diff --git a/src/wp-admin/includes/image-edit.php b/src/wp-admin/includes/image-edit.php
index 2f6bc25740e2d..1f3ac1a3d088a 100644
--- a/src/wp-admin/includes/image-edit.php
+++ b/src/wp-admin/includes/image-edit.php
@@ -525,6 +525,8 @@ function wp_save_image_file( $filename, $image, $mime_type, $post_id ) {
  * @param int $w Image width in pixels.
  * @param int $h Image height in pixels.
  * @return float|int Image preview ratio.
+ *
+ * @phpstan-pure
  */
 function _image_get_preview_ratio( $w, $h ) {
 	$max = max( $w, $h );
diff --git a/src/wp-admin/includes/image.php b/src/wp-admin/includes/image.php
index a05531c6d9557..d1cf2ca58d048 100644
--- a/src/wp-admin/includes/image.php
+++ b/src/wp-admin/includes/image.php
@@ -757,6 +757,8 @@ function wp_generate_attachment_metadata( $attachment_id, $file ) {
  *
  * @param string $str Fraction string.
  * @return int|float Returns calculated fraction or integer 0 on invalid input.
+ *
+ * @phpstan-pure
  */
 function wp_exif_frac2dec( $str ) {
 	if ( ! is_scalar( $str ) || is_bool( $str ) ) {
diff --git a/src/wp-admin/includes/media.php b/src/wp-admin/includes/media.php
index 42de0269a05c2..d48eb7f53431c 100644
--- a/src/wp-admin/includes/media.php
+++ b/src/wp-admin/includes/media.php
@@ -1351,6 +1351,7 @@ function image_link_input_fields( $post, $url_type = '' ) {
  * @param WP_Post $edit_post Attachment WP_Post object.
  * @return string HTML markup for the textarea element.
  *
+ * @phpstan-pure
  * @phpstan-return non-falsy-string
  */
 function wp_caption_input_textarea( $edit_post ) {
diff --git a/src/wp-admin/includes/menu.php b/src/wp-admin/includes/menu.php
index f1c2985e93e8e..1e71c782ec8ea 100644
--- a/src/wp-admin/includes/menu.php
+++ b/src/wp-admin/includes/menu.php
@@ -211,6 +211,7 @@
  *
  * @phpstan-template T of string
  * @phpstan-param T $class_to_add
+ * @phpstan-pure
  * @phpstan-return ( $classes is empty ? T : non-empty-string )
  */
 function add_cssclass( $class_to_add, $classes ) {
diff --git a/src/wp-admin/includes/misc.php b/src/wp-admin/includes/misc.php
index c1ee93a2849e5..1d3bc8700728b 100644
--- a/src/wp-admin/includes/misc.php
+++ b/src/wp-admin/includes/misc.php
@@ -363,6 +363,8 @@ function update_recently_edited( $file ) {
  *
  * @param array $allowed_files List of theme file paths.
  * @return array Tree structure for listing theme files.
+ *
+ * @phpstan-pure
  */
 function wp_make_theme_file_tree( $allowed_files ) {
 	$tree_list = array();
diff --git a/src/wp-admin/includes/upgrade.php b/src/wp-admin/includes/upgrade.php
index 461ab78a219e5..8c97eaa5212e4 100644
--- a/src/wp-admin/includes/upgrade.php
+++ b/src/wp-admin/includes/upgrade.php
@@ -3640,6 +3640,8 @@ function make_site_theme() {
  *
  * @param int $level User level.
  * @return string User role name.
+ *
+ * @phpstan-pure
  */
 function translate_level_to_role( $level ) {
 	switch ( $level ) {
diff --git a/src/wp-includes/abilities-api.php b/src/wp-includes/abilities-api.php
index abd3684273a5a..31753160f1498 100644
--- a/src/wp-includes/abilities-api.php
+++ b/src/wp-includes/abilities-api.php
@@ -592,6 +592,8 @@ function wp_get_abilities( array $args = array() ): array {
  * @param array $meta       The ability's meta array.
  * @param array $conditions The required key/value conditions to match against.
  * @return bool True if all conditions match, false otherwise.
+ *
+ * @phpstan-pure
  */
 function _wp_get_abilities_match_meta( array $meta, array $conditions ): bool {
 	foreach ( $conditions as $key => $value ) {
diff --git a/src/wp-includes/block-editor.php b/src/wp-includes/block-editor.php
index 830e67cfce013..c244a789947bd 100644
--- a/src/wp-includes/block-editor.php
+++ b/src/wp-includes/block-editor.php
@@ -397,6 +397,8 @@ function _wp_get_iframed_editor_assets() {
  * @param array  $blocks     Array of blocks.
