Public HTTPS URLs per sandbox

[nthh]

Summary

Give each sandbox an automatic public HTTPS endpoint so users can preview web apps, share demos, and expose services without manual port forwarding.

User stories

• "I'm building a React app in the sandbox and want to preview it in my browser"
• "I want to share a link to my running app with a teammate for feedback"
• "I'm developing an API and want to test it from Postman / curl externally"

Current state

The server proxies agent dashboard ports via /proxy/{id}/{path}, but this is:

• Authenticated (session owner only)
• Single port per agent (hardcoded in agent.json)
• Server-mediated (all traffic flows through FastAPI)
• Not shareable

Proposed behavior

Each sandbox gets a URL like {session-id}.sandbox.remolt.dev that routes directly to the pod. Any port the user exposes inside the sandbox is accessible.

Current:  Browser → remolt.dev/proxy/{id}/{path} → server → pod:port
Proposed: Browser → abc123.sandbox.remolt.dev → Cloudflare/Ingress → pod:port

Implementation options

1. Cloudflare Tunnel per pod (simplest for current infra)

• Sidecar container runs cloudflared tunnel in each pod
• Registers {session-id}.sandbox.remolt.dev with Cloudflare
• Auto-TLS, no ingress controller needed
• Teardown on pod destruction

2. Wildcard Ingress + cert

• Wildcard DNS *.sandbox.remolt.dev → Ingress controller
• Ingress rule per session, created/deleted with pod lifecycle
• Wildcard TLS cert (Let's Encrypt or Cloudflare Origin CA)

3. Server proxy enhancement (least infrastructure change)

• Extend current /proxy/{id}/{path} to support any port, not just agent dashboard
• Add optional public/shareable mode (token-gated or fully public)
• Still server-mediated but no DNS/ingress changes needed

Considerations

• Security: should sandbox URLs be public by default, or require explicit opt-in?
• Port discovery: how does the user specify which port(s) to expose?
• Auth: public links vs. token-gated links vs. session-owner-only
• Bandwidth: public URLs could be abused — tie into existing bandwidth limiting
• Cleanup: tunnel/ingress rules must be torn down when pod is destroyed

Competitive context

• Shellbox gives every box automatic HTTPS + TLS
• GitHub Codespaces has port forwarding with shareable URLs
• Gitpod has public/private port visibility controls