Troubleshooting Supabase Mcp OAuth (Experimental) Issues

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Hey guys! Ever run into a snag where something that should work just...doesn't? Today, we're diving deep into a particularly frustrating issue: the experimental mcp OAuth not playing nice with Supabase. If you've been banging your head against the wall trying to figure this out, you're in the right place. We'll break down the problem, explore the potential causes, and, most importantly, arm you with the knowledge to troubleshoot and (hopefully!) fix it.

Understanding the Problem: mcp OAuth and Supabase

So, what exactly is this mcp OAuth thing, and why is it important for Supabase? Let's break it down. MCP, or Management Control Plane, is essentially the behind-the-scenes system that lets you manage your Supabase project. OAuth (Open Authorization) is a standard protocol that allows applications to access resources on behalf of a user without needing their credentials. Think of it as a secure way to grant access without handing over your password.

The experimental mcp OAuth in the Codex CLI (which, in this case, is version 0.45.0) should allow you to seamlessly connect to your Supabase project. You configure your codex settings with your Supabase URL and project reference, and then use the codex mcp login supabase command. This should kick off an OAuth flow, where you authorize the connection in your browser.

However, as we see in the reported issue, things don't always go as planned. The user encountered a HTTP 404 Not Found error when opening the authorization URL provided by Codex. This is a major roadblock, preventing them from connecting to their Supabase project via mcp. This error typically means that the resource being requested (in this case, the authorization endpoint) cannot be found on the server. It’s like trying to find a specific street address, but the street simply doesn’t exist.

Decoding the Error Message and the Setup

Let’s dissect the error message and the user's setup to understand what might be going wrong. The error message, Dynamic registration failed: Registration failed: HTTP 404 Not Found, immediately points to a problem with the OAuth flow's registration process. Dynamic registration is a feature where the client (Codex CLI, in this case) attempts to register itself with the authorization server (Supabase) on the fly. If this registration fails, the entire OAuth dance can’t even begin.

The configuration provided by the user looks like this:

experimental_use_rmcp_client = true
[mcp_servers.supabase]
url = "https://mcp.supabase.com/mcp?project_ref=xxxxxxxxxx&read_only=true"

This configuration tells Codex to use the experimental mcp client and specifies the URL for the Supabase mcp endpoint. The project_ref is a unique identifier for the Supabase project, and read_only=true indicates that the Codex client should only have read access. The user then attempts to log in using the command codex mcp login supabase, which triggers the OAuth flow.

The authorization URL generated by Codex looks something like this:

https://mcp.supabase.com/authorize?project_ref=xxxxxxxxx&read_only=true&response_type=code&client_id=mcp-client&state=tshk3Txx-eZzGANecv2EaJZDQ&code_challenge=xxxxxx&code_challenge_method=S256&redirect_uri=http%3A%2F%2F127.0.0.1%3A49387%2Fcallback

This URL contains all the necessary parameters for the OAuth flow, including the project_ref, response_type, client_id, state, code_challenge, code_challenge_method, and redirect_uri. However, when the user opens this URL in their browser, they encounter a 404 Not Found error. This suggests that the authorization endpoint (/authorize) is not available at the specified URL.

Potential Culprits and Troubleshooting Steps

Okay, so we've established the problem. Now, let's put on our detective hats and explore the possible reasons behind this 404 Not Found error. Here’s a breakdown of potential causes and how to investigate them:

1. Incorrect Supabase URL or Project Reference

This is the most common suspect. Even a tiny typo in the URL or project_ref can lead to a 404 error. Double-check, and then triple-check that the URL and project_ref in your Codex configuration are exactly correct. Copy and paste them directly from your Supabase dashboard to avoid any errors.

  • How to check: Go to your Supabase project dashboard and verify the project reference. Ensure the URL matches the expected format for your Supabase instance.

2. Issues with Supabase's mcp Endpoint

It's possible (though less likely) that there's a problem on Supabase's end. The mcp endpoint might be temporarily unavailable, or there might be an issue with their OAuth configuration. It’s always good to rule out the possibility of a server-side issue.

  • How to check: Check Supabase's status page for any reported outages or issues. You can also try accessing other parts of your Supabase project to see if the problem is isolated to the mcp endpoint.

3. Codex CLI Configuration Errors

There might be something amiss in your Codex CLI configuration. Perhaps there's a syntax error, or a setting that's interfering with the OAuth flow. Sometimes, even a seemingly minor configuration mistake can cause major headaches.

  • How to check: Carefully review your codex configuration file. Ensure that all the settings are correctly formatted and that there are no conflicting options. Pay special attention to the experimental_use_rmcp_client setting, and make sure it's set to true if you're using the experimental mcp client.

