:root {
            color-scheme: light;
            --bg: #ffffff;
            --page: #f5f5f7;
            --panel: #ffffff;
            --panel-muted: #fbfbfd;
            --text: #1d1d1f;
            --muted: #6e6e73;
            --muted-2: #86868b;
            --line: #d2d2d7;
            --line-soft: #e8e8ed;
            --blue: #0071e3;
            --blue-hover: #0077ed;
            --blue-soft: #f0f7ff;
            --red: #d70015;
            --green: #1d7f3a;
            --radius-lg: 18px;
            --radius-md: 14px;
            --radius-sm: 10px;
            --shadow-pop: 0 14px 42px rgba(0, 0, 0, .14);
            --font: -apple-system, BlinkMacSystemFont, "SF Pro Text", "SF Pro Display", "Helvetica Neue", Arial, sans-serif;
        }


        :root[data-theme="dark"] {
            color-scheme: dark;
            --bg: #000000;
            --page: #101010;
            --panel: #161617;
            --panel-muted: #1d1d1f;
            --text: #f5f5f7;
            --muted: #a1a1a6;
            --muted-2: #86868b;
            --line: #3a3a3c;
            --line-soft: #2c2c2e;
            --blue: #2997ff;
            --blue-hover: #46a6ff;
            --blue-soft: rgba(41, 151, 255, .14);
            --red: #ff453a;
            --green: #30d158;
            --shadow-pop: 0 18px 48px rgba(0, 0, 0, .5);
        }

        * {
            box-sizing: border-box;
        }

        html, body {
            height: 100%;
        }

        body {
            margin: 0;
            overflow: hidden;
            background: var(--page);
            color: var(--text);
            font-family: var(--font);
            -webkit-font-smoothing: antialiased;
            text-rendering: optimizeLegibility;
        }

        button, input, textarea, select {
            font: inherit;
        }

        button {
            -webkit-tap-highlight-color: transparent;
        }

        ::selection {
            background: rgba(0, 113, 227, .18);
        }

        .app-shell {
            height: 100vh;
            height: 100dvh;
            min-height: 0;
            display: grid;
            grid-template-columns: 350px minmax(0, 1fr);
            overflow: hidden;
            background: var(--page);
        }

        .app-shell.sidebar-collapsed {
            grid-template-columns: 0 minmax(0, 1fr);
        }

        .app-shell.sidebar-collapsed .sidebar {
            max-height: 0;
            border-bottom: 0;
        }

        .app-shell.wide-mode .messages-inner,
        .app-shell.wide-mode .composer-inner,
        .app-shell.wide-mode .pending-files {
            width: min(1300px, 100%);
        }

        .messages-inner, .composer-inner, .pending-files {
            transition: width 0.3s ease;
        }

        .new-chat-btn, .settings-btn, .theme-btn, .sidebar-toggle-btn,
        .send-btn, .btn, .action-btn, .icon-btn, .custom-select-trigger,
        .thinking-header, .model-pill, .attach-btn, .code-copy-btn, .message-expand-btn {
            border: 0;
            cursor: pointer;
            transition: background-color .12s ease, border-color .12s ease, color .12s ease, transform .08s ease;
        }

        .new-chat-btn:active, .settings-btn:active, .theme-btn:active, .sidebar-toggle-btn:active,
        .send-btn:active, .btn:active, .action-btn:active, .icon-btn:active, .custom-select-trigger:active,
        .model-pill:active, .attach-btn:active, .code-copy-btn:active {
            transform: scale(.985);
        }

        .form-input, .form-select, .chat-input {
            width: 100%;
            background: transparent;
            border: 0;
            outline: 0;
            color: var(--text);
        }

        .form-input, .form-select {
            min-height: 42px;
            padding: 9px 11px;
            border: 1px solid var(--line);
            border-radius: 11px;
            background: var(--panel);
        }

        .form-input:focus, .form-select:focus,
        .input-wrap:focus-within,
        .custom-select.open .custom-select-trigger,
        .top-model-select.open .model-pill {
            border-color: var(--blue);
            box-shadow: 0 0 0 3px rgba(0, 113, 227, .12);
        }

        .top-model-option, .custom-option {
            width: 100%;
            min-height: 36px;
            padding: 8px 10px;
            border: 0;
            border-radius: 10px;
            background: transparent;
            color: var(--text);
            text-align: left;
            font-size: 13px;
            cursor: pointer;
            overflow: hidden;
            text-overflow: ellipsis;
            white-space: nowrap;
        }

        .top-model-option:hover, .custom-option:hover {
            background: var(--page);
        }

        .top-model-option.selected, .custom-option.selected {
            color: var(--blue);
            background: var(--blue-soft);
            font-weight: 700;
        }

        .top-model-option.empty, .custom-option.empty {
            color: var(--muted);
            cursor: default;
        }

        .sidebar {
            min-width: 0;
            min-height: 0;
            overflow: hidden;
            background: var(--panel-muted);
            border-right: 1px solid var(--line-soft);
            display: flex;
            flex-direction: column;
        }

        .brand-area {
            flex: 0 0 auto;
            padding: 22px 18px 16px;
            border-bottom: 1px solid var(--line-soft);
        }

        .brand-header {
            display: flex;
            align-items: center;
            gap: 12px;
            margin-bottom: 16px;
        }

        .brand-logo {
            position: relative;
            flex: 0 0 auto;
            width: 40px;
            height: 40px;
            display: inline-flex;
            align-items: center;
            justify-content: center;
            border-radius: 12px;
            background: linear-gradient(135deg,
                color-mix(in srgb, var(--blue, #4f7cff) 92%, #fff 8%) 0%,
                color-mix(in srgb, var(--blue, #4f7cff) 60%, #a78bfa 40%) 100%);
            color: #fff;
            box-shadow:
                0 6px 16px -6px color-mix(in srgb, var(--blue, #4f7cff) 70%, transparent),
                inset 0 1px 0 rgba(255, 255, 255, .35);
        }

        .brand-logo svg {
            width: 22px;
            height: 22px;
            display: block;
            filter: drop-shadow(0 1px 1px rgba(0, 0, 0, .15));
        }

        .brand-logo-glow {
            position: absolute;
            inset: -6px;
            border-radius: 16px;
            background: radial-gradient(closest-side,
                color-mix(in srgb, var(--blue, #4f7cff) 35%, transparent) 0%,
                transparent 70%);
            opacity: .55;
            pointer-events: none;
            z-index: -1;
            animation: brand-logo-pulse 4.2s ease-in-out infinite;
        }

        @keyframes brand-logo-pulse {
            0%, 100% { opacity: .35; transform: scale(1); }
            50% { opacity: .7; transform: scale(1.06); }
        }

        .brand-text {
            display: flex;
            flex-direction: column;
            line-height: 1.1;
            min-width: 0;
        }

        .brand-title {
            font-size: 20px;
            font-weight: 700;
            letter-spacing: -.02em;
            background: linear-gradient(90deg,
                var(--text) 0%,
                color-mix(in srgb, var(--text) 70%, var(--blue, #4f7cff) 30%) 100%);
            -webkit-background-clip: text;
            background-clip: text;
            -webkit-text-fill-color: transparent;
            margin: 0;
        }

        .brand-subtitle {
            font-size: 11px;
            font-weight: 600;
            letter-spacing: .14em;
            text-transform: uppercase;
            color: var(--muted-2, var(--muted));
            margin-top: 4px;
        }

        .toolbar-row {
            display: flex;
            gap: 8px;
        }

        .new-chat-btn {
            flex: 1;
            min-height: 40px;
            padding: 0 16px;
            border-radius: 999px;
            background: var(--blue);
            color: #fff;
            font-weight: 600;
        }

        .new-chat-btn:hover {
            background: var(--blue-hover);
        }

        .settings-btn {
            min-height: 40px;
            padding: 0 14px;
            border-radius: 999px;
            background: var(--panel);
            color: var(--text);
            border: 1px solid var(--line);
            font-weight: 600;
        }

        .theme-btn {
            width: 38px;
            height: 38px;
            padding: 0;
            display: inline-flex;
            align-items: center;
            justify-content: center;
            font-size: 18px;
            border-radius: 999px;
            background: var(--panel);
            color: var(--text);
            border: 1px solid var(--line);
        }

        .sidebar-toggle-btn {
            min-height: 40px;
            padding: 0 14px;
            border-radius: 999px;
            background: var(--panel);
            color: var(--text);
            border: 1px solid var(--line);
            font-weight: 600;
        }

        .settings-btn:hover, .theme-btn:hover, .sidebar-toggle-btn:hover {
            background: var(--page);
        }

        .conversation-list {
            flex: 1 1 auto;
            min-height: 0;
            overflow-y: auto;
            overflow-x: hidden;
            overscroll-behavior: contain;
            padding: 10px;
            scrollbar-gutter: stable;
        }

        .conversation-item {
            width: 100%;
            display: grid;
            grid-template-columns: minmax(0, 1fr) auto;
            gap: 8px;
            align-items: center;
            padding: 12px 10px 12px 12px;
            margin-bottom: 4px;
            border-radius: 12px;
            border: 1px solid transparent;
            color: var(--text);
            cursor: pointer;
            background: transparent;
        }

        .conversation-item:hover, .conversation-item.active {
            background: var(--panel);
            border-color: var(--line-soft);
        }

        .conversation-item.active {
            border-color: var(--line);
        }

        .conversation-title {
            min-width: 0;
            overflow: hidden;
            text-overflow: ellipsis;
            white-space: nowrap;
            font-size: 14px;
            font-weight: 500;
        }

        .conversation-meta {
            color: var(--muted-2);
            font-size: 12px;
            margin-top: 3px;
        }

        .conversation-actions {
            display: flex;
            gap: 3px;
            opacity: .82;
        }

        .icon-btn {
            width: 28px;
            height: 28px;
            display: inline-flex;
            align-items: center;
            justify-content: center;
            border-radius: 50%;
            background: transparent;
            color: var(--muted);
        }

        .icon-btn:hover {
            background: var(--page);
            color: var(--text);
        }

        .main {
            min-width: 0;
            min-height: 0;
            height: 100%;
            width: 100%;
            overflow: hidden;
            display: flex;
            flex-direction: column;
            background: var(--bg);
        }

        .app-header {
            flex: 0 0 auto;
            padding: 16px 28px 0;
            background:
                linear-gradient(180deg, color-mix(in srgb, var(--bg) 96%, var(--panel) 4%) 0%, color-mix(in srgb, var(--bg) 88%, transparent) 100%);
            border-bottom: 1px solid var(--line-soft);
            backdrop-filter: blur(18px);
            -webkit-backdrop-filter: blur(18px);
            z-index: 12;
        }

        .app-header-inner {
            width: min(1120px, 100%);
            margin: 0 auto;
            display: flex;
            flex-direction: column;
            gap: 10px;
        }

        /* ==================== 标签栏（分段控件） ==================== */
        .app-tabs {
            display: flex;
            align-items: center;
            justify-content: center;
        }

        .app-tabs-inner {
            display: inline-flex;
            align-items: center;
            padding: 5px;
            border-radius: 18px;
            background: color-mix(in srgb, var(--panel) 76%, transparent);
            border: 1px solid color-mix(in srgb, var(--line-soft) 78%, transparent);
            box-shadow: inset 0 1px 0 rgba(255, 255, 255, .16), 0 10px 24px rgba(15, 23, 42, .05);
            gap: 4px;
        }

        :root[data-theme="dark"] .app-tabs-inner {
            background: color-mix(in srgb, var(--panel) 88%, transparent);
            border-color: color-mix(in srgb, var(--line) 72%, transparent);
            box-shadow: inset 0 1px 0 rgba(255, 255, 255, .04), 0 12px 30px rgba(0, 0, 0, .22);
        }

        .app-tab {
            min-width: 112px;
            min-height: 40px;
            padding: 0 18px;
            border: 0;
            border-radius: 14px;
            background: transparent;
            color: var(--muted);
            font-weight: 600;
            font-size: 13px;
            letter-spacing: .01em;
            cursor: pointer;
            transition: color .18s ease, background-color .18s ease, box-shadow .18s ease, transform .18s ease;
            display: inline-flex;
            align-items: center;
            justify-content: center;
            gap: 6px;
            position: relative;
            white-space: nowrap;
        }

        .app-tab:hover {
            color: var(--text);
            background: color-mix(in srgb, var(--panel) 78%, transparent);
        }

        .app-tab.active {
            background: linear-gradient(180deg, color-mix(in srgb, var(--panel) 96%, white 4%) 0%, var(--panel) 100%);
            color: var(--text);
            box-shadow: 0 1px 2px rgba(15, 23, 42, .06), 0 8px 20px rgba(15, 23, 42, .08);
        }

        :root[data-theme="dark"] .app-tab.active {
            background: linear-gradient(180deg, color-mix(in srgb, var(--panel) 94%, white 6%) 0%, var(--panel) 100%);
            box-shadow: 0 1px 2px rgba(0, 0, 0, .35), 0 10px 24px rgba(0, 0, 0, .28);
        }

        .app-tab .tab-badge-new {
            display: inline-flex;
            align-items: center;
            justify-content: center;
            min-width: 30px;
            height: 18px;
            padding: 0 6px;
            border-radius: 999px;
            background: color-mix(in srgb, var(--blue) 14%, transparent);
            border: 1px solid color-mix(in srgb, var(--blue) 24%, transparent);
            color: var(--blue);
            font-size: 9px;
            font-weight: 700;
            line-height: 1;
            letter-spacing: .08em;
            margin-left: 2px;
        }

        .tab-content {
            display: none;
            flex: 1;
            min-height: 0;
            flex-direction: column;
            overflow: hidden;
        }

        .tab-content.active {
            display: flex;
        }

        /* ==================== 站点统计 ==================== */
        .site-stats {
            flex: 0 0 auto;
            text-align: center;
            padding: 6px 14px 8px;
            font-size: 11px;
            color: var(--muted-2);
            background: var(--bg);
            letter-spacing: .02em;
        }

        .site-stats span {
            color: var(--muted);
            font-weight: 600;
        }

        /* ==================== 在线人数徽章 ==================== */
        .online-badges {
            display: inline-flex;
            align-items: center;
            gap: 6px;
            margin-left: 8px;
            flex-wrap: wrap;
            justify-content: center;
            vertical-align: middle;
        }

        .online-badge {
            display: inline-flex;
            align-items: center;
            gap: 3px;
            padding: 2px 8px;
            border-radius: 999px;
            font-size: 10px;
            font-weight: 600;
            line-height: 1.4;
            border: 1px solid transparent;
        }

        .online-badge span,
        .online-total span {
            color: inherit !important;
            font-weight: 700;
        }

        .online-badge.chatting {
            background: rgba(59, 130, 246, 0.10);
            border-color: rgba(59, 130, 246, 0.25);
            color: #2563eb !important;
        }

        .online-badge.imaging {
            background: rgba(168, 85, 247, 0.10);
            border-color: rgba(168, 85, 247, 0.25);
            color: #9333ea !important;
        }

        .online-badge.idle {
            background: rgba(148, 163, 184, 0.12);
            border-color: rgba(148, 163, 184, 0.25);
            color: #64748b !important;
        }

        .online-total {
            margin-left: 4px;
            padding: 2px 8px;
            border-radius: 999px;
            background: rgba(34, 197, 94, 0.10);
            border: 1px solid rgba(34, 197, 94, 0.25);
            font-size: 10px;
            font-weight: 600;
            color: #16a34a !important;
        }

        :root[data-theme="dark"] .online-badge.chatting {
            background: rgba(96, 165, 250, 0.16);
            border-color: rgba(96, 165, 250, 0.35);
            color: #93c5fd !important;
        }

        :root[data-theme="dark"] .online-badge.imaging {
            background: rgba(192, 132, 252, 0.16);
            border-color: rgba(192, 132, 252, 0.35);
            color: #d8b4fe !important;
        }

        :root[data-theme="dark"] .online-badge.idle {
            background: rgba(148, 163, 184, 0.18);
            border-color: rgba(148, 163, 184, 0.35);
            color: #cbd5e1 !important;
        }

        :root[data-theme="dark"] .online-total {
            background: rgba(74, 222, 128, 0.16);
            border-color: rgba(74, 222, 128, 0.35);
            color: #86efac !important;
        }

        @media (max-width: 640px) {
            .online-badges {
                gap: 4px;
                margin-left: 4px;
            }
            .online-badge,
            .online-total {
                font-size: 9px;
                padding: 1px 6px;
            }
        }

        /* ==================== 消息中的图片 ==================== */
        .message-image {
            margin: 10px 0;
            border-radius: 14px;
            overflow: hidden;
            border: 1px solid var(--line-soft);
            background: var(--panel-muted);
            max-width: 600px;
        }

        .message-image img {
            display: block;
            width: 100%;
            height: auto;
            cursor: zoom-in;
            border-radius: 0;
        }

        .image-meta {
            padding: 10px 12px;
            border-top: 1px solid var(--line-soft);
        }

        .image-prompt {
            display: block;
            font-size: 13px;
            color: var(--muted);
            margin-bottom: 8px;
            line-height: 1.45;
            word-break: break-word;
        }

        .image-actions {
            display: flex;
            gap: 6px;
            flex-wrap: wrap;
        }

        .image-actions button {
            padding: 5px 11px;
            font-size: 12px;
            border-radius: 999px;
            border: 1px solid var(--line);
            background: var(--panel);
            color: var(--text);
            cursor: pointer;
            transition: all .15s ease;
        }

        .image-actions button:hover {
            background: var(--blue-soft);
            border-color: rgba(0, 113, 227, .28);
            color: var(--blue);
        }

        /* ==================== 图片灯箱 ==================== */
        .image-lightbox {
            display: none;
            position: fixed;
            inset: 0;
            background: rgba(0, 0, 0, .92);
            z-index: 2000;
            align-items: center;
            justify-content: center;
            padding: 30px;
        }

        .image-lightbox.active {
            display: flex;
        }

        .image-lightbox img {
            max-width: 92%;
            max-height: 92vh;
            border-radius: 10px;
            box-shadow: 0 20px 60px rgba(0, 0, 0, .5);
        }

        .image-lightbox-close {
            position: absolute;
            top: 18px;
            right: 22px;
            width: 44px;
            height: 44px;
            border: none;
            border-radius: 50%;
            background: rgba(255, 255, 255, .12);
            color: #fff;
            font-size: 24px;
            cursor: pointer;
            display: flex;
            align-items: center;
            justify-content: center;
        }

        .image-lightbox-close:hover {
            background: rgba(255, 255, 255, .22);
        }

        .topbar {
            position: relative;
            z-index: 60;
            min-height: 74px;
            padding: 18px 22px 20px;
            border: 1px solid color-mix(in srgb, var(--line-soft) 82%, transparent);
            border-radius: 24px;
            display: flex;
            align-items: center;
            justify-content: space-between;
            gap: 18px;
            background: color-mix(in srgb, var(--panel) 78%, transparent);
            box-shadow: inset 0 1px 0 rgba(255, 255, 255, .18), 0 14px 36px rgba(15, 23, 42, .06);
            backdrop-filter: blur(18px);
            -webkit-backdrop-filter: blur(18px);
        }

        :root[data-theme="dark"] .topbar {
            background: color-mix(in srgb, var(--panel) 88%, transparent);
            border-color: color-mix(in srgb, var(--line) 76%, transparent);
            box-shadow: inset 0 1px 0 rgba(255, 255, 255, .04), 0 16px 36px rgba(0, 0, 0, .24);
        }

        .chat-title-wrap {
            min-width: 0;
            display: flex;
            flex-direction: column;
            gap: 5px;
        }

        .chat-title {
            min-width: 0;
            overflow: hidden;
            text-overflow: ellipsis;
            white-space: nowrap;
            color: var(--text);
            font-size: 22px;
            line-height: 1.15;
            font-weight: 720;
            letter-spacing: -.04em;
        }

        .chat-subtitle {
            color: var(--muted);
            font-size: 13px;
            line-height: 1.45;
        }

        .topbar-actions {
            display: flex;
            align-items: center;
            gap: 8px;
            flex-shrink: 0;
            flex-wrap: wrap;
            justify-content: flex-end;
        }

        .status-pill {
            color: var(--text);
            font-size: 12px;
            font-weight: 600;
            min-height: 40px;
            padding: 0 14px;
            border: 1px solid color-mix(in srgb, var(--line) 88%, transparent);
            border-radius: 14px;
            background: color-mix(in srgb, var(--panel) 94%, transparent);
            max-width: 240px;
            overflow: hidden;
            text-overflow: ellipsis;
            white-space: nowrap;
            box-shadow: inset 0 1px 0 rgba(255, 255, 255, .14);
        }
        .balance-pill {
            display: inline-flex;
            align-items: center;
            color: var(--text);
            font-size: 12px;
            font-weight: 600;
            min-height: 40px;
            padding: 0 12px;
            border: 1px solid color-mix(in srgb, var(--line) 88%, transparent);
            border-radius: 14px;
            background: color-mix(in srgb, var(--panel) 94%, transparent);
            white-space: nowrap;
            box-shadow: inset 0 1px 0 rgba(255, 255, 255, .14);
            user-select: none;
        }

        .top-model-select {
            position: relative;
            max-width: 260px;
            min-width: 168px;
        }

        .thinking-mode-toggle {
            display: inline-flex;
            align-items: stretch;
            min-height: 40px;
            padding: 3px;
            border: 1px solid color-mix(in srgb, var(--line) 88%, transparent);
            border-radius: 14px;
            background: color-mix(in srgb, var(--panel) 94%, transparent);
            box-shadow: inset 0 1px 0 rgba(255, 255, 255, .14);
            gap: 2px;
            flex-shrink: 0;
        }
        .thinking-mode-btn {
            appearance: none;
            border: 0;
            background: transparent;
            color: var(--muted);
            font-size: 12px;
            font-weight: 600;
            padding: 0 12px;
            border-radius: 11px;
            cursor: pointer;
            white-space: nowrap;
        }
        .thinking-mode-btn:hover {
            color: var(--text);
        }
        .thinking-mode-btn.active {
            background: color-mix(in srgb, var(--accent, #6366f1) 18%, var(--panel));
            color: var(--text);
            box-shadow: inset 0 0 0 1px color-mix(in srgb, var(--accent, #6366f1) 40%, transparent);
        }

        .model-pill {
            display: flex;
            align-items: center;
            justify-content: space-between;
            gap: 10px;
            width: 100%;
            text-align: left;
            appearance: none;
        }

