return {"ok": False, "status": "rescheduled", "reason": "cooldown"}

        # Per-account rate window (0 = disabled; `or` coercion would silently
        # turn an explicit 0 into 1.0)
        interval = (float(campaign.send_interval_seconds)
                    if campaign.send_interval_seconds is not None else 1.0)
        ok, wait = _rate_window(f"acct:{account.id}", interval)
        if not ok:
            _reschedule(db, self, campaign.id, cr, job, timedelta(seconds=wait),
                        "rate limit window")
            return {"ok": False, "status": "rescheduled", "reason": "rate window"}

        # ------------------------------------------------------------- build message
        recipient = db.get(Recipient, cr.recipient_id)
        subject_row = db.get(SubjectLine, cr.generated_subject_id) if cr.generated_subject_id else None
        template = db.get(EmailTemplate, cr.generated_template_id) if cr.generated_template_id else None
        subject = subject_row.subject if subject_row else campaign.name
        if template is None:
            cr.status = "perm_failed"
            cr.last_error = "No template assigned"
            campaign.failed_count += 1
            db.commit()
            return {"ok": False, "status": "perm_failed", "reason": "no template"}

        var_cfg = dict(campaign.variable_config or {})
        engine = VariableEngine(var_cfg)
        _today = date.today()
        g = GeneratedValues(
            invoice_number=cr.generated_invoice_number,
            amount=cr.generated_amount,
            shipping=cr.generated_shipping,
            random_name=engine.generate_random_name(),
            invoice_date=var_cfg.get("invoice_date") or _today.isoformat(),
            due_date=var_cfg.get("due_date")
                      or (_effective_invoice_date(var_cfg.get("invoice_date") or _today.isoformat())
                          + timedelta(days=int(var_cfg.get("due_days", 14)))).isoformat(),
            phone=cr.generated_phone or var_cfg.get("company_phone", ""),
        )
        unsub_url = _unsubscribe_url(recipient, campaign)
        rec = _recipient_dict(recipient)
        cf = (recipient.custom_fields if recipient else None) or {}