  * @param string $block_name Name of the block to find.
  * @return array Found block, or empty array if none found.
+ *
+ * @phpstan-pure
  */
 function wp_get_first_block( $blocks, $block_name ) {
 	foreach ( $blocks as $block ) {
diff --git a/src/wp-includes/block-patterns.php b/src/wp-includes/block-patterns.php
index 3e50b349d242c..5bc5fb60c1bfd 100644
--- a/src/wp-includes/block-patterns.php
+++ b/src/wp-includes/block-patterns.php
@@ -252,6 +252,8 @@ function _register_core_block_patterns_and_categories() {
  *
  * @param array $pattern Pattern as returned from the Pattern Directory API.
  * @return array Normalized pattern.
+ *
+ * @phpstan-pure
  */
 function wp_normalize_remote_block_pattern( $pattern ) {
 	if ( isset( $pattern['block_types'] ) ) {
diff --git a/src/wp-includes/block-supports/dimensions.php b/src/wp-includes/block-supports/dimensions.php
index 584574f4153ce..bc9f1f977924b 100644
--- a/src/wp-includes/block-supports/dimensions.php
+++ b/src/wp-includes/block-supports/dimensions.php
@@ -94,6 +94,8 @@ function wp_apply_dimensions_support( $block_type, $block_attributes ) {
  *
  * @param mixed $aspect_ratio Aspect-ratio value.
  * @return bool Whether the value is an explicit aspect ratio.
+ *
+ * @phpstan-pure
  */
 function wp_is_explicit_aspect_ratio_value( $aspect_ratio ) {
 	if ( ! is_string( $aspect_ratio ) && ! is_numeric( $aspect_ratio ) ) {
diff --git a/src/wp-includes/block-supports/elements.php b/src/wp-includes/block-supports/elements.php
index e8076cc1bd3ba..cb2cd64ae2a52 100644
--- a/src/wp-includes/block-supports/elements.php
+++ b/src/wp-includes/block-supports/elements.php
@@ -29,6 +29,8 @@ function wp_get_elements_class_name(): string {
  * @param array $block   Block object.
  * @param array $options Per element type options e.g. whether to skip serialization.
  * @return bool Whether the block needs an elements class name.
+ *
+ * @phpstan-pure
  */
 function wp_should_add_elements_class_name( $block, $options ) {
 	if ( ! isset( $block['attrs']['style']['elements'] ) ) {
diff --git a/src/wp-includes/block-supports/layout.php b/src/wp-includes/block-supports/layout.php
index 0162ae8d5a047..24c5197626828 100644
--- a/src/wp-includes/block-supports/layout.php
+++ b/src/wp-includes/block-supports/layout.php
@@ -44,6 +44,8 @@ function wp_get_block_style_variation_name_from_registered_style( string $class_
  *
  * @param mixed $layout Layout object.
  * @return array Child layout values, or an empty array.
+ *
+ * @phpstan-pure
  */
 function wp_get_layout_child_values( $layout ) {
 	if ( ! is_array( $layout ) ) {
@@ -63,6 +65,8 @@ function wp_get_layout_child_values( $layout ) {
  *
  * @param mixed $layout Layout object.
  * @return array Container layout values, or an empty array.
+ *
+ * @phpstan-pure
  */
 function wp_get_layout_container_values( $layout ) {
 	if ( ! is_array( $layout ) ) {
@@ -300,6 +304,8 @@ function wp_get_child_layout_style_rules( $selector, $child_layout, $parent_layo
  * @access private
  *
  * @return array[] Layout definitions.
+ *
+ * @phpstan-pure
  */
 function wp_get_layout_definitions() {
 	$layout_definitions = array(
diff --git a/src/wp-includes/block-supports/states.php b/src/wp-includes/block-supports/states.php
index 147f770855c21..89a3a2d41d6c7 100644
--- a/src/wp-includes/block-supports/states.php
+++ b/src/wp-includes/block-supports/states.php
@@ -78,6 +78,8 @@ function wp_normalize_state_style_for_css_output( $style ) {
  *
  * @param array $declarations CSS declarations generated by the style engine.
  * @return array CSS declarations with fallback border styles applied where needed.
+ *
+ * @phpstan-pure
  */
 function wp_get_state_declarations_with_fallback_border_styles( $declarations ) {
 	if ( ! is_array( $declarations ) ) {
@@ -123,6 +125,8 @@ function wp_get_state_declarations_with_fallback_border_styles( $declarations )
  *
  * @param array $declarations CSS declarations generated by the style engine.
  * @return array CSS declarations with background resets applied where needed.
