GetBusbar/busbar ? reverse-engineered prompt

Build me a self hosted AI gateway that I can point my existing SDKs at by changing the base URL and key.

I want one fast Rust binary that sits between my app and model providers, handles OpenAI, OpenAI Responses, Anthropic, Gemini, Cohere, and Bedrock Converse, and keeps the provider credentials at the boundary instead of in my app. It should support routing a request to different providers based on a simple pool name, with real failover if the first provider is unavailable, plus basic circuit breaker and load balancing behavior.

It should work with streaming too, keep the same request and response shape where possible, and let me control budgets, policy, and what destinations are allowed. Please also include audit and execution evidence so I can see what happened after a call. If you need to check any current SDK or provider docs, look them up online first.