diff --git a/rector.php b/rector.php
index 14a079e0ab04..8fd3ab275345 100644
--- a/rector.php
+++ b/rector.php
@@ -53,6 +53,7 @@
 use Rector\TypeDeclaration\Rector\ClassMethod\AddMethodCallBasedStrictParamTypeRector;
 use Rector\TypeDeclaration\Rector\ClassMethod\ReturnNeverTypeRector;
 use Rector\TypeDeclaration\Rector\Closure\AddClosureVoidReturnTypeWhereNoReturnRector;
+use Rector\TypeDeclaration\Rector\Closure\ClosureReturnTypeRector;
 use Rector\TypeDeclaration\Rector\Empty_\EmptyOnNullableObjectToInstanceOfRector;
 use Rector\TypeDeclaration\Rector\Function_\AddFunctionVoidReturnTypeWhereNoReturnRector;
 use Rector\TypeDeclaration\Rector\Property\TypedPropertyFromAssignsRector;
@@ -217,6 +218,7 @@
         AddFunctionVoidReturnTypeWhereNoReturnRector::class,
         AddMethodCallBasedStrictParamTypeRector::class,
         TypedPropertyFromAssignsRector::class,
+        ClosureReturnTypeRector::class,
     ])
     ->withConfiguredRule(StringClassNameToClassConstantRector::class, [
         // keep '\\' prefix string on string '\Foo\Bar'
diff --git a/system/Database/OCI8/Builder.php b/system/Database/OCI8/Builder.php
index 4423a5243a81..24a6bb53b07c 100644
--- a/system/Database/OCI8/Builder.php
+++ b/system/Database/OCI8/Builder.php
@@ -109,12 +109,12 @@ protected function _replace(string $table, array $keys, array $values): string
     {
         $fieldNames = array_map(static fn ($columnName) => trim($columnName, '"'), $keys);
 
-        $uniqueIndexes = array_filter($this->db->getIndexData($table), static function ($index) use ($fieldNames) {
+        $uniqueIndexes = array_filter($this->db->getIndexData($table), static function ($index) use ($fieldNames): bool {
             $hasAllFields = count(array_intersect($index->fields, $fieldNames)) === count($index->fields);
 
             return ($index->type === 'PRIMARY') && $hasAllFields;
         });
-        $replaceableFields = array_filter($keys, static function ($columnName) use ($uniqueIndexes) {
+        $replaceableFields = array_filter($keys, static function ($columnName) use ($uniqueIndexes): bool {
             foreach ($uniqueIndexes as $index) {
                 if (in_array(trim($columnName, '"'), $index->fields, true)) {
                     return false;
@@ -344,7 +344,7 @@ protected function _upsertBatch(string $table, array $keys, array $values): stri
             if (empty($constraints)) {
                 $fieldNames = array_map(static fn ($columnName) => trim($columnName, '"'), $keys);
 
-                $uniqueIndexes = array_filter($this->db->getIndexData($table), static function ($index) use ($fieldNames) {
+                $uniqueIndexes = array_filter($this->db->getIndexData($table), static function ($index) use ($fieldNames): bool {
                     $hasAllFields = count(array_intersect($index->fields, $fieldNames)) === count($index->fields);
 
                     return ($index->type === 'PRIMARY' || $index->type === 'UNIQUE') && $hasAllFields;
diff --git a/system/Database/OCI8/PreparedQuery.php b/system/Database/OCI8/PreparedQuery.php
index a6b6c73c0348..0d20619413d7 100644
--- a/system/Database/OCI8/PreparedQuery.php
+++ b/system/Database/OCI8/PreparedQuery.php
@@ -113,7 +113,7 @@ public function parameterize(string $sql): string
         // Track our current value
         $count = 0;
 
