diff --git a/frontend/src/components/kanban/TaskEditForm.tsx b/frontend/src/components/kanban/TaskEditForm.tsx
index 91226ada..595b5237 100644
--- a/frontend/src/components/kanban/TaskEditForm.tsx
+++ b/frontend/src/components/kanban/TaskEditForm.tsx
@@ -71,13 +71,30 @@ export function TaskEditForm({
   const { t } = useTranslation("kanban");
   const { t: tc } = useTranslation("common");
 
+  // Cross-field check: a snooze date past the deadline
+  // is incoherent (the deadline badge would fire before
+  // the snooze even surfaces). Lex compare agrees with
+  // chronological order on ``YYYY-MM-DD``. The API
+  // mirrors this rule and returns 400 if it slips
+  // through, so this is purely instant-feedback UX.
+  const datesOutOfOrder = !!(
+    editScheduled
+    && editDeadline
+    && editDeadline < editScheduled
+  );
+
+  function handleSave() {
+    if (datesOutOfOrder) return;
+    onSave();
+  }
+
   function handleKeyDown(e: React.KeyboardEvent) {
     if (
       (e.metaKey || e.ctrlKey) &&
       e.key === "Enter"
     ) {
       e.preventDefault();
-      onSave();
+      handleSave();
     }
     if (e.key === "Escape") {
       onCancel();
@@ -155,6 +172,11 @@ export function TaskEditForm({
           />
         </label>
       </div>
+      {datesOutOfOrder && (
+        <p className="text-2xs text-red-500 px-0.5">
+          {t("datesOutOfOrder")}
+        </p>
+      )}
       <div
         onPointerDown={(e) => e.stopPropagation()}
       >
@@ -177,8 +199,8 @@ export function TaskEditForm({
         </button>
         <button
           onPointerDown={(e) => e.stopPropagation()}
-          onClick={onSave}
-          disabled={isSaving}
+          onClick={handleSave}
+          disabled={isSaving || datesOutOfOrder}
           className="p-1 text-cta hover:bg-cta-muted rounded disabled:opacity-40"
         >
           <Check size={12} />
diff --git a/frontend/src/locales/de/kanban.json b/frontend/src/locales/de/kanban.json
index efd7e8cb..e6cab72a 100644
--- a/frontend/src/locales/de/kanban.json
+++ b/frontend/src/locales/de/kanban.json
@@ -4,6 +4,7 @@
   "newTask": "Neue Aufgabe (Doppeltipp B)",
   "collapseColumn": "Spalte einklappen",
   "expandColumn": "Spalte ausklappen",
+  "datesOutOfOrder": "Frist muss am oder nach dem geplanten Datum liegen.",
   "scheduledLabel": "Geplant",
   "deadlineLabel": "Frist",
   "snoozedCount": "{{count}} geplant",
diff --git a/frontend/src/locales/en/kanban.json b/frontend/src/locales/en/kanban.json
index 73e6c85d..577a1596 100644
--- a/frontend/src/locales/en/kanban.json
+++ b/frontend/src/locales/en/kanban.json
@@ -4,6 +4,7 @@
   "newTask": "New task (double-tap B)",
   "collapseColumn": "Collapse column",
   "expandColumn": "Expand column",
+  "datesOutOfOrder": "Deadline must be on or after the scheduled date.",
   "scheduledLabel": "Scheduled",
   "deadlineLabel": "Deadline",
   "snoozedCount": "{{count}} snoozed",
diff --git a/frontend/src/locales/es/kanban.json b/frontend/src/locales/es/kanban.json
index 4f2e23ad..0971bb9b 100644
--- a/frontend/src/locales/es/kanban.json
+++ b/frontend/src/locales/es/kanban.json
@@ -4,6 +4,7 @@
   "newTask": "Nueva tarea (doble clic en B)",
   "collapseColumn": "Colapsar columna",
   "expandColumn": "Expandir columna",
+  "datesOutOfOrder": "La fecha límite debe ser igual o posterior a la fecha programada.",
   "scheduledLabel": "Programada",
   "deadlineLabel": "Fecha l\u00edmite",
   "snoozedCount": "{{count}} pospuestas",
diff --git a/frontend/src/locales/ru/kanban.json b/frontend/src/locales/ru/kanban.json
index 280f21dc..a22f16c4 100644
--- a/frontend/src/locales/ru/kanban.json
+++ b/frontend/src/locales/ru/kanban.json
@@ -4,6 +4,7 @@
   "newTask": "Новая задача (двойное нажатие B)",
   "collapseColumn": "Свернуть колонку",
   "expandColumn": "Развернуть колонку",
+  "datesOutOfOrder": "Срок должен быть не раньше запланированной даты.",
   "scheduledLabel": "Запланировано",
   "deadlineLabel": "Срок",
   "snoozedCount": "{{count}} отложено",
diff --git a/kaisho/api/routers/kanban.py b/kaisho/api/routers/kanban.py
index 3514bd74..8b26e836 100644
--- a/kaisho/api/routers/kanban.py
+++ b/kaisho/api/routers/kanban.py
@@ -1,5 +1,5 @@
 from fastapi import APIRouter, Body, HTTPException
-from pydantic import BaseModel
+from pydantic import BaseModel, model_validator
 
