fix(issue-23): the remote audit record names the dispatch it vouches for; a record without identity fails closed

Review round 4 (planner-reviewer-claude-01 B-1, planner-reviewer-codex-01
P2, reached independently): dispatch_verified is a boolean. It says the
subscriber's token check ran when the record was written, but names no
dispatch, the token being masked by the audit redactor and attempt_id not
written. events.ndjson is appended to across a job's attempts, so a started
verified under attempt 1 satisfied every later attempt's wait - the very
misattribution R1 forbids, alive on the remote path while the local path
(data.dispatch_token in events.log) was already immune. codex reproduced it
with the real signed producer, the real _Watcher, the real audit writer and
the real operator re-dispatch; both waits answered 0 where 1 was due, even
when attempt 2's subscriber had correctly dropped attempt 1's replayed packet.

The subscriber now writes dispatch_fingerprint = SHA-256 of the token it
verified, and attempt_id for readers. With a token demanded, the predicate
accepts an audit record only if it is dispatch_verified AND its fingerprint
equals SHA-256 of that token; a record with no fingerprint - written before
the field existed - names nothing and is rejected on that path. Without a
token, any received started counts, as before.

Fingerprint over attempt_id as the identity, weighing the two proposals: the
local path already compares the token, so hashing it keeps one identity axis
for both sources; the token is a uuid4 nonce (registry.py:141), 128 bits, so
its SHA-256 is not recoverable and it is a CAS fence rather than the HMAC
secret in the first place; and attempt_id cannot tell apart a token
re-minted within one attempt, where the token can. attempt_id is recorded
because it is cheap and readable, not relied on.

W7 pins codex's five cases end to end - current dispatch accepted, an old
attempt's record rejected after a real re-dispatch, still rejected when the
stale packet is replayed and dropped, the new dispatch's own started
accepted, a bad HMAC never recorded - with create's wait and the wrapper's
wait required to agree on each. W8 pins the fail-closed legacy record and
the untokened compatibility path. W5 gains the no-fingerprint and
other-dispatch cases; W6 checks the real _Watcher writes the fingerprint and
never the token. S7e's status reset had no reason left and is gone. codex's
own reproduction file, unmodified, passes 5/5 against this tree.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

.agents/skills/lib.sh

@@ -2233,8 +2233,15 @@ except Exception:
 #    `started` it received, the only evidence a REMOTE agent (no shared disk)
 #    can leave. The subscriber verifies the HMAC and drops any event whose
 #    data.dispatch_token differs from the job's expected token before it
-#    writes this record, and marks it dispatch_verified when that check ran;
+#    writes this record (dispatch_verified), and writes dispatch_fingerprint
-#    with <dispatch_token> given, only a dispatch_verified record counts.
+#    = SHA-256 of that token. The file is appended to across a job's
+#    attempts, so the flag alone would let an earlier attempt's record
+#    acknowledge a later dispatch (review round 4): with <dispatch_token>
+#    given, a record counts only if it is dispatch_verified AND its
+#    fingerprint equals SHA-256(<dispatch_token>). A record with no
+#    fingerprint (written before this field existed) names no dispatch and
+#    is rejected on that path - fail closed. Without a token, any received
+#    started counts, as before.
 #
 # Never the registry status: a record leaves `pending` when another writer
 # closes it or another dispatch claims it. Lines are parsed as JSON, never
@@ -2247,8 +2254,9 @@ delegate_started_recorded() {
   local audit="$logs_dir/$job_id/events.ndjson"
   [ -f "$ev_log" ] || [ -f "$audit" ] || return 1
   EV_LOG="$ev_log" EV_AUDIT="$audit" EV_TOK="$tok" python3 -c '
-import json, os, sys
+import hashlib, json, os, sys
 tok = os.environ.get("EV_TOK", "")
+fp = hashlib.sha256(tok.encode("utf-8")).hexdigest() if tok else ""
 
 def lines(path):
     if not os.path.isfile(path):
@@ -2271,7 +2279,9 @@ for e in lines(os.environ["EV_LOG"]):
 for e in lines(os.environ["EV_AUDIT"]):
     if e.get("event") != "received" or e.get("source_event") != "started":
         continue
-    if not tok or e.get("dispatch_verified") is True:
+    if not tok:
+        sys.exit(0)
+    if e.get("dispatch_verified") is True and e.get("dispatch_fingerprint") == fp:
         sys.exit(0)
 sys.exit(1)
 ' 2>/dev/null