-        return preg_replace_callback('/\?/', static function ($matches) use (&$count) {
+        return preg_replace_callback('/\?/', static function ($matches) use (&$count): string {
             return ':' . ($count++);
         }, $sql);
     }
diff --git a/system/Database/Postgre/Builder.php b/system/Database/Postgre/Builder.php
index 90b53b04e9da..196535729efe 100644
--- a/system/Database/Postgre/Builder.php
+++ b/system/Database/Postgre/Builder.php
@@ -368,7 +368,7 @@ protected function _updateBatch(string $table, array $keys, array $values): stri
             $sql .= 'WHERE ' . implode(
                 ' AND ',
                 array_map(
-                    static function ($key, $value) use ($table, $alias, $that) {
+                    static function ($key, $value) use ($table, $alias, $that): string|RawSql {
                         if ($value instanceof RawSql && is_string($key)) {
                             return $table . '.' . $key . ' = ' . $value;
                         }
@@ -463,7 +463,7 @@ protected function _upsertBatch(string $table, array $keys, array $values): stri
             $constraints = $this->QBOptions['constraints'] ?? [];
 
             if (empty($constraints)) {
-                $allIndexes = array_filter($this->db->getIndexData($table), static function ($index) use ($fieldNames) {
+                $allIndexes = array_filter($this->db->getIndexData($table), static function ($index) use ($fieldNames): bool {
                     $hasAllFields = count(array_intersect($index->fields, $fieldNames)) === count($index->fields);
 
                     return ($index->type === 'UNIQUE' || $index->type === 'PRIMARY') && $hasAllFields;
@@ -575,7 +575,7 @@ protected function _deleteBatch(string $table, array $keys, array $values): stri
             $sql .= 'WHERE ' . implode(
                 ' AND ',
                 array_map(
-                    static function ($key, $value) use ($table, $alias, $that) {
+                    static function ($key, $value) use ($table, $alias, $that): RawSql|string {
                         if ($value instanceof RawSql) {
                             return $value;
                         }
diff --git a/system/Database/Postgre/PreparedQuery.php b/system/Database/Postgre/PreparedQuery.php
index 6425297d2e97..cabca91bb662 100644
--- a/system/Database/Postgre/PreparedQuery.php
+++ b/system/Database/Postgre/PreparedQuery.php
@@ -119,7 +119,7 @@ public function parameterize(string $sql): string
         // Track our current value
         $count = 0;
 
-        return preg_replace_callback('/\?/', static function () use (&$count) {
+        return preg_replace_callback('/\?/', static function () use (&$count): string {
             $count++;
 
             return "\${$count}";
diff --git a/system/Database/SQLSRV/Builder.php b/system/Database/SQLSRV/Builder.php
index a6d0b8e85ccd..fcc0b170084f 100644
--- a/system/Database/SQLSRV/Builder.php
+++ b/system/Database/SQLSRV/Builder.php
@@ -699,7 +699,7 @@ protected function _upsertBatch(string $table, array $keys, array $values): stri
             if (empty($constraints)) {
                 $tableIndexes = $this->db->getIndexData($table);
 
-                $uniqueIndexes = array_filter($tableIndexes, static function ($index) use ($fieldNames) {
+                $uniqueIndexes = array_filter($tableIndexes, static function ($index) use ($fieldNames): bool {
                     $hasAllFields = count(array_intersect($index->fields, $fieldNames)) === count($index->fields);
 
                     return $index->type === 'PRIMARY' && $hasAllFields;
@@ -707,7 +707,7 @@ protected function _upsertBatch(string $table, array $keys, array $values): stri
 
                 // if no primary found then look for unique - since indexes have no order
                 if ($uniqueIndexes === []) {
-                    $uniqueIndexes = array_filter($tableIndexes, static function ($index) use ($fieldNames) {
+                    $uniqueIndexes = array_filter($tableIndexes, static function ($index) use ($fieldNames): bool {
                         $hasAllFields = count(array_intersect($index->fields, $fieldNames)) === count($index->fields);
 
                         return $index->type === 'UNIQUE' && $hasAllFields;
diff --git a/system/Database/SQLite3/Builder.php b/system/Database/SQLite3/Builder.php
index 87bc4d73a885..8a5d43b6751a 100644
--- a/system/Database/SQLite3/Builder.php
+++ b/system/Database/SQLite3/Builder.php
@@ -145,7 +145,7 @@ protected function _upsertBatch(string $table, array $keys, array $values): stri
             if (empty($constraints)) {
                 $fieldNames = array_map(static fn ($columnName) => trim($columnName, '`'), $keys);
 
