[FEATURE] Desktop: allow multiple simultaneous spellchecker languages

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

The desktop app's spellchecker is locked to a single dictionary, en-US. For anyone who writes to Claude in more than one language, the prompt input becomes a wall of red underlines — every word of Norwegian, German, French or Czech is flagged as a misspelling.

The current choice is binary, and both options are bad:

• Spellcheck on — my English is checked, which I want, but every Norwegian word is underlined.
• Spellcheck off — the red noise stops, but I lose the English checking I actually want. (Not currently possible in-app anyway: #58693.)

In a browser this is a solved problem. Chrome and Edge let you enable several dictionaries at once and check against all of them. The desktop app takes that away.

%APPDATA%\Claude\Preferences on Windows shows the single hardcoded entry:

{"spellcheck":{"dictionaries":["en-US"],"dictionary":""}}

It is not derived from the OS language list. Windows already reports both languages as available with spellchecking enabled:

PS> Get-WinUserLanguageList | ForEach-Object { "$($_.LanguageTag) spellcheck=$($_.Spellchecking)" }
en-US spellcheck=True
nb spellcheck=True

The app uses en-US only, and there is no language switcher in the input's right-click menu. The information needed to do the right thing automatically is already on the machine.

This has been reported five times, from at least four languages, and the underlying ask — several languages at the same time — has never been addressed:

• #60012 — spell check only checks the primary Windows language (German ignored) — closed as not planned
• #72247 — expose a spellchecker language setting, stuck on en-US — closed as invalid
• #68621 — add spell-check language configuration / disable option — closed as not planned
• #66464 — uses en-US despite the system language being en-GB — closed as not planned
• #58693 — spell checking cannot be turned off — still open

Proposed Solution

A spellcheck language setting that accepts more than one language:

• Settings → a multi-select list of available dictionaries, with the OS preferred languages pre-ticked on first run
• and/or a spellcheckLanguages key in settings, e.g. ["en-US", "nb"]
• and an explicit "off" option, which would also close out #58693

This should be inexpensive. Electron's Chromium spellchecker already supports multiple simultaneous dictionaries — it is one call:

session.defaultSession.setSpellCheckerLanguages(['en-US', 'nb'])

• setSpellCheckerLanguages takes an array. A word is only flagged if every active dictionary rejects it. Hunspell dictionaries download on demand.
• Valid codes come from Chromium's kSupportedSpellCheckerLanguages in components/spellcheck/common/spellcheck_common.cc. Norwegian Bokmål is already in that list as {"nb", "nb-NO"}, so no new dictionary work is needed.
• session.availableSpellCheckerLanguages can populate the settings UI directly, so the list does not have to be maintained by hand.
• macOS caveat: setSpellCheckerLanguages is a no-op there — macOS uses the native checker, which auto-detects language and is configured in System Settings. So this is a Windows/Linux change, and on macOS the setting should be hidden or marked as OS-managed.

Alternative Solutions

There is currently no working workaround.

#72247 suggested hand-editing spellcheck.dictionaries in %APPDATA%\Claude\Preferences to a multi-language list and force-quitting the app so it does not rewrite the file on a clean exit. That no longer holds. I set the key to ["en-US","nb"] and the running app rewrote it back to ["en-US"] on its own, within half an hour, with no restart involved:

11:05 edit applied {"spellcheck":{"dictionaries":["en-US","nb"],"dictionary":""}}
11:37 app rewrote it {"spellcheck":{"dictionaries":["en-US"],"dictionary":""}}
So the stored preference is not what drives the checker — a hardcoded single-language list is being applied over it.

Discord, which uses the same Electron spellchecker, behaves the same way: the edit survives a force-quit, then the app resets the key to ["en-US"] on next launch and never downloads the second dictionary. The pattern is "app overrides Chromium's stored preference", which is why this has to be a real setting rather than a config-file tweak.

Adding the language in Windows Settings → Time & language → Language does not help either. The app ignores the OS preferred-language list even though it is already populated correctly (see the Get-WinUserLanguageList output above) — same as reported in #60012.

Priority

Medium - Would be very helpful

Feature Category

Configuration and settings

Use Case Example

I am Norwegian and work in English. In a single session I write English prompts to Claude and Norwegian notes, commit text and messages. Today every Norwegian sentence I type comes back solid red, so I either put up with the noise or give up spellchecking altogether. With two dictionaries enabled, both languages are checked and only genuine typos are underlined — exactly what the browser version already does.

Additional Context

Environment:

• Claude Code desktop app 1.34493.1.0 (MSIX), CLI 2.1.237
• Windows 11 Pro 10.0.26200
• Windows display language English; Norwegian Bokmål installed as a preferred language with spell check enabled