fix(core): Keep remapped session trace baggage mutable

Copying session trace baggage for a transaction now creates mutable baggage so the transaction can populate DSC fields even if the ambient session baggage was already frozen by an earlier outgoing request.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: adinauer

sentry/src/main/java/io/sentry/Baggage.java

@@ -233,8 +233,8 @@ public Baggage(final @NotNull Baggage baggage) {
         baggage.sampleRate,
         sampleRand,
         baggage.thirdPartyHeader,
-        baggage.mutable,
-        baggage.shouldFreeze,
+        true,
+        false,
         baggage.logger);
   }
 

sentry/src/test/java/io/sentry/BaggageTest.kt

@@ -440,7 +440,7 @@ class BaggageTest {
   }
 
   @Test
-  fun `copy with overrides preserves frozen state`() {
+  fun `copy with overrides creates mutable baggage`() {
     val baggage =
       Baggage.fromHeader(
         "sentry-sample_rand=0.1,sentry-trace_id=75302ac48a024bde9a3b3734a82e36c8",
@@ -450,7 +450,8 @@ class BaggageTest {
 
     val copy = Baggage.copyWithOverrides(baggage, SentryId("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"), 0.2)
 
-    assertFalse(copy.isMutable)
+    assertTrue(copy.isMutable)
+    assertFalse(copy.isShouldFreeze)
     assertEquals("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa", copy.traceId)
     assertEquals(0.2, copy.sampleRand!!, 0.0001)
     assertEquals("75302ac48a024bde9a3b3734a82e36c8", baggage.traceId)

sentry/src/test/java/io/sentry/ScopesTest.kt

@@ -21,6 +21,7 @@ import io.sentry.test.createTestScopes
 import io.sentry.test.initForTest
 import io.sentry.util.HintUtils
 import io.sentry.util.StringUtils
+import io.sentry.util.TracingUtils
 import java.io.File
 import java.nio.file.Files
 import java.util.Queue
@@ -1865,6 +1866,47 @@ class ScopesTest {
     assertNull(transaction.root.spanContext.parentSpanId)
   }
 
+  @Test
+  fun `session trace transaction baggage is populated after scope baggage is frozen`() {
+    val scopes = generateScopes {
+      it.isEnableSessionTraceLifecycle = true
+      it.release = "1.0.0"
+      it.environment = "production"
+    }
+
+    scopes.startSession()
+
+    val sessionTraceId = AtomicReference<SentryId>()
+    val sessionSampleRand = AtomicReference<Double>()
+    val headersWithoutTransaction =
+      TracingUtils.traceIfAllowed(scopes, "https://sentry.io/hello", emptyList(), null)
+    assertNotNull(headersWithoutTransaction)
+    scopes.configureScope { scope ->
+      sessionTraceId.set(scope.propagationContext.traceId)
+      sessionSampleRand.set(scope.propagationContext.sampleRand)
+      assertFalse(scope.propagationContext.baggage!!.isMutable)
+    }
+
+    val firstTransaction =
+      scopes.startTransaction(TransactionContext("first transaction", "ui.load"))
+    assertSessionTraceBaggage(
+      firstTransaction,
+      scopes,
+      sessionTraceId.get(),
+      sessionSampleRand.get(),
+    )
+    firstTransaction.finish()
+
+    val secondTransaction =
+      scopes.startTransaction(TransactionContext("second transaction", "ui.action"))
+    assertSessionTraceBaggage(
+      secondTransaction,
+      scopes,
+      sessionTraceId.get(),
+      sessionSampleRand.get(),
+    )
+  }
+
   @Test
   fun `when startTransaction with bindToScope set to false, transaction is not attached to the scope`() {
     val scopes = generateScopes()
@@ -4408,6 +4450,30 @@ class ScopesTest {
     return createScopes(options)
   }
 
+  private fun assertSessionTraceBaggage(
+    transaction: ITransaction,
+    scopes: IScopes,
+    sessionTraceId: SentryId,
+    sessionSampleRand: Double,
+  ) {
+    assertTrue(transaction is SentryTracer)
+    assertEquals(sessionTraceId, transaction.root.spanContext.traceId)
+
+    val tracingHeaders =
+      TracingUtils.traceIfAllowed(scopes, "https://sentry.io/hello", emptyList(), transaction)
+    val baggage =
+      Baggage.fromHeader(tracingHeaders!!.baggageHeader!!.value, NoOpLogger.getInstance())
+
+    assertEquals(sessionTraceId.toString(), baggage.traceId)
+    assertEquals(transaction.name, baggage.transaction)
+    assertEquals("true", baggage.sampled)
+    assertEquals(1.0, baggage.sampleRate!!, 0.0001)
+    assertEquals(sessionSampleRand, baggage.sampleRand!!, 0.0001)
+    assertEquals("key", baggage.publicKey)
+    assertEquals("1.0.0", baggage.release)
+    assertEquals("production", baggage.environment)
+  }
+
   private fun getEnabledScopes(
     optionsConfiguration: Sentry.OptionsConfiguration<SentryOptions>? = null
   ): Triple<Scopes, ISentryClient, ILogger> {