Default development server to loopback and preserve bind interface

.agents/skills/marmite/references/cli-reference.md

@@ -201,8 +201,8 @@ marmite [site_folder] atproto publish --dry-run
 |------|-------|---------|-------------|
 | `--verbose` | `-v` | 0 (warn) | Verbosity: `-v` info, `-vv` debug, `-vvv` trace, `-vvvv` trace all |
 | `--watch` | `-w` | false | Auto-rebuild on file changes |
-| `--serve` | | false | Start built-in HTTP server |
-| `--bind <ADDR>` | | `0.0.0.0:8000` | Server bind address (requires `--serve`) |
+| `--serve` | | false | Start development-only HTTP server (not for production) |
+| `--bind <ADDR>` | | `127.0.0.1:8000` | Server bind address (requires `--serve`) |
 | `--config <FILE>` | `-c` | `marmite.yaml` | Path to config file |
 | `--force` | | false | Force full rebuild |
 

example/content/docs/getting-started.md

@@ -193,13 +193,15 @@ webserver such as **Apache** or **Nginx**, or most probably use a free
 static hosting service such as **Github pages**, **Netlify** or **CLoudflare**.
 
 However, during the content writing you want to check how the website looks,
-so the built-in server comes handy, just add `--serve`
+so the built-in development-only server comes handy, just add `--serve`.
+It defaults to `127.0.0.1:8000` and is not for production deployments.
 
 ```
 marmite myblog site --watch --serve
 ...
 Watching for changes in folder: myblog
 Starting built-in HTTP server
+Development-only server. Not for production deployments.
 Server started at http://localhost:8000/ - Type ^C to stop.
 ```
 
@@ -210,7 +212,7 @@ When the server is running, a [[marmite-toolbar]] icon appears at the top-left c
 The server also exposes a [[content-management-api]] under `/__marmite__/` for programmatic content and config management.
 
 If you want to share your site with others in the same network, just 
-pass `--bind "0.0.0.0:8000` and then share your local IP address.
+pass `--bind 0.0.0.0:8000` and then share your local IP address.
 
 ## Media
 

example/content/docs/marmite-command-line-interface.md

@@ -174,19 +174,23 @@ Watching for changed on: myblog/
 Marmite generates a flat site, which means you can open it directly on your browser (with some limitations) 
 or use any web server to serve it.
 
-Marmite comes with a built-in server to use only locally.
+Marmite comes with a development-only server, not for production deployments.
+It binds to `127.0.0.1:8000` by default.
 
 Use `--serve` to start the server.
 
 ```console
-$ /marmite myblog /var/www/myblog -w
+$ /marmite myblog /var/www/myblog -w --serve
 Site generated at: /var/www/myblog
 Watching for changed on: myblog/
 Starting built-in HTTP server...
-Server started at http://0.0.0.0:8000/ - Type ^C to stop.
+Development-only server. Not for production deployments.
+Server started at http://127.0.0.1:8000/ - Type ^C to stop.
 ```
 
-If you want to change the address use `--bind ip:port`
+If you want to change the address use `--bind ip:port`. For access from other
+machines on your network, use `--bind 0.0.0.0:8000`. If the requested port is
+unavailable, the server uses an OS-assigned port on the requested interface.
 
 > [!IMPORTANT]  
 > The built-in server is not suitable for production, when deploying use a webserver such as [Nginx] or read the [[hosting]] guide to learn how to deploy to Github pages, Gitlab pages, Codeberg Pages, Netlify and more.
@@ -591,9 +595,9 @@ Options:
   -w, --watch
           Detect changes and rebuild the site automatically
       --serve
-          Serve the site with a built-in HTTP server
+          Serve the site with a development-only HTTP server (not for production)
       --bind <BIND>
-          Address to bind the server [default: 0.0.0.0:8000]
+          Address to bind the server [default: 127.0.0.1:8000]
   -c, --config <CONFIG>
           Path to custom configuration file [default: marmite.yaml]
       --init-templates

example/content/release-notes/marmite-0-4-3-release-notes.md

@@ -0,0 +1,19 @@
+---
+date: 2026-09-29
+title: Marmite 0.4.3 Release Notes
+slug: marmite-0-4-3-release-notes
+stream: draft
+tags: [release-notes, marmite]
+---
+
+## Bug Fixes
+
+### Development server binding
+
+`--serve` now defaults to `127.0.0.1:8000`. If the requested port is unavailable,
+the fallback uses an OS-assigned port while preserving the requested interface,
+instead of binding to all interfaces. Use `--bind 0.0.0.0:8000` explicitly for
+access from other machines on your network.
+
+The CLI help and server startup message now explicitly identify the built-in
+server as development-only, not for production deployments.

src/cli.rs

@@ -52,12 +52,12 @@ pub struct Cli {
     #[arg(long, short)]
     pub watch: bool,
 
