diff --git a/cameleer3-server-app/src/main/java/com/cameleer3/server/app/config/StorageBeanConfig.java b/cameleer3-server-app/src/main/java/com/cameleer3/server/app/config/StorageBeanConfig.java
index 001f666e..06def6ba 100644
--- a/cameleer3-server-app/src/main/java/com/cameleer3/server/app/config/StorageBeanConfig.java
+++ b/cameleer3-server-app/src/main/java/com/cameleer3/server/app/config/StorageBeanConfig.java
@@ -110,8 +110,8 @@ public class StorageBeanConfig {
             WriteBuffer<ChunkAccumulator.ProcessorBatch> processorBatchBuffer,
             DiagramStore diagramStore) {
         return new ChunkAccumulator(
-                executionBuffer::offer,
-                processorBatchBuffer::offer,
+                executionBuffer::offerOrWarn,
+                processorBatchBuffer::offerOrWarn,
                 diagramStore,
                 java.time.Duration.ofMinutes(5));
     }
diff --git a/cameleer3-server-app/src/main/java/com/cameleer3/server/app/diagram/ElkDiagramRenderer.java b/cameleer3-server-app/src/main/java/com/cameleer3/server/app/diagram/ElkDiagramRenderer.java
index e357711f..6c846f97 100644
--- a/cameleer3-server-app/src/main/java/com/cameleer3/server/app/diagram/ElkDiagramRenderer.java
+++ b/cameleer3-server-app/src/main/java/com/cameleer3/server/app/diagram/ElkDiagramRenderer.java
@@ -884,6 +884,7 @@ public class ElkDiagramRenderer implements DiagramRenderer {
     }
 
     private ElkNode getElkRoot(ElkNode node) {
+        if (node == null) return null;
         ElkNode current = node;
         while (current.getParent() != null) {
             current = current.getParent();
diff --git a/cameleer3-server-core/src/main/java/com/cameleer3/server/core/ingestion/WriteBuffer.java b/cameleer3-server-core/src/main/java/com/cameleer3/server/core/ingestion/WriteBuffer.java
index 46a7be35..29450a72 100644
--- a/cameleer3-server-core/src/main/java/com/cameleer3/server/core/ingestion/WriteBuffer.java
+++ b/cameleer3-server-core/src/main/java/com/cameleer3/server/core/ingestion/WriteBuffer.java
@@ -38,6 +38,16 @@ public class WriteBuffer<T> {
         return queue.offer(item);
     }
 
+    /**
+     * Offer an item, logging a warning if the buffer is full.
+     * Use this as a {@code Consumer<T>} when the caller cannot handle backpressure.
+     */
+    public void offerOrWarn(T item) {
+        if (!queue.offer(item)) {
+            log.warn("WriteBuffer full (capacity={}), item dropped", capacity);
+        }
+    }
+
     /**
      * Offer a batch of items with all-or-nothing semantics.
      * If the buffer does not have enough remaining capacity for the entire batch,