apps/web/cypress/e2e/planning-leftovers.feature

@@ -0,0 +1,24 @@
+Feature: Serving leftovers from the planning basket
+  As a signed-in user
+  I want to drag a week's leftovers onto another slot
+  So that I don't cook a fresh batch for a meal an existing one already covers
+
+  Background:
+    Given I am signed in as "Alice" "Martin"
+    And my household id is 1
+    And the planning has a batch with leftovers to spare
+
+  Scenario: Drag a leftover onto another slot, confirm the portions, and see the "restes" chip
+    When I visit "/"
+    And I open the leftovers basket
+    Then the leftovers basket lists "Lasagnes" with 2 portions
+    When I drag the "Lasagnes" leftover onto Wednesday lunch
+    And I confirm serving 2 leftover portions
+    Then Wednesday lunch shows a leftovers chip for "Lasagnes"
+    And the leftovers basket count is gone
+
+  Scenario: Throw a leftover away from the basket
+    When I visit "/"
+    And I open the leftovers basket
+    And I throw away the "Lasagnes" leftover
+    Then the leftovers basket shows nothing left

apps/web/cypress/e2e/planning-leftovers.ts

@@ -0,0 +1,132 @@
+import { Given, Then, When } from "@badeball/cypress-cucumber-preprocessor";
+
+// Mocks the API via cy.intercept — this job has no live backend (see
+// .github/workflows/ci.yml); apps/api's Mocha suite covers the real
+// leftover endpoints. Drives @dnd-kit's MouseSensor with raw mouse
+// events (mousedown on the handle → two mousemoves → mouseup on the
+// target), the reliable way to script one of its drags in Cypress.
+
+/** One fresh batch: 12 prepared for 10 requested -> a pool of 2, no leftovers item pointing at it yet. */
+const SOURCE_ITEM = {
+  id: 1,
+  weekDay: "lundi",
+  meal: "diner",
+  portions: 12,
+  portionsRequested: 10,
+  discardedPortions: 0,
+  sourceItem: null,
+  recipe: { id: 1, name: "Lasagnes" },
+};
+
+Given("the planning has a batch with leftovers to spare", () => {
+  cy.intercept("GET", "**/profile/disliked-ingredients", { statusCode: 200, body: [] });
+  cy.intercept("GET", /\/planning\?/, {
+    statusCode: 200,
+    body: {
+      id: 1,
+      startDate: "2026-08-17T00:00:00.000Z",
+      finishDate: "2026-08-23T00:00:00.000Z",
+      items: [SOURCE_ITEM],
+    },
+  }).as("getPlanning");
+});
+
+When("I open the leftovers basket", () => {
+  cy.get(".leftovers-basket__toggle").click();
+});
+
+Then(
+  "the leftovers basket lists {string} with {int} portions",
+  (recipe: string, portions: number) => {
+    cy.contains(".leftovers-basket__line", recipe).should("contain.text", `${portions} en restes`);
+  },
+);
+
+/** dnd-kit's MouseSensor listens on the drag element for `mousedown`, then on the document for `mousemove`/`mouseup`; a first move past the 5px activation distance, then a move onto the target, then release. */
+function dragLeftoverOnto(targetSelectorChain: () => Cypress.Chainable<JQuery<HTMLElement>>) {
+  cy.get(".leftovers-basket__drag-handle")
+    .first()
+    .then(($handle) => {
+      const h = $handle[0].getBoundingClientRect();
+      const start = {
+        clientX: Math.round(h.left + h.width / 2),
+        clientY: Math.round(h.top + h.height / 2),
+      };
+      targetSelectorChain().then(($target) => {
+        const t = $target[0].getBoundingClientRect();
+        const end = {
+          clientX: Math.round(t.left + t.width / 2),
+          clientY: Math.round(t.top + t.height / 2),
+        };
+        cy.wrap($handle).trigger("mousedown", { button: 0, ...start });
+        cy.get("body")
+          .trigger("mousemove", {
+            button: 0,
+            clientX: start.clientX + 12,
+            clientY: start.clientY + 12,
+          })
+          .trigger("mousemove", { button: 0, ...end })
+          .trigger("mouseup", { button: 0, ...end });
+      });
+    });
+}
+
+/** The `<td>` for (Wednesday, lunch): MEALS order puts `dejeuner` at row index 2, WEEK_DAYS puts `mercredi` at td index 2. */
+function wednesdayLunchCell() {
+  return cy.get(".planning-grid tbody tr").eq(2).find("td").eq(2);
+}
+
+When("I drag the {string} leftover onto Wednesday lunch", (_recipe: string) => {
+  cy.intercept("POST", "**/planning/items/leftover", (req) => {
+    req.reply({
+      statusCode: 201,
+      body: {
+        id: 99,
+        weekDay: "mercredi",
+        meal: "dejeuner",
+        portions: req.body.portions,
+        portionsRequested: req.body.portions,
+        discardedPortions: 0,
+        sourceItem: { id: req.body.sourceItemId },
+        recipe: { id: 1, name: "Lasagnes" },
+      },
+    });
+  }).as("assignLeftover");
+
+  dragLeftoverOnto(wednesdayLunchCell);
+});
+
+When("I confirm serving {int} leftover portions", (portions: number) => {
+  cy.get("#leftover-assign-portions").clear().type(String(portions));
+  cy.contains(".recipe-picker-confirm__confirm", "Ajouter au planning").click();
+  cy.wait("@assignLeftover").its("request.body").should("deep.include", {
+    sourceItemId: 1,
+    weekDay: "mercredi",
+    meal: "dejeuner",
+    portions,
+  });
+});
+
+Then("Wednesday lunch shows a leftovers chip for {string}", (recipe: string) => {
+  wednesdayLunchCell()
+    .find(".recipe-chip--leftover")
+    .should("contain.text", recipe)
+    .and("contain.text", "♻️");
+});
+
+Then("the leftovers basket count is gone", () => {
+  cy.get(".leftovers-basket__count").should("not.exist");
+});
+
+When("I throw away the {string} leftover", (recipe: string) => {
+  cy.intercept("PATCH", "**/planning/items/1/discard-leftover", {
+    statusCode: 200,
+    body: { ...SOURCE_ITEM, discardedPortions: 2 },
+  }).as("discard");
+  cy.contains(".leftovers-basket__line", recipe).find(".leftovers-basket__discard").click();
+  cy.wait("@discard");
+});
+
+Then("the leftovers basket shows nothing left", () => {
+  cy.contains(".leftovers-basket__empty", "Aucun reste cette semaine.").should("be.visible");
+});

