+        return lastIdx !== -1 ? series[lastIdx]!.close : null;
       };
       broker.setPriceOverride(priceOverride);
       cb.onTurnStart?.({ asOf, dateIso });
diff --git a/src/data/sources/dnsePublic.ts b/src/data/sources/dnsePublic.ts
index 151733c..f60315c 100644
--- a/src/data/sources/dnsePublic.ts
+++ b/src/data/sources/dnsePublic.ts
@@ -24,6 +24,27 @@ export interface Bar {
   volume: number;
 }
 
+/**
+ * Finds the index of the last bar that occurred on or before a given timestamp.
+ * Assumes the bars array is sorted chronologically by time.
+ * Time complexity: O(log n)
+ */
+export function findLastBarIndex(bars: Bar[], time: number): number {
+  let low = 0;
+  let high = bars.length - 1;
+  let ans = -1;
+  while (low <= high) {
+    const mid = (low + high) >> 1;
+    if (bars[mid]!.time <= time) {
+      ans = mid;
+      low = mid + 1;
+    } else {
+      high = mid - 1;
+    }
+  }
+  return ans;
+}
+
 async function fetchOhlcs(
   kind: "stock" | "index",
   symbol: string,
@@ -66,9 +87,12 @@ function clipBars(bars: Bar[]): Bar[] {
   // is set, fall through unchanged — DNSE only returns historical data anyway.
   const hasOverride =
     asOfClock.getStore()?.asOfSec != null || isAsOfOverridden();
-  if (!hasOverride) return bars;
+  if (!hasOverride || bars.length === 0) return bars;
   const asOf = nowSec();
-  return bars.filter((b) => b.time <= asOf);
+  const lastIdx = findLastBarIndex(bars, asOf);
+  if (lastIdx === -1) return [];
+  // slice is O(1) conceptually and much faster than O(n) filter
+  return bars.slice(0, lastIdx + 1);
 }
 
 export async function getStockOhlcv(