opencode-agent · Oct 30, 2026 · Oct 26, 2026 · Oct 30, 2026
@@ -1,3 +1,5 @@
+import { flow, Option, Schema } from "effect"
+
 export const DESKTOP_NATIVE_LOCALES = [
   "en",
   "zh",
@@ -302,6 +304,9 @@ export const DESKTOP_NATIVE_ENGLISH = {
 
   "desktop.picker.error.notSelected": "File was not selected by the picker",
   "desktop.picker.error.sizeLimit": "Selected attachments exceed the {{limit}} MB limit",
+
+  "desktop.contextMenu.spellcheck": "Spellcheck",
+  "desktop.contextMenu.spellcheckLanguages": "Spellcheck Languages",
 } as const
 
 export type DesktopNativeKey = keyof typeof DESKTOP_NATIVE_ENGLISH
@@ -310,6 +315,7 @@ export type DesktopNativeMessages = Record<DesktopNativeKey, string>
 
 export type DesktopNativeBundle = { locale: DesktopNativeLocale; messages: DesktopNativeMessages }
 
+// SAFETY: DESKTOP_NATIVE_ENGLISH is a const literal, so its own keys are exactly DesktopNativeKey.
 export const DESKTOP_NATIVE_KEYS = Object.keys(DESKTOP_NATIVE_ENGLISH) as DesktopNativeKey[]
 
 export const DESKTOP_NATIVE_MAX_PAYLOAD_BYTES = 64 * 1024
@@ -320,35 +326,24 @@ export function createDesktopNativeBundle(
 ): DesktopNativeBundle {
   return {
     locale,
+    // SAFETY: the entries map every DesktopNativeKey to a string, which is exactly DesktopNativeMessages.
     messages: Object.fromEntries(DESKTOP_NATIVE_KEYS.map((key) => [key, translate(key)])) as DesktopNativeMessages,
   }
 }
 
-export function parseDesktopNativeBundle(value: unknown): DesktopNativeBundle | undefined {
-  if (!value || typeof value !== "object" || Array.isArray(value)) return undefined
-
-  try {
-    if (new TextEncoder().encode(JSON.stringify(value)).byteLength > DESKTOP_NATIVE_MAX_PAYLOAD_BYTES) return undefined
-  } catch {
-    return undefined
-  }
+const DesktopNativeBundleSchema = Schema.Struct({
+  locale: Schema.Literals(DESKTOP_NATIVE_LOCALES),
+  messages: Schema.Record(Schema.Literals(DESKTOP_NATIVE_KEYS), Schema.String),
+}).check(
+  Schema.makeFilter(
+    (bundle) => new TextEncoder().encode(JSON.stringify(bundle)).byteLength <= DESKTOP_NATIVE_MAX_PAYLOAD_BYTES,
+  ),
+)
 
-  const bundle = value as { locale?: unknown; messages?: unknown }
+const decodeDesktopNativeBundle = Schema.decodeUnknownOption(DesktopNativeBundleSchema, { onExcessProperty: "error" })
 
-  if (!DESKTOP_NATIVE_LOCALES.some((locale) => locale === bundle.locale)) return undefined
-
-  if (!bundle.messages || typeof bundle.messages !== "object" || Array.isArray(bundle.messages)) return undefined
-  const messages = bundle.messages as Record<string, unknown>
-  const keys = Object.keys(messages)
-
-  if (keys.length !== DESKTOP_NATIVE_KEYS.length) return undefined
-
-  if (!DESKTOP_NATIVE_KEYS.every((key) => typeof messages[key] === "string")) return undefined
-
-  if (!keys.every((key) => key in DESKTOP_NATIVE_ENGLISH)) return undefined
-
-  return bundle as DesktopNativeBundle
-}
+/** Validates a bundle the renderer sent over IPC: a supported locale, exactly the native keys, and a bounded size. */
+export const parseDesktopNativeBundle = flow(decodeDesktopNativeBundle, Option.getOrUndefined)
 
 export function formatDesktopNativeMessage(message: string, params?: Record<string, string | number>) {
   if (!params) return message