+ *
+ * @phpstan-pure
  */
 function wp_get_state_declarations_with_background_resets( $declarations ) {
 	if ( ! is_array( $declarations ) ) {
@@ -154,6 +158,8 @@ function wp_get_state_declarations_with_background_resets( $declarations ) {
  *
  * @param array $state_style State style object.
  * @return array State style object with fallback dimension styles applied where needed.
+ *
+ * @phpstan-pure
  */
 function wp_get_state_style_with_fallback_dimension_styles( $state_style ) {
 	if ( ! is_array( $state_style ) ) {
@@ -295,6 +301,8 @@ function wp_get_state_style_groups( $state_style, $block_selectors ) {
  * @param array $state_style State style object.
  * @param array $nested_keys Keys to remove from the root style object.
  * @return array Root-only style object.
+ *
+ * @phpstan-pure
  */
 function wp_get_root_state_style( $state_style, $nested_keys ) {
 	if ( ! is_array( $state_style ) ) {
diff --git a/src/wp-includes/blocks.php b/src/wp-includes/blocks.php
index 1701548d8d3fa..585d26b8a3bea 100644
--- a/src/wp-includes/blocks.php
+++ b/src/wp-includes/blocks.php
@@ -1391,6 +1391,8 @@ function apply_block_hooks_to_content_from_post_object(
  *
  * @param string $serialized_block The serialized markup of a block and its inner blocks.
  * @return string The serialized markup of the inner blocks.
+ *
+ * @phpstan-pure
  */
 function remove_serialized_parent_block( $serialized_block ) {
 	$start = strpos( $serialized_block, '-->' ) + strlen( '-->' );
@@ -1408,6 +1410,8 @@ function remove_serialized_parent_block( $serialized_block ) {
  *
  * @param string $serialized_block The serialized markup of a block and its inner blocks.
  * @return string The serialized markup of the wrapper block.
+ *
+ * @phpstan-pure
  */
 function extract_serialized_parent_block( $serialized_block ) {
 	$start = strpos( $serialized_block, '-->' ) + strlen( '-->' );
@@ -1597,6 +1601,8 @@ function insert_hooked_blocks_into_rest_response( $response, $post ) {
  *                                                       Default: 'insert_hooked_blocks'.
  * @return callable A function that returns the serialized markup for the given block,
  *                  including the markup for any hooked blocks before it.
+ *
+ * @phpstan-pure
  */
 function make_before_block_visitor( $hooked_blocks, $context, $callback = 'insert_hooked_blocks' ) {
 	/**
@@ -1654,6 +1660,8 @@ function make_before_block_visitor( $hooked_blocks, $context, $callback = 'inser
  *                                                       Default: 'insert_hooked_blocks'.
  * @return callable A function that returns the serialized markup for the given block,
  *                  including the markup for any hooked blocks after it.
+ *
+ * @phpstan-pure
  */
 function make_after_block_visitor( $hooked_blocks, $context, $callback = 'insert_hooked_blocks' ) {
 	/**
@@ -3086,6 +3094,7 @@ static function ( $format ) {
  * @param bool     $is_next Flag for handling `next/previous` blocks.
  * @return string|null The pagination arrow HTML or null if there is none.
  *
+ * @phpstan-pure
  * @phpstan-return non-falsy-string|null
  */
 function get_query_pagination_arrow( $block, $is_next ) {
@@ -3188,6 +3197,7 @@ function build_comment_query_vars_from_block( $block ) {
  *                                  Accepts 'next' or 'previous'. Default 'next'.
  * @return string|null The pagination arrow HTML or null if there is none.
  *
+ * @phpstan-pure
  * @phpstan-return non-falsy-string|null
  */
 function get_comments_pagination_arrow( $block, $pagination_type = 'next' ) {
diff --git a/src/wp-includes/category-template.php b/src/wp-includes/category-template.php
index dbb1ff8ab0d2c..214a735ac6c37 100644
--- a/src/wp-includes/category-template.php
+++ b/src/wp-includes/category-template.php
@@ -803,6 +803,8 @@ function wp_tag_cloud( $args = '' ) {
  *
  * @param int $count Number of posts with that tag.
  * @return int Scaled count.
+ *
+ * @phpstan-pure
  */
 function default_topic_count_scale( $count ) {
 	return (int) round( log10( $count + 1 ) * 100 );
diff --git a/src/wp-includes/connectors.php b/src/wp-includes/connectors.php
index 9c83a973eba43..f4210ae04d6b5 100644
--- a/src/wp-includes/connectors.php
+++ b/src/wp-includes/connectors.php
@@ -418,6 +418,8 @@ function _wp_connectors_register_default_ai_providers( WP_Connector_Registry $re
  *
  * @param string $key The API key to mask.
