From ce8c7878dfc859fc41277e30db26700e1cb1b334 Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Sat, 22 Aug 2026 20:51:03 +0000
Subject: [PATCH] perf(ui): optimize time formatting with pre-computed array
 lookups

---
 .jules/bolt.md                             |  3 +++
 src/cli/ui/components/messageList/utils.ts | 10 +++++++---
 2 files changed, 10 insertions(+), 3 deletions(-)
 create mode 100644 .jules/bolt.md

diff --git a/.jules/bolt.md b/.jules/bolt.md
new file mode 100644
index 00000000..93f39533
--- /dev/null
+++ b/.jules/bolt.md
@@ -0,0 +1,3 @@
+## 2026-08-22 - [Time Formatting Array Lookups]
+**Learning:** For high-throughput render paths in React `ink` terminal UIs, prefer pre-computed array lookups for bounded data (like time formatting 0-59) over repeated string allocations (like `String().padStart()`) to reduce performance overhead.
+**Action:** When implementing rendering logic that formats small ranges of numbers, utilize pre-computed lookup tables to minimize string allocations.
diff --git a/src/cli/ui/components/messageList/utils.ts b/src/cli/ui/components/messageList/utils.ts
index ca9a3ed9..72003ac2 100644
--- a/src/cli/ui/components/messageList/utils.ts
+++ b/src/cli/ui/components/messageList/utils.ts
@@ -1,6 +1,10 @@
+const PAD_2 = Array.from({ length: 60 }, (_, i) => (i < 10 ? `0${i}` : `${i}`));
+
 export function formatTime(timestamp: Date): string {
-  const hours = String(timestamp.getHours()).padStart(2, '0');
-  const minutes = String(timestamp.getMinutes()).padStart(2, '0');
-  const seconds = String(timestamp.getSeconds()).padStart(2, '0');
+  // Performance: Pre-computed array lookups for 0-59 are faster than String().padStart()
+  // avoiding repeated string allocations in high-throughput render paths.
+  const hours = PAD_2[timestamp.getHours()];
+  const minutes = PAD_2[timestamp.getMinutes()];
+  const seconds = PAD_2[timestamp.getSeconds()];
   return `${hours}:${minutes}:${seconds}`;
 }