feat(agents): Add task assignment and comments functionality

backend/alembic/versions/8045fbfb157f_add_task_assigned_agent.py

@@ -0,0 +1,36 @@
+"""add task assigned agent
+
+Revision ID: 8045fbfb157f
+Revises: 6df47d330227
+Create Date: 2026-02-04 17:28:57.465934
+
+"""
+from __future__ import annotations
+
+from alembic import op
+
+
+# revision identifiers, used by Alembic.
+revision = '8045fbfb157f'
+down_revision = '6df47d330227'
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.execute(
+        "ALTER TABLE tasks ADD COLUMN IF NOT EXISTS assigned_agent_id UUID"
+    )
+    op.execute(
+        "ALTER TABLE tasks ADD CONSTRAINT IF NOT EXISTS tasks_assigned_agent_id_fkey "
+        "FOREIGN KEY (assigned_agent_id) REFERENCES agents(id)"
+    )
+
+
+def downgrade() -> None:
+    op.execute(
+        "ALTER TABLE tasks DROP CONSTRAINT IF EXISTS tasks_assigned_agent_id_fkey"
+    )
+    op.execute(
+        "ALTER TABLE tasks DROP COLUMN IF EXISTS assigned_agent_id"
+    )

backend/alembic/versions/b9d22e2a4d50_add_task_comments_index.py

@@ -0,0 +1,29 @@
+"""add task comments index
+
+Revision ID: b9d22e2a4d50
+Revises: 8045fbfb157f
+Create Date: 2026-02-04 17:32:06.204331
+
+"""
+from __future__ import annotations
+
+from alembic import op
+
+
+# revision identifiers, used by Alembic.
+revision = 'b9d22e2a4d50'
+down_revision = '8045fbfb157f'
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.execute(
+        "CREATE INDEX IF NOT EXISTS ix_activity_events_task_comment "
+        "ON activity_events (task_id, created_at) "
+        "WHERE event_type = 'task.comment'"
+    )
+
+
+def downgrade() -> None:
+    op.execute("DROP INDEX IF EXISTS ix_activity_events_task_comment")

backend/app/api/tasks.py

@@ -3,7 +3,8 @@ from __future__ import annotations
 from datetime import datetime
 
 from fastapi import APIRouter, Depends, HTTPException, status
-from sqlmodel import Session, select
+from sqlalchemy import asc
+from sqlmodel import Session, col, select
 
 from app.api.deps import (
     ActorContext,
@@ -14,9 +15,17 @@ from app.api.deps import (
 )
 from app.core.auth import AuthContext
 from app.db.session import get_session
+from app.models.agents import Agent
+from app.models.activity_events import ActivityEvent
 from app.models.boards import Board
 from app.models.tasks import Task
-from app.schemas.tasks import TaskCreate, TaskRead, TaskUpdate
+from app.schemas.tasks import (
+    TaskCommentCreate,
+    TaskCommentRead,
+    TaskCreate,
+    TaskRead,
+    TaskUpdate,
+)
 from app.services.activity_log import record_activity
 
