diff --git a/CHANGELOG.md b/CHANGELOG.md
index 45ed237a5a..1a155d2433 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,8 @@ and this project adheres to
 
 ## [Unreleased]
 
+## [4.0.0] - 2025-11-26
+
 ### Added
 
 - ✨ Add comments feature to the editor #1330
@@ -14,13 +16,13 @@ and this project adheres to
 ### Changed
 
 - ⚡️(sw) stop to cache external resources likes videos #1655
-- 💥(frontend) upgrade to ui-kit v2
-
-### Fixed
-
+- 💥(frontend) upgrade to ui-kit v2 #1605
 - ♿(frontend) improve accessibility:
   - ♿(frontend) improve share modal button accessibility #1626
   - ♿(frontend) improve screen reader support in DocShare modal #1628
+
+### Fixed
+
 - 🐛(frontend) fix toolbar not activated when reader #1640
 - 🐛(frontend) preserve left panel width on window resize #1588
 - 🐛(frontend) prevent duplicate as first character in title #1595
@@ -896,7 +898,8 @@ and this project adheres to
 - ✨(frontend) Coming Soon page (#67)
 - 🚀 Impress, project to manage your documents easily and collaboratively.
 
-[unreleased]: https://github.com/suitenumerique/docs/compare/v3.10.0...main
+[unreleased]: https://github.com/suitenumerique/docs/compare/v4.0.0...main
+[v4.0.0]: https://github.com/suitenumerique/docs/releases/v4.0.0
 [v3.10.0]: https://github.com/suitenumerique/docs/releases/v3.10.0
 [v3.9.0]: https://github.com/suitenumerique/docs/releases/v3.9.0
 [v3.8.2]: https://github.com/suitenumerique/docs/releases/v3.8.2
diff --git a/UPGRADE.md b/UPGRADE.md
index c167db3c2f..3fe48c1568 100644
--- a/UPGRADE.md
+++ b/UPGRADE.md
@@ -16,6 +16,29 @@ the following command inside your docker container:
 
 ## [Unreleased]
 
+## [4.0.0] - 2025-11-26
+
+- ⚠️ We updated `@gouvfr-lasuite/ui-kit` to `0.18.0`, so if you are customizing Docs with a css layer or with a custom template, you need to update your customization to follow the new design system structure.  
+More information about the changes in the design system can be found here:
+  - https://suitenumerique.github.io/cunningham/storybook/?path=/docs/migrating-from-v3-to-v4--docs
+  - https://github.com/suitenumerique/docs/pull/1605
+  - https://github.com/suitenumerique/docs/blob/main/docs/theming.md
+
+- If you were using the `THEME_CUSTOMIZATION_FILE_PATH` and have overridden the header logo, you need to update your customization file to follow the new structure of the header, it is now: 
+  ```json
+  {
+    ...,
+    "header": {
+      "icon": {
+        "src": "your_logo_src",
+        "width": "your_logo_width",
+        "height": "your_logo_height"
+      }
+    }
+  }
+  ```
+
+
 ## [3.3.0] - 2025-05-22
 
