Improve DX: warn or block invite emails when Site URL is not configured

[iddi5504]

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Describe the issue

Invite confirmation emails fall back to localhost when Site URL is not configured .
Invite confirmation emails sent from Supabase Studio can contain broken magic links that use http://localhost:3000 as the base URL.

This happens when the project Site URL is not configured in Authentication settings. Supabase Auth silently falls back to localhost, resulting in unusable invite links for end users.

Related to #41321.

To Reproduce

Steps to reproduce the behavior, please provide code snippets or a repository:

1. Go to authetication, then users
2. Click on invite user
3. Type email and invite
4. After invite user
5. Check email, The link has localhost as the baseurl

Actual behavior

The confirmation email contains a link similar to:

http://localhost:3000/#access_token=...&type=signup

This link is not reachable for the invited user and results in a failed connection.

Expected behavior

One of the following would improve the experience:

• Prevent sending invite confirmation emails when Site URL is not configured
• Show a warning in Supabase Studio if Site URL is unset or invalid
• Require Site URL during project setup
• Provide clearer feedback that magic links depend on Site URL

Screenshots

If applicable, add screenshots to help explain your problem.

System information

• OS: [macOS]
• Browser (if applies) [chrome]
• Version of supabase-js: [e.g. 6.0.2]
• Version of Node.js: [e.g. 10.10.0]

Additional context

Related to #41321

Invite confirmation emails use the magic link flow and rely on Auth configuration.

From the email template:

You have been invited to create a user on {{ .SiteURL }}
<a href="{{ .ConfirmationURL }}">Accept the invite</a> 

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🔗 Similar Issues

Possible Duplicates

• ISSUE-39718

Related Issues

• Auth: Password Reset and Invite Links Use localhost:3000 in Production Environment #39718
• Localhost redirect URLs not respected in resetPasswordForEmail #36640
• Bug: Password Reset and Magic Links Generating Empty URLs (No Tokens) #40928
• Send Email Auth Hook site_url is the Supabase project URL and not the configured SiteUrl #36565

👤 Suggested Assignees

• vduggen
• brondibur
• Chahdhammami
• JPTeasdale

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[ShaikAfreed098]

When i try the same thing with my Supabase account and when i tried to invite other member to my project as a developer role and it worked it just send the email to other person and he also joined my project without any kind of issue..