feat: move color themes into a bundled themes plugin

CHANGELOG.md

@@ -14,6 +14,8 @@
 
 - The icon rail, sidebar, tab bar, dock, Dashboard, Manage, Settings and command palette now come from a bundled layout. It can be swapped for another layout but not removed, and a fix to it no longer needs a Termix release
 - Your theme is saved to your account so your other devices use it too, unless you keep settings on this device only
+- The themes besides light and dark now come from a bundled themes plugin. It can be swapped but not removed, and Termix keeps a basic light and dark theme of its own
+- A theme that no longer exists shows as System instead of an unstyled page
 
 ## 26.10.2
 

docker/bundled-plugins.json

@@ -35,6 +35,13 @@
       "sha256": "3a51cc9a4c966478f2ebfd58dbbe025ff0ebe8bbdcd3ba73156151e555f62dec",
       "defaultLook": true
     },
+    {
+      "id": "classic-themes",
+      "source": "tmxplug",
+      "url": "https://github.com/Termix-SSH/Plugin-Classic-Themes/releases/download/v1.0.0/classic-themes-1.0.0.tmxplug",
+      "sha256": "17561e569811476ea4e1f7cdf8d9afbe33edf061bd09f6b05699b44968da41ad",
+      "defaultLook": true
+    },
     {
       "id": "docker",
       "source": "tmxplug",

packages/plugin-sdk/CHANGELOG.md

@@ -13,6 +13,8 @@ Plugin API 1.4.0.
 - `validateThemeCss()` in `@termix-ssh/plugin-sdk/manifest`
 - `@termix-ssh/plugin-sdk/ui` also exports what a whole layout is built from: the API client, shared types, hooks, `useShellController()` and `APP_VERSION`. These reach into core, so they can change with a core release
 - `@termix-ssh/plugin-sdk/testing-host` exports the registries and permission seam a layout's own tests fill directly
+- A plugin that only holds themes needs no source: `termix-plugin build` writes an empty backend and `validate` does not ask for a frontend
+- `termix-plugin validate` flags `ui:layout` or `ui:theme` with nothing contributed, and a layout plugin with no frontend
 
 ### Fixed
 

packages/plugin-sdk/PLUGIN-GUIDE.md

@@ -563,6 +563,17 @@ inside `@media` or `@supports`. `@import`, `url()` to another host and other at-
 `termix-plugin validate` and by the server. Set the same tokens core's themes set (`--background`,
 `--foreground`, `--card`, `--border`, `--muted` and the rest).
 
+A plugin that only holds themes needs no code. Leave out `src/`: `termix-plugin build` writes an empty backend and
+`validate` does not ask for a frontend. Keep the CSS in `themes/` and a test that checks it with
+`validateThemeCss()`. Notes:
+
+- A theme with the id of a built-in (`light` or `dark`) replaces core's basic copy while the plugin runs.
+- The first theme a bundled default-look plugin lists is the default for new installs.
+- Themes show in the picker in the order core lists its own, then the plugin's order.
+- A theme someone saved that no longer exists shows as System. It comes back when the plugin does.
+- Accent color, UI font, font size and density are not part of a theme. Core applies them on top.
+- Bundled Classic Themes (https://github.com/Termix-SSH/Plugin-Classic-Themes) is a full example.
+
 ## Looking native
 
 Build UI from `@termix-ssh/plugin-sdk/ui` so it matches Termix and follows the theme. The full list of

packages/plugin-sdk/cli/commands/build.mjs

@@ -5,7 +5,12 @@ import { fileURLToPath } from "node:url";
 import * as esbuild from "esbuild";
 import { BACKEND_EXTERNALS, FRONTEND_EXTERNALS } from "../lib/externals.mjs";
 import { staticUrlImports } from "../lib/static-url-imports.mjs";
-import { readManifest, resolveEntry, copyDir } from "../lib/plugin-dir.mjs";
+import {
+  readManifest,
+  resolveEntry,
+  copyDir,
+  isThemeOnly,
+} from "../lib/plugin-dir.mjs";
 import { openapi } from "./openapi.mjs";
 import { splitByCoreClasses } from "../lib/css-classes.mjs";
 
@@ -232,32 +237,41 @@ export async function build({ cwd }) {
   fs.mkdirSync(outDir, { recursive: true });
 
   const backendEntry = resolveEntry(cwd, BACKEND_ENTRIES);
-  if (!backendEntry) {
+  if (!backendEntry && !isThemeOnly(manifest)) {
     throw new Error(
       `${pluginId}: no backend entry (looked for ${BACKEND_ENTRIES.join(", ")})`,
     );
   }
 
