feat(langfuse): add Score event support

Implement ScoreEventBody and CreateScore API to enable evaluation of LLM
outputs via Langfuse scores (e.g., user satisfaction, accuracy metrics).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: danostrosky

libs/acl/langfuse/event.go

@@ -79,6 +79,7 @@ type eventBodyUnion struct {
 	Span       *SpanEventBody       `json:",inline,omitempty"`
 	Generation *GenerationEventBody `json:",inline,omitempty"`
 	Event      *EventEventBody      `json:",inline,omitempty"`
+	Score      *ScoreEventBody      `json:",inline,omitempty"`
 	Log        *SDKLogEventBody     `json:",inline,omitempty"`
 }
 
@@ -91,6 +92,8 @@ func (e *eventBodyUnion) MarshalJSON() ([]byte, error) {
 		return sonic.Marshal(e.Generation)
 	} else if e.Event != nil {
 		return sonic.Marshal(e.Event)
+	} else if e.Score != nil {
+		return sonic.Marshal(e.Score)
 	}
 	return nil, fmt.Errorf("event body is empty")
 }
@@ -104,6 +107,8 @@ func (e *eventBodyUnion) getTraceID() string {
 		return e.Generation.TraceID
 	} else if e.Event != nil {
 		return e.Event.TraceID
+	} else if e.Score != nil {
+		return e.Score.TraceID
 	}
 	return ""
 }
@@ -115,6 +120,8 @@ func (e *eventBodyUnion) getObservationID() string {
 		return e.Generation.ID
 	} else if e.Event != nil {
 		return e.Event.ID
+	} else if e.Score != nil {
+		return e.Score.ObservationID
 	}
 	return ""
 }
@@ -257,4 +264,14 @@ type SDKLogEventBody struct {
 	Log string `json:"log"`
 }
 
-// TODO: ScoreEvent
+type ScoreEventBody struct {
+	ID            string  `json:"id,omitempty"`
+	TraceID       string  `json:"traceId"`
+	Name          string  `json:"name"`
+	Value         float64 `json:"value"`
+	ObservationID string  `json:"observationId,omitempty"`
+	Comment       string  `json:"comment,omitempty"`
+	DataType      string  `json:"dataType,omitempty"`
+	ConfigID      string  `json:"configId,omitempty"`
+	Environment   string  `json:"environment,omitempty"`
+}

libs/acl/langfuse/event_test.go

@@ -77,6 +77,19 @@ func TestEventBodyUnion(t *testing.T) {
 	assert.Equal(t, observationID, eventUnion.getObservationID())
 	assert.Equal(t, map[string]string{"key": "value"}, eventUnion.getMetadata())
 
+	scoreUnion := &eventBodyUnion{Score: &ScoreEventBody{
+		ID:            "scoreID",
+		TraceID:       traceID,
+		Name:          "accuracy",
+		Value:         0.95,
+		ObservationID: observationID,
+	}}
+	assert.Equal(t, traceID, scoreUnion.getTraceID())
+	assert.Equal(t, observationID, scoreUnion.getObservationID())
+	assert.Equal(t, "", scoreUnion.getInput())
+	assert.Equal(t, "", scoreUnion.getOutput())
+	assert.Nil(t, scoreUnion.getMetadata())
+
 	generationUnion := &eventBodyUnion{Generation: &GenerationEventBody{
 		BaseObservationEventBody: BaseObservationEventBody{
 			BaseEventBody: BaseEventBody{

libs/acl/langfuse/langfuse.go

@@ -37,6 +37,7 @@ type Langfuse interface {
 	CreateGeneration(body *GenerationEventBody) (string, error)
 	EndGeneration(body *GenerationEventBody) error
 	CreateEvent(body *EventEventBody) (string, error)
+	CreateScore(body *ScoreEventBody) (string, error)
 	Flush()
 }
 
@@ -205,6 +206,25 @@ func (l *langfuseIns) CreateEvent(body *EventEventBody) (string, error) {
 	})
 }
 
+// CreateScore creates a new score for evaluating LLM outputs
+//
+// Parameters:
+//   - body: The score event details. If ID is empty, a new UUID will be generated
+//
+// Returns:
+//   - string: The ID of the created score
+//   - error: Any error that occurred during creation
+func (l *langfuseIns) CreateScore(body *ScoreEventBody) (string, error) {
+	if len(body.ID) == 0 {
+		body.ID = uuid.NewString()
+	}
+	return body.ID, l.tm.push(&event{
+		ID:   uuid.NewString(),
+		Type: EventTypeScoreCreate,
+		Body: eventBodyUnion{Score: body},
+	})
+}
+
 // Flush waits for all queued events to be processed and uploaded to Langfuse
 //
 // This method blocks until all pending events in the queue have been processed