diff --git a/src/__integration__/balance-flow.test.ts b/src/__integration__/balance-flow.test.ts
new file mode 100644
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--- /dev/null
+++ b/src/__integration__/balance-flow.test.ts
@@ -0,0 +1,574 @@
+/**
+ * Integration tests for the Bilan (balance sheet) feature — Issue #144.
+ *
+ * Cross-cutting tests that exercise the *whole* TS surface in one go:
+ *
+ *   account → priced category → priced snapshot → linked transfer → return
+ *
+ * Like `category-migration.test.ts` we cannot spin up real `tauri-plugin-sql`
+ * (the bridge only lives inside the Tauri WebView). Instead we drive every
+ * service against an in-memory FakeDb that:
+ *   - records every executed SQL,
+ *   - returns hand-tuned `select` results to mimic the real schema,
+ *   - simulates `lastInsertId` / `rowsAffected` for INSERT/DELETE.
+ *
+ * The Tauri `invoke` is mocked — `computeAccountReturn` lives on the Rust
+ * side (`compute_account_return`), so we assert the request payload and
+ * have the mock return a stable `AccountReturn` shape. The Rust math itself
+ * is covered by `return_calculator.rs`'s `#[cfg(test)] mod tests`.
+ *
+ * Scope (from spec-plan-bilan.md, Issue #144):
+ *   1. End-to-end happy path
+ *   2. Currency-lock (CHECK `currency = 'CAD'`) at the service level
+ *   3. Migration v9 on a seeded DB — covered in Rust (lib.rs `mod tests`)
+ *   4. TransactionsPage non-regression for the inlined transfer icon
+ *   5. Coverage best-effort (deferred — see decisions-log.md)
+ */
+
+import { describe, it, expect, vi, beforeEach } from "vitest";
+
+vi.mock("../services/db", () => ({
+  getDb: vi.fn(),
+}));
+
+vi.mock("@tauri-apps/api/core", () => ({
+  invoke: vi.fn(),
+}));
+
+vi.mock("../services/profileService", () => ({
+  loadProfiles: vi.fn(),
+}));
+
+import { getDb } from "../services/db";
+import { invoke } from "@tauri-apps/api/core";
+import { loadProfiles } from "../services/profileService";
+
+import {
+  createBalanceCategory,
+  createBalanceAccount,
+  listBalanceAccounts,
+  createSnapshot,
+  upsertSnapshotLines,
+  listLinesBySnapshot,
+  linkTransfer,
+  unlinkTransfer,
+  listAccountTransfers,
+  computeAccountReturn,
+  BalanceServiceError,
+  PRICED_VALUE_TOLERANCE,
+} from "../services/balance.service";
+
+// ---------------------------------------------------------------------------
+// FakeDb harness: scripted select results, recorded execute calls.
+// ---------------------------------------------------------------------------
+
+interface FakeDb {
+  calls: Array<{ sql: string; params?: unknown[] }>;
+  selectQueue: Array<unknown[]>;
+  executeQueue: Array<{ lastInsertId?: number; rowsAffected?: number }>;
+  select: ReturnType<typeof vi.fn>;
+  execute: ReturnType<typeof vi.fn>;
+}
+
+function makeFakeDb(): FakeDb {
+  const db: FakeDb = {
+    calls: [],
+    selectQueue: [],
+    executeQueue: [],
+    select: vi.fn(),
+    execute: vi.fn(),
+  };
+  db.select.mockImplementation(async (sql: string, params?: unknown[]) => {
+    db.calls.push({ sql, params });
+    if (db.selectQueue.length === 0) {
+      throw new Error(`Unscripted SELECT (no queued result): ${sql}`);
+    }
+    return db.selectQueue.shift();
+  });
+  db.execute.mockImplementation(async (sql: string, params?: unknown[]) => {
+    db.calls.push({ sql, params });
+    if (db.executeQueue.length === 0) {
+      // Default: 1 affected row, monotonically increasing lastInsertId
+      return { rowsAffected: 1, lastInsertId: db.calls.length };
+    }
+    return db.executeQueue.shift();
+  });
+  return db;
+}
+
+let fake: FakeDb;
+
+beforeEach(() => {
+  fake = makeFakeDb();
+  vi.mocked(getDb).mockResolvedValue(
+    { select: fake.select, execute: fake.execute } as never
+  );
+  vi.mocked(invoke).mockReset();
+  vi.mocked(loadProfiles).mockReset();
+});
+
+// Helper: queue a sequence of SELECT results in FIFO order.
