janhq/jan · warning · Error

Backend installed but failed to refresh UI: ${String(e)}

Error message

Backend installed but failed to refresh UI: ${String(e)}

What it means

The backend archive was successfully installed and normalized, but the post-install UI refresh (refreshBackendOptions) threw an error. The install itself is complete, but the UI/settings state may be inconsistent. The error is re-thrown to signal that the user may need to restart the app to see the new backend.

Source

Thrown at extensions/llamacpp-extension/src/index.ts:2944

        }
      }
    }

    if (!(await fs.existsSync(expectedBinPath))) {
      await fs.rm(backendDir)
      throw new Error(
        'Not a supported backend archive! Missing llama-server binary.'
      )
    }

    try {
      await this.refreshBackendOptions()
      logger.info(
        `Backend ${backendIdentifier}/${version} installed and UI refreshed`
      )
    } catch (e) {
      logger.error('Backend installed but failed to refresh UI', e)
      throw new Error(
        `Backend installed but failed to refresh UI: ${String(e)}`
      )
    }
  }

  /**
   * Install the supplementary CUDA runtime DLLs that upstream ships separately
   * (`cudart-llama-bin-<backend>.zip`) into every installed backend of that
   * type, so llama-server can resolve cublas/cudart at launch.
   */
  async installCudaRuntime(path: string): Promise<void> {
    if (
      !(await fs.existsSync(path)) ||
      (!path.endsWith('tar.gz') && !path.endsWith('zip'))
    ) {
      throw new Error(`Invalid path or file ${path}`)
    }

View on GitHub (pinned to fad3f12a14)

Solutions

1. Restart the application — the backend is installed on disk and will be discovered on next launch.
2. If the error persists, check the settings file for corruption and verify the settings store is writable.
3. Manually trigger a backend options refresh from the UI after restart.

try {
  await extension.installBackend(path)
} catch (e) {
  if (e instanceof Error && e.message.includes('failed to refresh UI')) {
    // Backend IS installed; just needs a restart to appear in UI
    console.warn('Backend installed; restart the app to see it in the UI')
  } else {
    throw e
  }
}

When it happens

Trigger: refreshBackendOptions throws: it reads installed backends and updates the settings/UI, which can fail if the settings store is locked, the IPC call times out, or there is a serialization error in the backend options data.

Common situations: App is shutting down during the install; settings file is locked by another process; a concurrent settings write causes a read/parse error; the UI was already unmounted.

Related errors

• No supported backend binaries found for this system. Backend
• Failed to fetch supported backends: ${error instanceof Error
• Critical settings "llamacpp_version" / "llamacpp_backend" no
• Invalid backend string: ${targetBackendString} supplied to u
• Invalid backend string format: "${targetBackendString}". Exp

AI-assisted analysis of janhq/jan@fad3f12a14 (2026-08-12). Data as JSON: /api/errors/dc254bb7cc83dd5d. Report an issue: GitHub.