From 646f8791723c727cffdf4081ba6af9bd124f940d Mon Sep 17 00:00:00 2001
From: yuki0418 <keryuuki0418@gmail.com>
Date: Fri, 22 Aug 2025 17:06:14 +0900
Subject: [PATCH] fix: resolve_route prevent dropping a trailing slash of id

---
 .changeset/every-kings-wink.md         |  5 +++++
 packages/kit/src/utils/routing.js      |  5 ++++-
 packages/kit/src/utils/routing.spec.js | 30 ++++++++++++++++++++++++++
 3 files changed, 39 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/every-kings-wink.md

diff --git a/.changeset/every-kings-wink.md b/.changeset/every-kings-wink.md
new file mode 100644
index 000000000000..6d643e8ac53a
--- /dev/null
+++ b/.changeset/every-kings-wink.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: resolve_route prevent dropping a trailing slash of id
diff --git a/packages/kit/src/utils/routing.js b/packages/kit/src/utils/routing.js
index ee129976b6e4..f36988f370b8 100644
--- a/packages/kit/src/utils/routing.js
+++ b/packages/kit/src/utils/routing.js
@@ -240,6 +240,8 @@ const basic_param_pattern = /\[(\[)?(\.\.\.)?(\w+?)(?:=(\w+))?\]\]?/g;
  */
 export function resolve_route(id, params) {
 	const segments = get_route_segments(id);
+	const has_id_trailing_slash = id != '/' && id.endsWith('/');
+
 	return (
 		'/' +
 		segments
@@ -262,7 +264,8 @@ export function resolve_route(id, params) {
 				})
 			)
 			.filter(Boolean)
-			.join('/')
+			.join('/') +
+		(has_id_trailing_slash ? '/' : '')
 	);
 }
 
diff --git a/packages/kit/src/utils/routing.spec.js b/packages/kit/src/utils/routing.spec.js
index 03ab03af3c78..75f5487eb2fa 100644
--- a/packages/kit/src/utils/routing.spec.js
+++ b/packages/kit/src/utils/routing.spec.js
@@ -278,30 +278,60 @@ describe('resolve_route', () => {
 			params: { one: 'one', two: 'two' },
 			expected: '/blog/one/two'
 		},
+		{
+			route: '/blog/[one]/[two]/',
+			params: { one: 'one', two: 'two' },
+			expected: '/blog/one/two/'
+		},
 		{
 			route: '/blog/[one=matcher]/[...two]',
 			params: { one: 'one', two: 'two/three' },
 			expected: '/blog/one/two/three'
 		},
+		{
+			route: '/blog/[one=matcher]/[...two]/',
+			params: { one: 'one', two: 'two/three' },
+			expected: '/blog/one/two/three/'
+		},
 		{
 			route: '/blog/[one=matcher]/[[two]]',
 			params: { one: 'one' },
 			expected: '/blog/one'
 		},
+		{
+			route: '/blog/[one=matcher]/[[two]]/',
+			params: { one: 'one' },
+			expected: '/blog/one/'
+		},
 		{
 			route: '/blog/[one]/[two]-and-[three]',
 			params: { one: 'one', two: '2', three: '3' },
 			expected: '/blog/one/2-and-3'
 		},
+		{
+			route: '/blog/[one]/[two]-and-[three]/',
+			params: { one: 'one', two: '2', three: '3' },
+			expected: '/blog/one/2-and-3/'
+		},
 		{
 			route: '/blog/[...one]',
 			params: { one: '' },
 			expected: '/blog'
 		},
+		{
+			route: '/blog/[...one]/',
+			params: { one: '' },
+			expected: '/blog/'
+		},
 		{
 			route: '/blog/[one]/[...two]-not-three',
 			params: { one: 'one', two: 'two/2' },
 			expected: '/blog/one/two/2-not-three'
+		},
+		{
+			route: '/blog/[one]/[...two]-not-three/',
+			params: { one: 'one', two: 'two/2' },
+			expected: '/blog/one/two/2-not-three/'
 		}
 	];