diff --git a/.github/copilot-instructions.md b/.github/copilot-instructions.md
index 73bc3ab31..0f089bceb 100644
--- a/.github/copilot-instructions.md
+++ b/.github/copilot-instructions.md
@@ -38,6 +38,7 @@ Use `.github/prompts/*.prompt.md` for guided workflows:
 - Avoid risky renames or moves of core stack paths used by downstream merges
 - Keep changes minimal and merge-friendly for downstream projects
 - Flag security or mergeability risks explicitly in reviews
+- Every new or modified function must have a JSDoc header: one-line description, `@param` for each argument, `@returns` for any non-void return value (always include `@returns` for async functions to document the resolved value)
 
 ## Architecture and modularity
 
diff --git a/CLAUDE.md b/CLAUDE.md
index e42a27b0a..e369a58cd 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -51,6 +51,7 @@ The `.claude/` folder contains embedded settings, skills, and agents that are av
 - Avoid risky renames or moves of core stack paths used by downstream merges
 - Keep changes minimal and merge-friendly for downstream projects
 - Flag security or mergeability risks explicitly in reviews
+- Every new or modified function must have a JSDoc header: one-line description, `@param` for each argument, `@returns` for any non-void return value (always include `@returns` for async functions to document the resolved value)
 
 ## Available embedded skills
 
diff --git a/ERRORS.md b/ERRORS.md
index feb2e64e1..076086975 100644
--- a/ERRORS.md
+++ b/ERRORS.md
@@ -12,3 +12,5 @@ Use this file as a compact memory of recurring AI mistakes.
 ## Entries
 
 - [2026-02-19] Vuetify 3 typography: computed/CSS media-query responsive headings -> use Vuetify responsive classes (example: `text-h5 text-sm-h4`)
+- [2026-02-22] functions: new or modified functions without JSDoc header -> always add JSDoc (description + `@param` for each arg + `@returns` for non-void return values and all async functions)
+- [2026-02-22] tests: never patch code to pass a test -> if a test is wrong, fix the test; if logic needs refactoring, refactor it
diff --git a/src/lib/helpers/tests/theme.spec.js b/src/lib/helpers/tests/theme.spec.js
index eb9b5ddc1..4e6da12e6 100644
--- a/src/lib/helpers/tests/theme.spec.js
+++ b/src/lib/helpers/tests/theme.spec.js
@@ -8,20 +8,18 @@ describe('Theme Helpers', () => {
       delete window.matchMedia;
     });
 
-    it('should return true when theme is explicitly true', () => {
-      expect(isDark(true)).toBe(true);
+    it('should return true when theme is dark', () => {
+      expect(isDark('dark')).toBe(true);
     });
 
-    it('should return false when theme is explicitly false', () => {
-      expect(isDark(false)).toBe(false);
+    it('should return false when theme is light', () => {
+      expect(isDark('light')).toBe(false);
     });
 
-    it('should return false when theme is undefined', () => {
+    it('should return false for unknown or missing theme (light by default)', () => {
       expect(isDark(undefined)).toBe(false);
-    });
-
-    it('should return false when theme is null', () => {
       expect(isDark(null)).toBe(false);
+      expect(isDark('')).toBe(false);
     });
 
     it('should detect auto dark mode from system preferences (dark)', () => {
diff --git a/src/lib/helpers/theme.js b/src/lib/helpers/theme.js
index 4031a0ac9..4489477b1 100644
--- a/src/lib/helpers/theme.js
+++ b/src/lib/helpers/theme.js
@@ -1,19 +1,20 @@
 /**
  * @desc Function to return actual theme
- * @param {String} option in config
- * @return {Boolean} dark value
+ * @param {String} theme - Theme option from config ('dark', 'light', or 'auto')
+ * @returns {Boolean} true if dark mode is active, false otherwise
  */
 export const isDark = (theme) => {
   if (theme === 'auto') {
     return !!(window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches);
   }
-  return !!theme;
+  return theme === 'dark';
 };
 
