headquarter/openspec/changes/instance-proxy/tasks.md

1. Backend - Proxy Endpoint

• 1.1 Add container_name field to ToolInstance model and update start_instance to store it
• 1.2 Create proxy endpoint /instances/{id}/proxy/{path:path} in tool_instances.py
• 1.3 Implement HTTP forwarding using httpx with streaming support
• 1.4 Add ownership check before proxying
• 1.5 Add WebSocket upgrade support for the proxy endpoint
• 1.6 Handle response header forwarding (Content-Type, cookies, etc.)

2. Backend - Instance URL Update

• 2.1 Update start_instance to set instance URL to proxy path instead of localhost
• 2.2 Ensure container_name is captured during start

3. Frontend - Update Instance Links

• 3.1 Update InstanceList "Open" button to use proxy URL
• 3.2 Update SessionsPage "Open" button to use proxy URL
• 3.3 Ensure URLs open in new tab

4. Testing & Quality

• 4.1 Test proxy with code-server instance
• 4.2 Verify WebSocket features work (terminal inside code-server)
• 4.3 Run quality gates (ruff, mypy, typecheck, lint, build)
• 4.4 Deploy and test end-to-end