1 files changed, 71 insertions, 0 deletions
diff --git a/internal/usage/observer_test.go b/internal/usage/observer_test.go
index 4a4eba6..e96a38a 100644
--- a/internal/usage/observer_test.go
+++ b/internal/usage/observer_test.go
@@ -2,6 +2,7 @@ package usage
 
 import (
 	"testing"
+	"time"
 
 	"aigw/internal/domain"
 )
@@ -57,3 +58,73 @@ func TestObserverReadsResponsesUsage(t *testing.T) {
 		t.Fatalf("unexpected streaming Responses usage: %+v reported=%v", got, stream.Reported())
 	}
 }
+
+func TestObserverReadsEmbeddingsUsage(t *testing.T) {
+	observer := NewObserver(domain.ProtocolOpenAIEmbeddings, false)
+	_, _ = observer.Write([]byte(`{"object":"list","data":[],"usage":{"prompt_tokens":17,"total_tokens":17}}`))
+	got := observer.Usage()
+	if !observer.Reported() || got.InputTokens != 17 || got.OutputTokens != 0 || got.TotalTokens != 17 {
+		t.Fatalf("unexpected Embeddings usage: %+v reported=%v", got, observer.Reported())
+	}
+}
+
+func TestObserverMarksFirstVisibleStreamingOutput(t *testing.T) {
+	base := time.Date(2026, 8, 6, 1, 2, 3, 0, time.UTC)
+	tests := []struct {
+		name     string
+		protocol domain.Protocol
+		metadata string
+		output   string
+	}{
+		{
+			name: "openai chat", protocol: domain.ProtocolOpenAI,
+			metadata: "data: {\"choices\":[{\"delta\":{\"role\":\"assistant\",\"content\":null}}]}\n\n",
+			output:   "data: {\"choices\":[{\"delta\":{\"content\":\"Hello\"}}]}\n\n",
+		},
+		{
+			name: "responses", protocol: domain.ProtocolOpenAIResponses,
+			metadata: "data: {\"type\":\"response.created\"}\n\n",
+			output:   "data: {\"type\":\"response.output_text.delta\",\"delta\":\"Hello\"}\n\n",
+		},
+		{
+			name: "anthropic", protocol: domain.ProtocolAnthropic,
+			metadata: "data: {\"type\":\"content_block_start\",\"content_block\":{\"type\":\"text\",\"text\":\"\"}}\n\n",
+			output:   "data: {\"type\":\"content_block_delta\",\"delta\":{\"type\":\"text_delta\",\"text\":\"Hello\"}}\n\n",
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			observer := NewObserver(test.protocol, true)
+			current := base
+			observer.now = func() time.Time { return current }
+			_, _ = observer.Write([]byte(test.metadata))
+			if got := observer.FirstOutputAt(); !got.IsZero() {
+				t.Fatalf("metadata marked first output at %v", got)
+			}
+			current = base.Add(275 * time.Millisecond)
+			_, _ = observer.Write([]byte(test.output))
+			if got := observer.FirstOutputAt(); !got.Equal(current) {
+				t.Fatalf("first output = %v, want %v", got, current)
+			}
+			current = base.Add(time.Second)
+			_, _ = observer.Write([]byte(test.output))
+			if got := observer.FirstOutputAt(); !got.Equal(base.Add(275 * time.Millisecond)) {
+				t.Fatalf("first output changed to %v", got)
+			}
+		})
+	}
+}
+
+func TestObserverMarksFirstNonStreamingBodyWrite(t *testing.T) {
+	base := time.Date(2026, 8, 6, 1, 2, 3, 0, time.UTC)
+	observer := NewObserver(domain.ProtocolOpenAI, false)
+	observer.now = func() time.Time { return base }
+	_, _ = observer.Write(nil)
+	if !observer.FirstOutputAt().IsZero() {
+		t.Fatal("empty write must not mark first output")
+	}
+	_, _ = observer.Write([]byte(`{"choices":[]}`))
+	if got := observer.FirstOutputAt(); !got.Equal(base) {
+		t.Fatalf("first output = %v, want %v", got, base)
+	}
+}