diff --git a/backend/internal/pkg/apicompat/responses_anthropic_cache_creation_test.go b/backend/internal/pkg/apicompat/responses_anthropic_cache_creation_test.go
index a5856845c9..b8c7916d2d 100644
--- a/backend/internal/pkg/apicompat/responses_anthropic_cache_creation_test.go
+++ b/backend/internal/pkg/apicompat/responses_anthropic_cache_creation_test.go
@@ -41,6 +41,41 @@ func TestAnthropicUsageFromResponsesUsage_NoCacheCreation(t *testing.T) {
 	assert.Equal(t, 0, got.CacheCreationInputTokens)
 }
 
+func TestResponsesEventToAnthropicEvents_StreamingCacheCreation(t *testing.T) {
+	state := NewResponsesEventToAnthropicState()
+	state.MessageStartSent = true
+
+	completedEvt := &ResponsesStreamEvent{
+		Type: "response.completed",
+		Response: &ResponsesResponse{
+			Status: "completed",
+			Usage: &ResponsesUsage{
+				InputTokens:              20,
+				OutputTokens:             5,
+				CacheCreationInputTokens: 6,
+				InputTokensDetails: &ResponsesInputTokensDetails{
+					CachedTokens: 4,
+				},
+			},
+		},
+	}
+
+	events := ResponsesEventToAnthropicEvents(completedEvt, state)
+
+	var deltaEvt *AnthropicStreamEvent
+	for i := range events {
+		if events[i].Type == "message_delta" {
+			deltaEvt = &events[i]
+			break
+		}
+	}
+	require.NotNil(t, deltaEvt, "should have message_delta event")
+	require.NotNil(t, deltaEvt.Usage)
+	assert.Equal(t, 6, deltaEvt.Usage.CacheCreationInputTokens, "streaming cache_creation must be preserved")
+	assert.Equal(t, 10, deltaEvt.Usage.InputTokens, "input = 20 - 4(read) - 6(creation)")
+	assert.Equal(t, 4, deltaEvt.Usage.CacheReadInputTokens)
+}
+
 func TestAnthropicToResponsesResponse_CacheCreation(t *testing.T) {
 	resp := AnthropicResponse{
 		ID:    "msg_test",
diff --git a/backend/internal/pkg/apicompat/responses_to_anthropic.go b/backend/internal/pkg/apicompat/responses_to_anthropic.go
index 9cc6e49c75..9c3b85b2ef 100644
--- a/backend/internal/pkg/apicompat/responses_to_anthropic.go
+++ b/backend/internal/pkg/apicompat/responses_to_anthropic.go
@@ -182,9 +182,10 @@ type ResponsesEventToAnthropicState struct {
 	// OutputIndexToBlockIdx maps Responses output_index → Anthropic content block index.
 	OutputIndexToBlockIdx map[int]int
 
-	InputTokens          int
-	OutputTokens         int
-	CacheReadInputTokens int
+	InputTokens              int
+	OutputTokens             int
+	CacheReadInputTokens     int
+	CacheCreationInputTokens int
 
 	ResponseID string
 	Model      string
@@ -259,9 +260,10 @@ func FinalizeResponsesAnthropicStream(state *ResponsesEventToAnthropicState) []A
 				StopReason: stopReason,
 			},
 			Usage: &AnthropicUsage{
-				InputTokens:          state.InputTokens,
-				OutputTokens:         state.OutputTokens,
-				CacheReadInputTokens: state.CacheReadInputTokens,
+				InputTokens:              state.InputTokens,
+				OutputTokens:             state.OutputTokens,
+				CacheReadInputTokens:     state.CacheReadInputTokens,
+				CacheCreationInputTokens: state.CacheCreationInputTokens,
 			},
 		},
 		AnthropicStreamEvent{Type: "message_stop"},
@@ -579,6 +581,7 @@ func resToAnthHandleCompleted(evt *ResponsesStreamEvent, state *ResponsesEventTo
 		state.InputTokens = usage.InputTokens
 		state.OutputTokens = usage.OutputTokens
 		state.CacheReadInputTokens = usage.CacheReadInputTokens
+		state.CacheCreationInputTokens = usage.CacheCreationInputTokens
 	}
 	if evt.Response != nil {
 		if evt.Response.Usage != nil {
@@ -586,6 +589,7 @@ func resToAnthHandleCompleted(evt *ResponsesStreamEvent, state *ResponsesEventTo
 			state.InputTokens = usage.InputTokens
 			state.OutputTokens = usage.OutputTokens
 			state.CacheReadInputTokens = usage.CacheReadInputTokens
+			state.CacheCreationInputTokens = usage.CacheCreationInputTokens
 		}
 		switch evt.Response.Status {
 		case "incomplete":
@@ -606,9 +610,10 @@ func resToAnthHandleCompleted(evt *ResponsesStreamEvent, state *ResponsesEventTo
 				StopReason: stopReason,
 			},
 			Usage: &AnthropicUsage{
-				InputTokens:          state.InputTokens,
-				OutputTokens:         state.OutputTokens,
-				CacheReadInputTokens: state.CacheReadInputTokens,
+				InputTokens:              state.InputTokens,
+				OutputTokens:             state.OutputTokens,
+				CacheReadInputTokens:     state.CacheReadInputTokens,
+				CacheCreationInputTokens: state.CacheCreationInputTokens,
 			},
 		},
 		AnthropicStreamEvent{Type: "message_stop"},