diff --git a/scripts/lib/actas-lock.sh b/scripts/lib/actas-lock.sh
index 7b00f584..b82cd799 100644
--- a/scripts/lib/actas-lock.sh
+++ b/scripts/lib/actas-lock.sh
@@ -83,6 +83,27 @@ agmsg_spawn_path() {
   printf '%s/spawn.%s__%s' "$(_actas_lock_dir)" "$t" "$a"
 }
 
+# Boot-process presence path for a spawned (team, agent). The boot script
+# generated by `spawn.sh` writes its own pid here right before exec'ing the
+# role's CLI, and removes it right after that CLI exits. Present iff a
+# launcher-spawned CLI process for that role is currently running --
+# independent of the ready sentinel above, which only
+# appears once the CLI/model reaches its own watcher-registration step. A
+# type whose actas flow is model-driven (e.g. grok-build's watcher start,
+# see docs/adr/0003) can get permanently stuck before that step -- most
+# visibly when the underlying model call itself fails (a rate/usage-limit
+# dialog the model never resolves) -- leaving no watcher and no ready
+# sentinel even though the CLI process is still alive on-screen. This file
+# lets an external liveness check (or a future spawn/status command) tell
+# "process launched and still running, registration incomplete" apart from
+# "nothing was ever launched, or it has exited." Same encoding as the lock
+# path.
+agmsg_boot_pid_path() {
+  local team="$1" agent="$2"
+  local t a; t="$(_actas_lock_encode "$team")"; a="$(_actas_lock_encode "$agent")"
+  printf '%s/boot-pid.%s__%s' "$(_actas_lock_dir)" "$t" "$a"
+}
+
 # Read the owner session_id of a lock file. Empty if no lock or unreadable.
 actas_lock_owner() {
   local lock; lock="$(actas_lock_path "$1" "$2")"
diff --git a/scripts/spawn.sh b/scripts/spawn.sh
index 3a306d1b..40e24b7a 100755
--- a/scripts/spawn.sh
+++ b/scripts/spawn.sh
@@ -411,6 +411,11 @@ if [ "$_msys_cmd_prefix" = "/" ]; then
   MSYS_GUARD="MSYS2_ARG_CONV_EXCL=/${_msys_cmd_name} "
 fi
 
+# Presence sentinel for this launch (see agmsg_boot_pid_path, lib/actas-lock.sh):
+# the boot script records its own pid here before exec'ing the CLI and clears
+# it right after, independent of whatever the CLI/model does or doesn't reach.
+BOOT_PID_PATH="$(agmsg_boot_pid_path "$TEAM" "$NAME")"
+
 BOOT_DIR="${TMPDIR:-/tmp}/agmsg-spawn"
 mkdir -p "$BOOT_DIR" 2>/dev/null || true
 # Best-effort GC of boot scripts left behind by spawns whose window was closed
@@ -433,6 +438,20 @@ esac
   # actas flow knows the session is already named <team>-<agent> (name_arg) and
   # suppresses the "rename this session" tip meant for hand-started sessions.
   echo 'export AGMSG_SPAWNED=1'
+  # Record boot-process presence before the CLI runs (see agmsg_boot_pid_path):
+  # $$ here is the boot script's own shell pid, not spawn.sh's -- it stays
+  # alive for exactly as long as the CLI below runs (foreground, not exec'd),
+  # so a liveness check on this pid tracks the CLI's lifetime even if the
+  # CLI/model never reaches its own watcher-registration step. A consumer
+  # always validates via kill(pid, 0) (same contract as every other sentinel
+  # here), so a stale file is harmless -- but the trap below still clears it
+  # on the common abnormal-exit paths (closed window/tab -> HUP, killed pane
+  # -> TERM, Ctrl-C -> INT) so it doesn't needlessly linger; only a SIGKILL
+  # (untrappable) leaves it behind for the next liveness check to invalidate.
+  printf 'mkdir -p %q 2>/dev/null || true\n' "$(_actas_lock_dir)"
+  printf 'AGMSG_BOOT_PID_PATH=%q\n' "$BOOT_PID_PATH"
+  printf 'echo $$ > "$AGMSG_BOOT_PID_PATH" 2>/dev/null || true\n'
+  printf 'trap '\''rm -f "$AGMSG_BOOT_PID_PATH" 2>/dev/null'\'' EXIT HUP TERM INT\n'
   # Drop inherited same-type session-identity vars before exec'ing the CLI (#294).
   if [ -n "$SPAWN_UNSET_VARS" ]; then
     printf 'unset %s\n' "$SPAWN_UNSET_VARS"
@@ -477,6 +496,8 @@ esac
     agmsg_role_cli_args "$AGENT_TYPE" "$SESSION_NAME" "$ACTAS_PROMPT"
     printf '\n'
   fi
+  echo 'trap - EXIT HUP TERM INT'  # CLI returned normally -- the explicit rm below covers it, not the trap
+  echo 'rm -f "$AGMSG_BOOT_PID_PATH" 2>/dev/null'  # presence over
   echo 'rm -f "$0" 2>/dev/null'   # self-clean once the agent exits
   echo 'exec "${SHELL:-/bin/bash}" -i'
 } > "$BOOT"
diff --git a/tests/test_spawn.bats b/tests/test_spawn.bats
index 681e6948..2f43bb94 100644
--- a/tests/test_spawn.bats
+++ b/tests/test_spawn.bats
@@ -183,6 +183,45 @@ teardown() {
   [[ "$output" == *"export AGMSG_SPAWNED=1"* ]]
 }
 
