#!/usr/bin/env bash
# test-wake-store-ack.sh — RED-FIRST invariant harness for W2 (EPIC #892):
# three-cursor durable store (store.sh, A2) + RECEIVED/CONSUMED ack-wrapper
# (ack.sh, A4).
#
# Each test asserts ONE CONVERGED-DESIGN invariant and is designed to go RED if
# that invariant regresses:
#   T1 three-cursor advancement                    (§1.2/§2.4)
#   T2 digest-coalesce-REPLACE vs actionable-APPEND (§1.2/§2.3)
#   T3 contiguous-prefix CONSUMED / gap rejection   (§1.2/§2.2)
#   T4 wake_id DELIVERY-dedup (never re-action)      (§2.2)
#   T5 atomic write-tmp+rename survives crash mid-write (§1.2)
#   T6 durability survives restart (retain until CONSUMED) (§2.3)
#   T7 ack local-write NEVER blocks on network       (§2.2)
#   T8 SOLE store-side allocator: enqueue (no --seq) allocates contiguous
#      observed_seq + anti-swallow fail-loud on explicit seq<=consumed (#908)
#   T9 burn-before-enqueue: a failed durable write must NOT advance the
#      observed_seq cursor (no burned seq / no interior gap)          (#908 arrow 1)
#   T10 concurrency: two concurrent enqueues get DISTINCT seqs (lock)  (#908)
#
# Isolated: every test runs against a fresh WAKE_STATE_HOME temp dir.
set -uo pipefail

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
STORE="$SCRIPT_DIR/store.sh"
ACK="$SCRIPT_DIR/ack.sh"

command -v jq >/dev/null 2>&1 || {
  echo "SKIP: jq not available" >&2
  exit 0
}

TMP_ROOT="$(mktemp -d)"
trap 'rm -rf "$TMP_ROOT"' EXIT

# Failures are recorded to a marker FILE, not a shell var: each test runs in a
# subshell (for env isolation) and a subshell cannot mutate a parent variable,
# so a var-based counter would silently swallow failures (the exact bug this
# harness must never have).
FAILFILE="$TMP_ROOT/failures"
: >"$FAILFILE"
pass=0
fail_msg() {
  echo "  FAIL: $*" >&2
  echo "x" >>"$FAILFILE"
}
ok() { pass=$((pass + 1)); }

# jq_any FILE FILTER — true iff any JSONL record in FILE matches FILTER. Uses
# slurp (-s), NOT `jq -e select` (which reflects only the LAST input's value
# over a multi-line JSONL and would misreport presence).
jq_any() {
  local file="$1" filter="$2"
  [ -f "$file" ] || return 1
  [ "$(jq -s "[.[] | select($filter)] | length" "$file" 2>/dev/null || echo 0)" -gt 0 ]
}
# stream_any — same, but reads JSONL from stdin.
stream_any() {
  local filter="$1"
  [ "$(jq -s "[.[] | select($filter)] | length" 2>/dev/null || echo 0)" -gt 0 ]
}

# fresh_state NAME — echoes a fresh isolated state home for export.
fresh_state() {
  local d="$TMP_ROOT/$1"
  rm -rf "$d"
  mkdir -p "$d"
  printf '%s' "$d"
}

echo "== T1: three-cursor advancement =="
(
  WAKE_STATE_HOME="$(fresh_state t1)"
  export WAKE_STATE_HOME
  unset WAKE_AGENT
  "$STORE" enqueue --seq 1 --class actionable --locators '{"repo":"r","issue":1}' >/dev/null
  "$STORE" enqueue --seq 2 --class actionable --locators '{"repo":"r","issue":2}' >/dev/null
  cur="$("$STORE" cursors)"
  echo "$cur" | grep -q 'observed_seq=2' || fail_msg "T1: observed_seq should be 2 after enqueue 1,2 [$cur]"
  echo "$cur" | grep -q 'consumed_seq=0' || fail_msg "T1: consumed_seq must NOT advance on enqueue (only on CONSUMED ack) [$cur]"
  echo "$cur" | grep -q 'pending_depth=2' || fail_msg "T1: pending depth should be 2 [$cur]"
  # consumed_seq advances only on CONSUMED.
  "$STORE" consume --upto 2 >/dev/null
  cur="$("$STORE" cursors)"
  echo "$cur" | grep -q 'consumed_seq=2' || fail_msg "T1: consumed_seq should be 2 after CONSUMED 2 [$cur]"
  echo "$cur" | grep -q 'pending_depth=0' || fail_msg "T1: pending drained after CONSUMED [$cur]"
) && ok

