Describe the bug

When using a custom async storage adapter (for Chrome extension with chrome.storage.local), the Supabase client crashes during initialization if the storage was recently cleared (e.g., after logout).

Instead of gracefully handling empty storage as "no session," the library throws an uncaught error in _initSupabaseAuthClient.

Environment:

• @supabase/supabase-js version: 2.x (bundled)
• Environment: Chrome Extension (Manifest V3)
• Storage adapter: Custom async adapter using chrome.storage.local

Custom Storage Adapter:
const chromeStorageAdapter = {
getItem: async (key) => {
return new Promise((resolve) => {
chrome.storage.local.get([key], (result) => {
resolve(result[key] ?? null);
});
});
},
setItem: async (key, value) => {
return new Promise((resolve, reject) => {
chrome.storage.local.set({ [key]: value }, resolve);
});
},
removeItem: async (key) => {
return new Promise((resolve) => {
chrome.storage.local.remove([key], resolve);
});
}
};

Library affected

supabase-js

Reproduction

No response

Steps to reproduce

1. Initialize Supabase client with custom async storage adapter
2. User logs in successfully (session stored)
3. User logs out - clear all Supabase keys from storage:
   await chrome.storage.local.remove(['sb--auth-token']);
4. Reload the page
5. Call createClient() again

Expected Behavior:

• createClient() should initialize successfully
• getSession() should return null (no session)
• App can show login screen

Actual Behavior:

• createClient() throws an error during _initSupabaseAuthClient
• App crashes

Error Stack Trace:
Uncaught (in promise) Error
at e (supabase.min.js:7)
at Fr (supabase.min.js:7)
at _initSupabaseAuthClient (supabase.min.js:7)
at Jr (supabase.min.js:7)
at e.createClient (supabase.min.js:7)

Workaround:
We wrapped createClient() in a try-catch and return null on failure, treating it as "not logged in":
function initSupabase() {
try {
return supabase.createClient(URL, KEY, {
auth: { storage: chromeStorageAdapter }
});
} catch (error) {
console.error('Supabase init failed:', error);
return null;
}
}

Suggested Fix:
The auth client initialization should handle empty/missing storage gracefully, treating it as "no existing session" rather than throwing an error.

System Info

OS: macOS (Darwin 25.0.0)
  Browser: Chrome (latest)
  Environment: Chrome Extension (Manifest V3)
  Node: N/A (browser-only)

Used Package Manager

npm

Logs

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Make sure this is a Supabase JS Library issue and not an issue with the Supabase platform. If it's a Supabase platform related bug, it should likely be reported to supabase/supabase instead.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.