fix: attach_command from one builder; no kill/start_command; stop closes a row-less session (Issue #71)

- attach_command is `herdr --session <server> agent attach <herdr name>`
  (`default` written too), built by lib_py.agents.sanitize.attach_command;
  create, resume and reconcile all use it. kill_command and start_command
  are no longer written, and status --json drops start_command.
- The two raw kill-session hints (create exit 43, id_order's orphan) print a
  stop-skill command with --herdr-session instead.
- stop_session.sh closes a session that has no registry row, herdr only and
  without --agent, when herdr runs it inside this workspace; another
  workspace's session is refused (exit 5), a missing one is exit 1, one that
  survives kill-session is exit 6. The registry is not changed.
- Docs: only the SKILL.md lines these changes made wrong; the skill block
  pins follow. Tests that asserted the removed fields keep their intent
  (issue50: create's own row; issue21: no control-root path in
  attach_command; tier2: the new form and the absent fields). S11 pins the
  shim to 4243da5, which changed it on purpose.

Refs #71

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

.agents/skills/lib_py/agents/id_order.py

@@ -341,7 +341,8 @@ def wait(cwd: str, agent: str, session: str, owner_pid: int,
                     print(
                         f"ERROR: {m['session']}'s create/resume exited before recording it, "
                         f"and {seen}; close it with: "
-                        f"HERDR_SESSION_NAME={srv} herdr kill-session -t {m['session']}",
+                        f"bash .agents/skills/multi-agent-mux-stop/scripts/stop_session.sh "
+                        f"--session {m['session']} --herdr-session {srv}",
                         file=sys.stderr, flush=True,
                     )
             return 1

