diff --git a/.github/trigger_files/IO_Iceberg_Integration_Tests_Dataflow.json b/.github/trigger_files/IO_Iceberg_Integration_Tests_Dataflow.json
index 5abe02fc09c7..0ca37f8c8e27 100644
--- a/.github/trigger_files/IO_Iceberg_Integration_Tests_Dataflow.json
+++ b/.github/trigger_files/IO_Iceberg_Integration_Tests_Dataflow.json
@@ -1,4 +1,5 @@
 {
   "comment": "Modify this file in a trivial way to cause this test suite to run.",
-  "modification": 1
+  "modification": 1,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/IO_Iceberg_Managed_Integration_Tests_Dataflow.json b/.github/trigger_files/IO_Iceberg_Managed_Integration_Tests_Dataflow.json
index 3a009261f4f9..9a4fbff0c0b7 100644
--- a/.github/trigger_files/IO_Iceberg_Managed_Integration_Tests_Dataflow.json
+++ b/.github/trigger_files/IO_Iceberg_Managed_Integration_Tests_Dataflow.json
@@ -1,4 +1,5 @@
 {
   "comment": "Modify this file in a trivial way to cause this test suite to run.",
-  "modification": 2
+  "modification": 2,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_Java_DataflowV2.json b/.github/trigger_files/beam_PostCommit_Java_DataflowV2.json
index c4a6954cecb7..07a9e088c21e 100644
--- a/.github/trigger_files/beam_PostCommit_Java_DataflowV2.json
+++ b/.github/trigger_files/beam_PostCommit_Java_DataflowV2.json
@@ -1,4 +1,5 @@
 {
   "modification": 9,
-  "https://github.com/apache/beam/pull/35159": "moving WindowedValue and making an interface"
+  "https://github.com/apache/beam/pull/35159": "moving WindowedValue and making an interface",
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_Java_Delta_IO_Dataflow.json b/.github/trigger_files/beam_PostCommit_Java_Delta_IO_Dataflow.json
index ab4daeae2349..44932dfca507 100644
--- a/.github/trigger_files/beam_PostCommit_Java_Delta_IO_Dataflow.json
+++ b/.github/trigger_files/beam_PostCommit_Java_Delta_IO_Dataflow.json
@@ -1,4 +1,5 @@
 {
   "comment": "Modify this file in a trivial way to cause this test suite to run.",
-  "modification": 3
+  "modification": 3,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_Java_Examples_Dataflow_ARM.json b/.github/trigger_files/beam_PostCommit_Java_Examples_Dataflow_ARM.json
index 0967ef424bce..05a452081cf3 100644
--- a/.github/trigger_files/beam_PostCommit_Java_Examples_Dataflow_ARM.json
+++ b/.github/trigger_files/beam_PostCommit_Java_Examples_Dataflow_ARM.json
@@ -1 +1,3 @@
-{}
+{
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
+}
diff --git a/.github/trigger_files/beam_PostCommit_Java_Examples_Dataflow_V2.json b/.github/trigger_files/beam_PostCommit_Java_Examples_Dataflow_V2.json
index ffdd1b908f46..2bbe49ea6083 100644
--- a/.github/trigger_files/beam_PostCommit_Java_Examples_Dataflow_V2.json
+++ b/.github/trigger_files/beam_PostCommit_Java_Examples_Dataflow_V2.json
@@ -2,5 +2,6 @@
   "https://github.com/apache/beam/pull/36138": "Cleanly separating v1 worker and v2 sdk harness container image handling",
   "https://github.com/apache/beam/pull/34902": "Introducing OutputBuilder",
   "comment": "Modify this file in a trivial way to cause this test suite to run",
-  "modification": 2
+  "modification": 2,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_Java_Examples_Dataflow_V2_Java.json b/.github/trigger_files/beam_PostCommit_Java_Examples_Dataflow_V2_Java.json
new file mode 100644
index 000000000000..04197c72efed
--- /dev/null
+++ b/.github/trigger_files/beam_PostCommit_Java_Examples_Dataflow_V2_Java.json
@@ -0,0 +1,4 @@
+{
+  "comment": "Modify this file in a trivial way to cause this test suite to run.",
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
+}