@@ -1005,6 +1005,8 @@ export const dict = {
   "settings.general.row.followUpBehavior.steer": "Steer",
   "settings.general.row.pinchZoom.title": "Pinch to zoom",
   "settings.general.row.pinchZoom.description": "Allow trackpad pinch and Ctrl-scroll gestures to zoom",
+  "settings.general.row.spellcheck.title": "Spellcheck",
+  "settings.general.row.spellcheck.description": "Underline misspelled words while typing",
 
   "sound.option.none": "None",
   "sound.option.alert01": "Alert 01",

@@ -72,7 +72,7 @@ const desktop = [
 ]
 
 export const dict = {
-  ...Object.fromEntries(DESKTOP_NATIVE_KEYS.map((key, index) => [key, desktop[index]])),
+  ...Object.fromEntries(desktop.map((value, index) => [DESKTOP_NATIVE_KEYS[index], value])),
   "command.category.suggested": "Predloženo",
   "command.category.view": "Prikaz",
   "command.category.project": "Projekt",

@@ -72,7 +72,7 @@ const desktop = [
 ]
 
 export const dict = {
-  ...Object.fromEntries(DESKTOP_NATIVE_KEYS.map((key, index) => [key, desktop[index]])),
+  ...Object.fromEntries(desktop.map((value, index) => [DESKTOP_NATIVE_KEYS[index], value])),
   "command.category.suggested": "Javasolt",
   "command.category.view": "Nézet",
   "command.category.project": "Projekt",

@@ -72,7 +72,7 @@ const desktop = [
 ]
 
 export const dict = {
-  ...Object.fromEntries(DESKTOP_NATIVE_KEYS.map((key, index) => [key, desktop[index]])),
+  ...Object.fromEntries(desktop.map((value, index) => [DESKTOP_NATIVE_KEYS[index], value])),
   "command.category.suggested": "Tillögur",
   "command.category.view": "Skoða",
   "command.category.project": "Verkefni",

@@ -72,7 +72,7 @@ const desktop = [
 ]
 
 export const dict = {
-  ...Object.fromEntries(DESKTOP_NATIVE_KEYS.map((key, index) => [key, desktop[index]])),
+  ...Object.fromEntries(desktop.map((value, index) => [DESKTOP_NATIVE_KEYS[index], value])),
   "command.category.suggested": "Siūloma",
   "command.category.view": "Rodinys",
   "command.category.project": "Projektas",

@@ -108,6 +108,12 @@ type PlatformBase = {
   /** Allow native pinch/Ctrl-scroll zoom gestures (desktop only) */
   setPinchZoomEnabled?(enabled: boolean): Promise<void> | void
 
+  /** Get whether the native spellchecker underlines misspelled words (desktop only) */
+  getSpellcheckEnabled?(): Promise<boolean>
+
+  /** Turn the native spellchecker on or off (desktop only) */
+  setSpellcheckEnabled?(enabled: boolean): Promise<void>
+
   /** Run a desktop-only menu action from the app chrome */
   runDesktopMenuAction?(action: DesktopMenuAction): Promise<void> | void
 

@@ -249,6 +249,17 @@ export const SettingsGeneral: Component = () => {
     void update.catch(() => setPinchZoom(!checked))
   }
 
+  const [spellcheck, { mutate: setSpellcheck }] = createResource(
+    () => desktop() && "getSpellcheckEnabled" in platform,
+    () => platform.getSpellcheckEnabled?.().catch(() => true) ?? true,
+    { initialValue: true },
+  )
+
+  const onSpellcheckChange = (checked: boolean) => {
+    setSpellcheck(checked)
+    void platform.setSpellcheckEnabled?.(checked).catch(() => setSpellcheck(!checked))
+  }
+
   const GeneralSection = () => (
     <div class="settings-section">
       <h3 class="settings-section-title">{language.t("settings.general.section.general")}</h3>
@@ -282,6 +293,14 @@ export const SettingsGeneral: Component = () => {
               <Switch checked={pinchZoom.latest} onChange={onPinchZoomChange} />
             </div>
           </SettingsRow>
+          <SettingsRow
+            title={language.t("settings.general.row.spellcheck.title")}
+            description={language.t("settings.general.row.spellcheck.description")}
+          >
+            <div data-action="settings-spellcheck">
+              <Switch checked={spellcheck.latest} onChange={onSpellcheckChange} />
+            </div>
+          </SettingsRow>
         </Show>
 
