janhq/jan · error

String(e)

Error message

String(e)

What it means

findSessionByModel wraps the Tauri invoke('plugin:mlx|find_mlx_session_by_model'); on any native-side failure it logs the error and rethrows it as String(e). Callers of load/unload/chat therefore see the raw native error text without a stack trace.

Solutions

1. Check logs — the original error is logged before rethrow
2. Ensure the Tauri mlx plugin is installed/registered for the current build
3. Retry after the app's backend has fully initialized (invoke before ready fails)
4. Validate modelId is a non-empty, correctly formatted identifier before lookup
5. Update the app if plugin command names changed between versions

Example fix

// before
const s = await mlx.getSessionInfo(modelId)
// after
let s = null
try {
  s = await mlx.getSessionInfo(modelId)
} catch (e) {
  logger.warn('MLX session lookup failed, treating as not loaded', e)
}

// Guard modelId before native lookup
if (typeof modelId !== 'string' || modelId.trim() === '') {
  throw new Error('modelId is required for MLX session lookup')
}

function hasSessionInfo(v: unknown): v is SessionInfo {
  return !!v && typeof v === 'object' && 'pid' in v && typeof (v as SessionInfo).pid === 'number'
}

try {
  const s = await mlx.getSessionInfo(modelId)
} catch (e) {
  logger.warn('MLX session lookup failed; treating as no session', e)
  const s = null
}

When it happens

Trigger: Any session lookup when the Tauri mlx plugin errors — plugin not registered, IPC failure, app backend crashed, or malformed modelId causing a native-side failure.

Common situations: Calling MLX APIs before the app's native plugin layer is ready, after an app update changed plugin commands, or in environments (e.g. web build) where the Tauri IPC is unavailable.

Understand the failure class

Background: "API request failed": what wrapped HTTP errors from external APIs mean and how to find the real cause — this error's family across 29 libraries.

Related errors

• ${e}
• IO error
• MlxError , message: " " }}
• No running MLX session found for model
• ${String(e)}

AI-assisted analysis of janhq/jan@7205d770c1 (2026-09-17). Data as JSON: /api/errors/ca60537a3eacc45e. Report an issue: GitHub.

Appendix: source

Thrown at extensions/mlx-extension/src/index.ts:382

      }
      return result
    } catch (error) {
      logger.error('Error unloading MLX model:', error)
      return {
        success: false,
        error: `Failed to unload model: ${error}`,
      }
    }
  }

  private async findSessionByModel(modelId: string): Promise<SessionInfo> {
    try {
      return await invoke<SessionInfo>('plugin:mlx|find_mlx_session_by_model', {
        modelId,
      })
    } catch (e) {
      logger.error(e)
      throw new Error(String(e))
    }
  }

  override async chat(
    opts: chatCompletionRequest,
    abortController?: AbortController
  ): Promise<chatCompletion | AsyncIterable<chatCompletionChunk>> {
    const sessionInfo = await this.findSessionByModel(opts.model)
    if (!sessionInfo) {
      throw new Error(`No active MLX session found for model: ${opts.model}`)
    }

    // Check if the process is alive
    const isAlive = await invoke<boolean>('plugin:mlx|is_mlx_process_running', {
      pid: sessionInfo.pid,
    })

    if (isAlive) {

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