From d9f82c18f1f4a448743504dcaf40ccd45ae191a3 Mon Sep 17 00:00:00 2001
From: Nic Polumeyv <162764842+Nic-Polumeyv@users.noreply.github.com>
Date: Wed, 29 Jul 2026 15:05:32 -0400
Subject: [PATCH 1/5] fix: generate valid `Path` types for routes with an
 optional first segment or several params in one segment

---
 .changeset/app-types-path-template.md         |  5 +++
 packages/kit/src/core/sync/write_app_types.js | 40 +++++++++++++------
 .../sync/write_types/test/app-types/+page.js  | 12 +++++-
 .../test/app-types/[[a]]/[[b]]/deep/+page.js  |  0
 .../test/app-types/[[lang]]/about/+page.js    |  0
 .../multi-param/[foo]-[bar]/+page.js          |  0
 packages/kit/src/utils/routing.js             |  2 +-
 7 files changed, 44 insertions(+), 15 deletions(-)
 create mode 100644 .changeset/app-types-path-template.md
 create mode 100644 packages/kit/src/core/sync/write_types/test/app-types/[[a]]/[[b]]/deep/+page.js
 create mode 100644 packages/kit/src/core/sync/write_types/test/app-types/[[lang]]/about/+page.js
 create mode 100644 packages/kit/src/core/sync/write_types/test/app-types/multi-param/[foo]-[bar]/+page.js

diff --git a/.changeset/app-types-path-template.md b/.changeset/app-types-path-template.md
new file mode 100644
index 000000000000..a4d93cb620df
--- /dev/null
+++ b/.changeset/app-types-path-template.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: generate valid `Path` types for routes with an optional first segment or several params in one segment
diff --git a/packages/kit/src/core/sync/write_app_types.js b/packages/kit/src/core/sync/write_app_types.js
index e8a76fdc25d6..7d57a89d71cd 100644
--- a/packages/kit/src/core/sync/write_app_types.js
+++ b/packages/kit/src/core/sync/write_app_types.js
@@ -4,15 +4,31 @@ import { resolve_entry } from '../../utils/filesystem.js';
 import { posixify } from '../../utils/os.js';
 import { write_if_changed } from './utils.js';
 import { s } from '../../utils/misc.js';
-import { get_route_segments } from '../../utils/routing.js';
-
-const replace_optional_params = (/** @type {string} */ id) =>
-	id.replace(/\/\[\[[^\]]+\]\]/g, '${string}');
-const replace_required_params = (/** @type {string} */ id) =>
-	id.replace(/\/\[[^\]]+\]/g, '/${string}');
-/** Convert route ID to pathname by removing layout groups */
-const remove_group_segments = (/** @type {string} */ id) => {
-	return '/' + get_route_segments(id).join('/');
+import { basic_param_pattern, get_route_segments } from '../../utils/routing.js';
+
+const optional_param_pattern = /^\[\[[\w-]+(?:=[\w-]+)?\]\]$/;
+
+/**
+ * Convert a route ID to a pathname (relative to the base path) in which each param
+ * is replaced with `${string}`
+ * @param {string} id
+ */
+const get_pathname_pattern = (id) => {
+	let pathname = '';
+	let separator = '';
+
+	for (const segment of get_route_segments(id)) {
+		if (optional_param_pattern.test(segment)) {
+			// the segment can be absent, so `${string}` absorbs the adjacent `/`. TypeScript does not
+			// match a literal against two consecutive placeholders, so only add one
+			if (!pathname.endsWith('${string}')) pathname += '${string}';
+		} else {
+			pathname += separator + segment.replace(basic_param_pattern, '${string}');
+			separator = '/';
+		}
+	}
+
+	return pathname;
 };
 
 /**
@@ -192,8 +208,7 @@ function generate_app_types(manifest_data, config, dir) {
 	}
 
 	for (const route of manifest_data.routes) {
-		const pathname = remove_group_segments(route.id);
-		let normalized_pathname = pathname.slice(1);
+		const pathname = get_pathname_pattern(route.id);
 
