finding-dev-server-url

Finding Dev Server URL

Detect which dev servers are running, what ports they're on, and open them.

How It Works

Cursor stores live terminal output in text files. Each terminal has a file at:

<terminals_folder>/<id>.txt

The terminals folder path is provided in your system context. Each file contains metadata (pid, cwd, last command) followed by the full terminal output.

Workflow

1. List All Terminals

ls <terminals_folder>/*.txt

2. Read Each Terminal's Metadata

Read the first ~10 lines of each terminal file to see:

pid — process ID
cwd — working directory
last_command — what's running (e.g. npm run dev, pnpm dev, python manage.py runserver)

Skip terminals where the last command is clearly not a server (e.g. git status, ls, cd).

3. Scan for Server URLs

Read the full content of terminals that look like they're running a server. Search for these patterns:

Framework	Pattern
Next.js	`Local: http://localhost:XXXX` or `▲ Ready`
Vite	`Local: http://localhost:XXXX/`
Create React App	`Local: http://localhost:XXXX`
Express	`listening on port XXXX` or `listening at http://...`
Django	`Starting development server at http://127.0.0.1:XXXX/`
Rails	`Listening on http://127.0.0.1:XXXX`
Flask	`Running on http://127.0.0.1:XXXX`
Go	`Listening on :XXXX` or `http server started on :XXXX`
PHP	`Development Server (http://localhost:XXXX) started`
Remix	`http://localhost:XXXX`
Astro	`http://localhost:XXXX`
Nuxt	`http://localhost:XXXX`

Regex to match most server output:

https?://(localhost|127\.0\.0\.1|0\.0\.0\.0)(:\d+)

Also check for standalone port patterns:

(listening|started|running|ready|serving).*(port\s*|:)\s*(\d{4,5})

4. Report

Print a summary:

Dev servers found:
  Terminal 1 (pid 12345) — npm run dev → http://localhost:3000 (cwd: /Users/me/app)
  Terminal 3 (pid 67890) — python manage.py runserver → http://127.0.0.1:8000 (cwd: /Users/me/api)

If no servers are found, say so and suggest starting one.

5. Open in Browser (Optional)

If the user wants to view the app, use Cursor's built-in browser:

browser_navigate → http://localhost:<port>

Then take a screenshot to confirm it's rendering:

browser_take_screenshot

Tips

If multiple servers are found, ask the user which one to open
If a terminal shows an error (e.g. EADDRINUSE, address already in use), report the conflict
If the server crashed (process exited), note that too — check for exit_code in the terminal file footer
Common default ports: Next.js (3000), Vite (5173), Django (8000), Rails (3000), Flask (5000), Go (8080)