From c354d318d13d8e73af4be2e8719be52b435cae77 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20P=C3=B6lz?=
 <38893694+Flash0ver@users.noreply.github.com>
Date: Mon, 21 Jul 2025 13:48:08 +0200
Subject: [PATCH 01/17] test: normalize ContinueTrace tests

---
 test/Sentry.Tests/HubTests.cs | 36 +++++++++++++++++++++++++++--------
 1 file changed, 28 insertions(+), 8 deletions(-)

diff --git a/test/Sentry.Tests/HubTests.cs b/test/Sentry.Tests/HubTests.cs
index 85bf533df9..7cedbddcf2 100644
--- a/test/Sentry.Tests/HubTests.cs
+++ b/test/Sentry.Tests/HubTests.cs
@@ -1176,7 +1176,7 @@ public void GetBaggage_NoSpanActive_ReturnsBaggageFromPropagationContext()
     }
 
     [Fact]
-    public void ContinueTrace_SetsPropagationContextAndReturnsTransactionContext()
+    public void ContinueTrace_ReceivesHeaders_SetsPropagationContextAndReturnsTransactionContext()
     {
         // Arrange
         var hub = _fixture.GetSut();
@@ -1210,6 +1210,25 @@ public void ContinueTrace_SetsPropagationContextAndReturnsTransactionContext()
         transactionContext.ParentSpanId.Should().Be(SpanId.Parse("2000000000000000"));
     }
 
+    [Fact]
+    public void ContinueTrace_DoesNotReceiveHeaders_CreatesRootTrace()
+    {
+        // Arrange
+        var hub = _fixture.GetSut();
+
+        // Act
+        var transactionContext = hub.ContinueTrace((SentryTraceHeader)null, (BaggageHeader)null, "test-name", "test-operation");
+
+        // Assert
+        transactionContext.Name.Should().Be("test-name");
+        transactionContext.Operation.Should().Be("test-operation");
+        transactionContext.SpanId.Should().NotBeNull();
+        transactionContext.ParentSpanId.Should().BeNull();
+        transactionContext.TraceId.Should().NotBeNull();
+        transactionContext.IsSampled.Should().BeNull();
+        transactionContext.IsParentSampled.Should().BeNull();
+    }
+
     [Fact]
     public void ContinueTrace_ReceivesHeadersAsStrings_SetsPropagationContextAndReturnsTransactionContext()
     {
@@ -1239,21 +1258,22 @@ public void ContinueTrace_ReceivesHeadersAsStrings_SetsPropagationContextAndRetu
     }
 
     [Fact]
-    public void ContinueTrace_DoesNotReceiveHeaders_CreatesRootTrace()
+    public void ContinueTrace_DoesNotReceiveHeadersAsStrings_CreatesRootTrace()
     {
         // Arrange
         var hub = _fixture.GetSut();
 
         // Act
-        var transactionContext = hub.ContinueTrace((string)null, null, "test-name");
+        var transactionContext = hub.ContinueTrace((string)null, (string)null, "test-name");
 
         // Assert
         transactionContext.Name.Should().Be("test-name");
-        transactionContext.SpanId.Should().NotBe(null);
-        transactionContext.ParentSpanId.Should().Be(null);
-        transactionContext.TraceId.Should().NotBe(null);
-        transactionContext.IsSampled.Should().Be(null);
-        transactionContext.IsParentSampled.Should().Be(null);
+        transactionContext.Operation.Should().BeEmpty();
+        transactionContext.SpanId.Should().NotBeNull();
+        transactionContext.ParentSpanId.Should().BeNull();
+        transactionContext.TraceId.Should().NotBeNull();
+        transactionContext.IsSampled.Should().BeNull();
+        transactionContext.IsParentSampled.Should().BeNull();
     }
 
     [Fact]

From 37908a3ecdb69916acf66ff63ba7cdf656bf899e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20P=C3=B6lz?=
 <38893694+Flash0ver@users.noreply.github.com>
Date: Mon, 21 Jul 2025 14:09:00 +0200
Subject: [PATCH 02/17] test: use Assertion over type-cast

---
 test/Sentry.Tests/HubTests.cs | 32 +++++++++++++++-----------------
 1 file changed, 15 insertions(+), 17 deletions(-)

diff --git a/test/Sentry.Tests/HubTests.cs b/test/Sentry.Tests/HubTests.cs
index 7cedbddcf2..687b3a39e7 100644
--- a/test/Sentry.Tests/HubTests.cs
+++ b/test/Sentry.Tests/HubTests.cs
@@ -708,8 +708,8 @@ public void StartTransaction_DynamicSamplingContextWithReplayId_UsesActiveReplay
         var transaction = hub.StartTransaction(transactionContext, new Dictionary<string, object>(), dsc);
 
         // Assert
-        var transactionTracer = ((TransactionTracer)transaction);
-        transactionTracer.IsSampled.Should().Be(true);
+        var transactionTracer = transaction.Should().BeOfType<TransactionTracer>().Subject;
+        transactionTracer.IsSampled.Should().BeTrue();
         transactionTracer.DynamicSamplingContext.Should().NotBeNull();
         foreach (var dscItem in dsc!.Items)
         {
@@ -743,7 +743,7 @@ public void StartTransaction_NoDynamicSamplingContext_UsesActiveReplaySessionId(
         var transaction = hub.StartTransaction(transactionContext, new Dictionary<string, object>());
 
         // Assert
-        var transactionTracer = ((TransactionTracer)transaction);
+        var transactionTracer = transaction.Should().BeOfType<TransactionTracer>().Subject;
         transactionTracer.SampleRand.Should().NotBeNull();
         transactionTracer.DynamicSamplingContext.Should().NotBeNull();
         if (replaySessionIsActive)
@@ -770,7 +770,7 @@ public void StartTransaction_NoDynamicSamplingContext_GeneratesSampleRand()
         var transaction = hub.StartTransaction(transactionContext, customContext);
 
         // Assert
-        var transactionTracer = ((TransactionTracer)transaction);
+        var transactionTracer = transaction.Should().BeOfType<TransactionTracer>().Subject;
         transactionTracer.SampleRand.Should().NotBeNull();
         transactionTracer.DynamicSamplingContext.Should().NotBeNull();
         transactionTracer.DynamicSamplingContext!.Items.Should().ContainKey("sample_rand");
@@ -789,7 +789,7 @@ public void StartTransaction_DynamicSamplingContextWithoutSampleRand_SampleRandN
         var transaction = hub.StartTransaction(transactionContext, new Dictionary<string, object>(), DynamicSamplingContext.Empty);
 
         // Assert
-        var transactionTracer = ((TransactionTracer)transaction);
+        var transactionTracer = transaction.Should().BeOfType<TransactionTracer>().Subject;
         transactionTracer.SampleRand.Should().NotBeNull();
         transactionTracer.DynamicSamplingContext.Should().NotBeNull();
         // See https://develop.sentry.dev/sdk/telemetry/traces/dynamic-sampling-context/#freezing-dynamic-sampling-context
@@ -818,8 +818,8 @@ public void StartTransaction_DynamicSamplingContextWithSampleRand_InheritsSample
         var transaction = hub.StartTransaction(transactionContext, new Dictionary<string, object>(), dsc);
 
         // Assert
-        var transactionTracer = ((TransactionTracer)transaction);
-        transactionTracer.IsSampled.Should().Be(true);
+        var transactionTracer = transaction.Should().BeOfType<TransactionTracer>().Subject;
+        transactionTracer.IsSampled.Should().BeTrue();
         transactionTracer.SampleRate.Should().Be(0.4);
         transactionTracer.SampleRand.Should().Be(0.1234);
         transactionTracer.DynamicSamplingContext.Should().Be(dsc);
@@ -851,17 +851,16 @@ public void StartTransaction_TraceSampler_UsesSampleRand(double sampleRate, bool
         // Assert
         if (expectedIsSampled)
         {
-            transaction.Should().BeOfType<TransactionTracer>();
-            var transactionTracer = ((TransactionTracer)transaction);
-            transactionTracer.IsSampled.Should().Be(true);
+            var transactionTracer = transaction.Should().BeOfType<TransactionTracer>().Subject;
+            transactionTracer.IsSampled.Should().BeTrue();
             transactionTracer.SampleRate.Should().Be(sampleRate);
             transactionTracer.SampleRand.Should().Be(0.1234);
             transactionTracer.DynamicSamplingContext.Should().Be(dsc);
         }
         else
         {
-            transaction.Should().BeOfType<UnsampledTransaction>();
-            var unsampledTransaction = ((UnsampledTransaction)transaction);
+            var unsampledTransaction = transaction.Should().BeOfType<UnsampledTransaction>().Subject;
+            unsampledTransaction.IsSampled.Should().BeFalse();
             unsampledTransaction.SampleRate.Should().Be(sampleRate);
             unsampledTransaction.SampleRand.Should().Be(0.1234);
             unsampledTransaction.DynamicSamplingContext.Should().Be(dsc);
@@ -894,17 +893,16 @@ public void StartTransaction_StaticSampler_UsesSampleRand(double sampleRate, boo
         // Assert
         if (expectedIsSampled)
         {
-            transaction.Should().BeOfType<TransactionTracer>();
-            var transactionTracer = ((TransactionTracer)transaction);
-            transactionTracer.IsSampled.Should().Be(expectedIsSampled);
+            var transactionTracer = transaction.Should().BeOfType<TransactionTracer>().Subject;
+            transactionTracer.IsSampled.Should().BeTrue();
             transactionTracer.SampleRate.Should().Be(sampleRate);
             transactionTracer.SampleRand.Should().Be(0.1234);
             transactionTracer.DynamicSamplingContext.Should().Be(dsc);
         }
         else
         {
-            transaction.Should().BeOfType<UnsampledTransaction>();
-            var unsampledTransaction = ((UnsampledTransaction)transaction);
+            var unsampledTransaction = transaction.Should().BeOfType<UnsampledTransaction>().Subject;
+            unsampledTransaction.IsSampled.Should().BeFalse();
             unsampledTransaction.SampleRate.Should().Be(sampleRate);
             unsampledTransaction.SampleRand.Should().Be(0.1234);
             unsampledTransaction.DynamicSamplingContext.Should().Be(dsc);

