Add failing test: unsafe.run destroys caller thread's OTel context

BrianHotopp · claude · BrianHotopp · commit 1786a32731a8 · 2026-03-13T14:25:02.000-04:00
Runtime.default.unsafe.run() permanently wipes the calling thread's
Context.current() because TracingSupervisor.onSuspend() unconditionally
calls Context.root().makeCurrent() when the fiber completes.

This affects any code that calls unsafe.run from a thread with existing
OTel context — e.g. Doobie transactor threads (which have context from
the agent's Executor wrapping), Java callbacks, or cats-effect bridges.

Co-Authored-By: Claude Opus 4.6 &lt;noreply@anthropic.com&gt;
diff --git a/instrumentation/zio/zio-2.0/javaagent/src/test/scala/io/opentelemetry/javaagent/instrumentation/zio/v2_0/ZioRuntimeInstrumentationTest.scala b/instrumentation/zio/zio-2.0/javaagent/src/test/scala/io/opentelemetry/javaagent/instrumentation/zio/v2_0/ZioRuntimeInstrumentationTest.scala
@@ -9,6 +9,7 @@ import io.opentelemetry.instrumentation.testing.junit._
 import io.opentelemetry.instrumentation.testing.util.TelemetryDataUtil.orderByRootSpanName
 import io.opentelemetry.javaagent.instrumentation.zio.v2_0.ZioTestFixtures._
 import io.opentelemetry.sdk.testing.assertj.{SpanDataAssert, TraceAssert}
+import org.assertj.core.api.Assertions.assertThat
 import org.junit.jupiter.api.extension.RegisterExtension
 import org.junit.jupiter.api.{Test, TestInstance}
 
@@ -121,6 +122,19 @@ class ZioRuntimeInstrumentationTest {
     )
   }
 
+  @Test
+  def unsafeRunShouldNotDestroyCallerThreadContext(): Unit = {
+    val (traceIdBefore, traceIdAfter) = runUnsafeRunPreservesCallerContext()
+
+    assertThat(traceIdAfter)
+      .describedAs(
+        "Runtime.default.unsafe.run() should not destroy the calling thread's OTel context. " +
+          "onSuspend() calls Context.root().makeCurrent() when the fiber completes, " +
+          "which wipes pre-existing context on the calling thread."
+      )
+      .isEqualTo(traceIdBefore)
+  }
+
   private def assertTrace(f: TraceAssert => Any): Consumer[TraceAssert] =
     (t: TraceAssert) => f(t)
 
diff --git a/instrumentation/zio/zio-2.0/javaagent/src/test/scala/io/opentelemetry/javaagent/instrumentation/zio/v2_0/ZioTestFixtures.scala b/instrumentation/zio/zio-2.0/javaagent/src/test/scala/io/opentelemetry/javaagent/instrumentation/zio/v2_0/ZioTestFixtures.scala
@@ -122,6 +122,36 @@ object ZioTestFixtures {
     }
   }
 
+  /**
+   * Demonstrates that Runtime.default.unsafe.run() destroys the calling thread's
+   * OTel context. The onSuspend handler calls Context.root().makeCurrent() when
+   * the fiber completes, which wipes any pre-existing context on the calling thread.
+   *
+   * Returns (traceIdBefore, traceIdAfter) so the test can assert they match.
+   */
+  def runUnsafeRunPreservesCallerContext(): (String, String) = {
+    val span = tracer.spanBuilder("caller_span").startSpan()
+    val scope = span.makeCurrent()
+    try {
+      val traceIdBefore =
+        io.opentelemetry.api.trace.Span.current().getSpanContext.getTraceId
+
+      Unsafe.unsafe { implicit unsafe =>
+        zio.Runtime.default.unsafe
+          .run(ZIO.succeed("hello"))(Trace.empty, unsafe)
+          .getOrThrowFiberFailure()
+      }
+
+      val traceIdAfter =
+        io.opentelemetry.api.trace.Span.current().getSpanContext.getTraceId
+
+      span.end()
+      (traceIdBefore, traceIdAfter)
+    } finally {
+      scope.close()
+    }
+  }
+
   private val tracer: Tracer = GlobalOpenTelemetry.getTracer("test")
 
   private def childSpan(opName: String)(op: UIO[Unit]): UIO[Unit] =
