diff --git a/controllers/individual_signing.go b/controllers/individual_signing.go
index 29ddfb6..3c373ee 100644
--- a/controllers/individual_signing.go
+++ b/controllers/individual_signing.go
@@ -141,9 +141,8 @@ func (ctl *IndividualSigningController) Check() {
 		ctl.GetString(":link_id"), ctl.GetString("email"),
 	)
 
-	// 非 debug 模式时隐藏调试信息
+	// status 是权威状态字段，始终返回；调试信息仅在 debug 模式下返回
 	if !debug {
-		v.Status = ""
 		v.DebugInfo = nil
 	}
 
diff --git a/models/individual_signing.go b/models/individual_signing.go
index aa23155..d6ed21e 100644
--- a/models/individual_signing.go
+++ b/models/individual_signing.go
@@ -29,7 +29,7 @@ type IndividualSigningInfo struct {
 type IndividualSigned struct {
 	Type           string     `json:"type"`                      // "individual" 或 "corp"
 	Signed         bool       `json:"signed"`                    // 是否已签署过
-	VersionMatched bool       `json:"version_matched,omitempty"` // 签署是否当前有效（考虑宽限期）
+	VersionMatched bool       `json:"version_matched"`            // 签署是否当前有效（考虑宽限期），始终返回以兼容旧版本调用
 	Status         string     `json:"status"`                    // 内部状态："not_signed" | "valid" | "expired"
 	DebugInfo      *DebugInfo `json:"_debug,omitempty"`          // 调试信息（仅debug=true时返回）
 }
diff --git a/models/individual_signing_test.go b/models/individual_signing_test.go
new file mode 100644
index 0000000..db763d2
--- /dev/null
+++ b/models/individual_signing_test.go
@@ -0,0 +1,125 @@
+package models
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+// TestIndividualSignedJSONSerialization verifies that the Check API response
+// always includes signed, version_matched and status fields so that legacy
+// callers keep working and the new authoritative status field is always present.
+//
+// Requirement (#909): the response must look like
+//
+//	{"data":{"type":"corporation","signed":true,"version_matched":true,"status":"valid"}}
+//
+// for all three states (not_signed / valid / expired), signed and
+// version_matched must be present even when false.
+func TestIndividualSignedJSONSerialization(t *testing.T) {
+	tests := []struct {
+		name string
+		in   IndividualSigned
+		want map[string]interface{}
+	}{
+		{
+			name: "valid",
+			in: IndividualSigned{
+				Type:           "corporation",
+				Signed:         true,
+				VersionMatched: true,
+				Status:         "valid",
+			},
+			want: map[string]interface{}{
+				"type":            "corporation",
+				"signed":          true,
+				"version_matched": true,
+				"status":          "valid",
+			},
+		},
+		{
+			name: "expired keeps version_matched:false",
+			in: IndividualSigned{
+				Type:           "corporation",
+				Signed:         true,
+				VersionMatched: false,
+				Status:         "expired",
+			},
+			want: map[string]interface{}{
+				"type":            "corporation",
+				"signed":          true,
+				"version_matched": false,
+				"status":          "expired",
+			},
+		},
+		{
+			name: "not_signed keeps signed:false and version_matched:false",
+			in: IndividualSigned{
+				Type:           "individual",
+				Signed:         false,
+				VersionMatched: false,
+				Status:         "not_signed",
+			},
+			want: map[string]interface{}{
+				"type":            "individual",
+				"signed":          false,
+				"version_matched": false,
+				"status":          "not_signed",
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			raw, err := json.Marshal(tt.in)
+			if err != nil {
+				t.Fatalf("json.Marshal returned unexpected error: %v", err)
+			}
+
+			var got map[string]interface{}
+			if err := json.Unmarshal(raw, &got); err != nil {
+				t.Fatalf("json.Unmarshal returned unexpected error: %v", err)
+			}
+
+			for k, wantVal := range tt.want {
+				gotVal, ok := got[k]
+				if !ok {
+					t.Errorf("missing field %q in response: %s", k, string(raw))
+					continue
+				}
+				if gotVal != wantVal {
+					t.Errorf("field %q = %v (%T), want %v (%T)",
+						k, gotVal, gotVal, wantVal, wantVal)
+				}
+			}
+
+			if _, ok := got["_debug"]; ok {
+				t.Errorf("_debug should be omitted when DebugInfo is nil, got: %s", string(raw))
+			}
+		})
+	}
+}
+
+// TestIndividualSignedDebugInfoOmittedWhenNil ensures the debug payload is
+// only exposed when populated (i.e. debug=true).
+func TestIndividualSignedDebugInfoOmittedWhenNil(t *testing.T) {
+	in := IndividualSigned{
+		Type:           "individual",
+		Signed:         true,
+		VersionMatched: true,
+		Status:         "valid",
+	}
+
+	raw, err := json.Marshal(in)
+	if err != nil {
+		t.Fatalf("json.Marshal returned unexpected error: %v", err)
+	}
+
+	var got map[string]interface{}
+	if err := json.Unmarshal(raw, &got); err != nil {
+		t.Fatalf("json.Unmarshal returned unexpected error: %v", err)
+	}
+
+	if _, ok := got["_debug"]; ok {
+		t.Errorf("_debug must be omitted when nil, got: %s", string(raw))
+	}
+}