diff --git a/src/Wolfgang.Etl.Abstractions/ExtractorBase.cs b/src/Wolfgang.Etl.Abstractions/ExtractorBase.cs
index 652112c0..b176d6e7 100644
--- a/src/Wolfgang.Etl.Abstractions/ExtractorBase.cs
+++ b/src/Wolfgang.Etl.Abstractions/ExtractorBase.cs
@@ -215,6 +215,7 @@ public int SkipItemCount
     /// <inheritdoc/>
     public virtual IAsyncEnumerable<TSource> ExtractAsync()
     {
+        ThrowIfDisposed();
         return ExtractWithResetAsync(CancellationToken.None);
     }
 
@@ -223,6 +224,7 @@ public virtual IAsyncEnumerable<TSource> ExtractAsync()
     /// <inheritdoc/>
     public virtual IAsyncEnumerable<TSource> ExtractAsync(CancellationToken token)
     {
+        ThrowIfDisposed();
         return ExtractWithResetAsync(token);
     }
 
@@ -231,6 +233,7 @@ public virtual IAsyncEnumerable<TSource> ExtractAsync(CancellationToken token)
     /// <inheritdoc/>
     public virtual IAsyncEnumerable<TSource> ExtractAsync(IProgress<TProgress> progress)
     {
+        ThrowIfDisposed();
 #if NET6_0_OR_GREATER
         ArgumentNullException.ThrowIfNull(progress);
 #else
@@ -250,6 +253,7 @@ public virtual IAsyncEnumerable<TSource> ExtractAsync(IProgress<TProgress> progr
     /// <inheritdoc/>
     public virtual IAsyncEnumerable<TSource> ExtractAsync(IProgress<TProgress> progress, CancellationToken token)
     {
+        ThrowIfDisposed();
 #if NET6_0_OR_GREATER
         ArgumentNullException.ThrowIfNull(progress);
 #else
@@ -465,17 +469,30 @@ public void Dispose()
     /// <see langword="true"/> when called from <see cref="Dispose()"/> or <see cref="DisposeAsync"/>
     /// (dispose managed resources); <see langword="false"/> when called from a finalizer.
     /// </param>
-    // Stryker disable all: equivalent mutant — Dispose(bool) has an inert base body: _disposed has
-    // no other reader (nothing throws ObjectDisposedException). Removing the whole body, negating the
-    // guard, or dropping the assignment is all unobservable; derived overrides supply real behaviour.
     protected virtual void Dispose(bool disposing)
     {
         if (_disposed)
+        // Stryker disable once all: equivalent — dropping this guard block only skips a redundant,
+        // idempotent re-assignment of _disposed. The guard's negation and the assignment below are
+        // real and killable (covered by the use-after-dispose tests).
         {
+            // Stryker disable once all: equivalent — same reasoning; skipping the early return just
+            // re-runs the idempotent `_disposed = true`.
             return;
         }
 
         _disposed = true;
     }
-    // Stryker restore all
+
+
+    // Throws if this extractor has already been disposed. Reads _disposed, so the public entry
+    // points reject use-after-dispose (and give the Dispose(bool) idempotency guard an observable
+    // effect).
