feat: support multiple assignees for tasks

apps/mcp/src/__tests__/utils/formatters.test.ts

@@ -91,7 +91,7 @@ describe("formatTask", () => {
 		const result = formatTask(baseTask);
 		expect(result).toContain("Status: None");
 		expect(result).toContain("Sprint: None");
-		expect(result).toContain("Assignee: Unassigned");
+		expect(result).toContain("Assignees: Unassigned");
 		expect(result).toContain("Parent Task: None");
 		expect(result).toContain("Story Points: None");
 		expect(result).toContain("Tags: None");
@@ -403,12 +403,12 @@ describe("formatTaskDetail", () => {
 			role_name: "Developer",
 		};
 		const result = formatTaskDetail(
-			{ ...baseTask, assignee_id: "u1" },
+			{ ...baseTask, assignee_ids: ["u1"] },
 			undefined,
 			undefined,
 			undefined,
 			undefined,
-			assignee,
+			[assignee],
 		);
 		expect(result).toContain("Alice Smith");
 		expect(result).toContain("@alice");

apps/mcp/src/api/client.ts

@@ -207,7 +207,8 @@ export class PacaAPIClient {
 		if (input.task_type_id !== undefined)
 			body.task_type_id = input.task_type_id;
 		if (input.sprint_id !== undefined) body.sprint_id = input.sprint_id;
-		if (input.assignee_id !== undefined) body.assignee_id = input.assignee_id;
+		if (input.assignee_id !== undefined)
+			body.assignee_ids = input.assignee_id ? [input.assignee_id] : [];
 		if (input.parent_task_id !== undefined)
 			body.parent_task_id = input.parent_task_id;
 		if (input.importance !== undefined) body.importance = input.importance;
@@ -237,7 +238,8 @@ export class PacaAPIClient {
 		if (input.task_type_id !== undefined)
 			body.task_type_id = input.task_type_id;
 		if (input.sprint_id !== undefined) body.sprint_id = input.sprint_id;
-		if (input.assignee_id !== undefined) body.assignee_id = input.assignee_id;
+		if (input.assignee_id !== undefined)
+			body.assignee_ids = input.assignee_id ? [input.assignee_id] : [];
 		if (input.reporter_id !== undefined) body.reporter_id = input.reporter_id;
 		if (input.parent_task_id !== undefined)
 			body.parent_task_id = input.parent_task_id;

apps/mcp/src/tools/task-tools.ts

@@ -548,7 +548,9 @@ async function getTaskDetail(
 	const status = statuses.find((s: any) => s.id === task.status_id);
 	const taskType = taskTypes.find((t: any) => t.id === task.task_type_id);
 	const sprint = sprints.find((s: any) => s.id === task.sprint_id);
-	const assignee = members.find((m: any) => m.id === task.assignee_id);
+	const assignees = members.filter((m: any) =>
+		task.assignee_ids?.includes(m.id),
+	);
 	const reporter = members.find((m: any) => m.id === task.reporter_id);
 	let parentTask: Task | undefined;
 	if (task.parent_task_id) {
@@ -565,7 +567,7 @@ async function getTaskDetail(
 		status,
 		taskType,
 		sprint,
-		assignee,
+		assignees,
 		reporter,
 		parentTask,
 		subtasks,

apps/mcp/src/types/index.ts

@@ -81,7 +81,7 @@ export interface Task {
 	description?: unknown[] | null;
 	importance: number;
 	story_points?: number | null;
-	assignee_id?: string | null;
+	assignee_ids?: string[];
 	reporter_id?: string | null;
 	custom_fields: Record<string, unknown>;
 	start_date?: string | null;

