diff --git a/cmd/libraryctl/main.go b/cmd/libraryctl/main.go
index b411579..f21a60e 100644
--- a/cmd/libraryctl/main.go
+++ b/cmd/libraryctl/main.go
@@ -732,7 +732,11 @@ func runCapture(ctx context.Context, opts options) error {
 		if err != nil {
 			return err
 		}
-		return checkNoUndeclaredWriter(ctx, images, declared)
+		app, err := containerEnv(ctx, opts.sourceApp)
+		if err != nil {
+			return err
+		}
+		return checkNoUndeclaredWriter(ctx, images, declared, opts.project, sourceTargetOf(app))
 	}
 	result, err := v071.CaptureLibrary(ctx, coordinator, archive, pool, search, objects, sourceReady,
 		v071.LibraryCaptureRequest{JobID: job, Scope: opts.scope,
@@ -809,21 +813,66 @@ func writerImageIDs(ctx context.Context, items []libraryfreeze.Service) ([]strin
 // checkNoUndeclaredWriter refuses to run when a running container uses a declared
 // writer image but is not part of the declared group: such a container could keep
 // writing during the maintenance window.
-func checkNoUndeclaredWriter(ctx context.Context, images []string, declared map[string]bool) error {
+func checkNoUndeclaredWriter(ctx context.Context, images []string, declared map[string]bool,
+	sourceProject string, source map[string]string) error {
 	for _, image := range images {
 		out, err := dockerOutput(ctx, "ps", "-q", "--filter", "ancestor="+image)
 		if err != nil {
 			return err
 		}
 		for _, id := range strings.Fields(out) {
-			if !declared[id] {
-				return fmt.Errorf("container %s uses a declared writer image but is not in the declared writer group", id[:12])
+			if declared[id] {
+				continue
+			}
+			project, err := dockerOutput(ctx, "inspect", "--format", `{{index .Config.Labels "com.docker.compose.project"}}`, id)
+			if err != nil {
+				return err
+			}
+			env, err := containerEnv(ctx, id)
+			if err != nil {
+				return err
+			}
+			if conflict, reason := undeclaredWriterConflict(false, project, sourceProject, env, source); conflict {
+				return fmt.Errorf("container %s uses a declared writer image but is not in the declared writer group: %s", id[:12], reason)
 			}
 		}
 	}
 	return nil
 }
 
+// sourceTargetOf 只取"写到哪儿"的身份：同一个数据库或同一个队列才是真冲突。
+func sourceTargetOf(env map[string]string) map[string]string {
+	return map[string]string{
+		"DB_HOST": env["DB_HOST"], "DB_NAME": env["DB_NAME"], "DB_PORT": env["DB_PORT"],
+		"REDIS_ADDR": env["REDIS_ADDR"], "REDIS_NAMESPACE": env["REDIS_NAMESPACE"],
+	}
+}
+
+// undeclaredWriterConflict 判断一个同镜像容器是否构成"未声明的并发写入者"。
+//
+// 同一 compose 项目或没有项目标签 ⇒ 无法证明隔离，直接冲突。
+// 另一个项目 ⇒ 只有数据目标（数据库/队列）与源相同才算冲突：
+// 镜像相同不等于写同一个库，本机共享业务栈与专用验收实例就是这种关系。
+func undeclaredWriterConflict(declared bool, project, sourceProject string, env, source map[string]string) (bool, string) {
+	if declared {
+		return false, ""
+	}
+	if project == "" {
+		return true, "没有 compose 项目标签，无法证明它不写同一个目标"
+	}
+	if project == sourceProject {
+		return true, "属于同一 compose 项目，却不是声明的写入服务"
+	}
+	if source["DB_HOST"] != "" && env["DB_HOST"] == source["DB_HOST"] && env["DB_NAME"] == source["DB_NAME"] {
+		return true, "另一个项目的同镜像容器指向同一个源数据库"
+	}
+	if source["REDIS_ADDR"] != "" && env["REDIS_ADDR"] == source["REDIS_ADDR"] &&
+		env["REDIS_NAMESPACE"] == source["REDIS_NAMESPACE"] {
+		return true, "另一个项目的同镜像容器共用同一个源队列"
+	}
+	return false, "另一套隔离栈（数据目标不同）"
+}
+
 func containerImageOf(ctx context.Context, id string) (string, error) {
 	image, err := dockerOutput(ctx, "inspect", "--format", "{{.Image}}", id)
 	if err != nil {
diff --git a/cmd/libraryctl/writer_check_test.go b/cmd/libraryctl/writer_check_test.go
new file mode 100644
index 0000000..276e811
--- /dev/null
+++ b/cmd/libraryctl/writer_check_test.go
@@ -0,0 +1,47 @@
+package main
+
+import (
+	"strings"
+	"testing"
+)
+
+// 同一台机器上可以有两套完全隔离的 WeKnora 栈共用同一个镜像（本机就是这样：
+// 共享业务栈 + 专用验收实例）。只按镜像判断"未声明的写入者"，会把另一套栈
+// 当成并发写入者，验收链永远开不了窗；但只看项目标签又会放过多起一个
+// 指向同一个库/队列的副本。判据要同时看归属与真实数据目标。
+func TestUndeclaredWriterConflict(t *testing.T) {
+	source := map[string]string{
+		"DB_HOST": "kgmaint-postgres", "DB_NAME": "kgmaint_target", "DB_PORT": "5432",
+		"REDIS_ADDR": "kgmaint-redis:6379", "REDIS_NAMESPACE": "kgmaint",
+	}
+	cases := []struct {
+		name       string
+		declared   bool
+		project    string
+		env        map[string]string
+		want       bool
+		reasonHint string
+	}{
+		{"已声明容器本身", true, "kgmaint-weknora", source, false, ""},
+		{"同项目里另起一份（不同名字）", false, "kgmaint-weknora", source, true, "同一 compose 项目"},
+		{"没有 compose 项目标签（docker run 的副本）", false, "", source, true, "没有 compose 项目标签"},
+		{"另一套隔离栈，数据目标不同", false, "weknora071full", map[string]string{
+			"DB_HOST": "WKNFull-postgres", "DB_NAME": "weknora_full", "REDIS_ADDR": "WKNFull-redis:6379", "REDIS_NAMESPACE": "weknora"},
+			false, ""},
+		{"另一套栈但指向同一个库", false, "other-project", map[string]string{
+			"DB_HOST": "kgmaint-postgres", "DB_NAME": "kgmaint_target", "REDIS_ADDR": "WKNFull-redis:6379"},
+			true, "同一个源数据库"},
+		{"另一套栈但共用同一队列", false, "other-project", map[string]string{
+			"DB_HOST": "other-pg", "DB_NAME": "other", "REDIS_ADDR": "kgmaint-redis:6379", "REDIS_NAMESPACE": "kgmaint"},
+			true, "同一个源队列"},
+	}
+	for _, tc := range cases {
+		conflict, reason := undeclaredWriterConflict(tc.declared, tc.project, "kgmaint-weknora", tc.env, source)
+		if conflict != tc.want {
+			t.Fatalf("%s: conflict=%v want %v (%s)", tc.name, conflict, tc.want, reason)
+		}
+		if tc.want && tc.reasonHint != "" && !strings.Contains(reason, tc.reasonHint) {
+			t.Fatalf("%s: reason %q should mention %q", tc.name, reason, tc.reasonHint)
+		}
+	}
+}