+function queueSelects(...rows: unknown[][]) {
+  for (const r of rows) fake.selectQueue.push(r);
+}
+
+// Helper: queue a sequence of EXECUTE results in FIFO order.
+function queueExecutes(
+  ...results: Array<{ lastInsertId?: number; rowsAffected?: number }>
+) {
+  for (const r of results) fake.executeQueue.push(r);
+}
+
+// ---------------------------------------------------------------------------
+// 1. End-to-end happy path
+// ---------------------------------------------------------------------------
+//
+// Walks the full Bilan flow as if the user just installed the app:
+//   1. Create a custom priced category ("etf-prov")
+//   2. Create an account on that category with a stock symbol
+//   3. Reload the joined accounts list and confirm the account is there
+//   4. Create a snapshot dated today
+//   5. Save a priced line for the new account (qty * price = value)
+//   6. Read the lines back and confirm what was persisted
+//   7. Link a transaction to the account as a +CAD deposit
+//   8. Compute the account's return → mock returns a stable shape, we
+//      assert the wiring uses the active profile's db_filename and forwards
+//      every parameter as ISO YYYY-MM-DD.
+//
+// Each step is asserted at the service-call level (params + queued SQL),
+// then we run cross-step sanity checks.
+
+describe("integration — Bilan end-to-end happy path", () => {
+  it("walks account → priced category → snapshot → transfer → return cleanly", async () => {
+    // ---- 1. Create a custom priced category ----
+    queueExecutes({ lastInsertId: 100 });
+    const categoryId = await createBalanceCategory({
+      key: "etf-prov",
+      i18n_key: "balance.category.etf_prov",
+      kind: "priced",
+      sort_order: 80,
+    });
+    expect(categoryId).toBe(100);
+
+    // ---- 2. Create the account on that category ----
+    // Service first SELECTs the category to validate it exists, then
+    // INSERTs the account.
+    queueSelects([
+      {
+        id: 100,
+        key: "etf-prov",
+        i18n_key: "balance.category.etf_prov",
+        kind: "priced",
+        sort_order: 80,
+        is_active: 1,
+        is_seed: 0,
+      },
+    ]);
+    queueExecutes({ lastInsertId: 7 });
+    const accountId = await createBalanceAccount({
+      balance_category_id: categoryId,
+      name: "VFV (Wealthsimple)",
+      symbol: "VFV.TO",
+    });
+    expect(accountId).toBe(7);
+
+    // ---- 3. listBalanceAccounts: account joined with category ----
+    queueSelects([
+      {
+        id: 7,
+        balance_category_id: 100,
+        name: "VFV (Wealthsimple)",
+        symbol: "VFV.TO",
+        currency: "CAD",
+        notes: null,
+        is_active: 1,
+        archived_at: null,
+        created_at: "",
+        updated_at: "",
+        category_key: "etf-prov",
+        category_i18n_key: "balance.category.etf_prov",
+        category_kind: "priced",
+      },
+    ]);
+    const accounts = await listBalanceAccounts();
+    expect(accounts).toHaveLength(1);
+    expect(accounts[0].category_kind).toBe("priced");
+    expect(accounts[0].symbol).toBe("VFV.TO");
+
+    // ---- 4. Create a snapshot dated 2026-04-25 ----
+    // createSnapshot first SELECTs by date (must be empty) then INSERTs.
+    queueSelects([]); // no existing snapshot
+    queueExecutes({ lastInsertId: 50 });
+    const snapshotId = await createSnapshot({ snapshot_date: "2026-04-25" });
+    expect(snapshotId).toBe(50);
+
+    // ---- 5. Save a priced line: 10 shares × $200 = $2000 ----
+    // upsertSnapshotLines: SELECT snapshot, then DELETE existing lines, then
+    // one INSERT per line, then UPDATE updated_at.
+    queueSelects([
+      {
+        id: 50,
+        snapshot_date: "2026-04-25",
+        notes: null,
+        created_at: "",
+        updated_at: "",
+      },
+    ]);
+    queueExecutes(
+      { rowsAffected: 0 }, // delete (no prior lines)
+      { lastInsertId: 200 }, // insert priced line
+      { rowsAffected: 1 } // bump updated_at
+    );
+    await upsertSnapshotLines(50, [
+      {
+        account_id: 7,
+        account_kind: "priced",
+        quantity: 10,
+        unit_price: 200,
+        value: 2000,
+      },
+    ]);
+
+    // The 2nd execute call should be the INSERT with the priced placeholders.
