diff --git a/app/settings/Settings.zig b/app/settings/Settings.zig
index 3aaa03ada..ddd7c9e12 100644
--- a/app/settings/Settings.zig
+++ b/app/settings/Settings.zig
@@ -8,7 +8,13 @@ const build_opts = @import("build_opts");
 
 const Settings = @This();
 
-pub const default_theme = "Fizzy Dark";
+/// The theme a fresh settings store starts with: the app's (`-Dapp-default-theme`,
+/// `build/app.zig`), or fizzy's. It names one of the themes the editor registers (fizzy's, the
+/// user's, or the app's own at `-Dapp-theme`); a name nothing registered logs and falls back.
+pub const default_theme = if (@hasDecl(build_opts, "app_default_theme") and build_opts.app_default_theme.len > 0)
+    build_opts.app_default_theme
+else
+    "Fizzy Dark";
 
 /// Duration after the last edit before autosave runs (during normal operation).
 pub const autosave_timeout_ns: i128 = 500 * 1_000_000;
diff --git a/build/app.zig b/build/app.zig
index e42e3ea2a..48987a76f 100644
--- a/build/app.zig
+++ b/build/app.zig
@@ -105,6 +105,7 @@ pub const Config = struct {
     app_repo_url_set: bool,
     app_issues_url: []const u8,
     app_layout_path: ?std.Build.LazyPath,
+    app_theme_path: ?std.Build.LazyPath,
     web_storage: []const u8,
     static_workbench: bool,
     static_text: bool,
@@ -526,7 +527,23 @@ pub fn readConfig(b: *std.Build, target: std.Build.ResolvedTarget, opts: Options
         "app-layout",
         "App-owned layout file (pub fn layout(?*anyopaque, *Layout))",
     );
+    // A consumer that wants its own themes passes `-Dapp-theme=` (a LazyPath to
+    // `pub fn add(gpa, themes: *std.ArrayList(dvui.Theme)) !void`), which the editor appends
+    // beside the user's, and `-Dapp-default-theme=` names the theme a fresh settings store
+    // starts with. Fizzy itself ships its own three and starts on `Fizzy Dark`.
+    const app_theme_path = b.option(
+        std.Build.LazyPath,
+        "app-theme",
+        "App-owned themes file (pub fn add(gpa, *std.ArrayList(dvui.Theme)) !void)",
+    );
+    const app_default_theme = b.option(
+        []const u8,
+        "app-default-theme",
+        "The theme a fresh settings store starts with (default: Fizzy Dark)",
+    );
     build_opts.addOption(bool, "has_app_layout", app_layout_path != null);
+    build_opts.addOption(bool, "has_app_theme", app_theme_path != null);
+    build_opts.addOption([]const u8, "app_default_theme", app_default_theme orelse "");
     // The frame of fizzy's own shape an app keeps (`src/editor/Chrome.zig`); the defaults are
     // fizzy's own.
     const chrome_sidebar_edge = b.option(
@@ -631,6 +648,7 @@ pub fn readConfig(b: *std.Build, target: std.Build.ResolvedTarget, opts: Options
         .app_repo_url_set = app_repo_url_set,
         .app_issues_url = app_issues_url,
         .app_layout_path = app_layout_path,
+        .app_theme_path = app_theme_path,
         .web_storage = web_storage,
         .static_workbench = static_workbench,
         .static_text = static_text,
@@ -696,6 +714,7 @@ pub fn construct(
         assets_module,
         app_icon_module,
         cfg.app_layout_path,
+        cfg.app_theme_path,
         try @import("sdk.zig").pluginsFor(b, opts.app_plugins, .web),
         opts.web_plugin_deps,
         opts.web_plugin_dirs,
@@ -784,6 +803,7 @@ fn native(
     const app_repo_url = cfg.app_repo_url;
     const app_repo_url_fallback = cfg.app_repo_url_fallback;
     const app_layout_path = cfg.app_layout_path;
+    const app_theme_path = cfg.app_theme_path;
     const static_workbench = cfg.static_workbench;
     const static_text = cfg.static_text;
     const static_image = cfg.static_image;
@@ -808,6 +828,7 @@ fn native(
         velopack_enabled,
         app_name,
         app_layout_path,
+        app_theme_path,
         app_plugins,
         dynamic_plugins,
     );
@@ -857,6 +878,7 @@ fn native(
             true,
             app_name,
             app_layout_path,
+            app_theme_path,
             app_plugins,
             dynamic_plugins,
         );
@@ -1535,6 +1557,11 @@ fn addTests(
         .optimize = optimize,
         .root_source_file = b.path("src/fizzy.zig"),
     });
+    // The app's themes module, when the build was given one (`-Dapp-theme`): the editor's
+    // comptime `has_app_theme` branch imports it.
+    if (cfg.app_theme_path) |path| {
+        fizzy_test_module.addAnonymousImport("app_theme", .{ .root_source_file = path });
+    }
     fizzy_test_module.addImport("dvui", dvui_testing_dep.module("dvui_testing"));
     fizzy_test_module.addImport("backend", dvui_testing_dep.module("testing"));
     // The testing backend has no viewports (`backend_web.viewports`).
diff --git a/build/exe.zig b/build/exe.zig
index 438b337a7..57e76099b 100644
--- a/build/exe.zig
+++ b/build/exe.zig
@@ -290,6 +290,9 @@ pub fn addFizzyExecutableForTarget(
     /// `Host.layout_ctx`. The file imports `dvui`, `app`, `core`, and `fizzy_sdk` — not
     /// `fizzy` / `Editor` — so the module graph does not cycle.
     app_layout: ?std.Build.LazyPath,
+    /// Consumer-owned themes file (`-Dapp-theme`). When set, Editor appends its themes beside
+    /// the user's. The file imports `dvui`.
+    app_theme: ?std.Build.LazyPath,
     /// Every plugin the application links, in registration order: fizzy's own
     /// (`fizzy.plugins`, built here) and the application's, each a static module from a plugin
     /// package (`plugin_dep.module("plugin")`). Listed in the generated `bundled_plugins` module
@@ -458,6 +461,7 @@ pub fn addFizzyExecutableForTarget(
         sdk_module,
         exe.root_module,
     );
+    sdk.wireAppThemes(b, resolved_target, optimize, app_theme, dvui_mod, exe.root_module);
 
