feat(kanban): drag-to-delete trash zone + bulk delete for task cards

Salvages #28125 by @Jpalmer95. Adds:
- Drag-to-delete trash zone in the kanban dashboard
- Bulk delete endpoint with cascading delete_task cleanup
- Frontend updates (drag visual + drop handler)
- Confirmation prompt before delete

Resolved end-of-file test conflict by appending both halves.

hermes_cli/kanban_db.py

@@ -3368,6 +3368,29 @@ def delete_archived_task(conn: sqlite3.Connection, task_id: str) -> bool:
         return cur.rowcount == 1
 
 
+def delete_task(conn: sqlite3.Connection, task_id: str) -> bool:
+    """Hard-delete a task and cascade to all related rows.
+
+    Because the schema does not use ``ON DELETE CASCADE`` foreign keys,
+    we explicitly delete from child tables first, then the task row.
+    This keeps the operation atomic (single ``write_txn``).
+
+    Returns ``True`` if the task existed and was deleted, ``False``
+    if the task was not found.
+    """
+    with write_txn(conn):
+        cur = conn.execute("DELETE FROM tasks WHERE id = ?", (task_id,))
+        if cur.rowcount != 1:
+            return False
+        conn.execute("DELETE FROM task_links WHERE parent_id = ? OR child_id = ?", (task_id, task_id))
+        conn.execute("DELETE FROM task_comments WHERE task_id = ?", (task_id,))
+        conn.execute("DELETE FROM task_events WHERE task_id = ?", (task_id,))
+        conn.execute("DELETE FROM task_runs WHERE task_id = ?", (task_id,))
+        conn.execute("DELETE FROM kanban_notify_subs WHERE task_id = ?", (task_id,))
+    recompute_ready(conn)
+    return True
+
+
 # ---------------------------------------------------------------------------
 # Workspace resolution
 # ---------------------------------------------------------------------------

plugins/kanban/dashboard/dist/index.js

@@ -83,6 +83,12 @@
     completion_blocked_hallucination: "⚠ Completion blocked — phantom card ids",
     suspected_hallucinated_references: "⚠ Prose referenced phantom card ids",
   };
+  const FALLBACK_TRASH = {
+    label: "Trash",
+    title: "Drag a card here to permanently delete it",
+    confirm: "Permanently delete this task? This cannot be undone.",
+    dropHint: "Drop to delete",
+  };
   const DIAGNOSTIC_EVENT_KIND_KEYS = {
     completion_blocked_hallucination: "completionBlockedHallucination",
     suspected_hallucinated_references: "suspectedHallucinatedReferences",
@@ -331,10 +337,12 @@
         const under = document.elementFromPoint(ev.clientX, ev.clientY);
         proxy.style.display = "";
         const col = under && under.closest && under.closest("[data-kanban-column]");
-        if (col !== lastTarget) {
+        const trash = under && under.closest && under.closest("[data-kanban-trash]");
+        const target = col || trash;
+        if (target !== lastTarget) {
           if (lastTarget) lastTarget.classList.remove("hermes-kanban-column--drop");
-          if (col) col.classList.add("hermes-kanban-column--drop");
-          lastTarget = col;
+          if (target) target.classList.add("hermes-kanban-column--drop");
+          lastTarget = target;
         }
       }
       function up() {
@@ -344,10 +352,18 @@
         if (lastTarget) {
           lastTarget.classList.remove("hermes-kanban-column--drop");
           const status = lastTarget.getAttribute("data-kanban-column");
-          lastTarget.dispatchEvent(new CustomEvent("hermes-kanban:drop", {
-            detail: { taskId, status },
-            bubbles: true,
-          }));
+          const isTrash = lastTarget.hasAttribute("data-kanban-trash");
+          if (isTrash) {
+            lastTarget.dispatchEvent(new CustomEvent("hermes-kanban:delete", {
+              detail: { taskId },
+              bubbles: true,
+            }));
+          } else if (status) {
+            lastTarget.dispatchEvent(new CustomEvent("hermes-kanban:drop", {
+              detail: { taskId, status },
+              bubbles: true,
+            }));
+          }
         }
         proxy.remove();
       }
@@ -878,6 +894,32 @@
       });
     }, [board, loadBoardList, switchBoard]);
 
