Function call_inference 

pub fn call_inference(
    upstream_json: String,
    url: String,
    client: Arc<Client>,
    auth: Option<String>,
    chunk_timeout: Duration,
) -> impl Stream<Item = Result<String, ExecutorError>> + Send + 'static

Step 2 — Call the LLM inference backend; yields raw SSE lines (data: …).

Always requests stream=true upstream. Stops on [DONE].

Errors

Each stream item is Result<String, ExecutorError>. The stream yields Err on:

• ExecutorError::LLMTransport — connect timeout (504) or connection failure (502)
• ExecutorError::LLMRequest — non-2xx HTTP status from the backend
• ExecutorError::NetworkError — network failure while reading the response body