From 23a45c20af9a9ad3630d67051c807fa77c1a602a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20P=C3=B6lz?=
 <38893694+Flash0ver@users.noreply.github.com>
Date: Mon, 21 Jul 2025 22:54:31 +0200
Subject: [PATCH 03/17] fix: DSC contains actual SampleRate

---
 src/Sentry/DynamicSamplingContext.cs          |  18 ++
 src/Sentry/Internal/Hub.cs                    |   7 +-
 .../SentryTracingMiddlewareTests.cs           |  15 +-
 .../SentrySpanProcessorTests.cs               |   3 +-
 test/Sentry.Tests/HubTests.cs                 | 170 ++++++++++++++++--
 5 files changed, 186 insertions(+), 27 deletions(-)

diff --git a/src/Sentry/DynamicSamplingContext.cs b/src/Sentry/DynamicSamplingContext.cs
index 7f1e1b82ba..e81550dadc 100644
--- a/src/Sentry/DynamicSamplingContext.cs
+++ b/src/Sentry/DynamicSamplingContext.cs
@@ -98,6 +98,24 @@ private DynamicSamplingContext(SentryId traceId,
 
     public BaggageHeader ToBaggageHeader() => BaggageHeader.Create(Items, useSentryPrefix: true);
 
+    public DynamicSamplingContext WithSampleRate(double sampleRate)
+    {
+        if (Items.TryGetValue("sample_rate", out var dscSampleRate))
+        {
+            if (double.TryParse(dscSampleRate, NumberStyles.Float, CultureInfo.InvariantCulture, out var rate))
+            {
+                if (Math.Abs(rate - sampleRate) > double.Epsilon)
+                {
+                    var items = Items.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
+                    items["sample_rate"] = sampleRate.ToString(CultureInfo.InvariantCulture);
+                    return new DynamicSamplingContext(items);
+                }
+            }
+        }
+
+        return this;
+    }
+
     public DynamicSamplingContext WithReplayId(IReplaySession? replaySession)
     {
         if (replaySession?.ActiveReplayId is not { } replayId || replayId == SentryId.Empty)
diff --git a/src/Sentry/Internal/Hub.cs b/src/Sentry/Internal/Hub.cs
index 67318abc54..2292def14a 100644
--- a/src/Sentry/Internal/Hub.cs
+++ b/src/Sentry/Internal/Hub.cs
@@ -172,8 +172,8 @@ internal ITransactionTracer StartTransaction(
 
         bool? isSampled = null;
         double? sampleRate = null;
-        var sampleRand = dynamicSamplingContext?.Items.TryGetValue("sample_rand", out var dscsampleRand) ?? false
-            ? double.Parse(dscsampleRand, NumberStyles.Float, CultureInfo.InvariantCulture)
+        var sampleRand = dynamicSamplingContext?.Items.TryGetValue("sample_rand", out var dscSampleRand) ?? false
+            ? double.Parse(dscSampleRand, NumberStyles.Float, CultureInfo.InvariantCulture)
             : SampleRandHelper.GenerateSampleRand(context.TraceId.ToString());
 
         // TracesSampler runs regardless of whether a decision has already been made, as it can be used to override it.
@@ -196,6 +196,9 @@ internal ITransactionTracer StartTransaction(
         sampleRate ??= _options.TracesSampleRate ?? 0.0;
         isSampled ??= context.IsSampled ?? SampleRandHelper.IsSampled(sampleRand, sampleRate.Value);
 
+        // Ensure the actual sampleRate is set on the provided DSC (https://github.com/getsentry/team-sdks/issues/117)
+        dynamicSamplingContext = dynamicSamplingContext?.WithSampleRate(sampleRate.Value);
+
         // Make sure there is a replayId (if available) on the provided DSC (if any).
         dynamicSamplingContext = dynamicSamplingContext?.WithReplayId(_replaySession);
 
diff --git a/test/Sentry.AspNetCore.Tests/SentryTracingMiddlewareTests.cs b/test/Sentry.AspNetCore.Tests/SentryTracingMiddlewareTests.cs
index f20b4cf1c5..3241942048 100644
--- a/test/Sentry.AspNetCore.Tests/SentryTracingMiddlewareTests.cs
+++ b/test/Sentry.AspNetCore.Tests/SentryTracingMiddlewareTests.cs
@@ -316,7 +316,7 @@ public async Task Baggage_header_propagates_to_outbound_requests(bool shouldProp
                 "sentry-trace_id=75302ac48a024bde9a3b3734a82e36c8, " +
                 "sentry-public_key=d4d82fc1c2c4032a83f3a29aa3a3aff, " +
                 "sentry-sample_rand=0.1234, " +
-                "sentry-sample_rate=0.5";
+                "sentry-sample_rate=1";
         }
         else
         {
@@ -395,13 +395,18 @@ public async Task Baggage_header_propagates_to_outbound_requests(bool shouldProp
     [Fact]
     public async Task Baggage_header_sets_dynamic_sampling_context()
     {
-        // incoming baggage header
-        const string baggage =
+        const string incomingBaggageHeader =
             "sentry-trace_id=75302ac48a024bde9a3b3734a82e36c8, " +
             "sentry-public_key=d4d82fc1c2c4032a83f3a29aa3a3aff, " +
             "sentry-sample_rand=0.1234, " +
             "sentry-sample_rate=0.5";
 
+        const string expectedBaggageHeader =
+            "sentry-trace_id=75302ac48a024bde9a3b3734a82e36c8, " +
+            "sentry-public_key=d4d82fc1c2c4032a83f3a29aa3a3aff, " +
+            "sentry-sample_rand=0.1234, " +
+            "sentry-sample_rate=1";
+
         // Arrange
         TransactionTracer transaction = null;
 
@@ -440,7 +445,7 @@ public async Task Baggage_header_sets_dynamic_sampling_context()
         {
             Headers =
             {
-                {"baggage", baggage}
+                {"baggage", incomingBaggageHeader}
             }
         };
 
@@ -449,7 +454,7 @@ public async Task Baggage_header_sets_dynamic_sampling_context()
         // Assert
         var dsc = transaction?.DynamicSamplingContext;
         Assert.NotNull(dsc);
-        Assert.Equal(baggage, dsc.ToBaggageHeader().ToString());
+        Assert.Equal(expectedBaggageHeader, dsc.ToBaggageHeader().ToString());
     }
 
     [Fact]
diff --git a/test/Sentry.OpenTelemetry.Tests/SentrySpanProcessorTests.cs b/test/Sentry.OpenTelemetry.Tests/SentrySpanProcessorTests.cs
index 360d3a6eed..c97e15f6a6 100644
--- a/test/Sentry.OpenTelemetry.Tests/SentrySpanProcessorTests.cs
+++ b/test/Sentry.OpenTelemetry.Tests/SentrySpanProcessorTests.cs
@@ -141,7 +141,8 @@ public void OnStart_Transaction_With_DynamicSamplingContext()
         {
             actual.Items["trace_id"].Should().Be(expected["trace_id"]);
             actual.Items["public_key"].Should().Be(expected["public_key"]);
-            actual.Items["sample_rate"].Should().Be(expected["sample_rate"]);
+            actual.Items["sample_rate"].Should().NotBe(expected["sample_rate"]);
+            actual.Items["sample_rate"].Should().Be(_fixture.Options.TracesSampleRate.ToString());
         }
     }
 
diff --git a/test/Sentry.Tests/HubTests.cs b/test/Sentry.Tests/HubTests.cs
index 687b3a39e7..3441e02ca0 100644
--- a/test/Sentry.Tests/HubTests.cs
+++ b/test/Sentry.Tests/HubTests.cs
@@ -681,6 +681,76 @@ public void StartTransaction_SameInstrumenter_SampledIn()
         transaction.IsSampled.Should().BeTrue();
     }
 