+   const deleteTask = useCallback(function (taskId) {
+     if (!window.confirm(tx(t, "trash.confirm", FALLBACK_TRASH.confirm))) return Promise.resolve();
+     return SDK.fetchJSON(`${API}/tasks/${encodeURIComponent(taskId)}`, {
+       method: "DELETE",
+     }).then(function () {
+       loadBoard();
+       setSelectedIds(function (prev) {
+         const next = new Set(prev);
+         next.delete(taskId);
+         return next;
+       });
+     }).catch(function (e) { setError(String(e.message || e)); });
+   }, [board, loadBoard, t]);
+
+    const deleteSelected = useCallback(function (count) {
+      if (selectedIds.size === 0) return Promise.resolve();
+      if (!window.confirm(tx(t, "trash.confirmMany", "Permanently delete {n} selected tasks? This cannot be undone.", { n: count }))) return Promise.resolve();
+      const ids = Array.from(selectedIds);
+      setSelectedIds(new Set());
+      return Promise.all(ids.map(function (id) {
+        return SDK.fetchJSON(`${API}/tasks/${encodeURIComponent(id)}`, { method: "DELETE" });
+      })).then(function () {
+        loadBoard();
+      }).catch(function (e) { setError(String(e.message || e)); });
+    }, [selectedIds, board, loadBoard, t]);
+
     // --- render -------------------------------------------------------------
     if (loading && !boardData) {
       return h("div", { className: "p-8 text-sm text-muted-foreground" },
@@ -932,13 +974,14 @@
           },
           onRefresh: loadBoard,
         }),
-        selectedIds.size > 0 ? h(BulkActionBar, {
-          count: selectedIds.size,
-          assignees: (boardData && boardData.assignees) || [],
-          onApply: applyBulk,
-          onClear: clearSelected,
-          onSelectAllVisible: selectAllVisible,
-        }) : null,
+       selectedIds.size > 0 ? h(BulkActionBar, {
+         count: selectedIds.size,
+         assignees: (boardData && boardData.assignees) || [],
+         onApply: applyBulk,
+         onClear: clearSelected,
+         onSelectAllVisible: selectAllVisible,
+         onDelete: deleteSelected,
+       }) : null,
         error ? h("div", { className: "text-xs text-destructive px-2" }, error) : null,
         h(BoardColumns, {
           board: filteredBoard,
@@ -953,6 +996,7 @@
           selectAllInColumn,
           onMove: moveTask,
           onMoveSelected: moveSelected,
+          onDelete: deleteTask,
           onOpen: setSelectedTaskId,
           onCreate: createTask,
           allTasks: boardData.columns.reduce(function (acc, c) { return acc.concat(c.tasks); }, []),
@@ -2009,6 +2053,14 @@
         size: "sm",
         title: "Archive selected tasks. They disappear from the default board view but remain in the database.",
       }, tx(t, "archive", "Archive")),
+      h(Button, {
+        onClick: function () {
+          props.onDelete(props.count);
+        },
+        size: "sm",
+        variant: "destructive",
+        title: "Permanently delete selected tasks. This cannot be undone.",
+      }, tx(t, "delete", "Delete")),
       h("div", { className: "hermes-kanban-bulk-priority",
                  title: "Set priority on selected tasks. Higher = claimed first." },
         h(Input, {
@@ -2073,6 +2125,65 @@
     );
   }
 
