fix(reset): fence every job registry the reset reads, by its physical directory (#78)

Review round 3 R1 (codex): the registration guard chose the workspace marker
from the path's spelling, so a symlink alias of .mam/jobs or a MAM_JOBS_DIR
registry was not refused. The reset now writes .reset-in-progress into each
registry its open-job check reads (.mam/jobs, MAM_JOBS_DIR, a row's other
control_plane.mam_jobs_dir - the latter only for this workspace's sessions),
each under that registry's lock and before the check, and removes it on exit;
register_job reads the marker inside the registry it writes to. The
precheck's separate lock barrier is subsumed by the fence.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.agents/skills/lib_py/delegation/registry.py

@@ -68,12 +68,16 @@ def liveness_window(heartbeat_sec: int, heartbeat_misses: int) -> int:
 
 
 # Issue #78: a reset of a workspace purges its agents' conversations, so no job
-# may be registered in that workspace's .mam/jobs while one runs. The reset
+# may be registered for them while it runs. The reset writes RESET_MARKER into
-# publishes .mam/reset-in-progress (pid/lstart, loop_lock.sh's format) and then
+# every registry its open-job check reads (its own .mam/jobs and MAM_JOBS_DIR,
-# takes this registry's lock once before it lists the open jobs; the marker is
+# and a row's other control_plane.mam_jobs_dir), each under that registry's
-# read under the same lock here, so a registration either is written before
+# lock and before the check: a registration reads it under the same lock, so it
-# that listing or sees the marker. The reset's own create (the onboarding job
+# is either written before the check or refused - by whatever path it names
-# of an agent it recreates) passes the reset's pid in MAM_RESET_OWNER_PID.
+# the directory. The marker carries the reset's pid/lstart (loop_lock.sh's
+# format), its workspace, and for another control plane's registry the
+# sessions it covers. The reset's own create (the onboarding job of an agent
+# it recreates) passes the reset's pid in MAM_RESET_OWNER_PID.
+RESET_MARKER = ".reset-in-progress"
 RESET_OWNER_ENV = "MAM_RESET_OWNER_PID"
 
 
@@ -90,15 +94,13 @@ def _lstart(pid: str) -> str:
     return " ".join(out.split())
 
 
-def reset_refusal(registry_dir: str) -> Optional[str]:
+def reset_refusal(registry_dir: str, agent_session: str) -> Optional[str]:
-    """Why a registration in ``registry_dir`` is refused, or None: a live
+    """Why registering a job for ``agent_session`` in ``registry_dir`` is
-    reset of the workspace that owns it (``<ws>/.mam/jobs``) that is not the
+    refused, or None: a live reset fenced this registry (for that session) and
-    caller's own. Holder states as loop_lock.sh decides them: a dead or
+    the caller is not its own create. Holder states as loop_lock.sh decides
-    reused pid is stale; ps failing on this process is unknown (refused)."""
+    them: a dead or reused pid is stale; ps failing on this process is unknown
-    jobs = os.path.abspath(registry_dir)
+    (refused)."""
-    if os.path.basename(jobs) != "jobs" or os.path.basename(os.path.dirname(jobs)) != ".mam":
+    marker = os.path.join(registry_dir, RESET_MARKER)
-        return None
-    marker = os.path.join(os.path.dirname(jobs), "reset-in-progress")
     try:
         with open(marker, encoding="utf-8") as fh:
             fields = dict(line.split("=", 1) for line in fh.read().splitlines() if "=" in line)
@@ -106,6 +108,8 @@ def reset_refusal(registry_dir: str) -> Optional[str]:
         return None
     except (OSError, ValueError) as exc:
         return "the reset marker %s cannot be read (%s)" % (marker, exc)
+    if "sessions" in fields and agent_session not in fields["sessions"].split(","):
+        return None
     pid = fields.get("pid", "")
     if not pid.isdigit() or os.environ.get(RESET_OWNER_ENV) == pid:
         return None
@@ -115,7 +119,7 @@ def reset_refusal(registry_dir: str) -> Optional[str]:
     if not cur or (fields.get("lstart") and cur != fields["lstart"]):
         return None
     return ("a reset of %s is in progress (pid %s); its agents are being purged and recreated;"
-            " register the job when it has finished" % (os.path.dirname(os.path.dirname(jobs)), pid))
+            " register the job when it has finished" % (fields.get("workspace", "?"), pid))
 
 
 def register_job(
@@ -213,7 +217,7 @@ def register_job(
     if dry_run:
         record["dry_run"] = True
     with registry_lock(registry_dir):
-        refusal = reset_refusal(registry_dir)
+        refusal = reset_refusal(registry_dir, agent_session)
         if refusal:
             raise ResetInProgressError(refusal)
         if mqtt_common._job_path(job_id, registry_dir).exists():