apps/mcp/src/utils/formatters.ts

@@ -56,7 +56,7 @@ ID: ${task.id}
 Status: ${task.status_id || "None"}
 Type: ${task.task_type_id || "None"}
 Sprint: ${task.sprint_id || "None"}
-Assignee: ${task.assignee_id || "Unassigned"}
+Assignees: ${task.assignee_ids && task.assignee_ids.length > 0 ? task.assignee_ids.join(", ") : "Unassigned"}
 Parent Task: ${task.parent_task_id || "None"}
 Importance: ${task.importance}
 Story Points: ${task.story_points ?? "None"}
@@ -77,7 +77,7 @@ ${description}`;
  * @param status - The task status object (if available)
  * @param taskType - The task type object (if available)
  * @param sprint - The sprint object (if available)
- * @param assignee - The assignee member object (if available)
+ * @param assignees - The assignee member objects (if available)
  * @param reporter - The reporter member object (if available)
  * @param parentTask - The parent task object (if available)
  * @param subtasks - Array of subtasks (if available)
@@ -100,7 +100,7 @@ export function formatTaskDetail(
 	status?: TaskStatus,
 	taskType?: TaskType,
 	sprint?: Sprint,
-	assignee?: ProjectMember,
+	assignees?: ProjectMember[],
 	reporter?: ProjectMember,
 	parentTask?: Task,
 	subtasks?: Task[],
@@ -141,10 +141,14 @@ export function formatTaskDetail(
 		);
 	}
 
-	if (assignee || task.assignee_id) {
-		sections.push(
-			`**Assignee:** ${assignee ? `${assignee.full_name || assignee.username} (@${assignee.username})` : task.assignee_id || "Unassigned"}`,
-		);
+	if ((assignees && assignees.length > 0) || (task.assignee_ids && task.assignee_ids.length > 0)) {
+		const label =
+			assignees && assignees.length > 0
+				? assignees
+						.map((a) => `${a.full_name || a.username} (@${a.username})`)
+						.join(", ")
+				: (task.assignee_ids ?? []).join(", ") || "Unassigned";
+		sections.push(`**Assignees:** ${label}`);
 	}
 
 	if (reporter || task.reporter_id) {
@@ -200,7 +204,7 @@ export function formatTaskDetail(
 		sections.push("## Subtasks");
 		subtasks.forEach((subtask, index) => {
 			sections.push(
-				`${index + 1}. **${subtask.title}** (#${subtask.task_number}) - Status ID: ${subtask.status_id || "None"}, Type ID: ${subtask.task_type_id || "None"}, Assignee ID: ${subtask.assignee_id || "Unassigned"}`,
+				`${index + 1}. **${subtask.title}** (#${subtask.task_number}) - Status ID: ${subtask.status_id || "None"}, Type ID: ${subtask.task_type_id || "None"}, Assignee IDs: ${subtask.assignee_ids && subtask.assignee_ids.length > 0 ? subtask.assignee_ids.join(", ") : "Unassigned"}`,
 			);
 		});
 	}

apps/web/src/components/projects/interactions/board-view.test.tsx

@@ -61,7 +61,7 @@ const makeTask = (overrides: Partial<Task> = {}): Task => ({
 	parent_task_id: null,
 	description: null,
 	importance: 0,
-	assignee_id: null,
+	assignee_ids: [],
 	reporter_id: null,
 	custom_fields: {},
 	view_position: null,

apps/web/src/components/projects/interactions/task-card.test.tsx

@@ -17,7 +17,7 @@ const makeTask = (overrides: Partial<Task> = {}): Task => ({
 	parent_task_id: null,
 	description: null,
 	importance: 0,
-	assignee_id: null,
+	assignee_ids: [],
 	reporter_id: null,
 	custom_fields: {},
 	view_position: null,
@@ -166,13 +166,13 @@ describe("TaskCard", () => {
 	it("shows the assignee icon when task has an assignee", () => {
 		const { container } = render(
 			<TaskCard
-				task={makeTask({ assignee_id: "user-1" })}
+				task={makeTask({ assignee_ids: ["user-1"] })}
 				statuses={NO_STATUSES}
 				taskTypes={NO_TYPES}
 			/>,
 		);
-		// assigned state: filled avatar circle with ring-primary/20
-		const assigneeEl = container.querySelector(".ring-primary\\/20");
+		// assigned state: filled avatar circle with the primary gradient
+		const assigneeEl = container.querySelector(".from-primary\\/20");
 		expect(assigneeEl).toBeInTheDocument();
 	});
 });

apps/web/src/components/projects/interactions/task-card.tsx

@@ -74,33 +74,54 @@ export function TaskCard({
 	const { t } = useTranslation("projects");
 	const [typePopoverOpen, setTypePopoverOpen] = useState(false);
 	const taskType = taskTypes.find((t) => t.id === task.task_type_id);
-	const assignee = task.assignee_id
-		? members.find((m) => m.id === task.assignee_id)
-		: undefined;
 	const status = statuses.find((s) => s.id === task.status_id);
 