        .model-pill::after {
            content: "⌄";
            color: var(--muted-2);
            flex: 0 0 auto;
        }

        .top-model-options {
            position: absolute;
            top: calc(100% + 8px);
            right: 0;
            z-index: 50;
            display: none;
            width: min(320px, 82vw);
            max-height: 280px;
            overflow-y: auto;
            padding: 6px;
            border: 1px solid var(--line);
            border-radius: 16px;
            background: color-mix(in srgb, var(--panel) 96%, transparent);
            box-shadow: var(--shadow-pop);
            backdrop-filter: blur(18px);
            -webkit-backdrop-filter: blur(18px);
        }

        .top-model-select.open .top-model-options {
            display: block;
        }

        .messages {
            flex: 1;
            min-height: 0;
            overflow-y: auto;
            overflow-x: hidden;
            overscroll-behavior: contain;
            padding: 28px 28px 120px;
            scroll-behavior: auto;
            scrollbar-gutter: stable;
            background: var(--bg);
        }

        .messages-inner {
            width: min(920px, 100%);
            margin: 0 auto;
        }

        .empty-state {
            width: min(760px, 100%);
            margin: 9vh auto 0;
            text-align: center;
            padding: 28px 20px;
        }

        .empty-icon {
            width: 70px;
            height: 70px;
            margin: 0 auto 18px;
            border-radius: 22px;
            background: var(--panel);
            border: 1px solid var(--line-soft);
            display: flex;
            align-items: center;
            justify-content: center;
            color: var(--blue);
            font-size: 30px;
        }

        .empty-state h1 {
            margin: 0;
            font-size: clamp(34px, 5vw, 54px);
            line-height: 1.04;
            letter-spacing: -.055em;
            font-weight: 700;
        }

        .empty-state p {
            margin: 14px auto 0;
            max-width: 520px;
            color: var(--muted);
            font-size: 16px;
            line-height: 1.48;
        }

        @keyframes messageEnter {
            from { opacity: 0; transform: translateY(12px); }
            to { opacity: 1; transform: translateY(0); }
        }

        .message-row {
            display: grid;
            grid-template-columns: 40px minmax(0, 1fr) 40px;
            gap: 14px;
            margin: 0 0 24px;
            align-items: start;
            animation: messageEnter 0.4s cubic-bezier(0.16, 1, 0.3, 1) forwards;
        }

        .assistant.message-row {
            grid-template-columns: 40px minmax(0, 1fr) 40px;
        }

        .assistant .avatar {
            grid-column: 1;
        }

        .assistant .message-block {
            grid-column: 2;
            text-align: left;
        }

        .assistant .message-card {
            margin-right: auto;
            margin-left: 0;
        }

        .user.message-row {
            grid-template-columns: 40px minmax(0, 1fr) 40px;
        }

        .user .message-block {
            grid-column: 2;
            text-align: right;
        }

        .user .message-card {
            margin-left: auto;
            margin-right: 0;
            text-align: left;
        }

        .avatar {
            width: 36px;
            height: 36px;
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 12px;
            font-weight: 700;
            background: var(--panel-muted);
            color: var(--muted);
            border: 1px solid var(--line-soft);
            user-select: none;
        }

        .user .avatar {
            grid-column: 3;
            grid-row: 1;
            background: var(--text);
            color: var(--bg);
            border-color: var(--text);
        }

        .message-block {
            min-width: 0;
        }

        .role-label {
            margin: 0 0 6px;
            color: var(--muted);
            font-size: 12px;
            font-weight: 700;
            letter-spacing: .02em;
        }

        .user .role-label {
            text-align: right;
        }

        .message-card {
            width: fit-content;
            max-width: 850px;
            padding: 14px 16px;
            border: 1px solid var(--line-soft);
            border-radius: 18px;
            background: var(--panel);
            color: var(--text);
            line-height: 1.65;
            font-size: 15px;
            overflow-wrap: anywhere;
        }
        .app-shell.wide-mode .assistant .message-card {
            width: 100% !important;
            max-width: none !important;
        }
        .assistant .message-card {
            border-top-left-radius: 6px;
        }

        .user .message-card {
            background: var(--panel-muted);
            border-color: var(--line-soft);
            border-top-right-radius: 6px;
        }

        .message-actions {
            display: flex;
            gap: 8px;
            margin-top: 8px;
        }

        .user .message-actions {
            justify-content: flex-end;
        }

        .action-btn {
            min-height: 30px;
            padding: 0 10px;
            border: 1px solid var(--line);
            border-radius: 999px;
            background: var(--panel);
            color: var(--muted);
            font-size: 12px;
        }

        .action-btn:hover {
            color: var(--text);
            background: var(--page);
        }

        .action-btn.primary-action {
            color: var(--blue);
            border-color: rgba(0, 113, 227, .28);
            background: var(--blue-soft);
        }

        .action-btn.copied {
            color: var(--green);
            border-color: rgba(29, 127, 58, .35);
            background: rgba(29, 127, 58, .08);
        }

        .message-card strong {
            font-weight: 700;
            color: var(--text);
            box-shadow: inset 0 -0.55em 0 rgba(0, 113, 227, 0.2);
            border-radius: 2px;
            padding: 0 2px;
            transition: box-shadow 0.2s ease;
        }

        :root[data-theme="dark"] .message-card strong {
            box-shadow: inset 0 -0.55em 0 rgba(41, 151, 255, 0.35);
        }

        .message-card h1, .message-card h2, .message-card h3, .message-card h4, .message-card h5, .message-card h6 {
            margin: 18px 0 8px;
            line-height: 1.2;
            letter-spacing: -.03em;
        }

        .assistant .message-card h1,
        .assistant .message-card h2,
        .assistant .message-card h3 {
            color: var(--blue);
            border-bottom: 1px dashed var(--line);
            padding-bottom: 6px;
            margin-top: 24px;
        }

        .assistant .message-card h1::before { content: '✨ '; }
        .assistant .message-card h2::before { content: '📌 '; }
        .assistant .message-card h3::before { content: '🔸 '; }
        .assistant .message-card h4::before { content: '🔹 '; }

        :root[data-theme="dark"] .assistant .message-card h1,
        :root[data-theme="dark"] .assistant .message-card h2,
        :root[data-theme="dark"] .assistant .message-card h3 {
            color: var(--blue-hover);
        }

        .message-card h1:first-child, .message-card h2:first-child, .message-card h3:first-child {
            margin-top: 0;
        }

        .message-card p {
            margin: 8px 0;
        }

        .message-card p:first-child {
            margin-top: 0;
        }

        .message-card p:last-child {
            margin-bottom: 0;
        }

        .message-card ul, .message-card ol {
            margin: 8px 0;
            padding-left: 23px;
        }

        .message-card li {
            margin: 3px 0;
        }

        .message-card a {
            color: var(--blue);
            text-decoration: none;
        }

        .message-card a:hover {
            text-decoration: underline;
        }

        .message-card code {
            font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
            font-size: .92em;
            padding: 2px 5px;
            border-radius: 6px;
            background: var(--page);
            border: 1px solid var(--line-soft);
        }

        .message-content-shell {
            position: relative;
        }

        .message-content-body {
            position: relative;
        }

        .message-content-body.collapsed {
            max-height: 260px;
            overflow: hidden;
        }

        .message-content-body.collapsed::after {
            content: "";
            position: absolute;
            left: 0;
            right: 0;
            bottom: 0;
            height: 72px;
            pointer-events: none;
            background: linear-gradient(to bottom, transparent, var(--panel));
        }

        .user .message-content-body.collapsed::after {
            background: linear-gradient(to bottom, transparent, var(--panel-muted));
        }

        .message-expand-btn {
            margin-top: 8px;
            min-height: 30px;
            padding: 0 11px;
            border: 1px solid var(--line);
            border-radius: 999px;
            background: var(--panel);
            color: var(--blue);
            font-size: 12px;
            font-weight: 700;
        }

        .message-expand-btn:hover {
            background: var(--blue-soft);
            border-color: rgba(0, 113, 227, .28);
        }

        .code-block {
            position: relative;
            margin: 12px 0;
        }

        .message-card pre {
            margin: 0;
            padding: 42px 13px 13px;
            overflow-x: auto;
            background: var(--page);
            border: 1px solid var(--line-soft);
            border-radius: 12px;
        }

        .code-block::before {
            content: "";
            position: absolute;
            top: 14px;
            left: 14px;
            width: 11px;
            height: 11px;
            border-radius: 50%;
            background: #ff5f56;
            box-shadow: 18px 0 0 #ffbd2e, 36px 0 0 #27c93f;
            z-index: 2;
        }

        .message-card pre code {
            padding: 0;
            border: 0;
            background: transparent;
        }

        .code-copy-btn {
            position: absolute;
            top: 8px;
            right: 8px;
            z-index: 2;
            width: 32px;
            height: 32px;
            border: 1px solid var(--line);
            border-radius: 9px;
            background: var(--panel);
            color: var(--muted);
            display: inline-flex;
            align-items: center;
            justify-content: center;
            font-weight: 700;
            line-height: 1;
        }

        .code-copy-btn:hover {
            color: var(--text);
            background: var(--blue-soft);
            border-color: rgba(0, 113, 227, .28);
        }

        .code-copy-btn.copied {
            color: var(--green);
            border-color: rgba(29, 127, 58, .35);
            background: rgba(29, 127, 58, .08);
        }

        .message-card blockquote {
            margin: 12px 0;
            padding: 10px 14px;
            border-left: 4px solid var(--blue);
            background: var(--blue-soft);
            border-radius: 0 8px 8px 0;
            color: var(--text);
        }

        .message-card table {
            width: 100%;
            border-collapse: collapse;
            margin: 12px 0;
            font-size: 14px;
        }

        .message-card th, .message-card td {
            border: 1px solid var(--line-soft);
            padding: 8px;
            text-align: left;
        }

        .message-card th {
            background: var(--page);
        }

        .message-card img {
            max-width: 100%;
            border-radius: 12px;
        }

        .message-card hr {
            border: 0;
            border-top: 1px solid var(--line-soft);
            margin: 16px 0;
        }

        .thinking-section {
            margin-bottom: 12px;
            border: 1px solid var(--line-soft);
            border-radius: 12px;
            background: var(--panel-muted);
            overflow: hidden;
        }

        body.thinking-hidden .thinking-section {
            display: none !important;
        }

        .typing-indicator {
            display: inline-flex;
            align-items: baseline;
            gap: 4px;
            padding: 4px 2px;
            line-height: 1;
            color: var(--muted);
            font-size: 14px;
            font-weight: 500;
        }
        .typing-indicator-label {
            letter-spacing: 0.2px;
            background: linear-gradient(
                90deg,
                var(--muted) 0%,
                var(--muted) 35%,
                color-mix(in srgb, var(--accent, #6366f1) 90%, var(--text)) 50%,
                var(--muted) 65%,
                var(--muted) 100%
            );
            background-size: 220% 100%;
            -webkit-background-clip: text;
            background-clip: text;
            -webkit-text-fill-color: transparent;
            animation: typing-shimmer 1.6s linear infinite;
        }
        .typing-indicator-dots {
            display: inline-flex;
            align-items: baseline;
            gap: 2px;
            margin-left: 2px;
        }
        .typing-indicator-dots span {
            display: inline-block;
            opacity: 0.25;
            animation: typing-dot 1.2s infinite ease-in-out;
        }
        .typing-indicator-dots span:nth-child(2) { animation-delay: 0.18s; }
        .typing-indicator-dots span:nth-child(3) { animation-delay: 0.36s; }
        @keyframes typing-dot {
            0%, 80%, 100% { opacity: 0.25; transform: translateY(0); }
            40% { opacity: 1; transform: translateY(-2px); }
        }
        @keyframes typing-shimmer {
            0% { background-position: 100% 0; }
            100% { background-position: -100% 0; }
        }

        .thinking-header {
            width: 100%;
            display: flex;
            align-items: center;
            justify-content: space-between;
            gap: 12px;
            padding: 9px 11px;
            border-bottom: 1px solid var(--line-soft);
            background: var(--panel-muted);
            color: var(--muted);
            font-size: 13px;
            text-align: left;
        }

        .thinking-badge {
            font-size: 11px;
            font-weight: 600;
            color: var(--muted-2);
        }

        .thinking-content {
            max-height: 260px;
            overflow-y: auto;
            padding: 11px;
            color: var(--muted);
            font-size: 13px;
            line-height: 1.58;
        }

        .thinking-content.collapsed {
            display: none;
        }

        .composer {
            flex: 0 0 auto;
            border-top: 1px solid var(--line-soft);
            padding: 16px 28px 22px;
            background: color-mix(in srgb, var(--bg) 85%, transparent);
            backdrop-filter: blur(16px);
            -webkit-backdrop-filter: blur(16px);
            z-index: 10;
        }

        .composer-inner {
            width: min(920px, 100%);
            margin: 0 auto;
            display: grid;
            grid-template-columns: minmax(0, 1fr) auto;
            gap: 10px;
            align-items: end;
        }

        .input-wrap {
            min-width: 0;
            border: 1px solid var(--line);
            border-radius: 18px;
            background: var(--panel);
            overflow: hidden;
        }

        .chat-input {
            display: block;
            min-height: 48px;
            max-height: 180px;
            padding: 13px 15px;
            resize: none;
            font-size: 15px;
            line-height: 1.45;
        }

        .chat-input::placeholder {
            color: var(--muted-2);
        }

        .chat-input:disabled {
            color: var(--muted-2);
            background: var(--panel-muted);
        }

        .send-btn {
            min-height: 48px;
            padding: 0 22px;
            border-radius: 999px;
            background: var(--blue);
            color: #fff;
            font-weight: 600;
        }

        .send-btn:hover {
            background: var(--blue-hover);
        }

        .send-btn:disabled {
            background: var(--muted-2);
            cursor: not-allowed;
        }

        .send-btn.stop {
            background: var(--red);
        }

        .modal {
            position: fixed;
            inset: 0;
            z-index: 1000;
            display: none;
            align-items: center;
            justify-content: center;
            padding: 20px;
            background: rgba(0, 0, 0, .32);
        }

        .modal.active {
            display: flex;
        }

        .modal-content {
            width: min(520px, 100%);
            max-height: min(82vh, 760px);
            overflow-y: auto;
            background: var(--panel);
            color: var(--text);
            border-radius: 20px;
            border: 1px solid var(--line-soft);
            box-shadow: var(--shadow-pop);
            padding: 24px;
        }

        .modal-header {
            margin: 0 0 18px;
            font-size: 22px;
            line-height: 1.18;
            letter-spacing: -.035em;
            font-weight: 700;
        }

        .form-group {
            margin-bottom: 15px;
        }

        .form-label {
            display: block;
            margin: 0 0 7px;
            color: var(--text);
            font-size: 13px;
            font-weight: 700;
        }

        .form-label-row {
            display: flex;
            align-items: center;
            justify-content: space-between;
            gap: 10px;
            margin: 0 0 7px;
        }

        .form-label-row .form-label {
            margin: 0;
        }

        .buy-api-key-link {
            color: var(--red);
            font-size: 13px;
            font-weight: 700;
            text-decoration: none;
            white-space: nowrap;
        }

        .buy-api-key-link:hover {
            text-decoration: underline;
        }

        .info-text {
            margin-top: 5px;
            color: var(--muted);
            font-size: 12px;
            line-height: 1.35;
        }

        .import-export-btns, .modal-actions, .fetch-models-section, .model-mode-toggle {
            display: flex;
            gap: 9px;
        }

        .import-export-btns {
            margin-bottom: 16px;
        }

        .fetch-models-section {
            align-items: end;
            margin-bottom: 15px;
        }

        .fetch-models-section .form-group {
            margin-bottom: 0;
            flex: 1;
        }

        .model-mode-toggle {
            flex-wrap: wrap;
            padding: 10px;
            margin-bottom: 15px;
            background: var(--page);
            border-radius: 13px;
        }

        .model-mode-toggle label {
            display: inline-flex;
            gap: 6px;
            align-items: center;
            color: var(--muted);
            font-size: 13px;
            font-weight: 600;
            cursor: pointer;
        }

        .native-select-hidden {
            position: absolute;
            width: 1px;
            height: 1px;
            opacity: 0;
            pointer-events: none;
            clip-path: inset(50%);
        }

        .custom-select {
            position: relative;
        }

        .custom-select-trigger {
            width: 100%;
            min-height: 44px;
            display: flex;
            align-items: center;
            justify-content: space-between;
            gap: 12px;
            padding: 0 12px 0 14px;
            border-radius: 12px;
            border: 1px solid var(--line);
            background: var(--panel);
            color: var(--text);
            text-align: left;
        }

        .custom-select-trigger:hover {
            background: var(--page);
        }

        .custom-select-text {
            min-width: 0;
            overflow: hidden;
            text-overflow: ellipsis;
            white-space: nowrap;
            font-size: 14px;
        }

        .custom-select-arrow {
            color: var(--muted);
            font-size: 16px;
            line-height: 1;
            transition: transform .12s ease;
        }

        .custom-select.open .custom-select-arrow {
            transform: rotate(180deg);
        }

        .custom-options {
            position: absolute;
            left: 0;
            right: 0;
            top: calc(100% + 6px);
            z-index: 20;
            display: none;
            max-height: 260px;
            overflow-y: auto;
            padding: 6px;
            border: 1px solid var(--line);
            border-radius: 14px;
            background: var(--panel);
            box-shadow: var(--shadow-pop);
        }

        .custom-select.open .custom-options {
            display: block;
        }

        .modal-actions {
            justify-content: flex-end;
            margin-top: 22px;
            flex-wrap: wrap;
        }

        .btn {
            min-height: 40px;
            padding: 0 16px;
            border-radius: 999px;
            font-weight: 600;
        }

        .btn-primary, .btn-info {
            background: var(--blue);
            color: #fff;
        }

        .btn-primary:hover, .btn-info:hover {
            background: var(--blue-hover);
        }

        .btn-secondary {
            background: var(--panel);
            color: var(--text);
            border: 1px solid var(--line);
        }

        .btn-secondary:hover {
            background: var(--page);
        }

        .btn-danger {
            background: var(--red);
            color: #fff;
        }

        .small-btn {
            min-height: 34px;
            padding: 0 12px;
            font-size: 12px;
        }

        .sr-only {
            position: absolute;
            width: 1px;
            height: 1px;
            padding: 0;
            margin: -1px;
            overflow: hidden;
            clip: rect(0, 0, 0, 0);
            border: 0;
        }

        .composer-inner.file-enabled {
            grid-template-columns: auto auto minmax(0, 1fr) auto;
        }

        .attach-btn,
        .prompt-lib-btn {
            height: 48px;
            padding: 0 14px;
            border: 1px solid var(--line);
            border-radius: 999px;
            background: var(--panel);
            color: var(--text);
            font-size: 14px;
            line-height: 1;
            font-weight: 500;
            cursor: pointer;
            display: inline-flex;
            align-items: center;
            justify-content: center;
            gap: 4px;
            white-space: nowrap;
        }

        .attach-btn:hover,
        .prompt-lib-btn:hover {
            background: var(--page);
            border-color: var(--blue);
            color: var(--blue);
        }

        /* Announcement modal */
        .announcement-content {
            width: min(560px, 94vw);
            max-height: 80vh;
            display: flex;
            flex-direction: column;
        }

        .announcement-body {
            flex: 1 1 auto;
            overflow-y: auto;
            padding: 4px 2px 8px;
            font-size: 14px;
            line-height: 1.65;
            color: var(--text);
        }

        .announcement-body h1,
        .announcement-body h2,
        .announcement-body h3,
        .announcement-body h4 {
            margin: 6px 0 10px;
            color: var(--text);
        }

        .announcement-body p {
            margin: 8px 0;
        }

        .announcement-body ul,
        .announcement-body ol {
            margin: 8px 0;
            padding-left: 22px;
        }

        .announcement-body a {
            color: var(--blue);
            text-decoration: none;
        }

        .announcement-body a:hover {
            text-decoration: underline;
        }

        .announcement-body img {
            max-width: 100%;
            border-radius: 8px;
        }

        .announcement-body code {
            background: var(--panel-muted);
            padding: 1px 6px;
            border-radius: 4px;
            font-size: 13px;
        }

        .announcement-skip {
            flex: 1 1 auto;
            display: inline-flex;
            align-items: center;
            gap: 6px;
            font-size: 13px;
            color: var(--muted);
            cursor: pointer;
            user-select: none;
        }

        .announcement-skip input {
            margin: 0;
            cursor: pointer;
        }

        /* Prompt library modal */
        .prompt-lib-content {
            width: min(960px, 96vw);
            max-width: 960px;
            max-height: 88vh;
            display: flex;
            flex-direction: column;
        }

        .prompt-lib-toolbar {
            display: flex;
            gap: 10px;
            margin: 4px 0 10px;
        }

        .prompt-search-input {
            flex: 1 1 auto;
        }

        .prompt-tag-bar {
            display: flex;
            flex-wrap: wrap;
            gap: 6px;
            margin-bottom: 10px;
            max-height: 90px;
            overflow-y: auto;
            padding: 4px 0;
        }

        .prompt-tag-chip {
            display: inline-flex;
            align-items: center;
            padding: 4px 10px;
            border: 1px solid var(--line);
            border-radius: 999px;
            background: var(--panel);
            color: var(--text);
            font-size: 12px;
            cursor: pointer;
            user-select: none;
            transition: all .15s;
            font-family: inherit;
        }

        .prompt-tag-chip:hover {
            background: var(--page);
        }

        .prompt-tag-chip.active {
            background: var(--blue);
            color: #fff;
            border-color: var(--blue);
        }

        .prompt-list {
            flex: 1 1 auto;
            min-height: 320px;
            max-height: 56vh;
            overflow-y: auto;
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
            gap: 10px;
            padding: 4px;
        }

        .prompt-card {
            width: 100%;
            border: 1px solid var(--line);
            border-radius: 12px;
            background: var(--panel);
            padding: 12px 14px;
            cursor: pointer;
            transition: all .15s;
            display: flex;
            flex-direction: column;
            gap: 6px;
            color: inherit;
            font-family: inherit;
            text-align: left;
        }

        .prompt-card:hover {
            border-color: var(--blue);
            background: var(--page);
            transform: translateY(-1px);
        }

        .prompt-card-title {
            font-size: 14px;
            font-weight: 600;
            color: var(--text);
            line-height: 1.35;
        }