diff --git a/.github/trigger_files/beam_PostCommit_Java_IO_Performance_Tests.json b/.github/trigger_files/beam_PostCommit_Java_IO_Performance_Tests.json
index b26833333238..1b1ef86e9175 100644
--- a/.github/trigger_files/beam_PostCommit_Java_IO_Performance_Tests.json
+++ b/.github/trigger_files/beam_PostCommit_Java_IO_Performance_Tests.json
@@ -1,4 +1,5 @@
 {
   "comment": "Modify this file in a trivial way to cause this test suite to run",
-  "modification": 2
+  "modification": 2,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_Java_Nexmark_Dataflow_V2.json b/.github/trigger_files/beam_PostCommit_Java_Nexmark_Dataflow_V2.json
new file mode 100644
index 000000000000..04197c72efed
--- /dev/null
+++ b/.github/trigger_files/beam_PostCommit_Java_Nexmark_Dataflow_V2.json
@@ -0,0 +1,4 @@
+{
+  "comment": "Modify this file in a trivial way to cause this test suite to run.",
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
+}
diff --git a/.github/trigger_files/beam_PostCommit_Java_Nexmark_Dataflow_V2_Java.json b/.github/trigger_files/beam_PostCommit_Java_Nexmark_Dataflow_V2_Java.json
new file mode 100644
index 000000000000..04197c72efed
--- /dev/null
+++ b/.github/trigger_files/beam_PostCommit_Java_Nexmark_Dataflow_V2_Java.json
@@ -0,0 +1,4 @@
+{
+  "comment": "Modify this file in a trivial way to cause this test suite to run.",
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
+}
diff --git a/.github/trigger_files/beam_PostCommit_Java_PVR_Flink_Batch.json b/.github/trigger_files/beam_PostCommit_Java_PVR_Flink_Batch.json
index 1d083be7e29a..6f486a1f8c14 100644
--- a/.github/trigger_files/beam_PostCommit_Java_PVR_Flink_Batch.json
+++ b/.github/trigger_files/beam_PostCommit_Java_PVR_Flink_Batch.json
@@ -1,5 +1,6 @@
 {
   "comment": "Modify this file in a trivial way to cause this test suite to run",
-  "https://github.com/apache/beam/pull/32440": "test new datastream runner for batch"
-  "modification": 2
+  "https://github.com/apache/beam/pull/32440": "test new datastream runner for batch",
+  "modification": 2,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_Java_PVR_Flink_Streaming.json b/.github/trigger_files/beam_PostCommit_Java_PVR_Flink_Streaming.json
index d7f4c03aaf5b..626e4fea5c8b 100644
--- a/.github/trigger_files/beam_PostCommit_Java_PVR_Flink_Streaming.json
+++ b/.github/trigger_files/beam_PostCommit_Java_PVR_Flink_Streaming.json
@@ -1,5 +1,6 @@
 {
   "comment": "Modify this file in a trivial way to cause this test suite to run",
   "modification": 2,
-  "https://github.com/apache/beam/pull/32440": "test new datastream runner for batch"
+  "https://github.com/apache/beam/pull/32440": "test new datastream runner for batch",
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_Java_PVR_Spark3_Streaming.json b/.github/trigger_files/beam_PostCommit_Java_PVR_Spark3_Streaming.json
index 38ae1cf68222..c1bb7d6c3798 100644
--- a/.github/trigger_files/beam_PostCommit_Java_PVR_Spark3_Streaming.json
+++ b/.github/trigger_files/beam_PostCommit_Java_PVR_Spark3_Streaming.json
@@ -1,4 +1,5 @@
 {
   "comment": "Modify this file in a trivial way to cause this test suite to run",
-  "modification": 8
+  "modification": 8,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_Java_PVR_Spark4_Batch.json b/.github/trigger_files/beam_PostCommit_Java_PVR_Spark4_Batch.json
new file mode 100644
index 000000000000..04197c72efed
--- /dev/null
+++ b/.github/trigger_files/beam_PostCommit_Java_PVR_Spark4_Batch.json
@@ -0,0 +1,4 @@
+{
+  "comment": "Modify this file in a trivial way to cause this test suite to run.",
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
+}
diff --git a/.github/trigger_files/beam_PostCommit_Java_PVR_Spark4_Streaming.json b/.github/trigger_files/beam_PostCommit_Java_PVR_Spark4_Streaming.json