  * @return string The masked key, e.g. "************fj39".
+ *
+ * @phpstan-pure
  */
 function _wp_connectors_mask_api_key( string $key ): string {
 	if ( strlen( $key ) <= 4 ) {
@@ -480,6 +482,8 @@ function _wp_connectors_get_api_key_source( string $setting_name, string $env_va
  * @param string $value The raw credentials string.
  * @return array{username: string, password: string} Parsed credentials. Both values
  *                                                   are empty when the string is malformed.
+ *
+ * @phpstan-pure
  */
 function wp_connectors_parse_application_password_credentials( string $value ): array {
 	$separator = strpos( $value, ':' );
diff --git a/src/wp-includes/formatting.php b/src/wp-includes/formatting.php
index 552c5f17c21a3..978e3f5cc52f0 100644
--- a/src/wp-includes/formatting.php
+++ b/src/wp-includes/formatting.php
@@ -727,6 +727,8 @@ function _get_wptexturize_split_regex( $shortcode_regex = '' ) {
  *
  * @param string[] $tagnames Array of shortcodes to find.
  * @return string The regular expression.
+ *
+ * @phpstan-pure
  */
 function _get_wptexturize_shortcode_regex( $tagnames ) {
 	$tagregexp = implode( '|', array_map( 'preg_quote', $tagnames ) );
@@ -2834,6 +2836,7 @@ function format_to_edit( $content, $rich_text = false ) {
  * @param int $threshold  Digit places number needs to be to not have zeros added.
  * @return string Adds leading zeros to number if needed.
  *
+ * @phpstan-pure
  * @phpstan-return (
  *     $threshold is 0
  *         ? lowercase-string&non-empty-string&numeric-string
@@ -2855,6 +2858,8 @@ function zeroise( $number, $threshold ) {
  *
  * @param string $value Value to which backslashes will be added.
  * @return string String with backslashes inserted.
+ *
+ * @phpstan-pure
  */
 function backslashit( $value ) {
 	if ( isset( $value[0] ) && $value[0] >= '0' && $value[0] <= '9' ) {
@@ -2878,6 +2883,7 @@ function backslashit( $value ) {
  * @return string String with trailing slash added.
  *
  * @phpstan-return non-falsy-string
+ * @phpstan-pure
  */
 function trailingslashit( $value ) {
 	return untrailingslashit( $value ) . '/';
@@ -2893,6 +2899,8 @@ function trailingslashit( $value ) {
  *
  * @param string $value Value from which trailing slashes will be removed.
  * @return string String without the trailing slashes.
+ *
+ * @phpstan-pure
  */
 function untrailingslashit( $value ) {
 	return rtrim( $value, '/\\' );
@@ -3306,6 +3314,8 @@ function make_clickable( $text ) {
  * @param string $text   The string to split.
  * @param int    $goal   The desired chunk length.
  * @return array Numeric array of chunks.
+ *
+ * @phpstan-pure
  */
 function _split_str_by_whitespace( $text, $goal ) {
 	$chunks = array();
@@ -5839,6 +5849,8 @@ function _sanitize_text_fields( $str, $keep_newlines = false ) {
  * @param string $path   A path.
  * @param string $suffix If the filename ends in suffix this will also be cut off.
  * @return string The base name of the given path.
+ *
+ * @phpstan-pure
  */
 function wp_basename( $path, $suffix = '' ) {
 	return urldecode( basename( str_replace( array( '%2F', '%5C' ), '/', urlencode( $path ) ), $suffix ) );
@@ -5945,6 +5957,8 @@ function sanitize_trackback_urls( $to_ping ) {
  *         T is array ? array<key-of<T>, ( value-of<T> is string ? string : value-of<T> )> : T
  *     )
  * )
+ *
+ * @phpstan-pure
  */
 function wp_slash( $value ) {
 	if ( is_array( $value ) ) {
@@ -6374,6 +6388,8 @@ function wp_staticize_emoji_for_email( $mail ) {
  *
  * @param string $type Optional. Which array type to return. Accepts 'partials' or 'entities', default 'entities'.
  * @return array An array to match all emoji that WordPress recognises.
+ *
+ * @phpstan-pure
  */
 function _wp_emoji_list( $type = 'entities' ) {
 	// Do not remove the START/END comments - they're used to find where to insert the arrays.
@@ -6399,6 +6415,8 @@ function _wp_emoji_list( $type = 'entities' ) {
  * @param string $url    URL to shorten.
  * @param int    $length Optional. Maximum length of the shortened URL. Default 35 characters.