     var dylibs: std.ArrayList(Dylib) = .empty;
     const workbench_dylib: ?*std.Build.Step.Compile = if (dynamic_plugins and
diff --git a/build/sdk.zig b/build/sdk.zig
index f5d25fbae..eebc22865 100644
--- a/build/sdk.zig
+++ b/build/sdk.zig
@@ -279,6 +279,28 @@ pub fn wireAppLayout(
     }
 }
 
+/// Wire an app-owned themes module against this target's framework modules: the editor appends
+/// its themes beside the user's when the build was given one (`-Dapp-theme`, see
+/// `build/app.zig`).
+pub fn wireAppThemes(
+    b: *std.Build,
+    target: std.Build.ResolvedTarget,
+    optimize: std.lang.OptimizeMode,
+    app_theme: ?std.Build.LazyPath,
+    dvui: *std.Build.Module,
+    consumer: *std.Build.Module,
+) void {
+    if (app_theme) |path| {
+        const mod = b.createModule(.{
+            .target = target,
+            .optimize = optimize,
+            .root_source_file = path,
+        });
+        mod.addImport("dvui", dvui);
+        consumer.addImport("app_theme", mod);
+    }
+}
+
 /// The whole of a `.zon` shape's generated module: import the file as a `Shape` — which is where
 /// it is type-checked, at comptime, against the field names and enums `Shape` declares —
 /// and hand it to the same walk a hand-written shape's calls would have performed itself.
diff --git a/build/web.zig b/build/web.zig
index 5d397e0dc..d18753184 100644
--- a/build/web.zig
+++ b/build/web.zig
@@ -129,6 +129,7 @@ pub fn build(
     /// The window's icon (`app.Branding.png`); `src/Entry.zig` imports it.
     app_icon_module: *std.Build.Module,
     app_layout: ?std.Build.LazyPath,
+    app_theme: ?std.Build.LazyPath,
     app_plugins: []const sdk.BundledPlugin,
     web_plugin_deps: []const []const u8,
     web_plugin_dirs: []const @import("app.zig").WebPluginDir,
@@ -352,6 +353,7 @@ pub fn build(
         sdk_module_web,
         web_exe.root_module,
     );
+    sdk.wireAppThemes(b, web_target, optimize, app_theme, dvui_web, web_exe.root_module);
 