-                $allIndexes = array_filter($this->db->getIndexData($table), static function ($index) use ($fieldNames) {
+                $allIndexes = array_filter($this->db->getIndexData($table), static function ($index) use ($fieldNames): bool {
                     $hasAllFields = count(array_intersect($index->fields, $fieldNames)) === count($index->fields);
 
                     return ($index->type === 'PRIMARY' || $index->type === 'UNIQUE') && $hasAllFields;
diff --git a/system/Debug/Toolbar/Collectors/Database.php b/system/Debug/Toolbar/Collectors/Database.php
index ee9f829b05b8..1a923a35516b 100644
--- a/system/Debug/Toolbar/Collectors/Database.php
+++ b/system/Debug/Toolbar/Collectors/Database.php
@@ -148,7 +148,7 @@ protected function formatTimelineData(): array
     public function display(): array
     {
         $data            = [];
-        $data['queries'] = array_map(static function (array $query) {
+        $data['queries'] = array_map(static function (array $query): array {
             $isDuplicate = $query['duplicate'] === true;
 
             $firstNonSystemLine = '';
diff --git a/system/Events/Events.php b/system/Events/Events.php
index a06bd7903e69..ad8efed62f9e 100644
--- a/system/Events/Events.php
+++ b/system/Events/Events.php
@@ -84,7 +84,7 @@ public static function initialize()
             $files = service('locator')->search('Config/Events.php');
         }
 
-        $files = array_filter(array_map(static function (string $file) {
+        $files = array_filter(array_map(static function (string $file): false|string {
             if (is_file($file)) {
                 return realpath($file) ?: $file;
             }
diff --git a/system/HTTP/ContentSecurityPolicy.php b/system/HTTP/ContentSecurityPolicy.php
index 7582bc467733..d0dda0ad5752 100644
--- a/system/HTTP/ContentSecurityPolicy.php
+++ b/system/HTTP/ContentSecurityPolicy.php
@@ -713,7 +713,7 @@ protected function generateNonces(ResponseInterface $response)
         $pattern = '/(' . preg_quote($this->styleNonceTag, '/')
             . '|' . preg_quote($this->scriptNonceTag, '/') . ')/';
 
-        $body = preg_replace_callback($pattern, function ($match) {
+        $body = preg_replace_callback($pattern, function ($match): string {
             $nonce = $match[0] === $this->styleNonceTag ? $this->getStyleNonce() : $this->getScriptNonce();
 
             return "nonce=\"{$nonce}\"";
diff --git a/system/HTTP/Negotiate.php b/system/HTTP/Negotiate.php
index 67a03a38014d..4f218347738d 100644
--- a/system/HTTP/Negotiate.php
+++ b/system/HTTP/Negotiate.php
@@ -233,7 +233,7 @@ public function parseHeader(string $header): array
         }
 
         // Sort to get the highest results first
-        usort($results, static function ($a, $b) {
+        usort($results, static function ($a, $b): int {
             if ($a['q'] === $b['q']) {
                 $aAst = substr_count($a['value'], '*');
                 $bAst = substr_count($b['value'], '*');
diff --git a/system/Helpers/Array/ArrayHelper.php b/system/Helpers/Array/ArrayHelper.php
index b9c356d381c1..f3eff03ba7a2 100644
--- a/system/Helpers/Array/ArrayHelper.php
+++ b/system/Helpers/Array/ArrayHelper.php
@@ -307,7 +307,7 @@ public static function recursiveCount(array $array, int $counter = 0): int
      */
     public static function sortValuesByNatural(array &$array, $sortByIndex = null): bool
     {
-        return usort($array, static function ($currentValue, $nextValue) use ($sortByIndex) {
+        return usort($array, static function ($currentValue, $nextValue) use ($sortByIndex): int {
             if ($sortByIndex !== null) {
                 return strnatcmp((string) $currentValue[$sortByIndex], (string) $nextValue[$sortByIndex]);
             }
diff --git a/system/Helpers/url_helper.php b/system/Helpers/url_helper.php
index d68fea2aad7d..fcfce09f5697 100644
--- a/system/Helpers/url_helper.php
+++ b/system/Helpers/url_helper.php
@@ -351,7 +351,15 @@ function safe_mailto(string $email, string $title = '', $attributes = ''): strin
     function auto_link(string $str, string $type = 'both', bool $popup = false): string
     {
         // Find and replace any URLs.
-        if ($type !== 'email' && preg_match_all('#(\w*://|www\.)[a-z0-9]+(-+[a-z0-9]+)*(\.[a-z0-9]+(-+[a-z0-9]+)*)+(/([^\s()<>;]+\w)?/?)?#i', $str, $matches, PREG_OFFSET_CAPTURE | PREG_SET_ORDER)) {
+        if (
+            $type !== 'email'
+            && preg_match_all(
+                '#([a-z][a-z0-9+\-.]*://|www\.)[a-z0-9]+(-+[a-z0-9]+)*(\.[a-z0-9]+(-+[a-z0-9]+)*)+(/([^\s()<>;]+\w)?/?)?#i',
+                $str,
+                $matches,
+                PREG_OFFSET_CAPTURE | PREG_SET_ORDER
+            )
+        ) {
             // Set our target HTML if using popup links.
             $target = ($popup) ? ' target="_blank"' : '';
 