-    /// Serve the site with a built-in HTTP server
+    /// Serve the site with a development-only HTTP server (not for production)
     #[arg(long)]
     pub serve: bool,
 
     /// Address to bind the server
-    #[arg(long, default_value = "0.0.0.0:8000", requires = "serve")]
+    #[arg(long, default_value = "127.0.0.1:8000", requires = "serve")]
     pub bind: String,
 
     /// Path to custom configuration file

src/server.rs

@@ -1,8 +1,11 @@
+//! Development-only preview server and editor API, not for production deployments.
+
 use chrono::Utc;
 use log::{error, info, warn};
 use serde_json::json;
 use std::fmt::Write as _;
 use std::io::{Cursor, ErrorKind};
+use std::net::ToSocketAddrs;
 use std::path::PathBuf;
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::mpsc;
@@ -23,7 +26,6 @@ pub struct ServerContext {
     pub watch_enabled: bool,
 }
 
-const FALLBACK_BIND_ADDRESS: &str = "0.0.0.0:0";
 const LIVE_RELOAD_SCRIPT_PATH: &str = "__marmite__/livereload.js";
 const TOOLBAR_JS_PATH: &str = "__marmite__/toolbar.js";
 const TOOLBAR_CSS_PATH: &str = "__marmite__/toolbar.css";
@@ -94,23 +96,31 @@ static EDITOR_HTML: LazyLock<String> = LazyLock::new(|| {
         .expect("embedded editor.html missing - this is a build-time error")
 });
 
+fn bind_server(bind_address: &str) -> Result<Server, Box<dyn std::error::Error + Send + Sync>> {
+    let mut addresses: Vec<_> = bind_address.to_socket_addrs()?.collect();
+    Server::http(addresses.as_slice()).or_else(|err| {
+        warn!(
+            "Failed to start server on address {bind_address}: {err:?}. Falling back to OS-assigned port on the same interface."
+        );
+        // Only change the port; retain the requested IPv4/IPv6 interfaces.
+        for address in &mut addresses {
+            address.set_port(0);
+        }
+        Server::http(addresses.as_slice())
+    })
+}
+
 pub fn start(bind_address: &str, ctx: &ServerContext, live_reload: Option<&LiveReload>) {
-    let server = match Server::http(bind_address) {
+    let server = match bind_server(bind_address) {
         Ok(server) => server,
         Err(e) => {
-            warn!(
-                "Failed to start server on address {bind_address}: {e:?}. Falling back to OS-assigned port."
-            );
-            match Server::http(FALLBACK_BIND_ADDRESS) {
-                Ok(server) => server,
-                Err(e) => {
-                    error!("Failed to start server on fallback address: {e:?}");
-                    return;
-                }
-            }
+            error!("Failed to start development server: {e:?}");
+            return;
         }
     };
 
+    info!("Development-only server. Not for production deployments.");
+
     let Some(server_addr) = server.server_addr().to_ip() else {
         warn!("Failed to get server IP address, using fallback display");
         // Use a fallback approach for display purposes

src/tests/server.rs

@@ -3,6 +3,41 @@ use std::fs;
 use std::io::Read;
 use tempfile::TempDir;
 
+#[test]
+fn test_default_bind_is_loopback_and_custom_bind_is_preserved() {
+    use clap::Parser;
+
+    let args = crate::cli::Cli::try_parse_from(["marmite", ".", "--serve"]).unwrap();
+    assert_eq!(args.bind, "127.0.0.1:8000");
+    let args =
+        crate::cli::Cli::try_parse_from(["marmite", ".", "--serve", "--bind", "0.0.0.0:9000"])
+            .unwrap();
+    assert_eq!(args.bind, "0.0.0.0:9000");
+}
+
+#[test]
+fn test_bind_fallback_preserves_interface() {
+    for ip in ["127.0.0.1", "0.0.0.0", "::1"] {
+        let ip: std::net::IpAddr = ip.parse().unwrap();
+        let occupied = match std::net::TcpListener::bind((ip, 0)) {
+            Ok(listener) => listener,
+            Err(err) if ip.is_ipv6() && err.kind() == ErrorKind::AddrNotAvailable => continue,
+            Err(err) => panic!("Failed to bind test listener: {err}"),
+        };
+        let requested = occupied.local_addr().unwrap();
+        let server = bind_server(&requested.to_string()).unwrap();
+        let actual = server.server_addr().to_ip().unwrap();
+        assert_eq!(actual.ip(), requested.ip());
+        assert_ne!(actual.port(), 0);
+        assert_ne!(actual.port(), requested.port());
+    }
+}
+
+#[test]
+fn test_invalid_bind_does_not_fall_back_to_all_interfaces() {
+    assert!(bind_server("invalid-address").is_err());
+}
+
 #[test]
 fn test_render_not_found_with_file() {
     let temp_dir = TempDir::new().unwrap();