 /**
  * @desc Function to return custom css object
- * @param {String} String, section, card, video
- * @return {Object} object in config { background: ... }
+ * @param {String} kind - Style section key (e.g. 'section', 'card', 'video')
+ * @param {Object} object - Config object containing the style definitions
+ * @returns {Object} object in config { background: ... }
  */
 export const style = (kind, object) => {
   const style = {};
@@ -41,7 +42,7 @@ export const style = (kind, object) => {
 /**
  * @desc Helper to convert hex color to RGB string
  * @param {String} hex - Hex color (e.g. #RRGGBB)
- * @return {String} RGB string (e.g. "255,255,255")
+ * @returns {String} RGB string (e.g. "255,255,255")
  */
 const hexToRgb = (hex) => {
   const result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);
@@ -53,7 +54,7 @@ const hexToRgb = (hex) => {
  * @param {String} hex - Hex color (e.g. #RRGGBB)
  * @param {Number} amount - Amount to adjust (-1 to 1, or 0-100 for legacy percent mode)
  * @param {String} output - 'rgb' for RGB string, 'hex' for hex string. Default: 'rgb'
- * @return {String} RGB string (e.g. "255,255,255") or hex string (e.g. "#ffffff")
+ * @returns {String} RGB string (e.g. "255,255,255") or hex string (e.g. "#ffffff")
  */
 const adjustColor = (hex, amount, output = 'rgb') => {
   const result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);
@@ -97,7 +98,7 @@ const adjustColor = (hex, amount, output = 'rgb') => {
  * @param {String} options.border - 'all', 'bottom', 'top', or 'none'. Default: 'all'
  * @param {Boolean|String} options.glowBorder - false, true (static gradient), or 'animated' (rotating). Default: false
  * @param {Object} options.extras - Additional CSS properties to merge
- * @return {Object} CSS style object with liquid glass effect
+ * @returns {Object} CSS style object with liquid glass effect
  */
 export const liquidGlassStyle = ({
   vuetifyTheme,
@@ -208,7 +209,7 @@ export const liquidGlassStyle = ({
  * @desc Generate overlap style for container (slides up into previous section)
  * @param {Boolean|String|Object} overlap - true (defaults), string ('30vh'), or { mobile: '20vh', desktop: '40vh' }
  * @param {Object} display - Vuetify display object ($vuetify.display)
- * @return {Object} Style object with margin-top, position and z-index
+ * @returns {Object} Style object with margin-top, position and z-index
  */
 export const overlapStyle = (overlap, display) => {
   if (!overlap) return {};
@@ -235,7 +236,7 @@ export const overlapStyle = (overlap, display) => {
  * @desc Helper to lighten a hex color
  * @param {String} hex - Hex color (e.g. #RRGGBB)
  * @param {Number} percent - Percentage to lighten (0-100)
- * @return {String} Hex color string
+ * @returns {String} Hex color string
  */
 export const lightenColor = (hex, percent) => adjustColor(hex, percent, 'hex');
 
diff --git a/src/lib/helpers/tools.js b/src/lib/helpers/tools.js
index db78b4463..9ea4beb6d 100644
--- a/src/lib/helpers/tools.js
+++ b/src/lib/helpers/tools.js
@@ -4,8 +4,8 @@
 
 /**
  * @desc Function to evaluate numbers of release from last release
- * @param {String} 2.3.4
- * @return {String} 23
+ * @param {String} release - Version string (e.g. '2.3.4' or 'v2.3.4')
+ * @returns {Array} Array of version number parts
  */
 export const releasesNumber = (release) => {
   const numbers = release[0] === 'v' ? release.substr(1).split('.') : release.split('.'); // get numbers last release
@@ -19,7 +19,7 @@ export const releasesNumber = (release) => {
  * @param {Int} page
  * @param {Int} perPage
  * @param {String} search
- * @return {String} server-items-length
+ * @returns {String} Pagination request string
  */
 export const pageRequest = (page, perPage, search) => {
   let request = `${page - 1}&${perPage}`;
@@ -29,9 +29,9 @@ export const pageRequest = (page, perPage, search) => {
 
 /**
  * @desc Function get a dynamic total count from dataTable
- * @param {Array} array of items
- * @param {Object} Object options from vuetify dataTable
- * @return {String} server-items-length
+ * @param {Array} items - Array of items from the current page
+ * @param {Object} options - Options object from Vuetify dataTable
+ * @returns {number} server items length
  */
 export const serverItemsLength = (items, options) =>
   items.length === options.itemsPerPage ? options.page * options.itemsPerPage + options.itemsPerPage : options.page * options.itemsPerPage;
diff --git a/src/lib/middlewares/model.js b/src/lib/middlewares/model.js
index 1b9318d33..c68cb6ecf 100644
--- a/src/lib/middlewares/model.js
+++ b/src/lib/middlewares/model.js
@@ -4,10 +4,10 @@
 import _ from 'lodash';
 
 /**
- * @desc Function to clean object (pick from model, remove null / undefined)
- * @param {Object} data
- * @param {[String]} model
- * @return {Object} result
+ * @desc Function to clean object (pick from model, remove null values)
+ * @param {Object} data - Source object to clean
+ * @param {Array} model - Array of keys to pick from data
+ * @returns {Object} Cleaned object with only model keys and non-null values
  */
 const clean = (data, model) => _.omitBy(_.pick(data, model), _.isNull);