wip

Author: realark

src/main/java/dev/braintrust/instrumentation/openai/otel/ChatCompletionEventsHelper.java

@@ -100,6 +100,24 @@ public SemconvChatMessage(String role, List<Object> parts) {
         }
     }
 
+    @JsonInclude(JsonInclude.Include.NON_NULL)
+    static class SemconvOutputChatMessage {
+        @JsonProperty("role")
+        public final String role;
+
+        @JsonProperty("parts")
+        public final List<Object> parts;
+
+        @JsonProperty("finish_reason")
+        public final String finishReason;
+
+        public SemconvOutputChatMessage(String role, List<Object> parts, String finishReason) {
+            this.role = role;
+            this.parts = parts;
+            this.finishReason = finishReason;
+        }
+    }
+
     @JsonInclude(JsonInclude.Include.NON_NULL)
     static class TextPart {
         @JsonProperty("type")
@@ -394,6 +412,38 @@ private static SemconvChatMessage transformToolMessage(ChatCompletionToolMessage
         return new SemconvChatMessage("tool", parts);
     }
 
+    // Transform ChatCompletionMessage (output) to OTel GenAI semconv format
+    private static SemconvOutputChatMessage transformOutputMessage(
+            ChatCompletionMessage message, String finishReason) {
+        List<Object> parts = new ArrayList<>();
+
+        // Handle text content
+        message.content()
+                .ifPresent(content -> {
+                    if (!content.isEmpty()) {
+                        parts.add(new TextPart(content));
+                    }
+                });
+
+        // Handle tool calls
+        message.toolCalls()
+                .ifPresent(toolCalls -> {
+                    for (var toolCall : toolCalls) {
+                        FunctionAccess functionAccess = getFunctionAccess(toolCall);
+                        if (functionAccess != null) {
+                            parts.add(
+                                    new ToolCallRequestPart(
+                                            functionAccess.name(),
+                                            functionAccess.id(),
+                                            functionAccess.arguments()));
+                        }
+                    }
+                });
+
+        // The role from ChatCompletionMessage is always "assistant" for output messages
+        return new SemconvOutputChatMessage("assistant", parts, finishReason);
+    }
+
     @SneakyThrows
     public static void emitPromptLogEvents(
             Context context,
@@ -488,14 +538,13 @@ public static void emitCompletionLogEvents(
         } else if (completion.choices().size() > 1) {
             log.debug("multiple choices in OAI response: {}", completion.choices().size());
         } else {
-            Span.current()
-                    .setAttribute(
-                            // "gen_ai.output.messages",
-                            "braintrust.output_json",
-                            JSON_MAPPER.writeValueAsString(
-                                    new ChatCompletionMessage[] {
-                                        completion.choices().get(0).message()
-                                    }));
+            // Set gen_ai.output.messages attribute for single choice (most common case)
+            ChatCompletion.Choice choice = completion.choices().get(0);
+            SemconvOutputChatMessage outputMessage = transformOutputMessage(
+                    choice.message(),
+                    choice.finishReason().toString());
+            String outputJson = JSON_MAPPER.writeValueAsString(new SemconvOutputChatMessage[] {outputMessage});
+            Span.current().setAttribute("gen_ai.output.messages", outputJson);
         }
         for (ChatCompletion.Choice choice : completion.choices()) {
             ChatCompletionMessage choiceMsg = choice.message();