+    private void ThrowIfDisposed()
+    {
+        if (_disposed)
+        {
+            throw new ObjectDisposedException(GetType().FullName);
+        }
+    }
 }
diff --git a/src/Wolfgang.Etl.Abstractions/LoaderBase.cs b/src/Wolfgang.Etl.Abstractions/LoaderBase.cs
index 0655245d..ed037e7c 100644
--- a/src/Wolfgang.Etl.Abstractions/LoaderBase.cs
+++ b/src/Wolfgang.Etl.Abstractions/LoaderBase.cs
@@ -186,6 +186,7 @@ public int SkipItemCount
     /// <inheritdoc/>
     public virtual Task LoadAsync(IAsyncEnumerable<TDestination> items)
     {
+        ThrowIfDisposed();
 #if NET6_0_OR_GREATER
         ArgumentNullException.ThrowIfNull(items);
 #else
@@ -204,6 +205,7 @@ public virtual Task LoadAsync(IAsyncEnumerable<TDestination> items)
     /// <inheritdoc/>
     public virtual Task LoadAsync(IAsyncEnumerable<TDestination> items, CancellationToken token)
     {
+        ThrowIfDisposed();
 #if NET6_0_OR_GREATER
         ArgumentNullException.ThrowIfNull(items);
 #else
@@ -222,6 +224,7 @@ public virtual Task LoadAsync(IAsyncEnumerable<TDestination> items, Cancellation
     /// <inheritdoc/>
     public virtual Task LoadAsync(IAsyncEnumerable<TDestination> items, IProgress<TProgress> progress)
     {
+        ThrowIfDisposed();
 #if NET6_0_OR_GREATER
         ArgumentNullException.ThrowIfNull(items);
         ArgumentNullException.ThrowIfNull(progress);
@@ -246,6 +249,7 @@ public virtual Task LoadAsync(IAsyncEnumerable<TDestination> items, IProgress<TP
     /// <inheritdoc/>
     public virtual Task LoadAsync(IAsyncEnumerable<TDestination> items, IProgress<TProgress> progress, CancellationToken token)
     {
+        ThrowIfDisposed();
 #if NET6_0_OR_GREATER
         ArgumentNullException.ThrowIfNull(items);
         ArgumentNullException.ThrowIfNull(progress);
@@ -463,17 +467,29 @@ public void Dispose()
     /// <see langword="true"/> when called from <see cref="Dispose()"/> or <see cref="DisposeAsync"/>
     /// (dispose managed resources); <see langword="false"/> when called from a finalizer.
     /// </param>
-    // Stryker disable all: equivalent mutant — Dispose(bool) has an inert base body: _disposed has
-    // no other reader (nothing throws ObjectDisposedException). Removing the whole body, negating the
-    // guard, or dropping the assignment is all unobservable; derived overrides supply real behaviour.
     protected virtual void Dispose(bool disposing)
     {
         if (_disposed)
+        // Stryker disable once all: equivalent — dropping this guard block only skips a redundant,
+        // idempotent re-assignment of _disposed. The guard's negation and the assignment below are
+        // real and killable (covered by the use-after-dispose tests).
         {
+            // Stryker disable once all: equivalent — same reasoning; skipping the early return just
+            // re-runs the idempotent `_disposed = true`.
             return;
         }
 
         _disposed = true;
     }
-    // Stryker restore all
+
+
+    // Throws if this loader has already been disposed. Reads _disposed, so the public entry points
+    // reject use-after-dispose (and give the Dispose(bool) idempotency guard an observable effect).
+    private void ThrowIfDisposed()
+    {
+        if (_disposed)
+        {
+            throw new ObjectDisposedException(GetType().FullName);
+        }
+    }
 }
diff --git a/src/Wolfgang.Etl.Abstractions/TransformerBase.cs b/src/Wolfgang.Etl.Abstractions/TransformerBase.cs
index d78cc6b7..c6979007 100644
--- a/src/Wolfgang.Etl.Abstractions/TransformerBase.cs
+++ b/src/Wolfgang.Etl.Abstractions/TransformerBase.cs
@@ -191,6 +191,7 @@ public int SkipItemCount
     /// <inheritdoc/>
     public virtual IAsyncEnumerable<TDestination> TransformAsync(IAsyncEnumerable<TSource> items)
     {
+        ThrowIfDisposed();
 #if NET6_0_OR_GREATER
         ArgumentNullException.ThrowIfNull(items);
 #else
@@ -209,6 +210,7 @@ public virtual IAsyncEnumerable<TDestination> TransformAsync(IAsyncEnumerable<TS
     /// <inheritdoc/>
     public virtual IAsyncEnumerable<TDestination> TransformAsync(IAsyncEnumerable<TSource> items, CancellationToken token)
     {
+        ThrowIfDisposed();
 #if NET6_0_OR_GREATER
         ArgumentNullException.ThrowIfNull(items);
 #else
@@ -227,6 +229,7 @@ public virtual IAsyncEnumerable<TDestination> TransformAsync(IAsyncEnumerable<TS
     /// <inheritdoc/>
     public virtual IAsyncEnumerable<TDestination> TransformAsync(IAsyncEnumerable<TSource> items, IProgress<TProgress> progress)
     {
+        ThrowIfDisposed();
 #if NET6_0_OR_GREATER
         ArgumentNullException.ThrowIfNull(items);
         ArgumentNullException.ThrowIfNull(progress);
@@ -251,6 +254,7 @@ public virtual IAsyncEnumerable<TDestination> TransformAsync(IAsyncEnumerable<TS
     /// <inheritdoc/>
     public virtual IAsyncEnumerable<TDestination> TransformAsync(IAsyncEnumerable<TSource> items, IProgress<TProgress> progress, CancellationToken token)
     {
+        ThrowIfDisposed();
 #if NET6_0_OR_GREATER
         ArgumentNullException.ThrowIfNull(items);
         ArgumentNullException.ThrowIfNull(progress);
@@ -472,17 +476,30 @@ public void Dispose()
     /// <see langword="true"/> when called from <see cref="Dispose()"/> or <see cref="DisposeAsync"/>
     /// (dispose managed resources); <see langword="false"/> when called from a finalizer.