 	/** Renders the chip/indicator for a single field key. */
 	const renderField = (fieldKey: string) => {
 		switch (fieldKey) {
-			case "assignee":
+			case "assignee": {
+				const assigneeIds = task.assignee_ids ?? [];
+				const visible = assigneeIds.slice(0, 3);
+				const overflow = assigneeIds.length - visible.length;
+				const avatarStack = (
+					<div className="flex items-center -space-x-1.5">
+						{visible.length > 0 ? (
+							visible.map((id) => {
+								const m = members.find((mm) => mm.id === id);
+								return (
+									<div
+										key={id}
+										className="flex size-5 items-center justify-center rounded-full bg-linear-to-br from-primary/20 to-primary/15 text-primary text-xs font-bold ring-2 ring-card"
+									>
+										{m ? (
+											(m.full_name || m.username).slice(0, 1).toUpperCase()
+										) : (
+											<User className="size-2.5" />
+										)}
+									</div>
+								);
+							})
+						) : (
+							<div className="flex size-5 items-center justify-center rounded-full bg-linear-to-br from-muted/80 to-muted/40 text-muted-foreground text-xs font-bold ring-1 ring-border/25">
+								<User className="size-2.5" />
+							</div>
+						)}
+						{overflow > 0 && (
+							<div className="flex size-5 items-center justify-center rounded-full bg-muted text-muted-foreground text-[10px] font-bold ring-2 ring-card">
+								+{overflow}
+							</div>
+						)}
+					</div>
+				);
+
 				return canEdit && members.length > 0 ? (
 					<Popover key="assignee">
 						<PopoverTrigger
 							type="button"
 							onClick={(e) => e.stopPropagation()}
-							className="nodrag flex size-5 items-center justify-center rounded-full transition-all duration-150 hover:ring-2 hover:ring-primary/30"
+							className="nodrag flex items-center rounded-full transition-all duration-150 hover:ring-2 hover:ring-primary/30"
 						>
-							{assignee ? (
-								<div className="flex size-5 items-center justify-center rounded-full bg-linear-to-br from-primary/20 to-primary/15 text-primary text-xs font-bold ring-1 ring-primary/20">
-									{(assignee.full_name || assignee.username)
-										.slice(0, 1)
-										.toUpperCase()}
-								</div>
-							) : (
-								<div className="flex size-5 items-center justify-center rounded-full bg-linear-to-br from-muted/80 to-muted/40 text-muted-foreground text-xs font-bold ring-1 ring-border/25">
-									<User className="size-2.5" />
-								</div>
-							)}
+							{avatarStack}
 						</PopoverTrigger>
 						<PopoverContent
 							className="w-48 p-1 rounded-xl border border-border/40 shadow-lg"
@@ -111,57 +132,50 @@ export function TaskCard({
 								className="flex w-full items-center gap-2.5 rounded-lg px-3 py-2 text-sm text-muted-foreground hover:bg-muted/60 transition-colors duration-100"
 								onClick={(e) => {
 									e.stopPropagation();
-									onUpdate?.(task.id, { assignee_id: null });
+									onUpdate?.(task.id, { assignee_ids: [] });
 								}}
 							>
 								<User className="size-3.5 opacity-60" />
 								<span className="flex-1 text-left">
 									{t("board.taskCard.unassigned")}
 								</span>
-								{!assignee && <Check className="size-3.5 text-primary" />}
+								{assigneeIds.length === 0 && (
+									<Check className="size-3.5 text-primary" />
+								)}
 							</button>
-							{members.map((m) => (
-								<button
-									key={m.id}
-									type="button"
-									className="flex w-full items-center gap-2.5 rounded-lg px-3 py-2 text-sm hover:bg-muted/60 transition-colors duration-100"
-									onClick={(e) => {
-										e.stopPropagation();
-										onUpdate?.(task.id, { assignee_id: m.id });
-									}}
-								>
-									<div className="flex size-5 items-center justify-center rounded-full bg-linear-to-br from-primary/20 to-primary/10 text-primary text-xs font-bold">
-										{(m.full_name || m.username).slice(0, 1).toUpperCase()}
-									</div>
-									<span className="flex-1 text-left truncate">
-										{m.full_name || m.username}
-									</span>
-									{m.id === task.assignee_id && (
-										<Check className="size-3.5 text-primary" />
-									)}
-								</button>
-							))}
+							{members.map((m) => {
+								const isSelected = task.assignee_ids?.includes(m.id) ?? false;
+								return (
+									<button
+										key={m.id}
+										type="button"
+										className="flex w-full items-center gap-2.5 rounded-lg px-3 py-2 text-sm hover:bg-muted/60 transition-colors duration-100"
+										onClick={(e) => {
+											e.stopPropagation();
+											const current = task.assignee_ids ?? [];
+											onUpdate?.(task.id, {
+												assignee_ids: isSelected
+													? current.filter((id) => id !== m.id)
+													: [...current, m.id],
+											});
+										}}
+									>
+										<div className="flex size-5 items-center justify-center rounded-full bg-linear-to-br from-primary/20 to-primary/10 text-primary text-xs font-bold">
+											{(m.full_name || m.username).slice(0, 1).toUpperCase()}
+										</div>
+										<span className="flex-1 text-left truncate">
+											{m.full_name || m.username}
+										</span>
+										{isSelected && <Check className="size-3.5 text-primary" />}
+									</button>
+								);
+							})}
 						</PopoverContent>
 					</Popover>
 				) : (
-					<div
-						key="assignee"
-						className={cn(
-							"flex size-5 items-center justify-center rounded-full text-xs font-bold ring-1",
-							task.assignee_id
-								? "bg-linear-to-br from-primary/20 to-primary/15 text-primary ring-primary/20"
-								: "bg-linear-to-br from-muted/80 to-muted/40 text-muted-foreground ring-border/25",
-						)}
-					>
-						{assignee ? (
-							(assignee.full_name || assignee.username)
-								.slice(0, 1)
-								.toUpperCase()
-						) : (
-							<User className="size-2.5" />
-						)}
-					</div>
+					<div key="assignee">{avatarStack}</div>
 				);
+			}
 