.agents/skills/lib_py/delegation/job_subscriber.py

@@ -24,6 +24,7 @@ Exit codes:
 from __future__ import annotations
 
 import argparse
+import hashlib
 import json
 import logging
 import queue
@@ -279,13 +280,19 @@ class _Watcher:
         # that survives defensive parsing is recorded here, including ones a
         # different host published. This is the external-observer record that
         # backstops the publisher's own "published" line if it never wrote one.
-        # `dispatch_verified` says this record is attributable to the job's
+        # Which dispatch this record vouches for. `dispatch_verified` says the
-        # current dispatch: the token check above ran (the registry record had
+        # token check above ran (the record had a dispatch_token and the
-        # a dispatch_token and the event's data.dispatch_token matched it) and
+        # event's data.dispatch_token matched it) after HMAC verification; on
-        # HMAC verification passed before that. The token itself is never
+        # its own it names no dispatch, and this file is appended to across a
-        # written - the audit redactor masks token-named keys - so this flag is
+        # job's attempts, so a reader waiting for a later dispatch would take
-        # what a local reader (delegate_started_recorded) can trust for a
+        # an earlier attempt's record as its acknowledgement (review round 4).
-        # remote agent's `started`, which has no line in events.log.
+        # `dispatch_fingerprint` is SHA-256 of the token that was verified -
+        # the same identity the local path compares in events.log, minus the
+        # token itself, which the audit redactor masks by key name and which a
+        # 128-bit uuid4 nonce is not recoverable from. `attempt_id` is kept for
+        # readers; it is not the identity, since a token can be re-minted
+        # within an attempt. A reader that demands a token must match the
+        # fingerprint; a record without one proves nothing about identity.
         mqtt_common.append_event(jid, {
             "event": "received",
             "source_event": payload.get("event"),
@@ -294,6 +301,10 @@ class _Watcher:
             "timestamp": payload.get("timestamp"),
             "detail": payload.get("detail", ""),
             "dispatch_verified": expected_disp_tok is not None,
+            "dispatch_fingerprint": (hashlib.sha256(expected_disp_tok.encode("utf-8")).hexdigest()
+                                     if expected_disp_tok else None),
+            "attempt_id": (data.get("attempt_id") if isinstance(data, dict) and data.get("attempt_id") is not None
+                           else self.attempts.get(jid)),
         })
         self.events.put((msg.topic, payload))
 

tests/test_issue23_24_startup_path.py

@@ -956,11 +956,17 @@ def test_w5_a_remote_agents_started_counts_only_through_the_subscribers_verified
         base.update(kw)
         return json.dumps(base) + "\n"
 
-    audit.write_text(rec(dispatch_verified=False))          # untokened record: not attributed
+    import hashlib
+    fp = lambda t: hashlib.sha256(t.encode()).hexdigest()
+    audit.write_text(rec(dispatch_verified=False, dispatch_fingerprint=None))   # untokened: not attributed
     assert "rc=1" in _wrapper_wait(tmp_path, jobs, "tok-1", ack_s=1, logs_dir=str(logs)).stdout
-    audit.write_text(rec(source_event="progress", dispatch_verified=True))   # not a started
+    audit.write_text(rec(source_event="progress", dispatch_verified=True, dispatch_fingerprint=fp("tok-1")))
+    assert "rc=1" in _wrapper_wait(tmp_path, jobs, "tok-1", ack_s=1, logs_dir=str(logs)).stdout   # not a started
+    audit.write_text(rec(dispatch_verified=True))                                # verified, no identity: fail closed
     assert "rc=1" in _wrapper_wait(tmp_path, jobs, "tok-1", ack_s=1, logs_dir=str(logs)).stdout
-    audit.write_text(rec(dispatch_verified=True))
+    audit.write_text(rec(dispatch_verified=True, dispatch_fingerprint=fp("tok-OLD")))   # another dispatch's
+    assert "rc=1" in _wrapper_wait(tmp_path, jobs, "tok-1", ack_s=1, logs_dir=str(logs)).stdout
+    audit.write_text(rec(dispatch_verified=True, dispatch_fingerprint=fp("tok-1")))
     assert "rc=0" in _wrapper_wait(tmp_path, jobs, "tok-1", ack_s=1, logs_dir=str(logs)).stdout
 
