diff --git a/src/Makefile b/src/Makefile
index 9d8125609b3..a91fd52da7e 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -570,7 +570,7 @@ test: $(REDIS_SERVER_NAME) $(REDIS_CHECK_AOF_NAME) $(REDIS_CLI_NAME) $(REDIS_BEN
 	@(cd ..; ./runtest)
 
 test-asan: $(REDIS_SERVER_NAME) $(REDIS_CHECK_AOF_NAME) $(REDIS_CLI_NAME) $(REDIS_BENCHMARK_NAME)
-	@(cd ..; ./runtest --tags -nosanitizer)
+	@(cd ..; ./runtest --tags -nosanitizer --asan)
 
 test-modules: $(REDIS_SERVER_NAME)
 	@(cd ..; ./runtest-moduleapi)
diff --git a/src/debug.c b/src/debug.c
index 88af0a22dc6..4a43d01de86 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -2288,6 +2288,14 @@ int memtest_test_linux_anonymous_maps(void) {
         end_addr = strtoul(end,NULL,16);
         size = end_addr-start_addr;
 
+        if (regions >= MEMTEST_MAX_REGIONS) {
+            snprintf(logbuf,sizeof(logbuf),
+                "*** Too many memory regions (max %d), skipping remaining regions\n",
+                MEMTEST_MAX_REGIONS);
+            if (write(fd,logbuf,strlen(logbuf)) == -1) { /* Nothing to do. */ }
+            break;
+        }
+
         start_vect[regions] = start_addr;
         size_vect[regions] = size;
         snprintf(logbuf,sizeof(logbuf),
@@ -2338,6 +2346,24 @@ void killThreads(void) {
 
 void doFastMemoryTest(void) {
 #if defined(HAVE_PROC_MAPS)
+#if defined(__has_feature)
+#  if __has_feature(address_sanitizer)
+#    define RUNNING_ASAN 1
+#  endif
+#endif
+#ifdef __SANITIZE_ADDRESS__
+#  define RUNNING_ASAN 1
+#endif
+
+#ifdef RUNNING_ASAN
+    /* Skip memory test when running under AddressSanitizer as it will
+     * interfere with ASAN's shadow memory and cause false positives. */
+    if (server.memcheck_enabled) {
+        serverLogRaw(LL_WARNING|LL_RAW, "\n------ FAST MEMORY TEST ------\n");
+        serverLogRaw(LL_WARNING|LL_RAW,
+            "Memory test skipped: running under AddressSanitizer\n");
+    }
+#else
     if (server.memcheck_enabled) {
         /* Test memory */
         serverLogRaw(LL_WARNING|LL_RAW, "\n------ FAST MEMORY TEST ------\n");
@@ -2350,6 +2376,7 @@ void doFastMemoryTest(void) {
                 "Fast memory test PASSED, however your memory can still be broken. Please run a memory test for several hours if possible.\n");
         }
     }
+#endif
 #endif /* HAVE_PROC_MAPS */
 }
 
diff --git a/src/networking.c b/src/networking.c
index 907687bf063..b7acad84bf2 100644
--- a/src/networking.c
+++ b/src/networking.c
@@ -1793,6 +1793,7 @@ static void resetReusableQueryBuf(client *c) {
 static void deferFreeClient(client *c) {
     sds client_desc;
     serverAssert(c->keyrequests_count);
+    if (c->CLIENT_DEFERED_CLOSING) return;
 
     client_desc = catClientInfoString(sdsempty(), c);
     serverLog(LL_NOTICE, "Defer client close: %s", client_desc);
@@ -1810,17 +1811,25 @@ void freeClientsInDeferedQueue(void) {
     listIter li;
     listNode *ln;
 
