diff --git a/Cargo.lock b/Cargo.lock
index e278722b7..8d8da5df4 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1007,6 +1007,31 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "craft-update"
+version = "0.1.0"
+source = "git+https://github.com/storytold/craft-libs?rev=db19c373c8d59a545972ca340987aecfb3611a4b#db19c373c8d59a545972ca340987aecfb3611a4b"
+dependencies = [
+ "chrono",
+ "dunce",
+ "egui",
+ "flate2",
+ "getrandom 0.3.4",
+ "log",
+ "plist",
+ "semver",
+ "serde",
+ "serde_json",
+ "sha2",
+ "tar",
+ "tempfile",
+ "ureq",
+ "verifysign",
+ "winreg",
+ "winsafe",
+ "zip 9.1.0",
+]
+
 [[package]]
 name = "craft-window"
 version = "0.1.0"
@@ -1133,6 +1158,12 @@ dependencies = [
  "syn 2.0.119",
 ]
 
+[[package]]
+name = "deranged"
+version = "0.5.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9e9de72ce2ad1f90dc62fa25f0f430ef85eb4b0d8fa0be4f30373bc40a21d28e"
+
 [[package]]
 name = "derive_arbitrary"
 version = "1.4.2"
@@ -1149,6 +1180,7 @@ name = "designcraft"
 version = "0.13.0"
 dependencies = [
  "arboard",
+ "craft-update",
  "craft-window",
  "designcraft-engine",
  "designcraft-ui-egui",
@@ -1256,7 +1288,7 @@ dependencies = [
  "indd",
  "kurbo",
  "log",
- "quick-xml",
+ "quick-xml 0.41.0",
  "same-file",
  "serde",
  "serde_json",
@@ -1264,7 +1296,7 @@ dependencies = [
  "thiserror 2.0.21",
  "unicode-segmentation",
  "wasm-bindgen-test",
- "zip",
+ "zip 3.0.0",
 ]
 
 [[package]]
@@ -1274,7 +1306,7 @@ dependencies = [
  "chrono",
  "designcraft-color",
  "designcraft-doc",
- "zip",
+ "zip 3.0.0",
 ]
 
 [[package]]
@@ -1299,7 +1331,7 @@ dependencies = [
  "serde",
  "serde_json",
  "thiserror 2.0.21",
- "zip",
+ "zip 3.0.0",
 ]
 
 [[package]]
@@ -1325,9 +1357,9 @@ dependencies = [
  "designcraft-geom",
  "designcraft-images",
  "log",
- "quick-xml",
+ "quick-xml 0.41.0",
  "thiserror 2.0.21",
- "zip",
+ "zip 3.0.0",
 ]
 
 [[package]]
@@ -1340,7 +1372,7 @@ dependencies = [
  "flate2",
  "image",
  "log",
- "quick-xml",
+ "quick-xml 0.41.0",
  "resvg",
  "tiff",
  "zune-core",
@@ -1395,10 +1427,10 @@ dependencies = [
  "designcraft-geom",
  "designcraft-images",
  "image",
- "quick-xml",
+ "quick-xml 0.41.0",
  "skrifa 0.47.0",
  "thiserror 2.0.21",
- "zip",
+ "zip 3.0.0",
 ]
 
 [[package]]
@@ -1425,8 +1457,8 @@ name = "designcraft-textimport"
 version = "0.13.0"
 dependencies = [
  "designcraft-doc",
- "quick-xml",
- "zip",
+ "quick-xml 0.41.0",
+ "zip 3.0.0",
 ]
 
 [[package]]
@@ -1446,6 +1478,7 @@ name = "designcraft-ui-egui"
 version = "0.13.0"
 dependencies = [
  "craft-ui",
+ "craft-update",
  "craft-window",
  "designcraft-color",
  "designcraft-compose",
@@ -1465,7 +1498,7 @@ dependencies = [
  "toml",
  "unicode-bidi",
  "web-time",
- "zip",
+ "zip 3.0.0",
 ]
 
 [[package]]
@@ -3361,6 +3394,18 @@ dependencies = [
  "jni-sys 0.3.1",
 ]
 
