diff --git a/plugins/kyberforge/.apm/hooks/check-apm-current.sh b/plugins/kyberforge/.apm/hooks/check-apm-current.sh
index 2200a73..bf4a15b 100755
--- a/plugins/kyberforge/.apm/hooks/check-apm-current.sh
+++ b/plugins/kyberforge/.apm/hooks/check-apm-current.sh
@@ -38,27 +38,47 @@ command -v apm > /dev/null 2>&1 || exit 0
 # `apm outdated` and `apm update` both resolve the lockfile from the cwd.
 cd "$project_dir" || exit 0
 
+# Only ever emit fixed text plus a digit-checked count — never interpolate
+# command output into the JSON, which would need escaping this cannot do safely.
+emit() {
+  printf '{"hookSpecificOutput":{"hookEventName":"SessionStart","reloadSkills":%s,"additionalContext":"%s"}}\n' "$1" "$2"
+}
+
+# Every apm call is time-boxed, so timeout(1) is a hard requirement. It is GNU
+# coreutils: stock macOS has none, and Homebrew's coreutils installs it as
+# `gtimeout`. Calling a missing binary would exit 127, which the `|| exit 0`
+# below swallows — the hook would silently never work. Say so once instead, and
+# do not run apm unbounded.
+if command -v timeout > /dev/null 2>&1; then
+  timeout_bin="timeout"
+elif command -v gtimeout > /dev/null 2>&1; then
+  timeout_bin="gtimeout"
+else
+  emit false "The apm install currency check did not run: neither timeout nor gtimeout (GNU coreutils) is on PATH, and this hook will not run apm without a time limit. Install coreutils (macOS: brew install coreutils) or run apm outdated by hand."
+  exit 0
+fi
+
+# apm drives git for every remote ref. A remote that wants credentials must fail
+# fast, not block on a terminal prompt nobody can see until the timeout fires.
+export GIT_TERMINAL_PROMPT=0
+
 # `apm outdated` exits 0 whether or not anything is stale, so the answer has to
 # come from its output. ~0.7s against six remote refs; a hung remote must not
-# hold the session open.
+# hold the session open. -k sends SIGKILL a grace period after the SIGTERM, so a
+# child that ignores TERM cannot outlive its budget; tests/test-apm-current-hook.sh
+# sums every limit plus its grace against the hooks.json timeout.
 #
 # There is no --json/machine-readable flag on `apm outdated` (verified against
 # apm 0.28.0), so the phrase match is forced rather than chosen. Note the
 # singular: apm prints "1 outdated dependency found" when exactly one package is
 # behind, so matching only "dependencies" would silently miss a one-package
 # drift. tests/test-apm-current-hook.sh pins both spellings against the real apm.
-outdated_output="$(timeout 60 apm outdated 2>&1)" || exit 0
+outdated_output="$("$timeout_bin" -k 5 60 apm outdated 2>&1)" || exit 0
 grep -qE 'outdated dependenc(y|ies) found' <<< "$outdated_output" || exit 0
 
 stale_count="$(grep -oE '[0-9]+ outdated dependenc(y|ies) found' <<< "$outdated_output" | grep -oE '^[0-9]+' || true)"
 [[ "$stale_count" =~ ^[0-9]+$ ]] || stale_count="some"
 
-# Only ever emit fixed text plus a digit-checked count — never interpolate
-# command output into the JSON, which would need escaping this cannot do safely.
-emit() {
-  printf '{"hookSpecificOutput":{"hookEventName":"SessionStart","reloadSkills":%s,"additionalContext":"%s"}}\n' "$1" "$2"
-}
-
 # What to do with the rewritten lock depends on the branch (ADR-0019): on the
 # default branch it is a real update to commit or discard; on a feature branch it
 # is churn unrelated to the branch and should be discarded. The branch name only
@@ -85,7 +105,23 @@ if [[ -n "$current_branch" && -n "$default_branch" ]]; then
   fi
 fi
 