+    /* We can safely use listIter here because listNext() saves the next node
+     * pointer BEFORE returning current node, so deleting current node doesn't
+     * invalidate the iterator. However, we must delete the node BEFORE calling
+     * freeClient() to avoid use-after-free if freeClient() recurses. */
     listRewind(server.clients_to_free, &li);
     while ((ln = listNext(&li))) {
         client *c = listNodeValue(ln);
         if (!c->keyrequests_count) {
             client_desc = catClientInfoString(sdsempty(), c);
             c->CLIENT_DEFERED_CLOSING = 0;
+            /* IMPORTANT: Remove from list BEFORE freeing to avoid:
+             * 1. Use-after-free if freeClient() recurses back here
+             * 2. Iterator pointing to freed memory */
+            listDelNode(server.clients_to_free, ln);
             freeClient(c);
             serverLog(LL_NOTICE, "Defered client closed: %s", client_desc);
             sdsfree(client_desc);
-            listDelNode(server.clients_to_free,ln);
         }
+        /* If client has pending key requests, skip it and continue with next client */
     }
 }
 
diff --git a/src/server.c b/src/server.c
index 58795faf3eb..28ea1454235 100644
--- a/src/server.c
+++ b/src/server.c
@@ -1067,8 +1067,17 @@ int updateClientMemUsageAndBucket(client *c) {
      * running_tid is the main thread. The true main thread is allowed to call
      * this function on clients handled by IO-threads as it makes sure the
      * IO-threads are paused, f.e see cleintsCron() and evictClients(). */
+#ifdef ENABLE_SWAP
+    if (!((pthread_equal(pthread_self(), server.main_thread_id) ||
+                  c->running_tid == IOTHREAD_MAIN_THREAD_ID) && c->conn)) {
+        return 0;
+    }
+
+#else
     serverAssert((pthread_equal(pthread_self(), server.main_thread_id) ||
                   c->running_tid == IOTHREAD_MAIN_THREAD_ID) && c->conn);
+#endif
+
     int allow_eviction = clientEvictionAllowed(c);
     removeClientFromMemUsageBucket(c, allow_eviction);
 
diff --git a/tests/integration/failover.tcl b/tests/integration/failover.tcl
index bd33f84aba6..4b623803040 100644
--- a/tests/integration/failover.tcl
+++ b/tests/integration/failover.tcl
@@ -1,4 +1,10 @@
 start_server {tags {"failover external:skip"} overrides {save {}}} {
+    if {$::asan} {
+        # ASAN needs more time to complete the failover
+        set failover_timeout 200
+    } else {
+        set failover_timeout 50
+    }
 start_server {overrides {save {}}} {
 start_server {overrides {save {}}} {
     set node_0 [srv 0 client]
@@ -83,8 +89,8 @@ start_server {overrides {save {}}} {
         # Execute the failover
         $node_0 failover to $node_1_host $node_1_port
 
-        # Wait for failover to end
-        wait_for_condition 50 100 {
+        # Wait for failover to end (increased timeout for ASAN compatibility)
+        wait_for_condition $failover_timeout 100 {
             [s 0 master_failover_state] == "no-failover"
         } else {
             fail "Failover from node 0 to node 1 did not finish"
@@ -118,8 +124,8 @@ start_server {overrides {save {}}} {
         $node_1 set CASE 1
         $node_1 FAILOVER
 
-        # Wait for failover to end
-        wait_for_condition 50 100 {
+        # Wait for failover to end (increased timeout for ASAN compatibility)
+        wait_for_condition $failover_timeout 100 {
             [s -1 master_failover_state] == "no-failover"
         } else {
             fail "Failover from node 1 to node 2 did not finish"
@@ -149,8 +155,8 @@ start_server {overrides {save {}}} {
         $node_2 set case 2
         $node_2 failover to $node_0_host $node_0_port TIMEOUT 100 FORCE
 
