fix: preserve JSON structure for redacted message attributes

When OmitIO is true, wrap REDACTED placeholder in proper JSON structure
so the UI can parse roles and show user/assistant entries in the
conversation timeline.

Author: GuyMoses

internal/otlp/otlp.go

@@ -324,9 +324,12 @@ func eventAttributes(event map[string]any, cfg Config) []Attribute {
 				key = mapped
 			}
 			if t, ok := attrTransformMap[k]; ok {
-				key = t.key
+				// Apply transform with redacted placeholder to preserve JSON structure
+				redactedTransformed := t.transform(redactedValue)
+				attrs = append(attrs, Attribute{Key: t.key, Value: StringVal(redactedTransformed)})
+			} else {
+				attrs = append(attrs, Attribute{Key: key, Value: StringVal(redactedValue)})
 			}
-			attrs = append(attrs, Attribute{Key: key, Value: StringVal(redactedValue)})
 			continue
 		}
 		if t, ok := attrTransformMap[k]; ok {

internal/otlp/otlp_test.go

@@ -237,10 +237,14 @@ func TestSendLogOmitIO(t *testing.T) {
 	assertAttr(t, lr.Attributes, "gen_ai.tool.name", "Bash")
 
 	// Content attributes are present but redacted.
+	// Tool I/O uses plain redaction.
 	assertAttr(t, lr.Attributes, "gen_ai.tool.call.arguments", "<REDACTED>")
 	assertAttr(t, lr.Attributes, "gen_ai.tool.call.result", "<REDACTED>")
-	assertAttr(t, lr.Attributes, "gen_ai.output.messages", "<REDACTED>")
-	assertAttr(t, lr.Attributes, "gen_ai.input.messages", "<REDACTED>")
+	// Message attributes preserve JSON structure for UI parsing.
+	assertAttrContains(t, lr.Attributes, "gen_ai.output.messages", `"role":"assistant"`)
+	assertAttrContains(t, lr.Attributes, "gen_ai.output.messages", `REDACTED`)
+	assertAttrContains(t, lr.Attributes, "gen_ai.input.messages", `"role":"user"`)
+	assertAttrContains(t, lr.Attributes, "gen_ai.input.messages", `REDACTED`)
 }
 
 func TestTruncateContent(t *testing.T) {
@@ -320,6 +324,18 @@ func assertAttr(t *testing.T, attrs []Attribute, key, want string) {
 	t.Errorf("attribute %s not found", key)
 }
 
+func assertAttrContains(t *testing.T, attrs []Attribute, key, substr string) {
+	t.Helper()
+	for _, a := range attrs {
+		if a.Key == key {
+			require.NotNil(t, a.Value.StringValue, "attribute %s: stringValue is nil", key)
+			assert.Contains(t, *a.Value.StringValue, substr, "attribute %s should contain %q", key, substr)
+			return
+		}
+	}
+	t.Errorf("attribute %s not found", key)
+}
+
 func assertIntAttr(t *testing.T, attrs []Attribute, key string, want int64) {
 	t.Helper()
 	for _, a := range attrs {

internal/otlp/trace_test.go

@@ -278,9 +278,11 @@ func TestNewLLMSpanOmitIO(t *testing.T) {
 
 	// Model is still present.
 	assertAttr(t, span.Attributes, "gen_ai.request.model", "claude-sonnet-4-20250514")
-	// Content attributes are present but redacted.
-	assertAttr(t, span.Attributes, "gen_ai.input.messages", "<REDACTED>")
-	assertAttr(t, span.Attributes, "gen_ai.output.messages", "<REDACTED>")
+	// Content attributes are present but redacted, preserving JSON structure for UI parsing.
+	assertAttrContains(t, span.Attributes, "gen_ai.input.messages", `"role":"user"`)
+	assertAttrContains(t, span.Attributes, "gen_ai.input.messages", `REDACTED`)
+	assertAttrContains(t, span.Attributes, "gen_ai.output.messages", `"role":"assistant"`)
+	assertAttrContains(t, span.Attributes, "gen_ai.output.messages", `REDACTED`)
 }
 
 func TestSendTraceSkipsWhenNotConfigured(t *testing.T) {