 
@@ -982,6 +988,112 @@ def test_w6_the_subscriber_stamps_dispatch_verified_on_what_it_records(mam_sandb
     recs = list(mqtt_common.iter_logged_events("job1", str(logs)))
     started = [r for r in recs if r.get("source_event") == "started"]
     assert len(started) == 1 and started[0]["dispatch_verified"] is True, recs
+    import hashlib
+    assert started[0]["dispatch_fingerprint"] == hashlib.sha256(b"tok-1").hexdigest(), started[0]
+    assert started[0]["attempt_id"] == 1, started[0]
+    assert "tok-1" not in json.dumps(started[0]), "the token itself must never reach the audit log"
+
+
+# --------------------------------------------------------------------------
+# review round 4 (planner-reviewer-claude-01 B-1, planner-reviewer-codex-01):
+# the remote audit record must name the dispatch it vouches for. Real signed
+# producer, real _Watcher.on_message, real audit writer, real re-dispatch
+# (registry operator write minting a new token) - no record is edited by hand.
+# --------------------------------------------------------------------------
+
+def _remote_fixture(tmp_path, monkeypatch):
+    import test_issue18_liveness_contract as live
+    jobs = tmp_path / "jobs"
+    env = live._env(tmp_path, dict(live.UNREACHABLE, MAM_DELEGATE_JOB_NO_MAIN="1",
+                                   MAM_JOBS_DIR=str(jobs)))
+    for key in ("MAM_ENV_FILE", "DELEGATE_JOB_LOGS_DIR", "WORKSPACE_ROOT"):
+        monkeypatch.setenv(key, env[key])
+    sys.path.insert(0, str(live.SKILLS))
+    from lib_py.delegation import job_subscriber, mqtt_common, publish_event, registry
+    return live, env, jobs, job_subscriber, mqtt_common, publish_event, registry
+
+
+def _receive(publish_event, watcher, jid, token, attempt, seq, secret):
+    """A signed `started` from the real producer, handed to the real subscriber."""
+    import types
+    payload = publish_event.build_payload(jid, seq, "started", "",
+                                          {"dispatch_token": token, "attempt_id": attempt}, secret)
+    watcher.on_message(None, None, types.SimpleNamespace(
+        topic="python/mqtt/jobs/%s/events" % jid, payload=json.dumps(payload).encode()))
+
+
+def _both_waits(live, env, tmp_path, jobs, jid, token):
+    """create's delegate_wait_started and the wrapper's _wait_started, same inputs."""
+    import shlex
+    script = (
+        'source %s\nset +e\nPY=%s\nREGISTRY_DIR=%s\nACK_TIMEOUT=0\nTIMEOUT=60\nSTART_TIME=$(date +%%s)\n'
+        'LOGS_DIR_ABS=%s\n_disp_tok=%s\n'
+        'delegate_wait_started %s 0 "$_disp_tok"; echo CREATE_RC=$?\n'
+        '_wait_started %s 0; echo WRAPPER_RC=$?\n'
+    ) % (shlex.quote(str(live.WRAPPER)), shlex.quote(sys.executable), shlex.quote(str(jobs)),
+         shlex.quote(env["DELEGATE_JOB_LOGS_DIR"]), shlex.quote(token), jid, jid)
+    res = subprocess.run(["bash", "-c", script], env=env, cwd=str(tmp_path),
+                         capture_output=True, text=True, timeout=60)
+    out = res.stdout + res.stderr
+    c = int(out.split("CREATE_RC=")[1].split()[0]); w = int(out.split("WRAPPER_RC=")[1].split()[0])
+    return c, w, out
+
+
+@pytest.mark.parametrize("scenario,expected", [
+    ("current", 0), ("old_audit", 1), ("old_audit_and_stale_wire", 1),
+    ("new_dispatch_received", 0), ("invalid_hmac", 1),
+])
+def test_w7_remote_audit_is_bound_to_the_dispatch_being_waited_for(tmp_path, monkeypatch, scenario, expected):
+    """W7 (codex's five cases, real paths throughout). Attempt 1 under token A
+    leaves a verified audit record; the operator re-dispatches (attempt 2,
+    new token B, nothing edited by hand); waiting for B must not be answered
+    by A's record, even when B's subscriber correctly dropped A's replayed
+    packet - and B's own verified started must still be accepted. Both waits
+    must agree."""
+    live, env, jobs, job_subscriber, mqtt_common, publish_event, registry = _remote_fixture(tmp_path, monkeypatch)
+    jid, secret = "auditjob", "test-only-hmac-secret"