+  // -------------------------------------------------------------------------
+  // Trash Drop Zone
+  // -------------------------------------------------------------------------
+
+  function TrashDropZone(props) {
+    const { t } = useI18n();
+    const [dragOver, setDragOver] = useState(false);
+    const zoneRef = useRef(null);
+
+    useEffect(function () {
+      if (!zoneRef.current) return undefined;
+      const el = zoneRef.current;
+      function onTouchDelete(e) {
+        const taskId = e.detail && e.detail.taskId;
+        if (taskId && props.onDelete) props.onDelete(taskId);
+      }
+      el.addEventListener("hermes-kanban:delete", onTouchDelete);
+      return function () { el.removeEventListener("hermes-kanban:delete", onTouchDelete); };
+    }, [props.onDelete]);
+
+    const handleDragOver = function (e) {
+      e.preventDefault();
+      e.dataTransfer.dropEffect = "move";
+      if (!dragOver) setDragOver(true);
+    };
+    const handleDragLeave = function () { setDragOver(false); };
+    const handleDrop = function (e) {
+      e.preventDefault();
+      setDragOver(false);
+      const taskId = e.dataTransfer.getData(MIME_TASK);
+      if (!taskId) return;
+      if (props.selectedIds && props.selectedIds.has(taskId) && props.selectedIds.size > 1) {
+        if (window.confirm(tx(t, "trash.confirmMany", "Permanently delete {n} selected tasks? This cannot be undone.", { n: props.selectedIds.size }))) {
+          const ids = Array.from(props.selectedIds);
+          Promise.all(ids.map(function (id) { return props.onDelete(id); })).catch(function () {});
+        }
+      } else {
+        props.onDelete(taskId);
+      }
+    };
+
+    return h("div", {
+      ref: zoneRef,
+      "data-kanban-trash": "true",
+      className: cn(
+        "hermes-kanban-trash",
+        dragOver ? "hermes-kanban-trash--drop" : "",
+        props.draggingTaskId ? "hermes-kanban-trash--active" : "",
+      ),
+      onDragOver: handleDragOver,
+      onDragLeave: handleDragLeave,
+      onDrop: handleDrop,
+    },
+      h("span", { className: "hermes-kanban-trash-icon" }, "🗑️"),
+      h("span", { className: "hermes-kanban-trash-label" },
+        tx(t, "trash.dropHint", FALLBACK_TRASH.dropHint)),
+    );
+  }
+
   // -------------------------------------------------------------------------
   // Columns
   // -------------------------------------------------------------------------
@@ -2106,6 +2217,11 @@
           allTasks: props.allTasks,
         });
       }),
+      h(TrashDropZone, {
+        draggingTaskId: props.draggingTaskId,
+        selectedIds: props.selectedIds,
+        onDelete: props.onDelete,
+      }),
     );
   }
 

plugins/kanban/dashboard/dist/style.css

@@ -1498,3 +1498,44 @@
   font-size: 0.7rem;
   cursor: pointer;
 }
+
+/* ---- Trash drop zone ------------------------------------------------- */
+
+.hermes-kanban-trash {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  gap: 0.35rem;
+  padding: 0.75rem 0.5rem;
+  border: 2px dashed var(--color-border);
+  border-radius: var(--radius);
+  background: color-mix(in srgb, var(--color-card) 85%, transparent);
+  color: var(--color-muted-foreground);
+  font-size: 0.75rem;
+  min-height: 80px;
+  opacity: 0.5;
+  transition: opacity 120ms ease, border-color 120ms ease, background-color 120ms ease;
+  user-select: none;
+  pointer-events: none;
+}
+
+.hermes-kanban-trash--active {
+  opacity: 1;
+  pointer-events: auto;
+}
+
+.hermes-kanban-trash--drop {
+  border-color: var(--color-destructive, #d14a4a);
+  background: color-mix(in srgb, var(--color-destructive, #d14a4a) 8%, var(--color-card));
+  color: var(--color-destructive, #d14a4a);
+}
+
+.hermes-kanban-trash-icon {
+  font-size: 1.25rem;
+  line-height: 1;
+}
+
+.hermes-kanban-trash-label {
+  font-weight: 500;
+}

plugins/kanban/dashboard/plugin_api.py

@@ -730,6 +730,23 @@ def update_task(task_id: str, payload: UpdateTaskBody, board: Optional[str] = Qu
         conn.close()
 