echo "== T2: digest coalesce-REPLACE vs actionable APPEND =="
(
  WAKE_STATE_HOME="$(fresh_state t2)"
  export WAKE_STATE_HOME
  unset WAKE_AGENT
  "$STORE" enqueue --seq 1 --class digest --locators '{"head":"aaa"}' >/dev/null
  "$STORE" enqueue --seq 2 --class actionable --locators '{"issue":7}' >/dev/null
  "$STORE" enqueue --seq 3 --class digest --locators '{"head":"bbb"}' >/dev/null
  "$STORE" enqueue --seq 4 --class human --locators '{"from":"peer"}' >/dev/null
  out="$("$STORE" drain)"
  ndigest="$(printf '%s\n' "$out" | jq -c 'select(.class=="digest")' | grep -c . || true)"
  [ "$ndigest" = "1" ] || fail_msg "T2: digest must COALESCE to a single pending entry, got $ndigest"
  head="$(printf '%s\n' "$out" | jq -r 'select(.class=="digest") | .locators.head')"
  [ "$head" = "bbb" ] || fail_msg "T2: newest digest must REPLACE prior (expected bbb, got $head)"
  nactionable="$(printf '%s\n' "$out" | jq -c 'select(.class=="actionable")' | grep -c . || true)"
  nhuman="$(printf '%s\n' "$out" | jq -c 'select(.class=="human")' | grep -c . || true)"
  [ "$nactionable" = "1" ] || fail_msg "T2: actionable must APPEND (never replaced), got $nactionable"
  [ "$nhuman" = "1" ] || fail_msg "T2: human must APPEND / stay durable, got $nhuman"
  # Durability never bypassed: all classes present in the durable store.
  total="$(printf '%s\n' "$out" | grep -c . || true)"
  [ "$total" = "3" ] || fail_msg "T2: durable store should hold digest+actionable+human = 3, got $total"
) && ok

echo "== T3: contiguous-prefix CONSUMED (reject ack N while N-1 unconsumed) =="
(
  WAKE_STATE_HOME="$(fresh_state t3)"
  export WAKE_STATE_HOME
  unset WAKE_AGENT
  # Gap: observe seq 1 and 3, but NOT 2.
  "$STORE" enqueue --seq 1 --class actionable --locators '{}' >/dev/null
  "$STORE" enqueue --seq 3 --class actionable --locators '{}' >/dev/null
  if "$STORE" consume --upto 3 >/dev/null 2>&1; then
    fail_msg "T3: CONSUMED 3 must be REJECTED while seq 2 is a gap (unconsumed)"
  fi
  cur="$("$STORE" cursors)"
  echo "$cur" | grep -q 'consumed_seq=0' || fail_msg "T3: rejected CONSUMED must NOT advance the cursor [$cur]"
  # Also reject via the ack wrapper.
  if "$ACK" consumed --upto 3 --no-sync >/dev/null 2>&1; then
    fail_msg "T3: ack.sh CONSUMED 3 must be REJECTED over a gap"
  fi
  # Fill the gap; now the contiguous prefix is ackable.
  "$STORE" enqueue --seq 2 --class actionable --locators '{}' >/dev/null
  "$ACK" consumed --upto 3 --no-sync >/dev/null 2>&1 || fail_msg "T3: CONSUMED 3 should succeed once gap at 2 is filled"
  cur="$("$STORE" cursors)"
  echo "$cur" | grep -q 'consumed_seq=3' || fail_msg "T3: consumed_seq should be 3 after contiguous prefix filled [$cur]"
  # Cumulative + can't regress: CONSUMED 2 after 3 is an idempotent no-op.
  "$ACK" consumed --upto 2 --no-sync >/dev/null 2>&1 || fail_msg "T3: cumulative CONSUMED 2 (<=3) should be an idempotent success"
  cur="$("$STORE" cursors)"
  echo "$cur" | grep -q 'consumed_seq=3' || fail_msg "T3: cursor must not regress below 3 [$cur]"
) && ok