-  await esbuild.build({
-    entryPoints: [backendEntry],
-    outfile: path.join(outDir, "backend.js"),
-    bundle: true,
-    format: "esm",
-    platform: "node",
-    target: "node22",
-    sourcemap: true,
-    logLevel: "warning",
-    // A native dependency's compiled .node binary is resolved by the
-    // package's own relative paths, which break once esbuild inlines its JS
-    // elsewhere. Declaring it in nativeDependencies keeps it a real
-    // node_modules import instead, resolved at runtime like a host-provided
-    // package.
-    external: [...BACKEND_EXTERNALS, ...(manifest.nativeDependencies ?? [])],
-    loader: BINARY_LOADERS,
-    // Bundled CJS deps still call require() for Node builtins at runtime.
-    // ESM has no ambient require, so give esbuild's require shim a real one.
-    banner: { js: REQUIRE_BANNER },
-  });
+  if (backendEntry) {
+    await esbuild.build({
+      entryPoints: [backendEntry],
+      outfile: path.join(outDir, "backend.js"),
+      bundle: true,
+      format: "esm",
+      platform: "node",
+      target: "node22",
+      sourcemap: true,
+      logLevel: "warning",
+      // A native dependency's compiled .node binary is resolved by the
+      // package's own relative paths, which break once esbuild inlines its JS
+      // elsewhere. Declaring it in nativeDependencies keeps it a real
+      // node_modules import instead, resolved at runtime like a host-provided
+      // package.
+      external: [...BACKEND_EXTERNALS, ...(manifest.nativeDependencies ?? [])],
+      loader: BINARY_LOADERS,
+      // Bundled CJS deps still call require() for Node builtins at runtime.
+      // ESM has no ambient require, so give esbuild's require shim a real one.
+      banner: { js: REQUIRE_BANNER },
+    });
+  } else {
+    // Core loads every plugin through a backend entry, so a theme only
+    // plugin gets an empty one.
+    fs.writeFileSync(
+      path.join(outDir, "backend.js"),
+      "export function activate() {}\n",
+    );
+  }
 
   for (const worker of readWorkerEntries(cwd, pluginId)) {
     await esbuild.build({

packages/plugin-sdk/cli/commands/validate.mjs

@@ -1,7 +1,7 @@
 import fs from "node:fs";
 import path from "node:path";
 import { fileURLToPath } from "node:url";
-import { readManifest } from "../lib/plugin-dir.mjs";
+import { readManifest, isThemeOnly } from "../lib/plugin-dir.mjs";
 
 /**
  * The manifest rules live in src/manifest.ts, which the server uses too, so
@@ -25,7 +25,8 @@ export async function validate({ cwd }) {
   // The manifest names files. They have to be there.
   const referenced = [
     raw.backend ?? "dist/backend.js",
-    raw.frontend ?? "dist/frontend.js",
+    // A theme only plugin has no frontend code.
+    ...(isThemeOnly(raw) ? [] : [raw.frontend ?? "dist/frontend.js"]),
     raw.locales ?? "locales",
   ];
   for (const rel of referenced) {
@@ -35,6 +36,7 @@ export async function validate({ cwd }) {
   }
 
   problems.push(...validateThemeFiles(cwd, raw, validateThemeCss));
+  problems.push(...validateLookCapabilities(cwd, raw));
   problems.push(
     ...(await validateMigrations(cwd, raw.id ?? path.basename(cwd))),
   );
@@ -78,6 +80,39 @@ export function validateThemeFiles(cwd, raw, validateThemeCss) {
   return problems;
 }
 
+/**
+ * ui:layout and ui:theme must match what the manifest contributes, both
+ * ways. The manifest check already flags a contribution without its
+ * capability; this flags a capability with nothing behind it, and a layout
+ * with no frontend to register it.
+ */
+export function validateLookCapabilities(cwd, raw) {
+  const problems = [];
+  const capabilities = Array.isArray(raw?.capabilities) ? raw.capabilities : [];
+  const layouts = raw?.contributes?.layouts;
+  const themes = raw?.contributes?.themes;
+  const hasLayouts = Array.isArray(layouts) && layouts.length > 0;
+  const hasThemes = Array.isArray(themes) && themes.length > 0;
+  if (capabilities.includes("ui:layout") && !hasLayouts) {
+    problems.push('"ui:layout" is declared but contributes.layouts is empty');
+  }
+  if (capabilities.includes("ui:theme") && !hasThemes) {
+    problems.push('"ui:theme" is declared but contributes.themes is empty');
+  }
+  if (hasLayouts) {
+    const entries = ["index.tsx", "index.ts", "index.mjs", "index.js"];
+    const frontend = entries.some((entry) =>
+      fs.existsSync(path.join(cwd, "src", "frontend", entry)),
+    );
+    if (!frontend && raw.frontend === undefined) {
+      problems.push(
+        "contributes.layouts needs a frontend that calls app.registerLayout",
+      );
+    }
+  }
+  return problems;
+}
+
 /** Env vars core sets for everyone, so a plugin need not list them. */
 const CORE_ENV = new Set([
   "DATA_DIR",