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

@@ -146,12 +146,10 @@ herdr_sessions:
     cmd: claude
     cmd_full: claude --dangerously-skip-permissions
     cwd: /path/to/project
-  start_command: "HERDR_SESSION_NAME=<herdr_session> herdr new-session -d -s <SESSION_NAME> -x 140 -y 40 -c <WORKSPACE> <CMD_FULL>"
-  attach_command: "HERDR_SESSION_NAME=<herdr_session> herdr agent attach <SESSION_NAME>"
-  kill_command: "HERDR_SESSION_NAME=<herdr_session> herdr kill-session -t <SESSION_NAME>"
+  attach_command: "herdr --session <herdr_session> agent attach <herdr name of SESSION_NAME>"
 ```
 
-The three commands require `source .agents/skills/lib.sh` first — `new-session`/`kill-session` are tmux-compat pseudo-commands the shim translates, and `HERDR_SESSION_NAME` is what the shim reads to route to the right isolated herdr *session* (real `herdr` has no env-var-based scoping of its own; `herdr_session: default` needs no prefix at all).
+`attach_command` is a native herdr command and runs from any shell: it always names the server (`default` too) and names the agent as herdr registered it (lower case, at most 32 characters: `lib_py/agents/sanitize.py`). Start and stop sessions only through the create, resume and stop skills.
 
 ## Workflow
 
@@ -258,5 +256,5 @@ herdr agent read "$SESSION_NAME" --source visible --lines 20   # TUI ready = age
 
 - **Resuming an old conversation** → `multi-agent-mux-resume`
 - **Killing an existing session** → `multi-agent-mux-stop`
-- **Just attaching to an existing session** → `herdr agent attach <name>` (no skill needed)
+- **Just attaching to an existing session** → the row's `attach_command` (no skill needed)
 - **One-shot print mode (claude -p "...")** → no herdr needed; use `claude-code` skill's print mode

.agents/skills/multi-agent-mux-create/scripts/create_session.sh

@@ -361,7 +361,7 @@ cleanup_herdr_on_error() {
   if [ "$alive" = "1" ]; then
     _mark_row_rolled_back "running" "rollback-failed"
     echo "ERROR: rollback could not kill herdr session '$SESSION_NAME' (kill rc=$kill_rc) - it is still running." >&2
-    echo "       Clean it up with: HERDR_SESSION_NAME=${HERDR_SESSION_NAME:-default} herdr kill-session -t $SESSION_NAME" >&2
+    echo "       Clean it up with: bash .agents/skills/multi-agent-mux-stop/scripts/stop_session.sh --session $SESSION_NAME --herdr-session ${HERDR_SESSION_NAME:-default}" >&2
     exit 43
   fi
   _mark_row_rolled_back "terminated" "rolled-back"
@@ -428,11 +428,6 @@ PANE_PID=$(_herdr list-panes -t "$SESSION_NAME" -F '#{pane_pid}' 2>/dev/null ||
 PANE_CWD=$(_herdr list-panes -t "$SESSION_NAME" -F '#{pane_current_path}' 2>/dev/null || echo "$WORKSPACE")
 PANE_CMD=$(_herdr list-panes -t "$SESSION_NAME" -F '#{pane_current_command}' 2>/dev/null || echo "$AGENT")
 
-# 시작 명령
-# NOTE: this must match what `spawn()` actually ran above — env-var-driven
-# herdr server shim (HERDR_SESSION_NAME picked up by the lib.sh shim).
-START_CMD="HERDR_SESSION_NAME=${HERDR_SESSION_NAME:-default} herdr new-session -d -s \"$SESSION_NAME\" -x 140 -y 40 -c \"$WORKSPACE\" \"$CMD_FULL\""
-
 # If --onboard is specified, automatically build the onboarding prompt (if session is ready)
 if [ "$ONBOARD" = "1" ] && [ -z "$SUBMIT_JOB_PROMPT" ] && [ -z "$LAST_VISIBLE_STATUS_OVERRIDE" ]; then
   SUBMIT_JOB_PROMPT="You are a newly spawned $ROLE Team Leader agent in this workspace. Without making any non-standard pre-preparations or modifying files directly, proceed immediately to align yourself with the project context by performing the following tasks:
@@ -508,12 +503,13 @@ fi
 atomic_dump_yaml "$AGENT_SESSIONS_YAML" \
   SESSION_NAME="$SESSION_NAME" AGENT="$AGENT" NOW_ISO="$NOW_ISO" \
   HERDR_EPOCH="$HERDR_EPOCH" PANE_PID="$PANE_PID" PANE_CWD="$PANE_CWD" \
-  CMD_FULL="$CMD_FULL" START_CMD="$START_CMD" CHILD_PID="$CHILD_PID" \
+  CMD_FULL="$CMD_FULL" CHILD_PID="$CHILD_PID" \
   HERDR_SESSION_NAME="${HERDR_SESSION_NAME:-default}" \
   MAM_WS_LABEL="$MAM_WS_LABEL" \
   SESSION_UUID="$SESSION_UUID" \
   LAST_VISIBLE_STATUS_OVERRIDE="${LAST_VISIBLE_STATUS_OVERRIDE:-}" \
   DELEGATE_JOB_ID="$DELEGATE_JOB_ID" ROLE="$ROLE" CONTROL_PLANE_JSON="$CP_JSON" <<'PYEOF'
+from lib_py.agents.sanitize import attach_command
 name = os.environ['SESSION_NAME']
 agent = os.environ['AGENT']
 role = os.environ['ROLE']
@@ -567,9 +563,7 @@ entry = {
         'cmd_full': os.environ['CMD_FULL'],
         'cwd': os.environ['PANE_CWD'],
     },
-    'start_command': os.environ['START_CMD'],
-    'attach_command': f'HERDR_SESSION_NAME={server_name} herdr agent attach {name}',
-    'kill_command': f'HERDR_SESSION_NAME={server_name} herdr kill-session -t {name}',
+    'attach_command': attach_command(server_name, name),
 }
 
 if agent == 'claude':

.agents/skills/multi-agent-mux-monitor/scripts/reconcile.sh

@@ -566,7 +566,7 @@ def _pin_and_verify_resume(s, agent, cwd, uuid, degraded=False):
     actions.append(f"updated {id_name} id: {uuid}")
 
 
-from lib_py.agents.sanitize import sanitize_herdr_agent_name as _sanitize
+from lib_py.agents.sanitize import sanitize_herdr_agent_name as _sanitize, attach_command
 
 yaml_sessions = d.get('herdr_sessions', [])
 yaml_session_names = {s['name'] for s in yaml_sessions if s.get('name')}
@@ -656,7 +656,6 @@ if herdr_confirmed:
         _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 ""
         # The shim resolves this from the pane's root process. Fall back to now
         # only if that failed: 'now' can merely over-estimate creation time,
         # which tightens the stale-transcript guard, whereas 0 disables it and
@@ -674,9 +673,7 @@ if herdr_confirmed:
             'herdr_server': srv,
             'herdr_workspace': _slug(pm['cwd']),
             'pane': {'index': 0, 'pid': pm['pid'], 'cmd': agent, 'cmd_full': cmd_full, 'cwd': pm['cwd']},
-            'start_command': f'HERDR_SESSION_NAME={srv} herdr new-session -d -s "{name}" -x 140 -y 40 -c "{pm["cwd"]}" "{cmd_full}"',
-            'attach_command': f'HERDR_SESSION_NAME={srv} herdr agent attach {name}',
-            'kill_command': f'herdr {server_opt}kill-session -t {name}',
+            'attach_command': attach_command(srv, name),
             'last_visible_status': 'running',
             'last_visible_note': 'auto-registered by monitor',
         }

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

@@ -27,7 +27,7 @@ Three cases this skill handles:
 
 1. **herdr is dead, conversation lives** — `agent-sessions.yaml` has the UUID. The JSONL/db is on disk. Re-spawn the herdr session + run `claude -r <id>` / `agy --conversation <id>`.
 2. **herdr is alive but empty** — You started a session with `multi-agent-mux-create` but haven't sent a message yet (so no session id was assigned). The user can either send their first message (and the id is auto-assigned), or you can read the *workspace's* most recent conversation from `$HOME_DIR/.gemini/antigravity-cli/cache/last_conversations.json` (defaults to `~/.gemini/...`) for agy, or the latest `*.jsonl` in `$CLAUDE_PROJECT_DIR/<workspace-key>/` (defaults to `~/.claude/projects/`) for claude.
-3. **herdr is alive AND the agent inside is already running** — `resume_session.sh` only updates the row and exits 0. It does not attach and does not check the agent's permission flags (#45); attach with `herdr --session <server> agent attach <name>`, where `<server>` is the row's `herdr_session` (the server it was resumed on).
+3. **herdr is alive AND the agent inside is already running** — `resume_session.sh` only updates the row and exits 0. It does not attach and does not check the agent's permission flags (#45); attach with the row's `attach_command` (`herdr --session <server> agent attach <name>`, where `<server>` is the row's `herdr_session` and `<name>` the name herdr registered).
 
 ### Resuming a `stopped` session (`stopped → running`)
 
@@ -60,7 +60,7 @@ If the resolved id is empty → for Class A agents (`agy`, `hermes`, `opencode`,
 bash .agents/skills/multi-agent-mux-resume/scripts/resume_session.sh --workspace <path> --agent <agent> --session <name>
 ```
 
