fix: suggest comment reassignment from recent commenter

ui/src/lib/assignees.test.ts

@@ -4,6 +4,7 @@ import {
   currentUserAssigneeOption,
   formatAssigneeUserLabel,
   parseAssigneeValue,
+  suggestedCommentAssigneeValue,
 } from "./assignees";
 
 describe("assignee selection helpers", () => {
@@ -50,4 +51,27 @@ describe("assignee selection helpers", () => {
     expect(formatAssigneeUserLabel("local-board", "someone-else")).toBe("Board");
     expect(formatAssigneeUserLabel("user-abcdef", "someone-else")).toBe("user-");
   });
+
+  it("suggests the last non-me commenter without changing the actual assignee encoding", () => {
+    expect(
+      suggestedCommentAssigneeValue(
+        { assigneeUserId: "board-user" },
+        [
+          { authorUserId: "board-user" },
+          { authorAgentId: "agent-123" },
+        ],
+        "board-user",
+      ),
+    ).toBe("agent:agent-123");
+  });
+
+  it("falls back to the actual assignee when there is no better commenter hint", () => {
+    expect(
+      suggestedCommentAssigneeValue(
+        { assigneeUserId: "board-user" },
+        [{ authorUserId: "board-user" }],
+        "board-user",
+      ),
+    ).toBe("user:board-user");
+  });
 });

ui/src/lib/assignees.ts

@@ -9,12 +9,40 @@ export interface AssigneeOption {
   searchText?: string;
 }
 
+interface CommentAssigneeSuggestionInput {
+  assigneeAgentId?: string | null;
+  assigneeUserId?: string | null;
+}
+
+interface CommentAssigneeSuggestionComment {
+  authorAgentId?: string | null;
+  authorUserId?: string | null;
+}
+
 export function assigneeValueFromSelection(selection: Partial<AssigneeSelection>): string {
   if (selection.assigneeAgentId) return `agent:${selection.assigneeAgentId}`;
   if (selection.assigneeUserId) return `user:${selection.assigneeUserId}`;
   return "";
 }
 
+export function suggestedCommentAssigneeValue(
+  issue: CommentAssigneeSuggestionInput,
+  comments: CommentAssigneeSuggestionComment[] | null | undefined,
+  currentUserId: string | null | undefined,
+): string {
+  if (comments && comments.length > 0 && currentUserId) {
+    for (let i = comments.length - 1; i >= 0; i--) {
+      const comment = comments[i];
+      if (comment.authorAgentId) return assigneeValueFromSelection({ assigneeAgentId: comment.authorAgentId });
+      if (comment.authorUserId && comment.authorUserId !== currentUserId) {
+        return assigneeValueFromSelection({ assigneeUserId: comment.authorUserId });
+      }
+    }
+  }
+
+  return assigneeValueFromSelection(issue);
+}
+
 export function parseAssigneeValue(value: string): AssigneeSelection {
   if (!value) {
     return { assigneeAgentId: null, assigneeUserId: null };