src/components/Layout/Panel.module.css

@@ -5,6 +5,18 @@
   border-radius: 8px;
   background: var(--bg-primary, #fff);
   overflow: clip;
+  display: flex;
+  flex-direction: column;
+  min-height: 0;
+}
+
+/* Card regions in bounded flex hosts (sidebar, PanelLayout pane): body fills and scrolls. */
+.panel[data-variant="card"] .body:not(.bodyHidden) {
+  flex: 1;
+  min-height: 0;
+  overflow: auto;
+  display: flex;
+  flex-direction: column;
 }
 
 /* --- Variant: table — fills available height, bounded scroll --- */
@@ -94,11 +106,14 @@
   background: var(--bg-secondary, rgba(0, 0, 0, 0.02));
   border-bottom: 1px solid var(--border-color, rgba(0, 0, 0, 0.08));
   min-height: 40px;
+  position: relative;
 }
 
 .headerCollapsible {
   cursor: pointer;
   user-select: none;
+  /* Reserve space so action icons never overlap the collapse chevron */
+  padding-right: 30px;
 }
 
 .headerCollapsible:hover {
@@ -128,15 +143,20 @@
 }
 
 .actions {
-  flex-shrink: 0;
+  flex-shrink: 1;
+  min-width: 0;
   display: flex;
   align-items: center;
   gap: 4px;
+  margin-left: auto;
 }
 
-/* Stable chevron position: fixed at the right edge of the header, same spot
-   whether collapsed or expanded. Icon swaps (down = open, right = collapsed). */
+/* Collapse chevron: always rightmost, above action icons (never covered). */
 .chevron {
+  position: absolute;
+  right: 14px;
+  top: 50%;
+  transform: translateY(-50%);
   flex-shrink: 0;
   display: inline-flex;
   align-items: center;
@@ -145,6 +165,8 @@
   height: 16px;
   font-size: 12px;
   color: var(--text-tertiary, #888);
+  z-index: 2;
+  pointer-events: none;
 }
 
 .body {

src/components/Layout/Panel.tsx

@@ -75,12 +75,12 @@ export const Panel: FC<PanelProps> = ({
           <span className={styles.title}>{title}</span>
           {subtitle && <span className={styles.subtitle}>{subtitle}</span>}
         </div>
-        {actions && <div className={styles.actions} onClick={(e) => e.stopPropagation()}>{actions}</div>}
         {collapsible && (
           <span className={styles.chevron} aria-hidden>
             {collapsed ? <FaChevronRight /> : <FaChevronDown />}
           </span>
         )}
+        {actions && <div className={styles.actions} onClick={(e) => e.stopPropagation()}>{actions}</div>}
       </div>
       <div className={`${styles.body} ${collapsed ? styles.bodyHidden : ''}`}>
         {children}

src/components/UnifiedDataBar/ChatsTab.module.css

@@ -3,6 +3,8 @@
   flex-direction: column;
   flex: 1;
   min-height: 0;
+  height: 100%;
+  overflow: hidden;
   gap: 8px;
 }
 
@@ -100,6 +102,9 @@
 .tree {
   display: flex;
   flex-direction: column;
+  flex: 1;
+  min-height: 0;
+  overflow-y: auto;
 }
 
 .chatItem {

src/components/UnifiedDataBar/SourcesTab.module.css

@@ -0,0 +1,22 @@
+.sourcesTab {
+  display: flex;
+  flex-direction: column;
+  flex: 1;
+  min-height: 0;
+  height: 100%;
+  overflow: hidden;
+}
+
+.treeHost {
+  flex: 1;
+  min-height: 0;
+  overflow: hidden;
+  display: flex;
+  flex-direction: column;
+}
+
+.empty {
+  padding: 12px;
+  font-size: 12px;
+  color: #888;
+}

src/components/UnifiedDataBar/SourcesTab.tsx

@@ -20,6 +20,7 @@ import { createUdbSourcesProvider } from './UdbSourcesProvider';
 import type { UdbBackendNode } from './UdbSourcesProvider';
 import { DataSourceSettingsModal } from './DataSourceSettingsModal';
 import { useLanguage } from '../../providers/language/LanguageContext';
+import styles from './SourcesTab.module.css';
 
 interface SourcesTabProps {
   context: UdbContext;
@@ -84,15 +85,15 @@ const SourcesTab: React.FC<SourcesTabProps> = ({
 
