frontend/src/App.css

.app-shell {
  display: flex;
  height: var(--app-shell-height, 100vh);
  color: #1c1f25;
  background: #f4f5fb;
  overflow: hidden;
}

.sidebar {
  width: 320px;
  background: #fff;
  border-right: 1px solid #e5e7ef;
  display: flex;
  flex-direction: column;
  height: 100%;
}

.sidebar-header {
  padding: 1.5rem;
  border-bottom: 1px solid #eef0f7;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  position: sticky;
  top: 0;
  background: #fff;
  z-index: 1;
}

.sidebar-header h2 {
  margin: 0;
  font-size: 1.1rem;
}

.sidebar-header p {
  margin: 0;
  color: #6b7280;
  font-size: 0.9rem;
}

.new-chat {
  align-self: flex-start;
  background: #5b21b6;
  color: #fff;
  border: none;
  padding: 0.55rem 1rem;
  border-radius: 999px;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.2s ease;
}

.new-chat:hover {
  background: #4c1d95;
}

.session-list {
  flex: 1;
  overflow-y: auto;
  padding: 0.75rem 0;
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

.session-item {
  border: none;
  background: transparent;
  text-align: left;
  padding: 0.75rem 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
  transition: background 0.15s ease, color 0.15s ease;
  cursor: pointer;
}

.session-item .title {
  font-weight: 600;
}

.session-item .timestamp {
  font-size: 0.85rem;
  color: #6b7280;
}

.session-item:hover {
  background: #f4f5fb;
}

.session-item.active {
  background: #ede9fe;
}

.chat-pane {
  flex: 1;
  display: flex;
  flex-direction: column;
  padding: 1.25rem 2rem 1.25rem;
  gap: 1rem;
  height: 100%;
  overflow: hidden;
}

.chat-header {
  display: flex;
  justify-content: space-between;
  gap: 1.5rem;
  flex-wrap: wrap;
  padding-bottom: 0.75rem;
  position: sticky;
  top: 0;
  background: #f4f5fb;
  z-index: 1;
}

.chat-header h1 {
  margin: 0;
  font-size: 1.6rem;
}

.chat-header p {
  margin: 0.35rem 0 0;
  color: #6b7280;
}

.model-picker {
  min-width: 240px;
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}

.model-picker label {
  font-size: 0.85rem;
  font-weight: 600;
  color: #4b5563;
}

.model-picker select {
  padding: 0.4rem 0.6rem;
  border-radius: 0.5rem;
  border: 1px solid #d4d4d8;
  background: #fff;
}

.model-note {
  margin: 0;
  font-size: 0.85rem;
  color: #6b7280;
}

.chat-log {
  flex: 1;
  background: #fff;
  border: 1px solid #e5e7ef;
  border-radius: 1rem;
  padding: 1.25rem;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 1rem;
  min-height: 0;
}

.history-entry {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.message {
  border-radius: 0.75rem;
  padding: 0.85rem 1rem;
  max-width: 720px;
  background: #f3f4f6;
  position: relative;
}

.message.user {
  align-self: flex-start;
  background: #eef2ff;
}

.message.assistant {
  align-self: flex-start;
  background: #f9fafb;
}

.message.pending {
  opacity: 0.8;
}

.message .content {
  margin: 0;
  white-space: pre-wrap;
}

.message .meta {
  margin-top: 0.5rem;
  font-size: 0.8rem;
  color: #6b7280;
}

.provenance {
  font-size: 0.85rem;
}

.provenance summary {
  cursor: pointer;
  color: #4c1d95;
}

.provenance-body {
  margin-top: 0.5rem;
  border-left: 3px solid #ede9fe;
  padding-left: 0.75rem;
  color: #4b5563;
}

.provenance-body h4 {
  margin-bottom: 0.3rem;
}

.provenance-body ul {
  margin: 0 0 0.4rem;
  padding-left: 1.2rem;
}

.composer {
  display: flex;
  gap: 0.75rem;
  border: 1px solid #d4d4d8;
  border-radius: 1rem;
  padding: 0.75rem;
  background: #fff;
  position: sticky;
  bottom: 1rem;
  box-shadow: 0 10px 40px rgba(15, 23, 42, 0.08);
  z-index: 1;
}

.composer textarea {
  flex: 1;
  border: none;
  resize: none;
  font-family: inherit;
  font-size: 1rem;
  line-height: 1.4;
}

.composer textarea:focus {
  outline: none;
}

.composer button {
  align-self: flex-end;
  border: none;
  background: #5b21b6;
  color: #fff;
  font-weight: 600;
  padding: 0.6rem 1.5rem;
  border-radius: 0.75rem;
  cursor: pointer;
  transition: background 0.2s ease;
}

.composer button:disabled {
  background: #c4b5fd;
  cursor: not-allowed;
}

.empty-state {
  text-align: center;
  color: #6b7280;
  padding: 2rem 0;
}

.error {
  color: #b91c1c;
  margin: 0.5rem 1rem;
}

.status {
  color: #6b7280;
  margin: 0;
}

@media (max-width: 960px) {
  .app-shell {
    flex-direction: column;
    height: auto;
    overflow: visible;
  }

  .sidebar {
    width: 100%;
    border-right: none;
    border-bottom: 1px solid #e5e7ef;
    height: auto;
  }

  .chat-pane {
    height: auto;
    padding: 1.25rem;
  }

  .composer {
    position: static;
    box-shadow: none;
  }
}