fix(issue-21): review R1-R3 - no env as agent arguments on a reused pane, one jobs dir for a relative MAM_JOBS_DIR, stop keeps the audit-log root

Review 9a1adb46 (planner-reviewer-codex-01):

- R1 [P1] lib.sh new-session: a forwarded binding reached the agent as
  arguments. With env flags the idle-pane branch prefixed `env K=V ...` to
  the command that `herdr agent start ... --kind <agent> -- <args>` passes to
  the agent executable. An idle pane is now reused only when no environment
  has to be set; otherwise the pane is created by pane split / workspace
  create, which take --env. The dead `env` prefix code is removed (its
  send-text fallback would have typed the same line).
- R2 [P2] runner: a relative MAM_JOBS_DIR is resolved once against the
  control root, the way the wrapper (cwd=workspace_root) reads it, and that
  absolute dir is used for delegation, wait, report lookup and cleanup.
- R3 [P2] stop: the row's control_plane.delegate_job_logs_dir is restored
  (exported unless the caller set DELEGATE_JOB_LOGS_DIR), so the
  cancellation history lands in the row's audit-log root.

Tests: T3-1 and T3-3 now assert that the binding arrives as --env on the
pane-creation calls and that no env/K=V token follows `--` in agent start
(fresh and reused pane); T3-4c (audit root on stop) and T2-15 (relative
MAM_JOBS_DIR) are new. The design doc's compatibility table and a create
comment no longer describe the removed idle-pane env path.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017R3Eg7MEpSWnm1oB9ZPP6G

.agents/skills/lib.sh

@@ -775,14 +775,15 @@ except Exception:
     pass
 " 2>/dev/null || echo "")
 
-      if [ -n "$idle_pane" ]; then
+      # An idle pane is reused only when no environment has to be set: the
+      # pane's shell is already running, and `agent start ... -- <args>` hands
+      # every token after -- to the agent executable (--kind), so an
+      # `env K=V` prefix would reach the agent as arguments, not as its
+      # environment (Issue #21 R1). With env flags, fall through to
+      # pane split / workspace create, which take --env.
+      if [ -n "$idle_pane" ] && [ -z "$env_flags" ]; then
         existing_ws="$cand_ws"
         target_pane="$idle_pane"
-        if [ -n "$env_flags" ] && [ -n "$final_cmd" ]; then
-          idle_env="${env_flags//--env /}"
-          idle_env="${idle_env:+$idle_env }HERDR_WORKSPACE_ID=$existing_ws"
-          final_cmd="env $idle_env $final_cmd"
-        fi
         break
       fi
 

.agents/skills/lib_py/loop/runner.py

@@ -64,7 +64,9 @@ class LoopRunner:
         # diff, base and head come from; everything else - wrapper, registry,
         # checkpoint, loop guard, promotion, cleanup - stays on the control
         # root (workspace_root).
-        self.jobs_dir = Path(os.environ.get("MAM_JOBS_DIR") or self.mam_dir / "jobs")
+        # A relative MAM_JOBS_DIR is taken against the control root, as the
+        # wrapper (run with cwd=workspace_root) takes it.
+        self.jobs_dir = (self.workspace_root / Path(os.environ.get("MAM_JOBS_DIR") or self.mam_dir / "jobs")).resolve()
         self.worktree_root: Path = self.workspace_root
         self.worktree_given = False
         self.base_ref: Optional[str] = None

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

@@ -205,7 +205,8 @@ fi
 # Issue #21 (item 3): the control-plane binding. Persisted on the row always;
 # forwarded to the pane (leading K=V tokens that lib.sh's new-session turns
 # into --env) only when it differs from what --workspace alone implies.
-# lib.sh splits those flags unquoted (and the idle-pane path evals them), so a
+# lib.sh splits those flags unquoted (and, with env flags, never reuses an
+# idle pane - `agent start --` would pass them to the agent as arguments), so a
 # binding with whitespace that would have to be forwarded is refused.
 CP_JSON="$(mam_control_plane_json "$WORKSPACE" 2>/dev/null || true)"
 CP_PREFIX=""

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

@@ -133,7 +133,8 @@ for s in d.get('herdr_sessions', []):
         cwd = (s.get('pane') or {}).get('cwd', '')
         jid = s.get('delegate_job_id', '') or ''
         cp = s.get('control_plane') or {}
-        print(json.dumps({'cwd': cwd, 'job_id': jid, 'mam_jobs_dir': cp.get('mam_jobs_dir', '') or ''}))
+        print(json.dumps({'cwd': cwd, 'job_id': jid, 'mam_jobs_dir': cp.get('mam_jobs_dir', '') or '',
+                          'delegate_job_logs_dir': cp.get('delegate_job_logs_dir', '') or ''}))
         sys.exit(0)
 sys.exit(7)
 ") || {
@@ -150,6 +151,12 @@ ROW_JOBS_DIR=$(printf '%s' "$MAPPED_DATA" | python3 -c 'import sys,json; print(j
 if [ -z "${MAM_JOBS_DIR:-}" ] && [ -n "$ROW_JOBS_DIR" ]; then
   export MAM_JOBS_DIR="$ROW_JOBS_DIR"
 fi
+# Same for the audit log (R3): the cancellation history belongs next to the
+# registry the row names, not under $WORKSPACE_ROOT/.mam/delegate_job_logs.
+ROW_LOGS_DIR=$(printf '%s' "$MAPPED_DATA" | python3 -c 'import sys,json; print(json.load(sys.stdin).get("delegate_job_logs_dir",""))')
+if [ -z "${DELEGATE_JOB_LOGS_DIR:-}" ] && [ -n "$ROW_LOGS_DIR" ]; then
+  export DELEGATE_JOB_LOGS_DIR="$ROW_LOGS_DIR"
+fi
 DELEGATE_JOB_TOKEN=""
 DELEGATE_JOB_ATTEMPT=""
 if [ -n "$DELEGATE_JOB_ID" ]; then