-        # Wait for node 0 to give up on sync attempt and start failover
-        wait_for_condition 50 100 {
+        # Wait for node 0 to give up on sync attempt and start failover (increased timeout for ASAN)
+        wait_for_condition $failover_timeout 100 {
             [s -2 master_failover_state] == "failover-in-progress"
         } else {
             fail "Failover from node 2 to node 0 did not timeout"
@@ -163,8 +169,8 @@ start_server {overrides {save {}}} {
 
         resume_process $node_0_pid
 
-        # Wait for failover to end
-        wait_for_condition 50 100 {
+        # Wait for failover to end (increased timeout for ASAN compatibility)
+        wait_for_condition $failover_timeout 100 {
             [s -2 master_failover_state] == "no-failover"
         } else {
             fail "Failover from node 2 to node 0 did not finish"
@@ -267,8 +273,8 @@ start_server {overrides {save {}}} {
         $node_0 failover to $node_1_host $node_1_port
         resume_process [srv -1 pid]
 
-        # Wait for failover to end
-        wait_for_condition 50 100 {
+        # Wait for failover to end (increased timeout for ASAN compatibility)
+        wait_for_condition $failover_timeout 100 {
             [s 0 master_failover_state] == "no-failover"
         } else {
             fail "Failover from node_0 to replica did not finish"
diff --git a/tests/swap/support/util.tcl b/tests/swap/support/util.tcl
index bc7d780986b..3a544fe4d18 100644
--- a/tests/swap/support/util.tcl
+++ b/tests/swap/support/util.tcl
@@ -477,7 +477,7 @@ proc scan_all_keys {r} {
     while {1} {
         set res [$r scan $cursor]
         set cursor [lindex $res 0]
-        lappend keys {*}[split [lindex $res 1] " "]
+        lappend keys {*}[lindex $res 1]
         if {$cursor == 0} {
             break
         }
@@ -497,36 +497,36 @@ proc swap_data_comp {r1 r2} {
     assert_equal [$r1 dbsize] [$r2 dbsize]
     set keys [scan_all_keys $r1]
     foreach key $keys {
-        set t [$r1 type {*}$key]
-        set t2 [$r2 type {*}$key]
+        set t [$r1 type $key]
+        set t2 [$r2 type $key]
         if {$t != $t2} {
             assert_failed "key '$key' type mismatch '$t' - '$t2'" ""
         }
         switch $t {
             {string} {
-                set v1 [$r1 get {*}$key]
-                set v2 [$r2 get {*}$key]
+                set v1 [$r1 get $key]
+                set v2 [$r2 get $key]
                 if {$v1 != $v2} {
                     data_conflict $t $key '' $v1 $v2
                 }
             }
             {list} {
-                set len [$r1 llen {*}$key]
-                set len2 [$r2 llen {*}$key]
+                set len [$r1 llen $key]
+                set len2 [$r2 llen $key]
                 if {$len != $len2} {
                     data_conflict $t $key '' 'LLEN:$len' 'LLEN:$len2'
                 }
                 for {set i 0} {$i < $len} {incr i} {
-                    set v1 [$r1 lindex {*}$key $i]
-                    set v2 [$r2 lindex {*}$key $i]
+                    set v1 [$r1 lindex $key $i]
+                    set v2 [$r2 lindex $key $i]
                     if {$v1 != $v2} {
                         data_conflict $t $key $i $v1 $v2
                     }
                 }
             }
             {set} {
-                set len [$r1 scard {*}$key]
-                set len2 [$r2 scard {*}$key]
+                set len [$r1 scard $key]
+                set len2 [$r2 scard $key]
                 if {$len != $len2} {
                     data_conflict $t $key '' 'SLEN:$len' 'SLEN:$len2'
                 }
@@ -538,21 +538,21 @@ proc swap_data_comp {r1 r2} {