+    [Fact]
+    public void StartTransaction_DynamicSamplingContextWithSampleRate_UsesSampleRate()
+    {
+        // Arrange
+        var transactionContext = new TransactionContext("name", "operation");
+        var dsc = BaggageHeader.Create(new List<KeyValuePair<string, string>>
+        {
+            {"sentry-trace_id", "43365712692146d08ee11a729dfbcaca"},
+            {"sentry-public_key", "d4d82fc1c2c4032a83f3a29aa3a3aff"},
+            {"sentry-sample_rate", "0.5"},
+            {"sentry-sample_rand", "0.1234"},
+        }).CreateDynamicSamplingContext();
+
+        _fixture.Options.TracesSampler = _ => 0.5;
+        _fixture.Options.TracesSampleRate = 0.5;
+
+        var hub = _fixture.GetSut();
+
+        // Act
+        var transaction = hub.StartTransaction(transactionContext, new Dictionary<string, object>(), dsc);
+
+        // Assert
+        var transactionTracer = transaction.Should().BeOfType<TransactionTracer>().Subject;
+        transactionTracer.SampleRate.Should().Be(0.5);
+        transactionTracer.DynamicSamplingContext.Should().BeSameAs(dsc);
+    }
+
+    [Theory]
+    [InlineData(true, true)]
+    [InlineData(true, false)]
+    [InlineData(false, true)]
+    [InlineData(false, false)]
+    public void StartTransaction_DynamicSamplingContextWithSampleRate_UsesActualSampleRate(bool useTracesSampler, bool useTracesSampleRate)
+    {
+        // Arrange
+        var transactionContext = new TransactionContext("name", "operation");
+        var dsc = BaggageHeader.Create(new List<KeyValuePair<string, string>>
+        {
+            {"sentry-trace_id", "43365712692146d08ee11a729dfbcaca"},
+            {"sentry-public_key", "d4d82fc1c2c4032a83f3a29aa3a3aff"},
+            {"sentry-sample_rate", "0.5"},
+            {"sentry-sample_rand", "0.1234"},
+        }).CreateDynamicSamplingContext();
+
+        _fixture.Options.TracesSampler = useTracesSampler ? _ => 0.3 : _ => null;
+        _fixture.Options.TracesSampleRate = useTracesSampleRate ? 0.4 : null;
+
+        var hub = _fixture.GetSut();
+
+        // Act
+        var transaction = hub.StartTransaction(transactionContext, new Dictionary<string, object>(), dsc);
+
+        // Assert
+        if (useTracesSampler || useTracesSampleRate)
+        {
+            var expectedSampleRate = useTracesSampler ? 0.3 : 0.4;
+            var transactionTracer = transaction.Should().BeOfType<TransactionTracer>().Subject;
+            transactionTracer.SampleRate.Should().Be(expectedSampleRate);
+            transactionTracer.DynamicSamplingContext.Should().NotBeSameAs(dsc);
+            transactionTracer.DynamicSamplingContext.Should().BeEquivalentTo(dsc.ReplaceSampleRate(expectedSampleRate));
+        }
+        else
+        {
+            var unsampledTransaction = transaction.Should().BeOfType<UnsampledTransaction>().Subject;
+            unsampledTransaction.SampleRate.Should().Be(0.0);
+            unsampledTransaction.DynamicSamplingContext.Should().NotBeSameAs(dsc);
+            unsampledTransaction.DynamicSamplingContext.Should().BeEquivalentTo(dsc.ReplaceSampleRate(0));
+        }
+    }
+
     [Theory]
     [InlineData(true)]
     [InlineData(false)]
@@ -711,22 +781,15 @@ public void StartTransaction_DynamicSamplingContextWithReplayId_UsesActiveReplay
         var transactionTracer = transaction.Should().BeOfType<TransactionTracer>().Subject;
         transactionTracer.IsSampled.Should().BeTrue();
         transactionTracer.DynamicSamplingContext.Should().NotBeNull();
-        foreach (var dscItem in dsc!.Items)
+
+        var expectedDsc = dsc.ReplaceSampleRate(_fixture.Options.TracesSampleRate.Value);
+        if (replaySessionIsActive)
         {
-            if (dscItem.Key == "replay_id")
-            {
-                transactionTracer.DynamicSamplingContext!.Items["replay_id"].Should().Be(replaySessionIsActive
-                    // We overwrite the replay_id when we have an active replay session
-                    ? _fixture.ReplaySession.ActiveReplayId.ToString()
-                    // Otherwise we propagate whatever was in the baggage header
-                    : dscItem.Value);
-            }
-            else
-            {
-                transactionTracer.DynamicSamplingContext!.Items.Should()
-                    .Contain(kvp => kvp.Key == dscItem.Key && kvp.Value == dscItem.Value);
-            }
+            // We overwrite the replay_id when we have an active replay session
+            // Otherwise we propagate whatever was in the baggage header
+            expectedDsc = expectedDsc.ReplaceReplayId(_fixture.ReplaySession);
         }
+        transactionTracer.DynamicSamplingContext.Should().BeEquivalentTo(expectedDsc);
     }
 
     [Theory]
@@ -822,7 +885,8 @@ public void StartTransaction_DynamicSamplingContextWithSampleRand_InheritsSample
         transactionTracer.IsSampled.Should().BeTrue();
         transactionTracer.SampleRate.Should().Be(0.4);
         transactionTracer.SampleRand.Should().Be(0.1234);
-        transactionTracer.DynamicSamplingContext.Should().Be(dsc);
+        transactionTracer.DynamicSamplingContext.Should().NotBeSameAs(dsc);
+        transactionTracer.DynamicSamplingContext.Should().BeEquivalentTo(dsc.ReplaceSampleRate(0.4));
     }
 
     [Theory]
@@ -855,7 +919,8 @@ public void StartTransaction_TraceSampler_UsesSampleRand(double sampleRate, bool
             transactionTracer.IsSampled.Should().BeTrue();
             transactionTracer.SampleRate.Should().Be(sampleRate);
             transactionTracer.SampleRand.Should().Be(0.1234);
-            transactionTracer.DynamicSamplingContext.Should().Be(dsc);
+            transactionTracer.DynamicSamplingContext.Should().NotBeSameAs(dsc);
+            transactionTracer.DynamicSamplingContext.Should().BeEquivalentTo(dsc.ReplaceSampleRate(sampleRate));
         }
         else
         {
@@ -863,7 +928,8 @@ public void StartTransaction_TraceSampler_UsesSampleRand(double sampleRate, bool
             unsampledTransaction.IsSampled.Should().BeFalse();
             unsampledTransaction.SampleRate.Should().Be(sampleRate);
             unsampledTransaction.SampleRand.Should().Be(0.1234);
-            unsampledTransaction.DynamicSamplingContext.Should().Be(dsc);
+            unsampledTransaction.DynamicSamplingContext.Should().NotBeSameAs(dsc);
+            unsampledTransaction.DynamicSamplingContext.Should().BeEquivalentTo(dsc.ReplaceSampleRate(sampleRate));
         }
     }
 
@@ -897,7 +963,8 @@ public void StartTransaction_StaticSampler_UsesSampleRand(double sampleRate, boo
             transactionTracer.IsSampled.Should().BeTrue();
             transactionTracer.SampleRate.Should().Be(sampleRate);
             transactionTracer.SampleRand.Should().Be(0.1234);
-            transactionTracer.DynamicSamplingContext.Should().Be(dsc);
+            transactionTracer.DynamicSamplingContext.Should().NotBeSameAs(dsc);
+            transactionTracer.DynamicSamplingContext.Should().BeEquivalentTo(dsc.ReplaceSampleRate(sampleRate));
         }
         else
         {
@@ -905,7 +972,8 @@ public void StartTransaction_StaticSampler_UsesSampleRand(double sampleRate, boo
             unsampledTransaction.IsSampled.Should().BeFalse();
             unsampledTransaction.SampleRate.Should().Be(sampleRate);
             unsampledTransaction.SampleRand.Should().Be(0.1234);
-            unsampledTransaction.DynamicSamplingContext.Should().Be(dsc);
+            unsampledTransaction.DynamicSamplingContext.Should().NotBeSameAs(dsc);
+            unsampledTransaction.DynamicSamplingContext.Should().BeEquivalentTo(dsc.ReplaceSampleRate(sampleRate));
         }
     }
 
@@ -2108,3 +2176,67 @@ internal partial class HubTestsJsonContext : JsonSerializerContext
 {
 }
 #endif
+
+#nullable enable
+file static class DynamicSamplingContextExtensions
+{
+    public static DynamicSamplingContext ReplaceSampleRate(this DynamicSamplingContext? dsc, double sampleRate)
+    {
+        Assert.NotNull(dsc);
+
+        var value = sampleRate.ToString(CultureInfo.InvariantCulture);
+        return dsc.Replace("sentry-sample_rate", value);
+    }
+
+    public static DynamicSamplingContext ReplaceReplayId(this DynamicSamplingContext? dsc, IReplaySession replaySession)
+    {
+        Assert.NotNull(dsc);
+
+        if (!replaySession.ActiveReplayId.HasValue)
+        {
+            throw new InvalidOperationException($"No {nameof(IReplaySession.ActiveReplayId)}.");
+        }
+
+        var value = replaySession.ActiveReplayId.Value.ToString();
+        return dsc.Replace("sentry-replay_id", value);
+    }
+
+    private static DynamicSamplingContext Replace(this DynamicSamplingContext dsc, string key, string newValue)
+    {
+        var items = dsc.ToBaggageHeader().Members.ToList();
+        var index = items.FindSingleIndex(key);
+
+        var oldValue = items[index].Value;
+        if (oldValue == newValue)
+        {
+            throw new InvalidOperationException($"{key} already is {oldValue}.");
+        }
+
+        items[index] = new KeyValuePair<string, string>(key, newValue);
+
+        var baggage = BaggageHeader.Create(items);
+        var dynamicSamplingContext = DynamicSamplingContext.CreateFromBaggageHeader(baggage, null);
+        if (dynamicSamplingContext is null)
+        {
+            throw new InvalidOperationException($"Invalid {nameof(BaggageHeader)}: {baggage}");
+        }
+
+        return dynamicSamplingContext;
+    }
+
+    private static int FindSingleIndex(this List<KeyValuePair<string, string>> items, string key)
+    {
+        var index = items.FindIndex(item => item.Key == key);
+        if (index == -1)
+        {
+            throw new InvalidOperationException($"{key} not found.");
+        }
+
+        if (items.FindLastIndex(item => item.Key == key) != index)
+        {
+            throw new InvalidOperationException($"Duplicate {key} found.");
+        }
+
+        return index;
+    }
+}

From 5cace1fd23cc00337005f7bcbe346f2176773c6d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20P=C3=B6lz?=
 <38893694+Flash0ver@users.noreply.github.com>
Date: Mon, 21 Jul 2025 23:31:02 +0200
Subject: [PATCH 04/17] test: fix catch and handle failed Assertions

---
 test/Sentry.Tests/HubTests.cs | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/test/Sentry.Tests/HubTests.cs b/test/Sentry.Tests/HubTests.cs
index 3441e02ca0..a4a9c4f031 100644
--- a/test/Sentry.Tests/HubTests.cs
+++ b/test/Sentry.Tests/HubTests.cs
@@ -66,13 +66,13 @@ public void PushAndLockScope_DoesNotAffectOuterScope()
         var hub = _fixture.GetSut();
 
         // Act & assert
-        hub.ConfigureScope(s => Assert.False(s.Locked));
+        hub.ScopeManager.ConfigureScope(s => Assert.False(s.Locked));
         using (hub.PushAndLockScope())
         {
-            hub.ConfigureScope(s => Assert.True(s.Locked));
+            hub.ScopeManager.ConfigureScope(s => Assert.True(s.Locked));
         }
 
-        hub.ConfigureScope(s => Assert.False(s.Locked));
+        hub.ScopeManager.ConfigureScope(s => Assert.False(s.Locked));
     }
 
     [Fact]
@@ -1259,17 +1259,18 @@ public void ContinueTrace_ReceivesHeaders_SetsPropagationContextAndReturnsTransa
             {"sentry-sample_rate", "1.0"}
         });
 
-        hub.ConfigureScope(scope => scope.PropagationContext.TraceId.Should().Be("43365712692146d08ee11a729dfbcaca")); // Sanity check
+        hub.ScopeManager.ConfigureScope(scope => scope.PropagationContext.TraceId.Should().Be(SentryId.Parse("43365712692146d08ee11a729dfbcaca"))); // Sanity check
 
