---
title: MARKLESS_ARTIFACT_CHILD_PROP_NOT_BUILD_KNOWN
description: "Delegate child prop is not build-known: a Markless compiler error."
sidebar: { hidden: true }
search: { keywords: ["ARTIFACT_CHILD_PROP_NOT_BUILD_KNOWN","artifact child prop not build known","markless error"] }
pagination: false
---

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

## What happened

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

```text
MARKLESS_ARTIFACT_CHILD_PROP_NOT_BUILD_KNOWN: MARKLESS_ARTIFACT_CHILD_PROP_NOT_BUILD_KNOWN: <<componentName>> prop <prop> must be a build-known static value. Runtime component execution is not a fallback.
A delegate is rendered once at build time, so every prop it reads must be a value the compiler can read at build time.
Pass a static value, or compose the child as TSRX source.
https://markless.dev/errors/MARKLESS_ARTIFACT_CHILD_PROP_NOT_BUILD_KNOWN
```

Words in angle brackets change from case to case.

## How to fix it

Start with the suggestion in the message above.

This page has no guide yet. [Help write it](/contributing/improve-these-docs).

## Where it comes from

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

- [packages/compiler/src/passes/link/delegate-children.ts](https://github.com/compiled-run/markless/blob/main/packages/compiler/src/passes/link/delegate-children.ts)

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