Remote MCP OAuth browser flow never triggered - Datadog MCP silently fails to authenticate

Description

When a remote MCP server requiring OAuth 2.1 + PKCE is configured (Datadog), OpenCode registers a client ID successfully and writes it to mcp-auth.json, but never initiates the browser-based authorization flow.

The MCP toggles to "loading" then "failed" with:

No auth URL surfaced to the user.
No browser window opened.
No error logged.

The mcp-auth.json entry is left with a clientId but no tokens. For comparison, the Atlassian remote MCP (same type: remote config) completes OAuth successfully and logs transport=StreamableHTTP connected with a full token set.

Plugins

[email protected]
@slkiser/[email protected]

OpenCode version

1.2.15

Steps to reproduce

Add a remote MCP server that requires OAuth to opencode.json:

{
  "mcp": {
    "datadog": {
      "enabled": true,
      "type": "remote",
      "url": "[https://mcp.datadoghq.eu/api/unstable/mcp-server/mcp?toolsets=core,apm,software-delivery](https://mcp.datadoghq.eu/api/unstable/mcp-server/mcp?toolsets=core,apm,software-delivery)"
    }
  }
}

This issue might be a duplicate of existing issues. Please check:

Remote MCP OAuth: browser never opens for re-authentication after session loss #16893: Same symptom — remote MCP OAuth browser flow never opens, mcp-auth.json has clientId but no tokens. That issue focuses on re-authentication after session loss, but the root cause may be the same.

If your issue is distinct (i.e., the browser flow never triggered even on the very first attempt, not just after a restart), please add a note clarifying that difference so this can be tracked separately.

I am working on this issue and now it initiate the browser-based authorization flow and saving the codeId and token in mcp-auth.json file as well but the screen is showing the flow is done but the terminal showing
invalid_grant - Invalid authorization code or code verifier. idk why it is happening but /mcp showing the connected to datadog mcp. Should I raise PR?

Okay so I tried reproducing and immediately hit the same issue as u, I made a pr to make our error handling better but even when it's better their error isnt rlly enough.

I did end up figuring out it was because the mcp urls need to be very specific even if u select a different region when doing the oauth flow.

 "datadog": {
      "type": "remote",

      // The url I copied from the docs:
      // "url": "https://mcp.datadoghq.com/v1/mcp",
      "url": "https://mcp.us5.datadoghq.com/v1/mcp",
      "enabled": true,
    },

I copied that first url from docs and kept hitting the issue, but I changed to the second one (where my account is based) and it fixed it

Hope this helps

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Remote MCP OAuth browser flow never triggered - Datadog MCP silently fails to authenticate #18130

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Remote MCP OAuth browser flow never triggered - Datadog MCP silently fails to authenticate #18130

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OpenCode version

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github-actions commented on Mar 18, 2026

Vishal2002 commented on Mar 25, 2026

rekram1-node commented on Jun 27, 2026

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