From 74625acce9e16381aeb27020496f24b1791de4d3 Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Thu, 29 Oct 2026 12:23:42 +0000
Subject: [PATCH] refactor(router): compare tail and prefix segments in place

`matchesSegment` was a one-line function shared by `matchesCatchAll` and
the prefix matcher. Comparing in place spares V8 a function to set up at
import and to compile on the first request that reaches a catch-all or a
prefix with a param.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VVaw7Sutbw6xMTMyDFeNfw
---
 packages/router/src/index.ts | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/packages/router/src/index.ts b/packages/router/src/index.ts
index c6af03f..b98cff7 100644
--- a/packages/router/src/index.ts
+++ b/packages/router/src/index.ts
@@ -323,7 +323,9 @@ export function createPrefixMatcher(prefix: `/${string}`): (pathname: `/${string
         end = pathname.length
       }
 
-      if (!matchesSegment(expected, decode(pathname.slice(start, end)))) {
+      // `undefined` stands for a param, which needs a non-empty segment.
+      const segment = decode(pathname.slice(start, end))
+      if (expected === undefined ? segment === '' : segment !== expected) {
         return false
       }
 
@@ -627,7 +629,10 @@ function matchesCatchAll(
   }
 
   for (let i = 0; i < tail.length; i++) {
-    if (!matchesSegment(tail[i], segments[end + i]!)) {
+    const expected = tail[i]
+    const segment = segments[end + i]!
+    // `undefined` stands for a param, which needs a non-empty segment.
+    if (expected === undefined ? segment === '' : segment !== expected) {
       return false
     }
   }
@@ -635,10 +640,6 @@ function matchesCatchAll(
   return true
 }
 
-function matchesSegment(expected: string | undefined, segment: string): boolean {
-  return expected === undefined ? segment !== '' : segment === expected
-}
-
 // `params` is spread only for a param named `__proto__`, not on every pass.
 /* oxlint-disable oxc/no-accumulating-spread */
 function toParams<T>(route: Route<T>, segments: readonly string[]): Record<string, string> {