         // Act
         var transactionContext = hub.ContinueTrace(traceHeader, baggageHeader, "test-name");
 
         // Assert
-        hub.ConfigureScope(scope =>
+        hub.ScopeManager.ConfigureScope(scope =>
         {
             scope.PropagationContext.TraceId.Should().Be(SentryId.Parse("5bd5f6d346b442dd9177dce9302fd737"));
             scope.PropagationContext.ParentSpanId.Should().Be(SpanId.Parse("2000000000000000"));
             Assert.NotNull(scope.PropagationContext._dynamicSamplingContext);
+            scope.PropagationContext._dynamicSamplingContext.Items.Should().Contain(baggageHeader.GetSentryMembers());
         });
 
         transactionContext.TraceId.Should().Be(SentryId.Parse("5bd5f6d346b442dd9177dce9302fd737"));
@@ -1306,17 +1307,18 @@ public void ContinueTrace_ReceivesHeadersAsStrings_SetsPropagationContextAndRetu
         var traceHeader = "5bd5f6d346b442dd9177dce9302fd737-2000000000000000";
         var baggageHeader = "sentry-trace_id=5bd5f6d346b442dd9177dce9302fd737, sentry-public_key=49d0f7386ad645858ae85020e393bef3, sentry-sample_rate=1.0";
 
-        hub.ConfigureScope(scope => scope.PropagationContext.TraceId.Should().Be("43365712692146d08ee11a729dfbcaca")); // Sanity check
+        hub.ScopeManager.ConfigureScope(scope => scope.PropagationContext.TraceId.Should().Be(SentryId.Parse("43365712692146d08ee11a729dfbcaca"))); // Sanity check
 
         // Act
         var transactionContext = hub.ContinueTrace(traceHeader, baggageHeader, "test-name");
 
         // Assert
-        hub.ConfigureScope(scope =>
+        hub.ScopeManager.ConfigureScope(scope =>
         {
             scope.PropagationContext.TraceId.Should().Be(SentryId.Parse("5bd5f6d346b442dd9177dce9302fd737"));
             scope.PropagationContext.ParentSpanId.Should().Be(SpanId.Parse("2000000000000000"));
             Assert.NotNull(scope.PropagationContext._dynamicSamplingContext);
+            scope.PropagationContext._dynamicSamplingContext.ToBaggageHeader().Members.Should().Contain(BaggageHeader.TryParse(baggageHeader)!.Members);
         });
 
         transactionContext.TraceId.Should().Be(SentryId.Parse("5bd5f6d346b442dd9177dce9302fd737"));
@@ -1355,7 +1357,7 @@ public void CaptureTransaction_AfterTransactionFinishes_ResetsTransactionOnScope
         transaction.Finish();
 
         // Assert
-        hub.ConfigureScope(scope => scope.Transaction.Should().BeNull());
+        hub.ScopeManager.ConfigureScope(scope => scope.Transaction.Should().BeNull());
     }
 
 #nullable enable

From 4401a9808f6c845f3daf22b884a1447bd8ff7f6b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20P=C3=B6lz?=
 <38893694+Flash0ver@users.noreply.github.com>
Date: Mon, 21 Jul 2025 23:31:22 +0200
Subject: [PATCH 05/17] style: reformat HubTests

---
 test/Sentry.Tests/HubTests.cs | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/test/Sentry.Tests/HubTests.cs b/test/Sentry.Tests/HubTests.cs
index a4a9c4f031..00c7fc0192 100644
--- a/test/Sentry.Tests/HubTests.cs
+++ b/test/Sentry.Tests/HubTests.cs
@@ -173,14 +173,13 @@ public void CaptureException_TransactionFinished_Gets_DSC_From_LinkedSpan()
             {"sentry-sample_rate", "1.0"},
             {"sentry-trace_id", "75302ac48a024bde9a3b3734a82e36c8"},
             {"sentry-public_key", "d4d82fc1c2c4032a83f3a29aa3a3aff"},
-            {"sentry-replay_id","bfd31b89a59d41c99d96dc2baf840ecd"}
+            {"sentry-replay_id", "bfd31b89a59d41c99d96dc2baf840ecd"}
         }).CreateDynamicSamplingContext(_fixture.ReplaySession);
 
         var transaction = hub.StartTransaction(
             transactionContext,
             new Dictionary<string, object>(),
-            dsc
-            );
+            dsc);
         transaction.Finish(exception);
 
         // Act
@@ -767,7 +766,7 @@ public void StartTransaction_DynamicSamplingContextWithReplayId_UsesActiveReplay
             {"sentry-public_key", "d4d82fc1c2c4032a83f3a29aa3a3aff"},
             {"sentry-sampled", "true"},
             {"sentry-sample_rate", "0.5"}, // Required in the baggage header, but ignored by sampling logic
-            {"sentry-replay_id","bfd31b89a59d41c99d96dc2baf840ecd"}
+            {"sentry-replay_id", "bfd31b89a59d41c99d96dc2baf840ecd"}
         }).CreateDynamicSamplingContext(dummyReplaySession);
 
         _fixture.Options.TracesSampleRate = 1.0;

From 3197ab6139fbe9f1369e179cf07d922aab323f0c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20P=C3=B6lz?=
 <38893694+Flash0ver@users.noreply.github.com>
Date: Tue, 22 Jul 2025 00:30:19 +0200
Subject: [PATCH 06/17] test: fix HubTests

---
 test/Sentry.Tests/HubTests.cs | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/test/Sentry.Tests/HubTests.cs b/test/Sentry.Tests/HubTests.cs
index 00c7fc0192..99679c5fd5 100644
--- a/test/Sentry.Tests/HubTests.cs
+++ b/test/Sentry.Tests/HubTests.cs
@@ -1218,9 +1218,13 @@ public void GetBaggage_SpanActive_ReturnsBaggageFromSpan(bool isSampled)
 
         // Assert
         baggage.Should().NotBeNull();
-        Assert.Equal("43365712692146d08ee11a729dfbcaca", Assert.Contains("trace_id", dsc.Items));
-        Assert.Equal("d4d82fc1c2c4032a83f3a29aa3a3aff", Assert.Contains("public_key", dsc.Items));
-        Assert.Equal("0.0", Assert.Contains("sample_rate", dsc.Items));
+        var sampleRand = isSampled ? ((TransactionTracer)transaction).SampleRand : ((UnsampledTransaction)transaction).SampleRand;
+        baggage.Members.Should().Equal([
+            new KeyValuePair<string, string>("sentry-trace_id", "43365712692146d08ee11a729dfbcaca"),
+            new KeyValuePair<string, string>("sentry-public_key", "d4d82fc1c2c4032a83f3a29aa3a3aff"),
+            new KeyValuePair<string, string>("sentry-sample_rate", isSampled ? "1" : "0.0"),
+            new KeyValuePair<string, string>("sentry-sample_rand", sampleRand!.Value.ToString(CultureInfo.InvariantCulture)),
+        ]);
     }
 
     [Fact]
@@ -1237,7 +1241,7 @@ public void GetBaggage_NoSpanActive_ReturnsBaggageFromPropagationContext()
 
         // Assert
         baggage.Should().NotBeNull();
-        Assert.Contains("43365712692146d08ee11a729dfbcaca", baggage!.ToString());
+        Assert.Contains("sentry-trace_id=43365712692146d08ee11a729dfbcaca", baggage!.ToString());
     }
 
     [Fact]
@@ -1286,6 +1290,12 @@ public void ContinueTrace_DoesNotReceiveHeaders_CreatesRootTrace()
         var transactionContext = hub.ContinueTrace((SentryTraceHeader)null, (BaggageHeader)null, "test-name", "test-operation");
 
         // Assert
+        hub.ScopeManager.ConfigureScope(scope =>
+        {
+            Assert.Null(scope.PropagationContext.ParentSpanId);
+            Assert.Null(scope.PropagationContext._dynamicSamplingContext);
+        });
+
         transactionContext.Name.Should().Be("test-name");
         transactionContext.Operation.Should().Be("test-operation");
         transactionContext.SpanId.Should().NotBeNull();
@@ -1334,6 +1344,12 @@ public void ContinueTrace_DoesNotReceiveHeadersAsStrings_CreatesRootTrace()
         var transactionContext = hub.ContinueTrace((string)null, (string)null, "test-name");
 
         // Assert
+        hub.ScopeManager.ConfigureScope(scope =>
+        {
+            Assert.Null(scope.PropagationContext.ParentSpanId);
+            Assert.Null(scope.PropagationContext._dynamicSamplingContext);
+        });
+
         transactionContext.Name.Should().Be("test-name");
         transactionContext.Operation.Should().BeEmpty();
         transactionContext.SpanId.Should().NotBeNull();

From bc91dd3bf6cf844e239ac429892d95b9ce00a21b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20P=C3=B6lz?=
 <38893694+Flash0ver@users.noreply.github.com>
Date: Tue, 22 Jul 2025 00:47:20 +0200
Subject: [PATCH 07/17] docs: update CHANGELOG.md

---
 CHANGELOG.md               | 3 ++-
 src/Sentry/Internal/Hub.cs | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e6b899e623..2ca81f2e79 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 ### Fixes
 
+- Overwrite `sample_rate` of _Dynamic Sampling Context (DSC)_ when making sampling decisions ([#4374](https://github.com/getsentry/sentry-dotnet/pull/4374))
 - Native AOT: don't load SentryNative on unsupported platforms ([#4347](https://github.com/getsentry/sentry-dotnet/pull/4347))
 
 ### Dependencies
@@ -1244,7 +1245,7 @@ There are some functional differences when publishing Native AOT:
 
 ### Fixes
 
-- Resolved an isse where the SDK would throw an exception while attempting to set the DynamicSamplingContext but the context exists already. ([#2592](https://github.com/getsentry/sentry-dotnet/pull/2592))
+- Resolved an issue where the SDK would throw an exception while attempting to set the DynamicSamplingContext but the context exists already. ([#2592](https://github.com/getsentry/sentry-dotnet/pull/2592))
 
 ### Dependencies
 
diff --git a/src/Sentry/Internal/Hub.cs b/src/Sentry/Internal/Hub.cs
index 2292def14a..e4f60272f2 100644
--- a/src/Sentry/Internal/Hub.cs
+++ b/src/Sentry/Internal/Hub.cs
@@ -196,7 +196,7 @@ internal ITransactionTracer StartTransaction(
         sampleRate ??= _options.TracesSampleRate ?? 0.0;
         isSampled ??= context.IsSampled ?? SampleRandHelper.IsSampled(sampleRand, sampleRate.Value);
 
-        // Ensure the actual sampleRate is set on the provided DSC (https://github.com/getsentry/team-sdks/issues/117)
+        // Ensure the actual sampleRate is set on the provided DSC (https://github.com/getsentry/sentry-dotnet/pull/4374)
         dynamicSamplingContext = dynamicSamplingContext?.WithSampleRate(sampleRate.Value);
 
         // Make sure there is a replayId (if available) on the provided DSC (if any).

