---
title: MARKLESS_SYNC_POLICY_UNEXTRACTABLE
description: "Cannot extract synchronous event policy: a Markless compiler error."
sidebar: { hidden: true }
search: { keywords: ["SYNC_POLICY_UNEXTRACTABLE","sync policy unextractable","markless error"] }
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---

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

## What happened

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

```text
MARKLESS_SYNC_POLICY_UNEXTRACTABLE: `<source>` detaches <action> from the event, so the compiler cannot prove when the default action is cancelled for <attributeName>.
preventDefault() and stopPropagation() must run before lazy handler symbols load; a detached reference hides which action runs and under what condition.
Call it directly on the event parameter instead of detaching <action>.
https://markless.dev/errors/MARKLESS_SYNC_POLICY_UNEXTRACTABLE
```

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

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