 router = APIRouter(prefix="/boards/{board_id}/tasks", tags=["tasks"])
@@ -66,9 +75,25 @@ def update_task(
     previous_status = task.status
     updates = payload.model_dump(exclude_unset=True)
     if actor.actor_type == "agent":
+        if actor.agent and actor.agent.board_id and task.board_id:
+            if actor.agent.board_id != task.board_id:
+                raise HTTPException(status_code=status.HTTP_403_FORBIDDEN)
         allowed_fields = {"status"}
         if not set(updates).issubset(allowed_fields):
             raise HTTPException(status_code=status.HTTP_403_FORBIDDEN)
+        if "status" in updates:
+            if updates["status"] == "inbox":
+                task.assigned_agent_id = None
+            else:
+                task.assigned_agent_id = actor.agent.id if actor.agent else None
+    elif "status" in updates and updates["status"] == "inbox":
+        task.assigned_agent_id = None
+    if "assigned_agent_id" in updates and updates["assigned_agent_id"]:
+        agent = session.get(Agent, updates["assigned_agent_id"])
+        if agent is None:
+            raise HTTPException(status_code=status.HTTP_404_NOT_FOUND)
+        if agent.board_id and task.board_id and agent.board_id != task.board_id:
+            raise HTTPException(status_code=status.HTTP_409_CONFLICT)
     for key, value in updates.items():
         setattr(task, key, value)
     task.updated_at = datetime.utcnow()
@@ -103,3 +128,45 @@ def delete_task(
     session.delete(task)
     session.commit()
     return {"ok": True}
+
+
+@router.get("/{task_id}/comments", response_model=list[TaskCommentRead])
+def list_task_comments(
+    task: Task = Depends(get_task_or_404),
+    session: Session = Depends(get_session),
+    actor: ActorContext = Depends(require_admin_or_agent),
+) -> list[ActivityEvent]:
+    if actor.actor_type == "agent" and actor.agent:
+        if actor.agent.board_id and task.board_id and actor.agent.board_id != task.board_id:
+            raise HTTPException(status_code=status.HTTP_403_FORBIDDEN)
+    statement = (
+        select(ActivityEvent)
+        .where(col(ActivityEvent.task_id) == task.id)
+        .where(col(ActivityEvent.event_type) == "task.comment")
+        .order_by(asc(col(ActivityEvent.created_at)))
+    )
+    return list(session.exec(statement))
+
+
+@router.post("/{task_id}/comments", response_model=TaskCommentRead)
+def create_task_comment(
+    payload: TaskCommentCreate,
+    task: Task = Depends(get_task_or_404),
+    session: Session = Depends(get_session),
+    actor: ActorContext = Depends(require_admin_or_agent),
+) -> ActivityEvent:
+    if actor.actor_type == "agent" and actor.agent:
+        if actor.agent.board_id and task.board_id and actor.agent.board_id != task.board_id:
+            raise HTTPException(status_code=status.HTTP_403_FORBIDDEN)
+    if not payload.message.strip():
+        raise HTTPException(status_code=status.HTTP_422_UNPROCESSABLE_ENTITY)
+    event = ActivityEvent(
+        event_type="task.comment",
+        message=payload.message.strip(),
+        task_id=task.id,
+        agent_id=actor.agent.id if actor.actor_type == "agent" and actor.agent else None,
+    )
+    session.add(event)
+    session.commit()
+    session.refresh(event)
+    return event

backend/app/models/tasks.py

@@ -21,6 +21,7 @@ class Task(TenantScoped, table=True):
     due_at: datetime | None = None
 
     created_by_user_id: UUID | None = Field(default=None, foreign_key="users.id", index=True)
+    assigned_agent_id: UUID | None = Field(default=None, foreign_key="agents.id", index=True)
 
     created_at: datetime = Field(default_factory=datetime.utcnow)
     updated_at: datetime = Field(default_factory=datetime.utcnow)

backend/app/schemas/tasks.py

@@ -12,6 +12,7 @@ class TaskBase(SQLModel):
     status: str = "inbox"
     priority: str = "medium"
     due_at: datetime | None = None
+    assigned_agent_id: UUID | None = None
 
 
 class TaskCreate(TaskBase):
@@ -24,6 +25,7 @@ class TaskUpdate(SQLModel):
     status: str | None = None
     priority: str | None = None
     due_at: datetime | None = None
+    assigned_agent_id: UUID | None = None
 
 
 class TaskRead(TaskBase):
@@ -32,3 +34,15 @@ class TaskRead(TaskBase):
     created_by_user_id: UUID | None
     created_at: datetime
     updated_at: datetime
+
+
+class TaskCommentCreate(SQLModel):
+    message: str
+
+
+class TaskCommentRead(SQLModel):
+    id: UUID
+    message: str | None
+    agent_id: UUID | None
+    task_id: UUID | None
+    created_at: datetime

frontend/src/app/boards/[boardId]/page.tsx

@@ -40,6 +40,21 @@ type Task = {
   status: string;
   priority: string;
   due_at?: string | null;
+  assigned_agent_id?: string | null;
+};
+
+type Agent = {
+  id: string;
+  name: string;
+  board_id?: string | null;
+};
+
+type TaskComment = {
+  id: string;
+  message?: string | null;
+  agent_id?: string | null;
+  task_id?: string | null;
+  created_at: string;
 };
 