+[[package]]
+name = "nix"
+version = "0.31.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cf20d2fde8ff38632c426f1165ed7436270b44f199fc55284c38276f9db47c3d"
+dependencies = [
+ "bitflags 2.13.2",
+ "cfg-if",
+ "cfg_aliases",
+ "libc",
+]
+
 [[package]]
 name = "nohash-hasher"
 version = "0.2.0"
@@ -3385,6 +3430,12 @@ dependencies = [
  "windows-sys 0.61.2",
 ]
 
+[[package]]
+name = "num-conv"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "521739c6d2bac4aa25192232afe6841231376b2b26d4d9fae5ecf8ca5772e441"
+
 [[package]]
 name = "num-traits"
 version = "0.2.19"
@@ -4068,6 +4119,19 @@ version = "0.2.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b4596b6d070b27117e987119b4dac604f3c58cfb0b191112e24771b2faeac1a6"
 
+[[package]]
+name = "plist"
+version = "1.10.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "327a4cb2ad49dc48adfdc9da89e22c64d488b508c67a044d71ba729e4521a285"
+dependencies = [
+ "base64 0.23.1",
+ "indexmap",
+ "quick-xml 0.42.0",
+ "serde",
+ "time",
+]
+
 [[package]]
 name = "png"
 version = "0.18.1"
@@ -4140,6 +4204,12 @@ dependencies = [
  "zerovec",
 ]
 
+[[package]]
+name = "powerfmt"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4a6394b9e965e73d0a289ee54f589087e2c676aedf60885baf52c76b771e4958"
+
 [[package]]
 name = "ppv-lite86"
 version = "0.2.21"
@@ -4268,6 +4338,15 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "quick-xml"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "41b1177fdf999d2321d3fb46ff47159d9c1fb9ad66a4879f8c50a0b504615e9b"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "quinn"
 version = "0.11.12"
@@ -4750,7 +4829,9 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "48e13bd8c0e9365c43cfa5c9e8f9ad49d3c8444926c9aac819e0e4dc503c8fdf"
 dependencies = [
  "aws-lc-rs",
+ "log",
  "once_cell",
+ "ring",
  "rustls-pki-types",
  "rustls-webpki",
  "subtle",
@@ -4930,6 +5011,10 @@ name = "semver"
 version = "1.0.28"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8a7852d02fc848982e0c167ef163aaff9cd91dc640ba85e263cb1ce46fae51cd"
+dependencies = [
+ "serde",
+ "serde_core",
+]
 
 [[package]]
 name = "send_wrapper"
@@ -5672,6 +5757,36 @@ dependencies = [
  "zune-jpeg",
 ]
 
+[[package]]
+name = "time"
+version = "0.3.55"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cdb87b95ec50ddfa440816d227a17b2ccbdda963a316a727fda0fc4334f7d134"
+dependencies = [
+ "deranged",
+ "num-conv",
+ "powerfmt",
+ "serde_core",
+ "time-core",
+ "time-macros",
+]
+
+[[package]]
+name = "time-core"
+version = "0.1.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9e1c906769ad99c88eaa54e728060edef082f8e358ff32030cb7c7d315e81109"
+
+[[package]]
+name = "time-macros"
+version = "0.2.32"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7e689342a48d2ea927c87ea50cabf8594854bf940e9310208848d680d668ed85"
+dependencies = [
+ "num-conv",
+ "time-core",
+]
+
 [[package]]
 name = "tiny-skia"
 version = "0.12.0"
@@ -5936,6 +6051,12 @@ dependencies = [
  "rustc-hash 2.1.3",
 ]
 
+[[package]]
+name = "typed-path"
+version = "0.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9ce898823d8cd0f028662d2f349694b1af0a5cc9be83f1d213a00d3147445e1e"
+
 [[package]]
 name = "typenum"
 version = "1.20.1"
@@ -6040,6 +6161,35 @@ version = "0.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8ecb6da28b8a351d773b68d5825ac39017e680750f980f3a1a85cd8dd28a47c1"
 
+[[package]]
+name = "ureq"
+version = "3.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cde93ff05758a36a851a398a772b0b79a82fbe3c186a46f2696baaeaf84c966b"
+dependencies = [
+ "base64 0.23.1",
+ "flate2",
+ "log",
+ "percent-encoding",
+ "rustls",
+ "rustls-pki-types",
+ "rustls-platform-verifier",
+ "ureq-proto",
+ "utf8-zero",
+]
+
+[[package]]
+name = "ureq-proto"
+version = "0.6.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "841583fc36089d7d59419568ae157f43a5a03a2e5a81ba87c77d1596ef46e922"
+dependencies = [
+ "base64 0.23.1",
+ "http",
+ "httparse",
+ "log",
+]
+
 [[package]]
 name = "url"
 version = "2.5.8"
@@ -6080,6 +6230,12 @@ dependencies = [
  "xmlwriter",
 ]
 