     // Cache-buster: stamps a 64-char hash into the index.html / fizzy.js placeholders so
     // the browser picks up new wasm builds without manual hard-reloads. Re-implements
diff --git a/sdk/src/Host.zig b/sdk/src/Host.zig
index 8faacf0d9..699efe2c0 100644
--- a/sdk/src/Host.zig
+++ b/sdk/src/Host.zig
@@ -35,6 +35,14 @@ pub const OpenAction = @import("menus.zig").OpenAction;
 pub const accounts = @import("accounts.zig");
 pub const Command = @import("Command.zig");
 pub const Demo = @import("Demo.zig");
+
+/// A theme a plugin registered (`Host.registerTheme`): the theme by value, its name the host's
+/// own copy, and who registered it, so the themes go with the plugin when it retires.
+pub const HostTheme = struct {
+    owner: ?*Plugin = null,
+    name: []u8,
+    theme: dvui.Theme,
+};
 pub const Claim = @import("Claim.zig");
 pub const Step = @import("Step.zig");
 pub const Author = @import("Author.zig");
@@ -265,6 +273,8 @@ open_actions: std.ArrayList(OpenAction) = .empty,
 demos: std.ArrayList(Demo) = .empty,
 /// Moves whenever `demos` changes, so the app lists them again only then.
 demos_generation: u32 = 0,
+/// Plugins' themes (`registerTheme`): the theme by value, and its name the host's own copy.
+themes: std.ArrayList(HostTheme) = .empty,
 /// Who the user is signed in as, per service (`accounts.Provider`). The host draws the disc.
 account_providers: std.ArrayList(accounts.Provider) = .empty,
 /// Pure-data menu leaf items the native (macOS NSMenu) menu builder consumes; see
@@ -390,6 +400,8 @@ pub fn deinit(self: *Host) void {
     self.open_actions.deinit(self.allocator);
     for (self.demos.items) |d| self.freeDemo(d);
     self.demos.deinit(self.allocator);
+    for (self.themes.items) |t| self.allocator.free(t.name);
+    self.themes.deinit(self.allocator);
     self.account_providers.deinit(self.allocator);
     self.native_menu_items.deinit(self.allocator);
     self.commands.deinit(self.allocator);
@@ -1078,6 +1090,7 @@ fn dropRegistrations(self: *Host, plugin: *Plugin) void {
     removeOwned(MenuSectionContribution, &self.menu_sections, plugin);
     removeOwned(OpenAction, &self.open_actions, plugin);
     removeOwned(RailItemContribution, &self.rail_items, plugin);
+    self.removeThemesOf(plugin);
     self.removeDemosOf(plugin);
     removeOwned(accounts.Provider, &self.account_providers, plugin);
     removeOwned(NativeMenuItem, &self.native_menu_items, plugin);
@@ -1648,6 +1661,36 @@ fn freeDemo(self: *Host, d: Demo) void {
     self.allocator.free(d.tape);
 }
 
+/// Register a theme the editor appends beside the user's and the app's — see
+/// `Editor.themes`. Copied: only the theme's `name` is kept; its font families must outlive
+/// the registration (literals, as `Font.find` takes). A theme of the same name replaces the
+/// old entry in place, so a reloaded plugin updates its theme instead of duplicating it.
+pub fn registerTheme(self: *Host, owner: ?*Plugin, theme: dvui.Theme) !void {
+    const name = try self.allocator.dupe(u8, theme.name);
+    errdefer self.allocator.free(name);
+    for (self.themes.items) |*t| {
+        if (std.mem.eql(u8, t.name, theme.name)) {
+            self.allocator.free(t.name);
+            t.* = .{ .owner = owner, .name = name, .theme = theme };
+            return;
+        }
+    }
+    try self.themes.append(self.allocator, .{ .owner = owner, .name = name, .theme = theme });
+}
+
+fn removeThemesOf(self: *Host, plugin: *Plugin) void {
+    var w: usize = 0;
+    for (self.themes.items) |t| {
+        if (t.owner == plugin) {
+            self.allocator.free(t.name);
+            continue;
+        }
+        self.themes.items[w] = t;
+        w += 1;
+    }
+    self.themes.items.len = w;
+}
+
 fn removeDemosOf(self: *Host, plugin: *Plugin) void {
     var w: usize = 0;
     for (self.demos.items) |d| {
@@ -3160,6 +3203,38 @@ test "pluginForExtension honors a user assignment and ignores a stale one" {
     Fake.override = null;
 }
 
+test "registerTheme keeps its own copy, replaces by name, and a plugin's themes go with it" {
+    var host = Host.init(testing.allocator);
+    defer host.deinit();
+    const vtable = Plugin.VTable{};
+    var plugin = Plugin{ .state = undefined, .vtable = &vtable, .id = "guide", .display_name = "Guide" };
+    try host.registerPlugin(&plugin);
+
+    var name_buf = "Graphl Dark".*;
+    var theme = dvui.Theme.builtin.adwaita_dark;
+    theme.name = &name_buf;
+    try host.registerTheme(&plugin, theme);
+    // Nothing points into what the plugin handed over.
+    name_buf[0] = 'x';
+    try testing.expectEqualStrings("Graphl Dark", host.themes.items[0].name);
+    try testing.expect(host.themes.items[0].theme.dark);
+    try testing.expectEqual(@as(usize, 1), host.themes.items.len);
+
+    // Same name replaces in place rather than duplicating.
+    theme = dvui.Theme.builtin.adwaita_light;
+    theme.name = "Graphl Dark";
+    try host.registerTheme(&plugin, theme);
+    try testing.expectEqual(@as(usize, 1), host.themes.items.len);
+    try testing.expect(!host.themes.items[0].theme.dark);
+
+    theme.name = "Graphl Light";
+    try host.registerTheme(&plugin, theme);
+    try testing.expectEqual(@as(usize, 2), host.themes.items.len);
+
+    host.unregisterPlugin(&plugin);
+    try testing.expectEqual(@as(usize, 0), host.themes.items.len);
+}
+
 test "registerDemo keeps its own copy, refuses a name twice, and a plugin's demos go with it" {
     var host = Host.init(testing.allocator);
     defer host.deinit();
diff --git a/sdk/src/version.zig b/sdk/src/version.zig
index 3ec330ffc..1a7a09640 100644
--- a/sdk/src/version.zig
+++ b/sdk/src/version.zig
@@ -75,7 +75,7 @@ pub const sdk_version = @import("sdk_version").sdk_version;
 /// why it is a single target/mode-invariant literal rather than a per-target table. Update this
 /// value from the `@compileError` it triggers whenever it changes; leave `sdk_version` to the
 /// next SDK release.
-pub const recorded_sdk_shape_fingerprint: u64 = 0x2d68c9a0cdaef363;
+pub const recorded_sdk_shape_fingerprint: u64 = 0x271ebd51f39b07ed;
 