apps/web/package.json

@@ -16,6 +16,8 @@
   "dependencies": {
     "@batch-cooking/date-tools": "workspace:*",
     "@batch-cooking/shared": "workspace:*",
+    "@dnd-kit/core": "^6.3.1",
+    "@dnd-kit/utilities": "^3.2.2",
     "i18next": "^26.3.6",
     "lucide-react": "^1.32.0",
     "react": "^18.3.1",

apps/web/src/api/client.ts

@@ -2,6 +2,7 @@ import {
   type AddPlanningItemInput,
   type AllergyView,
   type ApiErrorResponse,
+  type AssignLeftoverInput,
   type BrowsableSourceItemView,
   type CreateRecipeInput,
   type DietView,
@@ -171,6 +172,14 @@ export class ApiClient {
     return this._request(`/planning/items/${id}/discard-leftover`, { method: "PATCH" });
   }
 
+  /** Serves `portions` of a source item's leftover pool on a slot, creating a "leftovers" planning item (same recipe as the source). Rejects with `LEFTOVER_QUANTITY_EXCEEDED` (over the pool) or `PLANNING_ITEM_NOT_FOUND`. */
+  public assignLeftover(input: AssignLeftoverInput): Promise<PlanningItemView> {
+    return this._request("/planning/items/leftover", {
+      method: "POST",
+      body: JSON.stringify(input),
+    });
+  }
+
   /**
    * Fetches the current user's household's shopping list for the week
    * covering `date` (`YYYY-MM-DD`, e.g. from `date-tools`'s

