diff --git a/apps/desktop/src/app/command-palette/marketplace-theme-page.tsx b/apps/desktop/src/app/command-palette/marketplace-theme-page.tsx
index eb175fdcb72..6766b2dae30 100644
--- a/apps/desktop/src/app/command-palette/marketplace-theme-page.tsx
+++ b/apps/desktop/src/app/command-palette/marketplace-theme-page.tsx
@@ -8,6 +8,7 @@
  * user can grab several.
  */
 
+import { useStore } from '@nanostores/react'
 import { useQuery } from '@tanstack/react-query'
 import { useEffect, useState } from 'react'
 
@@ -18,6 +19,7 @@ import { triggerHaptic } from '@/lib/haptics'
 import { Check, Download, Loader2, Palette } from '@/lib/icons'
 import { cn } from '@/lib/utils'
 import { installVscodeThemeFromMarketplace } from '@/themes/install'
+import { $marketplaceInstalls } from '@/themes/user-themes'
 
 const compactNumber = new Intl.NumberFormat(undefined, { notation: 'compact', maximumFractionDigits: 1 })
 
@@ -43,8 +45,8 @@ export function MarketplaceThemePage({ search, onPickTheme }: MarketplaceThemePa
   const { t } = useI18n()
   const copy = t.commandCenter.installTheme
   const debouncedSearch = useDebounced(search.trim(), 300)
+  const installs = useStore($marketplaceInstalls)
   const [installingId, setInstallingId] = useState<string | null>(null)
-  const [installed, setInstalled] = useState<Record<string, true>>({})
   const [installError, setInstallError] = useState<string | null>(null)
 
   const query = useQuery({
@@ -53,6 +55,20 @@ export function MarketplaceThemePage({ search, onPickTheme }: MarketplaceThemePa
     staleTime: 5 * 60 * 1000
   })
 
+  // Already installed → just re-activate it; never re-download what we have.
+  const select = (item: DesktopMarketplaceSearchItem) => {
+    const owned = installs.get(item.extensionId)
+
+    if (owned) {
+      triggerHaptic('crisp')
+      onPickTheme(owned.name)
+
+      return
+    }
+
+    void install(item)
+  }
+
   const install = async (item: DesktopMarketplaceSearchItem) => {
     if (installingId) {
       return
@@ -65,7 +81,6 @@ export function MarketplaceThemePage({ search, onPickTheme }: MarketplaceThemePa
       const theme = await installVscodeThemeFromMarketplace(item.extensionId)
 
       triggerHaptic('crisp')
-      setInstalled(prev => ({ ...prev, [item.extensionId]: true }))
       onPickTheme(theme.name)
     } catch (error) {
       setInstallError(error instanceof Error ? error.message : copy.error)
@@ -93,7 +108,7 @@ export function MarketplaceThemePage({ search, onPickTheme }: MarketplaceThemePa
       {installError && <p className="px-2 pb-1 pt-1.5 text-[0.6875rem] text-(--ui-red)">{installError}</p>}
       {results.map(item => {
         const busy = installingId === item.extensionId
-        const done = installed[item.extensionId]
+        const done = installs.has(item.extensionId)
 
         return (
           <button
@@ -104,7 +119,7 @@ export function MarketplaceThemePage({ search, onPickTheme }: MarketplaceThemePa
             )}
             disabled={Boolean(installingId) && !busy}
             key={item.extensionId}
-            onClick={() => void install(item)}
+            onClick={() => select(item)}
             onMouseDown={event => event.preventDefault()}
             role="option"
             type="button"
diff --git a/apps/desktop/src/app/settings/appearance-settings.tsx b/apps/desktop/src/app/settings/appearance-settings.tsx
index ffa41c5af4e..f9fbc546224 100644
--- a/apps/desktop/src/app/settings/appearance-settings.tsx
+++ b/apps/desktop/src/app/settings/appearance-settings.tsx
@@ -17,7 +17,8 @@ import { $toolViewMode, setToolViewMode } from '@/store/tool-view'
 import { $translucency, setTranslucency } from '@/store/translucency'
 import { getBaseColors, useTheme } from '@/themes/context'
 import { installVscodeThemeFromMarketplace } from '@/themes/install'
-import { isUserTheme, removeUserTheme } from '@/themes/user-themes'
+import type { DesktopTheme } from '@/themes/types'
+import { $marketplaceInstalls, isUserTheme, removeUserTheme } from '@/themes/user-themes'
 
 import { MODE_OPTIONS } from './constants'
 import { PetSettings } from './pet-settings'
@@ -82,18 +83,17 @@ const compactNumber = new Intl.NumberFormat(undefined, { notation: 'compact', ma
  */
 function MarketplaceThemeResults({
   query,
-  installedExtIds,
+  installs,
   onInstalled
 }: {
   query: string
-  installedExtIds: Set<string>
+  installs: ReadonlyMap<string, DesktopTheme>
   onInstalled: (name: string) => void
 }) {
   const { t } = useI18n()
   const copy = t.commandCenter.installTheme
   const debounced = useDebounced(query.trim(), 300)
   const [installingId, setInstallingId] = useState<string | null>(null)
-  const [installedHere, setInstalledHere] = useState<Record<string, true>>({})
   const [error, setError] = useState<string | null>(null)
 
   const search = useQuery({
@@ -103,6 +103,20 @@ function MarketplaceThemeResults({
     staleTime: 5 * 60 * 1000
   })
 