From 755bbef292827032bfd6d43712518d4bf3559f11 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20P=C3=B6lz?=
 <38893694+Flash0ver@users.noreply.github.com>
Date: Wed, 23 Jul 2025 16:34:37 +0200
Subject: [PATCH 08/17] test: skip failing test on Android & iOS (device tests)

---
 test/Sentry.Tests/HubTests.cs | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/test/Sentry.Tests/HubTests.cs b/test/Sentry.Tests/HubTests.cs
index 99679c5fd5..6077a25231 100644
--- a/test/Sentry.Tests/HubTests.cs
+++ b/test/Sentry.Tests/HubTests.cs
@@ -59,13 +59,17 @@ public void PushScope_BreadcrumbWithinScope_NotVisibleOutside()
         Assert.Empty(hub.ScopeManager.GetCurrent().Key.Breadcrumbs);
     }
 
-    [Fact]
+    [SkippableFact]
     public void PushAndLockScope_DoesNotAffectOuterScope()
     {
+#if __ANDROID__ || __IOS__
+        Skip.If(true, "Fails on both Android & iOS Device Tests");
+#endif
+
         // Arrange
         var hub = _fixture.GetSut();
 
-        // Act & assert
+        // Act & Assert
         hub.ScopeManager.ConfigureScope(s => Assert.False(s.Locked));
         using (hub.PushAndLockScope())
         {

From 62592339098ef1d91a8d71403a622f1805177ce1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20P=C3=B6lz?=
 <38893694+Flash0ver@users.noreply.github.com>
Date: Thu, 24 Jul 2025 12:04:47 +0200
Subject: [PATCH 09/17] fix: DSC sample_rate when sampling forced

---
 src/Sentry/DynamicSamplingContext.cs | 13 +++++++---
 src/Sentry/Internal/Hub.cs           |  2 +-
 test/Sentry.Tests/HubTests.cs        | 37 +++++++++++++++++++++++++++-
 3 files changed, 47 insertions(+), 5 deletions(-)

diff --git a/src/Sentry/DynamicSamplingContext.cs b/src/Sentry/DynamicSamplingContext.cs
index e81550dadc..f11d12e375 100644
--- a/src/Sentry/DynamicSamplingContext.cs
+++ b/src/Sentry/DynamicSamplingContext.cs
@@ -98,16 +98,23 @@ private DynamicSamplingContext(SentryId traceId,
 
     public BaggageHeader ToBaggageHeader() => BaggageHeader.Create(Items, useSentryPrefix: true);
 
-    public DynamicSamplingContext WithSampleRate(double sampleRate)
+    public DynamicSamplingContext WithSampleRate(bool? isSampled, double sampleRate)
     {
         if (Items.TryGetValue("sample_rate", out var dscSampleRate))
         {
             if (double.TryParse(dscSampleRate, NumberStyles.Float, CultureInfo.InvariantCulture, out var rate))
             {
-                if (Math.Abs(rate - sampleRate) > double.Epsilon)
+                var newSampleRate = isSampled switch
+                {
+                    true => 1.0,
+                    false => 0.0,
+                    _ => sampleRate,
+                };
+
+                if (Math.Abs(rate - newSampleRate) > double.Epsilon)
                 {
                     var items = Items.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
-                    items["sample_rate"] = sampleRate.ToString(CultureInfo.InvariantCulture);
+                    items["sample_rate"] = newSampleRate.ToString(CultureInfo.InvariantCulture);
                     return new DynamicSamplingContext(items);
                 }
             }
diff --git a/src/Sentry/Internal/Hub.cs b/src/Sentry/Internal/Hub.cs
index e4f60272f2..4aacc861b6 100644
--- a/src/Sentry/Internal/Hub.cs
+++ b/src/Sentry/Internal/Hub.cs
@@ -197,7 +197,7 @@ internal ITransactionTracer StartTransaction(
         isSampled ??= context.IsSampled ?? SampleRandHelper.IsSampled(sampleRand, sampleRate.Value);
 
         // Ensure the actual sampleRate is set on the provided DSC (https://github.com/getsentry/sentry-dotnet/pull/4374)
-        dynamicSamplingContext = dynamicSamplingContext?.WithSampleRate(sampleRate.Value);
+        dynamicSamplingContext = dynamicSamplingContext?.WithSampleRate(context.IsSampled, sampleRate.Value);
 
         // Make sure there is a replayId (if available) on the provided DSC (if any).
         dynamicSamplingContext = dynamicSamplingContext?.WithReplayId(_replaySession);
diff --git a/test/Sentry.Tests/HubTests.cs b/test/Sentry.Tests/HubTests.cs
index 6077a25231..43b8bd0e4a 100644
--- a/test/Sentry.Tests/HubTests.cs
+++ b/test/Sentry.Tests/HubTests.cs
@@ -63,7 +63,7 @@ public void PushScope_BreadcrumbWithinScope_NotVisibleOutside()
     public void PushAndLockScope_DoesNotAffectOuterScope()
     {
 #if __ANDROID__ || __IOS__
-        Skip.If(true, "Fails on both Android & iOS Device Tests");
+        Skip.If(true, "Fails on both Android & iOS Device Tests. See https://github.com/getsentry/sentry-dotnet/issues/4385.");
 #endif
 
         // Arrange
@@ -754,6 +754,41 @@ public void StartTransaction_DynamicSamplingContextWithSampleRate_UsesActualSamp
         }
     }
 
+    [SkippableTheory]
+    [InlineData(null, 0.3)]
+    [InlineData(true, 1.0)]
+    [InlineData(false, 0.0)]
+    public void StartTransaction_DynamicSamplingContextWithForcedSampling_UsesForcedValue(bool? isSampled, double expectedSampleRate)
+    {
+#if DEBUG
+        Skip.If(isSampled is false, "Should return an 'UnsampledTransaction', not a 'TransactionTracer'. See https://github.com/getsentry/sentry-dotnet/issues/4386.");
+#endif
+
+        // Arrange
+        var transactionContext = new TransactionContext("name", "operation", isSampled: isSampled);
+        var dsc = BaggageHeader.Create(new List<KeyValuePair<string, string>>
+        {
+            {"sentry-trace_id", "43365712692146d08ee11a729dfbcaca"},
+            {"sentry-public_key", "d4d82fc1c2c4032a83f3a29aa3a3aff"},
+            {"sentry-sample_rate", "0.5"},
+            {"sentry-sample_rand", "0.1234"},
+        }).CreateDynamicSamplingContext();
+
+        _fixture.Options.TracesSampler = _ => 0.3;
+        _fixture.Options.TracesSampleRate = 0.4;
+
+        var hub = _fixture.GetSut();
+
+        // Act
+        var transaction = hub.StartTransaction(transactionContext, new Dictionary<string, object>(), dsc);
+
+        // Assert
+        var transactionTracer = transaction.Should().BeOfType<TransactionTracer>().Subject;
+        transactionTracer.SampleRate.Should().Be(0.3);
+        transactionTracer.DynamicSamplingContext.Should().NotBeSameAs(dsc);
+        transactionTracer.DynamicSamplingContext.Should().BeEquivalentTo(dsc.ReplaceSampleRate(expectedSampleRate));
+    }
+
     [Theory]
     [InlineData(true)]
     [InlineData(false)]

From fd39406b1e0a298c3eceac93c35b99abd26f07fd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20P=C3=B6lz?=
 <38893694+Flash0ver@users.noreply.github.com>
Date: Thu, 24 Jul 2025 12:24:08 +0200
Subject: [PATCH 10/17] test: fix PushAndLockScope when GlobalMode

---
 test/Sentry.Tests/HubTests.cs | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/test/Sentry.Tests/HubTests.cs b/test/Sentry.Tests/HubTests.cs
index 43b8bd0e4a..77c4726b8a 100644
--- a/test/Sentry.Tests/HubTests.cs
+++ b/test/Sentry.Tests/HubTests.cs
@@ -59,13 +59,9 @@ public void PushScope_BreadcrumbWithinScope_NotVisibleOutside()
         Assert.Empty(hub.ScopeManager.GetCurrent().Key.Breadcrumbs);
     }
 
-    [SkippableFact]
+    [Fact]
     public void PushAndLockScope_DoesNotAffectOuterScope()
     {
-#if __ANDROID__ || __IOS__
-        Skip.If(true, "Fails on both Android & iOS Device Tests. See https://github.com/getsentry/sentry-dotnet/issues/4385.");
-#endif
-
         // Arrange
         var hub = _fixture.GetSut();
 
@@ -76,7 +72,14 @@ public void PushAndLockScope_DoesNotAffectOuterScope()
             hub.ScopeManager.ConfigureScope(s => Assert.True(s.Locked));
         }
 
-        hub.ScopeManager.ConfigureScope(s => Assert.False(s.Locked));
+        if (_fixture.Options.IsGlobalModeEnabled)
+        {
+            hub.ScopeManager.ConfigureScope(s => Assert.True(s.Locked));
+        }
+        else
+        {
+            hub.ScopeManager.ConfigureScope(s => Assert.False(s.Locked));
+        }
     }
 
     [Fact]

From cd5355b598ad65ec722d613979b5db81993018d5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20P=C3=B6lz?=
 <38893694+Flash0ver@users.noreply.github.com>
Date: Thu, 24 Jul 2025 18:09:46 +0200
Subject: [PATCH 11/17] fix: forced sampling is only considered when
 TracesSampler has not decided