apps/web/src/features/planning/LeftoverAssignDialog.tsx

@@ -0,0 +1,81 @@
+import { useState } from "react";
+import { useTranslation } from "react-i18next";
+import { Dialog } from "../../components/ui/Dialog";
+
+/**
+ * The little "how many portions?" step shown after a leftover card is
+ * dropped onto a planning slot — same shape/style as `RecipePickerDialog`'s
+ * own portions step (`.recipe-picker-confirm`). Defaults to the whole
+ * available pool, capped at it; `onConfirm` does the actual
+ * `POST /planning/items/leftover` and reports back a rejection message to
+ * show inline.
+ */
+export function LeftoverAssignDialog({
+  recipeName,
+  available,
+  onCancel,
+  onConfirm,
+}: {
+  recipeName: string;
+  available: number;
+  onCancel: () => void;
+  /** Resolves to an error label to display, or `null` on success (the caller closes the dialog itself). */
+  onConfirm: (portions: number) => Promise<string | null>;
+}) {
+  const { t } = useTranslation();
+  const [portions, setPortions] = useState(String(available));
+  const [error, setError] = useState<string | null>(null);
+  const [isSubmitting, setIsSubmitting] = useState(false);
+
+  const parsed = Number(portions);
+  const isValid = Number.isInteger(parsed) && parsed >= 1 && parsed <= available;
+
+  async function submit() {
+    if (!isValid) return;
+    setIsSubmitting(true);
+    setError(null);
+    try {
+      const message = await onConfirm(parsed);
+      if (message !== null) {
+        setError(message);
+        setIsSubmitting(false);
+      }
+    } catch {
+      setError(t("errors.INTERNAL_ERROR"));
+      setIsSubmitting(false);
+    }
+  }
+
+  return (
+    <Dialog onClose={onCancel} title={t("planning.leftovers.assignTitle", { recipe: recipeName })}>
+      <div className="recipe-picker-confirm">
+        <label htmlFor="leftover-assign-portions">
+          {t("planning.leftovers.assignPortionsLabel", { max: available })}
+        </label>
+        <input
+          id="leftover-assign-portions"
+          type="number"
+          min="1"
+          max={available}
+          step="1"
+          value={portions}
+          onChange={(e) => setPortions(e.target.value)}
+        />
+        {error && <p className="field-error">{error}</p>}
+        <div className="recipe-picker-confirm__actions">
+          <button type="button" onClick={onCancel} disabled={isSubmitting}>
+            {t("planning.leftovers.assignCancel")}
+          </button>
+          <button
+            type="button"
+            className="recipe-picker-confirm__confirm"
+            onClick={() => void submit()}
+            disabled={isSubmitting || !isValid}
+          >
+            {isSubmitting ? t("planning.picker.adding") : t("planning.leftovers.assignConfirm")}
+          </button>
+        </div>
+      </div>
+    </Dialog>
+  );
+}

apps/web/src/features/planning/LeftoversBasket.tsx

@@ -1,8 +1,9 @@
 import type { PlanningItemView, PlanningView } from "@batch-cooking/shared";
+import { useDraggable } from "@dnd-kit/core";
 import { useEffect, useRef, useState } from "react";
 import { useTranslation } from "react-i18next";
 import { apiClient } from "../../api/client";
-import { collectLeftoverLines } from "./leftovers-basket";
+import { collectLeftoverLines, dragIdForLeftover } from "./leftovers-basket";
 import "./leftovers-basket.scss";
 
 /**
@@ -11,12 +12,13 @@ import "./leftovers-basket.scss";
  * one line per fresh planning item that cooked more than it needed, with
  * where it came from, how many portions are left, and a "jeter" button.
  *
- * Read-only for now: dragging a leftover onto another slot arrives in a
+ * Each line is also draggable (`@dnd-kit`, see {@link LeftoverLineCard})
- * later iteration. Same conditional-mount + outside-click-to-close pattern
+ * onto a planning cell to serve part of its pool there — `PlanningPage`
- * as `WeekNavigator`'s `CalendarPopover`. The list is derived on every
+ * owns the `DndContext` and the drop handling. Same conditional-mount +
- * render from `planning` (see {@link collectLeftoverLines}) rather than
+ * outside-click-to-close pattern as `WeekNavigator`'s `CalendarPopover`.
- * held in its own state, so a discard elsewhere on the page is reflected
+ * The list is derived on every render from `planning` (see
- * here for free.
+ * {@link collectLeftoverLines}) rather than held in its own state, so a
+ * discard or assignment elsewhere on the page is reflected here for free.
  */
 export function LeftoversBasket({
   planning,
@@ -79,28 +81,13 @@ export function LeftoversBasket({
           ) : (
             <ul className="leftovers-basket__list">
               {lines.map(({ item, available }) => (
-                <li key={item.id} className="leftovers-basket__line">
+                <LeftoverLineCard
-                  <div className="leftovers-basket__meta">
+                  key={item.id}
-                    <span className="leftovers-basket__recipe">{item.recipe.name}</span>
+                  item={item}
-                    <span className="leftovers-basket__origin">
+                  available={available}
-                      {t("planning.leftovers.origin", {
+                  isDiscarding={discardingId === item.id}
-                        day: t(`common.days.${item.weekDay}`),
+                  onDiscard={() => void discard(item)}
-                        meal: t(`planning.meals.${item.meal}`),
+                />
-                      })}
-                    </span>
-                  </div>
-                  <span className="leftovers-basket__qty">
-                    {t("planning.leftovers.available", { count: available })}
-                  </span>
-                  <button
-                    type="button"
-                    className="leftovers-basket__discard"
-                    onClick={() => void discard(item)}
-                    disabled={discardingId === item.id}
-                  >
-                    {t("planning.leftovers.discard")}
-                  </button>
-                </li>
               ))}
             </ul>
           )}
@@ -109,3 +96,66 @@ export function LeftoversBasket({
     </div>
   );
 }
+
+/**
+ * One basket line, draggable (`@dnd-kit` `useDraggable`) onto a planning
+ * cell to serve part of its pool there. The drag `data` carries what
+ * `PlanningPage`'s `onDragEnd` needs to open the "how many portions?"
+ * step; the sensors' activation distance (see `PlanningPage`) keeps a
+ * plain click on "Jeter" from starting a drag.
+ */
+function LeftoverLineCard({
+  item,
+  available,
+  isDiscarding,
+  onDiscard,
+}: {
+  item: PlanningItemView;
+  available: number;
+  isDiscarding: boolean;
+  onDiscard: () => void;
+}) {
+  const { t } = useTranslation();
+  // The draggable node is the small grip button, not the whole `<li>`: a
+  // pointer-based collision test then resolves cleanly to the single cell
+  // under the cursor (a wide `<li>` box would straddle several cells).
+  const { attributes, listeners, setNodeRef, isDragging } = useDraggable({
+    id: dragIdForLeftover(item.id),
+    data: { sourceItemId: item.id, recipeName: item.recipe.name, available },
+  });
+
+  return (
+    <li className={isDragging ? "leftovers-basket__line is-dragging" : "leftovers-basket__line"}>
+      <button
+        type="button"
+        ref={setNodeRef}
+        className="leftovers-basket__drag-handle"
+        aria-label={t("planning.leftovers.dragHandle", { recipe: item.recipe.name })}
+        {...attributes}
+        {...listeners}
+      >
+        ⠿
+      </button>
+      <div className="leftovers-basket__meta">
+        <span className="leftovers-basket__recipe">{item.recipe.name}</span>
+        <span className="leftovers-basket__origin">
+          {t("planning.leftovers.origin", {
+            day: t(`common.days.${item.weekDay}`),
+            meal: t(`planning.meals.${item.meal}`),
+          })}
+        </span>
+      </div>
+      <span className="leftovers-basket__qty">
+        {t("planning.leftovers.available", { count: available })}
+      </span>
+      <button
+        type="button"
+        className="leftovers-basket__discard"
+        onClick={onDiscard}
+        disabled={isDiscarding}
+      >
+        {t("planning.leftovers.discard")}
+      </button>
+    </li>
+  );
+}

