Hostinger Horizons: Troubleshooting Supabase

Common Issues and Field-Tested Solutions

Supabase & authentication problems

These are the most frequent issues.

Typical root causes

Wrong Project URL or Anon/Public key

New/duplicate Supabase clients created with placeholder values

Missing Auth Providers (e.g., Email not enabled)

CORS misconfiguration

Row Level Security (RLS) blocking reads/writes

Expired invites/secrets after reconnecting projects

Do the following:

Use the client file that comes with your project: If you already have a file called customSupabaseClient.js, keep using it. Don’t create new ones like supabase.js or supabaseClient.js with example or placeholder data.

Check your project settings in Horizons: Make sure the Project URL and Public/Anon key match exactly with your Supabase project settings.

Set up sign-in options in Supabase. Go to Supabase → Auth → Settings. Turn on Email login first, and add other sign-in methods (like Google) if you need them.

Add at least one test user: Either create a new one or make sure an existing test account works.

Allow your app’s URLs: In Supabase → Auth → URL Configuration, add both your preview and live (production) links.

If you’re using Row Level Security (RLS): Double-check that your rules allow the actions your app is trying to do.

When you update keys or URLs: Redeploy your app so the changes take effect.

If Horizons added extra Supabase files by mistake: Go back to the version before those changes, then use this prompt: “Use customSupabaseClient.js for all Supabase calls. Remove any duplicate clients and update imports accordingly.”

Signup error caused by a timing issue in the database

When a user signs up, enters their details, and clicks Confirm, they might see an RLS violation error in the console. This happens because the app tries to update the database before the user is fully authorized. Horizons assumes the user is logged in immediately after signup, but with email verification, authorization only happens after they sign in.

How to fix:

Instruct Horizons to update the signup and login flow. For example, you can use a prompt like this: “Move initial database manipulation logic from sign up logic to initial sign in. All database manipulation requests that are protected by authorization RLS must be respected and moved to flow where users are authorized – signed in.“

The console error usually shows which database table caused the issue. Include that table name in your prompt to get more accurate results from Horizons.

Supabase changing browser tabs causes website navigation

When a user switches browser tabs and returns to the app, they might see a different page than the one they left. This likely happens because of how useEffect, visibilitychange, and Supabase session handling work. When the tab is reopened, the app checks for an active session before Supabase confirms it, so it mistakenly thinks the user isn’t logged in and redirects them to the home page.

Ask Horizons to refactor the Supabase logic that uses the visibilitychange browser event to handle authentication sessions. For example, you can use a prompt like this: “Update Supabase logic that is using `visibilitychange` to check for authentication state. Make sure the user session is fully acknowledged before redirecting the user to the root route.”

Missing Supabase Credentials

Every action triggers an error indicating a missing API key or Supabase URL.

How to fix

Disconnect and reconnect your Supabase project. This will re-upload the Supabase API file and automatically add the API key and URL.

Sometimes issues can’t be reproduced or the steps aren’t clear, but logs are saved and can often help identify the problem. Be sure to select the correct timestamp when reviewing them.

Sandbox or Preview fails to start, hangs, or doesn’t finish building

Typical root causes

Heavy or unsupported packages causing npm install to hang
AI-made edits to critical configuration files (like vite.config.js or package.json)
Version conflicts between dependencies

Do this

Don’t manually edit vite.config.js (and avoid asking the AI to). If it was changed, revert to the last working message.
Avoid heavy/complex packages that often stall installs. If builds started failing after adding one, remove it and try again.
If dependencies won’t resolve, use this prompt: “Resolve dependency conflicts without modifying vite.config.js. Keep only the essential packages. Prefer stable versions and remove unused dependencies.”
If Preview is still stuck after reverting and trimming deps, use “Ask to Fix” once, then capture logs and contact support (include your project URL and the time the failure occurred).

Dependency and version conflicts

The issue appears when npm install never finishes and shows “dependency tree” or peer-dependency errors.

Pin stable library versions instead of using broad ranges.
Remove or replace problematic packages, and re-run Ask to Fix to rewrite imports.
If the AI added a tool or plugin that changed your build setup (for example, a PWA integration modifying Vite), revert those changes and ask it to add the feature without altering the core build settings.

Temporary global or infrastructure incidents

Sometimes external services (e.g., auth or backends) or internal infrastructure can cause temporary failures.

Do this

If the logs show external service outages or timeouts, try again later.
Avoid making major or destructive changes during incidents. Capture the logs and use Ask to Fix once services have recovered.