new file mode 100644
index 000000000000..04197c72efed
--- /dev/null
+++ b/.github/trigger_files/beam_PostCommit_Java_PVR_Spark4_Streaming.json
@@ -0,0 +1,4 @@
+{
+  "comment": "Modify this file in a trivial way to cause this test suite to run.",
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
+}
diff --git a/.github/trigger_files/beam_PostCommit_Java_PVR_Spark_Batch.json b/.github/trigger_files/beam_PostCommit_Java_PVR_Spark_Batch.json
index d6a91b7e2e86..975b99265d4e 100644
--- a/.github/trigger_files/beam_PostCommit_Java_PVR_Spark_Batch.json
+++ b/.github/trigger_files/beam_PostCommit_Java_PVR_Spark_Batch.json
@@ -1,4 +1,5 @@
 {
   "comment": "Modify this file in a trivial way to cause this test suite to run",
-  "modification": 7
+  "modification": 7,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_Java_ValidatesRunner_Dataflow_V2.json b/.github/trigger_files/beam_PostCommit_Java_ValidatesRunner_Dataflow_V2.json
index 22f6c3813b60..04ea96054d2a 100644
--- a/.github/trigger_files/beam_PostCommit_Java_ValidatesRunner_Dataflow_V2.json
+++ b/.github/trigger_files/beam_PostCommit_Java_ValidatesRunner_Dataflow_V2.json
@@ -1,4 +1,5 @@
 {
   "comment": "Modify this file in a trivial way to cause this test suite to run!",
-  "modification": 5
+  "modification": 5,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_Java_ValidatesRunner_Dataflow_V2_Streaming.json b/.github/trigger_files/beam_PostCommit_Java_ValidatesRunner_Dataflow_V2_Streaming.json
index ca6b5440de4f..38c53ff4a6f9 100644
--- a/.github/trigger_files/beam_PostCommit_Java_ValidatesRunner_Dataflow_V2_Streaming.json
+++ b/.github/trigger_files/beam_PostCommit_Java_ValidatesRunner_Dataflow_V2_Streaming.json
@@ -1,4 +1,5 @@
 {
   "comment": "Modify this file in a trivial way to cause this test suite to run!",
   "modification": 1,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_Java_ValidatesRunner_ULR.json b/.github/trigger_files/beam_PostCommit_Java_ValidatesRunner_ULR.json
index 6e2f429dd24e..3af8cfd244ae 100644
--- a/.github/trigger_files/beam_PostCommit_Java_ValidatesRunner_ULR.json
+++ b/.github/trigger_files/beam_PostCommit_Java_ValidatesRunner_ULR.json
@@ -2,5 +2,6 @@
   "https://github.com/apache/beam/pull/34902": "Introducing OutputBuilder",
   "comment": "Modify this file in a trivial way to cause this test suite to run",
   "https://github.com/apache/beam/pull/31156": "noting that PR #31156 should run this test",
-  "https://github.com/apache/beam/pull/35159": "moving WindowedValue and making an interface"
+  "https://github.com/apache/beam/pull/35159": "moving WindowedValue and making an interface",
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_Python_Xlang_Gcp_Dataflow.json b/.github/trigger_files/beam_PostCommit_Python_Xlang_Gcp_Dataflow.json
index 83346d34aee0..dd4c6d12bfc2 100644
--- a/.github/trigger_files/beam_PostCommit_Python_Xlang_Gcp_Dataflow.json
+++ b/.github/trigger_files/beam_PostCommit_Python_Xlang_Gcp_Dataflow.json
@@ -1,4 +1,5 @@
 {
   "comment": "Modify this file in a trivial way to cause this test suite to run",
-  "modification": 16
+  "modification": 16,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_Python_Xlang_Gcp_Direct.json b/.github/trigger_files/beam_PostCommit_Python_Xlang_Gcp_Direct.json
index b26833333238..1b1ef86e9175 100644
--- a/.github/trigger_files/beam_PostCommit_Python_Xlang_Gcp_Direct.json
+++ b/.github/trigger_files/beam_PostCommit_Python_Xlang_Gcp_Direct.json
@@ -1,4 +1,5 @@
 {
   "comment": "Modify this file in a trivial way to cause this test suite to run",
-  "modification": 2