        .prompt-card-remark {
            font-size: 12px;
            color: var(--muted);
            line-height: 1.45;
            display: -webkit-box;
            -webkit-line-clamp: 2;
            -webkit-box-orient: vertical;
            overflow: hidden;
        }

        .prompt-card-tags {
            display: flex;
            flex-wrap: wrap;
            gap: 4px;
            margin-top: 2px;
        }

        .prompt-card-tag {
            display: inline-block;
            padding: 1px 7px;
            border-radius: 4px;
            background: var(--panel-muted);
            color: var(--muted);
            font-size: 11px;
        }

        .prompt-list-empty {
            grid-column: 1 / -1;
            text-align: center;
            color: var(--muted-2);
            padding: 40px 0;
            font-size: 13px;
        }

        .prompt-detail-meta {
            font-size: 12px;
            color: var(--muted);
            margin-bottom: 10px;
            line-height: 1.5;
        }

        @media (max-width: 600px) {
            .prompt-list {
                grid-template-columns: 1fr;
            }
        }

        .pending-files {
            width: min(920px, 100%);
            margin: 0 auto 10px;
            display: flex;
            flex-wrap: wrap;
            gap: 8px;
        }

        .file-chip {
            max-width: 260px;
            min-height: 32px;
            display: inline-flex;
            align-items: center;
            gap: 8px;
            padding: 5px 8px 5px 10px;
            border: 1px solid var(--line-soft);
            border-radius: 999px;
            background: var(--panel-muted);
            color: var(--text);
            font-size: 12px;
        }

        .file-chip-name {
            min-width: 0;
            overflow: hidden;
            text-overflow: ellipsis;
            white-space: nowrap;
        }

        .file-chip-size {
            flex: 0 0 auto;
            color: var(--muted);
        }

        .file-chip-remove {
            width: 22px;
            height: 22px;
            border: 0;
            border-radius: 50%;
            background: transparent;
            color: var(--muted);
            cursor: pointer;
        }

        .file-chip-remove:hover {
            background: var(--page);
            color: var(--text);
        }

        .message-files {
            display: flex;
            flex-wrap: wrap;
            gap: 7px;
            margin-bottom: 10px;
        }

        .message-file-pill {
            max-width: 280px;
            display: inline-flex;
            align-items: center;
            gap: 6px;
            padding: 5px 9px;
            border: 1px solid var(--line-soft);
            border-radius: 999px;
            background: var(--page);
            color: var(--muted);
            font-size: 12px;
        }

        .message-file-pill span {
            overflow: hidden;
            text-overflow: ellipsis;
            white-space: nowrap;
        }

        ::-webkit-scrollbar {
            width: 10px;
            height: 10px;
        }

        ::-webkit-scrollbar-track {
            background: transparent;
        }

        ::-webkit-scrollbar-thumb {
            background: color-mix(in srgb, var(--muted-2), transparent 28%);
            border-radius: 999px;
            border: 3px solid transparent;
            background-clip: padding-box;
        }

        ::-webkit-scrollbar-thumb:hover {
            background-color: var(--muted-2);
        }

        @media (prefers-reduced-motion: reduce) {
            * {
                transition: none !important;
                scroll-behavior: auto !important;
                animation: none !important;
            }
        }

        @media (max-width: 900px) {
            .app-shell {
                grid-template-columns: 300px minmax(0, 1fr);
            }
            .topbar { padding: 14px 18px; }
            .messages { padding: 22px 18px 120px; }
            .composer { padding: 14px 18px 18px; }
            .status-pill { max-width: 180px; }
        }

        @media (max-width: 760px) {
            .app-header {
                padding: 12px 14px 0;
            }
            .app-header-inner {
                gap: 8px;
            }
            .app-tabs-inner {
                width: 100%;
                max-width: 100%;
                justify-content: center;
            }
            .app-tab {
                flex: 1;
                min-width: 0;
                padding: 0 10px;
                font-size: 12px;
                text-align: center;
            }
            .app-tab .tab-badge-new {
                min-width: 26px;
                height: 16px;
                padding: 0 5px;
                font-size: 8px;
            }
            .site-stats {
                padding: 4px 12px 6px;
                font-size: 10px;
            }
            .message-image {
                max-width: 100%;
            }
            .image-actions {
                flex-wrap: wrap;
            }
            .sidebar-toggle-btn {
                min-height: 36px;
                padding: 0 11px;
                font-size: 12px;
            }
            .app-shell {
                display: flex;
                flex-direction: column;
            }
            .sidebar {
                flex: none;
                width: 100%;
                max-height: 28vh;
                border-right: 0;
                border-bottom: 1px solid var(--line-soft);
            }
            .main {
                flex: 1;
                min-height: 0;
            }
            .brand-area { padding: 14px 12px 10px; }
            .brand-header { margin-bottom: 10px; }
            .brand-title { font-size: 19px; }
            .conversation-list { padding: 8px; }
            .topbar {
                min-height: 62px;
                padding: 12px 14px 14px;
                border-radius: 20px;
            }
            .chat-title { font-size: 19px; }
            .chat-subtitle { display: none; }
            .status-pill { display: block; max-width: 100%; }
            .messages { padding: 16px 12px 110px; }
            .empty-state { margin-top: 4vh; }
            .composer { padding: 10px 12px 12px; }
            .modal { align-items: flex-end; padding: 10px; }
            .modal-content {
                width: 100%;
                max-height: 88vh;
                border-radius: 18px;
                padding: 20px;
            }
            .custom-options { max-height: 220px; }
        }

        @media (max-width: 560px) {
            .toolbar-row {
                display: grid;
                grid-template-columns: 1fr auto;
            }
            .settings-btn { padding: 0 12px; }
            .app-header {
                padding: 10px 12px 0;
            }
            .topbar {
                padding: 12px 14px 14px;
                flex-direction: column;
                align-items: stretch;
                gap: 10px;
            }
            .topbar-actions {
                width: 100%;
                display: grid !important;
                grid-template-columns: minmax(0, 1fr) repeat(4, auto);
                justify-content: stretch;
                align-items: center;
                gap: 8px;
            }
            .top-model-select {
                min-width: 0;
                max-width: none;
            }
            .model-pill { min-width: 0; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
            .top-model-options { left: 0; right: auto; width: min(100%, 88vw); }

            .message-row,
            .user.message-row,
            .assistant.message-row {
                grid-template-columns: 1fr;
                gap: 8px;
            }

            .avatar { display: none; }
            .user .message-block, .assistant .message-block { grid-column: auto; text-align: left; }
            .user .message-card, .assistant .message-card { width: auto; margin: 0; max-width: 100%;}
            .user .message-actions { justify-content: flex-start; }

            .composer-inner { grid-template-columns: 1fr; }
            .composer-inner.file-enabled {
                grid-template-columns: repeat(2, minmax(0, 1fr));
                grid-template-areas:
                    "prompt attach"
                    "input  input"
                    "send   send";
            }
            .composer-inner.file-enabled .prompt-lib-btn { grid-area: prompt; }
            .composer-inner.file-enabled .attach-btn { grid-area: attach; }
            .composer-inner.file-enabled .input-wrap { grid-area: input; }
            .composer-inner.file-enabled .send-btn { grid-area: send; }
            .send-btn { width: 100%; }
            .attach-btn, .prompt-lib-btn {
                min-height: 44px;
                padding: 0 12px;
                font-size: 13px;
                width: auto;
            }
            .file-chip { max-width: 100%; }
            .modal-actions .btn { flex: 1 1 auto; }
        }

        @media (max-width: 380px) {
            .brand-subtitle { display: none; }
            .brand-title { font-size: 18px; }
            .brand-logo { width: 34px; height: 34px; border-radius: 10px; }
            .brand-logo svg { width: 19px; height: 19px; }
            .empty-state h1 { font-size: 32px; }
        }

        /* ==================== 2026 interaction refresh ==================== */
        .sidebar-close-btn,
        .sidebar-backdrop {
            display: none;
        }

        .announcement-btn {
            min-width: 40px;
            min-height: 40px;
            padding: 0 12px;
            display: inline-flex;
            align-items: center;
            justify-content: center;
            gap: 6px;
            border: 1px solid var(--line);
            border-radius: 999px;
            background: var(--panel);
            color: var(--text);
            font-weight: 600;
            cursor: pointer;
        }

        .announcement-btn:hover {
            background: var(--page);
        }

        .settings-modal-content {
            width: min(620px, 100%);
            max-height: min(92vh, 820px);
        }

        .api-mode-selector {
            display: grid;
            grid-template-columns: repeat(2, minmax(0, 1fr));
            gap: 10px;
            margin-bottom: 14px;
        }

        .api-mode-card {
            min-width: 0;
            min-height: 88px;
            padding: 14px;
            display: flex;
            flex-direction: column;
            align-items: flex-start;
            justify-content: center;
            gap: 5px;
            border: 1px solid var(--line);
            border-radius: 8px;
            background: var(--panel-muted);
            color: var(--text);
            text-align: left;
            cursor: pointer;
        }

        .api-mode-card:hover {
            border-color: color-mix(in srgb, var(--blue) 45%, var(--line));
        }

        .api-mode-card.active {
            border-color: var(--blue);
            background: var(--blue-soft);
            box-shadow: 0 0 0 2px color-mix(in srgb, var(--blue) 12%, transparent);
        }

        .api-mode-card-title {
            font-size: 15px;
            font-weight: 700;
        }

        .api-mode-card-description,
        .api-mode-panel-description {
            color: var(--muted);
            font-size: 12px;
            line-height: 1.45;
        }

        .api-mode-panels {
            margin-bottom: 15px;
        }

        .api-mode-panel {
            padding: 12px 14px;
            border: 1px solid var(--line-soft);
            border-radius: 8px;
            background: var(--panel-muted);
        }

        .api-mode-panel[hidden] {
            display: none;
        }

        .api-mode-panel .form-group {
            margin-bottom: 0;
        }

        .api-mode-panel-title {
            margin-bottom: 4px;
            font-size: 13px;
            font-weight: 700;
        }

        .api-key-input-wrap {
            position: relative;
        }

        .api-key-toggle-btn {
            position: absolute;
            top: 50%;
            right: 6px;
            width: 36px;
            height: 36px;
            padding: 0;
            transform: translateY(-50%);
            border: 0;
            border-radius: 8px;
            background: transparent;
            color: var(--muted);
            cursor: pointer;
        }

        .api-key-toggle-btn:hover {
            background: var(--page);
            color: var(--text);
        }

        .api-status {
            min-height: 18px;
            margin-top: 7px;
            color: var(--muted);
            font-size: 12px;
            line-height: 1.45;
        }

        .api-status-loading {
            color: var(--blue);
        }

        .api-status-success {
            color: var(--green);
        }

        .api-status-error {
            color: var(--red);
        }

        .composer.drag-over {
            box-shadow: inset 0 3px 0 var(--blue);
            background: var(--blue-soft);
        }

        .file-chip-preview {
            width: 30px;
            height: 30px;
            flex: 0 0 30px;
            border-radius: 6px;
            object-fit: cover;
        }

        .image-file-chip {
            padding-left: 5px;
        }

        .message-image-attachment {
            width: 132px;
            min-width: 0;
            padding: 0;
            display: grid;
            grid-template-rows: 88px auto;
            overflow: hidden;
            border: 1px solid var(--line-soft);
            border-radius: 8px;
            background: var(--panel-muted);
            color: var(--text);
            cursor: zoom-in;
            text-align: left;
        }

        .message-image-attachment img {
            width: 100%;
            height: 88px;
            object-fit: cover;
        }

        .message-image-attachment span {
            min-width: 0;
            padding: 7px 8px;
            overflow: hidden;
            text-overflow: ellipsis;
            white-space: nowrap;
            font-size: 11px;
        }

        @media (max-width: 760px) {
            .app-shell {
                position: relative;
                display: grid;
                grid-template-columns: minmax(0, 1fr);
                height: 100dvh;
            }

            .sidebar {
                position: fixed;
                inset: 0 auto 0 0;
                z-index: 320;
                width: min(88vw, 340px);
                height: 100dvh;
                max-height: none;
                border-right: 1px solid var(--line);
                border-bottom: 0;
                transform: translateX(-102%);
                transition: transform .2s ease;
                box-shadow: 18px 0 48px rgba(0, 0, 0, .18);
            }

            .app-shell.mobile-sidebar-open .sidebar {
                transform: translateX(0);
            }

            .sidebar-backdrop {
                position: fixed;
                inset: 0;
                z-index: 310;
                display: block;
                opacity: 0;
                visibility: hidden;
                border: 0;
                background: rgba(0, 0, 0, .38);
                transition: opacity .2s ease, visibility .2s ease;
            }

            .app-shell.mobile-sidebar-open + .sidebar-backdrop {
                opacity: 1;
                visibility: visible;
            }

            .sidebar-close-btn {
                margin-left: auto;
                width: 44px;
                height: 44px;
                display: inline-flex;
                align-items: center;
                justify-content: center;
                border: 0;
                border-radius: 50%;
                background: var(--page);
                color: var(--text);
                font-size: 24px;
                cursor: pointer;
            }

            .main {
                width: 100%;
                height: 100dvh;
            }

            .brand-area {
                padding-top: max(14px, env(safe-area-inset-top));
            }

            .toolbar-row {
                display: grid;
                grid-template-columns: repeat(2, minmax(0, 1fr));
            }

            .new-chat-btn {
                grid-column: 1 / -1;
            }

            .announcement-btn,
            .settings-btn {
                width: 100%;
                height: 44px;
                min-height: 44px;
                padding: 0 12px;
            }

            .conversation-actions .icon-btn {
                width: 40px;
                min-width: 40px;
                height: 40px;
            }

            .settings-modal-content .modal-actions {
                position: sticky;
                bottom: 0;
                z-index: 2;
                padding-top: 10px;
                background: var(--panel);
            }

            .app-header {
                padding: max(8px, env(safe-area-inset-top)) 10px 0;
            }

            .app-tab {
                min-height: 38px;
            }

            .topbar {
                min-height: 58px;
                padding: 8px 10px 10px;
                border-radius: 14px;
                flex-direction: row;
                align-items: center;
                gap: 8px;
            }

            .chat-title-wrap {
                display: none;
            }

            .topbar-actions {
                width: 100%;
                display: grid;
                grid-template-columns: 44px minmax(0, 1fr) auto;
                gap: 7px;
                flex-wrap: nowrap;
            }

            .sidebar-toggle-btn {
                width: 44px;
                height: 44px;
                min-height: 44px;
                padding: 0;
                font-size: 18px;
            }

            .top-model-select {
                width: 100%;
                max-width: none;
                min-width: 0;
            }

            .model-pill {
                width: 100%;
                max-width: none;
                min-width: 0;
                text-align: left;
            }

            .thinking-mode-toggle {
                min-height: 44px;
            }

            .thinking-mode-btn {
                min-height: 36px;
                padding: 0 9px;
            }

            .balance-pill,
            #themeToggle,
            #widthToggle {
                display: none;
            }

            .site-stats {
                display: none;
            }

            .messages {
                padding: 12px 10px 96px;
            }

            .composer {
                padding: 8px 10px max(8px, env(safe-area-inset-bottom));
            }

            .composer-inner.file-enabled {
                display: grid;
                grid-template-columns: 44px 44px minmax(0, 1fr) 48px;
                grid-template-areas: "prompt attach input send";
                gap: 6px;
                align-items: end;
            }

            .composer-inner.file-enabled .prompt-lib-btn { grid-area: prompt; }
            .composer-inner.file-enabled .attach-btn { grid-area: attach; }
            .composer-inner.file-enabled .input-wrap { grid-area: input; }
            .composer-inner.file-enabled .send-btn { grid-area: send; }

            .attach-btn,
            .prompt-lib-btn,
            .send-btn {
                width: 44px;
                min-width: 44px;
                height: 48px;
                min-height: 48px;
                padding: 0;
                border-radius: 14px;
                font-size: 19px;
            }

            .send-btn {
                width: 48px;
                min-width: 48px;
                overflow: hidden;
                font-size: 0;
            }

            .send-btn::before {
                content: "↑";
                font-size: 22px;
                line-height: 1;
            }

            .send-btn.stop::before {
                content: "■";
                font-size: 15px;
            }

            .composer-tool-label {
                display: none;
            }

            .chat-input {
                min-height: 48px;
                padding: 12px 13px;
            }

            .pending-files {
                margin-bottom: 7px;
                flex-wrap: nowrap;
                overflow-x: auto;
                overscroll-behavior-inline: contain;
            }

            .file-chip {
                max-width: 230px;
                flex: 0 0 auto;
            }

            .modal {
                padding: 0;
            }

            .modal-content {
                max-height: min(92dvh, 820px);
                padding: 20px 18px max(20px, env(safe-area-inset-bottom));
                border-radius: 18px 18px 0 0;
                border-bottom: 0;
            }

            .api-mode-selector {
                gap: 8px;
            }

            .api-mode-card {
                min-height: 96px;
                padding: 12px;
            }

            .modal-actions .btn {
                min-height: 44px;
            }
        }

        @media (max-width: 430px) {
            .thinking-mode-btn {
                font-size: 11px;
                padding: 0 7px;
            }

            .api-mode-selector {
                grid-template-columns: 1fr;
            }

            .api-mode-card {
                min-height: 70px;
            }

            .app-tab {
                padding: 0 7px;
            }
        }

        @media (max-width: 760px) {
            .desktop-width-utility {
                display: none !important;
            }
        }

        /* ==================== ChatGPT-inspired mobile shell ==================== */
        .mobile-appbar,
        .mobile-primary-nav,
        .mobile-sidebar-footer,
        .mobile-tools-btn,
        .mobile-modal-close {
            display: none;
        }

        .action-btn svg {
            width: 16px;
            height: 16px;
            fill: none;
            stroke: currentColor;
            stroke-width: 1.9;
            stroke-linecap: round;
            stroke-linejoin: round;
            vertical-align: middle;
        }

        .announcement-btn svg,
        .settings-btn svg,
        .sidebar-close-btn svg,
        .icon-btn svg {
            width: 17px;
            height: 17px;
            flex: 0 0 auto;
            fill: none;
            stroke: currentColor;
            stroke-width: 1.9;
            stroke-linecap: round;
            stroke-linejoin: round;
        }

        @media (max-width: 760px) {
            :root {
                --mobile-soft: #f4f4f4;
                --mobile-soft-hover: #ececec;
                --mobile-composer-shadow: 0 8px 28px rgba(0, 0, 0, .08);
            }

            :root[data-theme="dark"] {
                --mobile-soft: #242424;
                --mobile-soft-hover: #303030;
                --mobile-composer-shadow: 0 10px 30px rgba(0, 0, 0, .32);
            }

            .app-shell {
                position: relative;
                display: grid;
                grid-template-columns: minmax(0, 1fr);
                width: 100%;
                height: 100dvh;
                background: var(--bg);
            }

            .main {
                width: 100%;
                height: 100dvh;
                background: var(--bg);
            }

            .app-header {
                min-height: calc(52px + env(safe-area-inset-top));
                padding: env(safe-area-inset-top) 8px 0;
                border: 0;
                border-bottom: 1px solid color-mix(in srgb, var(--line-soft) 68%, transparent);
                background: color-mix(in srgb, var(--bg) 94%, transparent);
                box-shadow: none;
                backdrop-filter: blur(14px);
                -webkit-backdrop-filter: blur(14px);
            }

            .app-header-inner {
                display: none;
            }

            .mobile-appbar {
                width: 100%;
                height: 52px;
                display: grid;
                grid-template-columns: 44px minmax(0, 1fr) 44px;
                align-items: center;
                gap: 4px;
            }

            .mobile-appbar-btn,
            .mobile-model-button {
                appearance: none;
                border: 0;
                background: transparent;
                color: var(--text);
                cursor: pointer;
                -webkit-tap-highlight-color: transparent;
            }

            .mobile-appbar-btn {
                width: 44px;
                height: 44px;
                padding: 0;
                display: inline-flex;
                align-items: center;
                justify-content: center;
                border-radius: 50%;
            }

            .mobile-appbar-btn:active,
            .mobile-model-button:active {
                background: var(--mobile-soft);
                transform: scale(.97);
            }

            .mobile-appbar-btn svg,
            .mobile-model-button svg,
            .mobile-nav-item svg,
            .mobile-sidebar-utility svg,
            .mobile-tools-btn svg,
            .mobile-modal-close svg,
            .mobile-sheet-close svg,
            .mobile-tool-icon svg,
            .announcement-btn svg,
            .settings-btn svg,
            .sidebar-close-btn svg {
                fill: none;
                stroke: currentColor;
                stroke-width: 1.9;
                stroke-linecap: round;
                stroke-linejoin: round;
            }

            .mobile-appbar-btn svg {
                width: 22px;
                height: 22px;
            }

            .mobile-appbar-center {
                min-width: 0;
                display: flex;
                align-items: center;
                justify-content: center;
            }

            .mobile-model-button {
                min-width: 0;
                max-width: 100%;
                min-height: 40px;
                padding: 0 10px;
                display: inline-flex;
                align-items: center;
                justify-content: center;
                gap: 4px;
                border-radius: 12px;
                font-size: 15px;
                line-height: 1;
                font-weight: 650;
                letter-spacing: -.015em;
            }

            .mobile-model-button[hidden],
            .mobile-section-title[hidden] {
                display: none !important;
            }

            .mobile-model-button span {
                min-width: 0;
                overflow: hidden;
                text-overflow: ellipsis;
                white-space: nowrap;
            }

            .mobile-model-button svg {
                width: 18px;
                height: 18px;
                flex: 0 0 auto;
            }

            .mobile-section-title {
                min-width: 0;
                overflow: hidden;
                text-overflow: ellipsis;
                white-space: nowrap;
                color: var(--text);
                font-size: 16px;
                font-weight: 650;
                letter-spacing: -.02em;
            }

            .topbar {
                display: none;
            }

            .site-stats {
                display: none;
            }

            /* Drawer: navigation first, history second, utilities last. */
            .sidebar {
                position: fixed;
                inset: 0 auto 0 0;
                z-index: 320;
                width: min(86vw, 320px);
                height: 100dvh;
                max-height: none;
                display: flex;
                border: 0;
                border-right: 1px solid color-mix(in srgb, var(--line-soft) 74%, transparent);
                background: color-mix(in srgb, var(--panel-muted) 96%, var(--bg) 4%);
                box-shadow: 18px 0 54px rgba(0, 0, 0, .14);
                transform: translateX(-102%);
                transition: transform .24s cubic-bezier(.2, .8, .2, 1);
            }

