> For the complete documentation index, see [llms.txt](https://shinkalabs.gitbook.io/hub/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://shinkalabs.gitbook.io/hub/andromeda/guides/simulate.md).

# Dry-run / Simulate

Before you commit a transaction, you can simulate it and get a structured diagnostic back. This uses Solana's `simulateTransaction` under the hood and turns the raw result into something you can act on.

{% hint style="info" %}
Exact request and response bodies are in the [OpenAPI spec](https://api.andromedainfra.pro/openapi.json).
{% endhint %}

## What you get

The diagnostic includes:

* **Would-succeed flag.** Whether the transaction would land.
* **Failure boundary.** If it would fail, where: which instruction, and the error.
* **Estimated compute units.** So you can size a compute budget.
* **Emitted events.** The events the transaction would emit (useful to confirm it does what you expect).
* **Full logs.** The raw program logs from the simulation.

## When to use it

* Before a high-value sign, to confirm the destination program accepts the transaction.
* When debugging a policy rejection: the failure boundary tells you which check failed.
* To estimate compute units for a batch before packing it. See [Auto-batching](/hub/andromeda/guides/batching.md).
* In CI, to catch a regression before it hits the chain.

## What it does not do

* It does not change state. Nothing is broadcast.
* It is a point-in-time estimate. State can change between simulation and submission (a slot rolls, a price moves, a presignature is consumed), so a successful simulation is not a guarantee. For anything sensitive to timing, simulate close to when you submit.

## Combine it

* With [Idempotency keys](/hub/andromeda/guides/idempotency.md): simulate, then submit with an idempotency key so a retry of the real submission is safe.
* With policy templates: simulate against a dWallet behind [`oracle-conditional`](/hub/andromeda/guides/deploy-policy/oracle-conditional.md) or [`time-lock`](/hub/andromeda/guides/deploy-policy/time-lock.md) to see whether the guard would let it through right now.


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