+    registry.register_job("remote audit", job_id=jid, registry_dir=str(jobs), auth_token=secret,
+                          dispatch_token="dispatch-A", transport="remote",
+                          broker={"host": "127.0.0.1", "port": 9, "tls": False})
+    w1 = job_subscriber._Watcher({jid}, {jid: secret}, {jid: 0}, {jid: "dispatch-A"}, {jid: 1})
+    _receive(publish_event, w1, jid, "dispatch-A", 1, 1, "wrong-secret" if scenario == "invalid_hmac" else secret)
+    recs = list(mqtt_common.iter_logged_events(jid, env["DELEGATE_JOB_LOGS_DIR"]))
+    assert sum(r.get("source_event") == "started" for r in recs) == (0 if scenario == "invalid_hmac" else 1), recs
+    token = "dispatch-A"
+    if scenario not in ("current", "invalid_hmac"):
+        job_subscriber._sync_remote_status(jid, "completed", str(jobs), token)
+        assert registry._operator_write(jid, str(jobs), status="pending", attempt_id=2, iteration=2) == 0
+        record = mqtt_common.load_job(jid, str(jobs))
+        token = record["dispatch_token"]
+        assert token != "dispatch-A" and record["attempt_id"] == 2, record
+        w2 = job_subscriber._Watcher({jid}, {jid: secret}, {jid: 0}, {jid: token}, {jid: 2})
+        if scenario == "old_audit_and_stale_wire":
+            _receive(publish_event, w2, jid, "dispatch-A", 1, 2, secret)     # A's packet replayed to B's subscriber
+            assert w2.events.empty(), "the subscriber must drop the stale dispatch"
+        elif scenario == "new_dispatch_received":
+            _receive(publish_event, w2, jid, token, 2, 2, secret)
+            assert not w2.events.empty()
+    assert not (jobs / ("%s.events.log" % jid)).exists(), "remote evidence comes only from the subscriber's audit"
+    c, w, out = _both_waits(live, env, tmp_path, jobs, jid, token)
+    assert (c, w) == (expected, expected), (scenario, c, w, out)
+
+
+def test_w8_a_record_without_identity_fails_closed_when_a_token_is_demanded(tmp_path, monkeypatch):
+    """W8: an audit record from before dispatch_fingerprint existed (verified,
+    no fingerprint) names no dispatch: rejected when a token is demanded,
+    accepted when none is (an untokened legacy job), exactly as before."""
+    live, env, jobs, job_subscriber, mqtt_common, publish_event, registry = _remote_fixture(tmp_path, monkeypatch)
+    jid = "legacyjob"
+    registry.register_job("legacy", job_id=jid, registry_dir=str(jobs), auth_token=None,
+                          dispatch_token="dispatch-L", transport="remote",
+                          broker={"host": "127.0.0.1", "port": 9, "tls": False})
+    mqtt_common.append_event(jid, {"event": "received", "source_event": "started", "seq": 1,
+                                   "topic": "t", "timestamp": "t", "detail": "",
+                                   "dispatch_verified": True}, env["DELEGATE_JOB_LOGS_DIR"])
+    c, w, out = _both_waits(live, env, tmp_path, jobs, jid, "dispatch-L")
+    assert (c, w) == (1, 1), ("token demanded: a record with no identity must not count", out)
+    c, w, out = _both_waits(live, env, tmp_path, jobs, jid, "")
+    assert (c, w) == (0, 0), ("no token demanded: compatibility path", out)
 
 
 def test_s7n_the_wrappers_wait_started_accepts_the_real_producers_line(mam_sandbox):
@@ -1037,7 +1149,7 @@ def test_s7e_a_started_from_another_dispatch_is_not_evidence(mam_sandbox):
                     "--event", "started", "--expect-dispatch-token", "tok-OLD", "--attempt-id", "1"],
                    check=True, capture_output=True, text=True, env=env, timeout=60)
     rec = jobs / "job1.json"
-    d = json.loads(rec.read_text()); d["dispatch_token"] = "tok-1"; d["status"] = "pending"
+    d = json.loads(rec.read_text()); d["dispatch_token"] = "tok-1"     # the re-dispatch; status untouched
     rec.write_text(json.dumps(d))
     res, published = _run_delivery(mam_sandbox, 0, seed_events=False)
     assert published == ["error"], (published, res.stderr)