 		/** @type {(path: string) => string} */
 		let serialise = s;
@@ -207,11 +222,10 @@ function generate_app_types(manifest_data, config, dir) {
 
 			dynamic_routes.push(route_type);
 
-			normalized_pathname = replace_required_params(replace_optional_params(pathname)).slice(1);
 			serialise = (p) => `\`${p}\` & {}`;
 		}
 
-		for (const p of get_pathnames_for_trailing_slash(normalized_pathname, route)) {
+		for (const p of get_pathnames_for_trailing_slash(pathname, route)) {
 			pathnames.add(serialise(p));
 		}
 
diff --git a/packages/kit/src/core/sync/write_types/test/app-types/+page.js b/packages/kit/src/core/sync/write_types/test/app-types/+page.js
index ee5b3a316821..12ec641ad53a 100644
--- a/packages/kit/src/core/sync/write_types/test/app-types/+page.js
+++ b/packages/kit/src/core/sync/write_types/test/app-types/+page.js
@@ -106,5 +106,15 @@ pathname = 'path-a/trailing-slash/never/layout/inside';
 
 // Test trailing-slash - always (endpoint) and never (page)
 pathname = 'path-a/trailing-slash/mixed';
-// eslint-disable-next-line @typescript-eslint/no-unused-vars
 pathname = 'path-a/trailing-slash/mixed/';
+
+// Test optional params, which can be omitted
+pathname = 'about';
+pathname = 'en/about';
+pathname = 'deep';
+pathname = 'en/deep';
+pathname = 'en/gb/deep';
+
+// Test multiple params in a single segment
+// eslint-disable-next-line @typescript-eslint/no-unused-vars
+pathname = 'multi-param/1-2';
diff --git a/packages/kit/src/core/sync/write_types/test/app-types/[[a]]/[[b]]/deep/+page.js b/packages/kit/src/core/sync/write_types/test/app-types/[[a]]/[[b]]/deep/+page.js
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/kit/src/core/sync/write_types/test/app-types/[[lang]]/about/+page.js b/packages/kit/src/core/sync/write_types/test/app-types/[[lang]]/about/+page.js
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/kit/src/core/sync/write_types/test/app-types/multi-param/[foo]-[bar]/+page.js b/packages/kit/src/core/sync/write_types/test/app-types/multi-param/[foo]-[bar]/+page.js
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/kit/src/utils/routing.js b/packages/kit/src/utils/routing.js
index fd66d3a4b778..9ae7066d03f4 100644
--- a/packages/kit/src/utils/routing.js
+++ b/packages/kit/src/utils/routing.js
@@ -260,7 +260,7 @@ function escape(str) {
 	);
 }
 
-const basic_param_pattern = /\[(\[)?(\.\.\.)?([\w-]+?)(?:=([\w-]+))?\]\]?/g;
+export const basic_param_pattern = /\[(\[)?(\.\.\.)?([\w-]+?)(?:=([\w-]+))?\]\]?/g;
 
 /**
  * Populate a route ID with params to resolve a pathname.

From 18307d036265dcb4eb2d7d1cf48dbd50b15c8818 Mon Sep 17 00:00:00 2001
From: Nic Polumeyv <162764842+Nic-Polumeyv@users.noreply.github.com>
Date: Wed, 29 Jul 2026 20:18:57 -0400
Subject: [PATCH 2/5] fix: don't let an omitted optional param merge into the
 next path segment