+[[package]]
+name = "utf8-zero"
+version = "0.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b8c0a043c9540bae7c578c88f91dda8bd82e59ae27c21baca69c8b191aaf5a6e"
+
 [[package]]
 name = "utf8_iter"
 version = "1.0.4"
@@ -6177,6 +6333,16 @@ dependencies = [
  "vello_common 0.2.0",
 ]
 
+[[package]]
+name = "verifysign"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6acfcc42a8d44f340d001193d97ef56bf33210b51ad760ae8308c97d5241ca51"
+dependencies = [
+ "core-foundation 0.10.1",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "version_check"
 version = "0.9.5"
@@ -6440,7 +6606,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "338e30461b3a2b67d70eb30a6d89f8e0c93a833e07d2ae89085cd070c4a00ac0"
 dependencies = [
  "proc-macro2",
- "quick-xml",
+ "quick-xml 0.41.0",
  "quote",
 ]
 
@@ -7065,6 +7231,16 @@ dependencies = [
  "xml",
 ]
 
+[[package]]
+name = "winreg"
+version = "0.55.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cb5a765337c50e9ec252c2069be9bf91c7df47afb103b642ba3a53bf8101be97"
+dependencies = [
+ "cfg-if",
+ "windows-sys 0.59.0",
+]
+
 [[package]]
 name = "winresource"
 version = "0.1.31"
@@ -7490,6 +7666,23 @@ dependencies = [
  "zopfli",
 ]
 
+[[package]]
+name = "zip"
+version = "9.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2886b00003a72c4ccee3f42cfc34908d33b2508a74d827dc2a4244706475c704"
+dependencies = [
+ "crc32fast",
+ "flate2",
+ "getrandom 0.4.3",
+ "indexmap",
+ "memchr",
+ "nix",
+ "typed-path",
+ "windows-sys 0.61.2",
+ "zopfli",
+]
+
 [[package]]
 name = "zlib-rs"
 version = "0.6.8"
diff --git a/Cargo.toml b/Cargo.toml
index afa0d7be9..43c880e9d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,6 +13,7 @@ repository = "https://github.com/storytold/designcraft"
 [workspace.dependencies]
 # Shared reader and writer; publish the immutable revision before this consumer.
 craft-pdf = { git = "https://github.com/storytold/craft-libs", rev = "a0916808f7d78bed8c7b90cdf937176015454a7f", version = "=0.1.0", default-features = false }
+craft-update = { git = "https://github.com/storytold/craft-libs", version = "=0.1.0", rev = "db19c373c8d59a545972ca340987aecfb3611a4b", features = ["egui"] }
 # internal
 designcraft-geom = { path = "crates/geom" }
 designcraft-color = { path = "crates/color" }
diff --git a/apps/designcraft/Cargo.toml b/apps/designcraft/Cargo.toml
index 1d47ef762..36415546e 100644
--- a/apps/designcraft/Cargo.toml
+++ b/apps/designcraft/Cargo.toml
@@ -32,6 +32,7 @@ arboard = { workspace = true }
 winit = { version = "0.30", default-features = false, features = ["x11"] }
 
 [target.'cfg(windows)'.dependencies]
+craft-update = { workspace = true }
 # EnumDisplayDevices (src/gpu.rs): which GPU drives the display, so the window draws on the GPU
 # that shows it; drawing on a GPU without a monitor reset the display driver. Safe wrappers over
 # Win32 (MIT); the `user` feature is User32.dll only.
diff --git a/apps/designcraft/src/main.rs b/apps/designcraft/src/main.rs
index 12f423d79..ac695774b 100644
--- a/apps/designcraft/src/main.rs
+++ b/apps/designcraft/src/main.rs
@@ -398,6 +398,11 @@ fn control_port_from(source: &str, value: Option<String>) -> Option<u16> {
 }
 