apps/web/src/features/planning/leftovers-basket.scss

@@ -69,6 +69,29 @@
     display: flex;
     align-items: center;
     gap: var(--space-sm);
+
+    &.is-dragging {
+      opacity: 0.5;
+    }
+  }
+
+  // Grip handle — the only part that starts a drag, so a click on "Jeter"
+  // never gets hijacked. `touch-action: none` lets @dnd-kit's PointerSensor
+  // own the gesture on touch devices.
+  &__drag-handle {
+    flex-shrink: 0;
+    padding: 0 var(--space-xs);
+    font-size: var(--font-size-base);
+    line-height: 1;
+    cursor: grab;
+    color: var(--color-text-muted);
+    background: none;
+    border: none;
+    touch-action: none;
+
+    &:active {
+      cursor: grabbing;
+    }
   }
 
   &__meta {

apps/web/src/features/planning/leftovers-basket.ts

@@ -11,6 +11,18 @@ export interface LeftoverLine {
   available: number;
 }
 
+/** Payload a dragged leftover card carries (`useDraggable`'s `data`) — read by `PlanningPage`'s `onDragEnd` to pre-fill the assign step. */
+export interface LeftoverDragData {
+  sourceItemId: number;
+  recipeName: string;
+  available: number;
+}
+
+/** `useDraggable` id for one leftover line — namespaced so it can't collide with a droppable cell's id. */
+export function dragIdForLeftover(itemId: number): string {
+  return `leftover-${itemId}`;
+}
+
 /**
  * The leftovers-basket rows for a week's planning: every **fresh** item
  * (`sourceItem === null`) whose leftover pool still has something in it,

apps/web/src/locales/fr/translation.json

@@ -131,7 +131,13 @@
       "empty": "Aucun reste cette semaine.",
       "origin": "{{day}} · {{meal}}",
       "available": "{{count}} en restes",
-      "discard": "Jeter"
+      "discard": "Jeter",
+      "dragHandle": "Glisser les restes de {{recipe}} vers un créneau",
+      "chipBadge": "Restes d'un autre créneau",
+      "assignTitle": "Servir des restes de {{recipe}}",
+      "assignPortionsLabel": "Portions à servir (max {{max}})",
+      "assignCancel": "Annuler",
+      "assignConfirm": "Ajouter au planning"
     },
     "meals": {
       "petit-dejeuner": "Petit-déjeuner",

