diff --git a/Resources/shell-integration/cmux-bash-integration.bash b/Resources/shell-integration/cmux-bash-integration.bash
index db9ae9f3..1d54c670 100644
--- a/Resources/shell-integration/cmux-bash-integration.bash
+++ b/Resources/shell-integration/cmux-bash-integration.bash
@@ -1,26 +1,35 @@
 # cmux shell integration for bash
 
+# Cache which send tool is available to avoid repeated PATH lookups.
+_CMUX_SEND_TOOL=""
+_cmux_detect_send_tool() {
+    if command -v ncat >/dev/null 2>&1; then
+        _CMUX_SEND_TOOL=ncat
+    elif command -v socat >/dev/null 2>&1; then
+        _CMUX_SEND_TOOL=socat
+    elif command -v nc >/dev/null 2>&1; then
+        _CMUX_SEND_TOOL=nc
+    fi
+}
+# Detection deferred to after _cmux_fix_path (end of file).
+
 _cmux_send() {
     local payload="$1"
-    if command -v ncat >/dev/null 2>&1; then
-        printf '%s\n' "$payload" | ncat -w 1 -U "$CMUX_SOCKET_PATH" --send-only
-    elif command -v socat >/dev/null 2>&1; then
-        printf '%s\n' "$payload" | socat -T 1 - "UNIX-CONNECT:$CMUX_SOCKET_PATH" >/dev/null 2>&1
-    elif command -v nc >/dev/null 2>&1; then
-        # Some nc builds don't support unix sockets, but keep as a last-ditch fallback.
-        #
-        # Important: macOS/BSD nc will often wait for the peer to close the socket
-        # after it has finished writing. cmux keeps the connection open, so
-        # a plain `nc -U` can hang indefinitely and leak background processes.
-        #
-        # Prefer flags that guarantee we exit after sending, and fall back to a
-        # short timeout so we never block sidebar updates.
-        if printf '%s\n' "$payload" | nc -N -U "$CMUX_SOCKET_PATH" >/dev/null 2>&1; then
-            :
-        else
-            printf '%s\n' "$payload" | nc -w 1 -U "$CMUX_SOCKET_PATH" >/dev/null 2>&1 || true
-        fi
-    fi
+    case "$_CMUX_SEND_TOOL" in
+        ncat)
+            printf '%s\n' "$payload" | ncat -w 1 -U "$CMUX_SOCKET_PATH" --send-only
+            ;;
+        socat)
+            printf '%s\n' "$payload" | socat -T 1 - "UNIX-CONNECT:$CMUX_SOCKET_PATH" >/dev/null 2>&1
+            ;;
+        nc)
+            if printf '%s\n' "$payload" | nc -N -U "$CMUX_SOCKET_PATH" >/dev/null 2>&1; then
+                :
+            else
+                printf '%s\n' "$payload" | nc -w 1 -U "$CMUX_SOCKET_PATH" >/dev/null 2>&1 || true
+            fi
+            ;;
+    esac
 }
 
 _cmux_restore_scrollback_once() {
@@ -271,6 +280,7 @@ _cmux_clear_pr_for_panel() {
     [[ -S "$CMUX_SOCKET_PATH" ]] || return 0
     [[ -n "$CMUX_TAB_ID" ]] || return 0
     [[ -n "$CMUX_PANEL_ID" ]] || return 0
+    # Synchronous: must arrive before the next report_pr from the poll loop.
     _cmux_send "clear_pr --tab=$CMUX_TAB_ID --panel=$CMUX_PANEL_ID"
 }
 