+  "modification": 2,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_Python_Xlang_IO_Dataflow.json b/.github/trigger_files/beam_PostCommit_Python_Xlang_IO_Dataflow.json
index c537844dc84a..4f9719d7185b 100644
--- a/.github/trigger_files/beam_PostCommit_Python_Xlang_IO_Dataflow.json
+++ b/.github/trigger_files/beam_PostCommit_Python_Xlang_IO_Dataflow.json
@@ -1,4 +1,5 @@
 {
   "comment": "Modify this file in a trivial way to cause this test suite to run",
-  "modification": 3
+  "modification": 3,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_Python_Xlang_IO_Direct.json b/.github/trigger_files/beam_PostCommit_Python_Xlang_IO_Direct.json
index b26833333238..1b1ef86e9175 100644
--- a/.github/trigger_files/beam_PostCommit_Python_Xlang_IO_Direct.json
+++ b/.github/trigger_files/beam_PostCommit_Python_Xlang_IO_Direct.json
@@ -1,4 +1,5 @@
 {
   "comment": "Modify this file in a trivial way to cause this test suite to run",
-  "modification": 2
+  "modification": 2,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_Python_Xlang_Messaging_Direct.json b/.github/trigger_files/beam_PostCommit_Python_Xlang_Messaging_Direct.json
index 38ae1cf68222..c1bb7d6c3798 100644
--- a/.github/trigger_files/beam_PostCommit_Python_Xlang_Messaging_Direct.json
+++ b/.github/trigger_files/beam_PostCommit_Python_Xlang_Messaging_Direct.json
@@ -1,4 +1,5 @@
 {
   "comment": "Modify this file in a trivial way to cause this test suite to run",
-  "modification": 8
+  "modification": 8,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_TransformService_Direct.json b/.github/trigger_files/beam_PostCommit_TransformService_Direct.json
index 8ed972c9f579..0942404b0ebf 100644
--- a/.github/trigger_files/beam_PostCommit_TransformService_Direct.json
+++ b/.github/trigger_files/beam_PostCommit_TransformService_Direct.json
@@ -1,4 +1,5 @@
 {
   "comment": "Modify this file in a trivial way to cause this test suite to run",
-  "revision": 3
+  "revision": 3,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_XVR_Direct.json b/.github/trigger_files/beam_PostCommit_XVR_Direct.json
index 702328d16d4b..3b864120bf95 100644
--- a/.github/trigger_files/beam_PostCommit_XVR_Direct.json
+++ b/.github/trigger_files/beam_PostCommit_XVR_Direct.json
@@ -1,3 +1,4 @@
 {
-  "modification": 1
+  "modification": 1,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_XVR_Flink.json b/.github/trigger_files/beam_PostCommit_XVR_Flink.json
index 7dcd6398db10..a60830fe7d2a 100644
--- a/.github/trigger_files/beam_PostCommit_XVR_Flink.json
+++ b/.github/trigger_files/beam_PostCommit_XVR_Flink.json
@@ -1,4 +1,5 @@
 {
   "modification": 3,
-  "trigger-2026-04-04": "portable_runner expand_sdf opt-in"
+  "trigger-2026-04-04": "portable_runner expand_sdf opt-in",
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_XVR_GoUsingJava_Dataflow.json b/.github/trigger_files/beam_PostCommit_XVR_GoUsingJava_Dataflow.json
index b26833333238..1b1ef86e9175 100644
--- a/.github/trigger_files/beam_PostCommit_XVR_GoUsingJava_Dataflow.json
+++ b/.github/trigger_files/beam_PostCommit_XVR_GoUsingJava_Dataflow.json
@@ -1,4 +1,5 @@
 {
   "comment": "Modify this file in a trivial way to cause this test suite to run",
-  "modification": 2
+  "modification": 2,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_XVR_JavaUsingPython_Dataflow.json b/.github/trigger_files/beam_PostCommit_XVR_JavaUsingPython_Dataflow.json
index 6a55e29ae15d..0ca37f8c8e27 100644
--- a/.github/trigger_files/beam_PostCommit_XVR_JavaUsingPython_Dataflow.json
+++ b/.github/trigger_files/beam_PostCommit_XVR_JavaUsingPython_Dataflow.json
@@ -1,4 +1,5 @@
 {
-    "comment": "Modify this file in a trivial way to cause this test suite to run.",
