clarify desktop theme picker behavior

desktop/src/features/settings/ui/SettingsPanels.tsx

@@ -124,7 +124,8 @@ function ThemeSettingsCard() {
       <div className="mb-3 min-w-0">
         <h2 className="text-sm font-semibold tracking-tight">Appearance</h2>
         <p className="text-sm text-muted-foreground">
-          Choose a theme for Sprout. Light and dark mode is auto-detected.
+          Pick the theme Sprout should use. Your selection stays active until
+          you choose another one.
         </p>
       </div>
 

desktop/src/shared/theme/ThemeProvider.tsx

@@ -10,6 +10,7 @@ import {
 import { createThemeVars, hexToHsl } from "./adaptive-theme";
 import {
   SYNTAX_THEMES,
+  isLightTheme,
   type SyntaxThemeName,
   extractThemeInfo,
   loadThemeData,
@@ -85,6 +86,12 @@ function applyAccentColor(hex: string) {
   root.style.setProperty("--sidebar-primary-foreground", fgHsl);
 }
 
+function applyThemeClass(themeName: SyntaxThemeName) {
+  const root = document.documentElement;
+  root.classList.remove("light", "dark");
+  root.classList.add(isLightTheme(themeName) ? "light" : "dark");
+}
+
 /** Apply cached CSS vars synchronously to prevent FOUC. */
 function applyCachedVars(): string | null {
   try {
@@ -146,7 +153,10 @@ export function ThemeProvider({
   // Apply cached vars synchronously before first render
   const [themeName, setThemeName] = useState<string>(() => {
     const cached = applyCachedVars();
-    return cached ?? readStoredTheme(defaultTheme);
+    if (cached) return cached;
+    const storedTheme = readStoredTheme(defaultTheme);
+    applyThemeClass(storedTheme);
+    return storedTheme;
   });
   const [isDark, setIsDark] = useState<boolean>(() => {
     return document.documentElement.classList.contains("dark");

desktop/tests/e2e/profile.spec.ts

@@ -290,7 +290,7 @@ test("opens settings with the keyboard shortcut and updates theme", async ({
   await expect(page.getByTestId("settings-nav-appearance")).toBeVisible();
   await page.getByTestId("settings-nav-appearance").click();
 
-  // Default theme is catppuccin-macchiato (dark)
+  // Default theme is houston (dark)
   await expect
     .poll(() =>
       page.evaluate(() => document.documentElement.classList.contains("dark")),
@@ -306,27 +306,37 @@ test("opens settings with the keyboard shortcut and updates theme", async ({
     )
     .toBe(true);
 
+  await expect
+    .poll(() => page.evaluate(() => localStorage.getItem("sprout-theme")))
+    .toBe("github-light");
+
+  const primaryBeforeAccent = await page.evaluate(() =>
+    document.documentElement.style.getPropertyValue("--primary").trim(),
+  );
+  expect(primaryBeforeAccent).toBeTruthy();
+
+  // Accent choice should persist across later theme switches.
+  await page.getByTestId("accent-color-red").click();
+
   await expect
     .poll(() =>
-      page.evaluate(() => document.documentElement.classList.contains("dark")),
+      page.evaluate(() => localStorage.getItem("sprout-accent-color")),
     )
-    .toBe(false);
+    .toBe("#ef4444");
 
-  // CSS variables are set on the root element (the real theming mechanism)
   await expect
     .poll(() =>
       page.evaluate(() =>
-        document.documentElement.style.getPropertyValue("--background").trim(),
+        document.documentElement.style.getPropertyValue("--primary").trim(),
       ),
     )
-    .toBeTruthy();
+    .not.toBe(primaryBeforeAccent);
 
-  // Theme name persists in localStorage
-  await expect
-    .poll(() => page.evaluate(() => localStorage.getItem("sprout-theme")))
-    .toBe("github-light");
+  const redAccent = await page.evaluate(() =>
+    document.documentElement.style.getPropertyValue("--primary").trim(),
+  );
+  expect(redAccent).toBeTruthy();
 
-  // Switch back to a dark theme — verifies light→dark transition
   await page.getByTestId("theme-option-dracula").click();
 
   await expect
@@ -339,6 +349,14 @@ test("opens settings with the keyboard shortcut and updates theme", async ({
     .poll(() => page.evaluate(() => localStorage.getItem("sprout-theme")))
     .toBe("dracula");
 
+  await expect
+    .poll(() =>
+      page.evaluate(() =>
+        document.documentElement.style.getPropertyValue("--primary").trim(),
+      ),
+    )
+    .toBe(redAccent);
+
   // Close settings with keyboard shortcut
   await page.keyboard.press(
     process.platform === "darwin" ? "Meta+," : "Control+,",