diff --git a/hadoop-ozone/dist/src/main/compose/ozone/docker-config b/hadoop-ozone/dist/src/main/compose/ozone/docker-config
index ecca3a971c61..ef8430bfaec6 100644
--- a/hadoop-ozone/dist/src/main/compose/ozone/docker-config
+++ b/hadoop-ozone/dist/src/main/compose/ozone/docker-config
@@ -67,3 +67,6 @@ no_proxy=om,scm,s3g,recon,kdc,localhost,127.0.0.1
 
 # Explicitly enable filesystem snapshot feature for this Docker compose cluster
 OZONE-SITE.XML_ozone.filesystem.snapshot.enabled=true
+
+# Periodic snapshot defrag for smoketest snapshot/snapshot-defrag.robot (HDDS-15181)
+OZONE-SITE.XML_ozone.snapshot.defrag.service.interval=30s
diff --git a/hadoop-ozone/dist/src/main/smoketest/snapshot/snapshot-defrag.robot b/hadoop-ozone/dist/src/main/smoketest/snapshot/snapshot-defrag.robot
new file mode 100644
index 000000000000..a8b02e5cc3a9
--- /dev/null
+++ b/hadoop-ozone/dist/src/main/smoketest/snapshot/snapshot-defrag.robot
@@ -0,0 +1,124 @@
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+*** Settings ***
+Documentation       Basic checks that snapshots still look correct while the OM runs periodic
+...                 snapshot defrag in the background (Jira HDDS-15181 / parent HDDS-13003).
+...                 Cluster setup: filesystem snapshots on; defrag interval in compose/ozone
+...                 docker-config. Default compose has one datanode: use replication 1 (OZONE_REPLICATION_FACTOR)
+...                 or scale datanodes to match replication.
+Library             OperatingSystem
+Resource            ../ozone-lib/shell.robot
+Resource            snapshot-setup.robot
+Suite Setup         Prepare Suite With Bucket And First Snapshot
+Test Timeout        20 minutes
+
+*** Variables ***
+# Wait long enough for at least two defrag runs (OM uses a 30s interval in compose).
+${DEFRAG_WAIT_SECONDS}     65
+
+*** Test Cases ***
+Read Snapshot Data Right After Create
+    [Documentation]     You can read the snapshotted key from the .snapshot path as soon as the snapshot exists.
+    Key Should Match Local File         ${SNAP_KEY_PATH_ONE}       /etc/hosts
+
+After Waiting Keys Still Match Through Snapshot And On Live Bucket
+    [Documentation]     Add a new key on the live bucket, wait so defrag may run, then confirm the snapshot
+    ...                 still has the old file and the live bucket has the new one.
+    ${key_two} =            snapshot-setup.Create key           ${VOLUME}       ${BUCKET}       /etc/passwd
+    Set Suite Variable      ${KEY_TWO}          ${key_two}
+    Set Suite Variable      ${LIVE_KEY_TWO_PATH}                   /${VOLUME}/${BUCKET}/${key_two}
+    Sleep                   ${DEFRAG_WAIT_SECONDS}
+    Key Should Match Local File         ${SNAP_KEY_PATH_ONE}       /etc/hosts
+    Key Should Match Local File         ${LIVE_KEY_TWO_PATH}       /etc/passwd
+
+Snapshot List Still Shows Active
+    [Documentation]     ozone sh snapshot ls still lists this snapshot as SNAPSHOT_ACTIVE.
+    ${result} =     Execute             ozone sh snapshot ls /${VOLUME}/${BUCKET}
+                    Should contain      ${result}       ${SNAPSHOT_ONE}
+                    Should contain      ${result}       SNAPSHOT_ACTIVE
+
+Second Snapshot Sees All Keys So Far
+    [Documentation]     Take another snapshot after adding a third key; older snapshot still only has the first key;
+    ...                 newer snapshot can read all three keys.
+    ${key_three} =            snapshot-setup.Create key           ${VOLUME}       ${BUCKET}       /etc/group
+    Set Suite Variable      ${KEY_THREE}        ${key_three}
+    ${snapshot_two} =       Create snapshot                     ${VOLUME}       ${BUCKET}
+    Set Suite Variable      ${SNAPSHOT_TWO}     ${snapshot_two}
+    Key Should Match Local File         /${VOLUME}/${BUCKET}/${SNAPSHOT_INDICATOR}/${SNAPSHOT_ONE}/${KEY_ONE}       /etc/hosts
+    Key Should Match Local File         /${VOLUME}/${BUCKET}/${SNAPSHOT_INDICATOR}/${SNAPSHOT_TWO}/${KEY_ONE}       /etc/hosts
+    Key Should Match Local File         /${VOLUME}/${BUCKET}/${SNAPSHOT_INDICATOR}/${SNAPSHOT_TWO}/${KEY_TWO}       /etc/passwd
+    Key Should Match Local File         /${VOLUME}/${BUCKET}/${SNAPSHOT_INDICATOR}/${SNAPSHOT_TWO}/${KEY_THREE}     /etc/group
+
+Snapshot Diff Starts A New Job
+    [Documentation]     Comparing the two snapshots prints the usual “new job” and --get-report hint (like snapshot-sh.robot).
+    ${result} =     Execute             ozone sh snapshot diff /${VOLUME}/${BUCKET} ${SNAPSHOT_ONE} ${SNAPSHOT_TWO}
+                    Should contain      ${result}       Submitting a new job
+                    Should contain      ${result}       --get-report option
+
+Snapshot Diff Json Report Lists Added Keys
+    [Documentation]     Full JSON report finishes with DONE and lists the keys that appeared after the first snapshot.
