Merge pull request 'feat(balance): chart vehicle/class toggle + collapsible returns' (#208) from issue-204-chart-vehicle-toggle-collapsible-returns into main

Issue 3 of overnight-2026-06-01-bilan-axe-vehicule. Builds the tracking UI
on top of the merged data layer (#202) and input UI (#203).

- Service: getSnapshotTotalsByVehicleAndDate(range) mirrors the by-category
  aggregation with GROUP BY COALESCE(a.vehicle_type, 'none') so null-envelope
  accounts land in a single 'none' bucket (never a SQL NULL key). Add
  vehicle_type to getAccountsLatestSnapshot SELECT + type.
- useBalanceOverview: new groupAxis ('class'|'vehicle') state ORTHOGONAL to
  chartMode; loads byVehicle alongside byCategory. Default groupAxis='class'.
- BalanceEvolutionChart + BalancePage: stacked-mode sub-toggle 'Par classe
  d'actif' (default) / 'Par enveloppe'. Vehicle legend reuses the #203
  vehicleType.* labels; the 'none' bucket uses balance.vehicle.none.
- BalanceAccountsTable: 4 return columns collapsed by default with a toggle,
  persisted across sessions via userPreferenceService key balance_show_returns.
- i18n FR/EN: balance.chart.axis.{byAssetClass,byVehicle}, balance.vehicle.none,
  balance.accountsTable.toggleReturns.{show,hide} (+ axisLegend aria label).

Tests: npm run build green (0 type errors); vitest 3314 passed. Added 5
service tests for the 'none' bucket + mixed envelopes + date range.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/balance/BalanceAccountsTable.tsx

@@ -20,15 +20,33 @@
 
 import { useEffect, useMemo, useState } from "react";
 import { useTranslation } from "react-i18next";
-import { Archive, MoreVertical, Link as LinkIcon, AlertTriangle } from "lucide-react";
+import {
+  Archive,
+  MoreVertical,
+  Link as LinkIcon,
+  AlertTriangle,
+  ChevronDown,
+  ChevronRight,
+} from "lucide-react";
 import type {
   AccountLatestSnapshot,
   AccountPeriodAnchor,
 } from "../../services/balance.service";
 import { computeAccountReturn } from "../../services/balance.service";
+import {
+  getPreference,
+  setPreference,
+} from "../../services/userPreferenceService";
 import type { AccountReturn } from "../../shared/types";
 import { renderCategoryLabelFromAccount } from "../../utils/renderCategoryLabel";
 
+/**
+ * Preference key persisting whether the 4 Modified-Dietz return columns are
+ * expanded. Absent/anything-but-"1" → collapsed (the spec default). Stored via
+ * `userPreferenceService` so the choice survives across sessions (Issue #204).
+ */
+const SHOW_RETURNS_PREF_KEY = "balance_show_returns";
+
 const cadFormatter = (locale: string) =>
   new Intl.NumberFormat(locale, {
     style: "currency",
@@ -98,8 +116,40 @@ export default function BalanceAccountsTable({
 
   const [openMenuFor, setOpenMenuFor] = useState<number | null>(null);
 
+  // Progressive disclosure of the 4 return columns (Issue #204). Collapsed by
+  // default; the persisted choice is read once on mount. We start `false` so
+  // the columns never flash open before the preference resolves.
+  const [showReturns, setShowReturns] = useState(false);
+  useEffect(() => {
+    let cancelled = false;
+    void (async () => {
+      try {
+        const stored = await getPreference(SHOW_RETURNS_PREF_KEY);
+        if (!cancelled && stored === "1") setShowReturns(true);
+      } catch {
+        // Pref read failure: keep the collapsed default.
+      }
+    })();
+    return () => {
+      cancelled = true;
+    };
+  }, []);
+
+  const toggleReturns = () => {
+    setShowReturns((prev) => {
+      const next = !prev;
+      // Best-effort persist; a write failure just means the next session
+      // falls back to the collapsed default.
+      void setPreference(SHOW_RETURNS_PREF_KEY, next ? "1" : "0").catch(
+        () => {}
+      );
+      return next;
+    });
+  };
+
   // Returns cache. Cleared whenever the account list changes (new accounts,
-  // archive, etc.). Loaded lazily after mount.
+  // archive, etc.). Loaded lazily after mount — only while the columns are
+  // shown, so a collapsed table never runs the Modified-Dietz computation.
   const [returns, setReturns] = useState<ReturnsByAccount>({});
   const [returnsLoading, setReturnsLoading] = useState(false);
 