 from ...backends import get_backend
 from ...config import load_settings_yaml
@@ -7,6 +7,36 @@
 router = APIRouter(prefix="/api/kanban", tags=["kanban"])
 
 
+def _reject_deadline_before_scheduled(
+    scheduled: str | None, deadline: str | None,
+) -> None:
+    """Raise ``ValueError`` when the user has supplied
+    both dates in the same payload and the deadline lands
+    before the scheduled (snooze) date.
+
+    A snoozed-past-its-deadline task is incoherent — the
+    deadline badge would fire before the snooze even
+    surfaces — and is almost certainly a typo. Lexicographic
+    compare on ``YYYY-MM-DD`` agrees with chronological
+    order, so a plain string compare is enough.
+
+    On ``TaskUpdate`` this only catches the "user sent
+    both at once" case; sending just one that breaks the
+    invariant against the stored other is not validated
+    here (the frontend has the merged shape and can do
+    that check). Catching the typo at the API boundary is
+    the higher-value safety net.
+    """
+    if not scheduled or not deadline:
+        return
+    if deadline < scheduled:
+        raise ValueError(
+            "deadline must be on or after scheduled date "
+            f"(got scheduled={scheduled}, "
+            f"deadline={deadline})"
+        )
+
+
 class TaskCreate(BaseModel):
     customer: str = ""
     title: str
@@ -20,6 +50,13 @@ class TaskCreate(BaseModel):
     scheduled: str | None = None
     deadline: str | None = None
 
+    @model_validator(mode="after")
+    def _check_dates(self) -> "TaskCreate":
+        _reject_deadline_before_scheduled(
+            self.scheduled, self.deadline,
+        )
+        return self
+
 
 class TaskUpdate(BaseModel):
     status: str | None = None
@@ -32,6 +69,13 @@ class TaskUpdate(BaseModel):
     scheduled: str | None = None
     deadline: str | None = None
 
+    @model_validator(mode="after")
+    def _check_dates(self) -> "TaskUpdate":
+        _reject_deadline_before_scheduled(
+            self.scheduled, self.deadline,
+        )
+        return self
+
 
 class TagsUpdate(BaseModel):
     tags: list[str]
diff --git a/kaisho/cli/task.py b/kaisho/cli/task.py
index 7b90b178..af687b87 100644
--- a/kaisho/cli/task.py
+++ b/kaisho/cli/task.py
@@ -24,6 +24,12 @@ def _format_task_line(task: dict) -> str:
     if tag_str:
         parts.append(tag_str)
     parts.append(created)
+    scheduled = task.get("scheduled")
+    deadline = task.get("deadline")
+    if scheduled:
+        parts.append(f"scheduled:{scheduled}")
+    if deadline:
+        parts.append(f"deadline:{deadline}")
     return "  ".join(parts)
 
