Expose cache usage in adapters

internal/adapter/cli/run.go

@@ -606,7 +606,7 @@ func printSummary(stderr io.Writer, res *domain.RunResult) {
 	if res == nil {
 		return
 	}
-	fmt.Fprintf(stderr, "prompt=%s@%s selected_profile=%s model=%s validation=%s mode=%s validation_errors=%d prompt_hash=%s inputs=%d usage=%d/%d/%d\n",
+	fmt.Fprintf(stderr, "prompt=%s@%s selected_profile=%s model=%s validation=%s mode=%s validation_errors=%d prompt_hash=%s inputs=%d usage=%d/%d/%d",
 		res.PromptID,
 		res.PromptVersion,
 		res.SelectedProfileID,
@@ -620,6 +620,10 @@ func printSummary(stderr io.Writer, res *domain.RunResult) {
 		res.Usage.CompletionTokens,
 		res.Usage.TotalTokens,
 	)
+	if res.Usage.CachedTokens != 0 || res.Usage.CacheWriteTokens != 0 {
+		fmt.Fprintf(stderr, " cached_tokens=%d cache_write_tokens=%d", res.Usage.CachedTokens, res.Usage.CacheWriteTokens)
+	}
+	fmt.Fprintln(stderr)
 }
 
 func printUsage(w io.Writer) {

internal/adapter/cli/run_test.go

@@ -1064,6 +1064,38 @@ func TestWriteOutputAndSummaryUseSeparateWriters(t *testing.T) {
 	if !strings.Contains(stderr.String(), "prompt=p@1") {
 		t.Fatalf("expected summary on stderr, got %q", stderr.String())
 	}
+	if strings.Contains(stderr.String(), "cached_tokens=") || strings.Contains(stderr.String(), "cache_write_tokens=") {
+		t.Fatalf("expected zero cache usage to be omitted from summary, got %q", stderr.String())
+	}
+}
+
+func TestPrintSummaryIncludesCacheUsageWhenPresent(t *testing.T) {
+	var stderr bytes.Buffer
+
+	printSummary(&stderr, &domain.RunResult{
+		PromptID:           "p",
+		PromptVersion:      "1",
+		SelectedProfileID:  "exec",
+		ModelName:          "m",
+		Validation:         domain.ValidationResult{Status: domain.ValidationPassed, Mode: domain.ValidationBasic},
+		RenderedPromptHash: "h",
+		InputHashes:        map[string]string{"in": "x"},
+		Usage: domain.TokenUsage{
+			PromptTokens:     10,
+			CompletionTokens: 5,
+			TotalTokens:      15,
+			CachedTokens:     0,
+			CacheWriteTokens: 3,
+		},
+	})
+
+	summary := stderr.String()
+	if !strings.Contains(summary, "usage=10/5/15") {
+		t.Fatalf("expected base usage summary, got %q", summary)
+	}
+	if !strings.Contains(summary, "cached_tokens=0 cache_write_tokens=3") {
+		t.Fatalf("expected cache usage in summary, got %q", summary)
+	}
 }
 
 type cliTestLibrary struct {

internal/adapter/http/dto.go

@@ -86,6 +86,8 @@ type tokenUsageDTO struct {
 	PromptTokens     int `json:"prompt_tokens"`
 	CompletionTokens int `json:"completion_tokens"`
 	TotalTokens      int `json:"total_tokens"`
+	CachedTokens     int `json:"cached_tokens"`
+	CacheWriteTokens int `json:"cache_write_tokens"`
 }
 
 type validationDTO struct {

internal/adapter/http/handler.go

@@ -105,6 +105,8 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 				PromptTokens:     res.Usage.PromptTokens,
 				CompletionTokens: res.Usage.CompletionTokens,
 				TotalTokens:      res.Usage.TotalTokens,
+				CachedTokens:     res.Usage.CachedTokens,
+				CacheWriteTokens: res.Usage.CacheWriteTokens,
 			},
 			StartTime:          res.StartTime,
 			EndTime:            res.EndTime,

internal/adapter/http/handler_test.go

@@ -66,11 +66,17 @@ func TestHandlerPostRunsSuccessWithExplicitProfileID(t *testing.T) {
 			APIKeyEnv:      envName,
 		},
 		InputHashes: map[string]string{"transcript": "h1"},
-		Usage:       domain.TokenUsage{PromptTokens: 1, CompletionTokens: 2, TotalTokens: 3},
-		StartTime:   start,
-		EndTime:     end,
-		Duration:    2 * time.Second,
-		RawOutput:   "hello",
+		Usage: domain.TokenUsage{
+			PromptTokens:     1,
+			CompletionTokens: 2,
+			TotalTokens:      3,
+			CachedTokens:     4,
+			CacheWriteTokens: 5,
+		},
+		StartTime: start,
+		EndTime:   end,
+		Duration:  2 * time.Second,
+		RawOutput: "hello",
 	}}
 
 	h := NewHandler(r)
@@ -111,6 +117,13 @@ func TestHandlerPostRunsSuccessWithExplicitProfileID(t *testing.T) {
 	if metadata["model_name"] != "m1" || metadata["endpoint"] != "http://llm/v1" {
 		t.Fatalf("unexpected model metadata: name=%#v endpoint=%#v", metadata["model_name"], metadata["endpoint"])
 	}
+	usage := metadata["usage"].(map[string]any)
+	if usage["prompt_tokens"] != float64(1) || usage["completion_tokens"] != float64(2) || usage["total_tokens"] != float64(3) {
+		t.Fatalf("unexpected base usage metadata: %#v", usage)
+	}
+	if usage["cached_tokens"] != float64(4) || usage["cache_write_tokens"] != float64(5) {
+		t.Fatalf("unexpected cache usage metadata: %#v", usage)
+	}
 	modelParams := metadata["model_params"].(map[string]any)
 	if modelParams["api_key_env"] != envName {
 		t.Fatalf("expected model_params.api_key_env=%q, got %#v", envName, modelParams["api_key_env"])
@@ -171,6 +184,10 @@ func TestHandlerPostRunsSuccessUsingPromptDefaultProfile(t *testing.T) {
 	if metadata["selected_profile_id"] != "prompt-default" {
 		t.Fatalf("expected selected_profile_id from result, got %#v", metadata["selected_profile_id"])
 	}
+	usage := metadata["usage"].(map[string]any)
+	if usage["cached_tokens"] != float64(0) || usage["cache_write_tokens"] != float64(0) {
+		t.Fatalf("expected zero cache usage fields to be included, got %#v", usage)
+	}
 }
 
 func TestHandlerModelOverrideMapsAllSupportedExecutionFields(t *testing.T) {