            .app-shell.mobile-sidebar-open .sidebar {
                transform: translateX(0);
            }

            .sidebar-backdrop {
                position: fixed;
                inset: 0;
                z-index: 310;
                display: block;
                opacity: 0;
                visibility: hidden;
                border: 0;
                background: rgba(0, 0, 0, .34);
                backdrop-filter: blur(1px);
                -webkit-backdrop-filter: blur(1px);
                transition: opacity .2s ease, visibility .2s ease;
            }

            .app-shell.mobile-sidebar-open + .sidebar-backdrop {
                opacity: 1;
                visibility: visible;
            }

            .brand-area {
                padding: max(14px, env(safe-area-inset-top)) 10px 8px;
                border: 0;
            }

            .brand-header {
                min-height: 44px;
                margin: 0 2px 10px;
                gap: 10px;
            }

            .brand-logo {
                width: 32px;
                height: 32px;
                border-radius: 10px;
                box-shadow: none;
            }

            .brand-logo svg {
                width: 18px;
                height: 18px;
            }

            .brand-logo-glow,
            .brand-subtitle {
                display: none;
            }

            .brand-title {
                font-size: 17px;
                font-weight: 650;
            }

            .sidebar-close-btn {
                width: 40px;
                height: 40px;
                margin-left: auto;
                display: inline-flex;
                border-radius: 50%;
                background: transparent;
                color: var(--muted);
                font-size: 24px;
            }

            .sidebar-close-btn svg {
                width: 20px;
                height: 20px;
            }

            .conversation-actions .icon-btn svg {
                width: 16px;
                height: 16px;
            }

            .toolbar-row {
                display: grid;
                grid-template-columns: repeat(2, minmax(0, 1fr));
                gap: 2px;
            }

            .new-chat-btn,
            .announcement-btn,
            .settings-btn {
                width: 100%;
                min-height: 42px;
                padding: 0 10px;
                display: inline-flex;
                align-items: center;
                justify-content: flex-start;
                border: 0;
                border-radius: 10px;
                background: transparent;
                color: var(--text);
                font-size: 14px;
                font-weight: 520;
                box-shadow: none;
            }

            .new-chat-btn {
                grid-column: 1 / -1;
                gap: 9px;
            }

            .new-chat-btn::before {
                content: "+";
                width: 20px;
                color: var(--text);
                font-size: 22px;
                line-height: 1;
                font-weight: 350;
                text-align: center;
            }

            .new-chat-btn:hover,
            .announcement-btn:hover,
            .settings-btn:hover,
            .new-chat-btn:active,
            .announcement-btn:active,
            .settings-btn:active {
                background: var(--mobile-soft);
                color: var(--text);
            }

            .mobile-primary-nav {
                margin-top: 8px;
                padding-top: 8px;
                display: grid;
                gap: 2px;
                border-top: 1px solid color-mix(in srgb, var(--line-soft) 72%, transparent);
            }

            .mobile-nav-item,
            .mobile-sidebar-utility {
                width: 100%;
                min-height: 44px;
                padding: 0 10px;
                display: flex;
                align-items: center;
                gap: 10px;
                border: 0;
                border-radius: 10px;
                background: transparent;
                color: var(--text);
                text-align: left;
                font-size: 14px;
                cursor: pointer;
            }

            .mobile-nav-item:hover,
            .mobile-nav-item:active,
            .mobile-nav-item.active,
            .mobile-sidebar-utility:hover,
            .mobile-sidebar-utility:active {
                background: var(--mobile-soft);
            }

            .mobile-nav-item svg,
            .mobile-sidebar-utility svg {
                width: 20px;
                height: 20px;
                flex: 0 0 20px;
            }

            .mobile-nav-badge {
                margin-left: auto;
                color: var(--muted);
                font-size: 9px;
                font-weight: 700;
                letter-spacing: .08em;
            }

            .conversation-list {
                padding: 8px 10px;
                scrollbar-gutter: auto;
            }

            .conversation-item {
                min-height: 44px;
                padding: 8px 8px 8px 10px;
                margin: 0 0 2px;
                border: 0;
                border-radius: 10px;
                gap: 4px;
            }

            .conversation-item:hover,
            .conversation-item.active {
                border: 0;
                background: var(--mobile-soft);
            }

            .conversation-title {
                font-size: 13px;
                font-weight: 500;
            }

            .conversation-meta {
                display: none;
            }

            .conversation-actions {
                max-width: 0;
                gap: 0;
                overflow: hidden;
                opacity: 0;
                transition: opacity .16s ease, max-width .16s ease;
            }

            .conversation-item.active .conversation-actions,
            .conversation-item:focus-within .conversation-actions {
                max-width: 108px;
                opacity: 1;
            }

            .conversation-actions .icon-btn {
                width: 36px;
                min-width: 36px;
                height: 36px;
                border-radius: 9px;
                font-size: 16px;
            }

            .mobile-sidebar-footer {
                flex: 0 0 auto;
                display: grid;
                gap: 2px;
                padding: 8px 10px max(10px, env(safe-area-inset-bottom));
                border-top: 1px solid color-mix(in srgb, var(--line-soft) 72%, transparent);
            }

            .mobile-sidebar-status {
                min-height: 30px;
                padding: 6px 10px 0 40px;
                color: var(--muted);
                font-size: 11px;
                overflow: hidden;
                text-overflow: ellipsis;
                white-space: nowrap;
            }

            /* Chat messages use whitespace for hierarchy; only user text is a bubble. */
            .messages {
                padding: 22px 16px 28px;
                background: var(--bg);
                scrollbar-gutter: auto;
                overscroll-behavior-y: contain;
            }

            .messages-inner {
                width: min(680px, 100%);
            }

            .message-row,
            .user.message-row,
            .assistant.message-row {
                display: grid;
                grid-template-columns: minmax(0, 1fr);
                gap: 0;
                margin: 0 0 26px;
                animation-duration: .24s;
            }

            .avatar,
            .role-label {
                display: none;
            }

            .assistant .message-block,
            .user .message-block {
                grid-column: 1;
                min-width: 0;
                text-align: left;
            }

            .assistant .message-card {
                width: 100%;
                max-width: none;
                margin: 0;
                padding: 0;
                border: 0;
                border-radius: 0;
                background: transparent;
                font-size: 15px;
                line-height: 1.68;
            }

            .user .message-block {
                display: flex;
                flex-direction: column;
                align-items: flex-end;
            }

            .user .message-card {
                width: fit-content;
                max-width: 86%;
                margin: 0;
                padding: 10px 14px;
                border: 0;
                border-radius: 20px;
                border-top-right-radius: 6px;
                background: var(--mobile-soft);
                font-size: 15px;
                line-height: 1.55;
            }

            .message-actions {
                min-height: 36px;
                margin-top: 4px;
                gap: 0;
            }

            .user .message-actions {
                justify-content: flex-end;
            }

            .action-btn,
            .action-btn.primary-action,
            .action-btn.copied {
                min-width: 36px;
                min-height: 36px;
                padding: 0 8px;
                border: 0;
                border-radius: 9px;
                background: transparent;
                color: var(--muted);
                font-size: 12px;
            }

            .action-btn:hover,
            .action-btn:active,
            .action-btn.primary-action:hover {
                border: 0;
                background: var(--mobile-soft);
                color: var(--text);
            }

            .message-card strong,
            :root[data-theme="dark"] .message-card strong {
                padding: 0;
                border-radius: 0;
                box-shadow: none;
            }

            .assistant .message-card h1,
            .assistant .message-card h2,
            .assistant .message-card h3,
            :root[data-theme="dark"] .assistant .message-card h1,
            :root[data-theme="dark"] .assistant .message-card h2,
            :root[data-theme="dark"] .assistant .message-card h3 {
                padding-bottom: 0;
                border: 0;
                color: var(--text);
            }

            .assistant .message-card h1::before,
            .assistant .message-card h2::before,
            .assistant .message-card h3::before,
            .assistant .message-card h4::before {
                content: none;
            }

            .message-card h1 { font-size: 22px; }
            .message-card h2 { font-size: 19px; }
            .message-card h3 { font-size: 17px; }

            .assistant .message-content-body.collapsed::after {
                background: linear-gradient(to bottom, transparent, var(--bg));
            }

            .thinking-section {
                margin: 0 0 14px;
                border: 0;
                border-radius: 12px;
                background: var(--mobile-soft);
            }

            .thinking-header {
                min-height: 42px;
            }

            .message-card pre {
                max-width: 100%;
                border-color: color-mix(in srgb, var(--line-soft) 76%, transparent);
                border-radius: 12px;
            }

            .empty-state {
                width: 100%;
                margin: min(18vh, 138px) auto 0;
                padding: 16px 8px;
            }

            .empty-icon {
                width: auto;
                height: auto;
                margin: 0 auto 15px;
                border: 0;
                border-radius: 0;
                background: transparent;
                color: var(--text);
                font-size: 25px;
            }

            .empty-state h1 {
                font-size: 28px;
                line-height: 1.16;
                letter-spacing: -.04em;
                font-weight: 650;
            }

            .empty-state p {
                margin-top: 9px;
                font-size: 14px;
                line-height: 1.5;
            }

            /* One composer surface, matching mobile chat conventions. */
            .composer {
                padding: 8px 12px max(8px, env(safe-area-inset-bottom));
                border: 0;
                background: linear-gradient(180deg, transparent 0, color-mix(in srgb, var(--bg) 92%, transparent) 24%, var(--bg) 52%);
                backdrop-filter: none;
                -webkit-backdrop-filter: none;
            }

            .composer-inner.file-enabled {
                width: min(680px, 100%);
                display: grid;
                grid-template-columns: 40px minmax(0, 1fr) 40px;
                grid-template-areas: "mobile-tools input send";
                align-items: end;
                gap: 3px;
                padding: 5px;
                border: 1px solid color-mix(in srgb, var(--line) 70%, transparent);
                border-radius: 26px;
                background: var(--panel);
                box-shadow: var(--mobile-composer-shadow);
            }

            .mobile-tools-btn {
                grid-area: mobile-tools;
                width: 40px;
                height: 40px;
                padding: 0;
                display: inline-flex;
                align-items: center;
                justify-content: center;
                border: 0;
                border-radius: 50%;
                background: transparent;
                color: var(--text);
                cursor: pointer;
            }

            .mobile-tools-btn:hover,
            .mobile-tools-btn:active {
                background: var(--mobile-soft);
            }

            .mobile-tools-btn svg {
                width: 22px;
                height: 22px;
            }

            .composer-inner.file-enabled .prompt-lib-btn,
            .composer-inner.file-enabled .attach-btn {
                display: none;
            }

            .composer-inner.file-enabled .input-wrap {
                grid-area: input;
            }

            .input-wrap,
            .input-wrap:focus-within {
                min-width: 0;
                border: 0;
                border-radius: 0;
                background: transparent;
                box-shadow: none;
            }

            .chat-input {
                min-height: 40px;
                max-height: 124px;
                padding: 9px 7px 8px;
                background: transparent;
                font-size: 16px;
                line-height: 1.42;
            }

            .composer-inner.file-enabled .send-btn {
                grid-area: send;
            }

            .send-btn {
                width: 40px;
                min-width: 40px;
                height: 40px;
                min-height: 40px;
                padding: 0;
                overflow: hidden;
                border-radius: 50%;
                background: var(--text);
                color: var(--bg);
                font-size: 0;
                box-shadow: none;
            }

            .send-btn:hover,
            .send-btn:active {
                background: color-mix(in srgb, var(--text) 86%, var(--bg));
            }

            .send-btn::before {
                content: "↑";
                font-size: 22px;
                line-height: 1;
                font-weight: 600;
            }

            .send-btn.stop::before {
                content: "■";
                font-size: 13px;
            }

            .send-btn:disabled {
                background: var(--muted-2);
                color: var(--bg);
            }

            .pending-files {
                width: min(680px, 100%);
                margin: 0 auto 7px;
                padding: 0 2px;
                flex-wrap: nowrap;
                overflow-x: auto;
                scrollbar-width: none;
                overscroll-behavior-inline: contain;
            }

            .pending-files::-webkit-scrollbar {
                display: none;
            }

            .file-chip {
                max-width: 230px;
                flex: 0 0 auto;
                border: 0;
                background: var(--mobile-soft);
            }

            /* Mobile sheets and full-screen settings. */
            .modal {
                align-items: flex-end;
                padding: 0;
                background: rgba(0, 0, 0, .34);
            }

            .modal-content {
                width: 100%;
                max-height: 92dvh;
                padding: 20px 18px max(20px, env(safe-area-inset-bottom));
                border: 0;
                border-radius: 24px 24px 0 0;
                box-shadow: 0 -10px 40px rgba(0, 0, 0, .16);
            }

            .modal-content:not(.settings-modal-content):not(.mobile-control-sheet)::before {
                content: "";
                display: block;
                width: 36px;
                height: 4px;
                margin: -8px auto 14px;
                border-radius: 999px;
                background: color-mix(in srgb, var(--muted-2) 45%, transparent);
            }

            .settings-modal-content {
                width: 100%;
                height: 100dvh;
                max-height: 100dvh;
                padding: max(16px, env(safe-area-inset-top)) 18px max(18px, env(safe-area-inset-bottom));
                border-radius: 0;
                box-shadow: none;
            }

            .modal-header-row {
                position: sticky;
                top: 0;
                z-index: 4;
                min-height: 46px;
                margin: -4px 0 12px;
                display: flex;
                align-items: center;
                justify-content: space-between;
                gap: 12px;
                background: var(--panel);
            }

            .modal-header-row .modal-header {
                margin: 0;
                font-size: 22px;
            }

            .mobile-modal-close {
                width: 40px;
                height: 40px;
                padding: 0;
                display: inline-flex;
                align-items: center;
                justify-content: center;
                border: 0;
                border-radius: 50%;
                background: var(--mobile-soft);
                color: var(--text);
                cursor: pointer;
            }

            .mobile-modal-close svg {
                width: 20px;
                height: 20px;
            }

            .settings-modal-content .import-export-btns {
                justify-content: flex-end;
                margin: 0 0 14px;
            }

            .settings-modal-content .import-export-btns .btn {
                min-height: 34px;
                padding: 0 9px;
                border: 0;
                background: transparent;
                color: var(--muted);
                font-size: 12px;
            }

            .api-mode-selector,
            .settings-modal-content .api-mode-selector {
                grid-template-columns: repeat(2, minmax(0, 1fr));
                gap: 3px;
                padding: 3px;
                margin-bottom: 16px;
                border-radius: 13px;
                background: var(--mobile-soft);
            }

            .api-mode-card,
            .settings-modal-content .api-mode-card {
                min-height: 42px;
                padding: 0 10px;
                align-items: center;
                border: 0;
                border-radius: 10px;
                background: transparent;
                text-align: center;
                box-shadow: none;
            }

            .api-mode-card.active,
            .settings-modal-content .api-mode-card.active {
                border: 0;
                background: var(--panel);
                box-shadow: 0 1px 3px rgba(0, 0, 0, .09);
            }

            .api-mode-card-title {
                font-size: 13px;
                font-weight: 650;
            }

            .api-mode-card-description {
                display: none;
            }

            .api-mode-panel {
                padding: 0;
                border: 0;
                border-radius: 0;
                background: transparent;
            }

            .api-mode-panels {
                margin-bottom: 18px;
            }

            .fetch-models-section {
                display: block;
            }

            .settings-modal-content .modal-actions {
                position: sticky;
                bottom: 0;
                z-index: 4;
                margin: 18px -18px calc(-1 * max(18px, env(safe-area-inset-bottom)));
                padding: 12px 18px max(14px, env(safe-area-inset-bottom));
                background: color-mix(in srgb, var(--panel) 94%, transparent);
                border-top: 1px solid color-mix(in srgb, var(--line-soft) 72%, transparent);
                backdrop-filter: blur(14px);
                -webkit-backdrop-filter: blur(14px);
            }

            .settings-modal-content .modal-actions .btn {
                min-height: 46px;
            }

            .prompt-lib-content {
                max-height: 92dvh;
                padding-left: 16px;
                padding-right: 16px;
            }

            .prompt-lib-toolbar {
                margin-bottom: 8px;
            }

            .prompt-search-input {
                min-height: 44px;
                border: 0;
                border-radius: 12px;
                background: var(--mobile-soft);
            }

            .prompt-tag-bar {
                max-height: none;
                margin: 0 -16px 8px;
                padding: 2px 16px 8px;
                flex-wrap: nowrap;
                overflow-x: auto;
                overflow-y: hidden;
                scrollbar-width: none;
            }

            .prompt-tag-bar::-webkit-scrollbar {
                display: none;
            }

            .prompt-tag-chip {
                flex: 0 0 auto;
                min-height: 34px;
                padding: 0 12px;
                border: 0;
                background: var(--mobile-soft);
            }

            .prompt-tag-chip.active {
                background: var(--text);
                color: var(--bg);
            }

            .prompt-list {
                min-height: 280px;
                max-height: 61dvh;
                display: block;
                padding: 0;
            }

            .prompt-card {
                min-height: 70px;
                padding: 13px 2px;
                gap: 4px;
                border: 0;
                border-bottom: 1px solid color-mix(in srgb, var(--line-soft) 74%, transparent);
                border-radius: 0;
                background: transparent;
            }

            .prompt-card:hover,
            .prompt-card:active {
                border-color: color-mix(in srgb, var(--line-soft) 74%, transparent);
                background: transparent;
                transform: none;
            }

            .prompt-card-title {
                font-size: 15px;
                font-weight: 600;
            }

            .prompt-card-tags {
                margin-top: 3px;
            }

            .prompt-card-tag {
                padding: 1px 6px;
                border-radius: 5px;
                background: var(--mobile-soft);
            }

            .prompt-lib-content > .modal-actions {
                display: none;
            }

            .mobile-sheet-modal.active {
                display: flex;
            }

            .mobile-control-sheet {
                max-height: min(84dvh, 680px);
                padding-top: 9px;
            }

            .mobile-sheet-handle {
                width: 36px;
                height: 4px;
                margin: 0 auto 14px;
                border-radius: 999px;
                background: color-mix(in srgb, var(--muted-2) 45%, transparent);
            }

            .mobile-sheet-header {
                min-height: 44px;
                margin-bottom: 14px;
                display: flex;
                align-items: center;
                justify-content: space-between;
                gap: 12px;
            }

            .mobile-sheet-title {
                font-size: 18px;
                line-height: 1.25;
                font-weight: 650;
                letter-spacing: -.025em;
            }

            .mobile-sheet-subtitle {
                margin-top: 3px;
                color: var(--muted);
                font-size: 12px;
                line-height: 1.4;
            }

            .mobile-sheet-close {
                width: 40px;
                height: 40px;
                flex: 0 0 40px;
                padding: 0;
                display: inline-flex;
                align-items: center;
                justify-content: center;
                border: 0;
                border-radius: 50%;
                background: var(--mobile-soft);
                color: var(--text);
                cursor: pointer;
            }

            .mobile-sheet-close svg {
                width: 20px;
                height: 20px;
            }

            .mobile-sheet-section-label {
                margin: 13px 0 7px;
                color: var(--muted);
                font-size: 11px;
                font-weight: 650;
                letter-spacing: .08em;
                text-transform: uppercase;
            }

            .mobile-model-options {
                max-height: 34dvh;
                overflow-y: auto;
                border-top: 1px solid color-mix(in srgb, var(--line-soft) 72%, transparent);
            }

            .mobile-model-option {
                width: 100%;
                min-height: 46px;
                padding: 0 2px;
                display: flex;
                align-items: center;
                justify-content: space-between;
                gap: 12px;
                border: 0;
                border-bottom: 1px solid color-mix(in srgb, var(--line-soft) 72%, transparent);
                background: transparent;
                color: var(--text);
                font-size: 14px;
                text-align: left;
                cursor: pointer;
            }

            .mobile-model-option.selected {
                font-weight: 650;
            }

            .mobile-model-option.selected::after {
                content: "✓";
                color: var(--text);
                font-size: 15px;
            }

            .mobile-model-empty {
                padding: 16px 2px;
                color: var(--muted);
                font-size: 13px;
                line-height: 1.5;
            }

            .mobile-mode-toggle {
                display: grid;
                grid-template-columns: repeat(3, minmax(0, 1fr));
                gap: 3px;
                padding: 3px;
                border-radius: 14px;
                background: var(--mobile-soft);
            }

            .mobile-mode-toggle .thinking-mode-btn {
                min-width: 0;
                min-height: 54px;
                padding: 7px 10px;
                display: flex;
                flex-direction: column;
                align-items: flex-start;
                justify-content: center;
                gap: 2px;
                border: 0;
                border-radius: 11px;
                background: transparent;
                color: var(--muted);
                text-align: left;
                font-size: 13px;
            }

            .mobile-mode-toggle .thinking-mode-btn small {
                color: var(--muted);
                font-size: 10px;
                font-weight: 500;
            }

            .mobile-mode-toggle .thinking-mode-btn.active {
                background: var(--panel);
                color: var(--text);
                box-shadow: 0 1px 3px rgba(0, 0, 0, .09);
            }

            .mobile-sheet-settings-link {
                width: 100%;
                min-height: 44px;
                margin-top: 12px;
                border: 0;
                border-radius: 11px;
                background: transparent;
                color: var(--muted);
                font-size: 13px;
                cursor: pointer;
            }

            .mobile-sheet-settings-link:hover,
            .mobile-sheet-settings-link:active {
                background: var(--mobile-soft);
                color: var(--text);
            }

            .mobile-tools-sheet {
                max-height: none;
            }

            .mobile-tool-row {
                width: 100%;
                min-height: 68px;
                padding: 10px 2px;
                display: grid;
                grid-template-columns: 44px minmax(0, 1fr);
                gap: 12px;
                align-items: center;
                border: 0;
                border-top: 1px solid color-mix(in srgb, var(--line-soft) 72%, transparent);
                background: transparent;
                color: var(--text);
                text-align: left;
                cursor: pointer;
            }

            .mobile-tool-row:last-child {
                border-bottom: 1px solid color-mix(in srgb, var(--line-soft) 72%, transparent);
            }