@@ -120,7 +170,7 @@ export default function BalanceAccountsTable({
   useEffect(() => {
     let cancelled = false;
     async function loadReturns() {
-      if (accounts.length === 0) {
+      if (!showReturns || accounts.length === 0) {
         setReturns({});
         return;
       }
@@ -155,7 +205,7 @@ export default function BalanceAccountsTable({
     return () => {
       cancelled = true;
     };
-  }, [accounts, horizons]);
+  }, [accounts, horizons, showReturns]);
 
   if (accounts.length === 0) {
     return (
@@ -231,6 +281,26 @@ export default function BalanceAccountsTable({
   }
 
   return (
+    <div className="space-y-2">
+      <div className="flex justify-end">
+        <button
+          type="button"
+          onClick={toggleReturns}
+          aria-expanded={showReturns}
+          className="inline-flex items-center gap-1.5 px-3 py-1.5 text-sm font-medium rounded-lg border border-[var(--border)] bg-[var(--card)] text-[var(--foreground)] hover:bg-[var(--muted)]/40"
+        >
+          {showReturns ? (
+            <ChevronDown size={14} />
+          ) : (
+            <ChevronRight size={14} />
+          )}
+          {t(
+            showReturns
+              ? "balance.accountsTable.toggleReturns.hide"
+              : "balance.accountsTable.toggleReturns.show"
+          )}
+        </button>
+      </div>
       <div className="bg-[var(--card)] border border-[var(--border)] rounded-xl overflow-x-auto">
         <table className="w-full text-sm">
           <thead className="bg-[var(--muted)]/30">
@@ -247,6 +317,8 @@ export default function BalanceAccountsTable({
             <th className="text-right px-4 py-3 font-medium">
               {t("balance.overview.periodDelta")}
             </th>
+            {showReturns && (
+              <>
                 <th className="text-right px-4 py-3 font-medium" title={t("balance.accountsTable.return3mTooltip")}>
                   {t("balance.accountsTable.return3m")}
                 </th>
@@ -259,6 +331,8 @@ export default function BalanceAccountsTable({
                 <th className="text-right px-4 py-3 font-medium" title={t("balance.accountsTable.unadjustedTooltip")}>
                   {t("balance.accountsTable.unadjusted")}
                 </th>
+              </>
+            )}
             <th className="text-right px-4 py-3 font-medium w-12">
               {t("balance.account.fields.actions")}
             </th>
@@ -309,6 +383,8 @@ export default function BalanceAccountsTable({
                     "—"
                   )}
                 </td>
+                {showReturns && (
+                  <>
                     <td className="px-4 py-3 text-right tabular-nums">
                       {returnsLoading && !accReturns["3M"]
                         ? "…"
@@ -329,6 +405,8 @@ export default function BalanceAccountsTable({
                         ? "…"
                         : renderUnadjustedCell(accReturns["1A"])}
                     </td>
+                  </>
+                )}
                 <td className="px-4 py-3 text-right relative">
                   <button
                     type="button"
@@ -385,5 +463,6 @@ export default function BalanceAccountsTable({
         </tbody>
         </table>
       </div>
+    </div>
   );
 }

src/components/balance/BalanceEvolutionChart.tsx

@@ -27,8 +27,12 @@ import {
 import type {
   SnapshotTotalPoint,
   SnapshotCategoryBreakdownPoint,
+  SnapshotVehicleBreakdownPoint,
 } from "../../services/balance.service";
-import type { BalanceChartMode } from "../../hooks/useBalanceOverview";
+import type {
+  BalanceChartMode,
+  BalanceGroupAxis,
+} from "../../hooks/useBalanceOverview";
 import type { BalanceAccountTransferWithTransaction } from "../../shared/types";
 