.agents/skills/lib_py/reset.py

@@ -18,11 +18,12 @@ import sqlite3
 import subprocess
 import sys
 import tempfile
-from typing import Dict, List, Mapping, Optional, Tuple
+from typing import Dict, Iterator, List, Mapping, Optional, Tuple
 
 from lib_py.agents.base import AGENT_SESSION_ENV, POST_DISCOVERED
 from lib_py.agents.registry import agent_of_row, get_adapter, own_key
 from lib_py.delegation.mqtt_common import registry_lock
+from lib_py.delegation.registry import RESET_MARKER
 from lib_py.update import open_jobs, row_server
 from lib_py.verify_session import verify_session_uuid
 
@@ -484,6 +485,39 @@ def target_open_jobs(workspace: str, state: dict, env: Mapping[str, str], sessio
     return out
 
 
+def fence_registries(workspace: str, state: dict, env: Mapping[str, str]) -> Iterator[str]:
+    """Write RESET_MARKER into every registry open_jobs reads, each under its
+    registry lock (a registration that read no marker has finished writing),
+    and yield its real path as it is written. This workspace's .mam/jobs and
+    MAM_JOBS_DIR (created when absent) refuse every registration; another
+    control plane's registry named by a row refuses only those addressed to
+    this registry's rows. The marker copies .mam/reset-in-progress."""
+    with open(os.path.join(workspace, ".mam", "reset-in-progress"), encoding="utf-8") as fh:
+        base = "".join(l + "\n" for l in fh.read().splitlines() if l.split("=", 1)[0] in ("pid", "lstart", "started"))
+    base += "workspace=%s\n" % workspace
+    rows = state.get("herdr_sessions") or []
+    sessions = ",".join("herdr:%s" % s["name"] for s in rows if s.get("name"))
+    plan, seen = [], set()
+    for d in (os.path.join(workspace, ".mam", "jobs"), env.get("MAM_JOBS_DIR") or ""):
+        if d:
+            os.makedirs(d, exist_ok=True)
+            plan.append((d, base))
+    for s in rows:
+        d = (s.get("control_plane") or {}).get("mam_jobs_dir") or ""
+        if d and os.path.isdir(d):
+            plan.append((d, base + "sessions=%s\n" % sessions))
+    for d, text in plan:
+        if _real(d) in seen:
+            continue
+        seen.add(_real(d))
+        with registry_lock(d):
+            fd, tmp = tempfile.mkstemp(dir=d, prefix=RESET_MARKER + ".")
+            with os.fdopen(fd, "w", encoding="utf-8") as fh:
+                fh.write(text)
+            os.replace(tmp, os.path.join(d, RESET_MARKER))
+        yield _real(d)
+
+
 def target_id_owned(state: dict, session_name: str) -> bool:
     """The row's recorded post-discovered id still verifies (revalidate) as a
     conversation of the row's cwd - the check stop makes before it keeps such
@@ -757,6 +791,9 @@ def main(argv: Optional[List[str]] = None) -> int:
     s.add_argument("--workspace", required=True)
     s.add_argument("--session", required=True)
 
+    s = sub.add_parser("fence")
+    s.add_argument("--workspace", required=True)
+
     s = sub.add_parser("id-owned")
     s.add_argument("--workspace", required=True)
     s.add_argument("--session", required=True)
@@ -814,12 +851,6 @@ def main(argv: Optional[List[str]] = None) -> int:
         return 1 if sel["errors"] else 0
 
     if a.cmd == "precheck":
-        # A registration that read no reset marker finishes writing under this
-        # lock before the open jobs are listed (registry.reset_refusal).
-        jobs_dir = os.path.join(ws, ".mam", "jobs")
-        if os.path.isdir(jobs_dir):
-            with registry_lock(jobs_dir):
-                pass
         lines = precheck(ws, state, os.environ)
         for line in lines:
             print(line)
@@ -852,6 +883,15 @@ def main(argv: Optional[List[str]] = None) -> int:
             print(line)
         return 1 if lines else 0
 
