diff --git a/src/Oms.Application/Storage/FileStoragePath.cs b/src/Oms.Application/Storage/FileStoragePath.cs
index 45cae8f..a9af070 100644
--- a/src/Oms.Application/Storage/FileStoragePath.cs
+++ b/src/Oms.Application/Storage/FileStoragePath.cs
@@ -39,6 +39,37 @@ public static class FileStoragePath
         && (value.StartsWith("http://", StringComparison.OrdinalIgnoreCase)
             || value.StartsWith("https://", StringComparison.OrdinalIgnoreCase));
 
+    /// <summary>
+    /// 是否为本系统对象存储域名（自定义域 cos.* / 腾讯云默认域）。
+    /// 这类地址带临时签名，库内应存 object key，读出时重新签名；不可当外链原样返回。
+    /// </summary>
+    public static bool IsManagedObjectStorageUrl(string? value)
+    {
+        if (!IsAbsoluteUrl(value))
+        {
+            return false;
+        }
+
+        try
+        {
+            var host = new Uri(value!).Host;
+            if (string.IsNullOrWhiteSpace(host))
+            {
+                return false;
+            }
+
+            host = host.ToLowerInvariant();
+            return host.StartsWith("cos.", StringComparison.Ordinal)
+                   || host.Contains("myqcloud.com", StringComparison.Ordinal)
+                   || host.Contains("tencentcos.cn", StringComparison.Ordinal)
+                   || host.Contains("tencentcos.com", StringComparison.Ordinal);
+        }
+        catch (UriFormatException)
+        {
+            return false;
+        }
+    }
+
     /// <summary>
     /// 读取对象时尝试的 key：含/不含 <c>admin/</c> 前缀（自定义域路径常带 PathBase）。
     /// </summary>
diff --git a/src/Oms.Application/Storage/OmsObjectStorageExtensions.cs b/src/Oms.Application/Storage/OmsObjectStorageExtensions.cs
index 28910bc..20db8cc 100644
--- a/src/Oms.Application/Storage/OmsObjectStorageExtensions.cs
+++ b/src/Oms.Application/Storage/OmsObjectStorageExtensions.cs
@@ -8,7 +8,7 @@ namespace Oms.Application.Storage;
 public static class OmsObjectStorageExtensions
 {
     /// <summary>
-    /// 将 key / 相对路径规范为库内 object key；绝对外链原样返回；空返回 null。
+    /// 将 key / 相对路径规范为库内 object key；本系统 COS 签名 URL 剥签后存 key；其它绝对外链原样返回；空返回 null。
     /// </summary>
     public static string? ToStorageKey(string? keyOrUrl)
     {
@@ -23,6 +23,12 @@ public static class OmsObjectStorageExtensions
             return "0";
         }
 
+        // 私有桶签名 URL 会过期，禁止写入库；只保留 object key。
+        if (FileStoragePath.IsManagedObjectStorageUrl(raw))
+        {
+            return FileStoragePath.NormalizeKey(raw);
+        }
+
         if (FileStoragePath.IsAbsoluteUrl(raw))
         {
             return raw;
@@ -32,7 +38,7 @@ public static class OmsObjectStorageExtensions
     }
 
     /// <summary>
-    /// 临时访问地址。空值返回空串；外链原样返回；逻辑 key 走 <see cref="IObjectStorage.GetUrlAsync"/>。
+    /// 临时访问地址。空值返回空串；真正外链原样返回；逻辑 key / 本系统 COS URL 走 <see cref="IObjectStorage.GetUrlAsync"/> 重新签名。
     /// Local 存储目录不可写/不可读时降级返回 key，避免拖垮下单等主流程。
     /// </summary>
     public static async Task<string> GetPublicUrlAsync(
@@ -46,7 +52,12 @@ public static class OmsObjectStorageExtensions
         }
 