 // Stable palette for the stacked-by-category areas. Indexed deterministically
@@ -49,10 +53,20 @@ const CATEGORY_PALETTE = [
 
 export interface BalanceEvolutionChartProps {
   mode: BalanceChartMode;
+  /**
+   * Stacked-mode grouping axis (Issue #204). `'class'` stacks by asset class
+   * (the `byCategory` series), `'vehicle'` stacks by fiscal envelope (the
+   * `byVehicle` series). Ignored in line mode. Defaults to `'class'`.
+   */
+  groupAxis?: BalanceGroupAxis;
   totals: SnapshotTotalPoint[];
   byCategory: SnapshotCategoryBreakdownPoint[];
+  /** Per-vehicle breakdown for the `groupAxis === 'vehicle'` stacked variant. */
+  byVehicle?: SnapshotVehicleBreakdownPoint[];
   /** Map category_key → translated label so the legend reads naturally. */
   categoryLabels?: Record<string, string>;
+  /** Map vehicle_key (incl. 'none') → translated label for the vehicle axis. */
+  vehicleLabels?: Record<string, string>;
   /**
    * Issue #142 — every linked transfer in the visible range. Rendered as
    * vertical `<ReferenceLine>` markers on the X axis: green for `in`
@@ -64,13 +78,37 @@ export interface BalanceEvolutionChartProps {
 
 export default function BalanceEvolutionChart({
   mode,
+  groupAxis = "class",
   totals,
   byCategory,
+  byVehicle = [],
   categoryLabels = {},
+  vehicleLabels = {},
   transferMarkers = [],
 }: BalanceEvolutionChartProps) {
   const { t, i18n } = useTranslation();
 
+  // The stacked chart is driven by whichever axis is active. Both breakdowns
+  // share the `{ snapshot_date, <map> }` shape, so we normalize to a common
+  // `{ snapshot_date, series }` form here and feed a single rendering path.
+  const stackedSource = useMemo(
+    () =>
+      groupAxis === "vehicle"
+        ? byVehicle.map((p) => ({
+            snapshot_date: p.snapshot_date,
+            series: p.byVehicle,
+          }))
+        : byCategory.map((p) => ({
+            snapshot_date: p.snapshot_date,
+            series: p.byCategory,
+          })),
+    [groupAxis, byCategory, byVehicle]
+  );
+
+  // Label map for the active axis (legend + tooltip). Falls back to the raw
+  // key when no translation is provided.
+  const activeLabels = groupAxis === "vehicle" ? vehicleLabels : categoryLabels;
+
   const cadFormatter = useMemo(
     () =>
       new Intl.NumberFormat(i18n.language === "fr" ? "fr-CA" : "en-CA", {
@@ -101,25 +139,26 @@ export default function BalanceEvolutionChart({
 
   // --- Stacked-area dataset ---
   // We transpose the per-snapshot bucket into one row per snapshot_date with
-  // one column per category_key. Categories absent at a snapshot date are
-  // emitted as 0 so Recharts renders a continuous stack.
+  // one column per series key (asset class OR fiscal envelope, per groupAxis).
+  // Keys absent at a snapshot date are emitted as 0 so Recharts renders a
+  // continuous stack.
   const { stackedData, categoryKeys } = useMemo(() => {
     const keys = new Set<string>();
-    for (const point of byCategory) {
-      for (const k of Object.keys(point.byCategory)) keys.add(k);
+    for (const point of stackedSource) {
+      for (const k of Object.keys(point.series)) keys.add(k);
     }
     const orderedKeys = Array.from(keys).sort();
-    const data = byCategory.map((point) => {
+    const data = stackedSource.map((point) => {
       const row: Record<string, string | number> = {
         snapshot_date: point.snapshot_date,
       };
       for (const k of orderedKeys) {
-        row[k] = point.byCategory[k] ?? 0;
+        row[k] = point.series[k] ?? 0;
       }
       return row;
     });
     return { stackedData: data, categoryKeys: orderedKeys };
-  }, [byCategory]);
+  }, [stackedSource]);
 
   const isEmpty =
     mode === "line" ? lineData.length === 0 : stackedData.length === 0;
@@ -247,13 +286,13 @@ export default function BalanceEvolutionChart({
             <Tooltip
               formatter={(value: number | undefined, name) => [
                 cadFormatter.format(value ?? 0),
-                categoryLabels[String(name)] ?? String(name),
+                activeLabels[String(name)] ?? String(name),
               ]}
               labelFormatter={(label) => formatDate(String(label))}
               contentStyle={tooltipContentStyle}
             />
             <Legend
-              formatter={(value) => categoryLabels[String(value)] ?? String(value)}
+              formatter={(value) => activeLabels[String(value)] ?? String(value)}
             />
             {categoryKeys.map((key, idx) => (
               <Area

