diff --git a/scripts/shell-init.sh b/scripts/shell-init.sh
index 0a3f4d1..0eb0168 100644
--- a/scripts/shell-init.sh
+++ b/scripts/shell-init.sh
@@ -37,18 +37,43 @@ fi
 
 (( INTERACTIVE )) || return 0
 
+# ---- run-once guard --------------------------------------------------------
+
+# Installed as both loginShellInit (/etc/profile) and interactiveShellInit
+# (/etc/bashrc), and /etc/profile sources /etc/bashrc, so a login shell would run
+# this twice and register starship's hooks twice. Not exported: child shells must
+# initialise on their own.
+if [[ -n ${NANUQSAURUS_SHELL_INIT_DONE:-} ]]; then
+  log_shell_init "already initialised, skipping"
+  return 0
+fi
+NANUQSAURUS_SHELL_INIT_DONE=1
+
 # ---- bash-preexec ----------------------------------------------------------
 
 if [[ -n ${BASH_VERSION:-} && -z ${bash_preexec_imported:-} && -r "@BASHPREEXEC@" ]]; then
   # shellcheck disable=SC1090
   . "@BASHPREEXEC@"
-  # Do NOT call __bp_install here. bash-preexec must install on the FIRST prompt,
-  # after starship/atuin/zoxide/ghostty have modified PROMPT_COMMAND, so that
-  # __bp_interactive_mode stays the LAST PROMPT_COMMAND entry. Installing eagerly
-  # lets later hooks land after it and silently breaks preexec (atuin recording).
   log_shell_init "bash-preexec loaded"
 fi
 
+# bash-preexec arms its DEBUG trap from __bp_interactive_mode, which it appends to
+# the END of PROMPT_COMMAND -- but its lazy installer runs in the MIDDLE of the
+# first prompt, because zoxide (below) and ghostty (~/.bashrc) append their hooks
+# after it. Those hooks then disarm the trap again, so the first command of every
+# session never reaches preexec and atuin never records it. PS0 is expanded once
+# per interactive command, before the DEBUG trap, so arming there is independent of
+# PROMPT_COMMAND ordering. Needs the non-forking ${ ...; } funsub (bash >= 5.3);
+# older bash keeps the previous behaviour.
+if [[ -n ${bash_preexec_imported:-} ]] &&
+   ((BASH_VERSINFO[0] > 5 || (BASH_VERSINFO[0] == 5 && BASH_VERSINFO[1] >= 3))); then
+  # shellcheck disable=SC2016
+  __nanuq_bp_arm='${ __bp_preexec_interactive_mode=on; }'
+  [[ ${PS0-} == *"$__nanuq_bp_arm"* ]] || PS0=$__nanuq_bp_arm${PS0-}
+  unset __nanuq_bp_arm
+  log_shell_init "bash-preexec PS0 arming enabled"
+fi
+
 # ---- starship --------------------------------------------------------------
 
 if have @STARSHIP@; then
@@ -57,8 +82,7 @@ if have @STARSHIP@; then
     */bash) eval "$(@STARSHIP@ init bash)" ;;
     */zsh)  eval "$(@STARSHIP@ init zsh)" ;;
   esac
-  # starship's bash init registers starship_precmd/starship_preexec_all with
-  # bash-preexec directly; no manual PROMPT_COMMAND wiring needed.
+  # registers starship_precmd/starship_preexec_all with bash-preexec directly
 else
   log_shell_init "starship skipped"
 fi
@@ -77,8 +101,7 @@ if have @ATUIN@; then
     */bash) eval "$(@ATUIN@ init bash)" ;;
     */zsh)  eval "$(@ATUIN@ init zsh)" ;;
   esac
-  # atuin's init registers __atuin_preexec/__atuin_precmd with bash-preexec
-  # itself; manual array wiring only caused duplicate hook entries.
+  # registers __atuin_preexec/__atuin_precmd with bash-preexec itself
 else
   log_shell_init "atuin skipped"
 fi
@@ -91,9 +114,7 @@ if have zoxide; then
     */bash) eval "$(zoxide init bash)" ;;
     */zsh)  eval "$(zoxide init zsh)" ;;
   esac
-  # zoxide's bash init hooks into bash-preexec (precmd_functions) when it is
-  # present; manual PROMPT_COMMAND wiring only pushed hooks past
-  # __bp_interactive_mode and broke preexec ordering.
+  # appends __zoxide_hook to PROMPT_COMMAND; see the PS0 note above
 else
   log_shell_init "zoxide skipped"
 fi