> ## 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.

# E0404 — WrongTarget

> The artifact was compiled for a different target backend and cannot be run on akida-akd1500 without recompilation.

<Warning>E0404: artifact was not compiled for akida-akd1500</Warning>

## What happened

A `.thx` artifact was submitted to the `akida-akd1500` backend, but its `metadata.target` field names a different target (for example `"sim"`). The backend rejects artifacts compiled for other targets.

## Why

A `.thx` artifact carries the target it was compiled for. The compiler resolves target-specific constants at compile time — for example, `alpha = exp(-dt / tau_mem)` uses the target's native `dt_ms`. Running an artifact compiled for one target on a different backend without recompilation may produce incorrect results even if both backends accept the same layer types.

## How to fix

Recompile the model for `akida-akd1500`:

```python theme={null}
import thrindex as thx

thx.compile(model, "model.thx", target="akida-akd1500")
```

Note that `akida-akd1500` rejects models containing [LIF layers](/errors/E0401) or [synaptic delays](/errors/E0402). If your model uses either, see those error pages for your options.

## Example

```
E0404: .thx artifact was compiled for target="sim", not "akida-akd1500".
Observed: metadata.target = "sim".
Why: A .thx artifact carries the target it was compiled for. Running it on a
     different backend without recompilation may produce incorrect results.
What to do: Recompile with target="akida-akd1500":
              thrindex build --target akida-akd1500 model.py
Docs: https://docs.thrindex.com/errors/E0404
```