15.7A Worked Example: The BiDi Proxy Pattern (Vibium)

The cleanest illustration of building on BiDi is Vibium (see the case study in Competitive Landscape): its clicker binary is a BiDi proxy that sits between clients and Chrome:

Client ──WebSocket──► Clicker Proxy ──WebSocket──► Chrome
                      │
                      ├── Forwards standard BiDi commands
                      ├── Intercepts vibium:* extension commands
                      ├── Runs actionability checks via script.callFunction
                      └── Performs clicks via input.performActions

The proxy pattern means:

• Clients don't need to know Chrome's BiDi endpoint directly
• Custom commands (vibium:click, etc.) are transparent to the client
• The proxy can add features (auto-wait, screenshots) without changing the protocol