  * @return string Shortened URL.
+ *
+ * @phpstan-pure
  */
 function url_shorten( $url, $length = 35 ) {
 	$stripped  = str_replace( array( 'https://', 'http://', 'www.' ), '', $url );
diff --git a/src/wp-includes/functions.php b/src/wp-includes/functions.php
index 114a9484f5659..b9f77c49739f6 100644
--- a/src/wp-includes/functions.php
+++ b/src/wp-includes/functions.php
@@ -1313,6 +1313,7 @@ function wp_removable_query_args() {
  * @param array $input_array Array to walk while sanitizing contents.
  * @return array Sanitized $input_array.
  *
+ * @phpstan-pure
  * @phpstan-template T of array
  * @phpstan-param T $input_array
  * @phpstan-return array<key-of<T>, ( value-of<T> is string ? string : value-of<T> )>
@@ -1616,6 +1617,7 @@ function get_num_queries() {
  * @param string $yn Character string containing either 'y' (yes) or 'n' (no).
  * @return bool True if 'y', false on anything else.
  *
+ * @phpstan-pure
  * @phpstan-return ( $yn is 'y'|'Y' ? true : false )
  */
 function bool_from_yn( $yn ) {
@@ -5087,6 +5089,7 @@ function wp_parse_args( $args, $defaults = array() ): array {
  * @param mixed[]|string|int $input_list List of values.
  * @return array Array of scalar values. A string is split into a list, while an array
  *               keeps its keys, so the result is not necessarily a list.
+ * @phpstan-pure
  * @phpstan-return (
  *     $input_list is string|int ? list<string> : (
  *         $input_list is array<string> ? array<string> : array<scalar>
@@ -5118,6 +5121,7 @@ function wp_parse_list( $input_list ): array {
  * @return int[] Sanitized array of IDs. May include zero. Keys are preserved
  *               from the input and `array_unique()` may leave gaps, so the
  *               result is not necessarily a list.
+ * @phpstan-pure
  * @phpstan-return array<non-negative-int>
  */
 function wp_parse_id_list( $input_list ): array {
@@ -5165,6 +5169,7 @@ function wp_parse_slug_list( $input_list ): array {
  * @param string[]             $keys        The list of keys.
  * @return array<string, mixed> The array slice.
  *
+ * @phpstan-pure
  * @phpstan-template TKey of string
  * @phpstan-template TValue
  * @phpstan-param array<string, TValue> $input_array
@@ -5230,6 +5235,8 @@ function wp_recursive_ksort( &$input_array ) {
  * @param mixed $default_value Optional. The return value if the path does not exist within the array,
  *                             or if `$input_array` or `$path` are not arrays. Default null.
  * @return mixed The value from the path specified.
+ *
+ * @phpstan-pure
  */
 function _wp_array_get( $input_array, $path, $default_value = null ) {
 	// Confirm $path is valid.
@@ -5444,6 +5451,7 @@ function _wp_to_kebab_case( $input_string ) {
  *
  * @phpstan-assert-if-true array<int, mixed> $data
  *
+ * @phpstan-pure
  * @phpstan-return ( $data is array<int, mixed> ? true : false )
  */
 function wp_is_numeric_array( $data ): bool {
@@ -7926,6 +7934,8 @@ function reset_mbstring_encoding() {
  *
  * @param mixed $value Boolean value to validate.
  * @return bool Whether the value is validated.
+ *
+ * @phpstan-pure
  */
 function wp_validate_boolean( $value ) {
 	if ( is_bool( $value ) ) {
@@ -9279,6 +9289,8 @@ function is_wp_version_compatible( $required ) {
  *
  * @param string $required Minimum required PHP version.
  * @return bool True if required version is compatible or empty, false if not.
+ *
+ * @phpstan-pure
  */
 function is_php_version_compatible( $required ) {
 	return empty( $required ) || version_compare( PHP_VERSION, $required, '>=' );
@@ -9295,6 +9307,8 @@ function is_php_version_compatible( $required ) {
  * @param int|float $actual    The actual number.
  * @param int|float $precision Optional. The allowed variation. Default 1.
  * @return bool Whether the numbers match within the specified precision.
+ *
+ * @phpstan-pure
  */
 function wp_fuzzy_number_match( $expected, $actual, $precision = 1 ) {
 	return abs( (float) $expected - (float) $actual ) <= $precision;
@@ -9459,6 +9473,8 @@ function wp_admin_notice( $message, $args = array() ) {
  *
  * @param string $mime_type The mime type to check.
  * @return bool Whether the mime type is for a HEIC/HEIF image.
