diff --git a/backend/internal/pkg/apicompat/anthropic_to_responses_response.go b/backend/internal/pkg/apicompat/anthropic_to_responses_response.go
index de8ab78df8..67c161bdd3 100644
--- a/backend/internal/pkg/apicompat/anthropic_to_responses_response.go
+++ b/backend/internal/pkg/apicompat/anthropic_to_responses_response.go
@@ -102,9 +102,10 @@ func AnthropicToResponsesResponse(resp *AnthropicResponse) *ResponsesResponse {
 		resp.Usage.CacheReadInputTokens +
 		resp.Usage.CacheCreationInputTokens
 	out.Usage = &ResponsesUsage{
-		InputTokens:  totalInputTokens,
-		OutputTokens: resp.Usage.OutputTokens,
-		TotalTokens:  totalInputTokens + resp.Usage.OutputTokens,
+		InputTokens:              totalInputTokens,
+		OutputTokens:             resp.Usage.OutputTokens,
+		TotalTokens:              totalInputTokens + resp.Usage.OutputTokens,
+		CacheCreationInputTokens: resp.Usage.CacheCreationInputTokens,
 	}
 	if resp.Usage.CacheReadInputTokens > 0 {
 		out.Usage.InputTokensDetails = &ResponsesInputTokensDetails{
@@ -497,9 +498,10 @@ func makeResponsesCompletedEvent(
 	// back to match OpenAI Responses semantics where input_tokens is the total.
 	totalInputTokens := state.InputTokens + state.CacheReadInputTokens + state.CacheCreationInputTokens
 	usage := &ResponsesUsage{
-		InputTokens:  totalInputTokens,
-		OutputTokens: state.OutputTokens,
-		TotalTokens:  totalInputTokens + state.OutputTokens,
+		InputTokens:              totalInputTokens,
+		OutputTokens:             state.OutputTokens,
+		TotalTokens:              totalInputTokens + state.OutputTokens,
+		CacheCreationInputTokens: state.CacheCreationInputTokens,
 	}
 	if state.CacheReadInputTokens > 0 {
 		usage.InputTokensDetails = &ResponsesInputTokensDetails{
diff --git a/backend/internal/pkg/apicompat/responses_anthropic_cache_creation_test.go b/backend/internal/pkg/apicompat/responses_anthropic_cache_creation_test.go
new file mode 100644
index 0000000000..a5856845c9
--- /dev/null
+++ b/backend/internal/pkg/apicompat/responses_anthropic_cache_creation_test.go
@@ -0,0 +1,64 @@
+package apicompat
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestAnthropicUsageFromResponsesUsage_CacheCreation(t *testing.T) {
+	usage := &ResponsesUsage{
+		InputTokens:              20,
+		OutputTokens:             5,
+		CacheCreationInputTokens: 6,
+		InputTokensDetails: &ResponsesInputTokensDetails{
+			CachedTokens: 4,
+		},
+	}
+
+	got := anthropicUsageFromResponsesUsage(usage)
+
+	assert.Equal(t, 10, got.InputTokens, "input = total(20) - cache_read(4) - cache_creation(6)")
+	assert.Equal(t, 5, got.OutputTokens)
+	assert.Equal(t, 4, got.CacheReadInputTokens)
+	assert.Equal(t, 6, got.CacheCreationInputTokens, "cache creation must be preserved")
+}
+
+func TestAnthropicUsageFromResponsesUsage_NoCacheCreation(t *testing.T) {
+	usage := &ResponsesUsage{
+		InputTokens:  10,
+		OutputTokens: 5,
+		InputTokensDetails: &ResponsesInputTokensDetails{
+			CachedTokens: 3,
+		},
+	}
+
+	got := anthropicUsageFromResponsesUsage(usage)
+
+	assert.Equal(t, 7, got.InputTokens)
+	assert.Equal(t, 3, got.CacheReadInputTokens)
+	assert.Equal(t, 0, got.CacheCreationInputTokens)
+}
+
+func TestAnthropicToResponsesResponse_CacheCreation(t *testing.T) {
+	resp := AnthropicResponse{
+		ID:    "msg_test",
+		Type:  "message",
+		Role:  "assistant",
+		Model: "claude-opus-4-6",
+		Usage: AnthropicUsage{
+			InputTokens:              10,
+			OutputTokens:             5,
+			CacheReadInputTokens:     4,
+			CacheCreationInputTokens: 6,
+		},
+		StopReason: "end_turn",
+	}
+
+	out := AnthropicToResponsesResponse(&resp)
+
+	require.NotNil(t, out.Usage)
+	assert.Equal(t, 20, out.Usage.InputTokens, "total = input(10) + cache_read(4) + cache_creation(6)")
+	assert.Equal(t, 6, out.Usage.CacheCreationInputTokens, "cache creation must round-trip")
+}
diff --git a/backend/internal/pkg/apicompat/responses_to_anthropic.go b/backend/internal/pkg/apicompat/responses_to_anthropic.go
index 037e16b652..9cc6e49c75 100644
--- a/backend/internal/pkg/apicompat/responses_to_anthropic.go
+++ b/backend/internal/pkg/apicompat/responses_to_anthropic.go
@@ -100,15 +100,16 @@ func anthropicUsageFromResponsesUsage(usage *ResponsesUsage) AnthropicUsage {
 		cachedTokens = usage.InputTokensDetails.CachedTokens
 	}
 
-	inputTokens := usage.InputTokens - cachedTokens
+	inputTokens := usage.InputTokens - cachedTokens - usage.CacheCreationInputTokens
 	if inputTokens < 0 {
 		inputTokens = 0
 	}
 
 	return AnthropicUsage{
-		InputTokens:          inputTokens,
-		OutputTokens:         usage.OutputTokens,
-		CacheReadInputTokens: cachedTokens,
+		InputTokens:              inputTokens,
+		OutputTokens:             usage.OutputTokens,
+		CacheReadInputTokens:     cachedTokens,
+		CacheCreationInputTokens: usage.CacheCreationInputTokens,
 	}
 }