pub fn detect_request_surface(body: &Json) -> Option<ProviderSurface>Expand description
Detect the request surface from a raw request body by top-level key.
Priority: OpenAI Responses (input/instructions) > Anthropic Messages
(system) > OpenAI Chat (messages). None when no key matches or body
is not an object. This is a best-effort heuristic: an Anthropic request that
omits the optional top-level system is indistinguishable from OpenAI Chat
and classifies as OpenAIChat.