+ *
+ * @phpstan-pure
  */
 function wp_is_heic_image_mime_type( $mime_type ) {
 	$heic_mime_types = array(
diff --git a/src/wp-includes/general-template.php b/src/wp-includes/general-template.php
index 73178b9eca23b..2b0860cc44bf2 100644
--- a/src/wp-includes/general-template.php
+++ b/src/wp-includes/general-template.php
@@ -2514,6 +2514,8 @@ function wp_get_archives( $args = '' ) {
  *
  * @param int $num Number of day.
  * @return float Days since the start of the week.
+ *
+ * @phpstan-pure
  */
 function calendar_week_mod( $num ) {
 	$base = 7;
diff --git a/src/wp-includes/http.php b/src/wp-includes/http.php
index 1a189a261306b..55ba274bec015 100644
--- a/src/wp-includes/http.php
+++ b/src/wp-includes/http.php
@@ -807,6 +807,7 @@ function wp_parse_url( $url, $component = -1 ) {
  *               doesn't exist in the given URL; a string or - in the case of
  *               PHP_URL_PORT - integer when it does. See parse_url()'s return values.
  *
+ * @phpstan-pure
  * @phpstan-param false|array{
  *     scheme?: string,
  *     host?: string,
@@ -863,6 +864,7 @@ function _get_component_from_parsed_url_array( $url_parts, $component = -1 ) {
  * @param int $constant PHP_URL_* constant.
  * @return string|false The named key or false.
  *
+ * @phpstan-pure
  * @phpstan-param int<-1, 7> $constant
  * @phpstan-return 'scheme'|'host'|'port'|'user'|'pass'|'path'|'query'|'fragment'|false
  */
diff --git a/src/wp-includes/json-schema.php b/src/wp-includes/json-schema.php
index 782ad9714fe36..010fc1f89ce31 100644
--- a/src/wp-includes/json-schema.php
+++ b/src/wp-includes/json-schema.php
@@ -102,6 +102,8 @@ function wp_prepare_json_schema_for_client( array $schema, string $schema_profil
  * @param array<string, mixed> $schema           The schema array.
  * @param array<string, true>  $allowed_keywords Lookup map of allowed JSON Schema keywords.
  * @return array<string, mixed> The prepared schema.
+ *
+ * @phpstan-pure
  */
 function _wp_prepare_json_schema_for_client_with_allowed_keywords( array $schema, array $allowed_keywords ): array {
 	if ( isset( $schema['type'] ) && 'object' === $schema['type'] && isset( $schema['default'] ) ) {
diff --git a/src/wp-includes/kses.php b/src/wp-includes/kses.php
index 0a7ea7ff3087e..aea39aa70c094 100644
--- a/src/wp-includes/kses.php
+++ b/src/wp-includes/kses.php
@@ -2313,6 +2313,8 @@ function wp_kses_hook( $content, $allowed_html, $allowed_protocols ) {
  * @since 1.0.0
  *
  * @return string KSES version number.
+ *
+ * @phpstan-pure
  */
 function wp_kses_version() {
 	return '0.2.2';
@@ -3113,6 +3115,8 @@ function wp_kses_stripslashes( $content ) {
  *
  * @param array $inarray Unfiltered array.
  * @return array Fixed array with all lowercase keys.
+ *
+ * @phpstan-pure
  */
 function wp_kses_array_lc( $inarray ) {
 	$outarray = array();
@@ -3388,6 +3392,8 @@ function wp_kses_normalize_entities3( $matches ) {
  *
  * @param int $i Unicode codepoint.
  * @return bool Whether or not the codepoint is a valid Unicode codepoint.
+ *
+ * @phpstan-pure
  */
 function valid_unicode( $i ) {
 	$i = (int) $i;
diff --git a/src/wp-includes/l10n.php b/src/wp-includes/l10n.php
index e90f97fd2025a..15686b83c9041 100644
--- a/src/wp-includes/l10n.php
+++ b/src/wp-includes/l10n.php
@@ -262,6 +262,8 @@ function translate( $text, $domain = 'default' ) {
  *
  * @param string $text A pipe-delimited string.
  * @return string Either $text or everything before the last pipe.
+ *
+ * @phpstan-pure
  */
 function before_last_bar( $text ) {
 	$last_bar = strrpos( $text, '|' );
@@ -678,6 +680,7 @@ function _nx( $single, $plural, $number, $context, $domain = 'default' ) {
  *     @type string|null $domain   Text domain.
  * }
  *
+ * @phpstan-pure
  * @phpstan-param literal-string $singular
  * @phpstan-param literal-string $plural
  * @phpstan-param literal-string|null $domain
@@ -736,6 +739,7 @@ function _n_noop( $singular, $plural, $domain = null ) {
  *     @type string|null $domain   Text domain.