@@ -370,7 +378,15 @@ function auto_link(string $str, string $type = 'both', bool $popup = false): str
         }
 
         // Find and replace any emails.
-        if ($type !== 'url' && preg_match_all('#([\w\.\-\+]+@[a-z0-9\-]+\.[a-z0-9\-\.]+[^[:punct:]\s])#i', $str, $matches, PREG_OFFSET_CAPTURE)) {
+        if (
+            $type !== 'url'
+            && preg_match_all(
+                '#([\w\.\-\+]+@[a-z0-9\-]+\.[a-z0-9\-\.]+[^[:punct:]\s])#i',
+                $str,
+                $matches,
+                PREG_OFFSET_CAPTURE
+            )
+        ) {
             foreach (array_reverse($matches[0]) as $match) {
                 if (filter_var($match[0], FILTER_VALIDATE_EMAIL) !== false) {
                     $str = substr_replace($str, safe_mailto($match[0]), $match[1], strlen($match[0]));
diff --git a/system/Router/Router.php b/system/Router/Router.php
index e20f4fff55bb..247f0de6b6b8 100644
--- a/system/Router/Router.php
+++ b/system/Router/Router.php
@@ -434,7 +434,7 @@ protected function checkRoutes(string $uri): bool
                 // Is this route supposed to redirect to another?
                 if ($this->collection->isRedirect($routeKey)) {
                     // replacing matched route groups with references: post/([0-9]+) -> post/$1
-                    $redirectTo = preg_replace_callback('/(\([^\(]+\))/', static function () {
+                    $redirectTo = preg_replace_callback('/(\([^\(]+\))/', static function (): string {
                         static $i = 1;
 
                         return '$' . $i++;
diff --git a/system/View/Parser.php b/system/View/Parser.php
index bbeb00f757c0..6600b0178369 100644
--- a/system/View/Parser.php
+++ b/system/View/Parser.php
@@ -534,7 +534,7 @@ protected function replaceSingle($pattern, $content, $template, bool $escape = f
         $content = (string) $content;
 
         // Replace the content in the template
-        return preg_replace_callback($pattern, function ($matches) use ($content, $escape) {
+        return preg_replace_callback($pattern, function ($matches) use ($content, $escape): string {
             // Check for {! !} syntax to not escape this one.
             if (
                 str_starts_with($matches[0], $this->leftDelimiter . '!')
diff --git a/tests/system/Commands/Utilities/NamespacesTest.php b/tests/system/Commands/Utilities/NamespacesTest.php
index c32d9280aef4..ffdfa0ddcf8d 100644
--- a/tests/system/Commands/Utilities/NamespacesTest.php
+++ b/tests/system/Commands/Utilities/NamespacesTest.php
@@ -42,7 +42,7 @@ protected function tearDown(): void
      */
     protected function getBuffer()
     {
-        return preg_replace_callback('/(\|\s*[^|]+\s*\|\s*)(.*?)(\s*\|\s*[^|]+\s*\|)/', static function (array $matches) {
+        return preg_replace_callback('/(\|\s*[^|]+\s*\|\s*)(.*?)(\s*\|\s*[^|]+\s*\|)/', static function (array $matches): string {
             $matches[2] = str_replace(DIRECTORY_SEPARATOR, '/', $matches[2]);
 
