multi-agent-mux/.agents/reports/reviewer-agy-01/report-05f28276.md

Code Review Report (4th Round Re-Review): PR #56 (fix/issue-50-55)

• Job ID: 05f28276
• Reviewer: agy (Session: herdr:reviewer-agy-01, Role: Reviewer)
• Date: 2026-10-12
• Target Pull Request: PR #56 (fix/issue-50-55, Closes #50, #55)
• Base Commit: efd27def47a4d67684694ccf43a6ebeede01620f (3rd round review head)
• Head Commit: 21f0c12b9e2195cba8e196d6ccc2469173302e8a (Fix commit)
• Verification Path: /var/folders/q_/68sxgw3j073dgjg8wl9s08vw0000gn/T/mam-review/loop-20261012T013821Z-656dfe/1
• Verification Environment: macOS (Darwin 24.3.0, arm64), Python 3.9.6, bash 3.2.57(1)-release, herdr 0.9.3

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1. Executive Summary

This 4th-round re-review evaluated commit 21f0c12b9e2195cba8e196d6ccc2469173302e8a, which addresses the regression discovered on macOS during full-suite testing where tests/test_tier4_e2e.py::test_e2e_scenario4_parallel_flock_locking (6 concurrent creates into the same folder) failed with exit code 4 (already running in agent-sessions.yaml).

Root Cause

During parallel create_session.sh invocations, create_session.sh runs reconcile.sh --once under ambient HERDR_SESSION_NAME=<slug>.

1. In reconcile.sh, unique_servers always includes 'default'.
2. The scan for 'default' executes herdr ls without -L.
3. The .mam/shim/herdr wrapper inspects HERDR_SESSION_NAME; because it is set to <slug>, _real_herdr delegates to "$HERDR_BIN" --session "$session" "$@".
4. Thus, the pane list returned by the 'default' scan actually reflects the panes on server <slug>.
5. Previously, reconcile.sh drift B labeled these newly discovered panes with herdr_server: default.
6. When concurrent create_session.sh processes attempted to adopt the auto-registered pane via _adopted_own, they required (s.get('herdr_server') or ...) == server_name (where server_name was <slug>). Because the monitor row recorded 'default', the comparison failed and create_session.sh aborted with exit code 4.

The Fix

In multi-agent-mux-monitor/scripts/reconcile.sh:659-661:

_ambient = os.environ.get('HERDR_SESSION_NAME', '')
if srv == 'default' and _ambient and _ambient != 'default':
    srv = _ambient
server_opt = f"-L {srv} " if srv != 'default' else ""

If the sweep is querying 'default' but HERDR_SESSION_NAME is set to an explicit server in the environment, reconcile.sh recognizes that the shim returned panes from that server, and records herdr_session: _ambient, herdr_server: _ambient, and -L _ambient in the entry. Additionally, tests/data/skill_code_blocks.json was updated to line 550 for SystemExit(4) in create_session.sh.

Verdict: PASS.

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2. Detailed Technical Verification

2.1 Correctness of the Ambient Server Attribution

• In .agents/skills/lib.sh:271-280:

  _real_herdr() {
    local session="${HERDR_SESSION_NAME:-}"
    if [ "$session" = "default" ]; then session=""; fi
    if [ -n "$session" ]; then
      if [ "${1:-}" = "--session" ] || [ "${1:-}" = "-s" ]; then "$HERDR_BIN" "$@"; else "$HERDR_BIN" --session "$session" "$@"; fi
    else
      "$HERDR_BIN" "$@"
    fi
  }
  

  Calls to herdr without -L or --session are answered by herdr --session "$session". Thus, attributing panes found in a 'default' scan to HERDR_SESSION_NAME is strictly faithful to the actual server queried by _real_herdr.

2.2 Side-Effect Analysis

1. Drift A (Termination Detection):
   • When a row is registered with herdr_server: <slug>, subsequent sweeps populate unique_servers from d.get('herdr_sessions'), adding <slug>.
   • reconcile.sh explicitly scans -L <slug> and places (name, '<slug>') into alive_set.
   • In drift A, (s.get('name'), s.get('herdr_server')) matches alive_set. The row is not falsely terminated.
2. Daemon Mode (No Ambient Server):
   • In persistent monitor daemon runs (reconcile.sh --subscribe), HERDR_SESSION_NAME is empty or 'default'.
   • _ambient and _ambient != 'default' evaluates to False, preserving exact default behavior.
3. Duplicate Registration Prevention:
   • In drift B, yaml_session_names.add(name) is updated immediately when a pane is registered.
   • If the same pane is enumerated in both the 'default' scan and an explicit -L <slug> scan within the same sweep, line 611 skips the duplicate (if (name, srv) in yaml_session_names or any(_sanitize(y) == name for y in yaml_session_names): continue). No duplicate entries are created.

2.3 Verification of Fixed Tests

1. test_e2e_scenario4_parallel_flock_locking:
   • Executed tests/test_tier4_e2e.py: all 5 scenarios passed in 364.51s, with scenario 4 completing in 42.28s without exit code 4.
2. tests/test_issue50_pane_lock.py:
   • Executed full test suite: 11 / 11 passed in 53.20s.
3. tests/test_issue42_skill_blocks.py:
   • Executed: 37 passed, 1 skipped. Line 550 in tests/data/skill_code_blocks.json matches create_session.sh exactly.

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3. Test Execution Summary

Test Target	Result	Duration
tests/test_tier4_e2e.py::test_e2e_scenario4_parallel_flock_locking	1 Passed	42.28s
tests/test_tier4_e2e.py (Full Suite, 5 Scenarios)	5 Passed	364.51s
tests/test_issue50_pane_lock.py (Full Suite)	11 Passed	53.20s
tests/test_issue42_skill_blocks.py	37 Passed, 1 Skipped	0.17s

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[VERDICT: PASS]