            .mobile-tool-icon {
                width: 42px;
                height: 42px;
                display: inline-flex;
                align-items: center;
                justify-content: center;
                border-radius: 12px;
                background: var(--mobile-soft);
            }

            .mobile-tool-icon svg {
                width: 21px;
                height: 21px;
            }

            .mobile-tool-row > span:last-child {
                min-width: 0;
                display: flex;
                flex-direction: column;
                gap: 3px;
            }

            .mobile-tool-row strong {
                font-size: 14px;
                font-weight: 620;
            }

            .mobile-tool-row small {
                color: var(--muted);
                font-size: 12px;
                line-height: 1.35;
            }
        }

/* ==================== Persistent site statistics footer ==================== */
/* Keep the live counters in normal layout flow so they never cover chat
   messages or the composer. This final override intentionally restores the
   footer after the responsive shell rules above hide the legacy element. */
.main > .site-stats {
    display: block !important;
    width: 100%;
    min-width: 0;
    min-height: 38px;
    box-sizing: border-box;
    flex: 0 0 auto;
    padding: 7px clamp(14px, 2.5vw, 28px) 8px;
    overflow-wrap: anywhere;
    border-top: 1px solid color-mix(in srgb, var(--line-soft) 72%, transparent);
    background: color-mix(in srgb, var(--bg) 96%, var(--panel) 4%);
    color: var(--muted-2);
    font-size: 12px;
    line-height: 24px;
    letter-spacing: 0;
    text-align: center;
}

.main > .site-stats > #busuanzi_value_site_pv,
.main > .site-stats > #busuanzi_value_site_uv {
    color: var(--muted);
    font-size: 13px;
    font-variant-numeric: tabular-nums;
    font-weight: 700;
}

.main > .site-stats .online-badges {
    display: inline-flex;
    max-width: 100%;
    margin-left: 10px;
    gap: 6px;
    flex-wrap: wrap;
    align-items: center;
    justify-content: center;
    vertical-align: middle;
}

.main > .site-stats .online-badge,
.main > .site-stats .online-total {
    min-height: 24px;
    box-sizing: border-box;
    display: inline-flex;
    padding: 2px 9px;
    align-items: center;
    justify-content: center;
    gap: 4px;
    font-size: 11px;
    line-height: 18px;
    white-space: nowrap;
}

.main > .site-stats .online-total {
    margin-left: 0;
}

@media (min-width: 761px) and (max-width: 900px) {
    .main > .site-stats {
        padding-right: 10px;
        padding-left: 10px;
    }

    .main > .site-stats .online-badges {
        margin-left: 6px;
    }
}

@media (max-width: 760px) {
    .main > .site-stats {
        display: none !important;
    }
}

        @media (max-width: 390px) {
            .messages {
                padding-right: 13px;
                padding-left: 13px;
            }

            .composer {
                padding-right: 9px;
                padding-left: 9px;
            }

            .user .message-card {
                max-width: 88%;
            }

            .mobile-model-button {
                max-width: 218px;
                font-size: 14px;
            }
        }

        /* ==================== ChatGPT / Codex-inspired desktop shell ==================== */
        @media (min-width: 761px) {
            :root {
                --desktop-sidebar-width: 256px;
                --desktop-content-width: 800px;
                --desktop-content-wide: 1040px;
                --desktop-soft: #f4f4f4;
                --desktop-soft-hover: #ececec;
                --desktop-overlay: rgba(0, 0, 0, .34);
                --desktop-composer-shadow: 0 8px 28px rgba(0, 0, 0, .08);
            }

            :root[data-theme="dark"] {
                --desktop-soft: #242424;
                --desktop-soft-hover: #303030;
                --desktop-overlay: rgba(0, 0, 0, .58);
                --desktop-composer-shadow: 0 10px 34px rgba(0, 0, 0, .3);
            }

            /* Mouse clicks should not inherit a browser-specific outline. Keep a
               consistent, high-contrast ring for keyboard navigation instead. */
            button:focus,
            a[href]:focus,
            input:focus,
            textarea:focus,
            select:focus,
            [role="button"]:focus,
            [tabindex]:not([tabindex="-1"]):focus {
                outline: none;
            }

            button:focus-visible,
            a[href]:focus-visible,
            input:focus-visible,
            textarea:focus-visible,
            select:focus-visible,
            [role="button"]:focus-visible,
            [tabindex]:not([tabindex="-1"]):focus-visible {
                outline: 2px solid var(--blue);
                outline-offset: 2px;
            }

            .app-shell {
                grid-template-columns: var(--desktop-sidebar-width) minmax(0, 1fr);
                background: var(--bg);
                transition: grid-template-columns .24s cubic-bezier(.2, .8, .2, 1);
            }

            .app-shell.sidebar-collapsed {
                grid-template-columns: 0 minmax(0, 1fr);
            }

            .sidebar {
                width: 100%;
                max-height: none;
                border: 0;
                border-right: 1px solid color-mix(in srgb, var(--line-soft) 72%, transparent);
                background: color-mix(in srgb, var(--panel-muted) 96%, var(--bg) 4%);
                opacity: 1;
                transform: translateX(0);
                transition: opacity .18s ease, transform .24s cubic-bezier(.2, .8, .2, 1), border-color .18s ease;
            }

            .app-shell.sidebar-collapsed .sidebar {
                width: 100%;
                max-height: none;
                border-right-color: transparent;
                opacity: 0;
                transform: translateX(-18px);
                pointer-events: none;
            }

            .brand-area {
                padding: 10px 10px 8px;
                border: 0;
            }

            .brand-header {
                min-height: 38px;
                margin: 0 4px 8px;
                gap: 9px;
            }

            .brand-logo {
                width: 30px;
                height: 30px;
                border-radius: 9px;
                box-shadow: none;
            }

            .brand-logo svg {
                width: 17px;
                height: 17px;
            }

            .brand-logo-glow,
            .brand-subtitle,
            .sidebar-close-btn {
                display: none;
            }

            .brand-title {
                font-size: 16px;
                font-weight: 650;
                letter-spacing: -.02em;
            }

            .toolbar-row {
                display: grid;
                grid-template-columns: repeat(2, minmax(0, 1fr));
                gap: 2px;
            }

            .new-chat-btn,
            .announcement-btn,
            .settings-btn {
                width: 100%;
                min-height: 40px;
                padding: 0 10px;
                display: inline-flex;
                align-items: center;
                justify-content: flex-start;
                gap: 9px;
                border: 0;
                border-radius: 9px;
                background: transparent;
                color: var(--text);
                box-shadow: none;
                font-size: 13px;
                font-weight: 520;
            }

            .new-chat-btn {
                grid-column: 1 / -1;
            }

            .new-chat-btn::before {
                content: "+";
                width: 19px;
                flex: 0 0 19px;
                color: currentColor;
                font-size: 21px;
                line-height: 1;
                font-weight: 350;
                text-align: center;
            }

            .new-chat-btn:hover,
            .announcement-btn:hover,
            .settings-btn:hover {
                border: 0;
                background: var(--desktop-soft-hover);
                color: var(--text);
            }

            .announcement-btn svg,
            .settings-btn svg {
                width: 19px;
                height: 19px;
            }

            .mobile-primary-nav {
                margin-top: 8px;
                padding-top: 8px;
                display: grid;
                gap: 2px;
                border-top: 1px solid color-mix(in srgb, var(--line-soft) 72%, transparent);
            }

            .mobile-nav-item,
            .mobile-sidebar-utility {
                width: 100%;
                min-height: 40px;
                padding: 0 10px;
                display: flex;
                align-items: center;
                gap: 10px;
                border: 0;
                border-radius: 9px;
                background: transparent;
                color: var(--text);
                text-align: left;
                font-size: 13px;
                font-weight: 500;
                cursor: pointer;
            }

            .mobile-nav-item:hover,
            .mobile-nav-item.active,
            .mobile-sidebar-utility:hover {
                background: var(--desktop-soft-hover);
            }

            .mobile-nav-item svg,
            .mobile-sidebar-utility svg,
            .mobile-appbar-btn svg,
            .mobile-model-button svg,
            .mobile-tools-btn svg,
            .mobile-modal-close svg,
            .mobile-sheet-close svg,
            .mobile-tool-icon svg {
                fill: none;
                stroke: currentColor;
                stroke-width: 1.9;
                stroke-linecap: round;
                stroke-linejoin: round;
            }

            .mobile-nav-item svg,
            .mobile-sidebar-utility svg {
                width: 19px;
                height: 19px;
                flex: 0 0 19px;
            }

            .mobile-nav-badge {
                margin-left: auto;
                color: var(--muted);
                font-size: 9px;
                line-height: 1;
                font-weight: 700;
                letter-spacing: .08em;
            }

            .conversation-list {
                padding: 8px 10px;
                scrollbar-gutter: auto;
            }

            .conversation-item {
                grid-template-columns: minmax(0, 1fr) 96px;
                min-height: 40px;
                padding: 7px 7px 7px 10px;
                margin: 0 0 2px;
                gap: 4px;
                border: 0;
                border-radius: 9px;
            }

            .conversation-item > button:first-child {
                width: auto !important;
                min-width: 0;
                display: flex !important;
                align-items: center;
                overflow: hidden;
            }

            .conversation-item:hover,
            .conversation-item.active {
                border: 0;
                background: var(--desktop-soft-hover);
            }

            .conversation-title {
                flex: 1 1 auto;
                min-width: 0;
                overflow: hidden;
                text-overflow: ellipsis;
                white-space: nowrap;
                font-size: 13px;
                font-weight: 500;
            }

            .conversation-meta {
                display: none;
            }

            .conversation-actions {
                width: 96px;
                min-width: 96px;
                max-width: 96px;
                flex: 0 0 96px;
                gap: 3px;
                overflow: visible;
                opacity: 0;
                pointer-events: none;
                transition: opacity .16s ease;
            }

            .conversation-item:hover .conversation-actions,
            .conversation-item.active .conversation-actions,
            .conversation-item:focus-within .conversation-actions {
                opacity: 1;
                pointer-events: auto;
            }

            .conversation-actions .icon-btn {
                width: 30px;
                min-width: 30px;
                flex: 0 0 30px;
                height: 30px;
                border-radius: 8px;
            }

            .conversation-actions .icon-btn:hover {
                background: color-mix(in srgb, var(--text) 8%, transparent);
            }

            .mobile-sidebar-footer {
                flex: 0 0 auto;
                display: grid;
                gap: 2px;
                padding: 8px 10px 10px;
                border-top: 1px solid color-mix(in srgb, var(--line-soft) 72%, transparent);
            }

            .mobile-sidebar-status {
                min-height: 28px;
                padding: 6px 10px 0 39px;
                overflow: hidden;
                color: var(--muted);
                font-size: 11px;
                text-overflow: ellipsis;
                white-space: nowrap;
            }

            .main {
                background: var(--bg);
            }

            .app-header {
                height: 56px;
                min-height: 56px;
                padding: 0 14px;
                display: block;
                border: 0;
                border-bottom: 1px solid color-mix(in srgb, var(--line-soft) 68%, transparent);
                background: color-mix(in srgb, var(--bg) 94%, transparent);
                box-shadow: none;
                backdrop-filter: blur(14px);
                -webkit-backdrop-filter: blur(14px);
            }

            .app-header-inner,
            .topbar {
                display: none !important;
            }

            .mobile-appbar {
                width: 100%;
                height: 56px;
                display: grid;
                grid-template-columns: 42px minmax(0, 1fr) 42px;
                align-items: center;
                gap: 5px;
            }

            .mobile-appbar-btn,
            .mobile-model-button {
                appearance: none;
                border: 0;
                background: transparent;
                color: var(--text);
                cursor: pointer;
            }

            .mobile-appbar-btn {
                width: 40px;
                height: 40px;
                padding: 0;
                display: inline-flex;
                align-items: center;
                justify-content: center;
                border-radius: 10px;
            }

            .mobile-appbar-btn:hover,
            .mobile-model-button:hover {
                background: var(--desktop-soft);
            }

            .mobile-appbar-btn svg {
                width: 21px;
                height: 21px;
            }

            .mobile-appbar-center {
                min-width: 0;
                display: flex;
                align-items: center;
                justify-content: flex-start;
                overflow: hidden;
            }

            .mobile-model-button {
                min-width: 0;
                max-width: min(420px, 100%);
                min-height: 38px;
                padding: 0 11px;
                display: inline-flex;
                align-items: center;
                justify-content: flex-start;
                gap: 5px;
                border-radius: 10px;
                font-size: 14px;
                line-height: 1;
                font-weight: 620;
                letter-spacing: -.01em;
            }

            .mobile-model-button[hidden],
            .mobile-section-title[hidden] {
                display: none !important;
            }

            .mobile-model-button span {
                min-width: 0;
                max-width: 100%;
                flex: 0 1 auto;
                overflow: hidden;
                text-overflow: ellipsis;
                white-space: nowrap;
            }

            .mobile-model-button svg {
                width: 17px;
                height: 17px;
                flex: 0 0 17px;
            }

            .mobile-section-title {
                min-width: 0;
                overflow: hidden;
                color: var(--text);
                font-size: 15px;
                font-weight: 620;
                letter-spacing: -.02em;
                text-overflow: ellipsis;
                white-space: nowrap;
            }

            .messages {
                padding: 32px clamp(24px, 4vw, 52px) 24px;
                background: var(--bg);
                scrollbar-gutter: stable;
                scrollbar-gutter: stable both-edges;
                overscroll-behavior-y: contain;
            }

            .messages-inner,
            .composer-inner,
            .pending-files {
                width: min(var(--desktop-content-width), 100%);
            }

            .app-shell.wide-mode .messages-inner,
            .app-shell.wide-mode .composer-inner,
            .app-shell.wide-mode .pending-files {
                width: min(var(--desktop-content-wide), 100%);
            }

            .message-row,
            .user.message-row,
            .assistant.message-row {
                display: grid;
                grid-template-columns: minmax(0, 1fr);
                gap: 0;
                margin: 0 0 30px;
                animation-duration: .24s;
            }

            .avatar,
            .role-label {
                display: none;
            }

            .assistant .message-block,
            .user .message-block {
                grid-column: 1;
                min-width: 0;
                text-align: left;
            }

            .assistant .message-card {
                width: 100%;
                max-width: none;
                margin: 0;
                padding: 0;
                border: 0;
                border-radius: 0;
                background: transparent;
                font-size: 15.5px;
                line-height: 1.72;
            }

            .user .message-block {
                display: flex;
                flex-direction: column;
                align-items: flex-end;
            }

            .user .message-card {
                width: fit-content;
                max-width: min(74%, 620px);
                margin: 0;
                padding: 10px 15px;
                border: 0;
                border-radius: 20px;
                border-top-right-radius: 7px;
                background: var(--desktop-soft);
                font-size: 15px;
                line-height: 1.56;
            }

            .message-actions {
                min-height: 34px;
                margin-top: 4px;
                gap: 1px;
            }

            @media (hover: hover) and (pointer: fine) {
                .message-block {
                    position: relative;
                }

                .message-actions {
                    position: absolute;
                    top: 100%;
                    z-index: 2;
                    min-height: 30px;
                    height: 30px;
                    margin-top: 0;
                    overflow: hidden;
                    opacity: 0;
                    pointer-events: none;
                    transform: translateY(-2px);
                    transition: opacity .14s ease, transform .14s ease;
                }

                .assistant .message-actions {
                    left: 0;
                }

                .user .message-actions {
                    right: 0;
                }

                .message-block:hover .message-actions,
                .message-block:focus-within .message-actions {
                    opacity: 1;
                    pointer-events: auto;
                    transform: translateY(0);
                }

                .message-block .message-actions .action-btn {
                    min-width: 30px;
                    min-height: 30px;
                }
            }

            .user .message-actions {
                justify-content: flex-end;
            }

            .action-btn,
            .action-btn.primary-action,
            .action-btn.copied {
                min-width: 34px;
                min-height: 34px;
                padding: 0 8px;
                border: 0;
                border-radius: 8px;
                background: transparent;
                color: var(--muted);
                font-size: 12px;
            }

            .action-btn:hover,
            .action-btn.primary-action:hover {
                border: 0;
                background: var(--desktop-soft);
                color: var(--text);
            }

            .action-btn.copied {
                color: var(--green);
            }

            .message-card strong,
            :root[data-theme="dark"] .message-card strong {
                padding: 0;
                border-radius: 0;
                box-shadow: none;
            }

            .assistant .message-card h1,
            .assistant .message-card h2,
            .assistant .message-card h3,
            :root[data-theme="dark"] .assistant .message-card h1,
            :root[data-theme="dark"] .assistant .message-card h2,
            :root[data-theme="dark"] .assistant .message-card h3 {
                padding-bottom: 0;
                border: 0;
                color: var(--text);
            }

            .assistant .message-card h1::before,
            .assistant .message-card h2::before,
            .assistant .message-card h3::before,
            .assistant .message-card h4::before {
                content: none;
            }

            .message-card h1 { font-size: 24px; }
            .message-card h2 { font-size: 20px; }
            .message-card h3 { font-size: 17px; }

            .assistant .message-content-body.collapsed::after {
                background: linear-gradient(to bottom, transparent, var(--bg));
            }

            .thinking-section {
                margin: 0 0 14px;
                overflow: hidden;
                border: 0;
                border-radius: 12px;
                background: var(--desktop-soft);
            }

            .thinking-header {
                min-height: 40px;
                border-bottom-color: color-mix(in srgb, var(--line-soft) 72%, transparent);
                background: transparent;
            }

            .message-card pre {
                max-width: 100%;
                border-color: color-mix(in srgb, var(--line-soft) 76%, transparent);
                border-radius: 12px;
            }

            .empty-state {
                width: 100%;
                margin: min(18vh, 150px) auto 0;
                padding: 20px 8px;
            }

            @media (min-height: 900px) {
                .empty-state {
                    margin-top: clamp(175px, 22vh, 240px);
                }
            }

            .empty-icon {
                width: auto;
                height: auto;
                margin: 0 auto 14px;
                border: 0;
                border-radius: 0;
                background: transparent;
                color: var(--text);
                font-size: 26px;
            }

            .empty-state h1 {
                font-size: clamp(30px, 3vw, 38px);
                line-height: 1.14;
                letter-spacing: -.045em;
                font-weight: 650;
            }

            .empty-state p {
                margin-top: 9px;
                font-size: 14px;
                line-height: 1.5;
            }

            .composer {
                padding: 8px clamp(24px, 4vw, 52px) 18px;
                border: 0;
                background: linear-gradient(180deg, transparent 0, color-mix(in srgb, var(--bg) 94%, transparent) 24%, var(--bg) 54%);
                box-shadow: none;
                backdrop-filter: none;
                -webkit-backdrop-filter: none;
            }

            .composer-inner.file-enabled {
                display: grid;
                grid-template-columns: 40px minmax(0, 1fr) 40px;
                grid-template-areas: "desktop-tools input send";
                align-items: end;
                gap: 3px;
                padding: 5px;
                border: 1px solid color-mix(in srgb, var(--line) 70%, transparent);
                border-radius: 26px;
                background: var(--panel);
                box-shadow: var(--desktop-composer-shadow);
            }

            .composer-inner.file-enabled:focus-within {
                border-color: color-mix(in srgb, var(--blue) 46%, var(--line));
                box-shadow: var(--desktop-composer-shadow), 0 0 0 2px color-mix(in srgb, var(--blue) 10%, transparent);
            }

            .composer-inner.file-enabled:has(.chat-input:focus-visible) {
                border-color: var(--blue);
                box-shadow: var(--desktop-composer-shadow), 0 0 0 3px color-mix(in srgb, var(--blue) 14%, transparent);
            }

            .mobile-tools-btn {
                grid-area: desktop-tools;
                width: 40px;
                height: 40px;
                padding: 0;
                display: inline-flex;
                align-items: center;
                justify-content: center;
                border: 0;
                border-radius: 50%;
                background: transparent;
                color: var(--text);
                cursor: pointer;
            }

            .mobile-tools-btn:hover,
            .mobile-tools-btn:active {
                background: var(--desktop-soft);
            }

            .mobile-tools-btn svg {
                width: 21px;
                height: 21px;
            }

            .composer-inner.file-enabled .prompt-lib-btn,
            .composer-inner.file-enabled .attach-btn {
                display: none;
            }

            .composer-inner.file-enabled .input-wrap {
                grid-area: input;
            }

            .input-wrap,
            .input-wrap:focus-within {
                min-width: 0;
                border: 0;
                border-radius: 0;
                background: transparent;
                box-shadow: none;
            }

            .chat-input {
                min-height: 40px;
                max-height: 160px;
                padding: 9px 8px 8px;
                background: transparent;
                font-size: 15px;
                line-height: 1.46;
            }

            .composer-inner.file-enabled .chat-input:focus-visible {
                outline: none;
            }

            .composer-inner.file-enabled .send-btn {
                grid-area: send;
            }

            .send-btn {
                width: 40px;
                min-width: 40px;
                height: 40px;
                min-height: 40px;
                padding: 0;
                overflow: hidden;
                border-radius: 50%;
                background: var(--text);
                color: var(--bg);
                font-size: 0;
                box-shadow: none;
            }

            .send-btn:hover,
            .send-btn:active {
                background: color-mix(in srgb, var(--text) 86%, var(--bg));
            }

            .send-btn::before {
                content: "\2191";
                font-size: 21px;
                line-height: 1;
                font-weight: 650;
            }

            .send-btn.stop::before {
                content: "\25A0";
                font-size: 12px;
            }

            .send-btn:disabled {
                background: var(--muted-2);
                color: var(--bg);
            }

            .pending-files {
                margin: 0 auto 7px;
                padding: 0 2px;
                flex-wrap: nowrap;
                overflow-x: auto;
                scrollbar-width: none;
                overscroll-behavior-inline: contain;
            }

            .pending-files::-webkit-scrollbar {
                display: none;
            }

            .file-chip {
                max-width: 250px;
                flex: 0 0 auto;
                border: 0;
                background: var(--desktop-soft);
            }

            /* Desktop dialogs use one clean surface and low-noise controls. */
            .modal {
                align-items: center;
                padding: 20px;
                background: var(--desktop-overlay);
                backdrop-filter: blur(3px);
                -webkit-backdrop-filter: blur(3px);
            }

            .modal-content {
                width: min(540px, 100%);
                max-height: min(calc(100dvh - 40px), 780px);
                padding: 24px;
                border: 1px solid color-mix(in srgb, var(--line-soft) 82%, transparent);
                border-radius: 20px;
                background: var(--panel);
                box-shadow: 0 20px 60px rgba(0, 0, 0, .2);
            }

