diff --git a/backend/internal/service/claude_code_validator_test.go b/backend/internal/service/claude_code_validator_test.go
index f34348720f..09a31bebe3 100644
--- a/backend/internal/service/claude_code_validator_test.go
+++ b/backend/internal/service/claude_code_validator_test.go
@@ -185,6 +185,65 @@ func TestClaudeCodeValidator_BillingBlockStillRequiresClaudeCodeUA(t *testing.T)
 	require.False(t, ok)
 }
 
+// 新版 Claude Code CLI 已取消 cch=... 签名字段，billing block 形如
+// `x-anthropic-billing-header: cc_version=...; cc_entrypoint=cli;`（无 cch）。
+// 检测依赖前缀 + cc_entrypoint=cli，不依赖 cch，故无身份 prose 的子请求仍应被识别。
+// 这同时覆盖了本仓 mimicry 注入的新格式 block（见 buildBillingAttributionText）。
+func TestClaudeCodeValidator_BillingBlockRecognizedWithoutCCH(t *testing.T) {
+	monitorPrompt, err := os.ReadFile("testdata/security_monitor_system_prompt.txt")
+	require.NoError(t, err)
+
+	validator := NewClaudeCodeValidator()
+	require.Less(t, validator.bestSimilarityScore(string(monitorPrompt)), systemPromptThreshold)
+
+	req := httptest.NewRequest(http.MethodPost, "http://example.com/v1/messages", nil)
+	req.Header.Set("User-Agent", "claude-cli/2.1.162 (external, cli)")
+	req.Header.Set("X-App", "cli")
+	req.Header.Set("anthropic-beta", "claude-code-20250219")
+	req.Header.Set("anthropic-version", "2023-06-01")
+
+	ok := validator.Validate(req, map[string]any{
+		"model": "claude-3-5-haiku-20241022",
+		"system": []any{
+			map[string]any{
+				"type": "text",
+				// 注意：无 cch 段，对齐新版 CLI 与本仓新的注入格式。
+				"text": "x-anthropic-billing-header: cc_version=2.1.162.884; cc_entrypoint=cli;",
+			},
+			map[string]any{
+				"type": "text",
+				"text": string(monitorPrompt),
+			},
+		},
+		"metadata": map[string]any{
+			"user_id": claudeCodeMetadataUserIDJSON,
+		},
+	})
+	require.True(t, ok, "无 cch 的新版 billing block 仍应被识别为 Claude Code")
+}
+
+// 安全回归：去掉 cch 后检测并未放松——非 claude-cli UA 即便携带无 cch 的 billing block
+// 仍在 Step 1 被拒，ClaudeCodeOnly group 不会因此被仿冒绕过。
+func TestClaudeCodeValidator_NoCCHBlockStillRequiresClaudeCodeUA(t *testing.T) {
+	validator := NewClaudeCodeValidator()
+	req := httptest.NewRequest(http.MethodPost, "http://example.com/v1/messages", nil)
+	req.Header.Set("User-Agent", "curl/8.0.0")
+	req.Header.Set("X-App", "cli")
+	req.Header.Set("anthropic-beta", "claude-code-20250219")
+	req.Header.Set("anthropic-version", "2023-06-01")
+
+	ok := validator.Validate(req, map[string]any{
+		"model": "claude-3-5-haiku-20241022",
+		"system": []any{
+			map[string]any{
+				"type": "text",
+				"text": "x-anthropic-billing-header: cc_version=2.1.162.884; cc_entrypoint=cli;",
+			},
+		},
+	})
+	require.False(t, ok)
+}
+
 func TestClaudeCodeValidator_MessagesPathRejectsNonClaudeCodeUA(t *testing.T) {
 	validator := NewClaudeCodeValidator()
 	req := httptest.NewRequest(http.MethodPost, "http://example.com/v1/messages", nil)