> For the complete documentation index, see [llms.txt](https://docs.buzzy.buzz/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.buzzy.buzz/troubleshooting/app-and-runtime-issues.md).

# App and Runtime Issues

Runtime issues happen when an app is previewed, tested, or opened by a user. They are usually caused by missing or mismatched app configuration, data context, app actions, or custom runtime code.

## Common Symptoms

* app URL opens but shows a named error
* preview or published app shows a blank screen
* navigation opens the wrong screen or cannot find the screen
* view, form, filter, or field cannot find its datatable or field
* action fails or does not pass the current row
* Code Widget, Function, or runtime action throws an exception

## Start With Error Codes

If the app shows a named error, go to [App Error Codes](/troubleshooting/app-error-codes.md). Error codes are grouped into:

* app and route errors
* datatable and field errors
* component and action errors
* runtime exceptions

## Fast Triage

1. Open the app from the Dashboard to rule out stale URLs.
2. Check what changed recently: deleted screens, renamed fields, regenerated data model, Figma publish, new action, new widget, or new function.
3. Open the affected screen in the editor.
4. Use [In-App Debugging](/troubleshooting/in-app-debugging.md) to inspect screen context, selected node, bindings, actions, fields, display formulas, and runtime row data.
5. Check whether a detail or edit screen expects the previous action to pass the current row.
6. After fixing the issue, preview again and rerun relevant [Tests](/the-building-blocks/release-tests.md).

## Related Guides

* [App Error Codes](/troubleshooting/app-error-codes.md)
* [In-App Debugging](/troubleshooting/in-app-debugging.md)
* [Tests](/the-building-blocks/release-tests.md)
* [Integration Issues](/troubleshooting/integration-issues.md)