+  // Already installed → just re-activate it; never re-download what we have.
+  const select = (item: DesktopMarketplaceSearchItem) => {
+    const owned = installs.get(item.extensionId)
+
+    if (owned) {
+      triggerHaptic('crisp')
+      onInstalled(owned.name)
+
+      return
+    }
+
+    void install(item)
+  }
+
   const install = async (item: DesktopMarketplaceSearchItem) => {
     if (installingId) {
       return
@@ -115,7 +129,6 @@ function MarketplaceThemeResults({
       const theme = await installVscodeThemeFromMarketplace(item.extensionId)
 
       triggerHaptic('crisp')
-      setInstalledHere(prev => ({ ...prev, [item.extensionId]: true }))
       onInstalled(theme.name)
     } catch (e) {
       setError(e instanceof Error ? e.message : copy.error)
@@ -173,7 +186,7 @@ function MarketplaceThemeResults({
       <div className="grid gap-2 sm:grid-cols-2">
         {results.map(item => {
           const busy = installingId === item.extensionId
-          const done = installedHere[item.extensionId] || installedExtIds.has(item.extensionId)
+          const done = installs.has(item.extensionId)
 
           return (
             <button
@@ -183,7 +196,7 @@ function MarketplaceThemeResults({
               )}
               disabled={Boolean(installingId) && !busy}
               key={item.extensionId}
-              onClick={() => void install(item)}
+              onClick={() => select(item)}
               type="button"
             >
               <Palette className="size-4 shrink-0 text-(--ui-text-tertiary)" />
@@ -220,6 +233,7 @@ export function AppearanceSettings() {
   const embedMode = useStore($embedMode)
   const embedAllowed = useStore($embedAllowed)
   const translucency = useStore($translucency)
+  const installs = useStore($marketplaceInstalls)
   const profiles = useStore($profiles)
   const activeProfileKey = normalizeProfileKey(useStore($activeGatewayProfile))
   const a = t.settings.appearance
@@ -242,20 +256,6 @@ export function AppearanceSettings() {
     // Active theme first; stable sort keeps the rest in their original order.
     .sort((a, b) => Number(b.name === themeName) - Number(a.name === themeName))
 
-  // Marketplace imports describe themselves as "VS Code · <publisher.extension>";
-  // pull those ids back out so search results already imported show as installed.
-  const MARKETPLACE_DESC_PREFIX = 'VS Code · '
-
-  const installedExtIds = new Set(
-    availableThemes
-      .map(theme =>
-        theme.description.startsWith(MARKETPLACE_DESC_PREFIX)
-          ? theme.description.slice(MARKETPLACE_DESC_PREFIX.length)
-          : ''
-      )
-      .filter(Boolean)
-  )
-
   // Themes save per profile. Surface that only when the user actually has more
   // than one profile (single-profile installs never see the distinction).
   const showProfileNote = profiles.length > 1
@@ -365,11 +365,7 @@ export function AppearanceSettings() {
                       })}
                     </div>
                   )}
-                  <MarketplaceThemeResults
-                    installedExtIds={installedExtIds}
-                    onInstalled={name => setTheme(name)}
-                    query={query}
-                  />
+                  <MarketplaceThemeResults installs={installs} onInstalled={name => setTheme(name)} query={query} />
                 </div>
                 {showProfileNote && (
                   <p className="mt-3 text-[length:var(--conversation-caption-font-size)] leading-(--conversation-caption-line-height) text-(--ui-text-tertiary)">
diff --git a/apps/desktop/src/themes/user-themes.test.ts b/apps/desktop/src/themes/user-themes.test.ts
index 53db3ce1d25..ca1f59c702b 100644
--- a/apps/desktop/src/themes/user-themes.test.ts
+++ b/apps/desktop/src/themes/user-themes.test.ts
@@ -1,15 +1,27 @@
 import { beforeEach, describe, expect, it } from 'vitest'
 
 import { BUILTIN_THEMES, DEFAULT_SKIN_NAME } from './presets'
-import { $userThemes, installUserTheme, isUserTheme, listAllThemes, removeUserTheme, resolveTheme } from './user-themes'
+import {
+  $marketplaceInstalls,
+  $userThemes,
+  installUserTheme,
+  isUserTheme,
+  listAllThemes,
+  marketplaceIdOf,
+  removeUserTheme,
+  resolveTheme
+} from './user-themes'
 import { convertVscodeColorTheme } from './vscode'
 