   if (!instanceId || !provider) {
     return (
-      <div style={{ padding: 12, fontSize: 12, color: '#888' }}>
+      <div className={styles.empty}>
         {t('Keine Workspace-Instanz aktiv.')}
       </div>
     );
   }
 
   return (
-    <div style={{ height: '100%', display: 'flex', flexDirection: 'column', minHeight: 0 }}>
-      <div style={{ flex: 1, overflow: 'auto', minHeight: 0 }}>
+    <div className={styles.sourcesTab}>
+      <div className={styles.treeHost}>
         <FormGeneratorTree
           provider={provider}
           ownership="own"

src/components/UnifiedDataBar/UnifiedDataBar.module.css

@@ -41,7 +41,9 @@
 .tabContent {
   flex: 1;
   min-height: 0;
-  overflow-y: auto;
+  overflow: hidden;
+  display: flex;
+  flex-direction: column;
   padding: 8px;
 }
 

src/pages/views/commcoach/CommcoachSessionView.tsx

@@ -394,7 +394,7 @@ export const CommcoachSessionView: React.FC = () => {
                 collapsible: true,
                 collapseKey: 'commcoach-session-udb',
                 content: (
-                  <Panel variant="card" title={t('Datenquellen')} id="commcoach-session-data-sources">
+                  <Panel variant="card" title={t('Datenquellen')} id="commcoach-session-data-sources" fill>
                     <UnifiedDataBar
                       context={_udbContext}
                       activeTab={udbTab}

src/pages/views/teamsbot/TeamsbotSessionView.tsx

@@ -1006,7 +1006,7 @@ export const TeamsbotSessionView: React.FC = () => {
               collapsible: true,
               collapseKey: 'teamsbot-session-udb',
               content: (
-                <Panel variant="card" title={t('Datenquellen')} id="teamsbot-session-datasources">
+                <Panel variant="card" title={t('Datenquellen')} id="teamsbot-session-datasources" fill>
                   <UnifiedDataBar
                     context={_udbContext}
                     activeTab={udbTab}

src/pages/views/workspace/WorkspaceContextSidebar.tsx

@@ -67,6 +67,19 @@ export const WorkspaceContextSidebar: React.FC<WorkspaceContextSidebarProps> = (
     aria-label="Kontext"
   >
     <div className={styles.contextToolbar}>
+      {allowCollapse && (
+        <button
+          type="button"
+          className={styles.contextCollapseBtn}
+          onClick={onToggleCollapsed}
+          title={isCollapsed ? 'Kontext ausklappen' : 'Kontext einklappen'}
+          aria-expanded={!isCollapsed}
+        >
+          {isCollapsed ? <FaChevronRight aria-hidden /> : <FaChevronLeft aria-hidden />}
+        </button>
+      )}
+      {!isCollapsed && (
+        <>
       <button
         type="button"
         className={`${styles.contextToolBtn} ${activeTab === 'files' ? styles.contextToolBtnActive : ''}`}
@@ -104,16 +117,7 @@ export const WorkspaceContextSidebar: React.FC<WorkspaceContextSidebarProps> = (
         <FaEye aria-hidden />
       </button>
       <span className={styles.contextToolbarGrow} />
-      {allowCollapse && (
-        <button
-          type="button"
-          className={styles.contextCollapseBtn}
-          onClick={onToggleCollapsed}
-          title={isCollapsed ? 'Kontext ausklappen' : 'Kontext einklappen'}
-          aria-expanded={!isCollapsed}
-        >
-          {isCollapsed ? <FaChevronRight aria-hidden /> : <FaChevronLeft aria-hidden />}
-        </button>
+        </>
       )}
     </div>
     {!isCollapsed && (

src/pages/views/workspace/WorkspacePage.module.css

@@ -162,6 +162,20 @@
   width: 44px;
 }
 
+.contextSidebarCollapsed .contextToolbar {
+  flex-direction: column;
+  align-items: center;
+  justify-content: flex-start;
+  padding: 6px 4px;
+  gap: 6px;
+  border-bottom: none;
+}
+
+.contextSidebarCollapsed .contextCollapseBtn {
+  width: 32px;
+  height: 32px;
+}
+
 /* When hosted inside a PanelLayout pane, the sidebar fills the pane width so
    the divider controls its size (instead of the fixed 320px). */
 .contextSidebarFill {