src/hooks/useBalanceOverview.ts

@@ -1,23 +1,29 @@
 // useBalanceOverview — scoped useReducer hook backing BalancePage.
 //
-// Domain coverage (per spec-plan-bilan.md v2 / Issue #141):
-//   - Time-series for the evolution chart (totals + per-category breakdown)
+// Domain coverage (per spec-plan-bilan.md v2 / Issue #141, extended in #204):
+//   - Time-series for the evolution chart (totals + per-category + per-vehicle)
 //   - Per-account latest snapshot value + period-anchor value (for Δ%)
 //   - Period selector (3M / 6M / 1A / 3A / Tout)
 //   - Chart mode toggle (line / stacked-area)
+//   - Group-axis toggle for the stacked mode (asset class / fiscal envelope)
 //
-// Returns are intentionally OUT of scope here — they ship in Issue #142
-// (Modified Dietz). The accounts table reserves columns for the return
-// metrics with TODO comments.
+// `chartMode` (line/stacked) and `groupAxis` (class/vehicle) are two ORTHOGONAL
+// dimensions: `groupAxis` only changes which breakdown feeds the stacked chart;
+// it has no effect in line mode. They are kept as independent state to avoid
+// conflating "how to draw" with "what to group by" (Issue #204).
+//
+// Returns (Modified Dietz) are loaded by the accounts table itself, not here.
 
 import { useReducer, useEffect, useCallback } from "react";
 import {
   getSnapshotTotalsByDate,
   getSnapshotTotalsByCategoryAndDate,
+  getSnapshotTotalsByVehicleAndDate,
   getAccountsLatestSnapshot,
   getAccountsPeriodAnchor,
   type SnapshotTotalPoint,
   type SnapshotCategoryBreakdownPoint,
+  type SnapshotVehicleBreakdownPoint,
   type AccountLatestSnapshot,
   type AccountPeriodAnchor,
   type SnapshotDateRange,
@@ -25,12 +31,17 @@ import {
 
 export type BalancePeriod = "3M" | "6M" | "1A" | "3A" | "all";
 export type BalanceChartMode = "line" | "stacked";
+/** Stacked-chart grouping axis: by asset class (category) or fiscal envelope. */
+export type BalanceGroupAxis = "class" | "vehicle";
 
 interface State {
   period: BalancePeriod;
   chartMode: BalanceChartMode;
+  /** Orthogonal to `chartMode`; only meaningful in stacked mode. Default 'class'. */
+  groupAxis: BalanceGroupAxis;
   evolutionTotals: SnapshotTotalPoint[];
   evolutionByCategory: SnapshotCategoryBreakdownPoint[];
+  evolutionByVehicle: SnapshotVehicleBreakdownPoint[];
   accountsLatest: AccountLatestSnapshot[];
   accountsPeriodAnchor: AccountPeriodAnchor[];
   isLoading: boolean;
@@ -40,12 +51,14 @@ interface State {
 type Action =
   | { type: "SET_PERIOD"; payload: BalancePeriod }
   | { type: "SET_CHART_MODE"; payload: BalanceChartMode }
+  | { type: "SET_GROUP_AXIS"; payload: BalanceGroupAxis }
   | { type: "LOAD_START" }
   | {
       type: "LOAD_SUCCESS";
       payload: {
         evolutionTotals: SnapshotTotalPoint[];
         evolutionByCategory: SnapshotCategoryBreakdownPoint[];
+        evolutionByVehicle: SnapshotVehicleBreakdownPoint[];
         accountsLatest: AccountLatestSnapshot[];
         accountsPeriodAnchor: AccountPeriodAnchor[];
       };
@@ -56,8 +69,10 @@ function initialState(): State {
   return {
     period: "1A",
     chartMode: "line",
+    groupAxis: "class",
     evolutionTotals: [],
     evolutionByCategory: [],
+    evolutionByVehicle: [],
     accountsLatest: [],
     accountsPeriodAnchor: [],
     isLoading: false,
@@ -71,6 +86,8 @@ function reducer(state: State, action: Action): State {
       return { ...state, period: action.payload };
     case "SET_CHART_MODE":
       return { ...state, chartMode: action.payload };
+    case "SET_GROUP_AXIS":
+      return { ...state, groupAxis: action.payload };
     case "LOAD_START":
       return { ...state, isLoading: true, error: null };
     case "LOAD_SUCCESS":
@@ -117,6 +134,7 @@ export interface UseBalanceOverviewResult {
   state: State;
   setPeriod: (period: BalancePeriod) => void;
   setChartMode: (mode: BalanceChartMode) => void;
+  setGroupAxis: (axis: BalanceGroupAxis) => void;
   reload: () => Promise<void>;
 }
 