 const apiBase =
@@ -61,8 +76,14 @@ export default function BoardDetailPage() {
 
   const [board, setBoard] = useState<Board | null>(null);
   const [tasks, setTasks] = useState<Task[]>([]);
+  const [agents, setAgents] = useState<Agent[]>([]);
   const [isLoading, setIsLoading] = useState(false);
   const [error, setError] = useState<string | null>(null);
+  const [selectedTask, setSelectedTask] = useState<Task | null>(null);
+  const [comments, setComments] = useState<TaskComment[]>([]);
+  const [isCommentsLoading, setIsCommentsLoading] = useState(false);
+  const [commentsError, setCommentsError] = useState<string | null>(null);
+  const [isCommentsOpen, setIsCommentsOpen] = useState(false);
 
   const [isDialogOpen, setIsDialogOpen] = useState(false);
   const [title, setTitle] = useState("");
@@ -82,7 +103,7 @@ export default function BoardDetailPage() {
     setError(null);
     try {
       const token = await getToken();
-      const [boardResponse, tasksResponse] = await Promise.all([
+      const [boardResponse, tasksResponse, agentsResponse] = await Promise.all([
         fetch(`${apiBase}/api/v1/boards/${boardId}`, {
           headers: {
             Authorization: token ? `Bearer ${token}` : "",
@@ -93,6 +114,11 @@ export default function BoardDetailPage() {
             Authorization: token ? `Bearer ${token}` : "",
           },
         }),
+        fetch(`${apiBase}/api/v1/agents`, {
+          headers: {
+            Authorization: token ? `Bearer ${token}` : "",
+          },
+        }),
       ]);
 
       if (!boardResponse.ok) {
@@ -101,11 +127,16 @@ export default function BoardDetailPage() {
       if (!tasksResponse.ok) {
         throw new Error("Unable to load tasks.");
       }
+      if (!agentsResponse.ok) {
+        throw new Error("Unable to load agents.");
+      }
 
       const boardData = (await boardResponse.json()) as Board;
       const taskData = (await tasksResponse.json()) as Task[];
+      const agentData = (await agentsResponse.json()) as Agent[];
       setBoard(boardData);
       setTasks(taskData);
+      setAgents(agentData);
     } catch (err) {
       setError(err instanceof Error ? err.message : "Something went wrong.");
     } finally {
@@ -165,6 +196,74 @@ export default function BoardDetailPage() {
     }
   };
 
+  const assigneeById = useMemo(() => {
+    const map = new Map<string, string>();
+    agents
+      .filter((agent) => !boardId || agent.board_id === boardId)
+      .forEach((agent) => {
+        map.set(agent.id, agent.name);
+      });
+    return map;
+  }, [agents, boardId]);
+
+  const displayTasks = useMemo(
+    () =>
+      tasks.map((task) => ({
+        ...task,
+        assignee: task.assigned_agent_id
+          ? assigneeById.get(task.assigned_agent_id)
+          : undefined,
+      })),
+    [tasks, assigneeById],
+  );
+
+  const loadComments = async (taskId: string) => {
+    if (!isSignedIn || !boardId) return;
+    setIsCommentsLoading(true);
+    setCommentsError(null);
+    try {
+      const token = await getToken();
+      const response = await fetch(
+        `${apiBase}/api/v1/boards/${boardId}/tasks/${taskId}/comments`,
+        {
+          headers: { Authorization: token ? `Bearer ${token}` : "" },
+        },
+      );
+      if (!response.ok) {
+        throw new Error("Unable to load comments.");
+      }
+      const data = (await response.json()) as TaskComment[];
+      setComments(data);
+    } catch (err) {
+      setCommentsError(err instanceof Error ? err.message : "Something went wrong.");
+    } finally {
+      setIsCommentsLoading(false);
+    }
+  };
+
+  const openComments = (task: Task) => {
+    setSelectedTask(task);
+    setIsCommentsOpen(true);
+    void loadComments(task.id);
+  };
+
+  const closeComments = () => {
+    setIsCommentsOpen(false);
+    setSelectedTask(null);
+    setComments([]);
+    setCommentsError(null);
+  };
+
+  const formatCommentTimestamp = (value: string) => {
+    const date = new Date(value);
+    if (Number.isNaN(date.getTime())) return "—";
+    return date.toLocaleString(undefined, {
+      month: "short",
+      day: "numeric",
+      hour: "2-digit",
+      minute: "2-digit",
+    });
+  };
 
   return (
     <DashboardShell>
@@ -215,14 +314,72 @@ export default function BoardDetailPage() {
             </div>
           ) : (
             <TaskBoard
-              tasks={tasks}
+              tasks={displayTasks}
               onCreateTask={() => setIsDialogOpen(true)}
               isCreateDisabled={isCreating}
+              onTaskSelect={openComments}
             />
           )}
         </div>
       </SignedIn>
 
