> ## 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.

# E0003 — UnknownLayerType

> The artifact contains a layer type this simulator does not recognize.

<Warning>E0003: unknown layer type</Warning>

## What happened

The `.thx` artifact contains a layer with a `type` field that this build of `thrindex-sim` does not support. The simulator cannot construct or run the layer.

## Why

The artifact was compiled with a newer version of THRINDEX that supports layer types (e.g. `Recurrent`, `SpikingConvTranspose2d`) that a previous simulator build does not know.

## How to fix

1. **Upgrade thrindex**: `pip install --upgrade thrindex`. This is always the right fix when running an artifact compiled by a newer version.
2. If you cannot upgrade, recompile the model using a supported architecture with the installed version.

## Example

```
E0003: unknown layer type: "Recurrent"
Why: the artifact was compiled with a newer thrindex that supports layer types
     this simulator does not know.
Fix: upgrade thrindex-sim, or recompile the model with a compatible version.
Docs: https://docs.thrindex.com/errors/E0003
```