-if timeout 300 apm update --yes > /dev/null 2>&1; then
+# Two sessions started together would both run `apm update --yes` over the same
+# tree. Serialise on a lock under apm_modules/: `apm install` itself adds that
+# directory to .gitignore, so the lock never shows up as a working-tree change,
+# and apm only ever removes package directories inside it, never the directory
+# (or this file) itself. The loser does not wait — the winner's refresh is the
+# one it wanted — and says so. flock(1) is util-linux, absent on stock macOS,
+# and there the refresh runs unserialised, as it did before the lock existed; so
+# does a checkout with no apm_modules/ yet, rather than creating it.
+if command -v flock > /dev/null 2>&1 && [[ -d apm_modules ]] \
+  && { exec 9> apm_modules/.kyberforge-apm-update.lock; } 2> /dev/null; then
+  if ! flock -n 9; then
+    emit false "apm install is ${stale_count} package(s) behind the remote default branch, and another session is refreshing it right now, so this session skipped its own refresh. Skills and agents loaded in this session may be stale; if they are, restart the session once that refresh has finished."
+    exit 0
+  fi
+fi
+
+if "$timeout_bin" -k 5 300 apm update --yes > /dev/null 2>&1; then
   emit true "apm install was ${stale_count} package(s) behind the remote default branch and has been refreshed automatically; skills and agents were redeployed and re-scanned. apm.lock.yaml has been rewritten and is now a modified file in the working tree - ${lock_advice}"
 else
   emit false "apm install is ${stale_count} package(s) behind the remote default branch and the automatic refresh failed. Deployed skills and agents may be stale. Run: apm update --yes"
diff --git a/tests/test-apm-current-hook.sh b/tests/test-apm-current-hook.sh
index 876333a..f456baa 100755
--- a/tests/test-apm-current-hook.sh
+++ b/tests/test-apm-current-hook.sh
@@ -36,6 +36,7 @@ make_apm() {
   cat > "$FAKE_BIN/apm" << EOF
 #!/usr/bin/env bash
 pwd > "$WORK/apm-cwd"
+echo "\${GIT_TERMINAL_PROMPT-unset}" > "$WORK/gtp-\$1"
 case "\$1" in
   outdated) echo "$outdated_line"; exit 0 ;;
   update)   touch "$WORK/update-was-called"; exit $update_exit ;;
@@ -297,14 +298,147 @@ out="$(run_hook_in "$WORK" "")"; rc=$?
 
 rm -f "$WORK/update-was-called" "$WORK/apm-cwd"
 out="$(run_hook_in "$ELSEWHERE" "$ELSEWHERE")"; rc=$?
-[[ $rc -eq 0 ]] && pass "exits 0 when neither the project dir nor the cwd has a lockfile" \
-  || fail "should exit 0 when there is no lockfile anywhere"
-[[ -z "$out" ]] && pass "stays silent when neither the project dir nor the cwd has a lockfile" \
-  || fail "should stay silent when there is no lockfile anywhere"
+[[ $rc -eq 0 ]] && pass "exits 0 when the project dir has no lockfile" \
+  || fail "should exit 0 when the project dir has no lockfile"
+[[ -z "$out" ]] && pass "stays silent when the project dir has no lockfile" \
+  || fail "should stay silent when the project dir has no lockfile"
 [[ ! -f "$WORK/update-was-called" ]] \
-  && pass "does not run apm update when there is no lockfile anywhere" \
+  && pass "does not run apm update when the project dir has no lockfile" \
   || fail "must not touch a project that does not use apm"
 