apps/web/src/pages/planning/PlanningPage.tsx

@@ -1,20 +1,57 @@
 import { DateTime, formatDateOnly, getWeekStart, toDateOnly } from "@batch-cooking/date-tools";
 import {
+  ErrorCode,
   MEALS,
   type Meal,
   type PlanningItemView,
   type PlanningView,
   WEEK_DAYS,
+  type WeekDay,
 } from "@batch-cooking/shared";
+import {
+  type CollisionDetection,
+  closestCenter,
+  DndContext,
+  type DragEndEvent,
+  KeyboardSensor,
+  MouseSensor,
+  pointerWithin,
+  TouchSensor,
+  useDroppable,
+  useSensor,
+  useSensors,
+} from "@dnd-kit/core";
 import { useEffect, useState } from "react";
 import { useTranslation } from "react-i18next";
 import { useNavigate } from "react-router-dom";
-import { apiClient } from "../../api/client";
+import { ApiError, apiClient } from "../../api/client";
+import { LeftoverAssignDialog } from "../../features/planning/LeftoverAssignDialog";
 import { LeftoversBasket } from "../../features/planning/LeftoversBasket";
+import type { LeftoverDragData } from "../../features/planning/leftovers-basket";
 import { type PlanningSlot, RecipePickerDialog } from "../../features/planning/RecipePickerDialog";
 import { WeekNavigator } from "../../features/planning/WeekNavigator";
+import { errorMessageService } from "../../services/error-message.service";
 import "./planning-page.scss";
 
+/** Drop-target payload each planning cell registers (`useDroppable`'s `data`) — the slot a dragged leftover lands on. */
+interface CellDropData {
+  date: string;
+  weekDay: WeekDay;
+  meal: Meal;
+}
+
+/**
+ * Drop onto whichever cell the pointer is actually over; fall back to the
+ * nearest cell centre only when the pointer isn't inside any (e.g. the
+ * keyboard sensor, which has no pointer). Cells are packed edge to edge, so
+ * a rect-overlap strategy would pick a neighbour whenever the small drag
+ * handle's translated box crossed a border.
+ */
+const dropOnCellUnderPointer: CollisionDetection = (args) => {
+  const underPointer = pointerWithin(args);
+  return underPointer.length > 0 ? underPointer : closestCenter(args);
+};
+
 /** Load state for the `GET /planning` call — a discriminated union so a stale/impossible combination (e.g. "loading" with data) can't be represented. */
 type PlanningState =
   | { status: "loading" }
@@ -48,6 +85,22 @@ export function PlanningPage() {
   // state for free on every open, same convention as `WeekNavigator`'s own
   // `CalendarPopover` (features/planning/WeekNavigator.tsx).
   const [openSlot, setOpenSlot] = useState<PlanningSlot | null>(null);
+  // A leftover card has been dropped on a slot and we're asking how many of
+  // its pool to serve there — `null` means no such step is open.
+  const [pendingAssign, setPendingAssign] = useState<(LeftoverDragData & CellDropData) | null>(
+    null,
+  );
+
+  // Mouse + touch rather than the unified PointerSensor: same coverage, but
+  // driven by plain mouse/touch events, which Cypress can script reliably
+  // (see `planning-leftovers.ts`). A small activation distance so a plain
+  // click on a basket line's "Jeter" button doesn't start a drag; the
+  // keyboard sensor keeps the whole flow reachable without a pointer.
+  const sensors = useSensors(
+    useSensor(MouseSensor, { activationConstraint: { distance: 5 } }),
+    useSensor(TouchSensor, { activationConstraint: { delay: 150, tolerance: 5 } }),
+    useSensor(KeyboardSensor),
+  );
 
   useEffect(() => {
     let cancelled = false;
@@ -99,6 +152,35 @@ export function PlanningPage() {
     patchPlanningItems((items) => items.map((i) => (i.id === updated.id ? updated : i)));
   }
 
+  /** A leftover card was dropped on a cell — open the "how many portions?" step for that (source, slot) pair. */
+  function handleDragEnd(event: DragEndEvent) {
+    const drag = event.active.data.current as LeftoverDragData | undefined;
+    const cell = event.over?.data.current as CellDropData | undefined;
+    if (!drag || !cell) return;
+    setPendingAssign({ ...drag, ...cell });
+  }
+
+  /** Confirms the assign step — `POST /planning/items/leftover`, then patches the new "leftovers" item into local state. Returns an error label to show inline, or `null` on success. */
+  async function confirmAssign(portions: number): Promise<string | null> {
+    if (!pendingAssign) return null;
+    try {
+      const item = await apiClient.assignLeftover({
+        date: pendingAssign.date,
+        weekDay: pendingAssign.weekDay,
+        meal: pendingAssign.meal,
+        sourceItemId: pendingAssign.sourceItemId,
+        portions,
+      });
+      patchPlanningItems((items) => [...items, item]);
+      setPendingAssign(null);
+      return null;
+    } catch (err) {
+      return errorMessageService.getLabel(
+        err instanceof ApiError ? err.code : ErrorCode.INTERNAL_ERROR,
+      );
+    }
+  }
+
   /** Optimistic removal (same rollback-on-failure idea as `FavoriteStarButton`) — the API call already happened by the time this needs to roll back, `removePlanningItem` having already rejected. */
   async function handleRemove(item: PlanningItemView) {
     patchPlanningItems((items) => items.filter((i) => i.id !== item.id));
@@ -114,53 +196,68 @@ export function PlanningPage() {
   const hasPlannedRecipes = state.status === "loaded" && (state.planning?.items.length ?? 0) > 0;
 