            .modal-header-row {
                min-height: 40px;
                margin: -2px 0 16px;
                display: flex;
                align-items: center;
                justify-content: space-between;
                gap: 12px;
            }

            .modal-header-row .modal-header {
                margin: 0;
            }

            .modal-header {
                margin-bottom: 18px;
                font-size: 21px;
                font-weight: 680;
                letter-spacing: -.035em;
            }

            .mobile-modal-close,
            .mobile-sheet-close {
                width: 36px;
                height: 36px;
                flex: 0 0 36px;
                padding: 0;
                display: inline-flex;
                align-items: center;
                justify-content: center;
                border: 0;
                border-radius: 50%;
                background: var(--desktop-soft);
                color: var(--text);
                cursor: pointer;
            }

            .mobile-modal-close:hover,
            .mobile-sheet-close:hover {
                background: var(--desktop-soft-hover);
            }

            .mobile-modal-close svg,
            .mobile-sheet-close svg {
                width: 18px;
                height: 18px;
            }

            .form-input,
            .form-select,
            .custom-select-trigger {
                min-height: 44px;
                border-color: color-mix(in srgb, var(--line) 82%, transparent);
                border-radius: 11px;
                background: color-mix(in srgb, var(--panel-muted) 54%, var(--panel));
            }

            .form-input:hover,
            .form-select:hover,
            .custom-select-trigger:hover {
                background: var(--desktop-soft);
            }

            .modal-content .form-group > .chat-input {
                min-height: 128px;
                padding: 12px 13px;
                border: 1px solid color-mix(in srgb, var(--line) 82%, transparent);
                border-radius: 11px;
                background: color-mix(in srgb, var(--panel-muted) 54%, var(--panel));
            }

            .modal-content .form-group > .chat-input:focus {
                border-color: var(--blue);
                box-shadow: 0 0 0 3px color-mix(in srgb, var(--blue) 13%, transparent);
            }

            .btn {
                min-height: 40px;
                padding: 0 15px;
                border-radius: 10px;
            }

            :root[data-theme="dark"] .btn-primary,
            :root[data-theme="dark"] .btn-info {
                background: #0b63b8;
                color: #fff;
            }

            :root[data-theme="dark"] .btn-primary:hover,
            :root[data-theme="dark"] .btn-info:hover {
                background: #09549c;
            }

            .settings-modal-content {
                width: min(640px, 100%);
                max-height: min(calc(100dvh - 40px), 820px);
                padding: 24px;
            }

            .settings-modal-content .import-export-btns {
                justify-content: flex-end;
                margin: -8px 0 14px;
            }

            .settings-modal-content .import-export-btns .btn {
                min-height: 32px;
                padding: 0 9px;
                border: 0;
                background: transparent;
                color: var(--muted);
                font-size: 12px;
            }

            .settings-modal-content .import-export-btns .btn:hover {
                background: var(--desktop-soft);
                color: var(--text);
            }

            .api-mode-selector,
            .settings-modal-content .api-mode-selector {
                grid-template-columns: repeat(2, minmax(0, 1fr));
                gap: 3px;
                padding: 3px;
                margin-bottom: 18px;
                border-radius: 13px;
                background: var(--desktop-soft);
            }

            .api-mode-card,
            .settings-modal-content .api-mode-card {
                min-height: 44px;
                padding: 0 12px;
                align-items: center;
                border: 0;
                border-radius: 10px;
                background: transparent;
                text-align: center;
                box-shadow: none;
            }

            .api-mode-card:hover,
            .settings-modal-content .api-mode-card:hover {
                border: 0;
                background: color-mix(in srgb, var(--panel) 54%, transparent);
            }

            .api-mode-card.active,
            .settings-modal-content .api-mode-card.active {
                border: 0;
                background: var(--panel);
                box-shadow: 0 1px 3px rgba(0, 0, 0, .1);
            }

            .api-mode-card-title {
                font-size: 13px;
                font-weight: 650;
            }

            .api-mode-card-description {
                display: none;
            }

            .api-mode-panels {
                margin-bottom: 18px;
            }

            .api-mode-panel {
                padding: 0;
                border: 0;
                border-radius: 0;
                background: transparent;
            }

            .fetch-models-section {
                align-items: flex-end;
            }

            .settings-modal-content .modal-actions {
                position: sticky;
                bottom: -24px;
                z-index: 3;
                margin: 20px -24px -24px;
                padding: 14px 24px;
                border-top: 1px solid color-mix(in srgb, var(--line-soft) 72%, transparent);
                background: color-mix(in srgb, var(--panel) 94%, transparent);
                backdrop-filter: blur(14px);
                -webkit-backdrop-filter: blur(14px);
            }

            .prompt-lib-content {
                width: min(920px, calc(100vw - 40px));
                max-width: 920px;
                max-height: min(calc(100dvh - 40px), 820px);
                padding: 24px;
            }

            .prompt-lib-toolbar {
                margin: 0 0 10px;
            }

            .prompt-search-input {
                border: 0;
                border-radius: 11px;
                background: var(--desktop-soft);
            }

            .prompt-search-input:focus {
                box-shadow: 0 0 0 3px color-mix(in srgb, var(--blue) 12%, transparent);
            }

            .prompt-tag-bar {
                max-height: 76px;
                margin-bottom: 8px;
                padding: 2px 0 8px;
            }

            .prompt-tag-chip {
                min-height: 30px;
                padding: 0 11px;
                border: 0;
                background: var(--desktop-soft);
            }

            .prompt-tag-chip:hover {
                background: var(--desktop-soft-hover);
            }

            .prompt-tag-chip.active {
                background: var(--text);
                color: var(--bg);
            }

            .prompt-list {
                min-height: 280px;
                max-height: min(54dvh, 520px);
                grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
                gap: 0 26px;
                padding: 0 4px;
            }

            .prompt-card {
                min-height: 92px;
                padding: 15px 4px;
                gap: 5px;
                border: 0;
                border-bottom: 1px solid color-mix(in srgb, var(--line-soft) 74%, transparent);
                border-radius: 0;
                background: transparent;
            }

            .prompt-card:hover {
                border-color: color-mix(in srgb, var(--line-soft) 74%, transparent);
                background: color-mix(in srgb, var(--desktop-soft) 58%, transparent);
                transform: none;
            }

            .prompt-card-title {
                font-size: 14px;
                font-weight: 620;
            }

            .prompt-card-tag {
                padding: 1px 6px;
                border-radius: 5px;
                background: var(--desktop-soft);
            }

            .prompt-lib-content > .modal-actions {
                margin-top: 14px;
            }

            /* The same model and tools surfaces are shared across desktop and mobile. */
            .mobile-control-sheet {
                width: min(460px, 100%);
                max-height: min(calc(100dvh - 40px), 680px);
                padding: 24px;
            }

            .mobile-sheet-handle {
                display: none;
            }

            .mobile-sheet-header {
                min-height: 40px;
                margin-bottom: 16px;
                display: flex;
                align-items: center;
                justify-content: space-between;
                gap: 12px;
            }

            .mobile-sheet-title {
                font-size: 19px;
                line-height: 1.25;
                font-weight: 660;
                letter-spacing: -.025em;
            }

            .mobile-sheet-subtitle {
                margin-top: 3px;
                color: var(--muted);
                font-size: 12px;
                line-height: 1.4;
            }

            .mobile-sheet-section-label {
                margin: 14px 0 7px;
                color: var(--muted);
                font-size: 11px;
                font-weight: 650;
                letter-spacing: .08em;
                text-transform: uppercase;
            }

            .mobile-model-options {
                max-height: 270px;
                overflow-y: auto;
                border-top: 1px solid color-mix(in srgb, var(--line-soft) 72%, transparent);
            }

            .mobile-model-option {
                width: 100%;
                min-height: 44px;
                padding: 0 3px;
                display: flex;
                align-items: center;
                justify-content: space-between;
                gap: 12px;
                border: 0;
                border-bottom: 1px solid color-mix(in srgb, var(--line-soft) 72%, transparent);
                background: transparent;
                color: var(--text);
                font-size: 13px;
                text-align: left;
                cursor: pointer;
            }

            .mobile-model-option > span {
                min-width: 0;
                flex: 1 1 auto;
                overflow-wrap: anywhere;
                word-break: break-word;
            }

            .mobile-model-option:hover {
                background: var(--desktop-soft);
            }

            .mobile-model-option.selected {
                font-weight: 650;
            }

            .mobile-model-option.selected::after {
                content: "\2713";
                flex: 0 0 auto;
                font-size: 14px;
            }

            .mobile-model-empty {
                padding: 16px 2px;
                color: var(--muted);
                font-size: 13px;
                line-height: 1.5;
            }

            .mobile-mode-toggle {
                display: grid;
                grid-template-columns: repeat(3, minmax(0, 1fr));
                gap: 3px;
                padding: 3px;
                border-radius: 13px;
                background: var(--desktop-soft);
            }

            .mobile-mode-toggle .thinking-mode-btn {
                min-width: 0;
                min-height: 52px;
                padding: 7px 10px;
                display: flex;
                flex-direction: column;
                align-items: flex-start;
                justify-content: center;
                gap: 2px;
                border: 0;
                border-radius: 10px;
                background: transparent;
                color: var(--muted);
                text-align: left;
                font-size: 13px;
            }

            .mobile-mode-toggle .thinking-mode-btn small {
                color: var(--muted);
                font-size: 10px;
                font-weight: 500;
            }

            .mobile-mode-toggle .thinking-mode-btn.active {
                background: var(--panel);
                color: var(--text);
                box-shadow: 0 1px 3px rgba(0, 0, 0, .1);
            }

            .mobile-sheet-settings-link {
                width: 100%;
                min-height: 42px;
                margin-top: 12px;
                border: 0;
                border-radius: 10px;
                background: transparent;
                color: var(--muted);
                font-size: 13px;
                cursor: pointer;
            }

            .mobile-sheet-settings-link:hover {
                background: var(--desktop-soft);
                color: var(--text);
            }

            .mobile-tools-sheet {
                width: min(430px, 100%);
            }

            .mobile-tool-row {
                width: 100%;
                min-height: 68px;
                padding: 10px 3px;
                display: grid;
                grid-template-columns: 42px minmax(0, 1fr);
                gap: 12px;
                align-items: center;
                border: 0;
                border-top: 1px solid color-mix(in srgb, var(--line-soft) 72%, transparent);
                background: transparent;
                color: var(--text);
                text-align: left;
                cursor: pointer;
            }

            .mobile-tool-row:last-child {
                border-bottom: 1px solid color-mix(in srgb, var(--line-soft) 72%, transparent);
            }

            .mobile-tool-row:hover {
                background: color-mix(in srgb, var(--desktop-soft) 76%, transparent);
            }

            .mobile-tool-icon {
                width: 40px;
                height: 40px;
                display: inline-flex;
                align-items: center;
                justify-content: center;
                border-radius: 11px;
                background: var(--desktop-soft);
            }

            .mobile-tool-icon svg {
                width: 20px;
                height: 20px;
            }

            .mobile-tool-row > span:last-child {
                min-width: 0;
                display: flex;
                flex-direction: column;
                gap: 3px;
            }

            .mobile-tool-row strong {
                font-size: 14px;
                font-weight: 620;
            }

            .mobile-tool-row small {
                color: var(--muted);
                font-size: 12px;
                line-height: 1.35;
            }
        }

/* ========================================================================== */
/* BTTL Ultra · Cyber Terminal                                                */
/* Strictly state-scoped: removing data-bttl/body class restores normal UI.   */
/* ========================================================================== */

:root[data-bttl="ultra"] {
    color-scheme: dark;
    --bttl-bg: #050908;
    --bttl-bg-raised: #07100c;
    --bttl-panel: #091510;
    --bttl-panel-strong: #0c1a14;
    --bttl-panel-soft: #10231b;
    --bttl-text: #e3fff4;
    --bttl-muted: #84aa9d;
    --bttl-muted-2: #5e8176;
    --bttl-line: rgba(70, 240, 176, .24);
    --bttl-line-soft: rgba(70, 240, 176, .12);
    --bttl-grid: rgba(70, 240, 176, .075);
    --bttl-signal: #46f0b0;
    --bttl-cyan: #45d9ff;
    --bttl-amber: #ffbd5a;
    --bttl-danger: #ff6976;
    --bttl-shadow: 0 18px 56px rgba(0, 0, 0, .44);
    --bg: var(--bttl-bg);
    --page: #030605;
    --panel: var(--bttl-panel);
    --panel-muted: var(--bttl-bg-raised);
    --text: var(--bttl-text);
    --muted: var(--bttl-muted);
    --muted-2: var(--bttl-muted-2);
    --line: rgba(70, 240, 176, .28);
    --line-soft: rgba(70, 240, 176, .13);
    --blue: var(--bttl-cyan);
    --blue-hover: #72e7ff;
    --blue-soft: rgba(69, 217, 255, .12);
    --green: var(--bttl-signal);
    --red: var(--bttl-danger);
    --mobile-soft: rgba(70, 240, 176, .075);
    --mobile-soft-hover: rgba(70, 240, 176, .13);
    --mobile-composer-shadow: 0 14px 38px rgba(0, 0, 0, .42);
    --desktop-soft: rgba(70, 240, 176, .075);
    --desktop-soft-hover: rgba(70, 240, 176, .13);
    --desktop-overlay: rgba(0, 5, 3, .76);
    --desktop-composer-shadow: 0 16px 44px rgba(0, 0, 0, .42);
}

:root[data-bttl="ultra"] body.bttl-ultra {
    background: var(--bttl-bg);
    color: var(--bttl-text);
}

:root[data-bttl="ultra"] body.bttl-ultra .app-shell {
    position: relative;
    isolation: isolate;
    background: var(--bttl-bg);
    color: var(--bttl-text);
    transition: background-color .42s ease, color .42s ease;
}

:root[data-bttl="ultra"] body.bttl-ultra .app-shell::before {
    content: "";
    position: absolute;
    z-index: 0;
    inset: 0;
    pointer-events: none;
    opacity: .16;
    background-image:
        linear-gradient(var(--bttl-grid) 1px, transparent 1px),
        linear-gradient(90deg, var(--bttl-grid) 1px, transparent 1px);
    background-size: 32px 32px;
    animation: bttl-grid-drift 18s linear infinite;
}

:root[data-bttl="ultra"] body.bttl-ultra .app-shell::after {
    content: "";
    position: absolute;
    z-index: 40;
    top: -18%;
    right: 0;
    left: 0;
    height: 18%;
    pointer-events: none;
    opacity: .1;
    background: linear-gradient(180deg,
        transparent 0%,
        rgba(69, 217, 255, .02) 34%,
        rgba(70, 240, 176, .42) 50%,
        rgba(69, 217, 255, .02) 66%,
        transparent 100%);
    box-shadow: 0 0 18px rgba(70, 240, 176, .08);
    animation: bttl-scanline-sweep 7s linear infinite;
}

:root[data-bttl="ultra"] body.bttl-ultra .app-shell > .sidebar,
:root[data-bttl="ultra"] body.bttl-ultra .app-shell > .main {
    position: relative;
    z-index: 1;
}

/* Header, active mode and status controls */
:root[data-bttl="ultra"] body.bttl-ultra .app-header,
:root[data-bttl="ultra"] body.bttl-ultra .topbar {
    border-color: var(--bttl-line-soft);
    background: rgba(5, 13, 10, .92);
    color: var(--bttl-text);
    box-shadow: inset 0 -1px 0 rgba(69, 217, 255, .06);
    backdrop-filter: blur(18px) saturate(115%);
    -webkit-backdrop-filter: blur(18px) saturate(115%);
}

:root[data-bttl="ultra"] body.bttl-ultra .mobile-appbar {
    color: var(--bttl-text);
}

:root[data-bttl="ultra"] body.bttl-ultra .mobile-appbar-center {
    min-width: 0;
    gap: 8px;
    overflow: hidden;
}

:root[data-bttl="ultra"] body.bttl-ultra .mobile-model-button,
:root[data-bttl="ultra"] body.bttl-ultra .model-pill {
    min-width: 0;
    border: 1px solid transparent;
    border-radius: 5px;
    background: transparent;
    color: var(--bttl-text);
    font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
    letter-spacing: .015em;
}

:root[data-bttl="ultra"] body.bttl-ultra .mobile-model-button:hover,
:root[data-bttl="ultra"] body.bttl-ultra .model-pill:hover {
    border-color: var(--bttl-line-soft);
    background: rgba(70, 240, 176, .06);
}

:root[data-bttl="ultra"] body.bttl-ultra #mobileModelStatus::after {
    content: " / REASONING";
    flex: 0 0 auto;
    color: var(--bttl-muted-2);
    font-size: 9px;
    font-weight: 500;
    letter-spacing: .12em;
}

:root[data-bttl="ultra"] body.bttl-ultra .model-pill::after {
    content: "/ REASONING  \2304";
    flex: 0 0 auto;
    color: var(--bttl-muted-2);
    font-size: 9px;
    font-weight: 500;
    letter-spacing: .12em;
}

:root[data-bttl="ultra"] body.bttl-ultra .mobile-appbar-btn,
:root[data-bttl="ultra"] body.bttl-ultra .theme-btn,
:root[data-bttl="ultra"] body.bttl-ultra .sidebar-toggle-btn {
    border: 1px solid transparent;
    border-radius: 5px;
    color: var(--bttl-muted);
}

:root[data-bttl="ultra"] body.bttl-ultra .mobile-appbar-btn:hover,
:root[data-bttl="ultra"] body.bttl-ultra .theme-btn:hover,
:root[data-bttl="ultra"] body.bttl-ultra .sidebar-toggle-btn:hover {
    border-color: var(--bttl-line-soft);
    background: rgba(70, 240, 176, .07);
    color: var(--bttl-signal);
}

:root[data-bttl="ultra"] body.bttl-ultra .mobile-bttl-controls {
    min-width: 0;
    flex: 0 0 auto;
    display: inline-flex;
    align-items: center;
    gap: 6px;
}

:root[data-bttl="ultra"] body.bttl-ultra .bttl-ultra-badge[hidden],
:root[data-bttl="ultra"] body.bttl-ultra .bttl-sound-toggle[hidden] {
    display: none !important;
}

:root[data-bttl="ultra"] body.bttl-ultra .bttl-ultra-badge {
    min-height: 28px;
    padding: 0 9px;
    display: inline-flex;
    align-items: center;
    gap: 7px;
    border: 1px solid var(--bttl-line);
    border-radius: 4px;
    background: linear-gradient(90deg, rgba(70, 240, 176, .12), rgba(69, 217, 255, .045));
    color: var(--bttl-signal);
    box-shadow: inset 0 0 18px rgba(70, 240, 176, .035), 0 0 14px rgba(70, 240, 176, .07);
    font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
    font-size: 10px;
    font-weight: 500;
    letter-spacing: .11em;
    white-space: nowrap;
}

:root[data-bttl="ultra"] body.bttl-ultra .bttl-ultra-signal {
    width: 7px;
    height: 7px;
    flex: 0 0 7px;
    border-radius: 50%;
    background: var(--bttl-signal);
    box-shadow: 0 0 10px var(--bttl-signal);
    animation: bttl-signal-pulse 1.8s ease-in-out infinite;
}

:root[data-bttl="ultra"] body.bttl-ultra .bttl-sound-toggle {
    position: relative;
    width: 30px;
    height: 30px;
    padding: 0;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    border: 1px solid var(--bttl-line-soft);
    border-radius: 4px;
    background: rgba(7, 16, 12, .82);
    color: var(--bttl-muted-2);
    cursor: pointer;
}

:root[data-bttl="ultra"] body.bttl-ultra .bttl-sound-toggle svg {
    width: 16px;
    height: 16px;
    fill: none;
    stroke: currentColor;
    stroke-width: 1.7;
    stroke-linecap: round;
    stroke-linejoin: round;
}

:root[data-bttl="ultra"] body.bttl-ultra .bttl-sound-toggle.active {
    border-color: var(--bttl-line);
    background: rgba(70, 240, 176, .1);
    color: var(--bttl-signal);
    box-shadow: 0 0 12px rgba(70, 240, 176, .08);
}

:root[data-bttl="ultra"] body.bttl-ultra .bttl-sound-toggle:not(.active) .bttl-sound-wave {
    opacity: .18;
}

:root[data-bttl="ultra"] body.bttl-ultra .bttl-sound-toggle:not(.active)::after {
    content: "";
    position: absolute;
    width: 17px;
    height: 1px;
    background: currentColor;
    transform: rotate(-43deg);
}

:root[data-bttl="ultra"] body.bttl-ultra .thinking-mode-btn {
    border-color: var(--bttl-line-soft);
    border-radius: 4px;
    background: rgba(7, 16, 12, .72);
    color: var(--bttl-muted);
    font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
}

:root[data-bttl="ultra"] body.bttl-ultra .thinking-mode-btn.active {
    border-color: rgba(69, 217, 255, .35);
    background: rgba(69, 217, 255, .08);
    color: var(--bttl-cyan);
}

:root[data-bttl="ultra"] body.bttl-ultra .thinking-mode-btn[data-mode="bttl"].active {
    border-color: var(--bttl-line);
    background: linear-gradient(90deg, rgba(70, 240, 176, .14), rgba(70, 240, 176, .055));
    color: var(--bttl-signal);
    box-shadow: inset 3px 0 0 var(--bttl-signal), 0 0 16px rgba(70, 240, 176, .065);
}

/* Sidebar / command workspace */
:root[data-bttl="ultra"] body.bttl-ultra .sidebar {
    border-color: var(--bttl-line-soft);
    background: rgba(7, 16, 12, .95);
    color: var(--bttl-text);
    box-shadow: inset -1px 0 0 rgba(69, 217, 255, .035);
}

:root[data-bttl="ultra"] body.bttl-ultra .brand-area {
    border-color: var(--bttl-line-soft);
    background: linear-gradient(180deg, rgba(70, 240, 176, .035), transparent);
}

:root[data-bttl="ultra"] body.bttl-ultra .brand-logo {
    border: 1px solid var(--bttl-line);
    border-radius: 5px;
    background: var(--bttl-panel-strong);
    color: var(--bttl-signal);
    box-shadow: inset 0 0 18px rgba(70, 240, 176, .08), 0 0 18px rgba(70, 240, 176, .08);
}