-`resume_session.sh` does the whole flow: original-cwd check, control-plane binding, the session-id decision (`lib_py/agents/session_ids.py`), the herdr-alive check, the agent command (adapter `resume-spec`, or `spawn-spec` for a Class A fresh spawn), spawn (just before it, the session's own empty shell left by a server restart is closed: same session id, no agent, nothing running; `lib_py/herdr_restore.py`), start-up dialogs, and the YAML update (`update_yaml_resumed.sh`, which also publishes a `progress "resumed"` event when the row has a `delegate_job_id`). It never attaches; attaching is a separate step that names the server, because the server the script exports does not reach the calling shell and the native `herdr` binary does not route on environment variables: `herdr --session <server> agent attach <name>` (`<server>` = the `--herdr-session` you passed, or the row's `herdr_session`).
+`resume_session.sh` does the whole flow: original-cwd check, control-plane binding, the session-id decision (`lib_py/agents/session_ids.py`), the herdr-alive check, the agent command (adapter `resume-spec`, or `spawn-spec` for a Class A fresh spawn), spawn (just before it, the session's own empty shell left by a server restart is closed: same session id, no agent, nothing running; `lib_py/herdr_restore.py`), start-up dialogs, and the YAML update (`update_yaml_resumed.sh`, which also publishes a `progress "resumed"` event when the row has a `delegate_job_id`). It never attaches; attaching is a separate step that names the server, because the server the script exports does not reach the calling shell and the native `herdr` binary does not route on environment variables: the row's `attach_command`, `herdr --session <server> agent attach <name>` (`<server>` = the `--herdr-session` you passed, or the row's `herdr_session`; `<name>` = the name herdr registered).
 