+# ---------------------------------------------------------------------------
+echo ""
+echo "--- git never prompts ---"
+# ---------------------------------------------------------------------------
+
+# A remote that wants credentials must fail fast inside apm's git calls, not
+# block on a terminal prompt until the timeout fires. Cleared on the way in so
+# the assertion cannot pass on an inherited value.
+make_apm "[!] 6 outdated dependencies found" 0
+rm -f "$WORK/gtp-outdated" "$WORK/gtp-update"
+(cd "$WORK" && env -u GIT_TERMINAL_PROMPT CLAUDE_PROJECT_DIR="$WORK" PATH="$FAKE_BIN:$PATH" bash "$HOOK" > /dev/null 2>&1)
+[[ "$(cat "$WORK/gtp-outdated" 2>/dev/null)" == "0" ]] \
+  && pass "apm outdated runs with GIT_TERMINAL_PROMPT=0" \
+  || fail "apm outdated saw GIT_TERMINAL_PROMPT='$(cat "$WORK/gtp-outdated" 2>/dev/null)' — must be 0"
+[[ "$(cat "$WORK/gtp-update" 2>/dev/null)" == "0" ]] \
+  && pass "apm update runs with GIT_TERMINAL_PROMPT=0" \
+  || fail "apm update saw GIT_TERMINAL_PROMPT='$(cat "$WORK/gtp-update" 2>/dev/null)' — must be 0"
+
+# ---------------------------------------------------------------------------
+echo ""
+echo "--- timeout(1) resolution ---"
+# ---------------------------------------------------------------------------
+
+# Stock macOS has no timeout(1); Homebrew coreutils ships it as gtimeout. A PATH
+# that holds only what the hook and the mock need — and no timeout — stands in
+# for that host. bash is invoked by absolute path; `env` and `bash` are still
+# linked in because the mock's shebang resolves them through PATH.
+REAL_TIMEOUT="$(command -v timeout || true)"
+BASH_BIN="$(command -v bash)"
+SANDBOX_BIN="$(mktemp -d)"
+GT_BIN="$(mktemp -d)"
+trap 'rm -rf "$FAKE_BIN" "$WORK" "$SANDBOX_BIN" "$GT_BIN" "${PROBE:-}"' EXIT
+for tool in bash env grep touch git; do
+  src="$(command -v "$tool" || true)"
+  [[ -n "$src" ]] && ln -s "$src" "$SANDBOX_BIN/$tool"
+done
+
+make_apm "[!] 6 outdated dependencies found" 0
+rm -f "$WORK/update-was-called" "$WORK/apm-cwd"
+out="$( (cd "$WORK" && env CLAUDE_PROJECT_DIR="$WORK" PATH="$FAKE_BIN:$SANDBOX_BIN" "$BASH_BIN" "$HOOK" 2>/dev/null) )"; rc=$?
+[[ $rc -eq 0 ]] && pass "exits 0 when neither timeout nor gtimeout is on PATH" \
+  || fail "exited $rc with no timeout binary — must exit 0"
+if echo "$out" | python3 -m json.tool > /dev/null 2>&1; then
+  pass "emits valid JSON when timeout(1) is missing"
+  [[ "$(echo "$out" | json_field reloadSkills)" == "False" ]] \
+    && pass "does not ask for a skill reload when timeout(1) is missing" || fail "reloadSkills should be false"
+  grep -q "neither timeout nor gtimeout" <<< "$(json_field additionalContext <<< "$out")" \
+    && pass "says timeout(1) is missing instead of failing silently" \
+    || fail "the notice should name the missing timeout binary"
+else
+  fail "emits valid JSON when timeout(1) is missing: $out"
+fi
+[[ ! -f "$WORK/apm-cwd" ]] && pass "runs no apm command without a time limit" \
+  || fail "ran apm unbounded with no timeout binary"
+
+if [[ -n "$REAL_TIMEOUT" ]]; then
+  cat > "$GT_BIN/gtimeout" << EOF
+#!/usr/bin/env bash
+touch "$WORK/gtimeout-was-called"
+exec "$REAL_TIMEOUT" "\$@"
+EOF
+  chmod +x "$GT_BIN/gtimeout"
+
+  rm -f "$WORK/update-was-called" "$WORK/gtimeout-was-called"
+  out="$( (cd "$WORK" && env CLAUDE_PROJECT_DIR="$WORK" PATH="$FAKE_BIN:$GT_BIN:$SANDBOX_BIN" "$BASH_BIN" "$HOOK" 2>/dev/null) )"
+  [[ -f "$WORK/gtimeout-was-called" ]] && pass "falls back to gtimeout when timeout is absent" \
+    || fail "should use gtimeout when timeout is not on PATH"
+  [[ -f "$WORK/update-was-called" && "$(echo "$out" | json_field reloadSkills 2>/dev/null)" == "True" ]] \
+    && pass "refreshes normally through gtimeout" || fail "the gtimeout path should refresh and reload: $out"
+
+  rm -f "$WORK/gtimeout-was-called"
+  (cd "$WORK" && env CLAUDE_PROJECT_DIR="$WORK" PATH="$FAKE_BIN:$GT_BIN:$(dirname "$REAL_TIMEOUT"):$SANDBOX_BIN" "$BASH_BIN" "$HOOK" > /dev/null 2>&1)
+  [[ ! -f "$WORK/gtimeout-was-called" ]] && pass "prefers timeout over gtimeout when both exist" \
+    || fail "used gtimeout although timeout is on PATH"
+else
+  echo "  (timeout not on PATH — gtimeout fallback cases not run)"
+fi
+
+# ---------------------------------------------------------------------------
+echo ""
+echo "--- concurrent sessions do not both update ---"
+# ---------------------------------------------------------------------------
+
+if command -v flock > /dev/null 2>&1; then
+  LOCK_PROJECT="$WORK/lock-project"
+  mkdir -p "$LOCK_PROJECT/apm_modules"
+  touch "$LOCK_PROJECT/apm.lock.yaml"
