diff --git a/changelog.d/unreleased/1668.fixed.md b/changelog.d/unreleased/1668.fixed.md
new file mode 100644
index 0000000000..fa172e9c1c
--- /dev/null
+++ b/changelog.d/unreleased/1668.fixed.md
@@ -0,0 +1,17 @@
+---
+category: fixed
+issues:
+  - 1668
+affected:
+  - tests/CodeIndex.Tests/SqlitePoolSensitiveCollection.cs
+  - tests/CodeIndex.Tests/SqlitePoolCleanup.cs
+  - tests/CodeIndex.Tests/SqlitePoolSensitiveCollectionTests.cs
+---
+
+## English
+
+- **SQLite pool-sensitive tests now clear pooled handles at collection boundaries (#1668)** — the serialized xUnit collection now owns a cleanup fixture that clears SQLite pools before and after the collection, reducing stale pooled-handle leakage after failed tests.
+
+## 日本語
+
+- **SQLite pool sensitive テストが collection 境界で pooled handle を解放するようになりました (#1668)** — 直列化された xUnit collection が cleanup fixture を持ち、collection の前後で SQLite pool を clear するため、失敗したテスト後に stale な pooled handle が残るリスクを減らします。
diff --git a/tests/CodeIndex.Tests/SqlitePoolCleanup.cs b/tests/CodeIndex.Tests/SqlitePoolCleanup.cs
index a2a6ebd345..5c95622165 100644
--- a/tests/CodeIndex.Tests/SqlitePoolCleanup.cs
+++ b/tests/CodeIndex.Tests/SqlitePoolCleanup.cs
@@ -5,6 +5,7 @@ namespace CodeIndex.Tests;
 internal static class SqlitePoolCleanup
 {
     private static readonly object Gate = new();
+    private static Action _clearAllPools = SqliteConnection.ClearAllPools;
     private static int _activeExclusiveOwners;
     private static bool _clearPending;
 
@@ -23,15 +24,38 @@ internal static void ClearPoolsForWindowsFileRelease(bool callerOwnsExclusiveAcc
         if (!OperatingSystem.IsWindows())
             return;
 
+        ClearPools(callerOwnsExclusiveAccess, deferForActiveOwners: true);
+    }
+
+    internal static void ClearPoolsAtCollectionBoundary()
+    {
+        ClearPools(callerOwnsExclusiveAccess: true, deferForActiveOwners: false);
+    }
+
+    internal static IDisposable ReplaceClearAllPoolsForTesting(Action clearAllPools)
+    {
+        ArgumentNullException.ThrowIfNull(clearAllPools);
+
         lock (Gate)
         {
-            if (_activeExclusiveOwners > 0 && !callerOwnsExclusiveAccess)
+            var prior = _clearAllPools;
+            _clearAllPools = clearAllPools;
+            return new RestoreClearAllPools(prior);
+        }
+    }
+
+    private static void ClearPools(bool callerOwnsExclusiveAccess, bool deferForActiveOwners)
+    {
+        lock (Gate)
+        {
+            if (deferForActiveOwners && _activeExclusiveOwners > 0 && !callerOwnsExclusiveAccess)
             {
                 _clearPending = true;
                 return;
             }
 
-            SqliteConnection.ClearAllPools();
+            _clearPending = false;
+            _clearAllPools();
         }
     }
 
@@ -51,9 +75,27 @@ public void Dispose()
                 if (_activeExclusiveOwners == 0 && _clearPending)
                 {
                     _clearPending = false;
-                    SqliteConnection.ClearAllPools();
+                    _clearAllPools();
                 }
             }
         }
     }
+
+    private sealed class RestoreClearAllPools(Action prior) : IDisposable
+    {
+        private bool _disposed;
+
+        public void Dispose()
+        {
+            lock (Gate)
+            {
+                if (_disposed)
+                    return;
+
+                _disposed = true;
+                _clearAllPools = prior;
+                _clearPending = false;
+            }
+        }
+    }
 }
diff --git a/tests/CodeIndex.Tests/SqlitePoolSensitiveCollection.cs b/tests/CodeIndex.Tests/SqlitePoolSensitiveCollection.cs
index b10a828bda..7f1d08ad8c 100644
--- a/tests/CodeIndex.Tests/SqlitePoolSensitiveCollection.cs
+++ b/tests/CodeIndex.Tests/SqlitePoolSensitiveCollection.cs
@@ -1,6 +1,21 @@
 namespace CodeIndex.Tests;
 
 [CollectionDefinition("SQLite pool sensitive", DisableParallelization = true)]
-public sealed class SqlitePoolSensitiveCollection
+public sealed class SqlitePoolSensitiveCollection : ICollectionFixture<SqlitePoolSensitiveFixture>
 {
 }
+
+public sealed class SqlitePoolSensitiveFixture : IAsyncLifetime
+{
+    public Task InitializeAsync()
+    {
+        SqlitePoolCleanup.ClearPoolsAtCollectionBoundary();
+        return Task.CompletedTask;
+    }
+
+    public Task DisposeAsync()
+    {
+        SqlitePoolCleanup.ClearPoolsAtCollectionBoundary();
+        return Task.CompletedTask;
+    }
+}
diff --git a/tests/CodeIndex.Tests/SqlitePoolSensitiveCollectionTests.cs b/tests/CodeIndex.Tests/SqlitePoolSensitiveCollectionTests.cs
new file mode 100644
index 0000000000..c268681570
--- /dev/null
+++ b/tests/CodeIndex.Tests/SqlitePoolSensitiveCollectionTests.cs
@@ -0,0 +1,40 @@
+namespace CodeIndex.Tests;
+
+[Collection("SQLite pool sensitive")]
+public sealed class SqlitePoolSensitiveCollectionTests
+{
+    [Fact]
+    public void Collection_RegistersPoolCleanupFixture()
+    {
+        Assert.Contains(
+            typeof(SqlitePoolSensitiveCollection).GetInterfaces(),
+            static type => type.IsGenericType &&
+                type.GetGenericTypeDefinition() == typeof(ICollectionFixture<>) &&
+                type.GetGenericArguments()[0] == typeof(SqlitePoolSensitiveFixture));
+    }
+
+    [Fact]
+    public async Task Fixture_ClearsPoolsOnInitializeAndDispose()
+    {
+        var clearCount = 0;
+        using var _ = SqlitePoolCleanup.ReplaceClearAllPoolsForTesting(() => clearCount++);
+        var fixture = new SqlitePoolSensitiveFixture();
+
+        await fixture.InitializeAsync();
+        await fixture.DisposeAsync();
+
+        Assert.Equal(2, clearCount);
+    }
+
+    [Fact]
+    public void CollectionBoundaryClear_DoesNotDeferBehindActiveExclusiveOwner()
+    {
+        var clearCount = 0;
+        using var _ = SqlitePoolCleanup.ReplaceClearAllPoolsForTesting(() => clearCount++);
+        using var owner = SqlitePoolCleanup.EnterExclusiveOwner();
+
+        SqlitePoolCleanup.ClearPoolsAtCollectionBoundary();
+
+        Assert.Equal(1, clearCount);
+    }
+}