  * }
  *
+ * @phpstan-pure
  * @phpstan-param literal-string $singular
  * @phpstan-param literal-string $plural
  * @phpstan-param literal-string $context
diff --git a/src/wp-includes/load.php b/src/wp-includes/load.php
index 1558a44189226..3723410e73996 100644
--- a/src/wp-includes/load.php
+++ b/src/wp-includes/load.php
@@ -1469,6 +1469,7 @@ function is_multisite() {
  *
  * @param mixed $maybeint Data you wish to have converted to a non-negative integer.
  * @return int A non-negative integer.
+ * @phpstan-pure
  * @phpstan-return non-negative-int
  */
 function absint( $maybeint ): int {
diff --git a/src/wp-includes/media.php b/src/wp-includes/media.php
index 2ffa92f2edba0..757ee9356d41b 100644
--- a/src/wp-includes/media.php
+++ b/src/wp-includes/media.php
@@ -164,6 +164,8 @@ function image_constrain_size_for_editor( $width, $height, $size = 'medium', $co
  * @param int|string $width  Image width in pixels.
  * @param int|string $height Image height in pixels.
  * @return string HTML attributes for width and, or height.
+ *
+ * @phpstan-pure
  */
 function image_hwstring( $width, $height ) {
 	$out = '';
@@ -1374,6 +1376,8 @@ function _wp_get_attachment_relative_path( $file ) {
  *     @type int $0 Image width.
  *     @type int $1 Image height.
  * }
+ *
+ * @phpstan-pure
  */
 function _wp_get_image_size_from_meta( $size_name, $image_meta ) {
 	if ( 'full' === $size_name ) {
@@ -2175,6 +2179,8 @@ function wp_img_tag_add_auto_sizes( string $image ): string {
  *
  * @param string $sizes_attr The 'sizes' attribute value.
  * @return bool True if the 'auto' keyword is present, false otherwise.
+ *
+ * @phpstan-pure
  */
 function wp_sizes_attribute_includes_valid_auto( string $sizes_attr ): bool {
 	list( $first_size ) = explode( ',', $sizes_attr, 2 );
diff --git a/src/wp-includes/nav-menu.php b/src/wp-includes/nav-menu.php
index ed49892ac0eb6..920b2511956b3 100644
--- a/src/wp-includes/nav-menu.php
+++ b/src/wp-includes/nav-menu.php
@@ -1330,6 +1330,8 @@ function wp_map_nav_menu_locations( $new_nav_menu_locations, $old_nav_menu_locat
  *
  * @param array $menu_item_data The menu item data array.
  * @return array The menu item data with reset menu_item_parent.
+ *
+ * @phpstan-pure
  */
 function _wp_reset_invalid_menu_item_parent( $menu_item_data ) {
 	if ( ! is_array( $menu_item_data ) ) {
diff --git a/src/wp-includes/plugin.php b/src/wp-includes/plugin.php
index a3e9afacdb8dc..900905874008c 100644
--- a/src/wp-includes/plugin.php
+++ b/src/wp-includes/plugin.php
@@ -862,6 +862,8 @@ function wp_register_plugin_realpath( $file ) {
  *
  * @param string $file The filename of the plugin (__FILE__).
  * @return string the filesystem path of the directory that contains the plugin.
+ *
+ * @phpstan-pure
  */
 function plugin_dir_path( $file ) {
 	return trailingslashit( dirname( $file ) );
diff --git a/src/wp-includes/rest-api.php b/src/wp-includes/rest-api.php
index 36b5b23de9f00..6f0448cbfe3ff 100644
--- a/src/wp-includes/rest-api.php
+++ b/src/wp-includes/rest-api.php
@@ -927,6 +927,8 @@ function rest_send_allow_header( $response, $server, $request ) {
  * @param array $array2 An array to compare keys against.
  * @return array An associative array containing all the entries of array1 which have keys
  *               that are present in all arguments.
+ *
+ * @phpstan-pure
  */
 function _rest_array_intersect_key_recursive( $array1, $array2 ) {
 	$array1 = array_intersect_key( $array1, $array2 );
@@ -1534,6 +1536,7 @@ function rest_is_ip_address( $ip ) {
  * @param bool|string|int $value The value being evaluated.
  * @return bool Returns the proper associated boolean value.
  *
+ * @phpstan-pure
  * @phpstan-return (
  *     $value is false|''|'0'|0|'false'|'False'|'FALSE'
  *         ? false
@@ -1560,6 +1563,8 @@ function rest_sanitize_boolean( $value ) {
  *
  * @param bool|string $maybe_bool The value being evaluated.