---
 src/Sentry/Internal/Hub.cs    | 15 +++++--
 test/Sentry.Tests/HubTests.cs | 75 ++++++++++++-----------------------
 2 files changed, 37 insertions(+), 53 deletions(-)

diff --git a/src/Sentry/Internal/Hub.cs b/src/Sentry/Internal/Hub.cs
index 925383319d..8313129137 100644
--- a/src/Sentry/Internal/Hub.cs
+++ b/src/Sentry/Internal/Hub.cs
@@ -189,16 +189,23 @@ internal ITransactionTracer StartTransaction(
                 // The TracesSampler trumps all other sampling decisions (even the trace header)
                 sampleRate = samplerSampleRate;
                 isSampled = SampleRandHelper.IsSampled(sampleRand, sampleRate.Value);
+
+                // Ensure the actual sampleRate is set on the provided DSC (if any)
+                dynamicSamplingContext = dynamicSamplingContext?.WithSampleRate(null, sampleRate.Value);
             }
         }
 
         // If the sampling decision isn't made by a trace sampler we check the trace header first (from the context) or
         // finally fallback to Random sampling if the decision has been made by no other means
-        sampleRate ??= _options.TracesSampleRate ?? 0.0;
-        isSampled ??= context.IsSampled ?? SampleRandHelper.IsSampled(sampleRand, sampleRate.Value);
+        if (isSampled == null)
+        {
+            Debug.Assert(sampleRate == null);
+            sampleRate = _options.TracesSampleRate ?? 0.0;
+            isSampled = context.IsSampled ?? SampleRandHelper.IsSampled(sampleRand, sampleRate.Value);
 
-        // Ensure the actual sampleRate is set on the provided DSC (https://github.com/getsentry/sentry-dotnet/pull/4374)
-        dynamicSamplingContext = dynamicSamplingContext?.WithSampleRate(context.IsSampled, sampleRate.Value);
+            // Ensure the actual sampleRate is set on the provided DSC (if any)
+            dynamicSamplingContext = dynamicSamplingContext?.WithSampleRate(context.IsSampled, sampleRate.Value);
+        }
 
         // Make sure there is a replayId (if available) on the provided DSC (if any).
         dynamicSamplingContext = dynamicSamplingContext?.WithReplayId(_replaySession);
diff --git a/test/Sentry.Tests/HubTests.cs b/test/Sentry.Tests/HubTests.cs
index 5b1853b330..8ada4deb8d 100644
--- a/test/Sentry.Tests/HubTests.cs
+++ b/test/Sentry.Tests/HubTests.cs
@@ -714,15 +714,28 @@ public void StartTransaction_DynamicSamplingContextWithSampleRate_UsesSampleRate
         transactionTracer.DynamicSamplingContext.Should().BeSameAs(dsc);
     }
 
-    [Theory]
-    [InlineData(true, true)]
-    [InlineData(true, false)]
-    [InlineData(false, true)]
-    [InlineData(false, false)]
-    public void StartTransaction_DynamicSamplingContextWithSampleRate_UsesActualSampleRate(bool useTracesSampler, bool useTracesSampleRate)
+    [SkippableTheory]
+    [InlineData(null, 0.3, 0.4, true, 0.3)]
+    [InlineData(null, 0.3, null, true, 0.3)]
+    [InlineData(null, null, 0.4, true, 0.4)]
+    [InlineData(null, null, null, false, 0.0)]
+    [InlineData(true, 0.3, 0.4, true, 0.3)]
+    [InlineData(true, 0.3, null, true, 0.3)]
+    [InlineData(true, null, 0.4, true, 0.4, 1.0)]
+    [InlineData(true, null, null, true, 0.0, 1.0)]
+    [InlineData(false, 0.3, 0.4, true, 0.3)]
+    [InlineData(false, 0.3, null, true, 0.3)]
+    [InlineData(false, null, 0.4, false, 0.4, 0.0)]
+    [InlineData(false, null, null, false, 0.0, 0.0)]
+    public void StartTransaction_DynamicSamplingContextWithSampleRate_OverwritesSampleRate(bool? isSampled, double? tracesSampler, double? tracesSampleRate, bool expectedIsSampled, double expectedSampleRate, double? expectedDscSampleRate = null)
     {
+#if DEBUG
+        Skip.If(isSampled is false && expectedIsSampled, $"Forced sampling via {nameof(ITransactionContext.IsSampled)} is not considered when {nameof(SentryOptions.TracesSampler)} is used, resulting in `Debug.Assert` of {nameof(TransactionTracer)} `.ctor`.");
+#endif
+        expectedDscSampleRate ??= expectedSampleRate;
+
         // Arrange
-        var transactionContext = new TransactionContext("name", "operation");
+        var transactionContext = new TransactionContext("name", "operation", isSampled: isSampled);
         var dsc = BaggageHeader.Create(new List<KeyValuePair<string, string>>
         {
             {"sentry-trace_id", "43365712692146d08ee11a729dfbcaca"},
@@ -731,8 +744,8 @@ public void StartTransaction_DynamicSamplingContextWithSampleRate_UsesActualSamp
             {"sentry-sample_rand", "0.1234"},
         }).CreateDynamicSamplingContext();
 
-        _fixture.Options.TracesSampler = useTracesSampler ? _ => 0.3 : _ => null;
-        _fixture.Options.TracesSampleRate = useTracesSampleRate ? 0.4 : null;
+        _fixture.Options.TracesSampler = _ => tracesSampler;
+        _fixture.Options.TracesSampleRate = tracesSampleRate;
 
         var hub = _fixture.GetSut();
 
@@ -740,58 +753,22 @@ public void StartTransaction_DynamicSamplingContextWithSampleRate_UsesActualSamp
         var transaction = hub.StartTransaction(transactionContext, new Dictionary<string, object>(), dsc);
 
         // Assert
-        if (useTracesSampler || useTracesSampleRate)
+        if (expectedIsSampled)
         {
-            var expectedSampleRate = useTracesSampler ? 0.3 : 0.4;
             var transactionTracer = transaction.Should().BeOfType<TransactionTracer>().Subject;
             transactionTracer.SampleRate.Should().Be(expectedSampleRate);
             transactionTracer.DynamicSamplingContext.Should().NotBeSameAs(dsc);
-            transactionTracer.DynamicSamplingContext.Should().BeEquivalentTo(dsc.ReplaceSampleRate(expectedSampleRate));
+            transactionTracer.DynamicSamplingContext.Should().BeEquivalentTo(dsc.ReplaceSampleRate(expectedDscSampleRate.Value));
         }
         else
         {
             var unsampledTransaction = transaction.Should().BeOfType<UnsampledTransaction>().Subject;
-            unsampledTransaction.SampleRate.Should().Be(0.0);
+            unsampledTransaction.SampleRate.Should().Be(expectedSampleRate);
             unsampledTransaction.DynamicSamplingContext.Should().NotBeSameAs(dsc);
-            unsampledTransaction.DynamicSamplingContext.Should().BeEquivalentTo(dsc.ReplaceSampleRate(0));
+            unsampledTransaction.DynamicSamplingContext.Should().BeEquivalentTo(dsc.ReplaceSampleRate(expectedDscSampleRate.Value));
         }
     }
 
-    [SkippableTheory]
-    [InlineData(null, 0.3)]
-    [InlineData(true, 1.0)]
-    [InlineData(false, 0.0)]
-    public void StartTransaction_DynamicSamplingContextWithForcedSampling_UsesForcedValue(bool? isSampled, double expectedSampleRate)
-    {
-#if DEBUG
-        Skip.If(isSampled is false, "Should return an 'UnsampledTransaction', not a 'TransactionTracer'. See https://github.com/getsentry/sentry-dotnet/issues/4386.");
-#endif
-
-        // Arrange
-        var transactionContext = new TransactionContext("name", "operation", isSampled: isSampled);
-        var dsc = BaggageHeader.Create(new List<KeyValuePair<string, string>>
-        {
-            {"sentry-trace_id", "43365712692146d08ee11a729dfbcaca"},
-            {"sentry-public_key", "d4d82fc1c2c4032a83f3a29aa3a3aff"},
-            {"sentry-sample_rate", "0.5"},
-            {"sentry-sample_rand", "0.1234"},
-        }).CreateDynamicSamplingContext();
-
-        _fixture.Options.TracesSampler = _ => 0.3;
-        _fixture.Options.TracesSampleRate = 0.4;
-
-        var hub = _fixture.GetSut();
-
-        // Act
-        var transaction = hub.StartTransaction(transactionContext, new Dictionary<string, object>(), dsc);
-
-        // Assert
-        var transactionTracer = transaction.Should().BeOfType<TransactionTracer>().Subject;
-        transactionTracer.SampleRate.Should().Be(0.3);
-        transactionTracer.DynamicSamplingContext.Should().NotBeSameAs(dsc);
-        transactionTracer.DynamicSamplingContext.Should().BeEquivalentTo(dsc.ReplaceSampleRate(expectedSampleRate));
-    }
-
     [Theory]
     [InlineData(true)]
     [InlineData(false)]

From 8dbe5e36d47c74794fe2aec5a4345ed3c6a1b665 Mon Sep 17 00:00:00 2001
From: Flash0ver <38893694+Flash0ver@users.noreply.github.com>
Date: Fri, 25 Jul 2025 10:01:03 +0200
Subject: [PATCH 12/17] fix: no longer overwrite DSC sample_rate when upstream
 sampling decision has been made

---
 src/Sentry/DynamicSamplingContext.cs | 13 +++----------
 src/Sentry/Internal/Hub.cs           | 15 ++++-----------
 test/Sentry.Tests/HubTests.cs        | 15 +++++++--------
 3 files changed, 14 insertions(+), 29 deletions(-)

diff --git a/src/Sentry/DynamicSamplingContext.cs b/src/Sentry/DynamicSamplingContext.cs
index f11d12e375..e81550dadc 100644
--- a/src/Sentry/DynamicSamplingContext.cs
+++ b/src/Sentry/DynamicSamplingContext.cs
@@ -98,23 +98,16 @@ private DynamicSamplingContext(SentryId traceId,
 
     public BaggageHeader ToBaggageHeader() => BaggageHeader.Create(Items, useSentryPrefix: true);
 
