diff --git a/00-RELEASENOTES b/00-RELEASENOTES
index 79e8dbe443f..bfc81c7dc53 100644
--- a/00-RELEASENOTES
+++ b/00-RELEASENOTES
@@ -19,6 +19,25 @@ The release notes contain PRs from multiple repositories:
 #Tn = Time Series (https://github.com/RedisTimeSeries/RedisTimeSeries)
 #Pn = Probabilistic (https://github.com/RedisBloom/RedisBloom)
 
+
+=============================================================
+8.2.1 (v8.2.1)    Committed  Mon 18 Aug 2025 12:00:00 IST
+=============================================================
+
+Update urgency: `MODERATE`: Program an upgrade of the server, but it's not urgent.
+
+### Bug fixes
+
+- #14240 `INFO KEYSIZES` - potential incorrect histogram updates on cluster mode with modules
+- #14274 Disable Active Defrag during flushing replica
+- #14276 `XADD` or `XTRIM` can crash the server after loading RDB
+- #Q6601 Potential crash when running `FLUSHDB` (MOD-10681)
+
+### Performance and resource utilization
+
+- Query Engine - LeanVec and LVQ proprietary Intel optimizations were removed from Redis Open Source
+- #Q6621 Fix regression in `INFO` (MOD-10779)
+
 ===========================================================
 8.2 GA (v8.2.0)    Released Mon 4 Aug 2025 15:00:00 IST
 ===========================================================
diff --git a/src/replication.c b/src/replication.c
index 486d94a5dc1..767b3473d2b 100644
--- a/src/replication.c
+++ b/src/replication.c
@@ -1949,7 +1949,17 @@ static void rdbLoadEmptyDbFunc(void) {
     serverLog(LL_NOTICE, "MASTER <-> REPLICA sync: Flushing old data");
     int empty_db_flags = server.repl_slave_lazy_flush ? EMPTYDB_ASYNC :
                                                         EMPTYDB_NO_FLAGS;
+
+    /* Temporarily disable active defragmentation during database flush.
+     * This prevents defrag from being triggered in replicationEmptyDbCallback()
+     * which could modify the database while it's being emptied. */
+    int orig_active_defrag = server.active_defrag_enabled;
+    server.active_defrag_enabled = 0;
+
     emptyData(-1, empty_db_flags, replicationEmptyDbCallback);
+
+    /* Restore the original active defragmentation. */
+    server.active_defrag_enabled = orig_active_defrag;
 }
 
 /* Once we have a link with the master and the synchronization was
diff --git a/src/t_stream.c b/src/t_stream.c
index e9b52fd96d7..5779544510a 100644
--- a/src/t_stream.c
+++ b/src/t_stream.c
@@ -2705,6 +2705,7 @@ int streamEntryIsReferenced(stream *s, streamID *id) {
         return 1;
 
     /* Check if the message is in any consumer group's PEL */
+    if (!s->cgroups_ref) return 0;
     unsigned char buf[sizeof(streamID)];
     streamEncodeID(buf, id);
     return raxFind(s->cgroups_ref, buf, sizeof(streamID), NULL);
diff --git a/src/version.h b/src/version.h
index 53dd09f245b..d417d619e66 100644
--- a/src/version.h
+++ b/src/version.h
@@ -1,2 +1,3 @@
-#define REDIS_VERSION "8.2.0"
-#define REDIS_VERSION_NUM 0x00080200
+/* Version information */
+#define REDIS_VERSION "8.2.1"
+#define REDIS_VERSION_NUM 0x00080201
diff --git a/tests/unit/memefficiency.tcl b/tests/unit/memefficiency.tcl
index 68c44c6b484..062bff09233 100644
--- a/tests/unit/memefficiency.tcl
+++ b/tests/unit/memefficiency.tcl
@@ -67,6 +67,14 @@ run_solo {defrag} {
         }
     }
 
+    proc discard_replies_every {rd count frequency discard_num} {
+        if {$count % $frequency == 0} {
+            for {set k 0} {$k < $discard_num} {incr k} {
+                $rd read ; # Discard replies
+            }
+        }
+    }
+
     proc test_active_defrag {type} {
     if {[string match {*jemalloc*} [s mem_allocator]] && [r debug mallctl arenas.page] <= 8192} {
         test "Active defrag main dictionary: $type" {
@@ -339,11 +347,7 @@ run_solo {defrag} {
                     $rd hset bighash $j [concat "asdfasdfasdf" $j]
 
                     incr count
-                    if {$count % 10000 == 0} {
-                        for {set k 0} {$k < 10000} {incr k} {
-                            $rd read ; # Discard replies
-                        }
-                    }
+                    discard_replies_every $rd $count 10000 10000
                 }
                 # creating that big hash, increased used_memory, so the relative frag goes down
                 set expected_frag 1.3
@@ -355,11 +359,7 @@ run_solo {defrag} {
                 $rd setrange $j 150 a
 
                 incr count
-                if {$count % 10000 == 0} {
-                    for {set k 0} {$k < 10000} {incr k} {
-                        $rd read ; # Discard replies
-                    }
-                }
+                discard_replies_every $rd $count 10000 10000
             }
             assert_equal [r dbsize] 500016
 
@@ -369,11 +369,7 @@ run_solo {defrag} {
                 $rd del $j
 
                 incr count
-                if {$count % 10000 == 0} {
-                    for {set k 0} {$k < 10000} {incr k} {
-                        $rd read ; # Discard replies
-                    }
-                }
+                discard_replies_every $rd $count 10000 10000
             }
             assert_equal [r dbsize] 250016
 
