diff --git a/frontend/e2e/flows.spec.ts b/frontend/e2e/flows.spec.ts
index 2285d6da4..b5c9bcb82 100644
--- a/frontend/e2e/flows.spec.ts
+++ b/frontend/e2e/flows.spec.ts
@@ -712,12 +712,8 @@ for (const variant of TARGET_VARIANTS) {
       const starBtn = page.getByTestId(`star-btn-${newConversationId}`);
       await expect(starBtn).toBeVisible({ timeout: 5_000 });
 
-      // Promote via backend API directly (UI handler targets a mismatched path)
-      const promoteResp = await request.post(
-        `/api/attacks/${encodeURIComponent(attackResultId)}/update-main-conversation`,
-        { data: { conversation_id: newConversationId } },
-      );
-      expect(promoteResp.ok()).toBeTruthy();
+      // Promote via the UI star button (tests the full click → API → refresh flow)
+      await starBtn.click();
 
       await expect
         .poll(
@@ -889,17 +885,10 @@ for (const variant of TARGET_VARIANTS) {
         timeout: 5_000,
       });
 
-      // Verify star button is visible but promote via API directly
-      // (UI handler targets a mismatched endpoint path)
-      await expect(
-        page.getByTestId(`star-btn-${branchConversationId}`),
-      ).toBeVisible({ timeout: 5_000 });
-
-      const promoteResp = await request.post(
-        `/api/attacks/${encodeURIComponent(attackResultId)}/update-main-conversation`,
-        { data: { conversation_id: branchConversationId } },
-      );
-      expect(promoteResp.ok()).toBeTruthy();
+      // Promote via the UI star button (tests the full click → API → refresh flow)
+      const starBtn = page.getByTestId(`star-btn-${branchConversationId}`);
+      await expect(starBtn).toBeVisible({ timeout: 5_000 });
+      await starBtn.click();
 
       await expect
         .poll(
diff --git a/frontend/src/components/Chat/ChatWindow.tsx b/frontend/src/components/Chat/ChatWindow.tsx
index e7e57cbd6..92249fa02 100644
--- a/frontend/src/components/Chat/ChatWindow.tsx
+++ b/frontend/src/components/Chat/ChatWindow.tsx
@@ -391,6 +391,7 @@ export default function ChatWindow({
 
     try {
       await attacksApi.changeMainConversation(attackResultId, convId)
+      setPanelRefreshKey(k => k + 1)
     } catch (err) {
       console.error('Failed to change main conversation:', err)
     }
@@ -528,7 +529,12 @@ export default function ChatWindow({
           onNewConversation={handleNewConversation}
           onChangeMainConversation={handleChangeMainConversation}
           onClose={() => setIsPanelOpen(false)}
-          locked={!activeTarget || isOperatorLocked || isCrossTargetLocked}
+          lockedReason={
+            !activeTarget ? 'Configure a target to enable this action.'
+            : isOperatorLocked ? 'Cannot modify — attack belongs to a different operator.'
+            : isCrossTargetLocked ? 'Cannot modify — attack was created with a different target.'
+            : undefined
+          }
           refreshKey={panelRefreshKey}
         />
       )}
diff --git a/frontend/src/components/Chat/ConversationPanel.tsx b/frontend/src/components/Chat/ConversationPanel.tsx
index 23072c1de..267b0feaf 100644
--- a/frontend/src/components/Chat/ConversationPanel.tsx
+++ b/frontend/src/components/Chat/ConversationPanel.tsx
@@ -30,8 +30,8 @@ interface ConversationPanelProps {
   onNewConversation: () => void
   onChangeMainConversation: (conversationId: string) => void
   onClose: () => void
-  /** When true, disable mutating actions (new conversation, promote to main) */
-  locked?: boolean
+  /** When set, disables mutating actions (new conversation, promote to main) and explains why. */
+  lockedReason?: string
   /** Increment to trigger a conversation list refresh (e.g. after sending a message) */
   refreshKey?: number
 }
@@ -43,7 +43,7 @@ export default function ConversationPanel({
   onNewConversation,
   onChangeMainConversation,
   onClose,
-  locked,
+  lockedReason,
   refreshKey,
 }: ConversationPanelProps) {
   const styles = useConversationPanelStyles()
@@ -107,13 +107,13 @@ export default function ConversationPanel({
           )}
         </div>
         <div style={{ display: 'flex', gap: tokens.spacingHorizontalXXS }}>
-          <Tooltip content={locked ? 'Cannot modify — attack is locked' : 'New Conversation'} relationship="label">
+          <Tooltip content={lockedReason ?? 'New Conversation'} relationship="label">
             <Button
               appearance="subtle"
               size="small"
               icon={<AddRegular />}
               onClick={onNewConversation}
-              disabled={!attackResultId || locked}
+              disabled={!attackResultId || !!lockedReason}
               data-testid="new-conversation-btn"
             />
           </Tooltip>
@@ -184,14 +184,14 @@ export default function ConversationPanel({
                   <Tooltip
                     content={conv.conversation_id === mainConversationId
                       ? 'This is the main conversation.'
-                      : 'Promote to main conversation.'}
+                      : lockedReason ?? 'Promote to main conversation.'}
                     relationship="description"
                   >
                     <Button
                       appearance="subtle"
                       size="small"
                       icon={conv.conversation_id === mainConversationId ? <StarFilled /> : <StarRegular />}
-                      disabled={conv.conversation_id === mainConversationId || locked}
+                      disabled={conv.conversation_id === mainConversationId || !!lockedReason}
                       onClick={(e) => {
                         e.stopPropagation()
                         if (conv.conversation_id !== mainConversationId) {
diff --git a/frontend/src/services/api.ts b/frontend/src/services/api.ts
index 55b079313..c6f682bf8 100644
--- a/frontend/src/services/api.ts
+++ b/frontend/src/services/api.ts
@@ -155,7 +155,7 @@ export const attacksApi = {
     conversationId: string
   ): Promise<ChangeMainConversationResponse> => {
     const response = await apiClient.post(
-      `/attacks/${encodeURIComponent(attackResultId)}/change-main-conversation`,
+      `/attacks/${encodeURIComponent(attackResultId)}/update-main-conversation`,
       { conversation_id: conversationId }
     )
     return response.data