@@ -127,10 +145,12 @@ export function useBalanceOverview(): UseBalanceOverviewResult {
     dispatch({ type: "LOAD_START" });
     try {
       const range = computeBalanceDateRange(period);
-      // Parallel fetches — no inter-dependency between the four queries.
-      const [totals, byCategory, latest, anchors] = await Promise.all([
+      // Parallel fetches — no inter-dependency between the queries.
+      const [totals, byCategory, byVehicle, latest, anchors] =
+        await Promise.all([
           getSnapshotTotalsByDate(range),
           getSnapshotTotalsByCategoryAndDate(range),
+          getSnapshotTotalsByVehicleAndDate(range),
           getAccountsLatestSnapshot(),
           getAccountsPeriodAnchor(range),
         ]);
@@ -139,6 +159,7 @@ export function useBalanceOverview(): UseBalanceOverviewResult {
         payload: {
           evolutionTotals: totals,
           evolutionByCategory: byCategory,
+          evolutionByVehicle: byVehicle,
           accountsLatest: latest,
           accountsPeriodAnchor: anchors,
         },
@@ -162,7 +183,11 @@ export function useBalanceOverview(): UseBalanceOverviewResult {
     dispatch({ type: "SET_CHART_MODE", payload: mode });
   }, []);
 
+  const setGroupAxis = useCallback((axis: BalanceGroupAxis) => {
+    dispatch({ type: "SET_GROUP_AXIS", payload: axis });
+  }, []);
+
   const reload = useCallback(() => load(state.period), [load, state.period]);
 
-  return { state, setPeriod, setChartMode, reload };
+  return { state, setPeriod, setChartMode, setGroupAxis, reload };
 }

src/i18n/locales/en.json

@@ -1563,10 +1563,15 @@
     "chart": {
       "empty": "No snapshot for this period.",
       "modeLegend": "Chart display mode",
+      "axisLegend": "Stacked chart grouping axis",
       "totalSeriesLabel": "Total",
       "mode": {
         "line": "Line",
         "stacked": "Stacked by type"
+      },
+      "axis": {
+        "byAssetClass": "By asset class",
+        "byVehicle": "By envelope"
       }
     },
     "onboarding": {
@@ -1788,7 +1793,14 @@
       "sinceCreation": "Since inception",
       "sinceCreationTooltip": "Modified Dietz return since the first snapshot.",
       "unadjusted": "Unadjusted",
-      "unadjustedTooltip": "Simple return (V_end − V_start) / V_start, with no contribution weighting."
+      "unadjustedTooltip": "Simple return (V_end − V_start) / V_start, with no contribution weighting.",
+      "toggleReturns": {
+        "show": "Show returns",
+        "hide": "Hide returns"
+      }
+    },
+    "vehicle": {
+      "none": "No envelope"
     },
     "transfers": {
       "linkAction": "Link transfers",

src/i18n/locales/fr.json

@@ -1563,10 +1563,15 @@
     "chart": {
       "empty": "Aucun snapshot pour cette période.",
       "modeLegend": "Mode d'affichage du graphique",
+      "axisLegend": "Axe de regroupement du graphique empilé",
       "totalSeriesLabel": "Total",
       "mode": {
         "line": "Ligne",
         "stacked": "Empilé par type"
+      },
+      "axis": {
+        "byAssetClass": "Par classe d'actif",
+        "byVehicle": "Par enveloppe"
       }
     },
     "onboarding": {
@@ -1788,7 +1793,14 @@
       "sinceCreation": "Depuis création",
       "sinceCreationTooltip": "Rendement Modified Dietz depuis le premier snapshot.",
       "unadjusted": "Non ajusté",
-      "unadjustedTooltip": "Rendement simple (V_fin − V_début) / V_début, sans pondération des apports."
+      "unadjustedTooltip": "Rendement simple (V_fin − V_début) / V_début, sans pondération des apports.",
+      "toggleReturns": {
+        "show": "Afficher les rendements",
+        "hide": "Masquer les rendements"
+      }
+    },
+    "vehicle": {
+      "none": "Sans enveloppe"
     },
     "transfers": {
       "linkAction": "Lier transferts",