echo "== T4: wake_id DELIVERY-dedup (dup delivery = re-RECEIVE, never re-action) =="
(
  WAKE_STATE_HOME="$(fresh_state t4)"
  export WAKE_STATE_HOME
  unset WAKE_AGENT
  "$STORE" enqueue --seq 1 --class digest --locators '{}' >/dev/null
  r1="$("$ACK" received --wake-id WID-abc)"
  [ "$r1" = "RECEIVED" ] || fail_msg "T4: first delivery should be RECEIVED, got '$r1'"
  r2="$("$ACK" received --wake-id WID-abc)"
  [ "$r2" = "DUP" ] || fail_msg "T4: duplicate delivery of same wake_id should be DUP (re-RECEIVE), got '$r2'"
  # RECEIVED (delivery) must NEVER advance consumed_seq (delivery != consumption).
  cur="$("$STORE" cursors)"
  echo "$cur" | grep -q 'consumed_seq=0' || fail_msg "T4: RECEIVED must not advance consumed_seq [$cur]"
) && ok

echo "== T5: atomic write-tmp+rename survives crash mid-write =="
(
  WAKE_STATE_HOME="$(fresh_state t5)"
  export WAKE_STATE_HOME
  unset WAKE_AGENT
  "$STORE" enqueue --seq 1 --class actionable --locators '{"issue":1}' >/dev/null
  STATE_DIR="$WAKE_STATE_HOME/default"
  before="$(cat "$STATE_DIR/pending.jsonl")"
  # Simulate a crash mid-write: a leftover atomic-write temp file with GARBAGE
  # that was never renamed over the live file.
  printf '{"observed_seq": 999, TRUNCATED-GARBAGE' >"$STATE_DIR/.wake.tmp.crash12"
  # The live store must be untouched and still valid JSON.
  after="$(cat "$STATE_DIR/pending.jsonl")"
  [ "$before" = "$after" ] || fail_msg "T5: live pending.jsonl changed by a crash temp file"
  drained="$("$STORE" drain)"
  printf '%s\n' "$drained" | jq -e . >/dev/null 2>&1 || fail_msg "T5: drain returned non-JSON — garbage temp corrupted the store"
  printf '%s\n' "$drained" | stream_any '.observed_seq==1' || fail_msg "T5: committed entry (seq 1) lost after simulated crash"
  printf '%s\n' "$drained" | grep -q 999 && fail_msg "T5: uncommitted garbage (seq 999) leaked into the live store"
  # A subsequent real mutation must succeed and clean the stale temp.
  "$STORE" enqueue --seq 2 --class actionable --locators '{"issue":2}' >/dev/null || fail_msg "T5: enqueue after crash temp failed"
  [ -e "$STATE_DIR/.wake.tmp.crash12" ] && fail_msg "T5: stale crash temp not cleaned by next mutation"
  d2="$("$STORE" drain)"
  [ "$(printf '%s\n' "$d2" | grep -c .)" = "2" ] || fail_msg "T5: store not healthy after crash+recovery (expected 2 entries)"
) && ok

