> ## Documentation Index
> Fetch the complete documentation index at: https://docs.thrindex.com/llms.txt
> Use this file to discover all available pages before exploring further.

# E0204 — Execution (backend)

> The hardware backend reported an execution error.

<Warning>E0204: backend execution failed</Warning>

## What happened

The hardware backend's execution path returned an error. The model loaded successfully, the input shape was valid, but the actual inference call failed.

## Why

This is a backend-specific error. Common causes:

* The hardware driver is not installed or not running
* The hardware device is not connected or not powered
* The device ran out of neuron core resources for this model
* A driver API call timed out or returned an unexpected status code

## How to fix

1. **Check the driver**: ensure the hardware driver is installed and the device is connected. For Loihi 2: verify `nxsdk` is installed and `lsusb` shows the device.
2. **Check device resources**: the model may require more neuron cores than are available. Try a smaller model.
3. **Check the error detail**: the error message includes a backend-specific `detail` string from the driver. Use it to diagnose the hardware-level failure.
4. **Run on sim first**: `thrindex run model.thx --target sim` to confirm the artifact is valid before debugging hardware.

## Example

```
E0204: backend execution failed
Why: loihi2 driver returned status RESOURCE_EXHAUSTED: model requires 128 cores, device has 64
Fix: check backend driver and hardware connection
Docs: https://docs.thrindex.com/errors/E0204
```