-    public DynamicSamplingContext WithSampleRate(bool? isSampled, double sampleRate)
+    public DynamicSamplingContext WithSampleRate(double sampleRate)
     {
         if (Items.TryGetValue("sample_rate", out var dscSampleRate))
         {
             if (double.TryParse(dscSampleRate, NumberStyles.Float, CultureInfo.InvariantCulture, out var rate))
             {
-                var newSampleRate = isSampled switch
-                {
-                    true => 1.0,
-                    false => 0.0,
-                    _ => sampleRate,
-                };
-
-                if (Math.Abs(rate - newSampleRate) > double.Epsilon)
+                if (Math.Abs(rate - sampleRate) > double.Epsilon)
                 {
                     var items = Items.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
-                    items["sample_rate"] = newSampleRate.ToString(CultureInfo.InvariantCulture);
+                    items["sample_rate"] = sampleRate.ToString(CultureInfo.InvariantCulture);
                     return new DynamicSamplingContext(items);
                 }
             }
diff --git a/src/Sentry/Internal/Hub.cs b/src/Sentry/Internal/Hub.cs
index 8313129137..b2af31ef78 100644
--- a/src/Sentry/Internal/Hub.cs
+++ b/src/Sentry/Internal/Hub.cs
@@ -189,23 +189,16 @@ internal ITransactionTracer StartTransaction(
                 // The TracesSampler trumps all other sampling decisions (even the trace header)
                 sampleRate = samplerSampleRate;
                 isSampled = SampleRandHelper.IsSampled(sampleRand, sampleRate.Value);
-
-                // Ensure the actual sampleRate is set on the provided DSC (if any)
-                dynamicSamplingContext = dynamicSamplingContext?.WithSampleRate(null, sampleRate.Value);
             }
         }
 
         // If the sampling decision isn't made by a trace sampler we check the trace header first (from the context) or
         // finally fallback to Random sampling if the decision has been made by no other means
-        if (isSampled == null)
-        {
-            Debug.Assert(sampleRate == null);
-            sampleRate = _options.TracesSampleRate ?? 0.0;
-            isSampled = context.IsSampled ?? SampleRandHelper.IsSampled(sampleRand, sampleRate.Value);
+        sampleRate ??= _options.TracesSampleRate ?? 0.0;
+        isSampled ??= context.IsSampled ?? SampleRandHelper.IsSampled(sampleRand, sampleRate.Value);
 
-            // Ensure the actual sampleRate is set on the provided DSC (if any)
-            dynamicSamplingContext = dynamicSamplingContext?.WithSampleRate(context.IsSampled, sampleRate.Value);
-        }
+        // Ensure the actual sampleRate is set on the provided DSC (if any)
+        dynamicSamplingContext = dynamicSamplingContext?.WithSampleRate(sampleRate.Value);
 
         // Make sure there is a replayId (if available) on the provided DSC (if any).
         dynamicSamplingContext = dynamicSamplingContext?.WithReplayId(_replaySession);
diff --git a/test/Sentry.Tests/HubTests.cs b/test/Sentry.Tests/HubTests.cs
index 8ada4deb8d..aa3c0d5d68 100644
--- a/test/Sentry.Tests/HubTests.cs
+++ b/test/Sentry.Tests/HubTests.cs
@@ -721,18 +721,17 @@ public void StartTransaction_DynamicSamplingContextWithSampleRate_UsesSampleRate
     [InlineData(null, null, null, false, 0.0)]
     [InlineData(true, 0.3, 0.4, true, 0.3)]
     [InlineData(true, 0.3, null, true, 0.3)]
-    [InlineData(true, null, 0.4, true, 0.4, 1.0)]
-    [InlineData(true, null, null, true, 0.0, 1.0)]
+    [InlineData(true, null, 0.4, true, 0.4)]
+    [InlineData(true, null, null, true, 0.0)]
     [InlineData(false, 0.3, 0.4, true, 0.3)]
     [InlineData(false, 0.3, null, true, 0.3)]
-    [InlineData(false, null, 0.4, false, 0.4, 0.0)]
-    [InlineData(false, null, null, false, 0.0, 0.0)]
-    public void StartTransaction_DynamicSamplingContextWithSampleRate_OverwritesSampleRate(bool? isSampled, double? tracesSampler, double? tracesSampleRate, bool expectedIsSampled, double expectedSampleRate, double? expectedDscSampleRate = null)
+    [InlineData(false, null, 0.4, false, 0.4)]
+    [InlineData(false, null, null, false, 0.0)]
+    public void StartTransaction_DynamicSamplingContextWithSampleRate_OverwritesSampleRate(bool? isSampled, double? tracesSampler, double? tracesSampleRate, bool expectedIsSampled, double expectedSampleRate)
     {
 #if DEBUG
         Skip.If(isSampled is false && expectedIsSampled, $"Forced sampling via {nameof(ITransactionContext.IsSampled)} is not considered when {nameof(SentryOptions.TracesSampler)} is used, resulting in `Debug.Assert` of {nameof(TransactionTracer)} `.ctor`.");
 #endif
-        expectedDscSampleRate ??= expectedSampleRate;
 
         // Arrange
         var transactionContext = new TransactionContext("name", "operation", isSampled: isSampled);
@@ -758,14 +757,14 @@ public void StartTransaction_DynamicSamplingContextWithSampleRate_OverwritesSamp
             var transactionTracer = transaction.Should().BeOfType<TransactionTracer>().Subject;
             transactionTracer.SampleRate.Should().Be(expectedSampleRate);
             transactionTracer.DynamicSamplingContext.Should().NotBeSameAs(dsc);
-            transactionTracer.DynamicSamplingContext.Should().BeEquivalentTo(dsc.ReplaceSampleRate(expectedDscSampleRate.Value));
+            transactionTracer.DynamicSamplingContext.Should().BeEquivalentTo(dsc.ReplaceSampleRate(expectedSampleRate));
         }
         else
         {
             var unsampledTransaction = transaction.Should().BeOfType<UnsampledTransaction>().Subject;
             unsampledTransaction.SampleRate.Should().Be(expectedSampleRate);
             unsampledTransaction.DynamicSamplingContext.Should().NotBeSameAs(dsc);
-            unsampledTransaction.DynamicSamplingContext.Should().BeEquivalentTo(dsc.ReplaceSampleRate(expectedDscSampleRate.Value));
+            unsampledTransaction.DynamicSamplingContext.Should().BeEquivalentTo(dsc.ReplaceSampleRate(expectedSampleRate));
         }
     }
 

From fa43554acb70f8d7886ed5b974879a17ec80213b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20P=C3=B6lz?=
 <38893694+Flash0ver@users.noreply.github.com>
Date: Mon, 28 Jul 2025 11:10:41 +0200
Subject: [PATCH 13/17] fix: overwrite DSC sample_rate only when TracesSampler
 or TracesSampleRate reached a sampling decision

---
 src/Sentry/Internal/Hub.cs    | 20 +++++++++++----
 test/Sentry.Tests/HubTests.cs | 48 ++++++++++++++++++++++-------------
 2 files changed, 46 insertions(+), 22 deletions(-)

diff --git a/src/Sentry/Internal/Hub.cs b/src/Sentry/Internal/Hub.cs
index b2af31ef78..f5f7e7a7c8 100644
--- a/src/Sentry/Internal/Hub.cs
+++ b/src/Sentry/Internal/Hub.cs
@@ -188,17 +188,27 @@ internal ITransactionTracer StartTransaction(
             {
                 // The TracesSampler trumps all other sampling decisions (even the trace header)
                 sampleRate = samplerSampleRate;
-                isSampled = SampleRandHelper.IsSampled(sampleRand, sampleRate.Value);
+                isSampled = SampleRandHelper.IsSampled(sampleRand, samplerSampleRate);
+
+                // Ensure the actual sampleRate is set on the provided DSC (if any) when the TracesSampler reached a sampling decision
+                dynamicSamplingContext = dynamicSamplingContext?.WithSampleRate(samplerSampleRate);
             }
         }
 
         // If the sampling decision isn't made by a trace sampler we check the trace header first (from the context) or
         // finally fallback to Random sampling if the decision has been made by no other means
-        sampleRate ??= _options.TracesSampleRate ?? 0.0;
-        isSampled ??= context.IsSampled ?? SampleRandHelper.IsSampled(sampleRand, sampleRate.Value);
+        if (sampleRate == null)
+        {
+            Debug.Assert(isSampled == null);
+            sampleRate = _options.TracesSampleRate ?? 0.0;
+            isSampled = context.IsSampled ?? SampleRandHelper.IsSampled(sampleRand, sampleRate.Value);
 
-        // Ensure the actual sampleRate is set on the provided DSC (if any)
-        dynamicSamplingContext = dynamicSamplingContext?.WithSampleRate(sampleRate.Value);
+            if (context.IsSampled is null && _options.TracesSampleRate is not null)
+            {
+                // Ensure the actual sampleRate is set on the provided DSC (if any) when not IsSampled upstream but the TracesSampleRate reached a sampling decision
+                dynamicSamplingContext = dynamicSamplingContext?.WithSampleRate(_options.TracesSampleRate.Value);
+            }
+        }
 
         // Make sure there is a replayId (if available) on the provided DSC (if any).
         dynamicSamplingContext = dynamicSamplingContext?.WithReplayId(_replaySession);
diff --git a/test/Sentry.Tests/HubTests.cs b/test/Sentry.Tests/HubTests.cs
index aa3c0d5d68..6c3b78ddd8 100644
--- a/test/Sentry.Tests/HubTests.cs
+++ b/test/Sentry.Tests/HubTests.cs
@@ -715,19 +715,19 @@ public void StartTransaction_DynamicSamplingContextWithSampleRate_UsesSampleRate
     }
 