echo "== T5b: _atomic_write is tmp+rename (killing the writer mid-write leaves the target intact) =="
(
  WAKE_STATE_HOME="$(fresh_state t5b)"
  export WAKE_STATE_HOME
  unset WAKE_AGENT
  # shellcheck disable=SC1091
  . "$SCRIPT_DIR/_wake-common.sh"
  d="$WAKE_STATE_HOME/atomic"
  mkdir -p "$d"
  target="$d/file"
  printf 'GOOD\n' | _atomic_write "$target"
  # Feed a writer via a FIFO but NEVER send EOF, then kill it mid-write. With
  # true tmp+rename the partial bytes land in a temp file and the rename never
  # runs, so `target` keeps its committed content. A direct (non-atomic) write
  # would have streamed the garbage straight into `target`.
  fifo="$d/fifo"
  mkfifo "$fifo"
  ( _atomic_write "$target" <"$fifo" ) &
  wpid=$!
  exec 9>"$fifo"
  printf 'PARTIAL-GARBAGE-NO-EOF' >&9
  sleep 0.3
  pkill -9 -P "$wpid" 2>/dev/null || true
  kill -9 "$wpid" 2>/dev/null || true
  exec 9>&-
  wait "$wpid" 2>/dev/null || true
  got="$(cat "$target" 2>/dev/null)"
  [ "$got" = "GOOD" ] || fail_msg "T5b: target corrupted by a killed mid-write (got '$got') — write is not tmp+rename atomic"
) && ok

echo "== T6: durability survives restart (retain until CONSUMED) =="
(
  WAKE_STATE_HOME="$(fresh_state t6)"
  export WAKE_STATE_HOME
  unset WAKE_AGENT
  # "Session 1": enqueue then vanish (no in-memory state carried).
  "$STORE" enqueue --seq 1 --class human --locators '{"from":"peer"}' >/dev/null
  "$STORE" enqueue --seq 2 --class actionable --locators '{"issue":9}' >/dev/null
  # "Session 2": a brand-new process (this subshell invocation of store.sh) must
  # see the persisted entries — nothing was held in memory.
  d="$("$STORE" drain)"
  [ "$(printf '%s\n' "$d" | grep -c .)" = "2" ] || fail_msg "T6: entries not retained across restart (expected 2)"
  printf '%s\n' "$d" | stream_any '.class=="human"' || fail_msg "T6: a human message was lost across restart (durability bypassed)"
  # Retained UNTIL consumed: after CONSUMED they are released.
  "$STORE" consume --upto 2 >/dev/null
  d2="$("$STORE" drain)"
  n2="$(printf '%s\n' "$d2" | grep -c . || true)"
  [ "$n2" = "0" ] || fail_msg "T6: entries should be released only AFTER CONSUMED (still $n2 pending)"
) && ok

