Create a Stream Listener for a Module Output Field

Creates a listener that receives streamed content for a specific output field during run_stream(). This mirrors DSPy's StreamListener: attach a callback to the field you care about (e.g., "answer") and it fires as content for that field is produced — token by token when the field can be token-streamed, or once with the complete value otherwise.

Usage

stream_listener(field, callback)

Arguments

field: Name of the output field to listen to (a single string).
callback: A function called with each chunk of text (a single string). For non-streamable fields, called once with the full value.

Value

A dsprrr_stream_listener object for use with run_stream().

Details

Token-level streaming is available when a module's output is a single string field. In that case dsprrr streams the response as plain text and treats the accumulated text as the field's value. Modules with multiple or non-string output fields run normally and fire each matching listener once with the completed value (chunked streaming of structured output is not supported by the underlying structured-output API).

Examples

if (FALSE) { # \dontrun{
listener <- stream_listener("answer", function(chunk) cat(chunk))
run_stream(mod, question = "Tell me a story", listeners = list(listener))
} # }