+    const insertCall = fake.calls.find(
+      (c) =>
+        typeof c.sql === "string" &&
+        c.sql.includes("INSERT INTO balance_snapshot_lines")
+    );
+    expect(insertCall).toBeDefined();
+    expect(insertCall!.params).toEqual([50, 7, 10, 200, 2000]);
+
+    // ---- 6. Read the lines back ----
+    queueSelects([
+      {
+        id: 200,
+        snapshot_id: 50,
+        account_id: 7,
+        quantity: 10,
+        unit_price: 200,
+        value: 2000,
+        price_source: "manual",
+        price_fetched_at: null,
+        created_at: "",
+        updated_at: "",
+      },
+    ]);
+    const lines = await listLinesBySnapshot(50);
+    expect(lines).toHaveLength(1);
+    expect(lines[0].value).toBe(2000);
+    expect(lines[0].quantity).toBe(10);
+    expect(lines[0].unit_price).toBe(200);
+
+    // ---- 7. Link a transaction (id=42) as a +CAD deposit (in) ----
+    // linkTransfer: SELECT existing duplicate (none), then INSERT.
+    queueSelects([]); // no existing duplicate
+    queueExecutes({ lastInsertId: 9 });
+    const transferId = await linkTransfer(7, 42, "in", "monthly contribution");
+    expect(transferId).toBe(9);
+    const linkCall = fake.calls.find(
+      (c) =>
+        typeof c.sql === "string" &&
+        c.sql.includes("INSERT INTO balance_account_transfers")
+    );
+    expect(linkCall).toBeDefined();
+    expect(linkCall!.params).toEqual([7, 42, "in", "monthly contribution"]);
+
+    // ---- 8. Compute the account return ----
+    vi.mocked(loadProfiles).mockResolvedValueOnce({
+      active_profile_id: "max",
+      profiles: [
+        {
+          id: "max",
+          name: "Max",
+          color: "#3b82f6",
+          pin_hash: null,
+          db_filename: "max.db",
+          created_at: "0",
+        },
+      ],
+    });
+    const fakeReturn = {
+      value_start: 1500,
+      value_end: 2000,
+      net_contributions: 400,
+      return_pct: 0.0667, // (2000 - 1500 - 400) / (1500 + W*400) ≈ 6.67%
+      annualized_pct: 0.28,
+      is_partial: false,
+      has_no_transfers_warning: false,
+    };
+    vi.mocked(invoke).mockResolvedValueOnce(fakeReturn);
+
+    const ret = await computeAccountReturn(7, "2026-01-01", "2026-04-25");
+    expect(ret).toEqual(fakeReturn);
+
+    // Wiring check: profile resolution + ISO date forwarding.
+    expect(invoke).toHaveBeenCalledWith("compute_account_return", {
+      dbFilename: "max.db",
+      accountId: 7,
+      periodStart: "2026-01-01",
+      periodEnd: "2026-04-25",
+    });
+
+    // ---- Cross-step sanity: every coherent value matches expectations.
+    // The end snapshot value (2000) matches what we saved.
+    expect(ret.value_end).toBe(2000);
+    // The reported return is a finite, non-zero number on a non-trivial period.
+    expect(ret.return_pct).not.toBeNull();
+    expect(Number.isFinite(ret.return_pct!)).toBe(true);
+    // Net contributions match the 1 linked transfer (+400 in).
+    expect(ret.net_contributions).toBeGreaterThan(0);
+  });
+
+  it("supports unlink as the inverse of link", async () => {
+    queueExecutes({ rowsAffected: 1 });
+    await expect(unlinkTransfer(7, 42)).resolves.toBeUndefined();
+    const unlinkCall = fake.calls.find(
+      (c) =>
+        typeof c.sql === "string" &&
+        c.sql.includes("DELETE FROM balance_account_transfers")
+    );
+    expect(unlinkCall!.params).toEqual([7, 42]);
+  });
+
+  it("listAccountTransfers reads back what link wrote (joined view)", async () => {
+    queueSelects([
+      {
+        id: 9,
+        account_id: 7,
+        transaction_id: 42,
+        direction: "in",
+        notes: "monthly contribution",
+        created_at: "2026-04-25 10:00:00",
+        transaction_date: "2026-04-15",
+        transaction_description: "Wealthsimple contrib",
+        transaction_amount: -400,
+        account_name: "VFV (Wealthsimple)",
+      },
+    ]);
+    const links = await listAccountTransfers(7);
+    expect(links).toHaveLength(1);
+    expect(links[0].direction).toBe("in");
+    expect(links[0].account_name).toBe("VFV (Wealthsimple)");
+  });
+});
+
+// ---------------------------------------------------------------------------
+// 2. Currency lock — CAD only at the MVP
+// ---------------------------------------------------------------------------
+//
+// The MVP locks accounts to CAD: the SQL CHECK is `currency = 'CAD'` and the
+// service rejects any other value with a typed `currency_unsupported` before
+// the SQL even fires. Asserts:
+//   - USD is rejected with the typed code,
+//   - the rejection happens BEFORE any SELECT/EXECUTE on the DB,
+//   - the default (no `currency` field) flows through and lands as 'CAD',
+//   - the SQL CHECK side is covered in Rust (lib.rs `migration_v9_*` tests).