packages/plugin-sdk/cli/lib/plugin-dir.mjs

@@ -14,6 +14,17 @@ export function readManifest(cwd) {
 }
 
 /** The first of these that exists, or null. */
+/** Only themes: CSS files and no code, so no source entry is needed. */
+export function isThemeOnly(manifest) {
+  const capabilities = manifest.capabilities ?? [];
+  return (
+    capabilities.length > 0 &&
+    capabilities.every((capability) => capability === "ui:theme") &&
+    Array.isArray(manifest.contributes?.themes) &&
+    manifest.contributes.themes.length > 0
+  );
+}
+
 export function resolveEntry(cwd, candidates) {
   for (const candidate of candidates) {
     const full = path.join(cwd, candidate);

scripts/check-core-plugin-ids.cjs

@@ -34,6 +34,7 @@ const OFFICIAL_IDS = [
   "alerts",
   "automations",
   "classic-layout",
+  "classic-themes",
   "docker",
   "file-manager",
   "fleets",

scripts/plugin-build.test.ts

@@ -35,6 +35,42 @@ function fixturePlugin(): string {
 }
 
 describe("termix-plugin build", () => {
+  it("builds a theme only plugin with an empty backend and no source", async () => {
+    vi.spyOn(console, "log").mockImplementation(() => {});
+    const dir = fs.mkdtempSync(path.join(os.tmpdir(), "termix-build-"));
+    cleanups.push(() => fs.rmSync(dir, { recursive: true, force: true }));
+    fs.writeFileSync(
+      path.join(dir, "manifest.json"),
+      JSON.stringify({
+        id: "theme-fixture",
+        capabilities: ["ui:theme"],
+        contributes: { themes: [{ id: "paper" }] },
+      }),
+    );
+
+    await build({ cwd: dir });
+
+    expect(
+      fs.readFileSync(path.join(dir, "dist", "backend.js"), "utf8"),
+    ).toContain("export function activate()");
+    expect(fs.existsSync(path.join(dir, "dist", "frontend.js"))).toBe(false);
+  });
+
+  it("still needs a backend entry once a plugin holds more than themes", async () => {
+    const dir = fs.mkdtempSync(path.join(os.tmpdir(), "termix-build-"));
+    cleanups.push(() => fs.rmSync(dir, { recursive: true, force: true }));
+    fs.writeFileSync(
+      path.join(dir, "manifest.json"),
+      JSON.stringify({
+        id: "mixed-fixture",
+        capabilities: ["ui:theme", "ui:layout"],
+        contributes: { themes: [{ id: "paper" }] },
+      }),
+    );
+
+    await expect(build({ cwd: dir })).rejects.toThrow("no backend entry");
+  });
+
   it("marks dist as ESM so Node loads backend.js without reparsing", async () => {
     vi.spyOn(console, "log").mockImplementation(() => {});
     const dir = fixturePlugin();

scripts/plugin-validate.test.ts

@@ -99,3 +99,48 @@ describe("termix-plugin validate themes", () => {
     expect(output).not.toContain("theme paper");
   });
 });
+
+describe("termix-plugin validate layouts and capabilities", () => {
+  function withManifest(extra: Record<string, unknown>) {
+    const root = plugin([]);
+    fs.writeFileSync(
+      path.join(root, "manifest.json"),
+      JSON.stringify({ id: "fixture", version: "1.0.0", ...extra }),
+    );
+    return root;
+  }
+
+  it("flags ui:theme with no themes and ui:layout with no layouts", async () => {
+    const output = await problems(
+      withManifest({ capabilities: ["ui:theme", "ui:layout"] }),
+    );
+    expect(output).toContain(
+      '"ui:theme" is declared but contributes.themes is empty',
+    );
+    expect(output).toContain(
+      '"ui:layout" is declared but contributes.layouts is empty',
+    );
+  });
+
+  it("flags a layout plugin with no frontend source", async () => {
+    const output = await problems(
+      withManifest({
+        capabilities: ["ui:layout"],
+        contributes: { layouts: [{ id: "wide", label: "Wide" }] },
+      }),
+    );
+    expect(output).toContain("contributes.layouts needs a frontend");
+  });
+
+  it("accepts a layout plugin that has a frontend entry", async () => {
+    const root = withManifest({
+      capabilities: ["ui:layout"],
+      contributes: { layouts: [{ id: "wide", label: "Wide" }] },
+    });
+    fs.mkdirSync(path.join(root, "src", "frontend"), { recursive: true });
+    fs.writeFileSync(path.join(root, "src", "frontend", "index.tsx"), "");
+    const output = await problems(root);
+    expect(output).not.toContain("contributes.layouts needs a frontend");
+    expect(output).not.toContain("is declared but");
+  });
+});

