fix(tui): stop writing kv.json on every theme preview keystroke

packages/opencode/src/cli/cmd/tui/component/dialog-theme-list.tsx

@@ -17,7 +17,7 @@ export function DialogThemeList() {
   const initial = theme.selected
 
   onCleanup(() => {
-    if (!confirmed) theme.set(initial)
+    if (!confirmed) theme.preview(initial)
   })
 
   return (
@@ -26,7 +26,7 @@ export function DialogThemeList() {
       options={options}
       current={initial}
       onMove={(opt) => {
-        theme.set(opt.value)
+        theme.preview(opt.value)
       }}
       onSelect={(opt) => {
         theme.set(opt.value)
@@ -38,12 +38,12 @@ export function DialogThemeList() {
       }}
       onFilter={(query) => {
         if (query.length === 0) {
-          theme.set(initial)
+          theme.preview(initial)
           return
         }
 
         const first = ref.filtered[0]
-        if (first) theme.set(first.value)
+        if (first) theme.preview(first.value)
       }}
     />
   )

packages/opencode/src/cli/cmd/tui/context/theme.tsx

@@ -478,6 +478,11 @@ export const { use: useTheme, provider: ThemeProvider } = createSimpleContext({
         kv.set("theme", theme)
         return true
       },
+      preview(theme: string) {
+        if (!hasTheme(theme)) return false
+        setStore("active", theme)
+        return true
+      },
       get ready() {
         return store.ready
       },

packages/opencode/test/fixture/tui-plugin.ts

@@ -109,6 +109,7 @@ type Opts = {
     selected?: string
     has?: HostPluginApi["theme"]["has"]
     set?: HostPluginApi["theme"]["set"]
+    preview?: HostPluginApi["theme"]["preview"]
     install?: HostPluginApi["theme"]["install"]
     mode?: HostPluginApi["theme"]["mode"]
     ready?: boolean
@@ -149,6 +150,13 @@ export function createTuiPluginApi(opts: Opts = {}): HostPluginApi {
       selected = name
       return true
     })
+  const preview =
+    opts.theme?.preview ??
+    ((name: string) => {
+      if (!has(name)) return false
+      selected = name
+      return true
+    })
   const renderer: CliRenderer = opts.renderer ?? {
     ...Object.create(null),
     once(this: CliRenderer) {
@@ -339,6 +347,9 @@ export function createTuiPluginApi(opts: Opts = {}): HostPluginApi {
       set(name) {
         return set(name)
       },
+      preview(name) {
+        return preview(name)
+      },
       async install(file) {
         if (opts.theme?.install) return opts.theme.install(file)
         throw new Error("base theme.install should not run")

packages/plugin/src/tui.ts

@@ -361,6 +361,7 @@ export type TuiTheme = {
   readonly selected: string
   has: (name: string) => boolean
   set: (name: string) => boolean
+  preview: (name: string) => boolean
   install: (jsonPath: string) => Promise<void>
   mode: () => "dark" | "light"
   readonly ready: boolean