src/pages/BalancePage.tsx

@@ -18,7 +18,10 @@ import {
   useBalanceOverview,
   type BalancePeriod,
   type BalanceChartMode,
+  type BalanceGroupAxis,
 } from "../hooks/useBalanceOverview";
+import { BALANCE_VEHICLE_TYPES } from "../shared/types";
+import { VEHICLE_NONE_BUCKET } from "../services/balance.service";
 import {
   archiveBalanceAccount,
   listAccountTransfers,
@@ -41,7 +44,8 @@ const PERIOD_OPTIONS: BalancePeriod[] = ["3M", "6M", "1A", "3A", "all"];
 
 export default function BalancePage() {
   const { t } = useTranslation();
-  const { state, setPeriod, setChartMode, reload } = useBalanceOverview();
+  const { state, setPeriod, setChartMode, setGroupAxis, reload } =
+    useBalanceOverview();
 
   // Issue #142 — link-transfers modal state. Categories list is loaded once
   // on mount (used by the modal's filter dropdown).
@@ -150,6 +154,20 @@ export default function BalancePage() {
     return m;
   }, [state.accountsLatest, t]);
 
+  // Map vehicle_key → translated label for the "par enveloppe" stacked axis.
+  // Reuses the #203 account-form labels (`balance.account.form.vehicleType.*`)
+  // so the legend never duplicates strings; the NULL-envelope bucket uses the
+  // dedicated `balance.vehicle.none` key.
+  const vehicleLabels = useMemo(() => {
+    const m: Record<string, string> = {
+      [VEHICLE_NONE_BUCKET]: t("balance.vehicle.none"),
+    };
+    for (const v of BALANCE_VEHICLE_TYPES) {
+      m[v] = t(`balance.account.form.vehicleType.${v}`);
+    }
+    return m;
+  }, [t]);
+
   const handleArchiveAccount = async (accountId: number) => {
     try {
       await archiveBalanceAccount(accountId);
@@ -223,6 +241,37 @@ export default function BalancePage() {
                 ))}
               </div>
 
+              <div className="flex flex-wrap items-center gap-3">
+                {/* Stacked-mode group-axis sub-toggle (asset class / envelope).
+                    Only meaningful while the stacked mode is active. */}
+                {state.chartMode === "stacked" && (
+                  <div
+                    role="group"
+                    aria-label={t("balance.chart.axisLegend")}
+                    className="inline-flex rounded-lg border border-[var(--border)] overflow-hidden"
+                  >
+                    {(["class", "vehicle"] as BalanceGroupAxis[]).map((axis) => (
+                      <button
+                        key={axis}
+                        type="button"
+                        onClick={() => setGroupAxis(axis)}
+                        className={`px-3 py-1.5 text-sm font-medium ${
+                          state.groupAxis === axis
+                            ? "bg-[var(--primary)] text-white"
+                            : "bg-[var(--card)] text-[var(--foreground)] hover:bg-[var(--muted)]/40"
+                        }`}
+                        aria-pressed={state.groupAxis === axis}
+                      >
+                        {t(
+                          axis === "class"
+                            ? "balance.chart.axis.byAssetClass"
+                            : "balance.chart.axis.byVehicle"
+                        )}
+                      </button>
+                    ))}
+                  </div>
+                )}
+
                 {/* Chart mode toggle */}
                 <div
                   role="group"
@@ -246,12 +295,16 @@ export default function BalancePage() {
                   ))}
                 </div>
               </div>
+            </div>
 