+    if a.cmd == "fence":
+        try:
+            for d in fence_registries(ws, state, os.environ):
+                print(d, flush=True)
+        except OSError as exc:
+            print("ERROR: cannot fence the job registries (%s)" % exc, file=sys.stderr)
+            return 1
+        return 0
+
     if a.cmd == "id-owned":
         return 0 if target_id_owned(state, a.session) else 1
 

.agents/skills/multi-agent-mux-delegate-job/registry.md

@@ -141,8 +141,8 @@ $PY scripts/registry.py status --job <id> --set completed          # set status
 $PY scripts/registry.py pick   --agent-session herdr:claude         # claim → running
 ```
 
-Exit codes: `0` ok, `1` not found / bad status / (`register`) a reset of the
+Exit codes: `0` ok, `1` not found / bad status / (`register`) a reset fenced
-workspace owning `<ws>/.mam/jobs` is in progress (Issue #78), `3` (`pick`) no
+this registry (its `.reset-in-progress` names a live reset, Issue #78), `3` (`pick`) no
 pending job for that session.
 
 ---

.agents/skills/multi-agent-mux-reset/SKILL.md

@@ -23,7 +23,7 @@ bash .agents/skills/multi-agent-mux-reset/scripts/reset.sh --yes [--dry-run]
 | Targets | Every registry row with `status: running` and `realpath(pane.cwd) == realpath(WS)`. Rows with any other status, worktree rows, and `orchestrator_uuids` are skipped and listed with their reason. |
 | Confirmation | `[y/N]` prompt; without a terminal `-y`/`--yes` is required (exits `3` otherwise). `--dry-run` inspects without `--yes` and changes nothing. |
 | Prechecks | Refuses before any change when an open job exists (prints the `registry.py ... close --request cancelled` command), when `.mam/loop-guard-active` or `.mam/update-in-progress` is held, when a target row lacks a valid agent or role, when a running `claude`/`grok` target has no recorded conversation id (the monitor had not pinned one; record it, or stop/purge it by hand first), when `.mam/reset-spec.json` is invalid, or when the caller itself is one of the targets. |
-| Lock & concurrency | Takes the update admission lock exclusively, acquires `.mam/loop-guard-active` and publishes `.mam/reset-in-progress`, then releases the admission lock and runs the prechecks. `run_loop.sh`, `update.sh` and another reset refuse on the loop marker; every job registration in this workspace's `.mam/jobs` (`multi-agent-mux-delegate-job submit`, `registry.py register`, the registry API) refuses on the reset marker, except the onboarding jobs of the reset's own `create_session.sh`. |
+| Lock & concurrency | Takes the update admission lock exclusively, acquires `.mam/loop-guard-active` and publishes `.mam/reset-in-progress`, then releases the admission lock and runs the prechecks. `run_loop.sh`, `update.sh` and another reset refuse on the loop marker. The reset then writes `.reset-in-progress` into every job registry its open-job check reads (`.mam/jobs`, `MAM_JOBS_DIR`, and a row's other `control_plane.mam_jobs_dir`), each under that registry's lock, before the check. A registration (`multi-agent-mux-delegate-job submit`, `registry.py register`, the registry API) into a fenced registry - by any path to that directory - refuses; in another control plane's registry only for this workspace's sessions. The onboarding jobs of the reset's own `create_session.sh` are let through. |
 | Spec file & rerun | Writes `.mam/reset-spec.json` atomically before the first stop/purge and removes it only when all targets reach `done`. Rerunning resumes from the spec file without re-purging already recreated agents (`created` or `done`). |
 | Sequence per target | Sequential (never parallel): ⓪ re-checks that its row still has the spec's agent and herdr server and that no job addressed to it is open, ① normal `stop_session.sh --reason reset` (a post-discovered agent's id is captured onto the row while herdr is live; `status: stopped`), ② checks that the row's id is the one recorded before the stop and, for a post-discovered agent, that it still verifies as a conversation of the row's folder, ③ `stop_session.sh --reason reset --purge-conversation --yes` (using the row's recorded ID, never a CLI UUID), then `create_session.sh` with the original name, agent, role, `--herdr-session`, and `--herdr-workspace` (onboarding enabled by default). |