     /// </param>
-    // Stryker disable all: equivalent mutant — Dispose(bool) has an inert base body: _disposed has
-    // no other reader (nothing throws ObjectDisposedException). Removing the whole body, negating the
-    // guard, or dropping the assignment is all unobservable; derived overrides supply real behaviour.
     protected virtual void Dispose(bool disposing)
     {
         if (_disposed)
+        // Stryker disable once all: equivalent — dropping this guard block only skips a redundant,
+        // idempotent re-assignment of _disposed. The guard's negation and the assignment below are
+        // real and killable (covered by the use-after-dispose tests).
         {
+            // Stryker disable once all: equivalent — same reasoning; skipping the early return just
+            // re-runs the idempotent `_disposed = true`.
             return;
         }
 
         _disposed = true;
     }
-    // Stryker restore all
+
+
+    // Throws if this transformer has already been disposed. Reads _disposed, so the public entry
+    // points reject use-after-dispose (and give the Dispose(bool) idempotency guard an observable
+    // effect).
+    private void ThrowIfDisposed()
+    {
+        if (_disposed)
+        {
+            throw new ObjectDisposedException(GetType().FullName);
+        }
+    }
 }
diff --git a/tests/Wolfgang.Etl.Abstractions.Tests.Unit/DisposedGuardTests.cs b/tests/Wolfgang.Etl.Abstractions.Tests.Unit/DisposedGuardTests.cs
new file mode 100644
index 00000000..556dd6ce
--- /dev/null
+++ b/tests/Wolfgang.Etl.Abstractions.Tests.Unit/DisposedGuardTests.cs
@@ -0,0 +1,172 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.Runtime.CompilerServices;
+using System.Threading;
+using System.Threading.Tasks;
+using Wolfgang.Etl.Abstractions.Tests.Unit.Models;
+
+namespace Wolfgang.Etl.Abstractions.Tests.Unit;
+
+/// <summary>
+/// Covers the dispose contract added to the base classes: once disposed, the public entry points
+/// throw <see cref="ObjectDisposedException"/>, and <c>Dispose</c> is idempotent. This gives the
+/// <c>Dispose(bool)</c> idempotency guard (<c>if (_disposed) …; _disposed = true;</c>) an observable
+/// effect — a mutation that negates the guard, drops its block, or skips the assignment leaves the
+/// instance "not disposed" and the throw never happens.
+/// </summary>
+public sealed class DisposedGuardTests
+{
+    private static async IAsyncEnumerable<int> Empty()
+    {
+        await Task.CompletedTask;
+        yield break;
+    }
+
+
+    private static readonly IProgress<EtlProgress> Progress = new NoOpProgress();
+
+
+    [Fact]
+    public void LoaderBase_every_LoadAsync_overload_throws_after_Dispose()
+    {
+        var loader = new NoOpLoader();
+        loader.Dispose();
+
+        Assert.Throws<ObjectDisposedException>(() => { _ = loader.LoadAsync(Empty()); });
+        Assert.Throws<ObjectDisposedException>(() => { _ = loader.LoadAsync(Empty(), CancellationToken.None); });
+        Assert.Throws<ObjectDisposedException>(() => { _ = loader.LoadAsync(Empty(), Progress); });
+        Assert.Throws<ObjectDisposedException>(() => { _ = loader.LoadAsync(Empty(), Progress, CancellationToken.None); });
+    }
+
+
+    [Fact]
+    public async Task LoaderBase_LoadAsync_throws_after_DisposeAsync()
+    {
+        var loader = new NoOpLoader();
+        await loader.DisposeAsync();
+
+        Assert.Throws<ObjectDisposedException>(() => { _ = loader.LoadAsync(Empty()); });
+    }
+
+
+    [Fact]
+    public void ExtractorBase_every_ExtractAsync_overload_throws_after_Dispose()
+    {
+        var extractor = new NoOpExtractor();
+        extractor.Dispose();
+
+        Assert.Throws<ObjectDisposedException>(() => extractor.ExtractAsync());