 			case "type":
 				return canEdit && taskTypes.length > 0 ? (

apps/web/src/components/projects/interactions/task-detail-panel.tsx

@@ -112,7 +112,7 @@ export function TaskDetailPanel({
 											<User className="size-3.5 opacity-70" />
 											{t("taskDetail.panel.assignee")}
 										</span>
-										{task.assignee_id ? (
+										{task.assignee_ids && task.assignee_ids.length > 0 ? (
 											<div className="flex items-center gap-2">
 												<div className="flex size-6 items-center justify-center rounded-full bg-linear-to-br from-primary/20 to-primary/10 text-primary text-xs font-bold ring-1 ring-primary/20">
 													<User className="size-3" />

apps/web/src/components/projects/interactions/task-detail/activity-item.tsx

@@ -66,14 +66,19 @@ export function describeTaskChange(
 				return t("taskDetail.activity.changedPriority", { oldVal, newVal });
 			return t("taskDetail.activity.setPriority", { newVal });
 		case "assignee": {
-			const oldName = resolveMember(change.old);
-			const newName = resolveMember(change.new);
-			if (hasOld && hasNew)
+			const oldIds = Array.isArray(change.old) ? change.old : [];
+			const newIds = Array.isArray(change.new) ? change.new : [];
+			const resolveMembers = (ids: unknown[]) =>
+				ids.map((id) => resolveMember(id)).join(", ");
+			const oldName = resolveMembers(oldIds);
+			const newName = resolveMembers(newIds);
+			if (oldIds.length > 0 && newIds.length > 0)
 				return t("taskDetail.activity.changedAssignee", {
 					oldName,
 					newName,
 				});
-			if (hasNew) return t("taskDetail.activity.assignedTo", { newName });
+			if (newIds.length > 0)
+				return t("taskDetail.activity.assignedTo", { newName });
 			return t("taskDetail.activity.removedAssignee", { oldName });
 		}
 		case "reporter": {

apps/web/src/components/projects/interactions/task-detail/activity-pane.tsx

@@ -193,8 +193,9 @@ export function TaskActivityPane({
 						if (typeof oldVal === "number") payload.importance = oldVal;
 						break;
 					case "assignee":
-						payload.assignee_id =
-							typeof oldVal === "string" && oldVal ? oldVal : null;
+						payload.assignee_ids = Array.isArray(oldVal)
+							? oldVal.filter((v): v is string => typeof v === "string")
+							: [];
 						break;
 					case "reporter":
 						payload.reporter_id =