 | Option | Meaning |
 |---|---|
@@ -136,4 +136,4 @@ herdr --session "$SERVER" agent read "$SESSION_NAME" --source visible --lines 30
 
 - **No saved session yet** → `multi-agent-mux-create`
 - **Killing an existing session** → `multi-agent-mux-stop`
-- **Just attaching** → `herdr --session <server> agent attach <name>` (no skill needed; `<server>` = the row's `herdr_session`)
+- **Just attaching** → the row's `attach_command` (no skill needed; `herdr --session <server> agent attach <name>`, `<name>` = the name herdr registered)

.agents/skills/multi-agent-mux-resume/scripts/update_yaml_resumed.sh

@@ -116,6 +116,7 @@ atomic_dump_yaml "$AGENT_SESSIONS_YAML" \
   MAM_WS_LABEL="$MAM_WS_LABEL" MAM_WS_LABEL_EXPLICIT="${MAM_WS_LABEL_EXPLICIT:-0}" \
   ALREADY_RUNNING="$ALREADY_RUNNING" DROP_STALE_ID="$DROP_STALE_ID" \
   CMD_FULL_OPT="$CMD_FULL_OPT" <<'PYEOF'
+from lib_py.agents.sanitize import attach_command
 name = os.environ['SESSION_NAME']
 uuid = os.environ['UUID']
 agent = os.environ['AGENT']
@@ -147,9 +148,7 @@ if target is None:
         'herdr_workspace': wsl,
         'delegate_job_id': None,
         'pane': {'index': 0, 'pid': int(pane_pid) if pane_pid.isdigit() else 0, 'cmd': agent, 'cwd': ws_root},
-        'start_command': f'HERDR_SESSION_NAME={server_name} herdr agent attach {name}',
-        'attach_command': f'HERDR_SESSION_NAME={server_name} herdr agent attach {name}',
-        'kill_command': f'HERDR_SESSION_NAME={server_name} herdr kill-session -t {name}',
+        'attach_command': attach_command(server_name, name),
     }
     d.setdefault('herdr_sessions', []).append(target)
 else:
@@ -159,9 +158,7 @@ else:
         if is_explicit or not target.get('herdr_session'):
             target['herdr_session'] = sn
             target['herdr_server'] = sn
-            target['start_command'] = f'HERDR_SESSION_NAME={sn} herdr agent attach {name}'
-            target['attach_command'] = f'HERDR_SESSION_NAME={sn} herdr agent attach {name}'
-            target['kill_command'] = f'HERDR_SESSION_NAME={sn} herdr kill-session -t {name}'
+            target['attach_command'] = attach_command(sn, name)
     wsl = os.environ.get('MAM_WS_LABEL', '')
     ws_explicit = os.environ.get('MAM_WS_LABEL_EXPLICIT') == '1'
     if wsl and (ws_explicit or not target.get('herdr_workspace')):

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

@@ -94,11 +94,10 @@ lab-paper-pdf2md-creator-claude              default      running    alive  clau
       "job_id": null,
       "job_status": null,
       "pane_cwd": "/home/.../refer_landing_page",
-      "attach_command": "HERDR_SESSION_NAME=default herdr agent attach lab-landing-page-creator-claude",
+      "attach_command": "herdr --session default agent attach lab-landing-page-creator-claude",
       "drift_classes": [],
       "pane_pid": 12345,
       "cmd_full": "claude --dangerously-skip-permissions --session-id <uuid>",
-      "start_command": "...",
       "last_visible_status": "pinned"
     }
   ]

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

@@ -221,11 +221,10 @@ for s in d.get('herdr_sessions', []):
         'pane_cwd': pane.get('cwd'),
         'attach_command': s.get('attach_command'),
         'drift_classes': drift_by_name.get(name, []),
-        # Additive beyond the D8 example — needed by the M1 Detail Pane
-        # (pane pid / full launch command / start command / last banner text).
+        # Additive beyond the D8 example (pane pid / full launch command /
+        # last banner text).
         'pane_pid': pane.get('pid'),
         'cmd_full': pane.get('cmd_full'),
-        'start_command': s.get('start_command'),
         'last_visible_status': s.get('last_visible_status'),
     })
 

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

@@ -25,7 +25,6 @@ Stop an agent's herdr session gracefully, resolve and store the conversation ID,
 