src/ui/components/theme-provider.tsx

@@ -1,7 +1,12 @@
 /* eslint-disable react-refresh/only-export-components */
 import { createContext, useContext, useEffect, useState } from "react";
 import type { ThemeId } from "@/types/ui-types";
-import { SYSTEM_THEME, getTheme, useThemes } from "@/look/theme-registry";
+import {
+  SYSTEM_THEME,
+  effectiveThemeId,
+  getTheme,
+  useThemes,
+} from "@/look/theme-registry";
 import { applyThemeCss } from "@/look/theme-css";
 
 type ThemeProviderProps = {
@@ -41,7 +46,9 @@ export function ThemeProvider({
   // Plugin themes arrive after login; the class and CSS follow them.
   const themes = useThemes();
 
-  const activeTheme = previewTheme ?? theme;
+  // A saved theme whose plugin is gone shows as System.
+  const shownTheme = effectiveThemeId(theme);
+  const activeTheme = previewTheme ?? shownTheme;
 
   useEffect(() => {
     const root = window.document.documentElement;
@@ -60,7 +67,7 @@ export function ThemeProvider({
   }, [activeTheme, themes]);
 
   const value = {
-    theme,
+    theme: shownTheme,
     setTheme: (theme: ThemeId, persist = true) => {
       if (persist) localStorage.setItem(storageKey, theme);
       setTheme(theme);