 | When skipped (exit 4) | The target is skipped and the reset continues to the next agent when step ⓪ finds a changed row (`row changed`) or an open job (`job open`) - nothing was changed for it -, or when step ② finds no id (`no conversation id recorded`) or an id other than the recorded one or one that does not verify for the row's folder (`id not verified`), or step ③ exits `4` (`purge refused`, in-use gate) - it is stopped but resumable (its row keeps its id) and its conversation files are untouched. Rerun once the cause is gone, or resume it. |
@@ -44,5 +44,5 @@ bash .agents/skills/multi-agent-mux-reset/scripts/reset.sh --yes [--dry-run]
 - **No external process termination**: processes holding conversation files open (reported via `lsof` in `in_use_hints`) are never signalled by MAM; end them yourself when safe, then rerun.
 - **Shared stores preserved**: Grok's shared `memory-v2.db` is left intact during purge; only session rows and per-session files are removed.
 - **Orchestrator hook during reset**: while `.mam/loop-guard-active` is held by the reset, the AGY orchestrator's direct file-edit hook (`loop_delegation_guard.sh`) blocks direct edits until the reset finishes.
-- **Job submissions during a reset**: `multi-agent-mux-delegate-job submit` and `registry.py register` refuse with `a reset of <WS> is in progress` until the reset ends; submit again afterwards. A record written into `.mam/jobs` by hand for a target after the precheck makes that target `job open` (skipped, not cancelled) if it is there before that target's stop.
+- **Job submissions during a reset**: `multi-agent-mux-delegate-job submit` and `registry.py register` refuse with `a reset of <WS> is in progress` until the reset ends (a marker left by a killed reset is stale and ignored); submit again afterwards. A record written into `.mam/jobs` by hand for a target after the precheck makes that target `job open` (skipped, not cancelled) if it is there before that target's stop.
 - **Same-type post-discovered ordering**: when resetting multiple post-discovered agents of the same type, the second `create_session.sh` waits up to `MAM_ID_ORDER_WAIT_S` for the first agent's ID to be recorded; if it times out, rerun the reset once the ID is recorded.

.agents/skills/multi-agent-mux-reset/scripts/reset.sh

@@ -92,9 +92,8 @@ _refuse_locked() {
 # The update admission lock is taken exclusively, as update.sh does, while the
 # reset publishes its markers: a delegate submit admitted earlier has written
 # its job record (the precheck below sees it), and one admitted later sees
-# .mam/reset-in-progress and refuses. Any other registration in .mam/jobs
+# .mam/reset-in-progress and refuses. Any other registration (registry.py
-# (registry.py register, the delegation API) reads the marker under the
+# register, the delegation API) is fenced below.
-# registry lock, which the precheck takes before it lists the open jobs.
 mkdir -p "$MAM"
 exec 7>>"$MAM/update-admission.lock"
 case "$("$PY" -m lib_py.pane_lock acquire --fd 7 --wait-env MAM_UPDATE_ADMISSION_WAIT_S)" in
@@ -115,7 +114,12 @@ case "$_acquire_rc" in
   3) _refuse_locked "a review loop or another reset is running (pid $(_mam_lock_field "$MARKER" "pid" 2>/dev/null || echo "unknown")); wait for it to end" ;;
   *) _refuse_locked "cannot determine whether a review loop or another reset is running (ps unavailable?)" ;;
 esac
+FENCED=()
 _release_reset_lock() {
+  local d
+  for d in ${FENCED[@]+"${FENCED[@]}"}; do
+    [ "$(_mam_lock_field "$d/.reset-in-progress" pid 2>/dev/null || true)" != "$$" ] || rm -f "$d/.reset-in-progress"
+  done
   mam_release_loop_lock "$RESET_MARKER" || true
