Fix setRetryOptions merging initialInterval into congestionInitialInterval

temporal-serviceclient/src/main/java/io/temporal/serviceclient/RpcRetryOptions.java

@@ -272,7 +272,8 @@ public Builder setRetryOptions(RpcRetryOptions o) {
       setInitialInterval(
           OptionsUtils.merge(initialInterval, o.getInitialInterval(), Duration.class));
       setCongestionInitialInterval(
-          OptionsUtils.merge(congestionInitialInterval, o.getInitialInterval(), Duration.class));
+          OptionsUtils.merge(
+              congestionInitialInterval, o.getCongestionInitialInterval(), Duration.class));
       setExpiration(OptionsUtils.merge(expiration, o.getExpiration(), Duration.class));
       setMaximumInterval(
           OptionsUtils.merge(maximumInterval, o.getMaximumInterval(), Duration.class));

temporal-serviceclient/src/test/java/io/temporal/serviceclient/RpcRetryOptionsTest.java

@@ -0,0 +1,30 @@
+package io.temporal.serviceclient;
+
+import static org.junit.Assert.assertEquals;
+
+import java.time.Duration;
+import org.junit.Test;
+
+public class RpcRetryOptionsTest {
+
+  /**
+   * congestionInitialInterval is the backoff used for RESOURCE_EXHAUSTED and is deliberately set
+   * much higher than initialInterval. Builder.setRetryOptions must merge it from the source's
+   * congestionInitialInterval, not from its initialInterval, otherwise that margin is silently
+   * collapsed.
+   */
+  @Test
+  public void setRetryOptionsMergesCongestionInitialInterval() {
+    RpcRetryOptions source =
+        RpcRetryOptions.newBuilder()
+            .setInitialInterval(Duration.ofMillis(200))
+            .setCongestionInitialInterval(Duration.ofSeconds(7))
+            .validateBuildWithDefaults();
+
+    RpcRetryOptions merged =
+        RpcRetryOptions.newBuilder().setRetryOptions(source).validateBuildWithDefaults();
+
+    assertEquals(Duration.ofMillis(200), merged.getInitialInterval());
+    assertEquals(Duration.ofSeconds(7), merged.getCongestionInitialInterval());
+  }
+}