src/ui/index.css

@@ -136,288 +136,6 @@
   --terminal-bg: #0c0d0b;
 }
 
-/* ── Dracula ────────────────────────────────────────────────── */
-.dracula {
-  --background: #282a36;
-  --foreground: #f8f8f2;
-  --card: #2d303d;
-  --card-foreground: #f8f8f2;
-  --popover: #2d303d;
-  --popover-foreground: #f8f8f2;
-  --primary: #8be9fd;
-  --primary-foreground: #282a36;
-  --secondary: #50536b;
-  --secondary-foreground: #f8f8f2;
-  --surface: #2d303d;
-  --surface-dim: #21222c;
-  --muted: #50536b;
-  --muted-foreground: #a8b3d9;
-  --accent: #5a5e7a;
-  --accent-foreground: #f8f8f2;
-  --destructive: #ff5555;
-  --border: rgba(168, 179, 217, 0.18);
-  --input: rgba(168, 179, 217, 0.14);
-  --ring: #8be9fd;
-  --chart-1: #ff79c6;
-  --chart-2: #8be9fd;
-  --chart-3: #50fa7b;
-  --chart-4: #ffb86c;
-  --chart-5: #bd93f9;
-  --radius: 0.625rem;
-  --sidebar: #21222c;
-  --sidebar-foreground: #f8f8f2;
-  --sidebar-primary: #8be9fd;
-  --sidebar-primary-foreground: #282a36;
-  --sidebar-accent: #5a5e7a;
-  --sidebar-accent-foreground: #f8f8f2;
-  --sidebar-border: rgba(168, 179, 217, 0.18);
-  --sidebar-ring: #8be9fd;
-  --warning: #f1fa8c;
-  --terminal-bg: #282a36;
-}
-
-/* ── Catppuccin Mocha ───────────────────────────────────────── */
-.catppuccin {
-  --background: #1e1e2e;
-  --foreground: #cdd6f4;
-  --card: #202235;
-  --card-foreground: #cdd6f4;
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-  --popover-foreground: #cdd6f4;
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-  --primary-foreground: #1e1e2e;
-  --secondary: #3b3d52;
-  --secondary-foreground: #cdd6f4;
-  --surface: #202235;
-  --surface-dim: #181825;
-  --muted: #3b3d52;
-  --muted-foreground: #b8c0e0;
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-  --destructive: #f38ba8;
-  --border: rgba(186, 194, 222, 0.18);
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-  --chart-4: #fab387;
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-  --radius: 0.625rem;
-  --sidebar: #181825;
-  --sidebar-foreground: #cdd6f4;
-  --sidebar-primary: #89b4fa;
-  --sidebar-primary-foreground: #1e1e2e;
-  --sidebar-accent: #45475a;
-  --sidebar-accent-foreground: #cdd6f4;
-  --sidebar-border: rgba(186, 194, 222, 0.18);
-  --sidebar-ring: #89b4fa;
-  --warning: #f9e2af;
-  --terminal-bg: #1e1e2e;
-}
-
-/* ── Nord ───────────────────────────────────────────────────── */
-.nord {
-  --background: #2e3440;
-  --foreground: #eceff4;
-  --card: #353c4a;
-  --card-foreground: #eceff4;
-  --popover: #353c4a;
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-  --sidebar-foreground: #eceff4;
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-  --sidebar-border: rgba(180, 192, 212, 0.18);
-  --sidebar-ring: #88c0d0;
-  --warning: #ebcb8b;
-  --terminal-bg: #2e3440;
-}
-
-/* ── Solarized Dark ─────────────────────────────────────────── */
-.solarized {
-  --background: #002b36;
-  --foreground: #b7c4c4;
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-  --sidebar-border: rgba(159, 179, 179, 0.2);
-  --sidebar-ring: #268bd2;
-  --warning: #b58900;
-  --terminal-bg: #002b36;
-}
-
-/* ── Tokyo Night ────────────────────────────────────────────── */
-
-.tokyo-night {
-  --background: #1a1b26;
-  --foreground: #c0caf5;
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-  --sidebar-accent-foreground: #c0caf5;
-  --sidebar-border: rgba(139, 147, 189, 0.2);
-  --sidebar-ring: #7aa2f7;
-  --warning: #e0af68;
-  --terminal-bg: #1a1b26;
-}
-
-/* ── One Dark ───────────────────────────────────────────────── */
-.one-dark {
-  --background: #282c34;
-  --foreground: #abb2bf;
-  --card: #2f343d;
-  --card-foreground: #abb2bf;
-  --popover: #2f343d;
-  --popover-foreground: #abb2bf;
-  --primary: #61afef;
-  --primary-foreground: #282c34;
-  --secondary: #3a404b;
-  --secondary-foreground: #abb2bf;
-  --surface: #2f343d;
-  --surface-dim: #21252b;
-  --muted: #3a404b;
-  --muted-foreground: #9aa3b2;
-  --accent: #424957;
-  --accent-foreground: #abb2bf;
-  --destructive: #e06c75;
-  --border: rgba(154, 163, 178, 0.18);
-  --input: rgba(154, 163, 178, 0.14);
-  --ring: #61afef;
-  --chart-1: #e06c75;
-  --chart-2: #56b6c2;
-  --chart-3: #98c379;
-  --chart-4: #e5c07b;
-  --chart-5: #c678dd;
-  --radius: 0.625rem;
-  --sidebar: #21252b;
-  --sidebar-foreground: #abb2bf;
-  --sidebar-primary: #61afef;
-  --sidebar-primary-foreground: #282c34;
-  --sidebar-accent: #424957;
-  --sidebar-accent-foreground: #abb2bf;
-  --sidebar-border: rgba(154, 163, 178, 0.18);
-  --sidebar-ring: #61afef;
-  --warning: #e5c07b;
-  --terminal-bg: #282c34;
-}
-
-/* ── Gruvbox Dark ───────────────────────────────────────────── */
-
-.gruvbox {
-  --background: #282828;
-  --foreground: #ebdbb2;
-  --card: #32302f;
-  --card-foreground: #ebdbb2;
-  --popover: #32302f;
-  --popover-foreground: #ebdbb2;
-  --primary: #fabd2f;
-  --primary-foreground: #282828;
-  --secondary: #45403d;
-  --secondary-foreground: #ebdbb2;
-  --surface: #32302f;
-  --surface-dim: #1d2021;
-  --muted: #45403d;
-  --muted-foreground: #c4b59d;
-  --accent: #504945;
-  --accent-foreground: #ebdbb2;
-  --destructive: #fb4934;
-  --border: rgba(196, 181, 157, 0.18);
-  --input: rgba(196, 181, 157, 0.14);
-  --ring: #fabd2f;
-  --chart-1: #fb4934;
-  --chart-2: #8ec07c;
-  --chart-3: #b8bb26;
-  --chart-4: #fabd2f;
-  --chart-5: #d3869b;
-  --radius: 0.625rem;
-  --sidebar: #1d2021;
-  --sidebar-foreground: #ebdbb2;
-  --sidebar-primary: #fabd2f;
-  --sidebar-primary-foreground: #282828;
-  --sidebar-accent: #504945;
-  --sidebar-accent-foreground: #ebdbb2;
-  --sidebar-border: rgba(196, 181, 157, 0.18);
-  --sidebar-ring: #fabd2f;
-  --warning: #fabd2f;
-  --terminal-bg: #282828;
-}
-
 @layer base {
   * {
     /* Tailwind v4 defaults border-color to currentColor, so any bare "border"