-    "modification": 1
-}
\ No newline at end of file
+  "comment": "Modify this file in a trivial way to cause this test suite to run.",
+  "modification": 1,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
+}
diff --git a/.github/trigger_files/beam_PostCommit_XVR_PythonUsingJavaSQL_Dataflow.json b/.github/trigger_files/beam_PostCommit_XVR_PythonUsingJavaSQL_Dataflow.json
index ca2897e2eb2b..c04f8e34f87f 100644
--- a/.github/trigger_files/beam_PostCommit_XVR_PythonUsingJavaSQL_Dataflow.json
+++ b/.github/trigger_files/beam_PostCommit_XVR_PythonUsingJavaSQL_Dataflow.json
@@ -1,3 +1,4 @@
 {
-  "modification": 2
-}
\ No newline at end of file
+  "modification": 2,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
+}
diff --git a/.github/trigger_files/beam_PostCommit_XVR_PythonUsingJava_Dataflow.json b/.github/trigger_files/beam_PostCommit_XVR_PythonUsingJava_Dataflow.json
index b73af5e61a43..0ca37f8c8e27 100644
--- a/.github/trigger_files/beam_PostCommit_XVR_PythonUsingJava_Dataflow.json
+++ b/.github/trigger_files/beam_PostCommit_XVR_PythonUsingJava_Dataflow.json
@@ -1,4 +1,5 @@
 {
-    "comment": "Modify this file in a trivial way to cause this test suite to run.",
-    "modification": 1
+  "comment": "Modify this file in a trivial way to cause this test suite to run.",
+  "modification": 1,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_XVR_Spark3.json b/.github/trigger_files/beam_PostCommit_XVR_Spark3.json
index 1be4456862dc..74a5d652c7b9 100644
--- a/.github/trigger_files/beam_PostCommit_XVR_Spark3.json
+++ b/.github/trigger_files/beam_PostCommit_XVR_Spark3.json
@@ -1,3 +1,4 @@
 {
-  "trigger-2026-07-08": "portable_runner expand_sdf opt-in 2"
+  "trigger-2026-07-08": "portable_runner expand_sdf opt-in 2",
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/.github/trigger_files/beam_PostCommit_Yaml_Xlang_Direct.json b/.github/trigger_files/beam_PostCommit_Yaml_Xlang_Direct.json
index 8ed972c9f579..0942404b0ebf 100644
--- a/.github/trigger_files/beam_PostCommit_Yaml_Xlang_Direct.json
+++ b/.github/trigger_files/beam_PostCommit_Yaml_Xlang_Direct.json
@@ -1,4 +1,5 @@
 {
   "comment": "Modify this file in a trivial way to cause this test suite to run",
-  "revision": 3
+  "revision": 3,
+  "https://github.com/apache/beam/pull/39990": "removing dead code from FnApiDoFnRunner"
 }
diff --git a/sdks/java/harness/src/main/java/org/apache/beam/fn/harness/FnApiDoFnRunner.java b/sdks/java/harness/src/main/java/org/apache/beam/fn/harness/FnApiDoFnRunner.java
index b9cfe6ec52dd..a5914a25f799 100644
--- a/sdks/java/harness/src/main/java/org/apache/beam/fn/harness/FnApiDoFnRunner.java
+++ b/sdks/java/harness/src/main/java/org/apache/beam/fn/harness/FnApiDoFnRunner.java
@@ -350,10 +350,6 @@ public final void addRunnerForPTransform(Context context) throws IOException {
         case PTransformTranslation.PAR_DO_TRANSFORM_URN:
           mainOutputTag = (TupleTag) ParDoTranslation.getMainOutputTag(parDoPayload);
           break;
-        case PTransformTranslation.SPLITTABLE_SPLIT_AND_SIZE_RESTRICTIONS_URN:
-          mainOutputTag =
-              new TupleTag(Iterables.getOnlyElement(pTransform.getOutputsMap().keySet()));
-          break;
         default:
           throw new IllegalStateException(
               String.format("Unknown urn: %s", pTransform.getSpec().getUrn()));
@@ -444,17 +440,7 @@ public final void addRunnerForPTransform(Context context) throws IOException {
     this.doFnInvoker = DoFnInvokers.tryInvokeSetupFor(doFn, pipelineOptions);
 
     this.startBundleArgumentProvider = new StartBundleArgumentProvider();
-    // Register the appropriate handlers.
