Terminal stream results

StreamResult is terminal metadata for one cleanly completed provider stream. It is not another chunk and is available only after Next observes clean io.EOF.

API surface

type StreamResult struct {
	Usage        *content.Usage
	Model        string
	FinishReason FinishReason
	Attempts     int
}

type StreamResultProducer func() (StreamResult, bool, error)

for {
	_, err := reader.Next()
	if errors.Is(err, io.EOF) {
		break
	}
	if err != nil {
		return err
	}
}
result, ok := reader.Result()
if ok {
	// Result returns an independent Usage copy.
	fmt.Println(result.Model, result.FinishReason, result.Attempts)
}

The producer is called once at clean EOF. A false boolean means no authoritative metadata. Producer errors are wrapped in *StreamResultError; invalid usage also becomes a result error. A non-EOF stream failure clears any result, so partial metadata cannot be mistaken for a completed response.

Frame adapters

FramesToChunksWithResult gives a semantic decoder its own producer. If that producer is absent, the adapter propagates the underlying frame reader’s result. This keeps provider-specific accumulation out of the generic reader.

Proof

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

Related: Response usage, Finish reasons.