  * @return bool True if a boolean, otherwise false.
+ *
+ * @phpstan-pure
  */
 function rest_is_boolean( $maybe_bool ) {
 	if ( is_bool( $maybe_bool ) ) {
@@ -2173,6 +2178,8 @@ function rest_validate_enum( $value, $args, $param ) {
  * @since 5.6.0
  *
  * @return string[] All valid JSON schema properties.
+ *
+ * @phpstan-pure
  */
 function rest_get_allowed_schema_keywords() {
 	return array(
@@ -3196,6 +3203,8 @@ function rest_filter_response_by_context( $response_data, $schema, $context ) {
  *
  * @param array $schema The schema to modify.
  * @return array The modified schema.
+ *
+ * @phpstan-pure
  */
 function rest_default_additional_properties_to_false( $schema ) {
 	$type = (array) $schema['type'];
diff --git a/src/wp-includes/script-loader.php b/src/wp-includes/script-loader.php
index 2d839af4a1a82..c4287237441b0 100644
--- a/src/wp-includes/script-loader.php
+++ b/src/wp-includes/script-loader.php
@@ -4655,6 +4655,8 @@ public function replace( string $text ): void {
  *
  * @param string $html_attribute_name Raw attribute name as found in the source HTML.
  * @return string|null Transformed `dataset` name, if interpretable as a custom data attribute, else `null`.
+ *
+ * @phpstan-pure
  */
 function wp_js_dataset_name( string $html_attribute_name ): ?string {
 	if ( 0 !== substr_compare( $html_attribute_name, 'data-', 0, 5, true ) ) {
@@ -4734,6 +4736,8 @@ function wp_js_dataset_name( string $html_attribute_name ): ?string {
  * @param string $js_dataset_name Name of JS `dataset` property to transform.
  * @return string|null Corresponding name of an HTML custom data attribute for the given dataset name,
  *                     if possible to represent in HTML, otherwise `null`.
+ *
+ * @phpstan-pure
  */
 function wp_html_custom_data_attribute_name( string $js_dataset_name ): ?string {
 	$end = strlen( $js_dataset_name );
diff --git a/src/wp-includes/shortcodes.php b/src/wp-includes/shortcodes.php
index bd5f74a1ec17b..2853fe8a6ea14 100644
--- a/src/wp-includes/shortcodes.php
+++ b/src/wp-includes/shortcodes.php
@@ -576,6 +576,8 @@ function do_shortcodes_in_html_tags( $content, $ignore_html, $tagnames ) {
  *
  * @param string $content Content to search for placeholders.
  * @return string Content with placeholders removed.
+ *
+ * @phpstan-pure
  */
 function unescape_invalid_shortcodes( $content ) {
 	// Clean up entire string, avoids re-parsing HTML.
@@ -597,6 +599,7 @@ function unescape_invalid_shortcodes( $content ) {
  * @return string The shortcode attribute regular expression.
  *
  * @phpstan-return non-falsy-string
+ * @phpstan-pure
  */
 function get_shortcode_atts_regex() {
 	return '/([\w-]+)\s*=\s*"([^"]*)"(?:\s|$)|([\w-]+)\s*=\s*\'([^\']*)\'(?:\s|$)|([\w-]+)\s*=\s*([^\s\'"]+)(?:\s|$)|"([^"]*)"(?:\s|$)|\'([^\']*)\'(?:\s|$)|(\S+)(?:\s|$)/';
diff --git a/src/wp-includes/user.php b/src/wp-includes/user.php
index 1d0523cfc9a9a..0f2aae3639014 100644
--- a/src/wp-includes/user.php
+++ b/src/wp-includes/user.php
@@ -4043,6 +4043,8 @@ function new_user_email_admin_notice() {
  * @access private
  *
  * @return string[] List of core privacy action types.
+ *
+ * @phpstan-pure
  */
 function _wp_privacy_action_request_types() {
 	return array(
diff --git a/src/wp-includes/view-config.php b/src/wp-includes/view-config.php
index 8765a5d095008..9c9ed6157bd22 100644
--- a/src/wp-includes/view-config.php
+++ b/src/wp-includes/view-config.php
@@ -26,6 +26,8 @@
  * @param string $kind The entity kind (e.g. `postType`).
  * @param string $name The entity name (e.g. `page`).
  * @return string The filter name.
+ *
+ * @phpstan-pure
  */
 function wp_get_entity_view_config_hook_name( $kind, $name ) {
 	return strtolower( "get_entity_view_config_{$kind}_{$name}" );