diff --git a/nodes/pip/main.cpp b/nodes/pip/main.cpp
index abb50c3..17877d8 100644
--- a/nodes/pip/main.cpp
+++ b/nodes/pip/main.cpp
@@ -106,7 +106,7 @@ class PiPNode : public dmf::NodeBase {
         std::vector<uint16_t> Cb0(inset_w / 2), Cb1(inset_w / 2);
         std::vector<uint16_t> Cr0(inset_w / 2), Cr1(inset_w / 2);
 
-        // --- Sync group: ensures both inputs have grain N before compositing ---
+        // --- Sync group: blocks until both inputs have grain N ---
         mxlFlowSynchronizationGroup sync_group{};
         mxlCreateFlowSynchronizationGroup(instance(), &sync_group);
         mxlFlowSynchronizationGroupAddReader(sync_group, bg_reader);
@@ -120,8 +120,10 @@ class PiPNode : public dmf::NodeBase {
         uint64_t frame_count = 0, timeout_count = 0;
 
         while (dmf::g_running.load(std::memory_order_relaxed)) {
-            mxlStatus st = mxlFlowSynchronizationGroupWaitForDataAt(
-                sync_group, index, 200'000'000);
+            // WaitForDataAt expects TAI nanoseconds, not a grain index.
+            const uint64_t tai_ns = mxlIndexToTimestamp(&rate, index);
+            const mxlStatus st = mxlFlowSynchronizationGroupWaitForDataAt(
+                sync_group, tai_ns, 200'000'000);
 
             if (st == MXL_STATUS_OK) {
                 mxlGrainInfo bg_grain{}, inset_grain{};
@@ -134,25 +136,20 @@ class PiPNode : public dmf::NodeBase {
                 mxlGrainInfo out_grain{};
                 uint8_t*     out_buf = nullptr;
                 if (mxlFlowWriterOpenGrain(out_writer, index, &out_grain, &out_buf) == MXL_STATUS_OK) {
-                    // Copy full background into output
                     std::memcpy(out_buf, bg_buf,
                                 static_cast<size_t>(bg_stride) * static_cast<size_t>(bg_h));
 
-                    // Scale inset and composite over background
-                    if (inset_buf) {
-                        dmf::v210::scale_and_overlay(
-                            inset_buf, inset_stride, inset_w, inset_h,
-                            out_buf,   out_stride,
-                            pip_x, pip_y, clamped_w, clamped_h,
-                            Y0, Y1, Cb0, Cb1, Cr0, Cr1);
-                    }
+                    dmf::v210::scale_and_overlay(
+                        inset_buf, inset_stride, inset_w, inset_h,
+                        out_buf,   out_stride,
+                        pip_x, pip_y, clamped_w, clamped_h,
+                        Y0, Y1, Cb0, Cb1, Cr0, Cr1);
 
                     out_grain.flags = (bg_grain.flags | inset_grain.flags) & MXL_GRAIN_FLAG_INVALID;
                     out_grain.validSlices = out_grain.totalSlices;
                     mxlFlowWriterCommitGrain(out_writer, &out_grain);
                     frame_count++;
                 }
-
                 index++;
 
             } else if (st == MXL_ERR_TIMEOUT) {