echo "== T7: ack local-write NEVER blocks on network =="
(
  WAKE_STATE_HOME="$(fresh_state t7)"
  export WAKE_STATE_HOME
  unset WAKE_AGENT
  "$STORE" enqueue --seq 1 --class digest --locators '{}' >/dev/null
  # A network-shaped shim on PATH: if the SYNCHRONOUS ack path ever invoked the
  # network directly, this marker would appear before ack returns.
  bin="$TMP_ROOT/t7bin"
  mkdir -p "$bin"
  for netcmd in curl wget nc ssh; do
    cat >"$bin/$netcmd" <<EOF
#!/usr/bin/env bash
touch "$WAKE_STATE_HOME/NET_CALLED_SYNC"
exit 0
EOF
    chmod +x "$bin/$netcmd"
  done
  # Background sync deliberately SLOW: proves the ack does not wait for it.
  export WAKE_ACK_SYNC_CMD="sleep 3; touch '$WAKE_STATE_HOME/SYNC_DONE'"
  # Sub-second timing (#918): `date +%s` is SECOND-granularity, so a
  # legitimately fast (sub-second) ack that straddles a wall-clock second
  # boundary can misreport elapsed=2s and flake under CI load (observed on
  # Woodpecker pipeline 2057; 20/20 passes locally elsewhere). Use
  # `date +%s.%N` and compare in milliseconds via awk (bash `[ ]` can't do
  # float/ms math) against a threshold comfortably below the 3s background
  # sync — proving the ack did NOT wait on it — while tolerating a
  # legitimate sub-second-to-~1s ack across a boundary.
  start="$(date +%s.%N)"
  out="$(PATH="$bin:$PATH" "$ACK" consumed --upto 1 --wake-id WID-1)"
  end="$(date +%s.%N)"
  elapsed_ms="$(awk -v s="$start" -v e="$end" 'BEGIN { printf "%d", (e - s) * 1000 }')"
  [ "$elapsed_ms" -lt 1500 ] || fail_msg "T7: ack path blocked ${elapsed_ms}ms — must return without waiting on the background sync"
  echo "$out" | grep -q 'CONSUMED 1' || fail_msg "T7: CONSUMED not reported [$out]"
  # Local write is durable IMMEDIATELY (no network needed to record the ack).
  STATE_DIR="$WAKE_STATE_HOME/default"
  jq_any "$STATE_DIR/ack-ledger.jsonl" '.type=="CONSUMED" and .upto==1' ||
    fail_msg "T7: CONSUMED not written to the local ledger synchronously"
  consumed_now="$("$STORE" cursors | sed -n 's/consumed_seq=//p')"
  [ "$consumed_now" = "1" ] || fail_msg "T7: consumed_seq not advanced by the local ack write (got '$consumed_now')"
  # The synchronous path must NOT have touched the network.
  [ -e "$WAKE_STATE_HOME/NET_CALLED_SYNC" ] && fail_msg "T7: a network command was invoked on the SYNCHRONOUS ack path"
  # And the slow sync must still be in flight (proves it was truly backgrounded).
  [ -e "$WAKE_STATE_HOME/SYNC_DONE" ] && fail_msg "T7: background sync finished synchronously — it was not detached"
  true
) && ok

echo "== T8: SOLE store-side allocator — enqueue (no --seq) allocates contiguous seqs + anti-swallow fail-loud (#908) =="
(
  WAKE_STATE_HOME="$(fresh_state t8)"
  export WAKE_STATE_HOME
  unset WAKE_AGENT
  # No --seq: the STORE allocates and PRINTS the assigned observed_seq.
  s1="$("$STORE" enqueue --class actionable --locators '{"n":1}')"
  s2="$("$STORE" enqueue --class actionable --locators '{"n":2}')"
  [ "$s1" = "1" ] || fail_msg "T8: first store-allocated observed_seq must be 1, got '$s1'"
  [ "$s2" = "2" ] || fail_msg "T8: second store-allocated observed_seq must be 2 (contiguous), got '$s2'"
  cur="$("$STORE" cursors)"
  echo "$cur" | grep -q 'observed_seq=2' || fail_msg "T8: observed_seq cursor should be 2 [$cur]"
  echo "$cur" | grep -q 'pending_depth=2' || fail_msg "T8: both allocations must be durably enqueued [$cur]"
  # ANTI-SWALLOW: consume the prefix, then a LEGACY explicit --seq inside the
  # consumed prefix must FAIL LOUD (never the old silent seq<=consumed no-op).
  "$STORE" consume --upto 2 >/dev/null
  before_depth="$("$STORE" cursors | sed -n 's/pending_depth=//p')"
  if "$STORE" enqueue --seq 1 --class actionable --locators '{}' >/dev/null 2>&1; then
    fail_msg "T8: explicit --seq 1 <= consumed_seq 2 must FAIL LOUD (anti-swallow), not be a silent no-op"
  fi
  err="$("$STORE" enqueue --seq 1 --class actionable --locators '{}' 2>&1 || true)"
  echo "$err" | grep -qi 'anti-swallow' || fail_msg "T8: the refusal must name the anti-swallow guarantee [$err]"
  after_depth="$("$STORE" cursors | sed -n 's/pending_depth=//p')"
  [ "$before_depth" = "$after_depth" ] || fail_msg "T8: a refused enqueue must not mutate the store (depth $before_depth->$after_depth)"
  # And the NEXT real allocation is > consumed (2) — never inside the prefix.
  s3="$("$STORE" enqueue --class actionable --locators '{"n":3}')"
  [ "$s3" = "3" ] || fail_msg "T8: post-consume allocation must be 3 (>consumed 2), got '$s3'"
) && ok