             return $matches[1] . $matches[2] . $matches[3];
diff --git a/tests/system/DataConverter/DataConverterTest.php b/tests/system/DataConverter/DataConverterTest.php
index 3383bbfdc102..36bae4e89ddc 100644
--- a/tests/system/DataConverter/DataConverterTest.php
+++ b/tests/system/DataConverter/DataConverterTest.php
@@ -606,7 +606,7 @@ public function testReconstructObjectWithClosure(): void
             'created_at' => 'datetime',
             'updated_at' => 'datetime',
         ];
-        $reconstructor = static function ($array) {
+        $reconstructor = static function ($array): User {
             $user = new User();
             $user->fill($array);
 
@@ -703,7 +703,7 @@ public function testExtractWithClosure(): void
             'created_at' => 'datetime',
             'updated_at' => 'datetime',
         ];
-        $extractor = static function ($obj) {
+        $extractor = static function ($obj): array {
             $array['id']         = $obj->id;
             $array['name']       = $obj->name;
             $array['created_at'] = $obj->created_at;
diff --git a/tests/system/Debug/TimerTest.php b/tests/system/Debug/TimerTest.php
index d76e35583305..643096c482cb 100644
--- a/tests/system/Debug/TimerTest.php
+++ b/tests/system/Debug/TimerTest.php
@@ -144,7 +144,7 @@ public function testRecordFunctionNoReturn(): void
     public function testRecordFunctionWithReturn(): void
     {
         $timer       = new Timer();
-        $returnValue = $timer->record('longjohn', static function () {
+        $returnValue = $timer->record('longjohn', static function (): string {
             usleep(100000);
 
             return 'test';
diff --git a/tests/system/Events/EventsTest.php b/tests/system/Events/EventsTest.php
index e761c7dff958..db975aaa1825 100644
--- a/tests/system/Events/EventsTest.php
+++ b/tests/system/Events/EventsTest.php
@@ -121,7 +121,7 @@ public function testCancelEvent(): void
 
         // This should cancel the flow of events, and leave
         // $result = 1.
-        Events::on('foo', static function ($arg) use (&$result) {
+        Events::on('foo', static function ($arg) use (&$result): bool {
             $result = 1;
 
             return false;
@@ -138,14 +138,14 @@ public function testPriority(): void
     {
         $result = 0;
 
-        Events::on('foo', static function () use (&$result) {
+        Events::on('foo', static function () use (&$result): bool {
             $result = 1;
 
             return false;
         }, EVENT_PRIORITY_NORMAL);
         // Since this has a higher priority, it will
         // run first.
-        Events::on('foo', static function () use (&$result) {
+        Events::on('foo', static function () use (&$result): bool {
             $result = 2;
 