 fn main() -> std::process::ExitCode {
+    // Windows: the update helper is a copy of this program started with `--finish-update`.
+    #[cfg(windows)]
+    if let Some(result) = craft_update::self_update::finish(&craft_update::suite::DESIGNCRAFT, &std::env::args_os().skip(1).collect::<Vec<_>>()) {
+        std::process::exit(i32::from(result.is_err()));
+    }
     // First, so every start-up record (and the engine's panic hook, installed with the first
     // Session) is captured; see `logging`.
     let logger = logging::install();
@@ -553,6 +558,7 @@ fn main() -> std::process::ExitCode {
                 session.recovery_dir = profile::recovery_dir();
                 let recovered = session.execute("file.recovery.open", &serde_json::json!({})).ok();
                 let mut app = DesignApp::new(session, services());
+                app.set_startup_update_check(true);
                 if let Some(line) = restarted.or_else(|| created.status_line()) {
                     app.status(line);
                 }
diff --git a/crates/ui-egui/Cargo.toml b/crates/ui-egui/Cargo.toml
index 0a826b69e..3d4a7c6f0 100644
--- a/crates/ui-egui/Cargo.toml
+++ b/crates/ui-egui/Cargo.toml
@@ -44,3 +44,6 @@ designcraft-fonts = { workspace = true, features = ["testing"] }
 [build-dependencies]
 serde_json = { workspace = true }
 toml = "1"
+
+[target.'cfg(not(target_arch = "wasm32"))'.dependencies]
+craft-update = { workspace = true }
diff --git a/crates/ui-egui/src/lib.rs b/crates/ui-egui/src/lib.rs
index 95d53b798..f3571d38b 100644
--- a/crates/ui-egui/src/lib.rs
+++ b/crates/ui-egui/src/lib.rs
@@ -33,6 +33,7 @@ pub mod story_editor;
 pub mod taskbar;
 pub mod theme;
 pub mod toolbar;
+pub mod updates_ui;
 pub mod widgets;
 
 use std::collections::HashMap;
@@ -836,6 +837,7 @@ pub struct DesignApp {
     pub cursors: cursors::Images,
     /// A panel's live preview (a slider being dragged), committed when it is let go.
     live_preview: LivePreview,
+    pub(crate) updates_rt: updates_ui::Runtime,
 }
 
 /// The preview a panel opened with `edit.preview`: it stays open while a panel holds it each frame.
@@ -935,6 +937,7 @@ impl DesignApp {
             quitting: None,
             cursors: cursors::Images::default(),
             live_preview: LivePreview::default(),
+            updates_rt: updates_ui::Runtime::default(),
         }
     }
 