+@test "spawn: boot script records and clears a boot-pid presence sentinel" {
+  # The boot script writes its own pid to agmsg_boot_pid_path before running
+  # the CLI, and removes it right after -- a liveness signal independent of
+  # the ready sentinel, which only appears once the CLI/model reaches its own
+  # watcher-registration step (some types, e.g. grok-build, never get there
+  # when the underlying model call itself fails, such as an unresolved
+  # rate-limit dialog).
+  bash "$SCRIPTS/join.sh" myteam existing claude-code "$PROJ"
+  run bash "$SCRIPTS/spawn.sh" claude-code alice --project "$PROJ" --no-wait
+  [ "$status" -eq 0 ]
+
+  export SKILL_DIR="$TEST_SKILL_DIR"
+  source "$SCRIPTS/lib/actas-lock.sh"
+  local pid_path; pid_path="$(agmsg_boot_pid_path myteam alice)"
+
+  boot="$(cat "$CAPTURE")"; run cat "$boot"
+  # The literal path is assigned to a boot-local var once, then referenced by
+  # name everywhere else (write, trap, clear) rather than re-embedded.
+  [[ "$output" == *"AGMSG_BOOT_PID_PATH=$pid_path"* ]]
+  [[ "$output" == *'echo $$ > "$AGMSG_BOOT_PID_PATH"'* ]]
+  [[ "$output" == *'trap '"'"'rm -f "$AGMSG_BOOT_PID_PATH"'* ]]
+  [[ "$output" == *"EXIT HUP TERM INT"* ]]
+  [[ "$output" == *'rm -f "$AGMSG_BOOT_PID_PATH"'* ]]
+  # Written before the CLI line, cleared after it -- not the other way round.
+  # (The CLI invocation is asserted-between, not line-anchored, since it may be
+  # prefixed by MSYS2_ARG_CONV_EXCL=... even on macOS/Linux -- inert there, but
+  # it means the line doesn't start with the bare cli name.)
+  local write_line clear_line between
+  write_line="$(grep -n "AGMSG_BOOT_PID_PATH=" "$boot" | head -1 | cut -d: -f1)"
+  clear_line="$(grep -n "^rm -f \"\$AGMSG_BOOT_PID_PATH\"" "$boot" | head -1 | cut -d: -f1)"
+  [ -n "$write_line" ]
+  [ -n "$clear_line" ]
+  [ "$write_line" -lt "$clear_line" ]
+  between="$(sed -n "${write_line},${clear_line}p" "$boot")"
+  [[ "$between" == *"claude"* ]]
+  [[ "$between" == *"actas"* ]]
+  [[ "$between" == *"alice"* ]]
+}
+
 @test "spawn: a type without name_arg emits no name flag (#339)" {
   # gemini's manifest has no name_arg=, so the boot script must not name the
   # session -- no bare `-n` token, unchanged from pre-#339 behavior.