Flags worked in local but not in prod

[naqi]

Thank you for building this library. I had a special use case and this fit it perfectly! The documentation and example have been super helpful in getting this implemented in a day.

Having said that it took an other day to get it working in our production env. I enabled toolbar for preview and prod builds. Browser extension is installed and I am logged in to my Vercel account. I only have one Vercel account so there was no chance I would be signed in to wrong account.

After redeploy, I started seeing the toolbar. However, flags explorer kept showing blank slate. Digging deeper I noticed that Flags Endpoint was getting 401 errors in production deployment.

When making the same call from a curl request I was getting 200.

curl --location 'https://example.com/.well-known/vercel/flags' \
--header 'Authorization: Bearer token_extracted_from_other_request'

Today I noticed a setting in the Toolbar which seemed odd to me since I had already enabled toolbar.

After tapping it, I got a list of domains for my deployment. Once I selected a domain I can now see my feature flags.

Is this expected behavior?

[naqi]

Another thing to note. Flag Explorer seems to only work with *.vercel.app domains. I can enable it on custom domain but I am seeing the same behavior. 401s for Flags Endpoint and empty state for Flags Explorer

[WITS]

Hi @naqi! Can you share the domain where you were experiencing this issue? The Flags Explorer is not limited to *.vercel.app domains, so I suspect there is another issue at play here

[naqi]

@WITS Sure, our custom domain is https://app.staging.makeswift.com

[naqi]

There is some update.

After clearing my cookies, for all time, in chrome. I am now able to see the feature flags. I am guessing some cookie was the cause?

However, when I tried a fresh browser Firefox it does not work. I can't even get the toolbar to show up. One of my team members is running developer version of Firefox and that seems to be loading the toolbar.

[WITS]

I'm happy to hear that it's mostly working now. 🙂

I don't believe that we have anything at a platform level that would behave differently for the flags endpoint depending on cookies. Is it possible that your application uses middleware, redirects, or rewrites that could intercept requests to the flags endpoint?

I'll share the Firefox issue with our team so we can look into it. Thank you for letting us know!