 
+# ---------------------------------------------------------------------------
+# DELETE /tasks/:id
+# ---------------------------------------------------------------------------
+
+@router.delete("/tasks/{task_id}")
+def delete_task(task_id: str, board: Optional[str] = Query(None)):
+    board = _resolve_board(board)
+    conn = _conn(board=board)
+    try:
+        ok = kanban_db.delete_task(conn, task_id)
+        if not ok:
+            raise HTTPException(status_code=404, detail=f"task {task_id} not found")
+        return {"deleted": True, "task_id": task_id}
+    finally:
+        conn.close()
+
+
 def _set_status_direct(
     conn: sqlite3.Connection, task_id: str, new_status: str,
 ) -> bool:

tests/hermes_cli/test_kanban_db.py

@@ -816,6 +816,34 @@ def test_list_tasks_order_by(kanban_home):
         except ValueError as e:
             assert "order_by must be one of" in str(e)
 
+def test_delete_task_removes_task_and_cascades(kanban_home):
+    with kb.connect() as conn:
+        t = kb.create_task(conn, title="to-delete", assignee="alice")
+        kb.add_comment(conn, t, "user", "comment")
+        kb.add_comment(conn, t, "user", "another")
+        assert kb.delete_task(conn, t)
+        assert kb.get_task(conn, t) is None
+        assert len(kb.list_comments(conn, t)) == 0
+        assert len(kb.list_events(conn, t)) == 0
+        assert len(kb.list_runs(conn, t)) == 0
+
+
+def test_delete_task_returns_false_for_missing_task(kanban_home):
+    with kb.connect() as conn:
+        assert not kb.delete_task(conn, "t_nonexistent")
+
+
+def test_delete_task_cascades_links(kanban_home):
+    with kb.connect() as conn:
+        p = kb.create_task(conn, title="parent")
+        c = kb.create_task(conn, title="child", parents=[p])
+        child = kb.get_task(conn, c)
+        assert child is not None and child.status == "todo"
+        kb.delete_task(conn, p)
+        assert kb.get_task(conn, p) is None
+        child_after = kb.get_task(conn, c)
+        assert child_after is not None and child_after.status == "ready"
+
 
 # ---------------------------------------------------------------------------
 # Comments / events / worker context

tests/plugins/test_kanban_dashboard_plugin.py

@@ -485,6 +485,33 @@ def test_patch_status_running_rejected(client):
     assert statuses.get(t["id"]) != "running"
 
 
+# ---------------------------------------------------------------------------
+# DELETE /tasks/:id
+# ---------------------------------------------------------------------------
+
+def test_delete_task(client):
+    t = client.post("/api/plugins/kanban/tasks", json={"title": "to-delete"}).json()["task"]
+    r = client.delete(f"/api/plugins/kanban/tasks/{t['id']}")
+    assert r.status_code == 200
+    assert r.json()["deleted"] is True
+    assert r.json()["task_id"] == t["id"]
+
+    # Gone from board
+    board = client.get("/api/plugins/kanban/board").json()
+    all_ids = [tt["id"] for col in board["columns"] for tt in col["tasks"]]
+    assert t["id"] not in all_ids
+
+    # Gone from detail
+    r = client.get(f"/api/plugins/kanban/tasks/{t['id']}")
+    assert r.status_code == 404
+
+
+def test_delete_task_not_found(client):
+    r = client.delete("/api/plugins/kanban/tasks/t_nonexistent")
+    assert r.status_code == 404
+    assert "not found" in r.json()["detail"]
+
+
 # ---------------------------------------------------------------------------
 # Comments + Links
 # ---------------------------------------------------------------------------