         <PluginSettingsSections page="general" section="general" />

@@ -55,6 +55,13 @@ export const clientSettings: Entry<SettingsRootTab>[] = [
     target: "settings-pinch-zoom",
     available: "desktop",
   },
+  {
+    tab: "general",
+    label: "settings.general.row.spellcheck.title",
+    target: "settings-spellcheck",
+    keywords: "spelling spell check dictionary",
+    available: "desktop",
+  },
   {
     tab: "general",
     label: "settings.general.row.mobileTitlebarBottom.title",

@@ -8,6 +8,7 @@ import { setForceFocus } from "../native/debug"
 import { showCliInstaller } from "../native/install-cli"
 import { DesktopLogging, scoped } from "../native/logging"
 import { createMenu, sendMenuCommand } from "../native/menu"
+import { getSpellcheckEnabled, setSpellcheckEnabled } from "../native/spellcheck"
 import { setNativeTranslations } from "../native/translations"
 import { IpcPortHandoff } from "../ipc-transport"
 import { ApplicationLifecycle } from "../lifecycle"
@@ -37,6 +38,8 @@ export const appHandlers = AppRpcs.toLayer(
       AppCheckAppExists: ({ appName }) => checkAppExists(appName).pipe(Effect.orDie),
       AppResolveAppPath: ({ appName }) => resolveAppPath(appName).pipe(Effect.orDie),
       AppSetBackgroundColor: ({ color }) => Effect.sync(() => setBackgroundColor(color)),
+      AppGetSpellcheckEnabled: () => Effect.sync(getSpellcheckEnabled),
+      AppSetSpellcheckEnabled: ({ enabled }) => Effect.sync(() => setSpellcheckEnabled(enabled)),
       AppExportDebugLogs: () => logging.exportDebug,
       AppSetForceFocus: ({ enabled }, context) => promise(() => setForceFocus(sender(handoff, context), enabled)),
       AppRecordFatalRendererError: ({ error }) =>

@@ -6,12 +6,18 @@ import { DesktopPaths } from "../paths"
 import { getUserShell, loadShellEnv } from "../service/shell-env"
 import { registerRendererProtocol, setDockIcon, setProtocolReporter } from "../windows"
 import { scoped } from "../native/logging"
+import { applySpellcheck, spellcheckMenuItems } from "../native/spellcheck"
 
 // electron-context-menu attaches to every existing and future window, so it can load once the first
 // window is up instead of holding up startup with its dependency tree.
 export const installContextMenu = Effect.gen(function* () {
   const { default: contextMenu } = yield* Effect.promise(() => import("electron-context-menu"))
-  contextMenu({ showSaveImageAs: true, showLookUpSelection: false, showSearchWithGoogle: false })
+  contextMenu({
+    showSaveImageAs: true,
+    showLookUpSelection: false,
+    showSearchWithGoogle: false,
+    append: (_actions, params) => (params.isEditable ? spellcheckMenuItems() : []),
+  })
 })
 
 export const prepareApplicationEnvironment = Effect.gen(function* () {
@@ -45,12 +51,13 @@ export const prepareDesktop = Effect.gen(function* () {
   )
   registerRendererProtocol(paths.rendererRoot)
   setDockIcon(path, paths)
+  applySpellcheck()
 })
 
 export const loadProxyEnvironment = Effect.gen(function* () {
   yield* Effect.try(() => {
     ensureLoopbackNoProxy()
-    // Electron 41.2 has a newer Node API than the current @types/node package.
+    // SAFETY: Electron 41.2 ships a Node with http.setGlobalProxyFromEnv, which the current @types/node lacks.
     const proxyAwareHttp = http as typeof http & { setGlobalProxyFromEnv(): void }
     proxyAwareHttp.setGlobalProxyFromEnv()
   }).pipe(Effect.catch((error) => Effect.logWarning("failed to load proxy environment", { error })))