         var raw = keyOrUrl.Trim();
-        if (FileStoragePath.IsAbsoluteUrl(raw))
+        // 历史数据可能把带 q-sign 的完整 URL 存进库；直接返回会 AccessDenied/Request has expired。
+        if (FileStoragePath.IsManagedObjectStorageUrl(raw))
+        {
+            raw = FileStoragePath.NormalizeKey(raw);
+        }
+        else if (FileStoragePath.IsAbsoluteUrl(raw))
         {
             return raw;
         }
diff --git a/src/Oms.Tests/FileStoragePathTests.cs b/src/Oms.Tests/FileStoragePathTests.cs
index 07b0843..9a26ce1 100644
--- a/src/Oms.Tests/FileStoragePathTests.cs
+++ b/src/Oms.Tests/FileStoragePathTests.cs
@@ -1,4 +1,6 @@
+using Fake.ObjectStorage;
 using FluentAssertions;
+using Moq;
 using Oms.Application.Storage;
 
 namespace Oms.Tests;
@@ -16,4 +18,69 @@ public class FileStoragePathTests
         keys.Should().Contain("admin/uploads/prints/orders/IDE2610061059117673-20261006105912.pdf");
         keys.Should().Contain("uploads/prints/orders/IDE2610061059117673-20261006105912.pdf");
     }
+
+    [Theory]
+    [InlineData("https://cos.ideship.com/uploads/a.pdf?q-sign-algorithm=sha1", true)]
+    [InlineData("http://cos.test.ideship.com/admin/uploads/a.pdf", true)]
+    [InlineData("https://bucket-123.cos.ap-guangzhou.myqcloud.com/uploads/a.pdf", true)]
+    [InlineData("https://third-party.example.com/label.pdf", false)]
+    [InlineData("uploads/prints/orders/a.pdf", false)]
+    public void IsManagedObjectStorageUrl_ShouldDetectCosHosts(string value, bool expected)
+    {
+        FileStoragePath.IsManagedObjectStorageUrl(value).Should().Be(expected);
+    }
+
+    [Fact]
+    public void ToStorageKey_ShouldStripExpiredCosSignedUrlToObjectKey()
+    {
+        var expired =
+            "https://cos.ideship.com/uploads/prints/orders/IDE2610081704036507-20261008170404.pdf?q-sign-algorithm=sha1&q-sign-time=1;2";
+
+        OmsObjectStorageExtensions.ToStorageKey(expired)
+            .Should()
+            .Be("uploads/prints/orders/IDE2610081704036507-20261008170404.pdf");
+    }
+
+    [Fact]
+    public void ToStorageKey_ShouldKeepExternalAbsoluteUrl()
+    {
+        const string external = "https://third-party.example.com/label.pdf?token=1";
+        OmsObjectStorageExtensions.ToStorageKey(external).Should().Be(external);
+    }
+
+    [Fact]
+    public async Task GetPublicUrl_ShouldResignManagedCosAbsoluteUrl()
+    {
+        var expired =
+            "https://cos.ideship.com/uploads/prints/orders/IDE2610081704036507-20261008170404.pdf?q-sign-algorithm=sha1&q-sign-time=1;2";
+        const string fresh =
+            "https://cos.ideship.com/uploads/prints/orders/IDE2610081704036507-20261008170404.pdf?q-sign-algorithm=sha1&fresh=1";
+
+        var storage = new Mock<IObjectStorage>(MockBehavior.Strict);
+        storage
+            .Setup(x => x.GetUrlAsync(
+                "uploads/prints/orders/IDE2610081704036507-20261008170404.pdf",
+                It.IsAny<TimeSpan?>(),
+                It.IsAny<CancellationToken>()))
+            .ReturnsAsync(fresh);
+
+        var url = await storage.Object.GetPublicUrlAsync(expired);
+
+        url.Should().Be(fresh);
+        storage.VerifyAll();
+    }
+
+    [Fact]
+    public async Task GetPublicUrl_ShouldPassThroughExternalAbsoluteUrl()
+    {
+        const string external = "https://third-party.example.com/label.pdf";
+        var storage = new Mock<IObjectStorage>(MockBehavior.Strict);
+
+        var url = await storage.Object.GetPublicUrlAsync(external);
+
+        url.Should().Be(external);
+        storage.Verify(
+            x => x.GetUrlAsync(It.IsAny<string>(), It.IsAny<TimeSpan?>(), It.IsAny<CancellationToken>()),
+            Times.Never);
+    }
 }