@@ -1384,6 +1387,7 @@ impl DesignApp {
     fn logic_tick(&mut self, ctx: &egui::Context) {
         self.update_screenshot_epoch(ctx);
         self.drain_control(ctx);
+        updates_ui::tick(self, ctx);
         if self.fonts_ready && !self.host_order_pending() {
             self.drain_inbox();
             self.open_os_documents();
@@ -2149,6 +2153,7 @@ impl DesignApp {
         story_editor::show(self, &ctx);
         dialogs::show(self, &ctx);
         about::show(self, &ctx);
+        updates_ui::show(self, &ctx);
         menus::palette(self, &ctx);
         // The IME is observed once, here: after the canvas, the floating panels, the story editor,
         // dialogs and Quick Apply have all applied this pass's commands and focus changes.
diff --git a/crates/ui-egui/src/menus.rs b/crates/ui-egui/src/menus.rs
index fda15c6bb..e3226044b 100644
--- a/crates/ui-egui/src/menus.rs
+++ b/crates/ui-egui/src/menus.rs
@@ -348,6 +348,7 @@ pub const UI_COMMANDS: &[(&str, &str, Option<&str>, &str)] = &[
         None,
         "{open?: true, tab?: \"about\"|\"contributors\"|\"models\"} — the About window: splash with community links, contributor and model credits (open: false closes it)",
     ),
+    ("help.checkForUpdates", "Check for Updates…", None, "{} — checks for newer releases and offers to update"),
     ("window.toolsDoubleColumn", "Tools: Double Column", None, "{}"),
     (
         "window.workspace",
@@ -990,6 +991,7 @@ pub const MENUS: &[(&str, &[&str])] = &[
             "-",
             "cmd:file.newSample",
             "-",
+            "ui:help.checkForUpdates",
             "ui:help.about",
         ],
     ),
@@ -1911,6 +1913,7 @@ fn run_ui_inner(app: &mut DesignApp, id: &str, p: &Value) -> Option<Result<Value
             app.ui.about = p.get("open").and_then(Value::as_bool).unwrap_or(true);
             Ok(json!(app.ui.about))
         }
+        "help.checkForUpdates" => crate::updates_ui::check(app),
         "help.app" => match p.get("app").and_then(Value::as_str) {
             Some(slug) if !slug.is_empty() && slug.chars().all(|c| c.is_ascii_alphanumeric() || c == '-') => {
                 let url = format!("{}/apps/{slug}", designcraft_engine::links::WEBSITE);
@@ -2418,6 +2421,7 @@ pub enum AppMenuItem {
 /// The macOS application menu. Settings… is `app.preferences`, which `native_menu_tree` leaves out of Edit.
 pub const MAC_APP_MENU: &[AppMenuItem] = &[
     AppMenuItem::Cmd { id: "dc-about", label: "About DesignCraft", command: "help.about" },
+    AppMenuItem::Cmd { id: "dc-updates", label: "Check for Updates…", command: "help.checkForUpdates" },
     AppMenuItem::Cmd { id: "dc-discord", label: "Join the ArtCraft Discord…", command: "help.discord" },
     AppMenuItem::Sep,
     AppMenuItem::Cmd { id: "dc-settings", label: "Settings…", command: "app.preferences" },
diff --git a/crates/ui-egui/src/updates_ui.rs b/crates/ui-egui/src/updates_ui.rs
new file mode 100644
index 000000000..43803c9a5
--- /dev/null
+++ b/crates/ui-egui/src/updates_ui.rs
@@ -0,0 +1,177 @@
+//! Software updates, background check at startup, and startup prompt modal.
+
+use serde_json::Value;
+
+use crate::DesignApp;
+
+#[cfg(not(target_arch = "wasm32"))]
+use craft_update::updater::{Action, Status, Updater};
+
+pub(crate) struct Runtime {
+    #[cfg(not(target_arch = "wasm32"))]
+    updater: Updater,
+    /// The desktop app turns the check at start on; tests and the web build leave it off.
+    #[cfg(not(target_arch = "wasm32"))]
+    startup_check: bool,
+    #[cfg(not(target_arch = "wasm32"))]
+    check_requested: bool,
+    /// The context of the last frame, to wake the UI when a check is queued from a menu callback.
+    #[cfg(not(target_arch = "wasm32"))]
+    repaint: Option<egui::Context>,
+    pub(crate) manual_window_open: bool,
+    pub(crate) status_message: Option<String>,
+}
+
+impl Default for Runtime {
+    fn default() -> Self {
+        Self {
+            #[cfg(not(target_arch = "wasm32"))]
+            updater: Updater::new(&craft_update::suite::DESIGNCRAFT, env!("CARGO_PKG_VERSION")),
+            #[cfg(not(target_arch = "wasm32"))]
+            startup_check: false,
+            #[cfg(not(target_arch = "wasm32"))]
+            check_requested: false,
+            #[cfg(not(target_arch = "wasm32"))]
+            repaint: None,
+            manual_window_open: false,
+            status_message: None,
+        }
+    }
+}
+
+impl DesignApp {
+    /// Whether the app asks for a newer release when it starts (off until the desktop app turns it on).
+    #[cfg(not(target_arch = "wasm32"))]
+    pub fn set_startup_update_check(&mut self, on: bool) {
+        self.updates_rt.startup_check = on;
+    }
+}
+
+pub(crate) fn check(app: &mut DesignApp) -> Result<Value, String> {