echo "== T9: burn-before-enqueue — a failed durable write must NOT advance observed_seq (no burned seq / no gap) (#908 arrow 1) =="
(
  WAKE_STATE_HOME="$(fresh_state t9)"
  export WAKE_STATE_HOME
  unset WAKE_AGENT
  STATE_DIR="$WAKE_STATE_HOME/default"
  # One successful allocation: observed_seq=1, and the enqueue lock now exists.
  s1="$("$STORE" enqueue --class actionable --locators '{"n":1}')"
  [ "$s1" = "1" ] || fail_msg "T9: baseline allocation should be 1, got '$s1'"
  obs_before="$("$STORE" cursors | sed -n 's/^observed_seq=//p')"
  [ "$obs_before" = "1" ] || fail_msg "T9: observed_seq should be 1 before the forced failure, got '$obs_before'"
  # Force the durable PENDING write to FAIL via a PRIVILEGE-INVARIANT trigger:
  # bind-mount a throwaway file OVER $STATE_DIR/pending.jsonl (_atomic_write's
  # exact rename TARGET for the durable write — see _wake-common.sh) so the
  # atomic write's `mv -f tmp target` hits EBUSY ("Device or resource busy"):
  # the kernel refuses to rename ANY file onto an ACTIVE MOUNT POINT. That is
  # a structural VFS constraint, not a DAC permission check — root does NOT
  # bypass it (no uid can rename over a live mountpoint short of an explicit
  # umount first). This replaces the old `chmod 500 "$STATE_DIR"` injection: a
  # CI container running as root BYPASSES DAC checks entirely, so the
  # "read-only" dir let mktemp/the write through and every assertion below
  # went spuriously green. The old chmod also blocked the CURSOR's own
  # mktemp (same dir), so it could never have caught a premature cursor
  # commit either — narrower coverage than its comment claimed. Here
  # observed_seq is left an ordinary writable file, never touched by the
  # mount, so a regression that commits the cursor before/independent of the
  # durable write is still genuinely caught by the assertions below.
  #
  # The mount + forced enqueue run inside a private mount+user namespace
  # (`unshare --mount --user --map-root-user`) so the mechanism is IDENTICAL
  # whether this harness runs unprivileged (dev) or as root (CI): creating a
  # user namespace needs no pre-existing privilege, and the busy-mountpoint
  # rule inside it is the real kernel rule, unaffected by uid in or out of a
  # namespace. The bind mount is entirely private to that namespace and
  # vanishes the instant it exits, so $STATE_DIR/pending.jsonl is a plain
  # writable file again for every assertion below — no manual cleanup step.
  rc=0
  if ! command -v unshare >/dev/null 2>&1; then
    fail_msg "T9: 'unshare' unavailable — cannot construct the privilege-invariant fault injection in this sandbox"
    rc=99
  else
    ro_src="$TMP_ROOT/t9-ro-src"
    mkdir -p "$ro_src"
    : >"$ro_src/pending.jsonl"
    # shellcheck disable=SC2016 # deliberate: $1/$2/$3 expand in the NESTED
    # bash (inside the unshare'd namespace), not this outer single-quoted one.
    unshare --mount --user --map-root-user bash -c '
      set -u
      ro_src="$1"
      state_dir="$2"
      store="$3"
      if ! mount --bind "$ro_src/pending.jsonl" "$state_dir/pending.jsonl" 2>/dev/null; then
        exit 98
      fi
      mount -o remount,ro,bind "$state_dir/pending.jsonl" 2>/dev/null || true
      "$store" enqueue --class actionable --locators "{\"n\":2}" >/dev/null 2>&1
    ' _ "$ro_src" "$STATE_DIR" "$STORE"
    rc=$?
    if [ "$rc" -eq 98 ]; then
      fail_msg "T9: could not bind-mount over pending.jsonl (mount unavailable in this sandbox) — fault injection not constructed"
    fi
  fi
  [ "$rc" -ne 0 ] || fail_msg "T9: an enqueue whose durable write fails must EXIT NON-ZERO (fail loud)"
  # THE ARROW-#1 ASSERTION: the observed_seq cursor did NOT advance — no seq was
  # burned by a write that never reached the store. (RED if the cursor bumps
  # before/independent of the durable write.)
  obs_after="$("$STORE" cursors | sed -n 's/^observed_seq=//p')"
  [ "$obs_after" = "1" ] || fail_msg "T9: a failed enqueue must NOT advance observed_seq (burned seq -> permanent gap), got '$obs_after'"
  # No interior gap was created: CONSUMED 1 (the only real obligation) still holds.
  "$STORE" consume --upto 1 >/dev/null 2>&1 || fail_msg "T9: CONSUMED 1 must remain valid — no burned-seq gap"
  # And a fresh allocation resumes cleanly at 2 (not 3 — nothing was burned).
  s="$("$STORE" enqueue --class actionable --locators '{"n":"2b"}')"
  [ "$s" = "2" ] || fail_msg "T9: post-failure allocation must resume at 2 (no burned seq), got '$s'"
) && ok