:root[data-bttl="ultra"] body.bttl-ultra .brand-logo-glow {
    display: block;
    opacity: .3;
    background: var(--bttl-signal);
    filter: blur(11px);
    animation: none;
}

:root[data-bttl="ultra"] body.bttl-ultra .brand-title,
:root[data-bttl="ultra"] body.bttl-ultra .brand-subtitle {
    color: var(--bttl-text);
    font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
    letter-spacing: .04em;
}

:root[data-bttl="ultra"] body.bttl-ultra .brand-subtitle {
    color: var(--bttl-muted-2);
}

:root[data-bttl="ultra"] body.bttl-ultra .new-chat-btn,
:root[data-bttl="ultra"] body.bttl-ultra .settings-btn,
:root[data-bttl="ultra"] body.bttl-ultra .announcement-btn,
:root[data-bttl="ultra"] body.bttl-ultra .mobile-sidebar-utility {
    border: 1px solid var(--bttl-line-soft);
    border-radius: 5px;
    background: rgba(70, 240, 176, .045);
    color: var(--bttl-text);
}

:root[data-bttl="ultra"] body.bttl-ultra .new-chat-btn:hover,
:root[data-bttl="ultra"] body.bttl-ultra .settings-btn:hover,
:root[data-bttl="ultra"] body.bttl-ultra .announcement-btn:hover,
:root[data-bttl="ultra"] body.bttl-ultra .mobile-sidebar-utility:hover {
    border-color: var(--bttl-line);
    background: rgba(70, 240, 176, .09);
    color: var(--bttl-signal);
}

:root[data-bttl="ultra"] body.bttl-ultra .conversation-list {
    background: transparent;
}

:root[data-bttl="ultra"] body.bttl-ultra .conversation-item {
    position: relative;
    border: 1px solid transparent;
    border-radius: 4px;
    color: var(--bttl-muted);
}

:root[data-bttl="ultra"] body.bttl-ultra .conversation-item:hover {
    border-color: var(--bttl-line-soft);
    background: rgba(70, 240, 176, .04);
    color: var(--bttl-text);
}

:root[data-bttl="ultra"] body.bttl-ultra .conversation-item.active {
    border-color: var(--bttl-line-soft);
    border-left-color: var(--bttl-signal);
    background: linear-gradient(90deg, rgba(70, 240, 176, .12), rgba(70, 240, 176, .025));
    color: var(--bttl-text);
    box-shadow: inset 2px 0 0 var(--bttl-signal);
}

:root[data-bttl="ultra"] body.bttl-ultra .conversation-item.active::after {
    content: "";
    position: absolute;
    top: 50%;
    right: 9px;
    width: 5px;
    height: 5px;
    border-radius: 50%;
    background: var(--bttl-signal);
    box-shadow: 0 0 8px var(--bttl-signal);
    transform: translateY(-50%);
}

:root[data-bttl="ultra"] body.bttl-ultra .mobile-sidebar-footer {
    border-color: var(--bttl-line-soft);
    background: rgba(5, 12, 9, .82);
}

/* BTTL keeps the command workspace focused on chat history only. */
:root[data-bttl="ultra"] body.bttl-ultra .sidebar .announcement-btn,
:root[data-bttl="ultra"] body.bttl-ultra .sidebar .settings-btn,
:root[data-bttl="ultra"] body.bttl-ultra .sidebar .mobile-primary-nav,
:root[data-bttl="ultra"] body.bttl-ultra .sidebar .mobile-sidebar-footer {
    display: none !important;
}

:root[data-bttl="ultra"] body.bttl-ultra .sidebar .new-chat-btn {
    width: 100%;
}

/* Messages and Ultra reasoning */
:root[data-bttl="ultra"] body.bttl-ultra .main,
:root[data-bttl="ultra"] body.bttl-ultra .messages {
    background: rgba(5, 9, 8, .84);
    color: var(--bttl-text);
}

:root[data-bttl="ultra"] body.bttl-ultra .messages {
    scrollbar-color: rgba(70, 240, 176, .25) transparent;
}

:root[data-bttl="ultra"] body.bttl-ultra .message-row {
    animation: bttl-message-enter .36s ease-out both;
}

:root[data-bttl="ultra"] body.bttl-ultra .user .message-card {
    border: 1px solid var(--bttl-line-soft);
    border-radius: 5px;
    border-top-right-radius: 2px;
    background: var(--bttl-panel-strong);
    color: var(--bttl-text);
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, .018);
}

:root[data-bttl="ultra"] body.bttl-ultra .assistant .message-card {
    position: relative;
    padding-left: 18px;
    border-left: 1px solid var(--bttl-line-soft);
    background: transparent;
    color: var(--bttl-text);
}

:root[data-bttl="ultra"] body.bttl-ultra .assistant .message-card::before {
    content: "";
    position: absolute;
    top: 0;
    left: -1px;
    width: 1px;
    height: 42px;
    background: linear-gradient(180deg, var(--bttl-signal), var(--bttl-cyan), transparent);
    box-shadow: 0 0 9px rgba(70, 240, 176, .28);
}

:root[data-bttl="ultra"] body.bttl-ultra .message-card,
:root[data-bttl="ultra"] body.bttl-ultra .message-card p,
:root[data-bttl="ultra"] body.bttl-ultra .message-card li,
:root[data-bttl="ultra"] body.bttl-ultra .message-card h1,
:root[data-bttl="ultra"] body.bttl-ultra .message-card h2,
:root[data-bttl="ultra"] body.bttl-ultra .message-card h3 {
    color: var(--bttl-text);
    text-shadow: none;
}

:root[data-bttl="ultra"] body.bttl-ultra .message-card a {
    color: var(--bttl-cyan);
    text-decoration-color: rgba(69, 217, 255, .42);
}

:root[data-bttl="ultra"] body.bttl-ultra .message-actions .action-btn {
    border: 1px solid transparent;
    color: var(--bttl-muted-2);
}

:root[data-bttl="ultra"] body.bttl-ultra .message-actions .action-btn:hover {
    border-color: var(--bttl-line-soft);
    background: rgba(70, 240, 176, .055);
    color: var(--bttl-signal);
}

:root[data-bttl="ultra"] body.bttl-ultra .thinking-section {
    position: relative;
    overflow: hidden;
    border: 1px solid var(--bttl-line-soft);
    border-radius: 5px;
    background: linear-gradient(135deg, rgba(70, 240, 176, .075), rgba(7, 16, 12, .9) 42%);
    box-shadow: inset 0 0 24px rgba(70, 240, 176, .025);
}

:root[data-bttl="ultra"] body.bttl-ultra .thinking-header {
    position: relative;
    min-height: 42px;
    border-bottom: 1px solid var(--bttl-line-soft);
    background: rgba(4, 11, 8, .52);
    color: var(--bttl-signal);
    font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
    letter-spacing: .08em;
}

:root[data-bttl="ultra"] body.bttl-ultra .thinking-header > span:first-child {
    font-size: 0;
}

:root[data-bttl="ultra"] body.bttl-ultra .thinking-header > span:first-child::before {
    content: "ULTRA REASONING";
    font-size: 10px;
    font-weight: 500;
    letter-spacing: .14em;
}

:root[data-bttl="ultra"] body.bttl-ultra .thinking-header::before {
    content: "";
    width: 6px;
    height: 6px;
    margin-right: 8px;
    flex: 0 0 6px;
    border-radius: 50%;
    background: var(--bttl-cyan);
    box-shadow: 0 0 9px var(--bttl-cyan);
}

:root[data-bttl="ultra"] body.bttl-ultra .thinking-header::after {
    content: "";
    position: absolute;
    right: auto;
    bottom: -1px;
    left: 0;
    width: 34%;
    height: 2px;
    background: linear-gradient(90deg, transparent, var(--bttl-cyan), var(--bttl-signal), transparent);
    transform-origin: center;
    animation: bttl-signal-pulse 1.9s ease-in-out infinite;
}

:root[data-bttl="ultra"] body.bttl-ultra .thinking-badge {
    border: 1px solid var(--bttl-line-soft);
    border-radius: 3px;
    background: rgba(70, 240, 176, .05);
    color: var(--bttl-muted);
    font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
}

:root[data-bttl="ultra"] body.bttl-ultra .thinking-content {
    background: rgba(4, 11, 8, .5);
    color: #b9d9ce;
    scrollbar-color: rgba(70, 240, 176, .24) transparent;
}

:root[data-bttl="ultra"] body.bttl-ultra .typing-indicator {
    color: var(--bttl-muted);
    font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
}

:root[data-bttl="ultra"] body.bttl-ultra .typing-indicator-label {
    animation: none;
    background: none;
    color: var(--bttl-signal);
    font-size: 0;
    letter-spacing: .12em;
    -webkit-text-fill-color: currentColor;
}

:root[data-bttl="ultra"] body.bttl-ultra .typing-indicator-label::after {
    content: "ULTRA REASONING";
    font-size: 11px;
}

:root[data-bttl="ultra"] body.bttl-ultra .typing-indicator-dots span {
    animation: none;
    color: var(--bttl-amber);
    opacity: .88;
    transform: none;
}

:root[data-bttl="ultra"] body.bttl-ultra .message-card code {
    border-color: var(--bttl-line-soft);
    background: rgba(70, 240, 176, .075);
    color: #8effd0;
    font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
}

:root[data-bttl="ultra"] body.bttl-ultra .message-card pre {
    border: 1px solid var(--bttl-line);
    border-radius: 5px;
    background: #020504;
    color: #baffdf;
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, .018);
}

:root[data-bttl="ultra"] body.bttl-ultra .message-card pre code {
    background: transparent;
    color: #baffdf;
}

:root[data-bttl="ultra"] body.bttl-ultra .code-block::before {
    background: var(--bttl-amber);
    box-shadow: 18px 0 0 var(--bttl-cyan), 36px 0 0 var(--bttl-signal);
}

:root[data-bttl="ultra"] body.bttl-ultra .code-copy-btn {
    border-color: var(--bttl-line-soft);
    border-radius: 4px;
    background: rgba(7, 16, 12, .88);
    color: var(--bttl-muted);
}

:root[data-bttl="ultra"] body.bttl-ultra .code-copy-btn:hover {
    border-color: var(--bttl-line);
    background: rgba(70, 240, 176, .09);
    color: var(--bttl-signal);
}

:root[data-bttl="ultra"] body.bttl-ultra .empty-state,
:root[data-bttl="ultra"] body.bttl-ultra .empty-state h1 {
    color: var(--bttl-text);
}

:root[data-bttl="ultra"] body.bttl-ultra .empty-icon {
    color: var(--bttl-signal);
    text-shadow: 0 0 18px rgba(70, 240, 176, .28);
}

/* Terminal composer */
:root[data-bttl="ultra"] body.bttl-ultra .composer {
    position: relative;
    padding-bottom: 30px;
    border-color: transparent;
    background: linear-gradient(180deg, transparent 0, rgba(5, 9, 8, .9) 28%, var(--bttl-bg) 62%);
}

:root[data-bttl="ultra"] body.bttl-ultra .composer::after {
    content: "BTTL ACTIVE · ENHANCED EXECUTION PATH";
    position: absolute;
    right: 0;
    bottom: 8px;
    left: 0;
    color: var(--bttl-muted-2);
    text-align: center;
    font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
    font-size: 8px;
    letter-spacing: .14em;
    pointer-events: none;
}

:root[data-bttl="ultra"] body.bttl-ultra .composer-inner.file-enabled {
    border: 1px solid var(--bttl-line);
    border-radius: 6px;
    background: rgba(7, 16, 12, .96);
    box-shadow: var(--bttl-shadow), inset 0 0 24px rgba(70, 240, 176, .025);
    transition: border-color .24s ease, box-shadow .24s ease, background-color .24s ease;
}

:root[data-bttl="ultra"] body.bttl-ultra .composer-inner.file-enabled:focus-within,
:root[data-bttl="ultra"] body.bttl-ultra .composer-inner.file-enabled:has(.chat-input:focus-visible) {
    border-color: var(--bttl-signal);
    background: rgba(8, 20, 15, .98);
    box-shadow: var(--bttl-shadow), 0 0 0 2px rgba(70, 240, 176, .09), 0 0 22px rgba(70, 240, 176, .08);
}

:root[data-bttl="ultra"] body.bttl-ultra .chat-input,
:root[data-bttl="ultra"] body.bttl-ultra .chat-input::placeholder {
    color: var(--bttl-text);
}

:root[data-bttl="ultra"] body.bttl-ultra .chat-input::placeholder {
    color: var(--bttl-muted-2);
}

:root[data-bttl="ultra"] body.bttl-ultra .mobile-tools-btn,
:root[data-bttl="ultra"] body.bttl-ultra .prompt-lib-btn,
:root[data-bttl="ultra"] body.bttl-ultra .attach-btn {
    border-radius: 4px;
    color: var(--bttl-muted);
}

:root[data-bttl="ultra"] body.bttl-ultra .mobile-tools-btn:hover,
:root[data-bttl="ultra"] body.bttl-ultra .prompt-lib-btn:hover,
:root[data-bttl="ultra"] body.bttl-ultra .attach-btn:hover {
    background: rgba(70, 240, 176, .08);
    color: var(--bttl-signal);
}

:root[data-bttl="ultra"] body.bttl-ultra .send-btn {
    border: 1px solid var(--bttl-signal);
    border-radius: 4px;
    background: var(--bttl-signal);
    color: #021008;
    box-shadow: 0 0 16px rgba(70, 240, 176, .13);
}

:root[data-bttl="ultra"] body.bttl-ultra .send-btn:hover,
:root[data-bttl="ultra"] body.bttl-ultra .send-btn:active {
    background: #79f8c8;
    color: #021008;
}

:root[data-bttl="ultra"] body.bttl-ultra .send-btn.stop {
    border-color: var(--bttl-amber);
    background: var(--bttl-amber);
    color: #1d1200;
    box-shadow: 0 0 16px rgba(255, 189, 90, .12);
}

:root[data-bttl="ultra"] body.bttl-ultra .pending-file,
:root[data-bttl="ultra"] body.bttl-ultra .file-chip {
    border-color: var(--bttl-line-soft);
    border-radius: 4px;
    background: var(--bttl-panel-strong);
    color: var(--bttl-text);
}

/* Shared overlays, controls and model/answer sheets */
:root[data-bttl="ultra"] body.bttl-ultra .modal {
    background: rgba(0, 5, 3, .78);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
}

:root[data-bttl="ultra"] body.bttl-ultra .ig-size-modal {
    background: rgba(0, 5, 3, .78);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
}

:root[data-bttl="ultra"] body.bttl-ultra .modal-content,
:root[data-bttl="ultra"] body.bttl-ultra .settings-modal-content,
:root[data-bttl="ultra"] body.bttl-ultra .prompt-lib-content,
:root[data-bttl="ultra"] body.bttl-ultra .mobile-control-sheet,
:root[data-bttl="ultra"] body.bttl-ultra .ig-size-modal-content {
    border: 1px solid var(--bttl-line);
    border-radius: 6px;
    background: var(--bttl-panel);
    color: var(--bttl-text);
    box-shadow: 0 24px 80px rgba(0, 0, 0, .58), inset 0 0 36px rgba(70, 240, 176, .018);
}

:root[data-bttl="ultra"] body.bttl-ultra .modal-header,
:root[data-bttl="ultra"] body.bttl-ultra .mobile-sheet-title,
:root[data-bttl="ultra"] body.bttl-ultra .ig-size-modal-header h3 {
    color: var(--bttl-text);
    font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
}

:root[data-bttl="ultra"] body.bttl-ultra .modal-header-row,
:root[data-bttl="ultra"] body.bttl-ultra .mobile-sheet-header,
:root[data-bttl="ultra"] body.bttl-ultra .ig-size-modal-header,
:root[data-bttl="ultra"] body.bttl-ultra .ig-size-modal-footer {
    border-color: var(--bttl-line-soft);
}

:root[data-bttl="ultra"] body.bttl-ultra .mobile-sheet-subtitle,
:root[data-bttl="ultra"] body.bttl-ultra .mobile-sheet-section-label,
:root[data-bttl="ultra"] body.bttl-ultra .form-label,
:root[data-bttl="ultra"] body.bttl-ultra .api-mode-card-description {
    color: var(--bttl-muted);
}

:root[data-bttl="ultra"] body.bttl-ultra .form-input,
:root[data-bttl="ultra"] body.bttl-ultra .form-select,
:root[data-bttl="ultra"] body.bttl-ultra .custom-select-trigger,
:root[data-bttl="ultra"] body.bttl-ultra .api-key-input-wrap,
:root[data-bttl="ultra"] body.bttl-ultra .ig-size-input,
:root[data-bttl="ultra"] body.bttl-ultra .ig-size-custom-input-wrap input {
    border-color: var(--bttl-line-soft);
    border-radius: 4px;
    background: rgba(4, 11, 8, .82);
    color: var(--bttl-text);
}

:root[data-bttl="ultra"] body.bttl-ultra .form-input:focus,
:root[data-bttl="ultra"] body.bttl-ultra .form-select:focus,
:root[data-bttl="ultra"] body.bttl-ultra .custom-select.open .custom-select-trigger,
:root[data-bttl="ultra"] body.bttl-ultra .ig-size-input:focus,
:root[data-bttl="ultra"] body.bttl-ultra .ig-size-custom-input-wrap input:focus {
    border-color: var(--bttl-signal);
    box-shadow: 0 0 0 2px rgba(70, 240, 176, .1);
}

:root[data-bttl="ultra"] body.bttl-ultra .custom-options,
:root[data-bttl="ultra"] body.bttl-ultra .top-model-options {
    border-color: var(--bttl-line);
    border-radius: 5px;
    background: var(--bttl-panel-strong);
    box-shadow: var(--bttl-shadow);
}

:root[data-bttl="ultra"] body.bttl-ultra .top-model-option:hover,
:root[data-bttl="ultra"] body.bttl-ultra .custom-option:hover,
:root[data-bttl="ultra"] body.bttl-ultra .mobile-model-option:hover {
    background: rgba(70, 240, 176, .07);
    color: var(--bttl-text);
}

:root[data-bttl="ultra"] body.bttl-ultra .top-model-option.selected,
:root[data-bttl="ultra"] body.bttl-ultra .custom-option.selected,
:root[data-bttl="ultra"] body.bttl-ultra .mobile-model-option.selected {
    background: rgba(70, 240, 176, .11);
    color: var(--bttl-signal);
    box-shadow: inset 2px 0 0 var(--bttl-signal);
}

:root[data-bttl="ultra"] body.bttl-ultra .api-mode-card,
:root[data-bttl="ultra"] body.bttl-ultra .prompt-card,
:root[data-bttl="ultra"] body.bttl-ultra .prompt-tag-chip,
:root[data-bttl="ultra"] body.bttl-ultra .mobile-sheet-settings-link {
    border-color: var(--bttl-line-soft);
    border-radius: 4px;
    background: rgba(70, 240, 176, .035);
    color: var(--bttl-text);
}

:root[data-bttl="ultra"] body.bttl-ultra .api-mode-selector {
    border: 1px solid var(--bttl-line-soft);
    border-radius: 5px;
    background: rgba(4, 11, 8, .72);
}

:root[data-bttl="ultra"] body.bttl-ultra .btn,
:root[data-bttl="ultra"] body.bttl-ultra .modal-actions .btn,
:root[data-bttl="ultra"] body.bttl-ultra #fetchModelsBtn {
    border-radius: 4px;
}

:root[data-bttl="ultra"] body.bttl-ultra .api-mode-card:hover,
:root[data-bttl="ultra"] body.bttl-ultra .prompt-card:hover,
:root[data-bttl="ultra"] body.bttl-ultra .prompt-tag-chip:hover,
:root[data-bttl="ultra"] body.bttl-ultra .mobile-sheet-settings-link:hover {
    border-color: var(--bttl-line);
    background: rgba(70, 240, 176, .075);
}

:root[data-bttl="ultra"] body.bttl-ultra .api-mode-card.active,
:root[data-bttl="ultra"] body.bttl-ultra .prompt-tag-chip.active,
:root[data-bttl="ultra"] body.bttl-ultra .btn-primary {
    border-color: var(--bttl-signal);
    background: var(--bttl-signal);
    color: #021008;
}

:root[data-bttl="ultra"] body.bttl-ultra .btn-secondary,
:root[data-bttl="ultra"] body.bttl-ultra .mobile-modal-close,
:root[data-bttl="ultra"] body.bttl-ultra .mobile-sheet-close,
:root[data-bttl="ultra"] body.bttl-ultra .api-key-toggle-btn {
    border-color: var(--bttl-line-soft);
    border-radius: 4px;
    background: rgba(70, 240, 176, .045);
    color: var(--bttl-muted);
}

/* Image generation keeps its logic; only shared shell/status chrome changes. */
:root[data-bttl="ultra"] body.bttl-ultra .image-generator-container {
    background: rgba(5, 9, 8, .86) !important;
    color: var(--bttl-text) !important;
}

:root[data-bttl="ultra"] body.bttl-ultra .ig-header h2,
:root[data-bttl="ultra"] body.bttl-ultra .ig-history-header h3 {
    color: var(--bttl-text) !important;
}

:root[data-bttl="ultra"] body.bttl-ultra .ig-header p,
:root[data-bttl="ultra"] body.bttl-ultra .ig-placeholder,
:root[data-bttl="ultra"] body.bttl-ultra .ig-history-empty,
:root[data-bttl="ultra"] body.bttl-ultra .ig-size-hint,
:root[data-bttl="ultra"] body.bttl-ultra .ig-size-current {
    color: var(--bttl-muted) !important;
}

:root[data-bttl="ultra"] body.bttl-ultra .ig-result-area,
:root[data-bttl="ultra"] body.bttl-ultra .ig-ref-add,
:root[data-bttl="ultra"] body.bttl-ultra .ig-history-item,
:root[data-bttl="ultra"] body.bttl-ultra .ig-actual-params,
:root[data-bttl="ultra"] body.bttl-ultra .ig-size-auto-hint,
:root[data-bttl="ultra"] body.bttl-ultra .ig-size-preview {
    border-color: var(--bttl-line-soft) !important;
    border-radius: 5px !important;
    background: var(--bttl-panel-strong) !important;
    color: var(--bttl-text) !important;
}

