---
title: MARKLESS_ASYNC_BOUNDARY_REQUIRED
description: "The markup reads an async computed() outside an @try block."
sidebar: { hidden: true }
search: { keywords: ["ASYNC_BOUNDARY_REQUIRED","async boundary required","markless error"] }
pagination: false
---

**Error** from the compiler, while it builds your `.tsrx` files.

## What happened

An async `computed()` can still be loading, or it can fail. The page needs to know what to show in both cases.

Markless prints the message, the reason, and a suggestion:

```text
MARKLESS_ASYNC_BOUNDARY_REQUIRED: Cannot read <computedLabel> "<source>" outside @try/@pending/@catch. Wrap the read in an async boundary.
Async computed values can be pending or rejected during initial render and resume. The runtime needs an explicit TSRX async boundary to render pending and error UI.
Wrap this template read in @try with @pending and @catch branches, or read a sync computed that is already guarded by an async boundary.
https://markless.dev/errors/MARKLESS_ASYNC_BOUNDARY_REQUIRED
```

Words in angle brackets change from case to case.

## How to fix it

Put the read inside `@try`, with a `@pending` branch for loading and a `@catch` branch for failure.

```tsrx
@try {
	<p>{details.title}</p>
} @pending {
	<p>Loading</p>
} @catch {
	<p>Could not load</p>
}
```

## Where it comes from

`@markless/compiler` raises this code. Source:

- [packages/compiler/src/passes/semantic-graph/diagnostics.ts](https://github.com/compiled-run/markless/blob/main/packages/compiler/src/passes/semantic-graph/diagnostics.ts)

Read [how to read a Markless error](/tooling/diagnostics), or go back to [all error codes](/errors).