> ## 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.

# E0009 — IntegrityCheckFailed

> The artifact's CRC32 checksum does not match. The file was modified after compilation.

<Warning>E0009: artifact integrity check failed (CRC32 mismatch)</Warning>

## What happened

The CRC32 stored in the artifact does not match the CRC32 computed over the artifact's body. The file was modified — either accidentally or intentionally — after `thx.compile()` wrote it.

## Why

Common causes:

* A text editor opened and re-saved the `.thx` file (changing line endings, encoding)
* File transfer corruption (truncation, bit flip, encoding conversion)
* Intentional modification of weights or parameters after compilation

## How to fix

1. **Recompile** the model from the Python source: `thx.compile(model, "model.thx")`.
2. If you received the artifact from an external source, download it again. Verify its checksum against the published value.
3. Never attempt to edit `.thx` files manually. They are sealed artifacts, not configuration files.

## Example

```
E0009: artifact integrity check failed (CRC32 mismatch)
Why: the artifact file was corrupted after it was compiled.
Fix: recompile or re-download the artifact.
Docs: https://docs.thrindex.com/errors/E0009
```

## Note on intentional modification

If you need to change model parameters (weights, threshold, tau\_mem), you must do so in Python and recompile. The `.thx` artifact is a sealed, versioned record of a specific model state. It is not a mutable configuration file.