4. Network Connectivity Problems

A network issue could prevent Codex from reaching the Supabase mcp endpoint. This could be a problem with your internet connection, your firewall, or some other network configuration.

  • How to check: Try accessing the Supabase mcp URL directly in your browser. If you can't reach it, there might be a network issue. Check your internet connection, firewall settings, and any other network configurations that might be interfering with the connection.

5. Redirect URI Mismatch

The redirect_uri in the authorization URL needs to match the one configured in your Supabase project settings. If there's a mismatch, the OAuth flow will fail. This is a critical security measure to prevent unauthorized access.

  • How to check: In your Supabase project settings, look for the OAuth configuration. Ensure that the redirect_uri listed there matches the one in the authorization URL generated by Codex. In this case it’s http://127.0.0.1:49387/callback.

6. Codex CLI Bug (Experimental Feature)

Since the mcp OAuth feature is marked as experimental, there's a chance that there's a bug in the Codex CLI itself. Experimental features are, by their nature, more prone to issues. It's a good idea to consider this possibility, especially if you've ruled out other causes.

  • How to check: Check the Codex CLI issue tracker for any reported bugs related to mcp OAuth. If you find a similar issue, you can add your experience to the discussion. If not, you might consider opening a new issue to report the bug.

7. Supabase OAuth Configuration Issues

There might be an issue with how OAuth is configured on the Supabase side. This could involve incorrect client IDs, secrets, or other OAuth-related settings.

  • How to check: Review your Supabase project's OAuth settings. Ensure that the client ID used by Codex is correctly configured and that there are no other issues with the OAuth setup.

Stepping Through the Troubleshooting Process

Okay, we've got a list of potential suspects. Now, let's talk about how to systematically investigate them. Here’s a step-by-step approach you can use:

  1. Verify the Supabase URL and Project Reference: This is the first and most crucial step. Double-check, triple-check, and even quadruple-check that the URL and project_ref in your Codex configuration are correct. Copy and paste them directly from your Supabase dashboard.
  2. Check Supabase's Status Page: Visit Supabase's status page to see if there are any reported outages or issues. This will quickly rule out any server-side problems.
  3. Review Codex CLI Configuration: Carefully examine your codex configuration file. Look for any syntax errors, typos, or conflicting settings. Pay close attention to the experimental_use_rmcp_client setting.
  4. Test Network Connectivity: Try accessing the Supabase mcp URL directly in your browser. If you can't reach it, investigate your network connection, firewall settings, and other network configurations.
  5. Check Redirect URI: Verify that the redirect_uri in the authorization URL matches the one configured in your Supabase project settings. This is a common source of OAuth errors.
  6. Consult Codex CLI Issue Tracker: Check the Codex CLI issue tracker for any reported bugs related to mcp OAuth. If you find a similar issue, contribute to the discussion. If not, consider opening a new issue.
  7. Review Supabase OAuth Configuration: Examine your Supabase project's OAuth settings. Ensure that the client ID used by Codex is correctly configured and that there are no other issues with the OAuth setup.

When to Ask for Help

Troubleshooting can be tricky, and sometimes you'll hit a wall. If you've tried all the steps above and you're still stuck, it's time to ask for help. Here are some places you can turn to:

  • Supabase Community: The Supabase community is a great resource for getting help. You can ask questions in their forums or Discord server.
  • Codex CLI Issue Tracker: If you suspect a bug in the Codex CLI, open an issue in their issue tracker. Be sure to provide detailed information about the problem, including the steps you've taken to troubleshoot it.
  • Stack Overflow: Stack Overflow is a popular question-and-answer site for developers. You can ask questions about Supabase, Codex CLI, or OAuth in general.

When asking for help, be sure to provide as much information as possible. This includes the error message you're seeing, your configuration settings, the steps you've taken to troubleshoot the problem, and any other relevant details. The more information you provide, the easier it will be for others to help you.

The Importance of Reporting Bugs

If you do encounter a bug, it's important to report it. This helps the developers fix the bug and improve the software for everyone. When reporting a bug, be sure to include the following information:

  • The version of Codex CLI you're using.
  • The operating system you're using.
  • The steps to reproduce the bug.
  • The expected behavior.
  • The actual behavior.
  • Any error messages you're seeing.

By providing this information, you'll make it easier for the developers to understand and fix the bug.

Conclusion: Persistence Pays Off

Dealing with OAuth and experimental features can be a real headache, but don't get discouraged! By understanding the problem, systematically troubleshooting, and leveraging available resources, you can often find a solution. Remember, persistence is key. Keep digging, keep asking questions, and you'll eventually crack the case. And who knows, you might even help improve the software for others along the way!

So, next time you're wrestling with mcp OAuth and Supabase, remember these tips and tricks. You've got this, guys! And happy coding!