+    #[cfg(not(target_arch = "wasm32"))]
+    {
+        app.updates_rt.check_requested = true;
+        if let Some(ctx) = &app.updates_rt.repaint {
+            ctx.request_repaint();
+        }
+        Ok(Value::Null)
+    }
+    #[cfg(target_arch = "wasm32")]
+    {
+        app.updates_rt.manual_window_open = true;
+        app.updates_rt.status_message = Some("Update check is not supported in the web browser.".into());
+        Ok(Value::Null)
+    }
+}
+
+pub(crate) fn tick(app: &mut DesignApp, ctx: &egui::Context) {
+    #[cfg(not(target_arch = "wasm32"))]
+    {
+        let rt = &mut app.updates_rt;
+        rt.repaint = Some(ctx.clone());
+        if std::mem::take(&mut rt.check_requested) {
+            rt.updater.check_now(ctx);
+        } else if rt.startup_check {
+            rt.updater.check_at_start(ctx);
+        }
+        rt.updater.tick(ctx);
+    }
+    #[cfg(target_arch = "wasm32")]
+    let _ = (app, ctx);
+}
+
+pub(crate) fn show(app: &mut DesignApp, ctx: &egui::Context) {
+    #[cfg(not(target_arch = "wasm32"))]
+    {
+        // The restart helper is scheduled before the app closes, so no update starts over unsaved work.
+        let clean = !app.session.documents().iter().any(|d| d.is_dirty());
+        match app.updates_rt.updater.show_if(ctx, clean) {
+            Action::OpenUrl(url) => ctx.open_url(egui::OpenUrl::new_tab(url)),
+            Action::Close => ctx.send_viewport_cmd(egui::ViewportCommand::Close),
+            Action::None => {}
+        }
+        // The window answers Help ▸ Check for Updates, so it follows the updater's status.
+        let rt = &mut app.updates_rt;
+        (rt.manual_window_open, rt.status_message) = match rt.updater.status() {
+            Status::Idle => (false, None),
+            Status::Checking => (true, Some(crate::i18n::tr(&app.ui.language, "Checking for updates…").to_string())),
+            Status::UpToDate => (
+                true,
+                Some(
+                    crate::i18n::tr(&app.ui.language, "DesignCraft {version} is currently the newest version available.")
+                        .replace("{version}", env!("CARGO_PKG_VERSION")),
+                ),
+            ),
+            Status::Failed(e) => (true, Some(crate::i18n::tr(&app.ui.language, "Could not check for updates:\n{error}").replace("{error}", e))),
+        };
+    }
+
+    if app.updates_rt.manual_window_open {
+        let mut open = true;
+        let title = crate::i18n::tr(&app.ui.language, "DesignCraft Updates");
+        let ok_label = crate::i18n::tr(&app.ui.language, "OK");
+        egui::Window::new(title)
+            .open(&mut open)
+            .collapsible(false)
+            .resizable(false)
+            .pivot(egui::Align2::CENTER_CENTER)
+            .default_pos(ctx.content_rect().center())
+            .show(ctx, |ui| {
+                if let Some(msg) = &app.updates_rt.status_message {
+                    ui.label(msg);
+                }
+                ui.add_space(8.0);
+                if ui.button(ok_label).clicked() {
+                    app.updates_rt.manual_window_open = false;
+                }
+            });
+        if !open {
+            app.updates_rt.manual_window_open = false;
+        }
+    }
+
+    // Closing the window dismisses the outcome it showed.
+    #[cfg(not(target_arch = "wasm32"))]
+    if !app.updates_rt.manual_window_open {
+        app.updates_rt.updater.dismiss_status();
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use designcraft_engine::Session;
+
+    #[test]
+    fn default_runtime_is_idle() {
+        let rt = Runtime::default();
+        assert!(!rt.manual_window_open);
+        #[cfg(not(target_arch = "wasm32"))]
+        {
+            assert!(!rt.startup_check);
+            assert!(!rt.updater.prompt_open());
+            assert_eq!(rt.updater.status(), &Status::Idle);
+        }
+    }
+
+    #[test]
+    #[cfg(not(target_arch = "wasm32"))]
+    fn startup_prompt_shows_and_closes() {
+        let mut app = DesignApp::new(Session::new(), Default::default());
+        let ctx = egui::Context::default();
+        let release = craft_update::Release {
+            tag: "v99.0.0".into(),
+            version: craft_update::parse_version("99.0.0"),
+            name: "DesignCraft 99.0.0".into(),
+            html_url: "https://github.com/storytold/designcraft/releases/tag/v99.0.0".into(),
+            ..Default::default()
+        };
+        app.updates_rt.updater.offer(release);
+
+        let mut output = ctx.run_ui(egui::RawInput::default(), |ui| {
+            show(&mut app, ui.ctx());
+        });
+        output.textures_delta.clear();
+        assert!(app.updates_rt.updater.prompt_open());
+    }
+}