 ⚠️ For some advanced features (ex: Export as PDF) Docs relies on XL packages from BlockNote. These are licenced under AGPL-3.0 and are not MIT compatible. You can perfectly use Docs without these packages by setting the environment variable `PUBLISH_AS_MIT` to true. That way you'll build an image of the application without the features that are not MIT compatible. Read the [environment variables documentation](/docs/env.md) for more information.
diff --git a/src/backend/pyproject.toml b/src/backend/pyproject.toml
index d648ab0b85..be7c4817b9 100644
--- a/src/backend/pyproject.toml
+++ b/src/backend/pyproject.toml
@@ -7,7 +7,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "impress"
-version = "3.10.0"
+version = "4.0.0"
 authors = [{ "name" = "DINUM", "email" = "dev@mail.numerique.gouv.fr" }]
 classifiers = [
     "Development Status :: 5 - Production/Stable",
diff --git a/src/frontend/apps/e2e/package.json b/src/frontend/apps/e2e/package.json
index c19ded02f9..f7fdc64045 100644
--- a/src/frontend/apps/e2e/package.json
+++ b/src/frontend/apps/e2e/package.json
@@ -1,6 +1,6 @@
 {
   "name": "app-e2e",
-  "version": "3.10.0",
+  "version": "4.0.0",
   "repository": "https://github.com/suitenumerique/docs",
   "author": "DINUM",
   "license": "MIT",
diff --git a/src/frontend/apps/impress/package.json b/src/frontend/apps/impress/package.json
index 9ace686abc..8d0f6be924 100644
--- a/src/frontend/apps/impress/package.json
+++ b/src/frontend/apps/impress/package.json
@@ -1,6 +1,6 @@
 {
   "name": "app-impress",
-  "version": "3.10.0",
+  "version": "4.0.0",
   "repository": "https://github.com/suitenumerique/docs",
   "author": "DINUM",
   "license": "MIT",
diff --git a/src/frontend/package.json b/src/frontend/package.json
index 84433d36fe..3253b5f38a 100644
--- a/src/frontend/package.json
+++ b/src/frontend/package.json
@@ -1,6 +1,6 @@
 {
   "name": "impress",
-  "version": "3.10.0",
+  "version": "4.0.0",
   "private": true,
   "repository": "https://github.com/suitenumerique/docs",
   "author": "DINUM",
diff --git a/src/frontend/packages/eslint-plugin-docs/package.json b/src/frontend/packages/eslint-plugin-docs/package.json
index b1910bc8e7..d6d3a0a1d4 100644
--- a/src/frontend/packages/eslint-plugin-docs/package.json
+++ b/src/frontend/packages/eslint-plugin-docs/package.json
@@ -1,6 +1,6 @@
 {
   "name": "eslint-plugin-docs",
-  "version": "3.10.0",
+  "version": "4.0.0",
   "repository": "https://github.com/suitenumerique/docs",
   "author": "DINUM",
   "license": "MIT",
diff --git a/src/frontend/packages/i18n/package.json b/src/frontend/packages/i18n/package.json
index 9236666e5e..1363e9d68a 100644
--- a/src/frontend/packages/i18n/package.json
+++ b/src/frontend/packages/i18n/package.json
@@ -1,6 +1,6 @@
 {
   "name": "packages-i18n",
-  "version": "3.10.0",
+  "version": "4.0.0",
   "repository": "https://github.com/suitenumerique/docs",
   "author": "DINUM",
   "license": "MIT",
diff --git a/src/frontend/servers/y-provider/package.json b/src/frontend/servers/y-provider/package.json
index 61761fd568..29012338b3 100644
--- a/src/frontend/servers/y-provider/package.json
+++ b/src/frontend/servers/y-provider/package.json
@@ -1,6 +1,6 @@
 {
   "name": "server-y-provider",
-  "version": "3.10.0",
+  "version": "4.0.0",
   "description": "Y.js provider for docs",
   "repository": "https://github.com/suitenumerique/docs",
   "license": "MIT",
diff --git a/src/helm/helmfile.yaml.gotmpl b/src/helm/helmfile.yaml.gotmpl
index 9db4a45282..5ec646426e 100644
--- a/src/helm/helmfile.yaml.gotmpl
+++ b/src/helm/helmfile.yaml.gotmpl
@@ -1,10 +1,10 @@
 environments:
   dev:
     values:
-      - version: 3.10.0
+      - version: 4.0.0
   feature:
     values:
-      - version: 3.10.0
+      - version: 4.0.0
         feature: ci
         domain: example.com
         imageTag: demo
diff --git a/src/helm/impress/Chart.yaml b/src/helm/impress/Chart.yaml
index 68c1d58e0a..ff723e02fa 100644
--- a/src/helm/impress/Chart.yaml
+++ b/src/helm/impress/Chart.yaml
@@ -1,5 +1,5 @@
 apiVersion: v2
 type: application
 name: docs
-version:  3.10.0
+version:  4.0.0
 appVersion: latest
diff --git a/src/mail/package.json b/src/mail/package.json
index fccd5e4e49..e90a735ca8 100644
--- a/src/mail/package.json
+++ b/src/mail/package.json
@@ -1,6 +1,6 @@
 {
   "name": "mail_mjml",
-  "version": "3.10.0",
+  "version": "4.0.0",
   "description": "An util to generate html and text django's templates from mjml templates",
   "type": "module",
   "dependencies": {