echo "== T10: concurrency — two concurrent enqueues get DISTINCT seqs (enqueue lock) (#908) =="
if command -v flock >/dev/null 2>&1; then
  (
    WAKE_STATE_HOME="$(fresh_state t10)"
    export WAKE_STATE_HOME
    unset WAKE_AGENT
    "$STORE" init >/dev/null 2>&1 || true
    o1="$TMP_ROOT/t10.o1"
    o2="$TMP_ROOT/t10.o2"
    # Two enqueues racing on the SAME store. Without the lock both read
    # observed_seq=0 and allocate 1 (aliasing + a lost write); the lock serializes
    # the allocate+write so they get 1 and 2.
    "$STORE" enqueue --class actionable --locators '{"c":1}' >"$o1" 2>/dev/null &
    p1=$!
    "$STORE" enqueue --class actionable --locators '{"c":2}' >"$o2" 2>/dev/null &
    p2=$!
    wait "$p1"; wait "$p2"
    a="$(tr -d '[:space:]' <"$o1")"
    b="$(tr -d '[:space:]' <"$o2")"
    [ -n "$a" ] && [ -n "$b" ] || fail_msg "T10: both concurrent enqueues must print an allocated seq (got '$a','$b')"
    [ "$a" != "$b" ] || fail_msg "T10: two concurrent enqueues must get DISTINCT seqs, both got '$a' (aliasing / lost write without the lock)"
    cur="$("$STORE" cursors)"
    echo "$cur" | grep -q 'observed_seq=2' || fail_msg "T10: observed_seq must reach 2 after two enqueues [$cur]"
    echo "$cur" | grep -q 'pending_depth=2' || fail_msg "T10: both entries must be durably stored (no lost write) [$cur]"
    # The two allocated seqs are exactly {1,2} (distinct, contiguous, gapless).
    lo="$a"; hi="$b"; [ "$a" -gt "$b" ] && { lo="$b"; hi="$a"; }
    { [ "$lo" = "1" ] && [ "$hi" = "2" ]; } || fail_msg "T10: concurrent seqs must be {1,2}, got {$lo,$hi}"
  ) && ok
else
  echo "  SKIP: flock not available (concurrency guarantee needs flock; matches detector single-instance SKIP)"
  ok
fi

echo
if [ -s "$FAILFILE" ]; then
  echo "wake store/ack harness: FAILED ($(grep -c . "$FAILFILE") assertion(s))" >&2
  exit 1
fi
echo "wake store/ack harness: all invariants passed ($pass groups)"