             <BalanceEvolutionChart
               mode={state.chartMode}
+              groupAxis={state.groupAxis}
               totals={state.evolutionTotals}
               byCategory={state.evolutionByCategory}
+              byVehicle={state.evolutionByVehicle}
               categoryLabels={categoryLabels}
+              vehicleLabels={vehicleLabels}
               transferMarkers={allTransferMarkers}
             />
 

src/services/balance.service.test.ts

@@ -40,6 +40,7 @@ import {
   BalanceServiceError,
   getSnapshotTotalsByDate,
   getSnapshotTotalsByCategoryAndDate,
+  getSnapshotTotalsByVehicleAndDate,
   getAccountsLatestSnapshot,
   getAccountsPeriodAnchor,
   computeAccountReturn,
@@ -693,6 +694,13 @@ describe("balance accounts — vehicle_type (#202)", () => {
     const sql = mockSelect.mock.calls[0][0] as string;
     expect(sql).toContain("c.custom_label AS category_custom_label");
   });
+
+  it("getAccountsLatestSnapshot threads vehicle_type (#204)", async () => {
+    mockSelect.mockResolvedValueOnce([]);
+    await getAccountsLatestSnapshot();
+    const sql = mockSelect.mock.calls[0][0] as string;
+    expect(sql).toContain("a.vehicle_type AS vehicle_type");
+  });
 });
 
 describe("updateBalanceAccount", () => {
@@ -1561,6 +1569,66 @@ describe("getSnapshotTotalsByCategoryAndDate", () => {
   });
 });
 
+describe("getSnapshotTotalsByVehicleAndDate (#204)", () => {
+  it("returns [] on empty DB", async () => {
+    mockSelect.mockResolvedValueOnce([]);
+    expect(await getSnapshotTotalsByVehicleAndDate()).toEqual([]);
+  });
+
+  it("COALESCEs NULL envelopes into a single 'none' bucket", async () => {
+    mockSelect.mockResolvedValueOnce([]);
+    await getSnapshotTotalsByVehicleAndDate();
+    const sql = mockSelect.mock.calls[0][0] as string;
+    // HIGH caveat: the GROUP BY must coalesce NULL → 'none' so null-envelope
+    // accounts never produce a SQL NULL key.
+    expect(sql).toContain("COALESCE(a.vehicle_type, 'none')");
+    expect(sql).toContain("GROUP BY s.snapshot_date, COALESCE(a.vehicle_type, 'none')");
+    expect(sql).toContain("INNER JOIN balance_accounts");
+  });
+
+  it("buckets a mix of envelopes plus the 'none' bucket per snapshot_date", async () => {
+    mockSelect.mockResolvedValueOnce([
+      { snapshot_date: "2026-01-31", vehicle_key: "none", total: 500 },
+      { snapshot_date: "2026-01-31", vehicle_key: "tfsa", total: 1500 },
+      { snapshot_date: "2026-01-31", vehicle_key: "rrsp", total: 3000 },
+      { snapshot_date: "2026-02-28", vehicle_key: "none", total: 700 },
+      { snapshot_date: "2026-02-28", vehicle_key: "tfsa", total: 1700 },
+    ]);
+    const out = await getSnapshotTotalsByVehicleAndDate();
+    expect(out).toEqual([
+      {
+        snapshot_date: "2026-01-31",
+        byVehicle: { none: 500, tfsa: 1500, rrsp: 3000 },
+      },
+      {
+        snapshot_date: "2026-02-28",
+        byVehicle: { none: 700, tfsa: 1700 },
+      },
+    ]);
+  });
+
+  it("handles a snapshot composed solely of null-envelope accounts", async () => {
+    mockSelect.mockResolvedValueOnce([
+      { snapshot_date: "2026-03-31", vehicle_key: "none", total: 4200 },
+    ]);
+    const out = await getSnapshotTotalsByVehicleAndDate();
+    expect(out).toEqual([
+      { snapshot_date: "2026-03-31", byVehicle: { none: 4200 } },
+    ]);
+  });
+
+  it("applies date range params when supplied", async () => {
+    mockSelect.mockResolvedValueOnce([]);
+    await getSnapshotTotalsByVehicleAndDate({
+      from: "2026-01-01",
+      to: "2026-12-31",
+    });
+    const sql = mockSelect.mock.calls[0][0] as string;
+    expect(sql).toContain("WHERE");
+    expect(mockSelect.mock.calls[0][1]).toEqual(["2026-01-01", "2026-12-31"]);
+  });
+});
+
 describe("getAccountsLatestSnapshot", () => {
   it("returns [] when there are no active accounts", async () => {
     mockSelect.mockResolvedValueOnce([]);

src/services/balance.service.ts

@@ -1326,6 +1326,65 @@ export async function getSnapshotTotalsByCategoryAndDate(
   return out;
 }
 