   return (
-    <div className="planning-page">
+    <DndContext
-      <div className="planning-page__header">
+      sensors={sensors}
-        <h1>{t("planning.title")}</h1>
+      collisionDetection={dropOnCellUnderPointer}
-        <WeekNavigator weekStart={weekStart} onChangeWeek={setWeekStart} />
+      onDragEnd={handleDragEnd}
+    >
+      <div className="planning-page">
+        <div className="planning-page__header">
+          <h1>{t("planning.title")}</h1>
+          <WeekNavigator weekStart={weekStart} onChangeWeek={setWeekStart} />
+          {state.status === "loaded" && (
+            <LeftoversBasket
+              planning={state.planning}
+              onLeftoverDiscarded={handleLeftoverDiscarded}
+            />
+          )}
+          <button
+            type="button"
+            className="planning-page__cook-btn"
+            disabled={!hasPlannedRecipes}
+            onClick={() => navigate(`/cuisiner?date=${formatDateOnly(weekStart)}`)}
+          >
+            {t("planning.startCooking")}
+          </button>
+        </div>
+
+        {state.status === "loading" && (
+          <p className="planning-page__status">{t("planning.loading")}</p>
+        )}
+
+        {state.status === "error" && (
+          <p className="planning-page__status planning-page__status--error">
+            {t("common.loadError")}
+          </p>
+        )}
+
         {state.status === "loaded" && (
-          <LeftoversBasket
+          <PlanningGrid
+            weekStart={weekStart}
             planning={state.planning}
-            onLeftoverDiscarded={handleLeftoverDiscarded}
+            onAddSlot={setOpenSlot}
+            onRemoveItem={handleRemove}
+          />
+        )}
+
+        {openSlot && (
+          <RecipePickerDialog
+            slot={openSlot}
+            onClose={() => setOpenSlot(null)}
+            onAdded={handleAdded}
+          />
+        )}
+
+        {pendingAssign && (
+          <LeftoverAssignDialog
+            recipeName={pendingAssign.recipeName}
+            available={pendingAssign.available}
+            onCancel={() => setPendingAssign(null)}
+            onConfirm={confirmAssign}
           />
         )}
-        <button
-          type="button"
-          className="planning-page__cook-btn"
-          disabled={!hasPlannedRecipes}
-          onClick={() => navigate(`/cuisiner?date=${formatDateOnly(weekStart)}`)}
-        >
-          {t("planning.startCooking")}
-        </button>
       </div>
-
+    </DndContext>
-      {state.status === "loading" && (
-        <p className="planning-page__status">{t("planning.loading")}</p>
-      )}
-
-      {state.status === "error" && (
-        <p className="planning-page__status planning-page__status--error">
-          {t("common.loadError")}
-        </p>
-      )}
-
-      {state.status === "loaded" && (
-        <PlanningGrid
-          weekStart={weekStart}
-          planning={state.planning}
-          onAddSlot={setOpenSlot}
-          onRemoveItem={handleRemove}
-        />
-      )}
-
-      {openSlot && (
-        <RecipePickerDialog
-          slot={openSlot}
-          onClose={() => setOpenSlot(null)}
-          onAdded={handleAdded}
-        />
-      )}
-    </div>
   );
 }
 
@@ -203,6 +300,9 @@ function PlanningGrid({
                 <MealCell
                   key={weekDay}
                   isToday={date.hasSame(today, "day")}
+                  date={formatDateOnly(date)}
+                  weekDay={weekDay}
+                  meal={meal}
                   items={items.filter((item) => item.weekDay === weekDay && item.meal === meal)}
                   onAdd={() => onAddSlot({ date: formatDateOnly(date), weekDay, meal })}
                   onRemove={onRemoveItem}
@@ -216,28 +316,55 @@ function PlanningGrid({
   );
 }
 