src/ui/locales/en.json

@@ -1115,14 +1115,7 @@
         "colorPickerTooltip": "Open color picker",
         "themeSystem": "System",
         "themeLight": "Light",
-        "themeDark": "Dark",
-        "themeDracula": "Dracula",
-        "themeCatppuccin": "Catppuccin",
-        "themeNord": "Nord",
-        "themeSolarized": "Solarized",
-        "themeTokyoNight": "Tokyo Night",
-        "themeOneDark": "One Dark",
-        "themeGruvbox": "Gruvbox"
+        "themeDark": "Dark"
       }
     }
   },

src/ui/look/theme-registry.ts

@@ -24,8 +24,9 @@ export interface ThemeDef {
 }
 
 /**
- * Themes core ships, with their tokens in index.css. A plugin theme with the
- * same id takes the built-in's place while it is installed.
+ * The two themes core keeps as a fallback, with their tokens in index.css.
+ * The rest come from theme plugins. A plugin theme with the same id takes
+ * the built-in's place while it is installed.
  */
 export const BUILTIN_THEMES: readonly ThemeDef[] = [
   {
@@ -40,48 +41,6 @@ export const BUILTIN_THEMES: readonly ThemeDef[] = [
     mode: "dark",
     swatch: { background: "#1a1c22", panel: "#25272e", text: "#e5e7eb" },
   },
-  {
-    id: "dracula",
-    label: "newUi.sidebar.userProfile.themeDracula",
-    mode: "dark",
-    swatch: { background: "#282a36", panel: "#44475a", text: "#f8f8f2" },
-  },
-  {
-    id: "catppuccin",
-    label: "newUi.sidebar.userProfile.themeCatppuccin",
-    mode: "dark",
-    swatch: { background: "#1e1e2e", panel: "#313244", text: "#cdd6f4" },
-  },
-  {
-    id: "nord",
-    label: "newUi.sidebar.userProfile.themeNord",
-    mode: "dark",
-    swatch: { background: "#2e3440", panel: "#3b4252", text: "#eceff4" },
-  },
-  {
-    id: "solarized",
-    label: "newUi.sidebar.userProfile.themeSolarized",
-    mode: "dark",
-    swatch: { background: "#002b36", panel: "#073642", text: "#93a1a1" },
-  },
-  {
-    id: "tokyo-night",
-    label: "newUi.sidebar.userProfile.themeTokyoNight",
-    mode: "dark",
-    swatch: { background: "#1a1b26", panel: "#24283b", text: "#c0caf5" },
-  },
-  {
-    id: "one-dark",
-    label: "newUi.sidebar.userProfile.themeOneDark",
-    mode: "dark",
-    swatch: { background: "#282c34", panel: "#21252b", text: "#abb2bf" },
-  },
-  {
-    id: "gruvbox",
-    label: "newUi.sidebar.userProfile.themeGruvbox",
-    mode: "dark",
-    swatch: { background: "#282828", panel: "#3c3836", text: "#ebdbb2" },
-  },
 ];
 
 const builtins = new Map(BUILTIN_THEMES.map((theme) => [theme.id, theme]));
@@ -96,15 +55,15 @@ function emit() {
   for (const listener of listeners) listener();
 }
 
-/** Built-ins in their order, a plugin theme in a built-in's place, then the rest. */
+/** Built-ins in their order, a plugin theme in a built-in's place, then the rest as declared. */
 export function listThemes(): ThemeDef[] {
   if (!snapshot) {
     const replaced = BUILTIN_THEMES.map(
       (theme) => pluginThemes.get(theme.id) ?? theme,
     );
-    const extra = [...pluginThemes.values()]
-      .filter((theme) => !builtins.has(theme.id))
-      .sort((a, b) => a.id.localeCompare(b.id));
+    const extra = [...pluginThemes.values()].filter(
+      (theme) => !builtins.has(theme.id),
+    );
     snapshot = [...replaced, ...extra];
   }
   return snapshot;
@@ -154,7 +113,16 @@ export function themeMode(id: string): "light" | "dark" {
       ? "dark"
       : "light";
   }
-  return getTheme(id)?.mode ?? "dark";
+  const theme = getTheme(id);
+  if (theme) return theme.mode;
+  // A theme that went away follows the OS, once the plugins have said so.
+  return pluginThemesKnown ? themeMode(SYSTEM_THEME) : "dark";
+}
+
+/** The theme to show for a saved id: itself, or System when it is gone. */
+export function effectiveThemeId(id: string): string {
+  if (id === SYSTEM_THEME || getTheme(id) || !pluginThemesKnown) return id;
+  return SYSTEM_THEME;
 }
 