@@ -0,0 +1,32 @@
+import { expect, test } from "bun:test"
+import { defaultSpellcheckLanguages } from "./spellcheck-languages"
+
+// A slice of Electron 44's Linux and Windows list, including aliases such as de and de-DE.
+const available = ["de", "de-DE", "en", "en-AU", "en-GB", "en-US", "es", "es-MX", "fr", "fr-FR", "pt", "pt-BR"]
+
+test.each([
+  [["de-DE"], ["de-DE", "en-US"]],
+  [
+    ["de-DE", "de", "en-US", "en"],
+    ["de-DE", "en-US"],
+  ],
+  [
+    ["de-AT", "fr-CA"],
+    ["de", "fr", "en-US"],
+  ],
+  [
+    ["en-GB", "de-DE"],
+    ["en-GB", "de-DE"],
+  ],
+  [["en-NZ"], ["en"]],
+  [
+    ["es-MX", "es-ES"],
+    ["es-MX", "en-US"],
+  ],
+  [["pt-AO"], ["pt", "en-US"]],
+  [["DE-de"], ["de-DE", "en-US"]],
+  [["ja-JP"], ["en-US"]],
+  [[], ["en-US"]],
+])("system languages %p use dictionaries %p", (preferred, languages) => {
+  expect(defaultSpellcheckLanguages(available, preferred)).toEqual(languages)
+})
@@ -0,0 +1,16 @@
+const base = (tag: string) => tag.split("-")[0].toLowerCase()
+
+// One dictionary per system language, matched exactly or by base language (de-AT -> de). Chromium
+// lists aliases such as de and de-DE separately, so a later tag for the same language is skipped.
+// US English is added when none of them is English, because prompts mix prose with English code terms.
+export function defaultSpellcheckLanguages(available: readonly string[], preferred: readonly string[]) {
+  const find = (tag: string) => available.find((language) => language.toLowerCase() === tag.toLowerCase())
+
+  const languages = preferred
+    .flatMap((tag) => find(tag) ?? find(base(tag)) ?? [])
+    .filter((language, index, all) => all.findIndex((other) => base(other) === base(language)) === index)
+
+  if (languages.some((language) => base(language) === "en") || !available.includes("en-US")) return languages
+
+  return [...languages, "en-US"]
+}
@@ -0,0 +1,74 @@
+import { app, session, type MenuItemConstructorOptions } from "electron"
+import { SPELLCHECK_ENABLED_KEY, SPELLCHECK_LANGUAGES_KEY } from "../storage/keys"
+import { getStore } from "../storage/store"
+import { defaultSpellcheckLanguages } from "./spellcheck-languages"
+import { nativeLanguageOptions, nativeT } from "./translations"
+
+// macOS checks spelling with the system spellchecker, which detects the language itself; Electron
+// ignores dictionary choices there.
+const choosesLanguages = process.platform !== "darwin"
+
+export function applySpellcheck() {
+  // Setting languages also turns the spellchecker on, so the stored on/off state goes last.
+  if (choosesLanguages) session.defaultSession.setSpellCheckerLanguages(spellcheckLanguages())
+
+  session.defaultSession.setSpellCheckerEnabled(getSpellcheckEnabled())
+}
+
+export function getSpellcheckEnabled() {
+  return getStore().get(SPELLCHECK_ENABLED_KEY) !== false
+}
+
+export function setSpellcheckEnabled(enabled: boolean) {
+  getStore().set(SPELLCHECK_ENABLED_KEY, enabled)
+  session.defaultSession.setSpellCheckerEnabled(enabled)
+}
+
+// Mirrors the Spellcheck menu in chat apps: a checkbox, and a dictionary picker where Electron owns
+// the dictionaries.
+export function spellcheckMenuItems(): MenuItemConstructorOptions[] {
+  const enabled = getSpellcheckEnabled()
+  const current = session.defaultSession.getSpellCheckerLanguages()
+
+  const toggle: MenuItemConstructorOptions = {
+    label: nativeT("desktop.contextMenu.spellcheck"),
+    type: "checkbox",
+    checked: enabled,
+    click: () => setSpellcheckEnabled(!enabled),
+  }
+
+  if (!choosesLanguages) return [{ type: "separator" }, toggle]
+
+  return [
+    { type: "separator" },
+    toggle,
+    {
+      label: nativeT("desktop.contextMenu.spellcheckLanguages"),
+      enabled,
+      submenu: nativeLanguageOptions(session.defaultSession.availableSpellCheckerLanguages).map((option) => ({
+        label: option.label,
+        type: "checkbox",
+        checked: current.includes(option.tag),
+        // The last dictionary stays; the Spellcheck checkbox is how to stop checking entirely.
+        enabled: !(current.length === 1 && current[0] === option.tag),
+        click: () => {
+          const next = current.includes(option.tag)
+            ? current.filter((language) => language !== option.tag)
+            : [...current, option.tag]
+
+          getStore().set(SPELLCHECK_LANGUAGES_KEY, next)
+          session.defaultSession.setSpellCheckerLanguages(next)
+        },
+      })),
+    },
+  ]
+}
+
+// Dictionaries picked from the menu win; otherwise follow the system languages on every launch.
+function spellcheckLanguages() {
+  const available = session.defaultSession.availableSpellCheckerLanguages
+  const stored = getStore().get(SPELLCHECK_LANGUAGES_KEY)
+  const chosen = Array.isArray(stored) ? available.filter((language) => stored.includes(language)) : []
+
+  return chosen.length ? chosen : defaultSpellcheckLanguages(available, app.getPreferredSystemLanguages())
+}
@@ -29,6 +29,16 @@ export function nativeT(key: DesktopNativeKey, params?: Record<string, string |
   return formatDesktopNativeMessage(bundle.messages[key], params)
 }
 
