errors.append(f"Max {cfg.MAX_GMAIL_ACCOUNTS_PER_CAMPAIGN} accounts per campaign")
    else:
        for aid in data.account_ids:
            acc = await db.get(GmailAccount, aid)
            if not acc or acc.user_id != user.id:
                errors.append(f"Gmail account {aid} not found")
            elif acc.status != "authorized" or not acc.is_active:
                errors.append(f"Account {acc.email} is not authorized/active")

    if data.attach_mode == "pdf":
        if not (data.attach_pdf or data.attach_pdf_template_id or data.attachment_id):
            errors.append("PDF attachment mode requires a template or attachment to convert")
    if data.attach_mode in ("file", "image") and not data.attachment_id:
        errors.append("File/image attachment mode requires selecting an attachment")

    if len(data.rotation_weights or {}) > 0 and data.rotation_strategy != "weighted":
        errors.append("rotation_weights only applies when rotation_strategy is weighted")

    # variable config sanity
    vc = data.variable_config or {}
    try:
        if "amount_min" in vc and "amount_max" in vc and float(vc["amount_min"]) > float(vc["amount_max"]):
            errors.append("amount_min must be <= amount_max")
        if "shipping_min" in vc and "shipping_max" in vc and float(vc["shipping_min"]) > float(vc["shipping_max"]):
            errors.append("shipping_min must be <= shipping_max")
    except (TypeError, ValueError):