@@ -769,12 +765,7 @@ run_solo {defrag} {
                 $rd lpush biglist2 $val
 
                 incr count
-                if {$count % 10000 == 0} {
-                    for {set k 0} {$k < 10000} {incr k} {
-                        $rd read ; # Discard replies
-                        $rd read ; # Discard replies
-                    }
-                }
+                discard_replies_every $rd $count 10000 20000
             }
 
             # create some fragmentation
@@ -884,11 +875,7 @@ run_solo {defrag} {
                     $rd setrange $j 600 x
 
                     incr count
-                    if {$count % 10000 == 0} {
-                        for {set k 0} {$k < 10000} {incr k} {
-                            $rd read ; # Discard replies
-                        }
-                    }
+                    discard_replies_every $rd $count 10000 10000
                 }
 
                 # create some fragmentation of 50%
@@ -898,11 +885,7 @@ run_solo {defrag} {
                     incr sent
                     incr j 1
 
-                    if {$sent % 10000 == 0} {
-                        for {set k 0} {$k < 10000} {incr k} {
-                            $rd read ; # Discard replies
-                        }
-                    }
+                    discard_replies_every $rd $sent 10000 10000
                 }
 
                 # create higher fragmentation in the first slab
@@ -959,6 +942,70 @@ run_solo {defrag} {
     }
     }
 
+    test "Active defrag can't be triggered during replicaof database flush. See issue #14267" {
+        start_server {tags {"repl"} overrides {save ""}} {
+            set master_host [srv 0 host]
+            set master_port [srv 0 port]
+
+            start_server {overrides {save ""}} {
+                set replica [srv 0 client]
+                set rd [redis_deferring_client 0]
+
+                $replica config set hz 100
+                $replica config set activedefrag no
+                $replica config set active-defrag-threshold-lower 5
+                $replica config set active-defrag-cycle-min 65
+                $replica config set active-defrag-cycle-max 75
+                $replica config set active-defrag-ignore-bytes 2mb
+
+                # add a mass of string keys
+                set count 0
+                for {set j 0} {$j < 500000} {incr j} {
+                    $rd setrange $j 150 a
+
+                    incr count
+                    discard_replies_every $rd $count 10000 10000
+                }
+                assert_equal [$replica dbsize] 500000
+
+                # create some fragmentation
+                set count 0
+                for {set j 0} {$j < 500000} {incr j 2} {
+                    $rd del $j
+
+                    incr count
+                    discard_replies_every $rd $count 10000 10000
+                }
+                $rd close
+                assert_equal [$replica dbsize] 250000
+
+                catch {$replica config set activedefrag yes} e
+                if {[$replica config get activedefrag] eq "activedefrag yes"} {
+                    # Start replication sync which will flush the replica's database,
+                    # then enable defrag to run concurrently with the database flush.
+                    $replica replicaof $master_host $master_port
+
+                    # wait for the active defrag to start working (decision once a second)
+                    wait_for_condition 50 100 {
+                        [s total_active_defrag_time] ne 0
+                    } else {
+                        after 120 ;# serverCron only updates the info once in 100ms
+                        puts [$replica info memory]
+                        puts [$replica info stats]
+                        puts [$replica memory malloc-stats]
+                        fail "defrag not started."
+                    }
+
+                    wait_for_sync $replica
+
+                    # wait for the active defrag to stop working (db has been emptied during replication sync)
+                    wait_for_defrag_stop 500 100
+                    assert_equal [$replica dbsize] 0
+                }
+            }
+        }
+    } {} {defrag external:skip tsan:skip cluster}
+
     start_cluster 1 0 {tags {"defrag external:skip tsan:skip cluster"} overrides {appendonly yes auto-aof-rewrite-percentage 0 save "" loglevel notice}} {
         test_active_defrag "cluster"
     }
diff --git a/tests/unit/type/stream.tcl b/tests/unit/type/stream.tcl
index cbd0f7ce0f9..9d888589d6b 100644
--- a/tests/unit/type/stream.tcl
+++ b/tests/unit/type/stream.tcl
@@ -244,6 +244,33 @@ start_server {
         assert {[r XLEN mystream] == 1} ;# Successfully trimmed to 1 entries
     }
 
+    test {XADD with ACKED option doesn't crash after DEBUG RELOAD} {
+        r DEL mystream
+        r XADD mystream 1-0 f v
+
+        # Create a consumer group and read one message
+        r XGROUP CREATE mystream mygroup 0
+        set records [r XREADGROUP GROUP mygroup consumer1 COUNT 1 STREAMS mystream >]
+        assert_equal [lindex [r XPENDING mystream mygroup] 0] 1
+
+        # After reload, the reference relationship between consumer groups and messages
+        # is correctly rebuilt, so the previously read but unacked message still cannot be deleted.
+        r DEBUG RELOAD
+        r XADD mystream MAXLEN = 1 ACKED 2-0 f v
+        assert_equal [r XLEN mystream] 2
+
+        # Acknowledge the read message so the PEL becomes empty
+        r XACK mystream mygroup [lindex [lindex [lindex [lindex $records 0] 1] 0] 0]
+        assert {[lindex [r XPENDING mystream mygroup] 0] == 0}
+
+        # After reload, since PEL is empty, no cgroup references will be recreated.
+        r DEBUG RELOAD
+
+        # ACKED option should work correctly even without cgroup references.
+        r XADD mystream MAXLEN = 1 ACKED 3-0 f v
+        assert_equal [r XLEN mystream] 2
+    } {} {needs:debug}
+
     test {XADD with MAXLEN option and DELREF option} {
         r DEL mystream
         r XADD mystream 1-0 f v