+/** Language tags with their names in the app locale, sorted for a menu. */
+export function nativeLanguageOptions(tags: readonly string[]) {
+  const locale = DESKTOP_NATIVE_LOCALE_TAGS[bundle.locale]
+  const names = new Intl.DisplayNames([locale], { type: "language" })
+
+  return tags
+    .map((tag) => ({ tag, label: names.of(tag) ?? tag }))
+    .toSorted((a, b) => a.label.localeCompare(b.label, locale))
+}
+
 /** The app locale the renderer last pushed. GUI plugin catalogs resolve against it. */
 export function nativeLocale() {
   return bundle.locale

@@ -6,6 +6,10 @@ export const PINCH_ZOOM_ENABLED_KEY = "pinchZoomEnabled"
 
 export const ZOOM_LEVEL_KEY = "zoomLevel"
 
+export const SPELLCHECK_ENABLED_KEY = "spellcheckEnabled"
+
+export const SPELLCHECK_LANGUAGES_KEY = "spellcheckLanguages"
+
 export const BACKGROUND_COLOR_KEY = "backgroundColor"
 
 export const WINDOW_IDS_KEY = "windowIds"

@@ -71,6 +71,8 @@ export type ElectronAPI = {
   setBackgroundColor(color: string): Promise<void>
   exportDebugLogs(): Promise<string>
   setForceFocus(enabled: boolean): Promise<void>
+  getSpellcheckEnabled(): Promise<boolean>
+  setSpellcheckEnabled(enabled: boolean): Promise<void>
   recordFatalRendererError(error: FatalRendererError): Promise<void>
   setNativeTranslations(bundle: DesktopNativeBundle): Promise<void>
 }
@@ -94,6 +94,8 @@ export const api: ElectronAPI = {
   setBackgroundColor: (color) => invoke("AppSetBackgroundColor", { color }),
   exportDebugLogs: () => invoke("AppExportDebugLogs"),
   setForceFocus: (enabled) => invoke("AppSetForceFocus", { enabled }),
+  getSpellcheckEnabled: () => invoke("AppGetSpellcheckEnabled"),
+  setSpellcheckEnabled: (enabled) => invoke("AppSetSpellcheckEnabled", { enabled }),
   recordFatalRendererError: (error) => invoke("AppRecordFatalRendererError", { error }),
   setNativeTranslations: (bundle) => invoke("AppSetNativeTranslations", { value: bundle }),
 }