diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a7ec52d..d9f1a85 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -39,7 +39,7 @@ jobs:
           dotnet run --project src/SharpClaw.Code.Cli/SharpClaw.Code.Cli.csproj --no-build --configuration Release -- test gates
       - name: Upload coverage
         if: matrix.os == 'ubuntu-latest'
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v7
         with:
           name: coverage-report
           path: ./coverage/**/coverage.cobertura.xml
diff --git a/docs/testing.md b/docs/testing.md
index 8d36c4e..3fd0a17 100644
--- a/docs/testing.md
+++ b/docs/testing.md
@@ -47,7 +47,7 @@ Scenarios are selected via request **`Metadata`** key **`parityScenario`** (**`P
 
 - **`streaming_text`** — deterministic deltas → `"Hello world"`
 - **`stream_failure`** — throws (turn fails; session may become **`Failed`**)
-- **`stream_slow`** — delays (cancellation / timeout scenarios)
+- **`stream_slow`** — emits an initial delta, then waits for cancellation (timeout / recovery scenarios)
 
 **`AddDeterministicMockModelProvider`** registers the provider + **`PostConfigure<ProviderCatalogOptions>`** so **`default`** / **`deterministic`** aliases point at the mock.
 
diff --git a/tests/SharpClaw.Code.MockProvider/DeterministicMockModelProvider.cs b/tests/SharpClaw.Code.MockProvider/DeterministicMockModelProvider.cs
index 0c4726f..37c5fff 100644
--- a/tests/SharpClaw.Code.MockProvider/DeterministicMockModelProvider.cs
+++ b/tests/SharpClaw.Code.MockProvider/DeterministicMockModelProvider.cs
@@ -72,8 +72,8 @@ private async IAsyncEnumerable<ProviderEvent> StreamEventsAsync(
             case ParityProviderScenario.StreamSlow:
                 await Task.Delay(500, cancellationToken).ConfigureAwait(false);
                 yield return CreateDelta(request, sequence: 1, "slow-start");
-                await Task.Delay(500, cancellationToken).ConfigureAwait(false);
-                yield return CreateTerminal(request, sequence: 2);
+                // Keep cancellation scenarios active even if a loaded runner observes the turn late.
+                await Task.Delay(Timeout.InfiniteTimeSpan, cancellationToken).ConfigureAwait(false);
                 yield break;
             case ParityProviderScenario.ToolCallRoundtrip:
                 // Check if the request already contains tool-result content (second iteration)
diff --git a/tests/SharpClaw.Code.MockProvider/ParityProviderScenario.cs b/tests/SharpClaw.Code.MockProvider/ParityProviderScenario.cs
index 8447e09..9b8d0d9 100644
--- a/tests/SharpClaw.Code.MockProvider/ParityProviderScenario.cs
+++ b/tests/SharpClaw.Code.MockProvider/ParityProviderScenario.cs
@@ -16,7 +16,7 @@ public static class ParityProviderScenario
     public const string StreamFailure = "stream_failure";
 
     /// <summary>
-    /// Delays long enough to let timeout and recovery scenarios cancel the stream.
+    /// Emits an initial delta, then waits for timeout and recovery scenarios to cancel the stream.
     /// </summary>
     public const string StreamSlow = "stream_slow";
 
diff --git a/tests/SharpClaw.Code.ParityHarness/ParityScenarioTests.cs b/tests/SharpClaw.Code.ParityHarness/ParityScenarioTests.cs
index 05ba6fc..7e9e6fa 100644
--- a/tests/SharpClaw.Code.ParityHarness/ParityScenarioTests.cs
+++ b/tests/SharpClaw.Code.ParityHarness/ParityScenarioTests.cs
@@ -334,7 +334,8 @@ private async Task RunPromptWithCancelAfterTurnStartAsync(
 
     private async Task WaitForActiveTurnAsync(ISessionStore store, CancellationToken cancellationToken)
     {
-        for (var attempt = 0; attempt < 100; attempt++)
+        // Startup is separate from the cancellation deadline and can be slow on loaded Windows runners.
+        for (var attempt = 0; attempt < 600; attempt++)
         {
             var session = await store.GetLatestAsync(_workspace, cancellationToken).ConfigureAwait(false);
             if (!string.IsNullOrWhiteSpace(session?.ActiveTurnId))
diff --git a/tests/SharpClaw.Code.UnitTests/Providers/DeterministicMockModelProviderTests.cs b/tests/SharpClaw.Code.UnitTests/Providers/DeterministicMockModelProviderTests.cs
index e56f74a..2c11d26 100644
--- a/tests/SharpClaw.Code.UnitTests/Providers/DeterministicMockModelProviderTests.cs
+++ b/tests/SharpClaw.Code.UnitTests/Providers/DeterministicMockModelProviderTests.cs
@@ -44,4 +44,24 @@ public async Task StartStreamAsync_should_emit_deterministic_ids_and_timestamps(
             new DateTimeOffset(2026, 4, 6, 0, 0, 0, TimeSpan.Zero).AddMilliseconds(2),
             new DateTimeOffset(2026, 4, 6, 0, 0, 0, TimeSpan.Zero).AddMilliseconds(3));
     }
+    [Fact]
+    public async Task Slow_stream_should_remain_active_until_canceled_after_delayed_observation()
+    {
+        var provider = new DeterministicMockModelProvider();
+        var request = new ProviderRequest(
+            "slow-request", "session", "turn", DeterministicMockModelProvider.ProviderNameConstant,
+            DeterministicMockModelProvider.DefaultModelId, "slow", null, OutputFormat.Text, null,
+            new Dictionary<string, string> { [ParityMetadataKeys.Scenario] = ParityProviderScenario.StreamSlow });
+        using var cancellation = new CancellationTokenSource();
+        var handle = await provider.StartStreamAsync(request, cancellation.Token);
+        await using var events = handle.Events.GetAsyncEnumerator(cancellation.Token);
+        Assert.True(await events.MoveNextAsync());
+
+        var nextEvent = events.MoveNextAsync().AsTask();
+        // Simulate observing the session after the original one-second fixture would have finished.
+        await Task.Delay(TimeSpan.FromMilliseconds(1500));
+        Assert.False(nextEvent.IsCompleted);
+        await cancellation.CancelAsync();
+        await Assert.ThrowsAnyAsync<OperationCanceledException>(async () => await nextEvent);
+    }
 }