+/** Sentinel bucket key for accounts with no fiscal envelope (NULL vehicle_type). */
+export const VEHICLE_NONE_BUCKET = "none";
+
+/** Per-snapshot breakdown by fiscal envelope (`vehicle_type`). */
+export interface SnapshotVehicleBreakdownPoint {
+  snapshot_date: string;
+  /** Keyed by vehicle_type code, with the `'none'` bucket for NULL envelopes. */
+  byVehicle: Record<string, number>;
+}
+
+interface RawVehicleBreakdownRow {
+  snapshot_date: string;
+  vehicle_key: string;
+  total: number;
+}
+
+/**
+ * Returns per-snapshot totals broken down by `balance_accounts.vehicle_type`,
+ * sorted by date ASC. Mirror of `getSnapshotTotalsByCategoryAndDate` for the
+ * "par enveloppe" axis of the stacked-area chart (Issue #204 / Étape 1).
+ *
+ * ⚠️ `vehicle_type` is NULLABLE — accounts with no envelope are grouped under
+ * a single `'none'` bucket via `COALESCE(a.vehicle_type, 'none')`, never a SQL
+ * NULL key (which would collapse to a `null` object key on the JS side). The
+ * `'none'` bucket is labelled with `balance.vehicle.none` in the UI.
+ *
+ * Vehicles with no value at a given date are omitted from the `byVehicle` map
+ * (chart consumers treat absent keys as zero).
+ */
+export async function getSnapshotTotalsByVehicleAndDate(
+  range?: SnapshotDateRange
+): Promise<SnapshotVehicleBreakdownPoint[]> {
+  const { clause, params } = buildDateRangeClause(range, "s");
+  const db = await getDb();
+  const rows = await db.select<RawVehicleBreakdownRow[]>(
+    `SELECT s.snapshot_date AS snapshot_date,
+            COALESCE(a.vehicle_type, 'none') AS vehicle_key,
+            COALESCE(SUM(l.value), 0) AS total
+       FROM balance_snapshots s
+       INNER JOIN balance_snapshot_lines l ON l.snapshot_id = s.id
+       INNER JOIN balance_accounts a ON a.id = l.account_id
+       ${clause}
+       GROUP BY s.snapshot_date, COALESCE(a.vehicle_type, 'none')
+       ORDER BY s.snapshot_date ASC, vehicle_key ASC`,
+    params
+  );
+  // Bucket rows by snapshot_date — many rows per date, one per vehicle.
+  const out: SnapshotVehicleBreakdownPoint[] = [];
+  let current: SnapshotVehicleBreakdownPoint | null = null;
+  for (const r of rows) {
+    if (!current || current.snapshot_date !== r.snapshot_date) {
+      current = { snapshot_date: r.snapshot_date, byVehicle: {} };
+      out.push(current);
+    }
+    current.byVehicle[r.vehicle_key] = r.total;
+  }
+  return out;
+}
+
 /** Latest-snapshot value per active account (Issue #141). */
 export interface AccountLatestSnapshot {
   account_id: number;
@@ -1337,6 +1396,11 @@ export interface AccountLatestSnapshot {
   category_kind: BalanceCategoryKind;
   /** Mirror of `balance_categories.custom_label` — drives renderCategoryLabel. */
   category_custom_label?: string | null;
+  /**
+   * Fiscal envelope of the account (`vehicle_type`), or NULL when none.
+   * Surfaced for the "par enveloppe" axis groupings (Issue #204).
+   */
+  vehicle_type?: BalanceVehicleType | null;
   /** Date of the snapshot whose value is reported, or null if no snapshot exists. */
   latest_snapshot_date: string | null;
   /** Value at that snapshot, or null if the account has no snapshot lines. */
@@ -1366,6 +1430,7 @@ export async function getAccountsLatestSnapshot(): Promise<
             c.i18n_key AS category_i18n_key,
             c.kind AS category_kind,
             c.custom_label AS category_custom_label,
+            a.vehicle_type AS vehicle_type,
             (SELECT s.snapshot_date
                FROM balance_snapshot_lines l
                JOIN balance_snapshots s ON s.id = l.snapshot_id