@@ -445,9 +455,10 @@ _cmux_run_pr_probe_with_timeout() {
 
 _cmux_stop_pr_poll_loop() {
     if [[ -n "$_CMUX_PR_POLL_PID" ]]; then
-        # Use SIGKILL directly to avoid blocking sleep in preexec.
-        # The poll loop is lightweight and safe to kill abruptly.
-        _cmux_kill_process_tree "$_CMUX_PR_POLL_PID" KILL
+        # Process-group kill: background jobs are process-group leaders, so
+        # negative PID kills the loop + all descendants (gh, sleep) without
+        # the synchronous /bin/ps + awk of tree-kill (~5-13ms).
+        kill -KILL -- -"$_CMUX_PR_POLL_PID" 2>/dev/null || true
         _CMUX_PR_POLL_PID=""
     fi
 }
@@ -702,4 +713,6 @@ _cmux_fix_path() {
 _cmux_fix_path
 unset -f _cmux_fix_path
 
+_cmux_detect_send_tool
+
 _cmux_install_prompt_command
diff --git a/Resources/shell-integration/cmux-zsh-integration.zsh b/Resources/shell-integration/cmux-zsh-integration.zsh
index 1364f4a6..273d062c 100644
--- a/Resources/shell-integration/cmux-zsh-integration.zsh
+++ b/Resources/shell-integration/cmux-zsh-integration.zsh
@@ -1,21 +1,29 @@
 # cmux shell integration for zsh
 # Injected automatically — do not source manually
 
+# Prefer zsh/net/unix for socket sends (no fork, ~0.2ms per send vs ~3ms
+# for fork+exec of ncat/socat/nc).  Falls back to external tools if the
+# module is unavailable.
+typeset -g _CMUX_HAS_ZSOCKET=0
+if zmodload zsh/net/unix 2>/dev/null; then
+    _CMUX_HAS_ZSOCKET=1
+fi
+
 _cmux_send() {
     local payload="$1"
+    if (( _CMUX_HAS_ZSOCKET )); then
+        local fd
+        zsocket "$CMUX_SOCKET_PATH" 2>/dev/null || return 1
+        fd=$REPLY
+        print -u $fd -r -- "$payload" 2>/dev/null
+        exec {fd}>&- 2>/dev/null
+        return 0
+    fi
     if command -v ncat >/dev/null 2>&1; then
         print -r -- "$payload" | ncat -w 1 -U "$CMUX_SOCKET_PATH" --send-only
     elif command -v socat >/dev/null 2>&1; then
         print -r -- "$payload" | socat -T 1 - "UNIX-CONNECT:$CMUX_SOCKET_PATH" >/dev/null 2>&1
     elif command -v nc >/dev/null 2>&1; then
-        # Some nc builds don't support unix sockets, but keep as a last-ditch fallback.
-        #
-        # Important: macOS/BSD nc will often wait for the peer to close the socket
-        # after it has finished writing. cmux keeps the connection open, so
-        # a plain `nc -U` can hang indefinitely and leak background processes.
-        #
-        # Prefer flags that guarantee we exit after sending, and fall back to a
-        # short timeout so we never block sidebar updates.
         if print -r -- "$payload" | nc -N -U "$CMUX_SOCKET_PATH" >/dev/null 2>&1; then
             :
         else
@@ -24,6 +32,16 @@ _cmux_send() {
     fi
 }
 
+# Fire-and-forget send: synchronous when zsocket is available (fast, no fork),
+# backgrounded otherwise.
+_cmux_send_bg() {
+    if (( _CMUX_HAS_ZSOCKET )); then
+        _cmux_send "$1"
+    else
+        { _cmux_send "$1" } >/dev/null 2>&1 &!
+    fi
+}
+
 _cmux_restore_scrollback_once() {
     local path="${CMUX_RESTORE_SCROLLBACK_FILE:-}"
     [[ -n "$path" ]] || return 0
@@ -337,9 +355,7 @@ _cmux_report_tty_once() {
     [[ -n "$payload" ]] || return 0
 
     _CMUX_TTY_REPORTED=1
-    {
-        _cmux_send "$payload"
-    } >/dev/null 2>&1 &!
+    _cmux_send_bg "$payload"
 }
 