   mam_release_loop_lock "$MARKER" || true
 }
@@ -140,6 +144,21 @@ if ! STATE_JSON="$(load_state_json strict)"; then
   exit 1
 fi
 
+# Every registry the precheck reads gets the reset marker under its own lock
+# (lib_py.reset fence): a registration that read none is written by then, any
+# later one is refused, by whatever path it names that registry.
+fence_out=""
+fence_rc=0
+fence_out="$(MAM_STATE_JSON="$STATE_JSON" "$PY" -m lib_py.reset fence --workspace "$WS")" || fence_rc=$?
+while IFS= read -r line; do
+  [ -n "$line" ] && FENCED+=("$line")
+done <<< "$fence_out"
+if [ "$fence_rc" -ne 0 ]; then
+  echo "ERROR: reset refused; nothing was changed:" >&2
+  echo "  - the job registries could not be fenced against new registrations (lib_py.reset fence rc $fence_rc)" >&2
+  exit 1
+fi
+
 pre_out=""
 pre_rc=0
 pre_out="$(MAM_STATE_JSON="$STATE_JSON" "$PY" -m lib_py.reset precheck --workspace "$WS")" || pre_rc=$?

tests/test_issue78_reset.py

@@ -1655,7 +1655,7 @@ if args[:2] == ["pane", "close"] or args[:1] == ["kill-session"]:
              "--agent-session", "herdr:{name_b}", "--prompt", "hi"],
             cwd={repr(str(mam_sandbox))}, stdin=subprocess.DEVNULL, capture_output=True, text=True, timeout=120,
         )
-        jobs = sorted(os.listdir({repr(str(jobs_dir))})) if os.path.isdir({repr(str(jobs_dir))}) else []
+        jobs = sorted(n for n in os.listdir({repr(str(jobs_dir))}) if n.endswith(".json")) if os.path.isdir({repr(str(jobs_dir))}) else []
         with open(probe, "w", encoding="utf-8") as fh:
             json.dump({{"rc": res.returncode, "stdout": res.stdout, "stderr": res.stderr,
                         "marker": os.path.isfile(marker), "jobs": jobs}}, fh)
@@ -1790,17 +1790,32 @@ def test_mam_reset_admit_refuses_only_a_live_reset(mam_sandbox: Path):
     assert res_stale.returncode == 0, res_stale.stderr
 
 
-def test_registry_cli_is_refused_after_the_target_recheck(mam_sandbox: Path, mock_herdr: Path, mock_agents):
+@pytest.mark.parametrize("registry", ["canonical", "alias", "custom"])
-    """Review round 2 R1 (codex): the documented registry CLI, run by a caller
+def test_registry_cli_is_refused_after_the_target_recheck(
+    mam_sandbox: Path, mock_herdr: Path, mock_agents, registry: str
+):
+    """Review rounds 2-3 R1 (codex): the documented registry CLI, run by a caller
     that is not a child of the reset, after the target's open-job re-check and
-    before its stop, is refused by .mam/reset-in-progress and registers nothing;
+    before its stop, is refused and registers nothing - whether it names the
-    the reset's own create still registers its onboarding job."""
+    registry by its canonical path, by a symlink alias, or the registry is the
+    MAM_JOBS_DIR the reset runs with; the reset's own create still registers
+    its onboarding job."""
     import threading
 
     name = "reviewer-claude-01"
     _claude_transcript(mam_sandbox, mam_sandbox, UA)
     _mock_herdr_agent(mock_herdr, name, mam_sandbox, agent="claude")
     _write_rows(mam_sandbox, [_row(name, "claude", mam_sandbox, own_id=UA)])
+    jobs_dir = mam_sandbox / ".mam" / "jobs"
+    jobs_dir.mkdir(parents=True, exist_ok=True)
+    env_extra = None
+    cli_dir = jobs_dir
+    if registry == "alias":
+        cli_dir = mam_sandbox / "job-alias"
+        cli_dir.symlink_to(jobs_dir)
+    elif registry == "custom":
+        jobs_dir = cli_dir = mam_sandbox / "elsewhere" / "jobs"
+        env_extra = {"MAM_JOBS_DIR": str(jobs_dir)}
     stop = mam_sandbox / ".agents/skills/multi-agent-mux-stop/scripts/stop_session.sh"
     original = stop.with_name("stop-original.sh")
     stop.rename(original)
@@ -1821,7 +1836,6 @@ os.execv('/bin/bash', ['bash', {str(original)!r}, *sys.argv[1:]])
     )
     stop.write_text("#!/bin/bash\nexec %s %s \"$@\"\n" % (shlex.quote(sys.executable), shlex.quote(str(gate))))
     stop.chmod(0o755)
-    jobs_dir = mam_sandbox / ".mam" / "jobs"
     record: dict = {}
 
     def writer():