+    ${result} =     Execute             ozone sh snapshot diff --get-report --json /${VOLUME}/${BUCKET} ${SNAPSHOT_ONE} ${SNAPSHOT_TWO}
+                    Should contain      echo '${result}' | jq '.jobStatus'   DONE
+                    Should contain      echo '${result}' | jq '.snapshotDiffReport.volumeName'    ${VOLUME}
+                    Should contain      echo '${result}' | jq '.snapshotDiffReport.bucketName'    ${BUCKET}
+                    Should contain      echo '${result}' | jq '.snapshotDiffReport.fromSnapshot'  ${SNAPSHOT_ONE}
+                    Should contain      echo '${result}' | jq '.snapshotDiffReport.toSnapshot'    ${SNAPSHOT_TWO}
+                    Should contain      echo '${result}' | jq '.snapshotDiffReport.diffList | .[].sourcePath'    ${KEY_TWO}
+                    Should contain      echo '${result}' | jq '.snapshotDiffReport.diffList | .[].sourcePath'    ${KEY_THREE}
+
+After More Defrag Time Snapshot Info And Reads Stay Consistent
+    [Documentation]     Wait again so defrag can run. Re-check ozone sh snapshot info (OM metadata includes
+    ...                 checkpointDir / status) and re-read keys through snapshot paths. We do not rerun snapshot
+    ...                 diff --get-report here: a completed diff report is served from cache for
+    ...                 ozone.om.snapshot.diff.job.report.persistent.time, so that call would not retrigger work.
+    Sleep                   ${DEFRAG_WAIT_SECONDS}
+    ${info_one} =       Execute             ozone sh snapshot info /${VOLUME}/${BUCKET} ${SNAPSHOT_ONE}
+                        Should contain      echo '${info_one}' | jq '.volumeName'       ${VOLUME}
+                        Should contain      echo '${info_one}' | jq '.bucketName'       ${BUCKET}
+                        Should contain      echo '${info_one}' | jq '.name'             ${SNAPSHOT_ONE}
+                        Should contain      echo '${info_one}' | jq '.snapshotStatus'   SNAPSHOT_ACTIVE
+    ${snap_id_one} =    Execute             echo '${info_one}' | jq -r '.snapshotId'
+                        Should contain      echo '${info_one}' | jq -r '.checkpointDir'    ${snap_id_one}
+    ${info_two} =       Execute             ozone sh snapshot info /${VOLUME}/${BUCKET} ${SNAPSHOT_TWO}
+                        Should contain      echo '${info_two}' | jq '.volumeName'       ${VOLUME}
+                        Should contain      echo '${info_two}' | jq '.bucketName'       ${BUCKET}
+                        Should contain      echo '${info_two}' | jq '.name'             ${SNAPSHOT_TWO}
+                        Should contain      echo '${info_two}' | jq '.snapshotStatus'   SNAPSHOT_ACTIVE
+    ${snap_id_two} =    Execute             echo '${info_two}' | jq -r '.snapshotId'
+                        Should contain      echo '${info_two}' | jq -r '.checkpointDir'    ${snap_id_two}
+    Key Should Match Local File         /${VOLUME}/${BUCKET}/${SNAPSHOT_INDICATOR}/${SNAPSHOT_ONE}/${KEY_ONE}       /etc/hosts
+    Key Should Match Local File         /${VOLUME}/${BUCKET}/${SNAPSHOT_INDICATOR}/${SNAPSHOT_TWO}/${KEY_ONE}       /etc/hosts
+    Key Should Match Local File         /${VOLUME}/${BUCKET}/${SNAPSHOT_INDICATOR}/${SNAPSHOT_TWO}/${KEY_TWO}       /etc/passwd
+    Key Should Match Local File         /${VOLUME}/${BUCKET}/${SNAPSHOT_INDICATOR}/${SNAPSHOT_TWO}/${KEY_THREE}     /etc/group
+
+Delete Older Snapshot Younger One Still Readable
+    [Documentation]     Delete the first snapshot; it shows SNAPSHOT_DELETED; read all keys through the second snapshot path.
+    ${output} =         Execute           ozone sh snapshot delete /${VOLUME}/${BUCKET} ${SNAPSHOT_ONE}
+                        Should not contain                    ${output}       Failed
+    ${output} =         Execute            ozone sh snapshot ls /${VOLUME}/${BUCKET} | jq '[.[] | select(.name == "${SNAPSHOT_ONE}") | .snapshotStatus] | if length > 0 then .[] else "SNAPSHOT_DELETED" end'
+                        Should contain                        ${output}       SNAPSHOT_DELETED
+    Key Should Match Local File         /${VOLUME}/${BUCKET}/${SNAPSHOT_INDICATOR}/${SNAPSHOT_TWO}/${KEY_ONE}       /etc/hosts
+    Key Should Match Local File         /${VOLUME}/${BUCKET}/${SNAPSHOT_INDICATOR}/${SNAPSHOT_TWO}/${KEY_TWO}       /etc/passwd
+    Key Should Match Local File         /${VOLUME}/${BUCKET}/${SNAPSHOT_INDICATOR}/${SNAPSHOT_TWO}/${KEY_THREE}     /etc/group
+
+*** Keywords ***
+Prepare Suite With Bucket And First Snapshot
+    Setup volume and bucket
+    ${key_one} =            snapshot-setup.Create key           ${VOLUME}       ${BUCKET}       /etc/hosts
+    Set Suite Variable      ${KEY_ONE}                          ${key_one}
+    ${snapshot_one} =       Create snapshot                     ${VOLUME}       ${BUCKET}
+    Set Suite Variable      ${SNAPSHOT_ONE}                     ${snapshot_one}
+    Set Suite Variable      ${SNAP_KEY_PATH_ONE}                /${VOLUME}/${BUCKET}/${SNAPSHOT_INDICATOR}/${snapshot_one}/${key_one}