:root[data-bttl="ultra"] body.bttl-ultra .ig-tab,
:root[data-bttl="ultra"] body.bttl-ultra .ig-size-btn,
:root[data-bttl="ultra"] body.bttl-ultra .ig-clear-btn,
:root[data-bttl="ultra"] body.bttl-ultra .ig-size-mode-tab,
:root[data-bttl="ultra"] body.bttl-ultra .ig-size-tier-btn,
:root[data-bttl="ultra"] body.bttl-ultra .ig-size-ratio-btn {
    border-color: var(--bttl-line-soft) !important;
    border-radius: 4px !important;
    background: rgba(70, 240, 176, .035) !important;
    color: var(--bttl-muted) !important;
}

:root[data-bttl="ultra"] body.bttl-ultra .ig-tab.active,
:root[data-bttl="ultra"] body.bttl-ultra .ig-size-mode-tab.active,
:root[data-bttl="ultra"] body.bttl-ultra .ig-size-tier-btn.active,
:root[data-bttl="ultra"] body.bttl-ultra .ig-size-ratio-btn.active {
    border-color: var(--bttl-line) !important;
    background: rgba(70, 240, 176, .11) !important;
    color: var(--bttl-signal) !important;
    box-shadow: inset 2px 0 0 var(--bttl-signal) !important;
}

:root[data-bttl="ultra"] body.bttl-ultra .ig-gen-btn {
    border: 1px solid var(--bttl-signal) !important;
    border-radius: 4px !important;
    background: var(--bttl-signal) !important;
    color: #021008 !important;
    box-shadow: 0 0 16px rgba(70, 240, 176, .1) !important;
}

@keyframes bttl-grid-drift {
    to { background-position: 64px 32px; }
}

@keyframes bttl-scanline-sweep {
    from { transform: translateY(-110%); }
    to { transform: translateY(calc(100vh + 110%)); }
}

@keyframes bttl-signal-pulse {
    0%, 100% { opacity: .55; transform: scale(.86); }
    50% { opacity: 1; transform: scale(1); }
}

@keyframes bttl-status-scan {
    from { transform: translateX(-115%); }
    to { transform: translateX(390%); }
}

@keyframes bttl-message-enter {
    from { opacity: 0; transform: translateY(7px); }
    to { opacity: 1; transform: translateY(0); }
}

@media (max-width: 760px) {
    :root[data-bttl="ultra"] body.bttl-ultra .app-shell > .sidebar {
        position: fixed;
        z-index: 320;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .app-shell > .main {
        position: relative;
        z-index: 1;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .app-shell::before {
        opacity: .1;
        animation: none;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .app-shell::after {
        display: none;
        animation: none;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .mobile-appbar-center {
        gap: 4px;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .mobile-model-button {
        min-width: 0;
        flex: 1 1 auto;
        padding-inline: 7px;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .mobile-bttl-controls {
        flex: 0 0 auto;
        gap: 4px;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .mobile-bttl-ultra-badge {
        min-height: 26px;
        padding-inline: 7px;
        font-size: 9px;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .mobile-bttl-ultra-badge .bttl-ultra-signal {
        animation: bttl-signal-pulse 1.8s ease-in-out infinite;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .mobile-bttl-sound-toggle {
        width: 28px;
        height: 28px;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .thinking-header::after,
    :root[data-bttl="ultra"] body.bttl-ultra .brand-logo-glow,
    :root[data-bttl="ultra"] body.bttl-ultra .ig-spinner {
        animation: none;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .assistant .message-card {
        padding-left: 13px;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .composer {
        padding-bottom: 27px;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .composer::after {
        bottom: 7px;
        font-size: 7px;
        letter-spacing: .09em;
    }
}

@media (max-width: 390px) {
    :root[data-bttl="ultra"] body.bttl-ultra .mobile-appbar {
        grid-template-columns: 38px minmax(0, 1fr) 38px;
        gap: 2px;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .mobile-appbar-btn {
        width: 36px;
        height: 36px;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .mobile-model-button {
        padding-inline: 5px;
        font-size: 12px;
    }

    :root[data-bttl="ultra"] body.bttl-ultra #mobileModelStatus::after {
        font-size: 6.5px;
        letter-spacing: 0;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .mobile-bttl-ultra-badge {
        max-width: 82px;
        min-height: 24px;
        padding-inline: 5px;
        overflow: hidden;
        font-size: 8px;
        letter-spacing: .06em;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .mobile-bttl-ultra-badge .bttl-ultra-signal {
        width: 5px;
        height: 5px;
        flex-basis: 5px;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .mobile-bttl-sound-toggle {
        width: 26px;
        height: 26px;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .mobile-bttl-sound-toggle svg {
        width: 14px;
        height: 14px;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .composer::after {
        content: "BTTL ACTIVE · ENHANCED PATH";
    }
}

@media (prefers-reduced-motion: reduce) {
    :root[data-bttl="ultra"],
    :root[data-bttl="ultra"]::before,
    :root[data-bttl="ultra"]::after,
    :root[data-bttl="ultra"] body.bttl-ultra,
    :root[data-bttl="ultra"] body.bttl-ultra::before,
    :root[data-bttl="ultra"] body.bttl-ultra::after,
    :root[data-bttl="ultra"] body.bttl-ultra *,
    :root[data-bttl="ultra"] body.bttl-ultra *::before,
    :root[data-bttl="ultra"] body.bttl-ultra *::after {
        animation: none !important;
        transition: none !important;
        scroll-behavior: auto !important;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .app-shell::after {
        display: none !important;
    }
}

/* ========================================================================== */
/* BTTL mode switch                                                           */
/* The mode now lives beside the model selector; the old status badge remains */
/* visually hidden as an aria-live announcement only.                         */
/* ========================================================================== */
.bttl-mode-switch {
    appearance: none;
    min-width: 0;
    height: 30px;
    padding: 0 7px 0 8px;
    flex: 0 0 auto;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 6px;
    border: 1px solid color-mix(in srgb, var(--line) 88%, transparent);
    border-radius: 999px;
    background: color-mix(in srgb, var(--panel) 94%, transparent);
    color: var(--muted);
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, .12);
    font-size: 9px;
    font-weight: 720;
    line-height: 1;
    letter-spacing: .08em;
    white-space: nowrap;
    cursor: pointer;
    user-select: none;
    -webkit-tap-highlight-color: transparent;
    transition:
        color .22s ease,
        border-color .22s ease,
        border-radius .35s ease,
        background-color .22s ease,
        box-shadow .3s ease,
        transform .12s ease;
}

.bttl-mode-switch:hover {
    border-color: color-mix(in srgb, var(--text) 28%, var(--line));
    background: color-mix(in srgb, var(--text) 5%, var(--panel));
    color: var(--text);
}

.bttl-mode-switch:active {
    transform: scale(.97);
}

.bttl-mode-switch:focus-visible {
    outline: 2px solid var(--blue, #0071e3);
    outline-offset: 2px;
}

.bttl-mode-switch-label {
    min-width: 0;
    overflow: hidden;
    text-overflow: clip;
}

.bttl-mode-switch-track {
    position: relative;
    width: 30px;
    height: 16px;
    flex: 0 0 30px;
    overflow: hidden;
    border: 1px solid color-mix(in srgb, var(--line) 92%, transparent);
    border-radius: 999px;
    background: color-mix(in srgb, var(--muted) 15%, var(--panel));
    box-shadow: inset 0 1px 3px rgba(0, 0, 0, .13);
    transition: border-color .25s ease, background-color .25s ease, box-shadow .3s ease;
}

.bttl-mode-switch-knob {
    position: absolute;
    top: 2px;
    left: 2px;
    width: 10px;
    height: 10px;
    border-radius: 50%;
    background: var(--muted-2);
    box-shadow: 0 1px 2px rgba(0, 0, 0, .2);
    transform: translateX(0);
    transition: transform .34s cubic-bezier(.2, .85, .25, 1.15), background-color .25s ease, box-shadow .3s ease;
}

.bttl-mode-switch[aria-checked="true"] .bttl-mode-switch-knob,
:root[data-bttl="ultra"] body.bttl-ultra .bttl-mode-switch .bttl-mode-switch-knob {
    transform: translateX(14px);
}

/* Ultra-active state: compact terminal control rather than a second badge. */
:root[data-bttl="ultra"] body.bttl-ultra .bttl-mode-switch {
    border-color: var(--bttl-line);
    border-radius: 5px;
    background: linear-gradient(90deg, rgba(70, 240, 176, .11), rgba(69, 217, 255, .045));
    color: var(--bttl-signal);
    box-shadow: inset 0 0 16px rgba(70, 240, 176, .035), 0 0 13px rgba(70, 240, 176, .07);
    font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
    text-shadow: 0 0 8px rgba(70, 240, 176, .28);
}

:root[data-bttl="ultra"] body.bttl-ultra .bttl-mode-switch:hover {
    border-color: rgba(70, 240, 176, .42);
    background: linear-gradient(90deg, rgba(70, 240, 176, .16), rgba(69, 217, 255, .07));
    color: #79f8c8;
}

:root[data-bttl="ultra"] body.bttl-ultra .bttl-mode-switch:focus-visible {
    outline-color: var(--bttl-cyan);
    box-shadow: 0 0 0 2px rgba(69, 217, 255, .1), 0 0 15px rgba(70, 240, 176, .1);
}

:root[data-bttl="ultra"] body.bttl-ultra .bttl-mode-switch-track {
    border-color: rgba(69, 217, 255, .34);
    background: rgba(70, 240, 176, .13);
    box-shadow: inset 0 0 7px rgba(70, 240, 176, .12);
}

:root[data-bttl="ultra"] body.bttl-ultra .bttl-mode-switch-knob {
    background: var(--bttl-signal);
    box-shadow: 0 0 8px rgba(70, 240, 176, .72);
}

/* Keep the model, BTTL switch and optional sound control on one compact row. */
.mobile-bttl-controls {
    min-width: 0;
    flex: 0 0 auto;
    display: inline-flex;
    align-items: center;
    gap: 5px;
}

.mobile-appbar-center > .mobile-model-button {
    min-width: 0;
    flex: 0 1 auto;
}

.mobile-appbar-center > .mobile-section-title {
    min-width: 0;
    flex: 1 1 auto;
}

/* Sound is an Ultra-only sibling immediately following the switch. */
:root:not([data-bttl="ultra"]) .bttl-sound-toggle,
.bttl-sound-toggle[hidden] {
    display: none !important;
}

/* Preserve status announcements without reserving header width. */
#bttlUltraBadge:not([hidden]),
#mobileBttlUltraBadge:not([hidden]) {
    position: absolute !important;
    width: 1px !important;
    min-width: 1px !important;
    height: 1px !important;
    min-height: 0 !important;
    padding: 0 !important;
    margin: -1px !important;
    overflow: hidden !important;
    clip: rect(0, 0, 0, 0) !important;
    clip-path: inset(50%) !important;
    border: 0 !important;
    background: transparent !important;
    box-shadow: none !important;
    white-space: nowrap !important;
}

#bttlUltraBadge[hidden],
#mobileBttlUltraBadge[hidden] {
    display: none !important;
}

#bttlUltraBadge .bttl-ultra-signal,
#mobileBttlUltraBadge .bttl-ultra-signal {
    display: none !important;
    animation: none !important;
}

/* With BTTL removed from the answer sheet, Instant and Thinking share it. */
.mobile-mode-toggle {
    grid-template-columns: repeat(2, minmax(0, 1fr));
}

@media (max-width: 760px) {
    .mobile-appbar-center {
        min-width: 0;
        overflow: hidden;
    }

    .mobile-model-button {
        min-width: 0;
        max-width: none;
        flex: 0 1 auto;
        overflow: hidden;
    }

    :root[data-bttl="ultra"] body.bttl-ultra .mobile-appbar-center > .mobile-model-button {
        flex: 0 1 auto;
    }

    .mobile-bttl-controls {
        max-width: max-content;
        gap: 4px;
    }

    .bttl-mode-switch {
        height: 28px;
        padding-inline: 7px 6px;
        gap: 5px;
    }
}

@media (max-width: 390px) {
    .bttl-mode-switch {
        height: 26px;
        padding-inline: 5px;
        gap: 4px;
        font-size: 8px;
        letter-spacing: .055em;
    }

    .bttl-mode-switch-track {
        width: 28px;
        height: 15px;
        flex-basis: 28px;
    }

    .bttl-mode-switch-knob {
        width: 9px;
        height: 9px;
    }

    .mobile-bttl-controls {
        gap: 3px;
    }
}

@media (prefers-reduced-motion: reduce) {
    .bttl-mode-switch,
    .bttl-mode-switch-track,
    .bttl-mode-switch-knob {
        transition: none !important;
    }
}

/* BTTL locks model selection to the codex-5.5 execution model. */
:root[data-bttl="ultra"] body.bttl-ultra #mobileModelButton,
:root[data-bttl="ultra"] body.bttl-ultra #modelStatus,
:root[data-bttl="ultra"] body.bttl-ultra #modelSelectTrigger {
    cursor: default !important;
    border-color: var(--bttl-line-soft, rgba(70, 240, 176, .2));
    color: var(--bttl-signal, #46f0b0);
}

:root[data-bttl="ultra"] body.bttl-ultra #mobileModelButton:hover,
:root[data-bttl="ultra"] body.bttl-ultra #modelStatus:hover,
:root[data-bttl="ultra"] body.bttl-ultra #modelSelectTrigger:hover,
:root[data-bttl="ultra"] body.bttl-ultra #mobileModelButton:disabled,
:root[data-bttl="ultra"] body.bttl-ultra #modelStatus:disabled,
:root[data-bttl="ultra"] body.bttl-ultra #modelSelectTrigger:disabled {
    background: rgba(70, 240, 176, .045) !important;
    color: var(--bttl-signal, #46f0b0) !important;
    transform: none !important;
}

:root[data-bttl="ultra"] body.bttl-ultra #mobileModelButton > svg,
:root[data-bttl="ultra"] body.bttl-ultra #modelSelectTrigger .custom-select-arrow {
    display: none !important;
}

:root[data-bttl="ultra"] body.bttl-ultra #modelSelectTrigger[disabled] {
    opacity: 1;
    pointer-events: none;
}

:root[data-bttl="ultra"] body.bttl-ultra #modelOptions,
:root[data-bttl="ultra"] body.bttl-ultra #topModelOptions {
    pointer-events: none;
}

/* BTTL pins the model to gpt-5.5: keep the selector readable, but not interactive. */
:root[data-bttl="ultra"] body.bttl-ultra #modelStatus[disabled],
:root[data-bttl="ultra"] body.bttl-ultra #mobileModelButton[disabled] {
    cursor: default;
    pointer-events: none;
    opacity: .9;
}

:root[data-bttl="ultra"] body.bttl-ultra #modelStatus[disabled] {
    border-color: var(--bttl-line-soft);
    background: rgba(70, 240, 176, .055);
    color: var(--bttl-signal);
}

:root[data-bttl="ultra"] body.bttl-ultra #modelStatus[disabled]::after {
    content: "LOCKED";
    color: var(--bttl-muted-2);
    font-size: 9px;
    font-weight: 600;
    letter-spacing: .1em;
}

:root[data-bttl="ultra"] body.bttl-ultra #mobileModelButton[disabled] {
    border-color: transparent;
    background: transparent;
    color: var(--bttl-signal);
}

:root[data-bttl="ultra"] body.bttl-ultra #mobileModelButton[disabled] svg {
    display: none !important;
}

:root[data-bttl="ultra"] body.bttl-ultra #mobileModelStatus::after {
    content: " / LOCKED";
    color: var(--bttl-muted-2);
    font-size: 9px;
    font-weight: 600;
    letter-spacing: .08em;
}

/* Model lists are redundant while the Ultra model is forced. */
:root[data-bttl="ultra"] body.bttl-ultra #topModelOptions,
:root[data-bttl="ultra"] body.bttl-ultra #mobileModelOptions,
:root[data-bttl="ultra"] body.bttl-ultra #fetchModelsSection,
:root[data-bttl="ultra"] body.bttl-ultra #modelSelectGroup,
:root[data-bttl="ultra"] body.bttl-ultra #modelFetchError {
    display: none !important;
}

/* BTTL first-run guide: isolated from the standard interface until Ultra is active. */
:root[data-bttl="ultra"] .bttl-guide-modal {
    z-index: 1400;
    padding: 20px;
    background: rgba(0, 7, 4, .82);
}

:root[data-bttl="ultra"] .bttl-guide-content {
    position: relative;
    width: min(530px, 100%);
    max-height: min(82dvh, 670px);
    overflow: auto;
    padding: 28px;
    border: 1px solid var(--bttl-line, rgba(70, 240, 176, .42));
    border-radius: 7px;
    background:
        linear-gradient(135deg, rgba(70, 240, 176, .075), transparent 40%),
        var(--bttl-panel, #07120e);
    color: var(--bttl-text, #e2fff1);
    box-shadow: 0 26px 90px rgba(0, 0, 0, .68), inset 0 0 0 1px rgba(70, 240, 176, .05);
    font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
}

:root[data-bttl="ultra"] .bttl-guide-content::before {
    content: "";
    position: absolute;
    inset: 8px;
    pointer-events: none;
    border: 1px solid rgba(70, 240, 176, .12);
    border-radius: 3px;
}

:root[data-bttl="ultra"] .bttl-guide-close {
    position: absolute;
    z-index: 1;
    top: 14px;
    right: 14px;
    width: 30px;
    height: 30px;
    border: 1px solid var(--bttl-line-soft, rgba(70, 240, 176, .2));
    border-radius: 4px;
    background: rgba(70, 240, 176, .045);
    color: var(--bttl-muted, #9bbbad);
    font: 400 22px/1 ui-monospace, monospace;
    cursor: pointer;
}

:root[data-bttl="ultra"] .bttl-guide-close:hover,
:root[data-bttl="ultra"] .bttl-guide-close:focus-visible {
    border-color: var(--bttl-signal, #46f0b0);
    color: var(--bttl-signal, #46f0b0);
    outline: none;
}

:root[data-bttl="ultra"] .bttl-guide-kicker {
    position: relative;
    z-index: 1;
    display: flex;
    align-items: center;
    gap: 8px;
    margin: 0 42px 14px 0;
    color: var(--bttl-signal, #46f0b0);
    font-size: 10px;
    font-weight: 700;
    letter-spacing: .14em;
}

:root[data-bttl="ultra"] .bttl-guide-kicker span {
    width: 7px;
    height: 7px;
    border-radius: 50%;
    background: var(--bttl-signal, #46f0b0);
    box-shadow: 0 0 12px var(--bttl-signal, #46f0b0);
}

:root[data-bttl="ultra"] .bttl-guide-title {
    position: relative;
    z-index: 1;
    margin: 0;
    color: var(--bttl-text, #e2fff1);
    font-size: clamp(22px, 5vw, 28px);
    line-height: 1.15;
    letter-spacing: -.045em;
}

:root[data-bttl="ultra"] .bttl-guide-intro {
    position: relative;
    z-index: 1;
    margin: 12px 0 20px;
    color: var(--bttl-muted, #9bbbad);
    font-size: 13px;
    line-height: 1.65;
}

:root[data-bttl="ultra"] .bttl-guide-list {
    position: relative;
    z-index: 1;
    display: grid;
    gap: 8px;
    margin: 0;
    padding: 0;
    list-style: none;
}

:root[data-bttl="ultra"] .bttl-guide-list li {
    display: grid;
    grid-template-columns: 28px minmax(0, 1fr);
    gap: 10px;
    align-items: start;
    padding: 10px;
    border: 1px solid var(--bttl-line-soft, rgba(70, 240, 176, .2));
    border-radius: 4px;
    background: rgba(70, 240, 176, .035);
}

:root[data-bttl="ultra"] .bttl-guide-index {
    padding-top: 1px;
    color: var(--bttl-signal, #46f0b0);
    font-size: 10px;
    font-weight: 700;
}

:root[data-bttl="ultra"] .bttl-guide-list strong,
:root[data-bttl="ultra"] .bttl-guide-list small {
    display: block;
}

:root[data-bttl="ultra"] .bttl-guide-list strong {
    color: var(--bttl-text, #e2fff1);
    font-size: 13px;
    line-height: 1.35;
}

:root[data-bttl="ultra"] .bttl-guide-list small {
    margin-top: 2px;
    color: var(--bttl-muted, #9bbbad);
    font-size: 11px;
    line-height: 1.5;
}

:root[data-bttl="ultra"] .bttl-guide-actions {
    position: relative;
    z-index: 1;
    margin-top: 20px;
    margin-bottom: 0;
}

:root[data-bttl="ultra"] .bttl-guide-actions .btn {
    min-height: 38px;
    font-family: inherit;
}

@media (max-width: 760px) {
    :root[data-bttl="ultra"] .bttl-guide-modal {
        align-items: center;
        padding: 14px;
    }

    :root[data-bttl="ultra"] .bttl-guide-content {
        width: min(530px, 100%);
        max-height: min(88dvh, 700px);
        padding: 24px 18px 18px;
        border-radius: 7px;
    }

    :root[data-bttl="ultra"] .bttl-guide-content::before {
        display: none;
    }

    :root[data-bttl="ultra"] .bttl-guide-content::after {
        content: none;
    }

    :root[data-bttl="ultra"] .bttl-guide-list li {
        padding: 9px;
    }
}

@media (max-width: 390px) {
    :root[data-bttl="ultra"] .bttl-guide-modal {
        padding: 10px;
    }

    :root[data-bttl="ultra"] .bttl-guide-content {
        padding: 22px 14px 14px;
    }

    :root[data-bttl="ultra"] .bttl-guide-kicker {
        font-size: 8.5px;
        letter-spacing: .1em;
    }

    :root[data-bttl="ultra"] .bttl-guide-intro {
        margin-bottom: 14px;
        font-size: 12px;
    }

    :root[data-bttl="ultra"] .bttl-guide-list {
        gap: 6px;
    }

    :root[data-bttl="ultra"] .bttl-guide-list li {
        grid-template-columns: 24px minmax(0, 1fr);
        gap: 7px;
        padding: 8px;
    }

    :root[data-bttl="ultra"] .bttl-guide-list small {
        font-size: 10px;
    }

    :root[data-bttl="ultra"] .bttl-guide-actions {
        display: grid;
        grid-template-columns: 1fr 1.15fr;
        gap: 8px;
    }

    :root[data-bttl="ultra"] .bttl-guide-actions .btn {
        min-width: 0;
        padding-inline: 8px;
        font-size: 12px;
    }
}