     [SkippableTheory]
-    [InlineData(null, 0.3, 0.4, true, 0.3)]
-    [InlineData(null, 0.3, null, true, 0.3)]
-    [InlineData(null, null, 0.4, true, 0.4)]
-    [InlineData(null, null, null, false, 0.0)]
-    [InlineData(true, 0.3, 0.4, true, 0.3)]
-    [InlineData(true, 0.3, null, true, 0.3)]
-    [InlineData(true, null, 0.4, true, 0.4)]
-    [InlineData(true, null, null, true, 0.0)]
-    [InlineData(false, 0.3, 0.4, true, 0.3)]
-    [InlineData(false, 0.3, null, true, 0.3)]
-    [InlineData(false, null, 0.4, false, 0.4)]
-    [InlineData(false, null, null, false, 0.0)]
-    public void StartTransaction_DynamicSamplingContextWithSampleRate_OverwritesSampleRate(bool? isSampled, double? tracesSampler, double? tracesSampleRate, bool expectedIsSampled, double expectedSampleRate)
+    [InlineData(null, 0.3, 0.4, true, 0.3, true)]
+    [InlineData(null, 0.3, null, true, 0.3, true)]
+    [InlineData(null, null, 0.4, true, 0.4, true)]
+    [InlineData(null, null, null, false, 0.0, false)]
+    [InlineData(true, 0.3, 0.4, true, 0.3, true)]
+    [InlineData(true, 0.3, null, true, 0.3, true)]
+    [InlineData(true, null, 0.4, true, 0.4, false)]
+    [InlineData(true, null, null, true, 0.0, false)]
+    [InlineData(false, 0.3, 0.4, true, 0.3, true)]
+    [InlineData(false, 0.3, null, true, 0.3, true)]
+    [InlineData(false, null, 0.4, false, 0.4, false)]
+    [InlineData(false, null, null, false, 0.0, false)]
+    public void StartTransaction_DynamicSamplingContextWithSampleRate_OverwritesSampleRate(bool? isSampled, double? tracesSampler, double? tracesSampleRate, bool expectedIsSampled, double expectedSampleRate, bool expectedDscOverwritten)
     {
 #if DEBUG
         Skip.If(isSampled is false && expectedIsSampled, $"Forced sampling via {nameof(ITransactionContext.IsSampled)} is not considered when {nameof(SentryOptions.TracesSampler)} is used, resulting in `Debug.Assert` of {nameof(TransactionTracer)} `.ctor`.");
@@ -756,15 +756,29 @@ public void StartTransaction_DynamicSamplingContextWithSampleRate_OverwritesSamp
         {
             var transactionTracer = transaction.Should().BeOfType<TransactionTracer>().Subject;
             transactionTracer.SampleRate.Should().Be(expectedSampleRate);
-            transactionTracer.DynamicSamplingContext.Should().NotBeSameAs(dsc);
-            transactionTracer.DynamicSamplingContext.Should().BeEquivalentTo(dsc.ReplaceSampleRate(expectedSampleRate));
+            if (expectedDscOverwritten)
+            {
+                transactionTracer.DynamicSamplingContext.Should().NotBeSameAs(dsc);
+                transactionTracer.DynamicSamplingContext.Should().BeEquivalentTo(dsc.ReplaceSampleRate(expectedSampleRate));
+            }
+            else
+            {
+                transactionTracer.DynamicSamplingContext.Should().BeSameAs(dsc);
+            }
         }
         else
         {
             var unsampledTransaction = transaction.Should().BeOfType<UnsampledTransaction>().Subject;
             unsampledTransaction.SampleRate.Should().Be(expectedSampleRate);
-            unsampledTransaction.DynamicSamplingContext.Should().NotBeSameAs(dsc);
-            unsampledTransaction.DynamicSamplingContext.Should().BeEquivalentTo(dsc.ReplaceSampleRate(expectedSampleRate));
+            if (expectedDscOverwritten)
+            {
+                unsampledTransaction.DynamicSamplingContext.Should().NotBeSameAs(dsc);
+                unsampledTransaction.DynamicSamplingContext.Should().BeEquivalentTo(dsc.ReplaceSampleRate(expectedSampleRate));
+            }
+            else
+            {
+                unsampledTransaction.DynamicSamplingContext.Should().BeSameAs(dsc);
+            }
         }
     }
 

From 23829431d069498ceaa2d4c1432d156273e2264e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20P=C3=B6lz?=
 <38893694+Flash0ver@users.noreply.github.com>
Date: Mon, 28 Jul 2025 11:14:24 +0200
Subject: [PATCH 14/17] ref: remove Debug.Assert

---
 src/Sentry/Internal/Hub.cs | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/Sentry/Internal/Hub.cs b/src/Sentry/Internal/Hub.cs
index f5f7e7a7c8..629e96128a 100644
--- a/src/Sentry/Internal/Hub.cs
+++ b/src/Sentry/Internal/Hub.cs
@@ -197,9 +197,8 @@ internal ITransactionTracer StartTransaction(
 
         // If the sampling decision isn't made by a trace sampler we check the trace header first (from the context) or
         // finally fallback to Random sampling if the decision has been made by no other means
-        if (sampleRate == null)
+        if (isSampled == null)
         {
-            Debug.Assert(isSampled == null);
             sampleRate = _options.TracesSampleRate ?? 0.0;
             isSampled = context.IsSampled ?? SampleRandHelper.IsSampled(sampleRand, sampleRate.Value);
 

From 8c5588f26d5b56e2e000da636fb751ecc5441e2a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20P=C3=B6lz?=
 <38893694+Flash0ver@users.noreply.github.com>
Date: Mon, 28 Jul 2025 11:35:56 +0200
Subject: [PATCH 15/17] docs: add comment to test

---
 test/Sentry.Tests/HubTests.cs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/test/Sentry.Tests/HubTests.cs b/test/Sentry.Tests/HubTests.cs
index 6c3b78ddd8..e5a24393e7 100644
--- a/test/Sentry.Tests/HubTests.cs
+++ b/test/Sentry.Tests/HubTests.cs
@@ -714,6 +714,11 @@ public void StartTransaction_DynamicSamplingContextWithSampleRate_UsesSampleRate
         transactionTracer.DynamicSamplingContext.Should().BeSameAs(dsc);
     }
 
+    // overwrite the 'sample_rate' of the Dynamic Sampling Context (DSC) when a sampling decisions is made in the downstream SDK
+    // 1. overwrite when 'TracesSampler' reaches a sampling decision
+    // 2. keep when a sampling decision has been made upstream (via 'TransactionContext.IsSampled')
+    // 3. overwrite when 'TracesSampleRate' reaches a sampling decision
+    // 4. keep otherwise
     [SkippableTheory]
     [InlineData(null, 0.3, 0.4, true, 0.3, true)]
     [InlineData(null, 0.3, null, true, 0.3, true)]

From 758028ccebba3d3037c6c43ffd65b0270a0cca94 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20P=C3=B6lz?=
 <38893694+Flash0ver@users.noreply.github.com>
Date: Wed, 30 Jul 2025 10:30:28 +0200
Subject: [PATCH 16/17] docs: update CHANGELOG

---
 CHANGELOG.md | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 01189e8d3d..11f2237078 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Changelog
 
+## Unreleased
+
+### Fixes
+
+- Update `sample_rate` of _Dynamic Sampling Context (DSC)_ when making sampling decisions ([#4374](https://github.com/getsentry/sentry-dotnet/pull/4374))
+
 ## 5.13.0
 
 ### Features
@@ -8,7 +14,6 @@
 
 ### Fixes
 
-- Overwrite `sample_rate` of _Dynamic Sampling Context (DSC)_ when making sampling decisions ([#4374](https://github.com/getsentry/sentry-dotnet/pull/4374))
 - Source context for class libraries when running on Android in Release mode ([#4294](https://github.com/getsentry/sentry-dotnet/pull/4294))
 - Native AOT: don't load SentryNative on unsupported platforms ([#4347](https://github.com/getsentry/sentry-dotnet/pull/4347))
 - Fixed issue introduced in release 5.12.0 that might prevent other middleware or user code from reading request bodies ([#4373](https://github.com/getsentry/sentry-dotnet/pull/4373))

From a13b7e0437ebf51775d6fb39204384315c23ad14 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20P=C3=B6lz?=
 <38893694+Flash0ver@users.noreply.github.com>
Date: Wed, 30 Jul 2025 11:00:51 +0200
Subject: [PATCH 17/17] fix: TransactionTracer was assumed to be considered
 even when TracesSampler applied

---
 src/Sentry/TransactionTracer.cs | 1 -
 test/Sentry.Tests/HubTests.cs   | 4 ----
 2 files changed, 5 deletions(-)

diff --git a/src/Sentry/TransactionTracer.cs b/src/Sentry/TransactionTracer.cs
index 5966a224da..767ccf977c 100644
--- a/src/Sentry/TransactionTracer.cs
+++ b/src/Sentry/TransactionTracer.cs
@@ -226,7 +226,6 @@ internal TransactionTracer(IHub hub, string name, string operation, TransactionN
     /// </summary>
     internal TransactionTracer(IHub hub, ITransactionContext context, TimeSpan? idleTimeout = null)
     {
-        Debug.Assert(context.IsSampled ?? true, "context.IsSampled should always be true when creating a TransactionTracer");
         _hub = hub;
         _options = _hub.GetSentryOptions();
         Name = context.Name;
diff --git a/test/Sentry.Tests/HubTests.cs b/test/Sentry.Tests/HubTests.cs
index e5a24393e7..91db9f4956 100644
--- a/test/Sentry.Tests/HubTests.cs
+++ b/test/Sentry.Tests/HubTests.cs
@@ -734,10 +734,6 @@ public void StartTransaction_DynamicSamplingContextWithSampleRate_UsesSampleRate
     [InlineData(false, null, null, false, 0.0, false)]
     public void StartTransaction_DynamicSamplingContextWithSampleRate_OverwritesSampleRate(bool? isSampled, double? tracesSampler, double? tracesSampleRate, bool expectedIsSampled, double expectedSampleRate, bool expectedDscOverwritten)
     {
-#if DEBUG
-        Skip.If(isSampled is false && expectedIsSampled, $"Forced sampling via {nameof(ITransactionContext.IsSampled)} is not considered when {nameof(SentryOptions.TracesSampler)} is used, resulting in `Debug.Assert` of {nameof(TransactionTracer)} `.ctor`.");
-#endif
-
         // Arrange
         var transactionContext = new TransactionContext("name", "operation", isSampled: isSampled);
         var dsc = BaggageHeader.Create(new List<KeyValuePair<string, string>>