 _cmux_report_shell_activity_state() {
@@ -350,9 +366,7 @@ _cmux_report_shell_activity_state() {
     [[ -n "$CMUX_PANEL_ID" ]] || return 0
     [[ "$_CMUX_SHELL_ACTIVITY_LAST" == "$state" ]] && return 0
     _CMUX_SHELL_ACTIVITY_LAST="$state"
-    {
-        _cmux_send "report_shell_state $state --tab=$CMUX_TAB_ID --panel=$CMUX_PANEL_ID"
-    } >/dev/null 2>&1 &!
+    _cmux_send_bg "report_shell_state $state --tab=$CMUX_TAB_ID --panel=$CMUX_PANEL_ID"
 }
 
 _cmux_ports_kick() {
@@ -362,9 +376,7 @@ _cmux_ports_kick() {
     [[ -n "$CMUX_TAB_ID" ]] || return 0
     [[ -n "$CMUX_PANEL_ID" ]] || return 0
     _CMUX_PORTS_LAST_RUN=$EPOCHSECONDS
-    {
-        _cmux_send "ports_kick --tab=$CMUX_TAB_ID --panel=$CMUX_PANEL_ID"
-    } >/dev/null 2>&1 &!
+    _cmux_send_bg "ports_kick --tab=$CMUX_TAB_ID --panel=$CMUX_PANEL_ID"
 }
 
 _cmux_report_git_branch_for_path() {
@@ -392,7 +404,7 @@ _cmux_clear_pr_for_panel() {
     [[ -S "$CMUX_SOCKET_PATH" ]] || return 0
     [[ -n "$CMUX_TAB_ID" ]] || return 0
     [[ -n "$CMUX_PANEL_ID" ]] || return 0
-    _cmux_send "clear_pr --tab=$CMUX_TAB_ID --panel=$CMUX_PANEL_ID"
+    _cmux_send_bg "clear_pr --tab=$CMUX_TAB_ID --panel=$CMUX_PANEL_ID"
 }
 
 _cmux_pr_output_indicates_no_pull_request() {
@@ -567,9 +579,10 @@ _cmux_run_pr_probe_with_timeout() {
 
 _cmux_stop_pr_poll_loop() {
     if [[ -n "$_CMUX_PR_POLL_PID" ]]; then
-        # Use SIGKILL directly to avoid blocking sleep in preexec.
-        # The poll loop is lightweight and safe to kill abruptly.
-        _cmux_kill_process_tree "$_CMUX_PR_POLL_PID" KILL
+        # Process-group kill: background jobs are process-group leaders, so
+        # negative PID kills the loop + all descendants (gh, sleep) without
+        # the synchronous /bin/ps + awk of tree-kill (~5-13ms).
+        kill -KILL -- -"$_CMUX_PR_POLL_PID" 2>/dev/null || true
         _CMUX_PR_POLL_PID=""
     fi
 }
@@ -682,7 +695,7 @@ _cmux_precmd() {
     _cmux_report_shell_activity_state prompt
 
     # Handle cases where Ghostty integration initializes after this file.
-    _cmux_patch_ghostty_semantic_redraw
+    (( _CMUX_GHOSTTY_SEMANTIC_PATCHED )) || _cmux_patch_ghostty_semantic_redraw
 
     if [[ -z "$_CMUX_TTY_NAME" ]]; then
         local t
@@ -717,11 +730,8 @@ _cmux_precmd() {
     # This is also the simplest way to test sidebar directory behavior end-to-end.
     if [[ "$pwd" != "$_CMUX_PWD_LAST_PWD" ]]; then
         _CMUX_PWD_LAST_PWD="$pwd"
-        {
-            # Quote to preserve spaces.
-            local qpwd="${pwd//\"/\\\"}"
-            _cmux_send "report_pwd \"${qpwd}\" --tab=$CMUX_TAB_ID --panel=$CMUX_PANEL_ID"
-        } >/dev/null 2>&1 &!
+        local qpwd="${pwd//\"/\\\"}"
+        _cmux_send_bg "report_pwd \"${qpwd}\" --tab=$CMUX_TAB_ID --panel=$CMUX_PANEL_ID"
     fi
 
     # Git branch/dirty: update immediately on directory change, otherwise every ~3s.