What causes "llamacpp extension not found" in janhq/jan?

Ensure the @janhq/llamacpp-extension is installed and enabled

llamacpp extension not found

Error message

llamacpp extension not found

What it means

getLlamacppDevices looks up the '@janhq/llamacpp-extension' via the extension manager and throws if it is not registered, because GPU device queries require that extension. It guards against calling getDevices() on undefined.

Solutions

Ensure the @janhq/llamacpp-extension is installed and enabled
Wait for extension manager initialization before querying devices
Reinstall the llamacpp extension if it failed to load
Guard callers with extensionManager.getByName check first

Example fix

// before
const devices = await getLlamacppDevices()
// after
const ext = window.core.extensionManager?.getByName('@janhq/llamacpp-extension')
const devices = ext ? await getLlamacppDevices() : []

Defensive patterns

Strategy: type-guard

Validate before calling

const ext = window.core.extensionManager?.getByName('@janhq/llamacpp-extension')
const canQueryDevices = !!ext

Type guard

function hasLlamacpp(m: typeof window.core.extensionManager): boolean { return !!m?.getByName('@janhq/llamacpp-extension') }

Try / catch

try { const devices = await getLlamacppDevices() } catch { const devices = []; showExtensionWarning() }

Prevention

Gate hardware UI behind extension-manager ready signal
Verify llamacpp extension presence in startup diagnostics
Handle optional extensions gracefully in settings pages

When it happens

Trigger: getLlamacppDevices called when the llamacpp extension is not installed, not yet loaded, or was disabled/removed.

Common situations: Hardware settings page opened before extensions finish loading, extension failed to install, or llamacpp extension uninstalled while hardware service still references it.

Understand the failure class

Background: "not installed", "pip install", "required for": how missing-dependency errors surface across open-source libraries — this error's family across 34 libraries.

Related errors

AI-assisted analysis of janhq/jan@7205d770c1 (2026-09-17). Data as JSON: /api/errors/78d8cb0d32b7695e. Report an issue: GitHub.

Appendix: source

Thrown at web-app/src/services/hardware/tauri.ts:23

import { invoke } from '@tauri-apps/api/core'
import type { HardwareData, SystemUsage, DeviceList } from './types'
import { DefaultHardwareService } from './default'

export class TauriHardwareService extends DefaultHardwareService {
  async getHardwareInfo(): Promise<HardwareData | null> {
    return invoke('plugin:hardware|get_system_info') as Promise<HardwareData>
  }

  async getSystemUsage(): Promise<SystemUsage | null> {
    return invoke('plugin:hardware|get_system_usage') as Promise<SystemUsage>
  }

  async getLlamacppDevices(): Promise<DeviceList[]> {
    const extensionManager = window.core.extensionManager
    const llamacppExtension = extensionManager.getByName('@janhq/llamacpp-extension')

    if (!llamacppExtension) {
      throw new Error('llamacpp extension not found')
    }

    return llamacppExtension.getDevices()
  }

  async setActiveGpus(data: { gpus: number[] }): Promise<void> {
    // TODO: llama.cpp extension should handle this
    console.log(data)
  }

  async refreshHardwareInfo(): Promise<void> {
    await invoke('plugin:hardware|refresh_system_info')
  }
}

View on GitHub (pinned to 7205d770c1)