-    switch (pTransform.getSpec().getUrn()) {
-      case PTransformTranslation.PAR_DO_TRANSFORM_URN:
-      case PTransformTranslation.SPLITTABLE_PROCESS_SIZED_ELEMENTS_AND_RESTRICTIONS_URN:
-        addStartFunction.accept(this::startBundle);
-        break;
-      case PTransformTranslation.SPLITTABLE_SPLIT_AND_SIZE_RESTRICTIONS_URN:
-        // startBundle should not be invoked
-      default:
-        // no-op
-    }
+    addStartFunction.accept(this::startBundle);
 
     String mainInput;
     try {
@@ -474,32 +460,16 @@ public final void addRunnerForPTransform(Context context) throws IOException {
         }
         break;
       case PTransformTranslation.SPLITTABLE_PROCESS_SIZED_ELEMENTS_AND_RESTRICTIONS_URN:
-        if (doFnSignature.processElement().observesWindow()
-            || (doFnSignature.newTracker() != null && doFnSignature.newTracker().observesWindow())
-            || (doFnSignature.getSize() != null && doFnSignature.getSize().observesWindow())
-            || (doFnSignature.newWatermarkEstimator() != null
-                && doFnSignature.newWatermarkEstimator().observesWindow())
-            || !sideInputMapping.isEmpty()) {
-          mainInputConsumer =
-              new SplittableFnDataReceiver() {
-                @Override
-                public void accept(WindowedValue input) throws Exception {
-                  processElementForWindowObservingSizedElementAndRestriction(input);
-                }
-              };
-          this.processContext = new WindowObservingProcessBundleContext();
-        } else {
-          mainInputConsumer =
-              new SplittableFnDataReceiver() {
-                @Override
-                public void accept(WindowedValue input) throws Exception {
-                  // TODO(BEAM-10303): Create a variant which is optimized to not observe the
-                  // windows.
-                  processElementForWindowObservingSizedElementAndRestriction(input);
-                }
-              };
-          this.processContext = new WindowObservingProcessBundleContext();
-        }
+        // TODO(BEAM-10303): Create a variant which is optimized to not observe the windows when
+        // neither the DoFn nor its side inputs observe them.
+        mainInputConsumer =
+            new SplittableFnDataReceiver() {
+              @Override
+              public void accept(WindowedValue input) throws Exception {
+                processElementForWindowObservingSizedElementAndRestriction(input);
+              }
+            };
+        this.processContext = new WindowObservingProcessBundleContext();
         break;
       default:
         throw new IllegalStateException("Unknown urn: " + pTransform.getSpec().getUrn());
@@ -507,16 +477,7 @@ public void accept(WindowedValue input) throws Exception {
     addPCollectionConsumer.accept(pTransform.getInputsOrThrow(mainInput), mainInputConsumer);
 
     this.finishBundleArgumentProvider = new FinishBundleArgumentProvider();
-    switch (pTransform.getSpec().getUrn()) {
-      case PTransformTranslation.PAR_DO_TRANSFORM_URN:
-      case PTransformTranslation.SPLITTABLE_PROCESS_SIZED_ELEMENTS_AND_RESTRICTIONS_URN:
-        addFinishFunction.accept(this::finishBundle);
-        break;
-      case PTransformTranslation.SPLITTABLE_SPLIT_AND_SIZE_RESTRICTIONS_URN:
-        // finishBundle should not be invoked
-      default:
-        // no-op
-    }
+    addFinishFunction.accept(this::finishBundle);
     addTearDownFunction.accept(this::tearDown);
 
     workCompletedShortId =