+  LOCKFILE="$LOCK_PROJECT/apm_modules/.kyberforge-apm-update.lock"
+  make_apm "[!] 6 outdated dependencies found" 0
+
+  # Lock free: the refresh runs and the lock lands under the gitignored
+  # apm_modules/, never in the project root where git would see it.
+  rm -f "$WORK/update-was-called"
+  out="$(run_hook_in "$LOCK_PROJECT" "$LOCK_PROJECT")"
+  [[ -f "$WORK/update-was-called" ]] && pass "updates when the lock is free" \
+    || fail "should update when no other session holds the lock"
+  [[ -f "$LOCKFILE" ]] && pass "takes its lock under apm_modules/" \
+    || fail "expected the lock at apm_modules/.kyberforge-apm-update.lock"
+
+  # Lock held by another session: this one must not update, must still exit 0
+  # with valid JSON, and must say why nothing was refreshed.
+  exec 8> "$LOCKFILE"
+  flock 8
+  rm -f "$WORK/update-was-called"
+  out="$(run_hook_in "$LOCK_PROJECT" "$LOCK_PROJECT" 8>&-)"; rc=$?
+  exec 8>&-
+  [[ $rc -eq 0 ]] && pass "exits 0 when another session holds the update lock" \
+    || fail "exited $rc with the lock held — must exit 0"
+  [[ ! -f "$WORK/update-was-called" ]] && pass "skips apm update when another session holds the lock" \
+    || fail "ran apm update while another session held the lock"
+  if echo "$out" | python3 -m json.tool > /dev/null 2>&1; then
+    [[ "$(echo "$out" | json_field reloadSkills)" == "False" ]] \
+      && pass "does not ask for a skill reload when it skipped the refresh" || fail "reloadSkills should be false"
+    grep -q "another session is refreshing it" <<< "$(json_field additionalContext <<< "$out")" \
+      && pass "says another session is refreshing" || fail "the notice should say another session holds the refresh"
+  else
+    fail "emits valid JSON when the lock is held: $out"
+  fi
+
+  # No apm_modules/ yet (fresh clone before install): proceed unserialised
+  # rather than create the directory.
+  NO_MODULES="$WORK/no-modules"
+  mkdir -p "$NO_MODULES"
+  touch "$NO_MODULES/apm.lock.yaml"
+  rm -f "$WORK/update-was-called"
+  run_hook_in "$NO_MODULES" "$NO_MODULES" > /dev/null
+  [[ -f "$WORK/update-was-called" && ! -e "$NO_MODULES/apm_modules" ]] \
+    && pass "without apm_modules/, updates unserialised and creates nothing" \
+    || fail "without apm_modules/ the hook should update and not create the directory"
+else
+  echo "  (flock not on PATH — lock cases not run)"
+fi
+
 # ---------------------------------------------------------------------------
 echo ""
 echo "--- hooks.json wiring ---"
@@ -333,15 +467,27 @@ matcher="$(python3 -c 'import json,sys; d=json.load(open(sys.argv[1])); print(d[
 # literal, so raising either internal `timeout` without raising the host budget
 # fails here instead of reintroducing the gap quietly.
 #
-# Every `timeout N` in the script counts, comments included: a stray "timeout
-# 300" in prose only makes this stricter, which is the safe direction.
+# Both spellings count, comments included: `-k K N` (the binary is resolved at
+# run time, so the call reads `"$timeout_bin" -k 5 60 …`) contributes the limit N
+# plus the kill-after grace K, since SIGKILL lands only K seconds after N; a
+# bare `timeout N` contributes N. A stray match in prose only makes this
+# stricter, which is the safe direction.
 script_budget=0
 timeout_count=0
-while read -r n; do
-  [[ -n "$n" ]] || continue
-  script_budget=$((script_budget + n))
+while read -r k n; do
+  [[ -n "$k" ]] || continue
+  script_budget=$((script_budget + k + ${n:-0}))
   timeout_count=$((timeout_count + 1))
-done < <(grep -oE '\btimeout [0-9]+\b' "$HOOK" | grep -oE '[0-9]+')
+done < <(
+  grep -oE -- '-k [0-9]+ [0-9]+\b' "$HOOK" | grep -oE '[0-9]+ [0-9]+' || true
+  grep -oE '\btimeout [0-9]+\b' "$HOOK" | grep -oE '[0-9]+' || true
+)
+
+# Without -k a child that ignores SIGTERM outlives its limit and the budget
+# above is fiction. Every time-boxed call must carry the grace.
+unkilled="$(grep -E '"\$timeout_bin" ' "$HOOK" | grep -vE -- '-k [0-9]+ [0-9]+' || true)"
+[[ -z "$unkilled" ]] && pass "every time-boxed apm call carries a -k kill-after grace" \
+  || fail "a time-boxed call has no -k grace: $unkilled"
 
 hook_timeout="$(python3 -c 'import json,sys; d=json.load(open(sys.argv[1])); print(d["hooks"]["SessionStart"][0]["hooks"][0]["timeout"])' "$HOOKS_JSON")"
 
@@ -381,7 +527,7 @@ if ! command -v apm > /dev/null 2>&1 || ! command -v git > /dev/null 2>&1; then
   echo "  $SKIP_REASON"
 else
   PROBE="$(mktemp -d)"
-  trap 'rm -rf "$FAKE_BIN" "$WORK" "$PROBE"' EXIT
+  trap 'rm -rf "$FAKE_BIN" "$WORK" "$SANDBOX_BIN" "$GT_BIN" "$PROBE"' EXIT
 
   UPSTREAM="$PROBE/upstream.git"
   git init -q "$UPSTREAM"