 - The herdr session's recorded `pane.pid / cmd / cwd / mcp_attachments` for audit
 - The agent's on-disk conversation (claude `*.jsonl`, agy `conversations/*.db`) — so the user can `multi-agent-mux-resume` later
-- The `start_command` so a future `multi-agent-mux-create --session <name>` reproduces the same herdr spec
 
 The stop command is always **graceful by default**:
 1. Sends exit keys to the agent TUI (`/exit` for Claude, `/exit` for Agy) and waits 3 seconds.
@@ -35,7 +34,7 @@ The stop command is always **graceful by default**:
 
 ## Pre-flight
 
-`stop_session.sh` checks this itself: the YAML exists and the session is registered (otherwise exit 1), and a session already `stopped` is a no-op (exit 0).
+`stop_session.sh` checks this itself: the YAML exists (otherwise exit 1), and a session already `stopped` is a no-op (exit 0). A session with no registry row (its create or resume died before registering it) is still closed, herdr only and with no `--agent`: only when herdr runs it inside this workspace, on the `--herdr-session` server (or `HERDR_SESSION_NAME`). The registry is not changed.
 
 ## Workflow
 
@@ -59,10 +58,12 @@ bash .agents/skills/multi-agent-mux-stop/scripts/stop_session.sh \
 | Exit | Meaning |
 |---|---|
 | 0 | Stopped; or already `stopped` (no-op, except with `--purge-conversation`, which still purges) |
-| 1 | From the checks before the stop, nothing was changed: YAML not found, or the session is not registered. **The registry update after the stop also exits 1** (the row disappeared from the YAML during the run) |
+| 1 | From the checks before the stop, nothing was changed: YAML not found, or the session is neither registered nor on the herdr server. **The registry update after the stop also exits 1** (the row disappeared from the YAML during the run) |
 | 2 | Bad arguments (including the retired `--mode` / `--capture-id` / `--graceful`), or `--agent` omitted and not resolvable |
 | 3 | `--purge-conversation` without `--yes` |
 | 4 | Purge aborted: the herdr session, or an agent process still holding the conversation, survived the kill chain. Records preserved: the registry row and the conversation files are untouched, though the session itself may already be down |
+| 5 | No registry row, and herdr runs the session outside this workspace: refused, nothing changed |
+| 6 | No registry row, and its herdr session survived `kill-session`; the registry is unchanged |
 | other | The registry update after the stop (YAML / DB write) failed and its code is passed through |
 
 Exits 2 and 3, and exit 1 from the pre-stop checks, come before anything is stopped, so nothing was changed. On exit 1 from the registry update, or an `other` exit, the session may already be down while its row still says `running`: check with `multi-agent-mux-status`, then run the stop again (it is idempotent).

.agents/skills/multi-agent-mux-stop/scripts/stop_session.sh

@@ -28,9 +28,12 @@
 #              구분은 --purge-conversation 유무로 대체되었습니다.
 #
 # Exit codes:
-#   0 = success (or already-stopped no-op) | 1 = YAML not found / not registered
+#   0 = success (or already-stopped no-op; or a session with no row closed)
+#   1 = YAML not found / not registered and not on the herdr server
 #   2 = invalid args | 3 = interactive confirmation required (--yes 누락)
 #   4 = purge aborted (herdr session or an agent process holding the conversation survived the kill chain)
+#   5 = no row, and herdr runs the session outside this workspace (refused, nothing changed)
+#   6 = no row, and its herdr session survived kill-session (registry unchanged)
 set -euo pipefail
 