 comptime {
     if (dylib.sdk_shape_fingerprint != recorded_sdk_shape_fingerprint) {
diff --git a/src/editor/Editor.zig b/src/editor/Editor.zig
index d315cbcee..73d869609 100644
--- a/src/editor/Editor.zig
+++ b/src/editor/Editor.zig
@@ -642,6 +642,15 @@ pub fn init(
             };
         }
 
+        // The app's own themes, contributed at `-Dapp-theme` (see `build/app.zig`). Before
+        // fizzy's own, so an app's themes sit beside the user's at the top of the picker.
+        if (comptime build_opts.has_app_theme) {
+            @import("app_theme").add(app.allocator, &editor.themes) catch |err| {
+                dvui.log.err("Failed to append the app's themes: {t}", .{err});
+                return error.FailedToAppendAppThemes;
+            };
+        }
+
         editor.themes.append(app.allocator, fizzy_dark) catch {
             dvui.log.err("Failed to append theme", .{});
             return error.FailedToAppendTheme;
@@ -1737,6 +1746,8 @@ const WebPluginRequest = struct {
         }
         rebuildKeybinds(editor);
         editor.rebuildExtensionOwnerCache();
+        editor.pullPluginContributions() catch |err|
+            dvui.log.err("web plugin '{s}': themes: {s}", .{ req.id, @errorName(err) });
         if (takeWebFileTypePrompt(gpa, req.id)) editor.maybeShowFileTypeDialog(req.id) catch |err|
             dvui.log.err("web plugin '{s}': file-type prompt: {s}", .{ req.id, @errorName(err) });
         // Remembered here, not by the page when it linked the module: the page cannot know
@@ -2365,6 +2376,8 @@ pub fn postInit(editor: *Editor) !void {
     // Settings so its icon sits directly above the cog in the sidebar rail.
     try PluginStore.register(editor.pluginManager());
 
+    try editor.pullPluginContributions();
+
     // Fizzy built-in: Settings (owner = null; not a plugin).
     try editor.app.host.registerSurface(.{
         .id = view_settings,
@@ -3627,6 +3640,33 @@ fn shapedTheme(editor: *const Editor, base: dvui.Theme) dvui.Theme {
     return theme;
 }
 
+/// What plugins registered in `initPlugin` that the editor holds itself, pulled once they have
+/// initialized (at startup, and when a web plugin loads), since the editor's own apply ran in
+/// `init`, before any plugin existed: their themes. Re-applies the settings theme when any came.
+fn pullPluginContributions(editor: *Editor) !void {
+    if ((try editor.importHostThemes()) > 0) try editor.applySettingsTheme();
+}
+
+/// Pull the themes plugins registered (`Host.registerTheme`) into `editor.themes`: an entry
+/// of the same name is replaced in place, new ones appended. Returns how many it pulled, so the
+/// caller knows whether to re-apply the settings theme.
+pub fn importHostThemes(editor: *Editor) !usize {
+    var changed: usize = 0;
+    for (editor.app.host.themes.items) |ht| {
+        var replaced = false;
+        for (editor.themes.items) |*t| {
+            if (std.mem.eql(u8, t.name, ht.name)) {
+                t.* = ht.theme;
+                replaced = true;
+                break;
+            }
+        }
+        if (!replaced) try editor.themes.append(editor.app.gpa, ht.theme);
+        changed += 1;
+    }
+    return changed;
+}
+
 pub fn applySettingsTheme(editor: *Editor) !void {
     const t = resolveSettingsTheme(editor);
     if (!std.mem.eql(u8, editor.app.settings.theme, t.name)) {