diff --git a/backend/internal/handler/gateway_handler.go b/backend/internal/handler/gateway_handler.go
index 3f7c9ff720..f5d99f3c3d 100644
--- a/backend/internal/handler/gateway_handler.go
+++ b/backend/internal/handler/gateway_handler.go
@@ -166,6 +166,7 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 		h.errorResponse(c, http.StatusBadRequest, "invalid_request_error", "Failed to parse request body")
 		return
 	}
+	body = parsedReq.Body.Bytes()
 	reqModel := parsedReq.Model
 	reqStream := parsedReq.Stream
 	reqLog = reqLog.With(zap.String("model", reqModel), zap.Bool("stream", reqStream))
@@ -1882,6 +1883,7 @@ func (h *GatewayHandler) CountTokens(c *gin.Context) {
 		h.errorResponse(c, http.StatusBadRequest, "invalid_request_error", "Failed to parse request body")
 		return
 	}
+	body = parsedReq.Body.Bytes()
 	// count_tokens 走 messages 严格校验时，复用已解析请求，避免二次反序列化。
 	SetClaudeCodeClientContext(c, body, parsedReq)
 	reqLog = reqLog.With(zap.String("model", parsedReq.Model), zap.Bool("stream", parsedReq.Stream))
diff --git a/backend/internal/handler/openai_gateway_count_tokens.go b/backend/internal/handler/openai_gateway_count_tokens.go
index 1143374603..a9c2710b9d 100644
--- a/backend/internal/handler/openai_gateway_count_tokens.go
+++ b/backend/internal/handler/openai_gateway_count_tokens.go
@@ -67,6 +67,7 @@ func (h *OpenAIGatewayHandler) CountTokens(c *gin.Context) {
 		h.anthropicErrorResponse(c, http.StatusBadRequest, "invalid_request_error", "Failed to parse request body")
 		return
 	}
+	body = parsedReq.Body.Bytes()
 	if parsedReq.Model == "" {
 		h.anthropicErrorResponse(c, http.StatusBadRequest, "invalid_request_error", "model is required")
 		return
diff --git a/backend/internal/service/gateway_request.go b/backend/internal/service/gateway_request.go
index 1665b1fe47..4ffd5ee8e9 100644
--- a/backend/internal/service/gateway_request.go
+++ b/backend/internal/service/gateway_request.go
@@ -161,6 +161,18 @@ func setGatewayRequestRanges(parsed *ParsedRequest, protocol string, jsonStr str
 	}
 }
 
+const claudeCodeLongContextModelSuffix = "[1m]"
+
+// Claude Code treats [1m] as a client-side context selector and normally removes it
+// before provider requests. Normalize leaked suffixes, including its duplicated form.
+func normalizeClaudeCodeLongContextModel(model string) string {
+	for len(model) > len(claudeCodeLongContextModelSuffix) &&
+		strings.EqualFold(model[len(model)-len(claudeCodeLongContextModelSuffix):], claudeCodeLongContextModelSuffix) {
+		model = model[:len(model)-len(claudeCodeLongContextModelSuffix)]
+	}
+	return model
+}
+
 // parseGatewayRequestCurrentBody 只做标量和 raw range 轻量解析，不恢复 system/messages 对象图。
 func parseGatewayRequestCurrentBody(parsed *ParsedRequest, protocol string) error {
 	if parsed == nil || parsed.Body == nil {
@@ -183,6 +195,19 @@ func parseGatewayRequestCurrentBody(parsed *ParsedRequest, protocol string) erro
 			return fmt.Errorf("invalid model field type")
 		}
 		parsed.Model = modelResult.String()
+		if protocol == domain.PlatformAnthropic {
+			normalizedModel := normalizeClaudeCodeLongContextModel(parsed.Model)
+			if normalizedModel != parsed.Model {
+				normalizedBody, err := sjson.SetBytes(bodyBytes, "model", normalizedModel)
+				if err != nil {
+					return fmt.Errorf("normalize model field: %w", err)
+				}
+				parsed.Body.Replace(normalizedBody)
+				bodyBytes = normalizedBody
+				jsonStr = *(*string)(unsafe.Pointer(&bodyBytes))
+				parsed.Model = normalizedModel
+			}
+		}
 	}
 
 	streamResult := gjson.Get(jsonStr, "stream")
diff --git a/backend/internal/service/gateway_request_test.go b/backend/internal/service/gateway_request_test.go
index 3172b4d086..d4e010a5e8 100644
--- a/backend/internal/service/gateway_request_test.go
+++ b/backend/internal/service/gateway_request_test.go
@@ -77,6 +77,40 @@ func TestParseGatewayRequest_InvalidStreamType(t *testing.T) {
 	require.Error(t, err)
 }
 
+func TestParseGatewayRequest_AnthropicNormalizesClaudeCodeLongContextModelSuffix(t *testing.T) {
+	tests := []struct {
+		name  string
+		model string
+		want  string
+	}{
+		{name: "lowercase suffix", model: "claude-opus-4-8[1m]", want: "claude-opus-4-8"},
+		{name: "uppercase suffix", model: "claude-opus-4-8[1M]", want: "claude-opus-4-8"},
+		{name: "duplicated suffix", model: "claude-opus-4-8[1M][1m]", want: "claude-opus-4-8"},
+		{name: "suffix in middle", model: "claude-opus-4-8[1m]-preview", want: "claude-opus-4-8[1m]-preview"},
+		{name: "suffix only", model: "[1m]", want: "[1m]"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			body := []byte(fmt.Sprintf(`{"model":%q,"system":"test","messages":[{"role":"user","content":"hi"}]}`, tt.model))
+			parsed, err := ParseGatewayRequest(NewRequestBodyRef(body), domain.PlatformAnthropic)
+			require.NoError(t, err)
+			require.Equal(t, tt.want, parsed.Model)
+			require.Equal(t, tt.want, gjson.GetBytes(parsed.Body.Bytes(), "model").String())
+			require.Equal(t, `"test"`, string(parsed.SystemRaw()))
+			require.NotEmpty(t, parsed.MessagesRaw())
+		})
+	}
+}
+
+func TestParseGatewayRequest_NonAnthropicPreservesClaudeCodeLongContextModelSuffix(t *testing.T) {
+	body := []byte(`{"model":"claude-opus-4-8[1m]","input":"hi"}`)
+	parsed, err := ParseGatewayRequest(NewRequestBodyRef(body), "responses")
+	require.NoError(t, err)
+	require.Equal(t, "claude-opus-4-8[1m]", parsed.Model)
+	require.Equal(t, "claude-opus-4-8[1m]", gjson.GetBytes(parsed.Body.Bytes(), "model").String())
+}
+
 func TestParseGatewayRequest_ResponsesInput(t *testing.T) {
 	body := []byte(`{"model":"gpt-5.1","input":[{"type":"message","role":"user","content":[{"type":"input_text","text":"hello"}]}]}`)
 	parsed, err := ParseGatewayRequest(NewRequestBodyRef(body), "responses")