> ## 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.

# Tier 3: Time-Travel

> Interactive debugging and non-destructive simulation.

Tier 3 is the ultimate investigation path, turning Prism into a full interactive debugger for the Stellar network.

## Interactive Debugging

Set breakpoints on:

* **Function Entry/Exit**: Stop when a specific contract function is called.
* **Storage Access**: Break when a specific ledger key is read or written.
* **Budget Thresholds**: Trigger a break when CPU or memory usage exceeds a limit.

Once a breakpoint is hit, you can step through execution one host call at a time.

## What-If Mode

The What-If engine lets you modify inputs and re-simulate:

* **Modified Arguments**: "Would it have worked if I passed 10 instead of 5?"
* **State Patching**: "What if the balance was already 100 XLM?"
* **Resource Limits**: "How much budget would I need for this to succeed?"

Prism runs both the original and modified execution and shows you a side-by-side diff of where they diverge.