 export function themeLabel(theme: ThemeDef, t: TFunction): string {

src/ui/tests/components/theme-provider.test.tsx

@@ -75,4 +75,36 @@ describe("ThemeProvider", () => {
     expect(classes()).toEqual(["dark"]);
     expect(document.getElementById("termix-theme-css")).toBeNull();
   });
+
+  it("shows system when the saved theme's plugin is gone", () => {
+    localStorage.setItem("test-theme", "nord");
+    mount();
+    // Plugins not read yet, so the saved theme is kept.
+    expect(classes()).toEqual(["nord"]);
+    act(() => setPluginThemes([]));
+    expect(api!.theme).toBe("system");
+    expect(classes()).toHaveLength(1);
+    expect(["light", "dark"]).toContain(classes()[0]);
+    expect(localStorage.getItem("test-theme")).toBe("nord");
+  });
+
+  it("brings the saved theme back when its plugin returns", () => {
+    localStorage.setItem("test-theme", "nord");
+    mount();
+    act(() => setPluginThemes([]));
+    act(() =>
+      setPluginThemes([
+        {
+          id: "nord",
+          label: "theme.nord",
+          mode: "dark",
+          swatch: { background: "#2e3440", panel: "#3b4252", text: "#eceff4" },
+          pluginId: "classic-themes",
+          cssHref: "/plugin-assets/classic-themes/_themes/nord.css?v=1",
+        },
+      ]),
+    );
+    expect(api!.theme).toBe("nord");
+    expect(classes()).toEqual(["nord"]);
+  });
 });

src/ui/tests/look/LookSettings.test.tsx

@@ -60,7 +60,7 @@ describe("LookSettings", () => {
     const [, layoutDefault, themeDefault] = screen.getAllByRole("combobox");
     fireEvent.change(layoutDefault, { target: { value: "fancy" } });
     expect(look.chooseDefaultLook).toHaveBeenCalledWith({ layout: "fancy" });
-    fireEvent.change(themeDefault, { target: { value: "nord" } });
-    expect(look.chooseDefaultLook).toHaveBeenCalledWith({ theme: "nord" });
+    fireEvent.change(themeDefault, { target: { value: "light" } });
+    expect(look.chooseDefaultLook).toHaveBeenCalledWith({ theme: "light" });
   });
 });

src/ui/tests/look/RepairView.test.tsx

@@ -155,9 +155,9 @@ describe("RepairView", () => {
     fireEvent.click(screen.getByText("Classic"));
     expect(look.chooseLayout).toHaveBeenCalledWith("classic");
     fireEvent.click(
-      screen.getAllByTitle("newUi.sidebar.userProfile.themeNord")[0],
+      screen.getAllByTitle("newUi.sidebar.userProfile.themeLight")[0],
     );
-    expect(look.chooseTheme).toHaveBeenCalledWith("nord");
+    expect(look.chooseTheme).toHaveBeenCalledWith("light");
   });
 
   it("resets to the default look", async () => {

src/ui/tests/look/theme-registry.test.ts

@@ -2,65 +2,81 @@ import { afterEach, describe, expect, it } from "vitest";
 import {
   BUILTIN_THEMES,
   arePluginThemesKnown,
+  effectiveThemeId,
   getTheme,
   listThemes,
   resetPluginThemes,
   setPluginThemes,
   themeLabel,
   themeMode,
+  type ThemeDef,
 } from "@/look/theme-registry";
 
 afterEach(() => resetPluginThemes());
 
 const swatch = { background: "#000000", panel: "#111111", text: "#ffffff" };
 
+function pluginTheme(
+  id: string,
+  mode: "light" | "dark" = "dark",
+  pluginId = "more-themes",
+): ThemeDef {
+  return { id, label: `theme.${id}`, mode, swatch, pluginId };
+}
+
 describe("theme registry", () => {
-  it("lists the built-ins in their order", () => {
-    expect(listThemes().map((theme) => theme.id)).toEqual(
-      BUILTIN_THEMES.map((theme) => theme.id),
-    );
+  it("keeps only a light and a dark theme in core", () => {
+    expect(BUILTIN_THEMES.map((theme) => theme.id)).toEqual(["light", "dark"]);
+    expect(listThemes().map((theme) => theme.id)).toEqual(["light", "dark"]);
     expect(arePluginThemesKnown()).toBe(false);
   });
 