@@ -1831,9 +1845,9 @@ os.execv('/bin/bash', ['bash', {str(original)!r}, *sys.argv[1:]])
                 time.sleep(0.02)
             record["marker"] = (mam_sandbox / ".mam" / "reset-in-progress").is_file()
             before = sorted(p.name for p in jobs_dir.glob("*.json"))
-            registry = mam_sandbox / ".agents/skills/multi-agent-mux-delegate-job/scripts/registry.py"
+            cli = mam_sandbox / ".agents/skills/multi-agent-mux-delegate-job/scripts/registry.py"
             res = subprocess.run(
-                [sys.executable, str(registry), "--registry-dir", str(jobs_dir), "register",
+                [sys.executable, str(cli), "--registry-dir", str(cli_dir), "register",
                  "--prompt", "external concurrent work", "--agent", "claude-code", "--agent-session", "herdr:" + name],
                 capture_output=True, text=True, timeout=30,
             )
@@ -1845,7 +1859,7 @@ os.execv('/bin/bash', ['bash', {str(original)!r}, *sys.argv[1:]])
     worker = threading.Thread(target=writer)
     worker.start()
     try:
-        res = _run_reset(mam_sandbox, "--yes")
+        res = _run_reset(mam_sandbox, "--yes", env_extra=env_extra)
     finally:
         worker.join(timeout=90)
         _wait_reconcile_idle(mam_sandbox)
@@ -1858,53 +1872,77 @@ os.execv('/bin/bash', ['bash', {str(original)!r}, *sys.argv[1:]])
     assert _result_of(res.stdout, name) == "done"
     onboarding = [json.loads(p.read_text(encoding="utf-8")) for p in jobs_dir.glob("*.json")]
     assert [j["agent_session"] for j in onboarding] == ["herdr:" + name], onboarding
+    assert not (jobs_dir / ".reset-in-progress").exists()
+
+
+def _registry_marker(jobs_dir: Path, holder: subprocess.Popen, ws: Path, sessions: Optional[str] = None) -> None:
+    _live_marker(jobs_dir / ".reset-in-progress", holder)
+    with open(jobs_dir / ".reset-in-progress", "a", encoding="utf-8") as fh:
+        fh.write("workspace=%s\n" % ws)
+        if sessions is not None:
+            fh.write("sessions=%s\n" % sessions)
 
 
 def test_register_job_refuses_only_a_live_reset_not_its_own(mam_sandbox: Path, monkeypatch):
     from lib_py.delegation import registry
 
-    jobs_dir = str(mam_sandbox / ".mam" / "jobs")
+    jobs_dir = mam_sandbox / ".mam" / "jobs"
-    marker = mam_sandbox / ".mam" / "reset-in-progress"
+    other = mam_sandbox / "other-control-plane" / "jobs"
+    jobs_dir.mkdir(parents=True, exist_ok=True)
+    other.mkdir(parents=True)
     monkeypatch.delenv(registry.RESET_OWNER_ENV, raising=False)
     holder = subprocess.Popen(["sleep", "120"])
     try:
-        _live_marker(marker, holder)
+        _registry_marker(jobs_dir, holder, mam_sandbox)
+        _registry_marker(other, holder, mam_sandbox, sessions="herdr:a,herdr:b")
+        for d in (jobs_dir, other):
             with pytest.raises(registry.ResetInProgressError, match="a reset of %s is in progress" % mam_sandbox):
-            registry.register_job(prompt="p", agent_session="herdr:x", registry_dir=jobs_dir)
+                registry.register_job(prompt="p", agent_session="herdr:b", registry_dir=str(d))
-        assert not list(Path(jobs_dir).glob("*.json"))
+        # Another control plane's registry refuses only the reset's sessions
-        # Another control plane's registry is not this workspace's .mam/jobs
+        assert registry.register_job(prompt="p", agent_session="herdr:x", registry_dir=str(other))
-        assert registry.reset_refusal(str(mam_sandbox / "elsewhere")) is None
+        assert not list(jobs_dir.glob("*.json"))
         monkeypatch.setenv(registry.RESET_OWNER_ENV, str(holder.pid))
-        assert registry.register_job(prompt="p", agent_session="herdr:x", registry_dir=jobs_dir)
+        assert registry.register_job(prompt="p", agent_session="herdr:x", registry_dir=str(jobs_dir))
         monkeypatch.delenv(registry.RESET_OWNER_ENV)
     finally:
         holder.kill()
         holder.wait()