                 }
             }
             {zset} {
-                set len [$r1 zcard {*}$key]
-                set len2 [$r2 zcard {*}$key]
+                set len [$r1 zcard $key]
+                set len2 [$r2 zcard $key]
                 if {$len != $len2} {
                     data_conflict $t $key '' 'SLEN:$len' 'SLEN:$len2'
                 }
                 set zcursor 0
                 while 1 {
-                    set res [$r1 zscan {*}$key $zcursor]
+                    set res [$r1 zscan $key $zcursor]
                     set zcursor [lindex $res 0]
                     set zdata [lindex $res 1]
                     set dlen [llength $zdata]
                     for {set i 0} {$i < $dlen} {incr i 2} {
                         set zkey [lindex $zdata $i]
                         set zscore [lindex $zdata [expr $i+1]]
-                        set zscore2 [$r2 zscore {*}$key $zkey]
+                        set zscore2 [$r2 zscore $key $zkey]
                         if {$zscore != $zscore2} {
                             data_conflict $t $key $zkey $zscore $zscore2
                         }
@@ -563,15 +563,15 @@ proc swap_data_comp {r1 r2} {
                 }
             }
             {hash} {
-                set len [$r1 hlen {*}$key]
-                set len2 [$r2 hlen {*}$key]
+                set len [$r1 hlen $key]
+                set len2 [$r2 hlen $key]
                 if {$len != $len2} {
                     data_conflict $t $key '' 'HLEN:$len' 'HLEN:$len2'
                 }
-                set hkeys [$r1 hkeys {*}$key]
+                set hkeys [$r1 hkeys $key]
                 foreach hkey $hkeys {
-                    set v1 [$r1 hget {*}$key $hkey]
-                    set v2 [$r2 hget {*}$key $hkey]
+                    set v1 [$r1 hget $key $hkey]
+                    set v2 [$r2 hget $key $hkey]
                     if {$v1 != $v2} {
                         data_conflict $t $key $hkey $v1 $v2
                     }
diff --git a/tests/swap/unit/del.tcl b/tests/swap/unit/del.tcl
index 3f6f6d326a8..712c5bf6d87 100644
--- a/tests/swap/unit/del.tcl
+++ b/tests/swap/unit/del.tcl
@@ -70,7 +70,7 @@ start_server {tags {"skip_unnecessary_rocksdb_del"}} {
         while {1} {
             set res [$r scan $cursor]
             set cursor [lindex $res 0]
-            lappend keys {*}[split [lindex $res 1] " "]
+            lappend keys {*}[lindex $res 1]
             if {$cursor == 0} {
                 break
             }
diff --git a/tests/swap/unit/expire.tcl b/tests/swap/unit/expire.tcl
index 9340bb48eaf..ebbf583f572 100644
--- a/tests/swap/unit/expire.tcl
+++ b/tests/swap/unit/expire.tcl
@@ -4,7 +4,7 @@ proc scan_all_keys {r} {
     while {1} {
         set res [$r scan $cursor]
         set cursor [lindex $res 0]
-        append keys [lindex $res 1]
+        lappend keys {*}[lindex $res 1]
         if {$cursor == 0} {
             break
         }
diff --git a/tests/test_helper.tcl b/tests/test_helper.tcl
index 883eab0f679..2e241a8bca8 100644
--- a/tests/test_helper.tcl
+++ b/tests/test_helper.tcl
@@ -78,6 +78,7 @@ set ::portcount 8000; # we don't wanna use more than 10000 to avoid collision wi
 set ::traceleaks 0
 set ::valgrind 0
 set ::tsan 0
+set ::asan 0
 set ::durable 0
 set ::tls 0
 set ::tls_module 0
@@ -650,6 +651,8 @@ for {set j 0} {$j < [llength $argv]} {incr j} {
         set ::valgrind 1
     } elseif {$opt eq {--tsan}} {
         set ::tsan 1
+    } elseif {$opt eq {--asan}} {
+        set ::asan 1
     } elseif {$opt eq {--stack-logging}} {
         if {[string match {*Darwin*} [exec uname -a]]} {
             set ::stack_logging 1