-  it("lets a plugin theme take a built-in's place and adds new ones after", () => {
+  it("lets a plugin theme take a built-in's place and adds new ones in the order given", () => {
     setPluginThemes([
       {
-        id: "nord",
-        label: "themes.nord",
-        mode: "dark",
-        swatch,
-        pluginId: "more-themes",
-        cssHref: "/plugin-assets/more-themes/_themes/nord.css",
-      },
-      {
-        id: "paper",
-        label: "Paper",
-        mode: "light",
-        swatch,
-        pluginId: "more-themes",
+        ...pluginTheme("dark"),
+        cssHref: "/plugin-assets/more-themes/_themes/dark.css",
       },
+      pluginTheme("nord"),
+      pluginTheme("dracula"),
+      pluginTheme("paper", "light"),
     ]);
     const ids = listThemes().map((theme) => theme.id);
-    expect(ids.indexOf("nord")).toBe(
-      BUILTIN_THEMES.findIndex((theme) => theme.id === "nord"),
-    );
-    expect(ids[ids.length - 1]).toBe("paper");
-    expect(getTheme("nord")?.pluginId).toBe("more-themes");
+    expect(ids).toEqual(["light", "dark", "nord", "dracula", "paper"]);
+    expect(getTheme("dark")?.pluginId).toBe("more-themes");
     expect(arePluginThemesKnown()).toBe(true);
 
     setPluginThemes([]);
-    expect(getTheme("nord")?.pluginId).toBeUndefined();
+    expect(getTheme("dark")?.pluginId).toBeUndefined();
     expect(getTheme("paper")).toBeUndefined();
+    expect(listThemes().map((theme) => theme.id)).toEqual(["light", "dark"]);
   });
 
   it("reports each theme's mode, following the OS for system", () => {
     expect(themeMode("light")).toBe("light");
-    expect(themeMode("dracula")).toBe("dark");
     expect(["light", "dark"]).toContain(themeMode("system"));
-    setPluginThemes([
-      { id: "paper", label: "Paper", mode: "light", swatch, pluginId: "x" },
-    ]);
+    setPluginThemes([pluginTheme("paper", "light"), pluginTheme("nord")]);
     expect(themeMode("paper")).toBe("light");
+    expect(themeMode("nord")).toBe("dark");
+  });
+
+  it("assumes dark for an unknown theme until the plugins have loaded, then follows the OS", () => {
+    expect(themeMode("nord")).toBe("dark");
+    setPluginThemes([]);
+    expect(["light", "dark"]).toContain(themeMode("nord"));
+    expect(themeMode("nord")).toBe(themeMode("system"));
+  });
+
+  it("falls back to system for a saved theme that no longer exists", () => {
+    // Plugins not read yet: the id may still arrive, so keep it.
+    expect(effectiveThemeId("nord")).toBe("nord");
+    setPluginThemes([pluginTheme("nord")]);
+    expect(effectiveThemeId("nord")).toBe("nord");
+    expect(effectiveThemeId("light")).toBe("light");
+    expect(effectiveThemeId("system")).toBe("system");
+    setPluginThemes([]);
+    expect(effectiveThemeId("nord")).toBe("system");
+    expect(effectiveThemeId("dark")).toBe("dark");
   });
 
   it("translates core labels in core and plugin labels in the plugin", () => {

src/ui/tests/plugin-host/bridge.test.ts

@@ -113,8 +113,9 @@ describe("useTheme", () => {
     );
     act(() => setTheme!("paper"));
     expect(result.current.theme).toBe("light");
+    // Gone themes follow the OS once the plugin list is known.
     act(() => setTheme!("dracula"));
-    expect(result.current.theme).toBe("dark");
+    expect(["light", "dark"]).toContain(result.current.theme);
     resetPluginThemes();
     localStorage.removeItem("bridge-theme");
   });

src/ui/tests/settings/appearance/appearance-controls.test.tsx

@@ -95,17 +95,17 @@ describe("ThemeGrid", () => {
     render(<ThemeGrid value="dark" onChange={onChange} />);
     const buttons = screen.getAllByRole("button");
     expect(buttons).toHaveLength(THEMES.length);
-    fireEvent.click(buttons[THEMES.findIndex((t) => t.id === "gruvbox")]);
-    expect(onChange).toHaveBeenCalledWith("gruvbox");
+    fireEvent.click(buttons[THEMES.findIndex((t) => t.id === "light")]);
+    expect(onChange).toHaveBeenCalledWith("light");
   });
 
   it("previews a theme while it is hovered", () => {
     render(<ThemeGrid value="dark" onChange={vi.fn()} />);
-    const nord =
-      screen.getAllByRole("button")[THEMES.findIndex((t) => t.id === "nord")];
-    fireEvent.mouseEnter(nord);
-    expect(theme.setThemePreview).toHaveBeenLastCalledWith("nord");
-    fireEvent.mouseLeave(nord);
+    const light =
+      screen.getAllByRole("button")[THEMES.findIndex((t) => t.id === "light")];
+    fireEvent.mouseEnter(light);
+    expect(theme.setThemePreview).toHaveBeenLastCalledWith("light");
+    fireEvent.mouseLeave(light);
     expect(theme.setThemePreview).toHaveBeenLastCalledWith(null);
   });
 });