feat!: Replace HTTP/2 support with HTTPS

internal/documentation/docs/pages/Configuration.md

@@ -655,7 +655,7 @@ server:
 
 :::
 
-By default, UI5 CLI will serve applications using Port `8080`. When running in HTTP/2 or HTTPS mode, Port `8443` will be used.
+By default, UI5 CLI will serve applications using Port `8080`. When running in HTTPS mode, Port `8443` will be used.
 
 If the default port is already in use, the next highest free port will be used.
 

internal/documentation/docs/pages/Overview.md

@@ -112,11 +112,11 @@ By placing this file in the root directory of the `my.app` application project,
 
 The structure of the dependency definition file follows that of the [`@ui5/project/graph/providers/DependencyTree~TreeNode`](../api/@ui5_project_graph_providers_DependencyTree.html#~TreeNode) type.
 
-## HTTP/2 Development Webserver
-The UI5 CLI contains a web server to serve the project via HTTP/2 protocol.
+## HTTPS Development Webserver
+The UI5 CLI contains a web server to serve the project via HTTPS protocol.
 
 ```sh
-ui5 serve --h2
+ui5 serve --https
 ```
 
 This requires an SSL certificate. You are guided through the automatic generation process. Also see the [UI5 Server documentation](./Server.md#ssl-certificates)

internal/documentation/docs/pages/Server.md

@@ -228,7 +228,7 @@ A project graph can be served only once. Do not call both `serveMiddleware` and
 :::
 
 ## SSL Certificates
-When starting the UI5 Server in HTTPS- or HTTP/2 mode, for example by using UI5 CLI parameter `--h2`, you will be prompted for the automatic generation of a local SSL certificate if necessary.
+When starting the UI5 Server in HTTPS mode, for example by using UI5 CLI parameter `--https`, you will be prompted for the automatic generation of a local SSL certificate if necessary.
 
 Follow the given instructions and enter your password to install the generated certificate as trusted. You can find the generated certificate and corresponding private key under `.ui5/server` in your user's home directory.
 

internal/documentation/docs/pages/Troubleshooting.md

@@ -18,7 +18,7 @@ UI5 CLI stores several kinds of data under your user's home directory in `~/.ui5
 | ---- | ---- | ---- |
 | `~/.ui5/framework/` | Downloaded UI5 framework dependencies (one copy per version) | Yes — re-downloaded on next invocation |
 | `~/.ui5/buildCache/` | Build cache used by `ui5 build` and `ui5 serve` (see [Build Cache Control](./Builder.md#build-cache-control)) | Yes — rebuilt on next `ui5 build` / `ui5 serve` |
-| `~/.ui5/server/` | Locally generated SSL certificate and private key for HTTPS / HTTP/2 mode | Yes — regenerated on next HTTPS server start; the new certificate must be re-trusted |
+| `~/.ui5/server/` | Locally generated SSL certificate and private key for HTTPS mode | Yes — regenerated on next HTTPS server start; the new certificate must be re-trusted |
 
 #### Resolution
 

internal/documentation/docs/updates/migrate-v5.md

@@ -356,6 +356,20 @@ The SAP Theme Designer can create custom themes based on CSS variables instead o
 
 With UI5 CLI v5, the `--experimental-css-variables` option has therefore been removed for the `ui5 build` command. For custom theme creation with CSS variables, please check out the **SAP Theme Designer**.
 
+## Removal of HTTP/2 Support
+
+Support for the HTTP/2 protocol has been removed from the development server. The underlying `spdy` package is unmaintained and does not work with Node.js v24 and higher. HTTP/2 was rarely needed for local development, as browsers handle HTTP/1.1 well.
+
+The `--h2` option of the `ui5 serve` command has therefore been removed and replaced by the new `--https` option, which serves the project over HTTPS using Node.js' built-in HTTPS server:
+
+```sh
+ui5 serve --https
+```
+
+Like the previous `--h2` option, `--https` requires an SSL certificate and guides you through the automatic generation process on first use. See the [UI5 Server documentation](../pages/Server.md#ssl-certificates) for details.
+
+If you genuinely need HTTP/2 for local development, put a reverse proxy (e.g. [nginx](https://nginx.org/)) in front of the UI5 Server and let it terminate HTTP/2 towards the browser (manual setup).
+
 ## `sap-ui-version.json`
 
 When you run `ui5 build`, the standard task [`generateVersionInfo`](../api/module-@ui5_builder_tasks_generateVersionInfo) now runs by default. This task generates an `sap-ui-version.json` file in the `resources/` directory. The task runs for all build types (default, jsdoc, and self-contained) in projects of type `application`. For other project types (such as `library`), the behavior remains unchanged: [`generateVersionInfo`](../api/module-@ui5_builder_tasks_generateVersionInfo) does not run.