[front] fix: stop sticky human mention re-inserting in the composer

front/components/assistant/conversation/AgentInputBar.tsx

@@ -712,6 +712,7 @@ export const AgentInputBar = ({ context }: AgentInputBarProps) => {
                 user={context.user}
                 onSubmit={context.handleSubmit}
                 stickyMentions={autoMentions}
+                stickyMentionsSourceId={lastUserMessage?.sId ?? null}
                 lastRequestedModel={lastRequestedModel}
                 conversation={context.conversation}
                 draftKey={context.draftKey}

front/components/assistant/conversation/input_bar/InputBar.tsx

@@ -90,6 +90,7 @@ interface InputBarProps {
   conversation?: ConversationWithoutContentType;
   space?: SpaceType;
   stickyMentions?: RichMention[];
+  stickyMentionsSourceId?: string | null;
   defaultAgentId?: string | null;
   isDefaultAgentLoading?: boolean;
   lastRequestedModel?: ModelSelectionType | null;
@@ -121,6 +122,7 @@ export const InputBar = React.memo(function InputBar({
   draftKey,
   space,
   stickyMentions,
+  stickyMentionsSourceId,
   defaultAgentId,
   isDefaultAgentLoading,
   lastRequestedModel = null,
@@ -767,6 +769,7 @@ export const InputBar = React.memo(function InputBar({
             pendingInputText={pendingInputText}
             onEnterKeyDown={handleSubmit}
             stickyMentions={stickyMentions}
+            stickyMentionsSourceId={stickyMentionsSourceId}
             defaultAgentId={defaultAgentId}
             isDefaultAgentLoading={isDefaultAgentLoading}
             lastRequestedModel={lastRequestedModel}

front/components/assistant/conversation/input_bar/InputBarContainer.tsx

@@ -253,6 +253,17 @@ export interface InputBarContainerProps {
   isSelectableSpacesLoading?: boolean;
   onSelectedSpaceIdsChange?: (spaceIds: string[]) => Promise<string[] | null>;
   stickyMentions?: RichMention[];
+  /**
+   * @cc [owner:frankaloia,label:react] sticky-human-mentions-prefill-once-per-source
+   * Sticky human mentions MUST be prefilled into the composer at most once per
+   * (conversation, source message). `stickyMentionsSourceId` identifies that source — the sId of
+   * the current user's last message the mentions derive from. Callers MUST set it so the prefill
+   * re-arms only when the user sends a new message (new source id) or switches conversation, not
+   * on unrelated conversation updates (streaming, other participants' messages). Re-inserting on
+   * every update re-adds the mention to the empty composer and prevents the user from dismissing
+   * it.
+   */
+  stickyMentionsSourceId?: string | null;
   user: UserType | null;
 }
 
@@ -278,6 +289,7 @@ const InputBarContainer = ({
   selectedAgent,
   pendingInputText,
   stickyMentions,
+  stickyMentionsSourceId,
   actions,
   disableAutoFocus,
   disableUserMentions,
@@ -853,6 +865,11 @@ const InputBarContainer = ({
   selectedSingleAgentRef.current = selectedSingleAgent;
   // Skip auto-save (especially clearDraft on empty) until initial content is restored.
   const hasCompletedInitialContentRestoreRef = useRef(false);
+  // Tracks the (conversation, source message) for which sticky human mentions were last
+  // prefilled, so we insert them once per source rather than on every re-render. Without this,
+  // streaming updates and other participants' messages would keep re-inserting the mention into
+  // the empty composer, and the user could not dismiss it.
+  const appliedStickyMentionKeyRef = useRef<string | null>(null);
 
   const saveCurrentDraftWithSelectedSpaces = useCallback(
     (spaceIds: string[]) => {
@@ -1387,7 +1404,6 @@ const InputBarContainer = ({
 
   // Restore draft text when switching conversations (including new conversations).
   // Agent selection is handled by useHandleMention.
-  // biome-ignore lint/correctness/useExhaustiveDependencies: ignored using `--suppress`
   useEffect(() => {
     hasCompletedInitialContentRestoreRef.current = false;
 
@@ -1421,10 +1437,19 @@ const InputBarContainer = ({
       return;
     }
 
-    // No draft — insert sticky user mentions into the editor
+    // No draft — insert sticky user mentions into the editor, but only once per source message.
+    // The effect re-runs on every conversation update (streaming, other participants' messages),
+    // so without this key it would keep re-inserting the mention into the empty composer and the
+    // user could never dismiss it. The key changes when the current user sends a new message (new
+    // source id) or switches conversation, which is exactly when we want to re-prefill.
     const stickyUserMentions = stickyMentions?.filter(isRichUserMention) ?? [];
-    if (stickyUserMentions.length > 0) {
+    const stickyMentionKey = `${conversation?.sId ?? "new"}::${stickyMentionsSourceId ?? ""}`;
+    if (
+      stickyUserMentions.length > 0 &&
+      appliedStickyMentionKeyRef.current !== stickyMentionKey
+    ) {
       editorService.resetWithMentions(stickyUserMentions, disableAutoFocus);
+      appliedStickyMentionKeyRef.current = stickyMentionKey;
     }
 
     hasCompletedInitialContentRestoreRef.current = true;
@@ -1436,6 +1461,7 @@ const InputBarContainer = ({
     editorService,
     getDraft,
     stickyMentions,
+    stickyMentionsSourceId,
     disableAutoFocus,
   ]);