Databricks App suddenly unable to load valid Jupyter notebook

jjjjjahs — Thu, 10 Sep 2026 14:22:00 GMT

Hello Databricks Support,

I am experiencing an issue with a Databricks App that was previously working correctly.

The App has recently started failing when trying to load one of the Jupyter notebooks in its source directory

Failed 11 minutes ago: Error downloading source code. Error: error updating files: failed to download notebook : The Jupyter file may not be a valid notebook or may be an unsupported version.

The important point is that the notebook can still be accessed/downloaded successfully from the Databricks Workspace folder, and I can open the downloaded .ipynb file normally. The notebook itself was also working perfectly through the Databricks App before this issue started.

Could you please investigate why the App's source-code synchronization/download process is now rejecting this notebook?

Thank you,
Kiia

Re: Databricks App suddenly unable to load valid Jupyter notebook

SumeshKashyap — Thu, 10 Sep 2026 16:55:36 GMT

That specific error — "error downloading source code... may not be a valid notebook or may be an unsupported version" — comes from the Apps source-sync step's nbformat validation, which is stricter than the normal Workspace notebook viewer/downloader. A few things commonly trigger it even though the notebook opens fine elsewhere:

- nbformat/nbformat_minor mismatch — if the notebook was last touched by an external tool (VS Code, JupyterLab, an export pipeline) it may have bumped nbformat_minor to a version the Apps sync parser doesn't recognize, even though the classic notebook viewer is more lenient.

- Non-standard cell metadata or outputs — large/binary outputs (embedded images, widgets) or custom metadata keys can trip a stricter JSON schema check.

- Encoding — a BOM or non-UTF-8 byte in the file (especially if it was ever edited outside Databricks) can cause this.

Quickest way to isolate it: download the .ipynb, run "jupyter nbconvert --to notebook --clear-output <file>.ipynb -o cleaned.ipynb" (normalizes nbformat and strips outputs/metadata), re-upload the cleaned version, and point the App at that. If that fixes it, the culprit was stale metadata rather than content. If it still fails on a freshly-normalized file, that's worth a support ticket — it'd point to a regression in the App's sync step rather than the notebook itself.

topic Databricks App suddenly unable to load valid Jupyter notebook in Administration & Architecture

Databricks App suddenly unable to load valid Jupyter notebook

Re: Databricks App suddenly unable to load valid Jupyter notebook