+      <Dialog open={isCommentsOpen} onOpenChange={(open) => {
+        if (!open) {
+          closeComments();
+        }
+      }}>
+        <DialogContent aria-label="Task comments">
+          <DialogHeader>
+            <DialogTitle>{selectedTask?.title ?? "Task"}</DialogTitle>
+            <DialogDescription>
+              {selectedTask?.description || "Task details and discussion."}
+            </DialogDescription>
+          </DialogHeader>
+          <div className="space-y-4">
+            <div className="space-y-3">
+              <div className="text-xs font-semibold uppercase tracking-[0.3em] text-quiet">
+                Comments
+              </div>
+              {isCommentsLoading ? (
+                <p className="text-sm text-muted">Loading comments…</p>
+              ) : commentsError ? (
+                <div className="rounded-lg border border-[color:var(--border)] bg-[color:var(--surface-muted)] p-3 text-xs text-muted">
+                  {commentsError}
+                </div>
+              ) : comments.length === 0 ? (
+                <p className="text-sm text-muted">No comments yet.</p>
+              ) : (
+                <div className="space-y-3">
+                  {comments.map((comment) => (
+                    <div
+                      key={comment.id}
+                      className="rounded-xl border border-[color:var(--border)] bg-[color:var(--surface)] p-3"
+                    >
+                      <div className="flex items-center justify-between text-xs text-muted">
+                        <span>
+                          {comment.agent_id
+                            ? assigneeById.get(comment.agent_id) ?? "Agent"
+                            : "Admin"}
+                        </span>
+                        <span>{formatCommentTimestamp(comment.created_at)}</span>
+                      </div>
+                      <p className="mt-2 text-sm text-strong">
+                        {comment.message || "—"}
+                      </p>
+                    </div>
+                  ))}
+                </div>
+              )}
+            </div>
+          </div>
+          <DialogFooter>
+            <Button variant="outline" onClick={closeComments}>
+              Close
+            </Button>
+          </DialogFooter>
+        </DialogContent>
+      </Dialog>
+
       <Dialog
         open={isDialogOpen}
         onOpenChange={(nextOpen) => {

frontend/src/components/molecules/TaskCard.tsx

@@ -8,11 +8,29 @@ interface TaskCardProps {
   status: string;
   assignee?: string;
   due?: string;
+  onClick?: () => void;
 }
 
-export function TaskCard({ title, status, assignee, due }: TaskCardProps) {
+export function TaskCard({
+  title,
+  status,
+  assignee,
+  due,
+  onClick,
+}: TaskCardProps) {
   return (
-    <Card className="border border-[color:var(--border)] bg-[color:var(--surface)]">
+    <Card
+      className="cursor-pointer border border-[color:var(--border)] bg-[color:var(--surface)] transition hover:border-[color:var(--border-strong)]"
+      onClick={onClick}
+      role="button"
+      tabIndex={0}
+      onKeyDown={(event) => {
+        if (event.key === "Enter" || event.key === " ") {
+          event.preventDefault();
+          onClick?.();
+        }
+      }}
+    >
       <CardContent className="space-y-4">
         <div className="flex items-start justify-between gap-3">
           <div className="space-y-2">

frontend/src/components/organisms/TaskBoard.tsx

@@ -10,12 +10,14 @@ type Task = {
   title: string;
   status: string;
   due_at?: string | null;
+  assignee?: string;
 };
 
 type TaskBoardProps = {
   tasks: Task[];
   onCreateTask: () => void;
   isCreateDisabled?: boolean;
+  onTaskSelect?: (task: Task) => void;
 };
 
 const columns = [
@@ -41,6 +43,7 @@ export function TaskBoard({
   tasks,
   onCreateTask,
   isCreateDisabled = false,
+  onTaskSelect,
 }: TaskBoardProps) {
   const grouped = useMemo(() => {
     const buckets: Record<string, Task[]> = {};
@@ -85,7 +88,9 @@ export function TaskBoard({
                   key={task.id}
                   title={task.title}
                   status={column.status}
+                  assignee={task.assignee}
                   due={formatDueDate(task.due_at)}
+                  onClick={() => onTaskSelect?.(task)}
                 />
               ))}
             </div>