> ## Documentation Index
> Fetch the complete documentation index at: https://prism-ddf93e61.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# What-If Engine

> Non-destructive re-simulation of transactions.

The What-If Engine allows developers to test hypotheses by modifying the inputs of a failed transaction.

## Input Patches

It supports patching four main categories:

1. **Function Arguments**: Modify the values passed to the contract.
2. **Auth Context**: Add or remove authorizations.
3. **Ledger State**: Change existing ledger entries before execution.
4. **Resource Limits**: Increase CPU/Memory/Footprint limits.

## Comparison Tracing

The engine runs both the original and the modified execution, producing a side-by-side trace that highlights the exact moment the results diverge.