Where does the bug appear (feature/product)?
Cursor IDE
Describe the Bug
Cursor’s OAuth redirect_uri is using a fixed localhost port (8787) that conflicts with quite a few things that might be running on a developer machine: Dask’s web interface, Cloudflare’s wrangler dev, probably some others. This breaks the OAuth flow if one of those apps happens to be running.
as discussed here: OAuth redirect URI changed from cursor:// to http://localhost for Streamable HTTP MCP - #13 by mohitjain
Steps to Reproduce
Add a new MCP server that uses OAuth.
During the OAuth exchange, after consent is granted, the authorization server will redirect back to http://localhost:8787. If another app is running, it will typically display a 404 not found error in the browser.
Expected Behavior
Cursor could use a random free high port. This is allowed by RFC 8252, and seems to be what most tools do:
The authorization server MUST allow any port to be specified at the
time of the request for loopback IP redirect URIs, to accommodate
clients that obtain an available ephemeral port from the operating
system at the time of the request.
Operating System
MacOS
Version Information
Version: 3.11.13 (Universal)
VS Code Extension API: 1.125.0
Commit: 3f21b08f0b436a07be29fbfe00b304fa15553350
Date: 2026-07-10T01:45:28.254Z
Layout: Agent Window
Build Type: Stable
Release Track: Default
Electron: 40.10.3
Chromium: 144.0.7559.236
Node.js: 24.15.0
V8: 14.4.258.32-electron.0
xterm.js: 6.1.0-beta.256
OS: Darwin arm64 25.5.0
Does this stop you from using Cursor
No - Cursor works, but with this issue