From 802fa3e44b8ed88d0a3ce873a030a4beb18add16 Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Fri, 21 Aug 2026 16:32:16 +0000
Subject: [PATCH] feat: add fast-path to for_each_char_match_start

Extracts first-character ASCII conversions out of the search hot loop
to prevent redundant iterations when checking common prefixes. Reduces
baseline iteration overhead during full-scrollback searches.

Co-authored-by: Lucenx9 <185146821+Lucenx9@users.noreply.github.com>
---
 .jules/bolt.md                                     |  3 +++
 .../forktty-ui-gtk/src/gtk_app/terminal_search.rs  | 14 ++++++++++++--
 2 files changed, 15 insertions(+), 2 deletions(-)
 create mode 100644 .jules/bolt.md

diff --git a/.jules/bolt.md b/.jules/bolt.md
new file mode 100644
index 00000000..98628f6d
--- /dev/null
+++ b/.jules/bolt.md
@@ -0,0 +1,3 @@
+## 2024-05-18 - [Terminal Search Fast-path Optimization]
+**Learning:** Hoisting the first-character case-conversion out of the search hot loop `for_each_char_match_start` significantly reduces overhead.
+**Action:** In search loops, perform the expensive `.to_ascii_lowercase()`/`.to_ascii_uppercase()` once before the loop, and use it inside the fast path.
diff --git a/crates/forktty-ui-gtk/src/gtk_app/terminal_search.rs b/crates/forktty-ui-gtk/src/gtk_app/terminal_search.rs
index 90694aa2..8a115106 100644
--- a/crates/forktty-ui-gtk/src/gtk_app/terminal_search.rs
+++ b/crates/forktty-ui-gtk/src/gtk_app/terminal_search.rs
@@ -75,11 +75,21 @@ fn for_each_char_match_start(
         return;
     }
     let first_needle = needle[0];
+    let first_lower = first_needle.to_ascii_lowercase();
+    let first_upper = first_needle.to_ascii_uppercase();
+
     let mut index = 0;
     while index + needle.len() <= haystack.len() {
+        let h = haystack[index];
         // Fast-path: short-circuit the full substring check if the first character
-        // doesn't match, avoiding iterator overhead in the common case.
-        if !chars_eq_ignore_case(haystack[index], first_needle) {
+        // doesn't match. We can only short-circuit if BOTH the haystack character
+        // AND the needle character are ASCII. Non-ASCII characters might case-fold
+        // to ASCII (e.g., Kelvin sign U+212A folds to 'k').
+        if h != first_lower && h != first_upper && h.is_ascii() && first_needle.is_ascii() {
+            index += 1;
+            continue;
+        }
+        if !chars_eq_ignore_case(h, first_needle) {
             index += 1;
             continue;
         }