---
 packages/kit/src/core/sync/write_app_types.js | 35 +++++++++----------
 .../sync/write_types/test/app-types/+page.js  |  4 +++
 2 files changed, 21 insertions(+), 18 deletions(-)

diff --git a/packages/kit/src/core/sync/write_app_types.js b/packages/kit/src/core/sync/write_app_types.js
index 7d57a89d71cd..f8e0537f206b 100644
--- a/packages/kit/src/core/sync/write_app_types.js
+++ b/packages/kit/src/core/sync/write_app_types.js
@@ -9,26 +9,25 @@ import { basic_param_pattern, get_route_segments } from '../../utils/routing.js'
 const optional_param_pattern = /^\[\[[\w-]+(?:=[\w-]+)?\]\]$/;
 
 /**
- * Convert a route ID to a pathname (relative to the base path) in which each param
- * is replaced with `${string}`
+ * Convert a route ID to the pathnames it can match (relative to the base path), in which each
+ * param is replaced with `${string}`. A param that fills an entire segment can be absent, so it
+ * contributes a pathname with the segment and one without, rather than one that absorbs the `/`
  * @param {string} id
  */
-const get_pathname_pattern = (id) => {
-	let pathname = '';
-	let separator = '';
+const get_pathname_patterns = (id) => {
+	let pathnames = [''];
 
 	for (const segment of get_route_segments(id)) {
-		if (optional_param_pattern.test(segment)) {
-			// the segment can be absent, so `${string}` absorbs the adjacent `/`. TypeScript does not
-			// match a literal against two consecutive placeholders, so only add one
-			if (!pathname.endsWith('${string}')) pathname += '${string}';
-		} else {
-			pathname += separator + segment.replace(basic_param_pattern, '${string}');
-			separator = '/';
-		}
+		const optional = optional_param_pattern.test(segment);
+		const content = optional ? '${string}' : segment.replace(basic_param_pattern, '${string}');
+
+		pathnames = pathnames.flatMap((pathname) => {
+			const joined = pathname === '' ? content : `${pathname}/${content}`;
+			return optional ? [joined, pathname] : [joined];
+		});
 	}
 
-	return pathname;
+	return [...new Set(pathnames)];
 };
 
 /**
@@ -208,8 +207,6 @@ function generate_app_types(manifest_data, config, dir) {
 	}
 
 	for (const route of manifest_data.routes) {
-		const pathname = get_pathname_pattern(route.id);
-
 		/** @type {(path: string) => string} */
 		let serialise = s;
 
@@ -225,8 +222,10 @@ function generate_app_types(manifest_data, config, dir) {
 			serialise = (p) => `\`${p}\` & {}`;
 		}
 
-		for (const p of get_pathnames_for_trailing_slash(pathname, route)) {
-			pathnames.add(serialise(p));
+		for (const pathname of get_pathname_patterns(route.id)) {
+			for (const p of get_pathnames_for_trailing_slash(pathname, route)) {
+				pathnames.add(serialise(p));
+			}
 		}
 
 		let layout_type = 'Record<string, never>';
diff --git a/packages/kit/src/core/sync/write_types/test/app-types/+page.js b/packages/kit/src/core/sync/write_types/test/app-types/+page.js
index 12ec641ad53a..a159df1f29b5 100644
--- a/packages/kit/src/core/sync/write_types/test/app-types/+page.js
+++ b/packages/kit/src/core/sync/write_types/test/app-types/+page.js
@@ -114,6 +114,10 @@ pathname = 'en/about';
 pathname = 'deep';
 pathname = 'en/deep';
 pathname = 'en/gb/deep';
+// @ts-expect-error an omitted optional param does not merge into the next segment
+pathname = 'xyzabout';
+// @ts-expect-error
+pathname = 'xyzdeep';
 
 // Test multiple params in a single segment
 // eslint-disable-next-line @typescript-eslint/no-unused-vars

From c6b0b9fb388fde8c49c70dc56802b6857e667e61 Mon Sep 17 00:00:00 2001
From: Nic Polumeyv <162764842+Nic-Polumeyv@users.noreply.github.com>
Date: Thu, 30 Jul 2026 14:29:38 -0400
Subject: [PATCH 3/5] fix: a rest param can match zero segments, so its segment
 can be absent

