Preserve OpenAI audio transcription output

braintrust-sdk/src/main/java/dev/braintrust/instrumentation/InstrumentationSemConv.java

@@ -199,11 +199,14 @@ private static void tagOpenAIRequest(
     @SneakyThrows
     private static void tagOpenAIResponse(
             Span span, JsonNode responseJson, @Nullable Long timeToFirstTokenNanoseconds) {
-        // Output — chat completions API uses "choices"; Responses API uses "output"
+        // Output — chat completions API uses "choices"; Responses API uses "output"; audio
+        // transcriptions and translations return a text-keyed object.
         if (responseJson.has("choices")) {
             span.setAttribute("braintrust.output_json", toJson(responseJson.get("choices")));
         } else if (responseJson.has("output")) {
             span.setAttribute("braintrust.output_json", toJson(responseJson.get("output")));
+        } else if (responseJson.has("text")) {
+            span.setAttribute("braintrust.output_json", toJson(responseJson));
         }
 
         Map<String, Object> metrics = new HashMap<>();

braintrust-sdk/src/test/java/dev/braintrust/instrumentation/InstrumentationSemConvTest.java

@@ -20,11 +20,7 @@
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
-/**
- * Covers {@link InstrumentationSemConv#addServerSideChildSpans}: only vendor-executed (server-side)
- * tool calls in an OpenAI Responses body become child spans nested under the LLM span. Client-side
- * calls ({@code function_call}, {@code computer_call}) are excluded.
- */
+/** Covers provider response tagging and {@link InstrumentationSemConv#addServerSideChildSpans}. */
 class InstrumentationSemConvTest {
 
     private static final AttributeKey<String> SPAN_ATTRIBUTES =
@@ -81,6 +77,44 @@ private static JsonNode json(String s) {
         return BraintrustJsonMapper.fromJson(s, JsonNode.class);
     }
 
+    private SpanData tagOpenAIResponse(String responseBody) {
+        Span span = tracer.spanBuilder("llm").startSpan();
+        try {
+            InstrumentationSemConv.tagLLMSpanResponse(
+                    tracer, span, InstrumentationSemConv.PROVIDER_NAME_OPENAI, responseBody);
+        } finally {
+            span.end();
+        }
+        return byName(exporter.getFinishedSpanItems(), "llm");
+    }
+
+    @Test
+    void tagsOpenAIAudioTranscriptionOutput() {
+        SpanData span = tagOpenAIResponse("{\"text\":\"Hello from the recording.\"}");
+
+        assertEquals(
+                json("{\"text\":\"Hello from the recording.\"}"),
+                json(span.getAttributes().get(OUTPUT_JSON)));
+    }
+
+    @Test
+    void tagsOpenAIVerboseAudioTranscriptionOutput() {
+        String body =
+                """
+                {
+                  "text": "Hello from the recording.",
+                  "language": "english",
+                  "duration": 1.25,
+                  "segments": [{"id": 0, "text": "Hello from the recording."}],
+                  "words": [{"word": "Hello", "start": 0.0, "end": 0.4}]
+                }
+                """;
+
+        SpanData span = tagOpenAIResponse(body);
+
+        assertEquals(json(body), json(span.getAttributes().get(OUTPUT_JSON)));
+    }
+
     @Test
     void emitsWebSearchCallToolSpanParentedToLlm() {
         String body =