+        Assert.Throws<ObjectDisposedException>(() => extractor.ExtractAsync(CancellationToken.None));
+        Assert.Throws<ObjectDisposedException>(() => extractor.ExtractAsync(Progress));
+        Assert.Throws<ObjectDisposedException>(() => extractor.ExtractAsync(Progress, CancellationToken.None));
+    }
+
+
+    [Fact]
+    public async Task ExtractorBase_ExtractAsync_throws_after_DisposeAsync()
+    {
+        var extractor = new NoOpExtractor();
+        await extractor.DisposeAsync();
+
+        Assert.Throws<ObjectDisposedException>(() => extractor.ExtractAsync());
+    }
+
+
+    [Fact]
+    public void TransformerBase_every_TransformAsync_overload_throws_after_Dispose()
+    {
+        var transformer = new NoOpTransformer();
+        transformer.Dispose();
+
+        Assert.Throws<ObjectDisposedException>(() => transformer.TransformAsync(Empty()));
+        Assert.Throws<ObjectDisposedException>(() => transformer.TransformAsync(Empty(), CancellationToken.None));
+        Assert.Throws<ObjectDisposedException>(() => transformer.TransformAsync(Empty(), Progress));
+        Assert.Throws<ObjectDisposedException>(() => transformer.TransformAsync(Empty(), Progress, CancellationToken.None));
+    }
+
+
+    [Fact]
+    public async Task TransformerBase_TransformAsync_throws_after_DisposeAsync()
+    {
+        var transformer = new NoOpTransformer();
+        await transformer.DisposeAsync();
+
+        Assert.Throws<ObjectDisposedException>(() => transformer.TransformAsync(Empty()));
+    }
+
+
+    [Fact]
+    public void Dispose_is_idempotent()
+    {
+        var loader = new NoOpLoader();
+
+        loader.Dispose();
+        var second = Record.Exception(() => loader.Dispose());
+
+        Assert.Null(second);
+    }
+
+
+    [Fact]
+    public void A_live_component_does_not_throw()
+    {
+        // Guards against a mutant that makes ThrowIfDisposed always throw (or the guard being
+        // inverted): a freshly-constructed, undisposed loader must accept a call.
+        var loader = new NoOpLoader();
+
+        var exception = Record.Exception(() => { _ = loader.LoadAsync(Empty()); });
+
+        Assert.Null(exception);
+    }
+
+
+    [ExcludeFromCodeCoverage]
+    private sealed class NoOpProgress : IProgress<EtlProgress>
+    {
+        public void Report(EtlProgress value)
+        {
+        }
+    }
+
+
+    [ExcludeFromCodeCoverage]
+    private sealed class NoOpLoader : LoaderBase<int, EtlProgress>
+    {
+        protected override Task LoadWorkerAsync(IAsyncEnumerable<int> items, CancellationToken token)
+            => Task.CompletedTask;
+
+        protected override EtlProgress CreateProgressReport() => new(CurrentItemCount);
+    }
+
+
+    [ExcludeFromCodeCoverage]
+    private sealed class NoOpExtractor : ExtractorBase<int, EtlProgress>
+    {
+#pragma warning disable CS1998 // async iterator with no yielded items is intentional
+        protected override async IAsyncEnumerable<int> ExtractWorkerAsync(
+            [EnumeratorCancellation] CancellationToken token)
+        {
+            yield break;
+        }
+#pragma warning restore CS1998
+
+        protected override EtlProgress CreateProgressReport() => new(CurrentItemCount);
+    }
+
+
+    [ExcludeFromCodeCoverage]
+    private sealed class NoOpTransformer : TransformerBase<int, int, EtlProgress>
+    {
+#pragma warning disable CS1998 // async iterator with no yielded items is intentional
+        protected override async IAsyncEnumerable<int> TransformWorkerAsync(
+            IAsyncEnumerable<int> items,
+            [EnumeratorCancellation] CancellationToken token)
+        {
+            yield break;
+        }
+#pragma warning restore CS1998
+
+        protected override EtlProgress CreateProgressReport() => new(CurrentItemCount);
+    }
+}