---
 .changeset/app-types-path-template.md                      | 2 +-
 packages/kit/src/core/sync/write_app_types.js              | 7 ++++---
 .../kit/src/core/sync/write_types/test/app-types/+page.js  | 6 +++++-
 .../write_types/test/app-types/files/[...path]/+page.js    | 0
 4 files changed, 10 insertions(+), 5 deletions(-)
 create mode 100644 packages/kit/src/core/sync/write_types/test/app-types/files/[...path]/+page.js

diff --git a/.changeset/app-types-path-template.md b/.changeset/app-types-path-template.md
index a4d93cb620df..31e16212deed 100644
--- a/.changeset/app-types-path-template.md
+++ b/.changeset/app-types-path-template.md
@@ -2,4 +2,4 @@
 '@sveltejs/kit': patch
 ---
 
-fix: generate valid `Path` types for routes with an optional first segment or several params in one segment
+fix: generate valid `Path` types for routes with optional params, rest params, or several params in one segment
diff --git a/packages/kit/src/core/sync/write_app_types.js b/packages/kit/src/core/sync/write_app_types.js
index f8e0537f206b..1e2f6330bc84 100644
--- a/packages/kit/src/core/sync/write_app_types.js
+++ b/packages/kit/src/core/sync/write_app_types.js
@@ -7,6 +7,7 @@ import { s } from '../../utils/misc.js';
 import { basic_param_pattern, get_route_segments } from '../../utils/routing.js';
 
 const optional_param_pattern = /^\[\[[\w-]+(?:=[\w-]+)?\]\]$/;
+const rest_param_pattern = /^\[\.\.\.[\w-]+(?:=[\w-]+)?\]$/;
 
 /**
  * Convert a route ID to the pathnames it can match (relative to the base path), in which each
@@ -18,12 +19,12 @@ const get_pathname_patterns = (id) => {
 	let pathnames = [''];
 
 	for (const segment of get_route_segments(id)) {
-		const optional = optional_param_pattern.test(segment);
-		const content = optional ? '${string}' : segment.replace(basic_param_pattern, '${string}');
+		const omittable = optional_param_pattern.test(segment) || rest_param_pattern.test(segment);
+		const content = omittable ? '${string}' : segment.replace(basic_param_pattern, '${string}');
 
 		pathnames = pathnames.flatMap((pathname) => {
 			const joined = pathname === '' ? content : `${pathname}/${content}`;
-			return optional ? [joined, pathname] : [joined];
+			return omittable ? [joined, pathname] : [joined];
 		});
 	}
 
diff --git a/packages/kit/src/core/sync/write_types/test/app-types/+page.js b/packages/kit/src/core/sync/write_types/test/app-types/+page.js
index a159df1f29b5..c05860a27e2d 100644
--- a/packages/kit/src/core/sync/write_types/test/app-types/+page.js
+++ b/packages/kit/src/core/sync/write_types/test/app-types/+page.js
@@ -120,5 +120,9 @@ pathname = 'xyzabout';
 pathname = 'xyzdeep';
 
 // Test multiple params in a single segment
-// eslint-disable-next-line @typescript-eslint/no-unused-vars
 pathname = 'multi-param/1-2';
+
+// Test rest params, which can match zero segments
+pathname = 'files';
+// eslint-disable-next-line @typescript-eslint/no-unused-vars
+pathname = 'files/a/b';
diff --git a/packages/kit/src/core/sync/write_types/test/app-types/files/[...path]/+page.js b/packages/kit/src/core/sync/write_types/test/app-types/files/[...path]/+page.js
new file mode 100644
index 000000000000..e69de29bb2d1

From dac40be07b3673c9e8e5d896a2033757251fcbc1 Mon Sep 17 00:00:00 2001
From: Nic Polumeyv <162764842+Nic-Polumeyv@users.noreply.github.com>
Date: Thu, 30 Jul 2026 14:39:03 -0400
Subject: [PATCH 4/5] fix: expand escape sequences instead of leaking them into
 the pathname types