-/** One (day, meal) cell: the recipes already planned for it (as pills, each showing its portion count) plus the "+" to add another. */
+/** One (day, meal) cell: the recipes already planned for it (as pills, each showing its portion count) plus the "+" to add another. Also a `@dnd-kit` drop target for a leftover card. */
 function MealCell({
   isToday,
+  date,
+  weekDay,
+  meal,
   items,
   onAdd,
   onRemove,
 }: {
   isToday: boolean;
+  date: string;
+  weekDay: WeekDay;
+  meal: Meal;
   items: PlanningItemView[];
   onAdd: () => void;
   onRemove: (item: PlanningItemView) => void;
 }) {
   const { t } = useTranslation();
+  const { setNodeRef, isOver } = useDroppable({
+    id: `cell-${weekDay}-${meal}`,
+    data: { date, weekDay, meal } satisfies CellDropData,
+  });
+
+  const className = ["meal-cell", isToday ? "today" : "", isOver ? "meal-cell--drop-over" : ""]
+    .filter(Boolean)
+    .join(" ");
 
   return (
-    <td className={isToday ? "meal-cell today" : "meal-cell"}>
+    <td ref={setNodeRef} className={className}>
       <div className="meal-cell__content">
         {items.length > 0 && (
           <div className="meal-cell__recipes">
             {items.map((item) => (
-              <span key={item.id} className="recipe-chip">
+              <span
+                key={item.id}
+                className={
+                  item.sourceItem !== null ? "recipe-chip recipe-chip--leftover" : "recipe-chip"
+                }
+              >
                 <span className="recipe-chip__name">
+                  {item.sourceItem !== null && (
+                    <span
+                      className="recipe-chip__leftover-badge"
+                      title={t("planning.leftovers.chipBadge")}
+                    >
+                      ♻️
+                    </span>
+                  )}
                   {item.recipe.name} · ×{item.portions}
                 </span>
                 <button

apps/web/src/pages/planning/planning-page.scss

@@ -161,6 +161,14 @@ table.planning-grid {
 // --- Case : pastilles de recette + bouton "+" -------------------------------
 .meal-cell {
   padding: var(--space-sm);
+
+  // Highlighted while a leftover card is dragged over it (@dnd-kit's
+  // `isOver`) — see PlanningPage's `MealCell` droppable.
+  &--drop-over {
+    background: var(--color-tag);
+    outline: 2px dashed var(--color-primary);
+    outline-offset: -2px;
+  }
 }
 
 .meal-cell__content {
@@ -197,6 +205,17 @@ table.planning-grid {
     white-space: nowrap;
   }
 
+  // A "leftovers" chip (`sourceItem !== null`) — served from another
+  // slot's batch, nothing cooked for it. Dimmer + a ♻️ marker.
+  &--leftover {
+    background: var(--color-surface-alt);
+    color: var(--color-text-muted);
+  }
+
+  &__leftover-badge {
+    margin-right: 0.15rem;
+  }
+
   &__remove {
     flex-shrink: 0;
     width: 1rem;

pnpm-lock.yaml

@@ -102,6 +102,12 @@ importers:
       '@batch-cooking/shared':
         specifier: workspace:*
         version: link:../../packages/shared
+      '@dnd-kit/core':
+        specifier: ^6.3.1
+        version: 6.3.1(react-dom@18.3.1(react@18.3.1))(react@18.3.1)
+      '@dnd-kit/utilities':
+        specifier: ^3.2.2
+        version: 3.2.2(react@18.3.1)
       i18next:
         specifier: ^26.3.6
         version: 26.3.6(typescript@5.9.3)
@@ -520,6 +526,22 @@ packages:
     resolution: {integrity: sha512-Xc3VhU02wqZ1HvHRJUwL09HkZSTvidqY5Ya0NXBSYOxAp+Ln9dcJr9fySI+CkONzP3PekQo9WdzCv0PGER/mOA==, tarball: https://registry.npmjs.org/@discoveryjs/json-ext/-/json-ext-1.1.0.tgz}
     engines: {node: '>=14.17.0'}
 
+  '@dnd-kit/accessibility@3.1.1':
+    resolution: {integrity: sha512-2P+YgaXF+gRsIihwwY1gCsQSYnu9Zyj2py8kY5fFvUM1qm2WA2u639R6YNVfU4GWr+ZM5mqEsfHZZLoRONbemw==, tarball: https://registry.npmjs.org/@dnd-kit/accessibility/-/accessibility-3.1.1.tgz}
+    peerDependencies:
+      react: '>=16.8.0'
+
+  '@dnd-kit/core@6.3.1':
+    resolution: {integrity: sha512-xkGBRQQab4RLwgXxoqETICr6S5JlogafbhNsidmrkVv2YRs5MLwpjoF2qpiGjQt8S9AoxtIV603s0GIUpY5eYQ==, tarball: https://registry.npmjs.org/@dnd-kit/core/-/core-6.3.1.tgz}
+    peerDependencies:
+      react: '>=16.8.0'
+      react-dom: '>=16.8.0'
+
+  '@dnd-kit/utilities@3.2.2':
+    resolution: {integrity: sha512-+MKAJEOfaBe5SmV6t34p80MMKhjvUz0vRrvVJbPT0WElzaOJ/1xs+D+KDv+tD/NE5ujfrChEcshd4fLn0wpiqg==, tarball: https://registry.npmjs.org/@dnd-kit/utilities/-/utilities-3.2.2.tgz}
+    peerDependencies:
+      react: '>=16.8.0'
+
   '@epic-web/invariant@1.0.0':
     resolution: {integrity: sha512-lrTPqgvfFQtR/eY/qkIzp98OGdNJu0m5ji3q/nJI8v3SXkRKEnWiOxMmbvcSoAIzv/cGiuvRy57k4suKQSAdwA==, tarball: https://registry.npmjs.org/@epic-web/invariant/-/invariant-1.0.0.tgz}
 
