CORS problem due to missing min_zoom in layer water about tileserver HOT 3 OPEN

That's odd! Can you give an example tile coordinate (preferably with a public URL) for debugging, please? We're also happy to accept PRs :)

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Sorry, but I'm firewalled. It was tileserver with imported https://download.geofabrik.de/europe/poland-latest.osm.pbf tested using nginx, apache2 to display the map (all sitting on the same machine).
As I see the problem is when assertion happens, there is an error generated, so the function that generates the header is omitted.
Commenting out quoted lines masks the problem allowing tileserver to work properly.

It was looking to be a CORS misconfiguration of apache or nginx forcing me to stray...

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If I'm understanding werkzeug correctly, it looks like it might be difficult to add headers to its exceptions, unfortunately. We used to run tileserver behind a proxy, would it be possible for you to do the same? That way you can ensure that CORS headers are present on all the responses.

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