---
 .changeset/app-types-path-template.md          |  2 +-
 packages/kit/src/core/sync/write_app_types.js  | 18 ++++++++++++++----
 .../sync/write_types/test/app-types/+page.js   |  8 +++++++-
 .../test/app-types/[x+2e]well-known/+page.js   |  0
 .../test/app-types/[x+40][handle]/+page.js     |  0
 packages/kit/src/utils/routing.js              |  8 ++++----
 6 files changed, 26 insertions(+), 10 deletions(-)
 create mode 100644 packages/kit/src/core/sync/write_types/test/app-types/[x+2e]well-known/+page.js
 create mode 100644 packages/kit/src/core/sync/write_types/test/app-types/[x+40][handle]/+page.js

diff --git a/.changeset/app-types-path-template.md b/.changeset/app-types-path-template.md
index 31e16212deed..99c9c25d49cb 100644
--- a/.changeset/app-types-path-template.md
+++ b/.changeset/app-types-path-template.md
@@ -2,4 +2,4 @@
 '@sveltejs/kit': patch
 ---
 
-fix: generate valid `Path` types for routes with optional params, rest params, or several params in one segment
+fix: generate valid `Path` types for routes with optional or rest params, several params in one segment, or escape sequences
diff --git a/packages/kit/src/core/sync/write_app_types.js b/packages/kit/src/core/sync/write_app_types.js
index 1e2f6330bc84..b3f5bcd9ea93 100644
--- a/packages/kit/src/core/sync/write_app_types.js
+++ b/packages/kit/src/core/sync/write_app_types.js
@@ -4,15 +4,21 @@ import { resolve_entry } from '../../utils/filesystem.js';
 import { posixify } from '../../utils/os.js';
 import { write_if_changed } from './utils.js';
 import { s } from '../../utils/misc.js';
-import { basic_param_pattern, get_route_segments } from '../../utils/routing.js';
+import {
+	decode_escape_sequence,
+	encode_pathname_chars,
+	get_route_segments,
+	segment_pattern
+} from '../../utils/routing.js';
 
 const optional_param_pattern = /^\[\[[\w-]+(?:=[\w-]+)?\]\]$/;
 const rest_param_pattern = /^\[\.\.\.[\w-]+(?:=[\w-]+)?\]$/;
 
 /**
  * Convert a route ID to the pathnames it can match (relative to the base path), in which each
- * param is replaced with `${string}`. A param that fills an entire segment can be absent, so it
- * contributes a pathname with the segment and one without, rather than one that absorbs the `/`
+ * param is replaced with `${string}` and each escape sequence is expanded. A param that fills an
+ * entire segment can be absent, so it contributes a pathname with the segment and one without,
+ * rather than one that absorbs the `/`
  * @param {string} id
  */
 const get_pathname_patterns = (id) => {
@@ -20,7 +26,11 @@ const get_pathname_patterns = (id) => {
 
 	for (const segment of get_route_segments(id)) {
 		const omittable = optional_param_pattern.test(segment) || rest_param_pattern.test(segment);
-		const content = omittable ? '${string}' : segment.replace(basic_param_pattern, '${string}');
+		const content = omittable
+			? '${string}'
+			: segment.replace(segment_pattern, (_, escape_type, escape_code) =>
+					escape_type ? encode_pathname_chars(decode_escape_sequence(escape_code)) : '${string}'
+				);
 
 		pathnames = pathnames.flatMap((pathname) => {
 			const joined = pathname === '' ? content : `${pathname}/${content}`;
diff --git a/packages/kit/src/core/sync/write_types/test/app-types/+page.js b/packages/kit/src/core/sync/write_types/test/app-types/+page.js
index c05860a27e2d..91d0e01e964b 100644
--- a/packages/kit/src/core/sync/write_types/test/app-types/+page.js
+++ b/packages/kit/src/core/sync/write_types/test/app-types/+page.js
@@ -124,5 +124,11 @@ pathname = 'multi-param/1-2';
 