@@ -4384,6 +4406,24 @@ snapshots:
 
   '@discoveryjs/json-ext@1.1.0': {}
 
+  '@dnd-kit/accessibility@3.1.1(react@18.3.1)':
+    dependencies:
+      react: 18.3.1
+      tslib: 2.8.1
+
+  '@dnd-kit/core@6.3.1(react-dom@18.3.1(react@18.3.1))(react@18.3.1)':
+    dependencies:
+      '@dnd-kit/accessibility': 3.1.1(react@18.3.1)
+      '@dnd-kit/utilities': 3.2.2(react@18.3.1)
+      react: 18.3.1
+      react-dom: 18.3.1(react@18.3.1)
+      tslib: 2.8.1
+
+  '@dnd-kit/utilities@3.2.2(react@18.3.1)':
+    dependencies:
+      react: 18.3.1
+      tslib: 2.8.1
+
   '@epic-web/invariant@1.0.0': {}
 
   '@esbuild/aix-ppc64@0.21.5':

specs/frontend-architecture.md

@@ -38,7 +38,8 @@ apps/web/src/
 │   ├── planning/
 │   │   ├── RecipePickerDialog.tsx  # dialogue "ajouter au planning" — parcourir/prévisualiser/importer, voir plus bas
 │   │   ├── recipe-picker-dialog.scss
-│   │   ├── LeftoversBasket.tsx + leftovers-basket.ts + leftovers-basket.scss  # icône + popover des restes de la semaine dans l'en-tête du planning (issue #34)
+│   │   ├── LeftoversBasket.tsx + leftovers-basket.ts + leftovers-basket.scss  # icône + popover des restes de la semaine, cartes draggables (issue #34)
+│   │   ├── LeftoverAssignDialog.tsx  # étape "combien de portions ?" au dépôt d'un reste sur un créneau
 │   │   └── WeekNavigator.tsx + week-navigator.scss  # arrows + calendrier de sélection de semaine — partagé par PlanningPage et ShoppingListPage, voir plus bas
 │   └── recipes/               # catalogue, import, édition — voir plus bas ; sous-dossiers par sous-domaine, pas de fichiers à plat
 │       ├── RecipeTable.tsx / RecipeTabs.tsx / RecipeDetailPanel.tsx   # racine : composants transverses au sous-domaine (utilisés par plusieurs des sous-dossiers ci-dessous)
@@ -401,9 +402,18 @@ une bordure appuyée après `collation`/`dejeuner`/`gouter`.
   `computeAvailableLeftover` (`@batch-cooking/shared`, `leftoverUses`
   reconstitué depuis le tableau plat) est `> 0`. Bouton « Jeter » par
   ligne → `PATCH /planning/items/:id/discard-leftover`, la réponse est
-  patchée dans `planning.items` par id. Le glisser-déposer d'un reste sur
+  patchée dans `planning.items` par id.
-  un autre créneau arrive dans une itération ultérieure. Libellés :
+- **Glisser-déposer** (`@dnd-kit/core`, 1re et seule utilisation de DnD de
-  `planning.leftovers.*`.
+  l'app) — `PlanningPage` monte un `<DndContext>` (`PointerSensor` avec
+  distance d'activation 5px pour ne pas voler le clic « Jeter », +
+  `KeyboardSensor`) autour de la grille et du panier. Chaque ligne du
+  panier est `useDraggable` (poignée `⠿` dédiée), chaque `MealCell` est
+  `useDroppable` (`data: { date, weekDay, meal }`, surbrillance `isOver`).
+  Au drop, `onDragEnd` ouvre `LeftoverAssignDialog` (quantité, défaut =
+  disponible, plafonné) → `POST /planning/items/leftover` (`apiClient.
+  assignLeftover`) → nouvel item patché dans `planning.items`. Un item
+  « restes » (`sourceItem !== null`) porte un badge ♻️ sur sa pastille
+  (`.recipe-chip--leftover`). Libellés : `planning.leftovers.*`.
 
 ### `RecipePickerDialog` — parcourir, prévisualiser, importer