-    assert registry.register_job(prompt="p", agent_session="herdr:x", registry_dir=jobs_dir)
+    assert registry.register_job(prompt="p", agent_session="herdr:x", registry_dir=str(jobs_dir))
-    assert len(list(Path(jobs_dir).glob("*.json"))) == 2
+    assert len(list(jobs_dir.glob("*.json"))) == 2
 
 
-def test_precheck_waits_for_a_registration_holding_the_registry_lock(tmp_path: Path):
+def test_fence_waits_for_a_registration_and_covers_every_registry_read(tmp_path: Path):
-    """R1 lock order: a registration that read no reset marker holds the registry
+    """R1 lock order and scope: a registration that read no marker holds the
-    lock until its record is written; the precheck, run after the marker is
+    registry lock until its record is written; fence writes the marker under
-    published, takes that lock before it lists the open jobs, so it sees the job."""
+    that lock, so it waits, and the precheck after it sees the job. Fenced are
+    .mam/jobs, MAM_JOBS_DIR (one marker for an alias of the same directory) and
+    a row's other control-plane registry (for this registry's sessions only)."""
     import fcntl
 
     ws = tmp_path / "ws"
     jobs_dir = ws / ".mam" / "jobs"
     jobs_dir.mkdir(parents=True)
-    state = {"herdr_sessions": [_row("reviewer-claude-01", "claude", ws, own_id=UA)]}
+    (ws / "alias").symlink_to(jobs_dir)
-    env = dict(os.environ, PYTHONPATH=str(SKILLS), PYTHONDONTWRITEBYTECODE="1", MAM_STATE_JSON=json.dumps(state))
+    other = tmp_path / "cp" / "jobs"
-    env.pop("MAM_JOBS_DIR", None)
+    other.mkdir(parents=True)
+    row = _row("reviewer-claude-01", "claude", ws, own_id=UA)
+    row["control_plane"] = {"mam_jobs_dir": str(other)}
+    state = {"herdr_sessions": [row]}
+    env = dict(os.environ, PYTHONPATH=str(SKILLS), PYTHONDONTWRITEBYTECODE="1", MAM_STATE_JSON=json.dumps(state),
+               MAM_JOBS_DIR=str(ws / "alias"))
+    holder = subprocess.Popen(["sleep", "120"])
+    try:
+        _live_marker(ws / ".mam" / "reset-in-progress", holder)
         lock = open(jobs_dir / ".lock", "a")
         fcntl.flock(lock, fcntl.LOCK_EX)
         try:
             proc = subprocess.Popen(
-            [sys.executable, "-m", "lib_py.reset", "precheck", "--workspace", str(ws)],
+                [sys.executable, "-m", "lib_py.reset", "fence", "--workspace", str(ws)],
                 env=env, stdout=subprocess.PIPE, stderr=subprocess.PIPE, text=True,
             )
             time.sleep(1.5)
             assert proc.poll() is None, proc.communicate()
+            assert not (jobs_dir / ".reset-in-progress").exists()
             (jobs_dir / "job78locked.json").write_text(
                 json.dumps({"job_id": "job78locked", "agent_session": "herdr:reviewer-claude-01", "status": "pending"}),
                 encoding="utf-8",
@@ -1913,8 +1951,18 @@ def test_precheck_waits_for_a_registration_holding_the_registry_lock(tmp_path: P
             fcntl.flock(lock, fcntl.LOCK_UN)
             lock.close()
         out, err = proc.communicate(timeout=30)
-    assert proc.returncode == 1, out + err
+        assert proc.returncode == 0, out + err
-    assert "job job78locked" in out
+        assert out.split() == [os.path.realpath(jobs_dir), os.path.realpath(other)]
+        own = (jobs_dir / ".reset-in-progress").read_text(encoding="utf-8")
+        assert "pid=%d\n" % holder.pid in own and "workspace=%s\n" % os.path.realpath(ws) in own
+        assert "sessions=" not in own
+        assert "sessions=herdr:reviewer-claude-01\n" in (other / ".reset-in-progress").read_text(encoding="utf-8")
+        pre = subprocess.run([sys.executable, "-m", "lib_py.reset", "precheck", "--workspace", str(ws)],
+                             env=env, capture_output=True, text=True, timeout=30)
+        assert pre.returncode == 1 and "job job78locked" in pre.stdout, pre.stdout + pre.stderr
+    finally:
+        holder.kill()
+        holder.wait()
 
 
 @pytest.mark.parametrize("artifact_cwd", ["own", "foreign"])