diff --git a/tools/ota_analysis/src/components/PayloadComposition.vue b/tools/ota_analysis/src/components/PayloadComposition.vue
index 5557c734c..376ff9b6a 100644
--- a/tools/ota_analysis/src/components/PayloadComposition.vue
+++ b/tools/ota_analysis/src/components/PayloadComposition.vue
@@ -35,6 +35,7 @@
     <v-col
       cols="12"
       md="6"
+      class="tooltip"
     >
       <v-btn
         :disabled="manifest.nonAB"
@@ -43,6 +44,12 @@
       >
         Analyse COW Merge Operations
       </v-btn>
+      <span
+        v-if="manifest.nonAB"
+        class="tooltiptext"
+      >
+        This function is only supported in A/B OTA
+      </span>
     </v-col>
     <v-col
       cols="12"
@@ -155,4 +162,24 @@ export default {
 .list-data {
   text-align: center;
 }
+.tooltip {
+  position: relative;
+  display: inline-block;
+}
+
+.tooltip .tooltiptext {
+  visibility: hidden;
+  width: 120px;
+  background-color: black;
+  color: #fff;
+  text-align: center;
+  border-radius: 6px;
+  padding: 5px 0;
+  position: absolute;
+  z-index: 1;
+}
+
+.tooltip:hover .tooltiptext {
+  visibility: visible;
+}
 </style>
\ No newline at end of file
diff --git a/tools/ota_analysis/src/services/map_parser.js b/tools/ota_analysis/src/services/map_parser.js
index 37b1d1822..6bc16d0d0 100644
--- a/tools/ota_analysis/src/services/map_parser.js
+++ b/tools/ota_analysis/src/services/map_parser.js
@@ -115,5 +115,8 @@ function InsertMap(map, name, left, right) {
 function queryMap(map, left, right) {
   // Assuming the consecutive blocks belong to the same file
   // Only the start block is queried here.
+  if (!map[left]) {
+    return 'unknown'
+  }
   return map[left]
 }
\ No newline at end of file
diff --git a/tools/ota_analysis/src/services/payload_nonab.js b/tools/ota_analysis/src/services/payload_nonab.js
index 5f43401a1..dd0769a7b 100644
--- a/tools/ota_analysis/src/services/payload_nonab.js
+++ b/tools/ota_analysis/src/services/payload_nonab.js
@@ -53,15 +53,20 @@ export class PayloadNonAB extends chromeos_update_engine.DeltaArchiveManifest{
     * zero [rangeset] : fill zeros
     * new [rangeset] : fill with new data from <partitionName.new.data>
     * erase [rangeset] : mark given blocks as empty
-    * move <...>
-    * bsdiff <patchstart> <patchlen> <...>
-    * imgdiff <patchstart> <patchlen> <...> :
+    * move <src_hash> <...>
+    * bsdiff <patchstart> <patchlen> <src_hash> <tgt_hash> <...>
+    * imgdiff <patchstart> <patchlen> <src_hash> <tgt_hash> <...> :
     * Read the source blocks and apply (not for move op) to the target blocks
     * stash <stash_id> <src_range> : load the given source range to memory
     * free <stash_id> : free the given <stash_id>
     * format:
     * [rangeset]: <# of pairs>, <pair A start>, <pair A end>, ...
     * <stash_id>: a hex number with length of 40
+    * <...>: We expect to parse the remainder of the parameter tokens as one of:
+    *   <tgt_range> <src_block_count> <src_range> (loads data from source image only)
+    *   <tgt_range> <src_block_count> - <[stash_id:stash_range] ...> (loads data from stashes only)
+    *   <tgt_range> <src_block_count> <src_range> <src_loc> <[stash_id:stash_range] ...>
+    *   (loads data from both source image and stashes)
     */
     partition.operations = new Array()
     let newDataSize = await this.sizeNewData(partition.partitionName)
@@ -87,14 +92,17 @@ export class PayloadNonAB extends chromeos_update_engine.DeltaArchiveManifest{
         op.dstExtents = elements.slice(1).reduce(parseRange, [])
         break
       case 'move':
+        op.dstExtents = parseRange([], elements[2])
         break
       case 'bsdiff':
         op.dataOffset = parseInt(elements[1])
         op.dataLength = parseInt(elements[2])
+        op.dstExtents = parseRange([], elements[5])
         break
       case 'imgdiff':
         op.dataOffset = parseInt(elements[1])
         op.dataLength = parseInt(elements[2])
+        op.dstExtents = parseRange([], elements[5])
         break
       case 'stash':
         break