Streaming errors

The stream package distinguishes clean io.EOF from every other failure. Once a non-EOF error occurs, the reader is permanently failed and Result returns false.

Typed errors

type StreamReaderError struct {
	Operation StreamOperation
	Failure   StreamReaderFailure
}

type StreamResultError struct {
	Cause error
}

StreamReaderFailure values include nil receiver, missing next function, and missing frame mapper. StreamResultError.Unwrap exposes ordinary causes but suppresses an io.EOF cause so metadata failure cannot masquerade as clean exhaustion.

value, err := reader.Next()
if err != nil && !errors.Is(err, io.EOF) {
	var boundary *stream.StreamReaderError
	if errors.As(err, &boundary) {
		log.Printf("stream boundary %s: %s", boundary.Operation, boundary.Failure)
	}
	_ = value
	return err
}

FramesToChunks skips (nil, nil) frame mappings, buffers multiple chunks returned for one frame, drains chunks returned alongside an io.EOF sentinel, and discards chunks returned with a non-EOF mapping error.

Proof

• Source: inference/stream/result.go, inference/stream/chunkstream.go
• Tests: inference/stream/stream_test.go, inference/stream/chunkstream_test.go

Related: StreamReader, Terminal stream results.