Local development usually means localhost:3000, localhost:8080, and a mental map of which port belongs to which service. AI agents struggle with this. They cannot reliably track dynamic port assignments across restarts, and they cannot predict which port a framework will choose when you spin up a new service.
Portless replaces port numbers with stable .localhost URLs. Instead of http://localhost:3000, you get https://myapp.localhost. The tool handles TLS, port assignment, and framework-specific CLI flag injection so your services bind to the right port without manual configuration.
It hit 12,000 GitHub stars in days and ranked #3 on TypeScript trending. The reason is simple: it solves a coordination problem that gets worse as you add more services or more agents to your workflow.
Why Port Numbers Break Agent Workflows
Agents need predictable endpoints. When you ask an agent to "start the frontend and call the API," it needs to know where the API will be. If the API binds to a random port, the agent must parse logs, guess, or fail.
