diff --git a/backend/internal/service/antigravity_gateway_service.go b/backend/internal/service/antigravity_gateway_service.go
index 5a90a195..31b3ece0 100644
--- a/backend/internal/service/antigravity_gateway_service.go
+++ b/backend/internal/service/antigravity_gateway_service.go
@@ -4463,6 +4463,14 @@ func (s *AntigravityGatewayService) streamUpstreamResponse(c *gin.Context, resp
 }
 
 // extractSSEUsage 从 SSE data 行中提取 Claude usage（用于流式透传场景）
+//
+// Anthropic streaming 的 usage 字段分布在两类事件中：
+//   - message_start：嵌套在 event.message.usage（input_tokens、cache_creation_input_tokens、
+//     cache_read_input_tokens 等输入侧字段）
+//   - message_delta：位于顶层 event.usage（流结束时的最终 output_tokens）
+//
+// 仅读取顶层 event.usage 会漏掉 message_start 的输入侧字段，导致流式透传请求落库的
+// usage_logs 记录 input_tokens=0。
 func (s *AntigravityGatewayService) extractSSEUsage(line string, usage *ClaudeUsage) {
 	if !strings.HasPrefix(line, "data: ") {
 		return
@@ -4472,8 +4480,15 @@ func (s *AntigravityGatewayService) extractSSEUsage(line string, usage *ClaudeUs
 	if json.Unmarshal([]byte(dataStr), &event) != nil {
 		return
 	}
-	u, ok := event["usage"].(map[string]any)
-	if !ok {
+	var u map[string]any
+	if eventType, _ := event["type"].(string); eventType == "message_start" {
+		if msg, ok := event["message"].(map[string]any); ok {
+			u, _ = msg["usage"].(map[string]any)
+		}
+	} else {
+		u, _ = event["usage"].(map[string]any)
+	}
+	if u == nil {
 		return
 	}
 	if v, ok := u["input_tokens"].(float64); ok && int(v) > 0 {
diff --git a/backend/internal/service/antigravity_gateway_service_test.go b/backend/internal/service/antigravity_gateway_service_test.go
index 1eb1451e..22124374 100644
--- a/backend/internal/service/antigravity_gateway_service_test.go
+++ b/backend/internal/service/antigravity_gateway_service_test.go
@@ -1301,6 +1301,19 @@ func TestExtractSSEUsage(t *testing.T) {
 			line:     `data: {"usage":{"input_tokens":10,"output_tokens":20,"cache_read_input_tokens":5,"cache_creation_input_tokens":3}}`,
 			expected: ClaudeUsage{InputTokens: 10, OutputTokens: 20, CacheReadInputTokens: 5, CacheCreationInputTokens: 3},
 		},
+		{
+			// Anthropic message_start 把 usage 嵌套在 message.usage 下，
+			// 必须从这里提取输入侧字段（含 cache_read/cache_creation_input_tokens）。
+			name:     "message_start nested usage with input/cache tokens",
+			line:     `data: {"type":"message_start","message":{"id":"msg_01","usage":{"input_tokens":35576,"cache_creation_input_tokens":0,"cache_read_input_tokens":12000,"output_tokens":1}}}`,
+			expected: ClaudeUsage{InputTokens: 35576, OutputTokens: 1, CacheReadInputTokens: 12000},
+		},
+		{
+			// message_start.message.usage.cache_creation 内的 5m/1h 明细也要解析。
+			name:     "message_start nested usage with cache_creation breakdown",
+			line:     `data: {"type":"message_start","message":{"usage":{"input_tokens":100,"cache_creation":{"ephemeral_5m_input_tokens":30,"ephemeral_1h_input_tokens":70}}}}`,
+			expected: ClaudeUsage{InputTokens: 100, CacheCreation5mTokens: 30, CacheCreation1hTokens: 70},
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -1311,6 +1324,29 @@ func TestExtractSSEUsage(t *testing.T) {
 	}
 }
 
+// TestExtractSSEUsage_StreamingSequence 复现 issue #2332：完整的 Anthropic streaming
+// 序列（message_start → message_delta）必须把两类事件中的 usage 字段都汇入同一份累计值，
+// 否则透传账号产出的 usage_logs 会出现 input_tokens=0、仅有 output_tokens 的"残缺"记录。
+func TestExtractSSEUsage_StreamingSequence(t *testing.T) {
+	svc := &AntigravityGatewayService{}
+	usage := &ClaudeUsage{}
+
+	// 1) message_start：携带完整输入侧 usage（input_tokens + cache_read）
+	svc.extractSSEUsage(
+		`data: {"type":"message_start","message":{"id":"msg_01","type":"message","role":"assistant","content":[],"model":"claude-opus-4-6","stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":35576,"cache_creation_input_tokens":0,"cache_read_input_tokens":12000,"output_tokens":1}}}`,
+		usage,
+	)
+	// 2) message_delta：流结束时只带 output_tokens（无 input_tokens 字段）
+	svc.extractSSEUsage(
+		`data: {"type":"message_delta","delta":{"stop_reason":"end_turn","stop_sequence":null},"usage":{"output_tokens":816}}`,
+		usage,
+	)
+
+	require.Equal(t, 35576, usage.InputTokens, "message_start 的 input_tokens 必须被记录，否则记账会缺失输入侧 token (#2332)")
+	require.Equal(t, 12000, usage.CacheReadInputTokens, "message_start 的 cache_read_input_tokens 必须被记录")
+	require.Equal(t, 816, usage.OutputTokens, "message_delta 的最终 output_tokens 必须被记录")
+}
+
 // TestAntigravityClientWriter 验证 antigravityClientWriter 的断开检测
 func TestAntigravityClientWriter(t *testing.T) {
 	t.Run("normal write succeeds", func(t *testing.T) {