             return false;
diff --git a/tests/system/Helpers/URLHelper/MiscUrlTest.php b/tests/system/Helpers/URLHelper/MiscUrlTest.php
index 7b3b6483069d..560729f55c95 100644
--- a/tests/system/Helpers/URLHelper/MiscUrlTest.php
+++ b/tests/system/Helpers/URLHelper/MiscUrlTest.php
@@ -523,7 +523,7 @@ public static function provideAutoLinkUrl(): iterable
             ],
             'test06' => [
                 'This one: ://codeigniter.com must not break this one: http://codeigniter.com',
-                'This one: <a href="://codeigniter.com">://codeigniter.com</a> must not break this one: <a href="http://codeigniter.com">http://codeigniter.com</a>',
+                'This one: ://codeigniter.com must not break this one: <a href="http://codeigniter.com">http://codeigniter.com</a>',
             ],
             'test07' => [
                 'Visit example.com or email foo@bar.com',
@@ -623,7 +623,7 @@ public static function provideAutolinkBoth(): iterable
             ],
             'test06' => [
                 'This one: ://codeigniter.com must not break this one: http://codeigniter.com',
-                'This one: <a href="://codeigniter.com">://codeigniter.com</a> must not break this one: <a href="http://codeigniter.com">http://codeigniter.com</a>',
+                'This one: ://codeigniter.com must not break this one: <a href="http://codeigniter.com">http://codeigniter.com</a>',
             ],
             'test07' => [
                 'Visit example.com or email foo@bar.com',
@@ -675,7 +675,7 @@ public static function provideAutoLinkPopup(): iterable
             ],
             'test06' => [
                 'This one: ://codeigniter.com must not break this one: http://codeigniter.com',
-                'This one: <a href="://codeigniter.com" target="_blank">://codeigniter.com</a> must not break this one: <a href="http://codeigniter.com" target="_blank">http://codeigniter.com</a>',
+                'This one: ://codeigniter.com must not break this one: <a href="http://codeigniter.com" target="_blank">http://codeigniter.com</a>',
             ],
             'test07' => [
                 'Visit example.com or email foo@bar.com',
diff --git a/tests/system/Test/FeatureTestTraitTest.php b/tests/system/Test/FeatureTestTraitTest.php
index b3ee3eadb4cc..a544620d1acd 100644
--- a/tests/system/Test/FeatureTestTraitTest.php
+++ b/tests/system/Test/FeatureTestTraitTest.php
@@ -153,7 +153,7 @@ public function testCallValidationTwice(): void
             [
                 'POST',
                 'section/create',
-                static function () {
+                static function (): string {
                     $validation = Services::validation();
                     $validation->setRule('title', 'title', 'required|min_length[3]');
 
diff --git a/tests/system/Validation/ValidationTest.php b/tests/system/Validation/ValidationTest.php
index 4e16fc2a713f..63db994d6cd1 100644
--- a/tests/system/Validation/ValidationTest.php
+++ b/tests/system/Validation/ValidationTest.php
@@ -311,7 +311,7 @@ public function testClosureRuleWithParamError(): void
         $this->validation->setRules([
             'foo' => [
                 'required',
-                static function ($value, $data, &$error, $field) {
+                static function ($value, $data, &$error, $field): bool {
                     if ($value !== 'abc') {
                         $error = 'The ' . $field . ' value is not "abc"';
 
diff --git a/tests/system/View/ParserTest.php b/tests/system/View/ParserTest.php
index 0cce9f722ebf..9a9f1fd8d0ac 100644
--- a/tests/system/View/ParserTest.php
+++ b/tests/system/View/ParserTest.php
@@ -806,7 +806,7 @@ public function testParserPluginClosure(): void
 
     public function testParserPluginParams(): void
     {
-        $this->parser->addPlugin('growth', static function ($str, array $params) {
+        $this->parser->addPlugin('growth', static function ($str, array $params): string {
             $step  = $params['step'] ?? 1;
             $count = $params['count'] ?? 2;
 
@@ -853,7 +853,7 @@ public function testParserSingleTagWithSingleParams(): void
 
     public function testParserSingleTagWithQuotedParams(): void
     {
-        $this->parser->addPlugin('count', static function (array $params = []) {
+        $this->parser->addPlugin('count', static function (array $params = []): string {
             $out = '';
 
             foreach ($params as $index => $param) {
@@ -870,7 +870,7 @@ public function testParserSingleTagWithQuotedParams(): void
 
     public function testParserSingleTagWithNamedParams(): void
     {
-        $this->parser->addPlugin('read_params', static function (array $params = []) {
+        $this->parser->addPlugin('read_params', static function (array $params = []): string {
             $out = '';
 
             foreach ($params as $index => $param) {
diff --git a/user_guide_src/source/general/ajax.rst b/user_guide_src/source/general/ajax.rst
index 967e2c280c59..ddc276fdf39a 100644
--- a/user_guide_src/source/general/ajax.rst
+++ b/user_guide_src/source/general/ajax.rst
@@ -56,7 +56,7 @@ React
 htmx
 ====
 
-You can use `ajax-header <https://htmx.org/extensions/ajax-header/>`_ extension.
+You can use `ajax-header <https://github.com/bigskysoftware/htmx-extensions/blob/main/src/ajax-header/README.md>`_ extension.
 
 .. code-block:: html