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<@ULVA73B9P> I have a slack incoming webhook block. When I use this block to send slack notification from state change hook, its working fine. However if I select this same block in an automation to send slack notification in Action step, automation action fails with the following error message:
```"reason": "The notification block was invalid: KeyError(\"No class found for dispatch key 'slack-incoming-webhook' in registry for type 'Block'.\")"```
Is it a bug or I am missing something here?

:white_check_mark: thought for 142.3 seconds

What you’re seeing is *expected behavior*, not usually a user mistake.

*Why it works in a state change hook but fails in an automation*

- *State change hooks* run in the environment where your flow code is running.
- *Automations* run in the Prefect server/Cloud automation environment.

Your block is the *integration-provided* Slack block with dispatch key `slack-incoming-webhook`, which comes from the `prefect-slack` package. In the automation runtime, Prefect tries to reconstruct that block type and fails because that class is not available there:

```"The notification block was invalid: KeyError("No class found for dispatch key 'slack-incoming-webhook' in registry for type 'Block'.")"```

So the issue is basically:

- local flow environment has `prefect-slack` installed -&gt; hook works
- automation runtime does *not* have that block class registered -&gt; automation fails

*Recommended fix*

Use the *built-in* Prefect notification block instead of the `prefect-slack` integration block for automations:

- built-in block slug: `slack-webhook`
- integration block slug: `slack-incoming-webhook`

The built-in `SlackWebhook` block is supported for notification actions and does not depend on `prefect-slack` being installed in the automation runtime.

*What to do*
1. Create a new block using the built-in Slack webhook notification block
2. Select that new block in your automation action
3. Keep your existing `prefect-slack` block for flow code/hooks only if you want

*Docs*
- <https://docs.prefect.io/v3/concepts/automations/#sending-notifications-with-automations|Automations: sending notifications>
- <https://docs.prefect.io/v3/how-to-guides/workflows/state-change-hooks/|State change hooks>
- <https://docs.prefect.io/integrations/prefect-slack/#comparing-slackwebhook-blocks|Comparison of the two Slack webhook block types>
- <https://docs.prefect.io/v3/concepts/blocks/#pre-registered-blocks|Pre-registered blocks>

*Short version*

You’re likely not missing anything — you’re using the *wrong Slack block type for automations*.  
For automation notification actions, prefer the built-in `slack-webhook` block instead of `slack-incoming-webhook`.

If you want, I can also show you exactly how to identify which Slack block you currently saved and how to recreate it correctly in the UI.