-const makeTheme = (label: string) =>
-  convertVscodeColorTheme({
-    name: label,
-    type: 'dark',
-    colors: { 'editor.background': '#101014', 'editor.foreground': '#fafafa', focusBorder: '#7aa2f7' }
-  }).theme
+const makeTheme = (label: string, source?: string) =>
+  convertVscodeColorTheme(
+    {
+      name: label,
+      type: 'dark',
+      colors: { 'editor.background': '#101014', 'editor.foreground': '#fafafa', focusBorder: '#7aa2f7' }
+    },
+    source ? { source } : undefined
+  ).theme
 
 describe('user theme registry', () => {
   beforeEach(() => {
@@ -61,3 +73,33 @@ describe('user theme registry', () => {
     expect(() => installUserTheme(broken)).toThrow(/colors/)
   })
 })
+
+describe('marketplace install tracking', () => {
+  beforeEach(() => {
+    window.localStorage.clear()
+    $userThemes.set({})
+  })
+
+  it('recovers the extension id only from Marketplace-sourced themes', () => {
+    expect(marketplaceIdOf(makeTheme('Dracula', 'dracula-theme.theme-dracula'))).toBe('dracula-theme.theme-dracula')
+    // A pasted (non-Marketplace) import has no extension id to report.
+    expect(marketplaceIdOf(makeTheme('Pasted'))).toBeNull()
+  })
+
+  it('maps installed Marketplace extension ids to their theme, reactively', () => {
+    expect($marketplaceInstalls.get().size).toBe(0)
+
+    const theme = installUserTheme(makeTheme('Dracula', 'dracula-theme.theme-dracula'))
+    const map = $marketplaceInstalls.get()
+
+    expect(map.get('dracula-theme.theme-dracula')).toEqual(theme)
+
+    removeUserTheme(theme.name)
+    expect($marketplaceInstalls.get().has('dracula-theme.theme-dracula')).toBe(false)
+  })
+
+  it('omits pasted imports (no extension id) from the map', () => {
+    installUserTheme(makeTheme('Pasted'))
+    expect($marketplaceInstalls.get().size).toBe(0)
+  })
+})
diff --git a/apps/desktop/src/themes/user-themes.ts b/apps/desktop/src/themes/user-themes.ts
index cb2cd34b384..c4bba521065 100644
--- a/apps/desktop/src/themes/user-themes.ts
+++ b/apps/desktop/src/themes/user-themes.ts
@@ -10,13 +10,18 @@
  * React mounts) can resolve a user theme synchronously, same as built-ins.
  */
 
-import { atom } from 'nanostores'
+import { atom, computed } from 'nanostores'
 
 import { BUILTIN_THEMES } from './presets'
 import type { DesktopTheme, DesktopThemeColors } from './types'
 
 const USER_THEMES_KEY = 'hermes-desktop-user-themes-v1'
 
+// Marketplace imports stamp their description "VS Code · <publisher.extension>"
+// (see `convertVscodeColorTheme`). This is the one place that convention is read
+// back out, so every install surface can tell what's already installed.
+const MARKETPLACE_DESC_PREFIX = 'VS Code · '
+
 // The minimal set of color keys a stored theme must carry to be usable. We keep
 // this loose — `applyTheme` tolerates missing optionals via fallbacks — but a
 // theme with no background/foreground/primary is junk and gets dropped.
@@ -111,6 +116,32 @@ export function removeUserTheme(name: string): void {
 
 export const isUserTheme = (name: string): boolean => Boolean($userThemes.get()[name])
 
+/** The Marketplace extension id an installed theme came from, or null. */
+export function marketplaceIdOf(theme: DesktopTheme): string | null {
+  return theme.description.startsWith(MARKETPLACE_DESC_PREFIX)
+    ? theme.description.slice(MARKETPLACE_DESC_PREFIX.length)
+    : null
+}
+
+/**
+ * Reactive `extensionId → installed theme` map, so the install UIs can mark
+ * Marketplace rows you already have (and re-activate them without re-downloading)
+ * from one memoized source instead of re-deriving the set on every render.
+ */
+export const $marketplaceInstalls = computed($userThemes, themes => {
+  const map = new Map<string, DesktopTheme>()
+
+  for (const theme of Object.values(themes)) {
+    const id = marketplaceIdOf(theme)
+
+    if (id) {
+      map.set(id, theme)
+    }
+  }
+
+  return map
+})
+
 /** Resolve a theme by name across the merged registry (built-in + user). */
 export function resolveTheme(name: string): DesktopTheme | undefined {
   return BUILTIN_THEMES[name] ?? $userThemes.get()[name]