 
@@ -41,10 +47,16 @@ def task():
               help="Task body/description")
 @click.option("--github-url", default=None,
               help="GitHub issue/PR URL")
+@click.option("--scheduled", default=None,
+              help="Snooze date (YYYY-MM-DD). "
+                   "Task hidden until that day arrives.")
+@click.option("--deadline", default=None,
+              help="Deadline date (YYYY-MM-DD).")
 @click.option("--json", "as_json", is_flag=True,
               help="JSON output")
 def task_add(customer_name, title, tags, status,
-             body, github_url, as_json):
+             body, github_url, scheduled, deadline,
+             as_json):
     """Add a new task."""
     backend = get_backend()
     backend.customers.ensure_customer(customer_name or "")
@@ -55,6 +67,8 @@ def task_add(customer_name, title, tags, status,
         tags=list(tags),
         body=body,
         github_url=github_url,
+        scheduled=scheduled,
+        deadline=deadline,
     )
     if as_json:
         click.echo(json.dumps(result, default=str))
@@ -187,9 +201,15 @@ def task_show(task_id, as_json):
               help="New body text")
 @click.option("--github-url", default=None,
               help="GitHub issue/PR URL")
+@click.option("--scheduled", default=None,
+              help="Snooze date (YYYY-MM-DD). "
+                   "Pass empty string to clear.")
+@click.option("--deadline", default=None,
+              help="Deadline date (YYYY-MM-DD). "
+                   "Pass empty string to clear.")
 @click.option("--json", "as_json", is_flag=True)
 def task_update(task_id, title, customer, body,
-                github_url, as_json):
+                github_url, scheduled, deadline, as_json):
     """Update a task's fields."""
     result = get_backend().tasks.update_task(
         task_id=task_id,
@@ -197,6 +217,8 @@ def task_update(task_id, title, customer, body,
         customer=customer,
         body=body,
         github_url=github_url,
+        scheduled=scheduled,
+        deadline=deadline,
     )
     if as_json:
         click.echo(json.dumps(result, default=str))
diff --git a/kaisho/cron/tool_defs.py b/kaisho/cron/tool_defs.py
index 56d80260..df4f5c44 100644
--- a/kaisho/cron/tool_defs.py
+++ b/kaisho/cron/tool_defs.py
@@ -19,8 +19,10 @@
         "name": "list_tasks",
         "tier": "read",
         "description": (
-            "List tasks from the kanban board. "
-            "Returns id, customer, title, status, tags for each task."
+            "List tasks from the kanban board. Returns "
+            "id, customer, title, status, tags, scheduled "
+            "(snooze date, YYYY-MM-DD or null), and "
+            "deadline (YYYY-MM-DD or null) for each task."
         ),
         "input_schema": {
             "type": "object",
diff --git a/tests/test_api.py b/tests/test_api.py
index 09d93f3c..f396b4ee 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -285,6 +285,65 @@ def test_create_missing_title(self, client):
         )
         assert r.status_code == 422
 
+    def test_create_rejects_deadline_before_scheduled(
+        self, client,
+    ):
+        """A snoozed-past-its-deadline task is incoherent
+        (deadline badge would fire before the snooze even
+        surfaces). The API rejects with 422 when both
+        dates are set and deadline < scheduled."""
+        r = client.post(
+            "/api/kanban/tasks",
+            json={
+                "customer": "Acme",
+                "title": "Incoherent",
+                "scheduled": "2099-06-15",
+                "deadline": "2099-06-10",
+            },
+        )
+        assert r.status_code == 422
+        assert "scheduled" in r.text.lower()
+
+    def test_create_allows_deadline_equal_scheduled(
+        self, client,
+    ):
+        """Same-day scheduled/deadline is legal — the
+        snooze surfaces and the deadline lands on the
+        same day, no contradiction."""
+        r = client.post(
+            "/api/kanban/tasks",
+            json={
+                "customer": "Acme",
+                "title": "Same day",
+                "scheduled": "2099-06-15",
+                "deadline": "2099-06-15",
+            },
+        )
+        assert r.status_code == 201
+
+    def test_update_rejects_deadline_before_scheduled(
+        self, client,
+    ):
+        """The cross-field check applies to PATCH too —
+        the user can't slip an invalid pair in via an
+        edit that sends both fields at once."""
+        r = client.post(
+            "/api/kanban/tasks",
+            json={
+                "customer": "Acme",
+                "title": "Edit me",
+            },
+        )
+        task_id = r.json()["id"]
+        r = client.patch(
+            f"/api/kanban/tasks/{task_id}",
+            json={
+                "scheduled": "2099-06-15",
+                "deadline": "2099-06-10",
+            },
+        )
+        assert r.status_code == 422
+
 
 # ── Clocks ──────────────────────────────────────────────