 # shellcheck disable=SC1091
@@ -110,16 +113,50 @@ else
   export HERDR_SESSION_NAME
 fi
 
-# --agent 미지정 시 레지스트리 기록으로 해석 (B-21).
-# ① row['agent'] → ② 세션명 접미사 → ③ pane.cmd 순. 셋 다 실패하면
-# 종전과 동일하게 exit 2 (헤더 :27-30 의 종료 코드 계약 유지).
-if [ -z "$AGENT" ]; then
-  AGENT="$(resolve_agent_type_from_registry "$SESSION_NAME")" || AGENT=""
-  [ -n "$AGENT" ] || {
-    echo "ERROR: cannot infer agent from '$SESSION_NAME'; pass --agent" >&2
-    exit 2
-  }
-fi
+# Issue #71: a session with no registry row (its create/resume died before
+# registering it) is closed here - herdr only, the registry is left alone. It
+# has no agent kind, so --agent is not needed. Only a session herdr runs
+# inside this workspace is closed; anything else changes nothing.
+stop_rowless() {
+  if [ "$PURGE" = "1" ]; then
+    echo "ERROR: session '$SESSION_NAME' not in $AGENT_SESSIONS_YAML; --purge-conversation needs its row. Nothing changed." >&2
+    exit 1
+  fi
+  local info cwd
+  info=$(herdr agent get "$SESSION_NAME" 2>/dev/null) || info=""
+  if [ -z "$info" ]; then
+    echo "ERROR: session '$SESSION_NAME' not in $AGENT_SESSIONS_YAML, and herdr server '${HERDR_SESSION_NAME:-default}' has no agent of that name. Nothing changed." >&2
+    exit 1
+  fi
+  cwd=$(printf '%s' "$info" | python3 -c '
+import sys, json
+raw = sys.stdin.read()
+try:
+    print(json.loads(raw[raw.index("{"):]).get("result", {}).get("agent", {}).get("cwd", "") or "")
+except Exception:
+    print("")
+')
+  if ! PANE_CWD="$cwd" python3 -c '
+import os, sys
+cwd, root = os.environ.get("PANE_CWD", ""), os.environ.get("WORKSPACE_ROOT", "")
+if not cwd or not root:
+    sys.exit(1)
+cwd, root = os.path.realpath(cwd), os.path.realpath(root)
+sys.exit(0 if cwd == root or cwd.startswith(root + os.sep) else 1)
+'; then
+    echo "ERROR: refusing to stop '$SESSION_NAME': it is not in $AGENT_SESSIONS_YAML, and herdr runs it in '${cwd:-<unknown>}', outside this workspace ($WORKSPACE_ROOT). Nothing changed." >&2
+    exit 5
+  fi
+  echo "session '$SESSION_NAME' has no registry row: closing its herdr session only (registry unchanged)"
+  herdr kill-session -t "$SESSION_NAME" 2>/dev/null || true
+  _wait_session_gone "$SESSION_NAME" 8 || true
+  if herdr has-session -t "$SESSION_NAME" 2>/dev/null; then
+    echo "ERROR: herdr session '$SESSION_NAME' is still running after kill-session (registry unchanged)" >&2
+    exit 6
+  fi
+  echo "closed herdr session '$SESSION_NAME' on server '${HERDR_SESSION_NAME:-default}' (no registry row)"
+  exit 0
+}
 
 # 세션이 YAML 에 있는지 + 해당 row 의 워크스페이스 cwd 및 delegate_job_id 추출.
 # JSON 으로 emit — cwd 에 '|' 가 들어가도 안전 (review item 7; 기존 cwd|jid 파서 대체).
@@ -136,10 +173,18 @@ for s in d.get('herdr_sessions', []):
                           'delegate_job_logs_dir': cp.get('delegate_job_logs_dir', '') or ''}))
         sys.exit(0)
 sys.exit(7)
-") || {
-  echo "ERROR: session '$SESSION_NAME' not in $AGENT_SESSIONS_YAML" >&2
-  exit 1
-}
+") || stop_rowless
+
+# --agent 미지정 시 레지스트리 기록으로 해석 (B-21).
+# ① row['agent'] → ② 세션명 접미사 → ③ pane.cmd 순. 셋 다 실패하면
+# 종전과 동일하게 exit 2 (헤더 :27-30 의 종료 코드 계약 유지).
+if [ -z "$AGENT" ]; then
+  AGENT="$(resolve_agent_type_from_registry "$SESSION_NAME")" || AGENT=""
+  [ -n "$AGENT" ] || {
+    echo "ERROR: cannot infer agent from '$SESSION_NAME'; pass --agent" >&2
+    exit 2
+  }
+fi
 
 TARGET_CWD=$(printf '%s' "$MAPPED_DATA" | python3 -c 'import sys,json; print(json.load(sys.stdin).get("cwd",""))')
 DELEGATE_JOB_ID=$(printf '%s' "$MAPPED_DATA" | python3 -c 'import sys,json; print(json.load(sys.stdin).get("job_id",""))')