 // Test rest params, which can match zero segments
 pathname = 'files';
-// eslint-disable-next-line @typescript-eslint/no-unused-vars
 pathname = 'files/a/b';
+
+// Test escape sequences, which are expanded
+pathname = '.well-known';
+// @ts-expect-error the route id's escape sequence is not part of the pathname
+pathname = '[x+2e]well-known';
+// eslint-disable-next-line @typescript-eslint/no-unused-vars
+pathname = '@someone';
diff --git a/packages/kit/src/core/sync/write_types/test/app-types/[x+2e]well-known/+page.js b/packages/kit/src/core/sync/write_types/test/app-types/[x+2e]well-known/+page.js
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/kit/src/core/sync/write_types/test/app-types/[x+40][handle]/+page.js b/packages/kit/src/core/sync/write_types/test/app-types/[x+40][handle]/+page.js
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/packages/kit/src/utils/routing.js b/packages/kit/src/utils/routing.js
index 2c77324d537c..f5b0d6b54d80 100644
--- a/packages/kit/src/utils/routing.js
+++ b/packages/kit/src/utils/routing.js
@@ -11,7 +11,7 @@ const escape_sequence_pattern = /\[([ux])\+([^\]]+)\]/;
  * Decodes the codepoints of an `[x+nn]` or `[u+nnnn]` escape sequence
  * @param {string} code the sequence without its `[x+`/`[u+` prefix or `]` suffix
  */
-function decode_escape_sequence(code) {
+export function decode_escape_sequence(code) {
 	return String.fromCharCode(...code.split('-').map((codepoint) => parseInt(codepoint, 16)));
 }
 
@@ -20,7 +20,7 @@ function decode_escape_sequence(code) {
  * escape sequence still matches the pattern `parse_route_id` builds for it
  * @param {string} str
  */
-function encode_pathname_chars(str) {
+export function encode_pathname_chars(str) {
 	return str.replace(
 		/[%/?#]/g,
 		(char) => '%' + char.charCodeAt(0).toString(16).toUpperCase().padStart(2, '0')
@@ -276,11 +276,11 @@ function escape(str) {
 		.join('');
 }
 
-export const basic_param_pattern = /\[(\[)?(\.\.\.)?([\w-]+?)(?:=([\w-]+))?\]\]?/g;
+const basic_param_pattern = /\[(\[)?(\.\.\.)?([\w-]+?)(?:=([\w-]+))?\]\]?/g;
 
 // escape sequences are expanded in the same pass as the params, so that a param
 // value containing `[x+2f]` is not itself expanded
-const segment_pattern = new RegExp(
+export const segment_pattern = new RegExp(
 	`${escape_sequence_pattern.source}|${basic_param_pattern.source}`,
 	'g'
 );

From 15d2da79ecf3bfab3771638325213bbe5f186b61 Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Fri, 31 Jul 2026 16:42:27 -0400
Subject: [PATCH 5/5] oops, bad merge

---
 packages/kit/src/core/sync/write_app_types.js | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/packages/kit/src/core/sync/write_app_types.js b/packages/kit/src/core/sync/write_app_types.js
index 7f981794730a..7a6724bf116c 100644
--- a/packages/kit/src/core/sync/write_app_types.js
+++ b/packages/kit/src/core/sync/write_app_types.js
@@ -226,9 +226,6 @@ function generate_app_types(manifest_data, config, dir) {
 			app_route_ids.push(s(route.id));
 		}
 
-		const pathname = remove_group_segments(route.id);
-		let normalized_pathname = pathname.slice(1);
-
 		/** @type {(path: string) => string} */
 		let serialise = s;