From b6154513bba2c7d933fc6c3fcd38706050f461cd Mon Sep 17 00:00:00 2001
From: tekkaya <86028633+tekkaya@users.noreply.github.com>
Date: Thu, 27 Aug 2026 16:35:59 -0700
Subject: [PATCH] Report missing activity timeout as BAD_REQUEST inside a Nexus
 operation handler

Previously, building StartActivityOptions with neither scheduleToCloseTimeout
nor startToCloseTimeout set always threw a plain IllegalArgumentException.
When that build() call happens inside a Nexus operation handler, that
exception isn't a recognized Nexus error type, so NexusTaskHandlerImpl's
catch-all surfaced it as an opaque HandlerException(INTERNAL), which the
caller retries until the operation's schedule-to-close timeout expires
instead of failing fast.

NexusTaskHandlerImpl.convertKnownFailures now maps any IllegalArgumentException
raised by handler code to a real HandlerException(BAD_REQUEST), matching the
pattern already used for header/operation-token parsing elsewhere in this
class and in TemporalOperationHandler/WorkflowRunOperationImpl. This fixes the
missing-timeout case without teaching the general-purpose, Nexus-agnostic
StartActivityOptions builder about Nexus, and it also covers every other
IllegalArgumentException a Nexus operation handler can throw (missing id,
empty task queue, negative start delay, etc.) with one change, regardless of
whether the handler is built via TemporalOperationHandler or a raw/sync
OperationHandler.
---
 .../internal/nexus/NexusTaskHandlerImpl.java  |  3 ++
 .../nexus/NexusTaskHandlerImplTest.java       | 40 +++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/temporal-sdk/src/main/java/io/temporal/internal/nexus/NexusTaskHandlerImpl.java b/temporal-sdk/src/main/java/io/temporal/internal/nexus/NexusTaskHandlerImpl.java
index 4d40183c27..c0a538da26 100644
--- a/temporal-sdk/src/main/java/io/temporal/internal/nexus/NexusTaskHandlerImpl.java
+++ b/temporal-sdk/src/main/java/io/temporal/internal/nexus/NexusTaskHandlerImpl.java
@@ -200,6 +200,9 @@ private void convertKnownFailures(Throwable e) {
       }
       throw new HandlerException(HandlerException.ErrorType.BAD_REQUEST, failure);
     }
+    if (failure instanceof IllegalArgumentException) {
+      throw new HandlerException(HandlerException.ErrorType.BAD_REQUEST, failure);
+    }
     if (failure instanceof ApplicationFailure) {
       if (((ApplicationFailure) failure).isNonRetryable()) {
         throw new HandlerException(
diff --git a/temporal-sdk/src/test/java/io/temporal/internal/nexus/NexusTaskHandlerImplTest.java b/temporal-sdk/src/test/java/io/temporal/internal/nexus/NexusTaskHandlerImplTest.java
index 2ddfa7fda1..5f71fb158e 100644
--- a/temporal-sdk/src/test/java/io/temporal/internal/nexus/NexusTaskHandlerImplTest.java
+++ b/temporal-sdk/src/test/java/io/temporal/internal/nexus/NexusTaskHandlerImplTest.java
@@ -162,6 +162,34 @@ public void startTaskWithUndeserializableInput() throws TimeoutException {
     Assert.assertFalse(e.isRetryable());
   }
 
+  @Test
+  public void startTaskHandlerMissingBothActivityTimeoutOptions() throws TimeoutException {
+    WorkflowClient client = mock(WorkflowClient.class);
+    NexusTaskHandlerImpl nexusTaskHandlerImpl =
+        new NexusTaskHandlerImpl(
+            client, NAMESPACE, TASK_QUEUE, dataConverter, new WorkerInterceptor[] {});
+    nexusTaskHandlerImpl.registerNexusServiceImplementations(
+        new Object[] {new ThrowingIllegalArgumentServiceImpl()});
+    nexusTaskHandlerImpl.start();
+
+    PollNexusTaskQueueResponse.Builder task =
+        PollNexusTaskQueueResponse.newBuilder()
+            .setRequest(
+                Request.newBuilder()
+                    .setStartOperation(
+                        StartOperationRequest.newBuilder()
+                            .setOperation("operation")
+                            .setService("TestNexusService1")
+                            .setPayload(dataConverter.toPayload("input").get())
+                            .build()));
+
+    NexusTaskHandler.Result result =
+        nexusTaskHandlerImpl.handle(new NexusTask(task, null, null), metricsScope);
+    HandlerException e = result.getHandlerException();
+    Assert.assertNotNull(e);
+    Assert.assertEquals(HandlerException.ErrorType.BAD_REQUEST, e.getErrorType());
+  }
+
   @Test
   public void startAsyncSyncOperation() throws TimeoutException {
     WorkflowClient client = mock(WorkflowClient.class);
@@ -405,6 +433,18 @@ public OperationHandler<String, String> operation() {
     }
   }
 
+  @ServiceImpl(service = TestNexusServices.TestNexusService1.class)
+  public class ThrowingIllegalArgumentServiceImpl {
+    @OperationImpl
+    public OperationHandler<String, String> operation() {
+      return OperationHandler.sync(
+          (ctx, details, input) -> {
+            throw new IllegalArgumentException(
+                "at least one of StartToCloseTimeout or ScheduleToCloseTimeout is required");
+          });
+    }
+  }
+
   @ServiceImpl(service = TestNexusServices.TestNexusService1.class)
   public class TestNexusServiceImpl {
     @OperationImpl