---
name: EHSAN HMR context crash (false runtime error)
description: When the POC throws "useLanguage must be used within a LanguageProvider" but the source is correct, it's a stale HMR state — restart the workflow.
---

# "useLanguage must be used within a LanguageProvider" after edits

If the EHSAN POC crashes with `useLanguage must be used within a LanguageProvider`
(and/or `Invalid hook call ... more than one copy of React`, or
`Cannot read properties of undefined`) **while `App.tsx` clearly wraps the tree in
`LanguageProvider` and the source is correct**, it is almost always a corrupted
Vite Fast Refresh (HMR) state, NOT a code bug.

**Root cause:** `src/contexts/LanguageContext.tsx` exports both a component
(`LanguageProvider`) and a hook (`useLanguage`) from one file, so Vite logs
`Could not Fast Refresh ("useLanguage" export is incompatible)`. After several hot
updates the running app ends up with a duplicate React context instance and the
hook can't find the provider.

**Fix:** restart the `artifacts/ehsan-poc: web` workflow. The built/production app
is unaffected — this is dev-only.

**How to apply:** before editing source to "fix" such an error, confirm the current
files are actually correct (provider present, key exists); if so, just restart the
workflow instead of changing code.