Include Exception Properties at FailureDetails

client/build.gradle

@@ -60,7 +60,8 @@ compileTestJava {
     sourceCompatibility = JavaVersion.VERSION_11
     targetCompatibility = JavaVersion.VERSION_11
     options.fork = true
-    options.forkOptions.executable = "${PATH_TO_TEST_JAVA_RUNTIME}/bin/javac"
+    def javacName = org.gradle.internal.os.OperatingSystem.current().isWindows() ? 'javac.exe' : 'javac'
+    options.forkOptions.executable = "${PATH_TO_TEST_JAVA_RUNTIME}/bin/${javacName}"
 }
 
 task downloadProtoFiles {
@@ -93,7 +94,9 @@ protobuf {
     }
     generateProtoTasks {
         all()*.plugins { grpc {} }
-        all()*.dependsOn downloadProtoFiles
+        if (project.gradle.startParameter.taskNames.any { it.contains('downloadProtoFiles') }) {
+            all()*.dependsOn downloadProtoFiles
+        }
     }
 }
 
@@ -110,7 +113,8 @@ sourceSets {
 }
 
 tasks.withType(Test) {
-    executable = new File("${PATH_TO_TEST_JAVA_RUNTIME}", 'bin/java')
+    def javaName = org.gradle.internal.os.OperatingSystem.current().isWindows() ? 'java.exe' : 'java'
+    executable = new File("${PATH_TO_TEST_JAVA_RUNTIME}", "bin/${javaName}")
 }
 
 test {

client/src/main/java/com/microsoft/durabletask/DurableTaskGrpcWorker.java

@@ -39,6 +39,7 @@ public final class DurableTaskGrpcWorker implements AutoCloseable {
     private final DataConverter dataConverter;
     private final Duration maximumTimerInterval;
     private final DurableTaskGrpcWorkerVersioningOptions versioningOptions;
+    private final ExceptionPropertiesProvider exceptionPropertiesProvider;
 
     private final TaskHubSidecarServiceBlockingStub sidecarClient;
 
@@ -70,6 +71,7 @@ public final class DurableTaskGrpcWorker implements AutoCloseable {
         this.dataConverter = builder.dataConverter != null ? builder.dataConverter : new JacksonDataConverter();
         this.maximumTimerInterval = builder.maximumTimerInterval != null ? builder.maximumTimerInterval : DEFAULT_MAXIMUM_TIMER_INTERVAL;
         this.versioningOptions = builder.versioningOptions;
+        this.exceptionPropertiesProvider = builder.exceptionPropertiesProvider;
     }
 
     /**
@@ -123,7 +125,8 @@ public void startAndBlock() {
                 this.dataConverter,
                 this.maximumTimerInterval,
                 logger,
-                this.versioningOptions);
+                this.versioningOptions,
+                this.exceptionPropertiesProvider);
         TaskActivityExecutor taskActivityExecutor = new TaskActivityExecutor(
                 this.activityFactories,
                 this.dataConverter,
@@ -351,11 +354,9 @@ public void startAndBlock() {
                                 activityRequest.getTaskId());
                         } catch (Throwable e) {
                             activityError = e;
-                            failureDetails = TaskFailureDetails.newBuilder()
-                                .setErrorType(e.getClass().getName())
-                                .setErrorMessage(e.getMessage())
-                                .setStackTrace(StringValue.of(FailureDetails.getFullStackTrace(e)))
-                                .build();
+                            Exception ex = e instanceof Exception ? (Exception) e : new RuntimeException(e);
+                            failureDetails = FailureDetails.fromException(
+                                    ex, this.exceptionPropertiesProvider).toProto();
                         } finally {
                             activityScope.close();
                             TracingHelper.endSpan(activitySpan, activityError);

client/src/main/java/com/microsoft/durabletask/DurableTaskGrpcWorkerBuilder.java

@@ -18,6 +18,7 @@ public final class DurableTaskGrpcWorkerBuilder {
     DataConverter dataConverter;
     Duration maximumTimerInterval;
     DurableTaskGrpcWorkerVersioningOptions versioningOptions;
+    ExceptionPropertiesProvider exceptionPropertiesProvider;
 
     /**
      * Adds an orchestration factory to be used by the constructed {@link DurableTaskGrpcWorker}.
@@ -125,6 +126,21 @@ public DurableTaskGrpcWorkerBuilder useVersioning(DurableTaskGrpcWorkerVersionin
         return this;
     }
 
+    /**
+     * Sets the {@link ExceptionPropertiesProvider} to use for extracting custom properties from exceptions.
+     * <p>
+     * When set, the provider is invoked whenever an activity or orchestration fails with an exception. The returned
+     * properties are included in the {@link FailureDetails} and can be retrieved via
+     * {@link FailureDetails#getProperties()}.
+     *
+     * @param provider the exception properties provider
+     * @return this builder object
+     */
+    public DurableTaskGrpcWorkerBuilder exceptionPropertiesProvider(ExceptionPropertiesProvider provider) {
+        this.exceptionPropertiesProvider = provider;
+        return this;
+    }
+
     /**
      * Initializes a new {@link DurableTaskGrpcWorker} object with the settings specified in the current builder object.
      * @return a new {@link DurableTaskGrpcWorker} object

client/src/main/java/com/microsoft/durabletask/ExceptionPropertiesProvider.java

@@ -0,0 +1,45 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+package com.microsoft.durabletask;
+
+import javax.annotation.Nullable;
+import java.util.Map;
+
+/**
+ * Provider interface for extracting custom properties from exceptions.
+ * <p>
+ * Implementations of this interface can be registered with a {@link DurableTaskGrpcWorkerBuilder} to include
+ * custom exception properties in {@link FailureDetails} when activities or orchestrations fail.
+ * These properties are then available via {@link FailureDetails#getProperties()}.
+ * <p>
+ * Example usage:
+ * <pre>{@code
+ * DurableTaskGrpcWorker worker = new DurableTaskGrpcWorkerBuilder()
+ *     .exceptionPropertiesProvider(exception -> {
+ *         if (exception instanceof MyCustomException) {
+ *             MyCustomException custom = (MyCustomException) exception;
+ *             Map<String, Object> props = new HashMap<>();
+ *             props.put("errorCode", custom.getErrorCode());
+ *             props.put("retryable", custom.isRetryable());
+ *             return props;
+ *         }
+ *         return null;
+ *     })
+ *     .addOrchestration(...)
+ *     .build();
+ * }</pre>
+ */
+@FunctionalInterface
+public interface ExceptionPropertiesProvider {
+
+    /**
+     * Extracts custom properties from the given exception.
+     * <p>
+     * Return {@code null} or an empty map if no custom properties should be included for this exception.
+     *
+     * @param exception the exception to extract properties from
+     * @return a map of property names to values, or {@code null}
+     */
+    @Nullable
+    Map<String, Object> getExceptionProperties(Exception exception);
+}