+
+describe("integration — currency lock (CAD only)", () => {
+  it("rejects USD at the service level with a typed error", async () => {
+    await expect(
+      createBalanceAccount({
+        balance_category_id: 1,
+        name: "USD account",
+        currency: "USD",
+      })
+    ).rejects.toBeInstanceOf(BalanceServiceError);
+
+    try {
+      await createBalanceAccount({
+        balance_category_id: 1,
+        name: "USD account",
+        currency: "USD",
+      });
+    } catch (e) {
+      expect((e as BalanceServiceError).code).toBe("currency_unsupported");
+    }
+    // CRITICAL: the rejection must happen up-front — no DB hit.
+    expect(fake.calls.length).toBe(0);
+  });
+
+  it("accepts the default and persists 'CAD' explicitly", async () => {
+    queueSelects([
+      {
+        id: 1,
+        key: "cash",
+        i18n_key: "balance.category.cash",
+        kind: "simple",
+        sort_order: 10,
+        is_active: 1,
+        is_seed: 1,
+      },
+    ]);
+    queueExecutes({ lastInsertId: 5 });
+    await createBalanceAccount({
+      balance_category_id: 1,
+      name: "Encaisse",
+    });
+    const insertCall = fake.calls.find(
+      (c) =>
+        typeof c.sql === "string" &&
+        c.sql.includes("INSERT INTO balance_accounts")
+    );
+    expect(insertCall).toBeDefined();
+    // [category_id, name, symbol, currency, notes]
+    expect(insertCall!.params).toEqual([1, "Encaisse", null, "CAD", null]);
+  });
+
+  it("rejects EUR / GBP / JPY too — not a CAD-only typo allowlist", async () => {
+    for (const ccy of ["EUR", "GBP", "JPY", "AUD"]) {
+      await expect(
+        createBalanceAccount({
+          balance_category_id: 1,
+          name: `Mystery ${ccy}`,
+          currency: ccy,
+        })
+      ).rejects.toMatchObject({ code: "currency_unsupported" });
+    }
+    expect(fake.calls.length).toBe(0);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// 3. Priced-kind invariant — coherence of the qty × price = value chain
+// ---------------------------------------------------------------------------
+//
+// Tied to the priced-kind path, but at the integration layer: a snapshot
+// saved with a drifting (qty * price ≠ value) line must be rejected before
+// any DB mutation, so the SQL CHECK never has the chance to fire and we
+// don't accidentally clear pre-existing lines.
+
+describe("integration — priced invariant rejects out-of-tolerance saves", () => {
+  it("does not run DELETE when one line is bad", async () => {
+    queueSelects([
+      {
+        id: 50,
+        snapshot_date: "2026-04-25",
+        notes: null,
+        created_at: "",
+        updated_at: "",
+      },
+    ]);
+    await expect(
+      upsertSnapshotLines(50, [
+        { account_id: 1, value: 1000 },
+        {
+          account_id: 7,
+          account_kind: "priced",
+          quantity: 10,
+          unit_price: 25,
+          // expected ≈ 250, way beyond ε
+          value: 999,
+        },
+      ])
+    ).rejects.toMatchObject({ code: "snapshot_priced_value_mismatch" });
+
+    // Critical safety: the DELETE must not have fired — otherwise the user
+    // would lose all existing lines on a partial save.
+    const deletes = fake.calls.filter(
+      (c) =>
+        typeof c.sql === "string" &&
+        c.sql.includes("DELETE FROM balance_snapshot_lines")
+    );
+    expect(deletes).toHaveLength(0);
+  });
+
+  it("accepts a drift just within the tolerance", async () => {
+    queueSelects([
+      {
+        id: 50,
+        snapshot_date: "2026-04-25",
+        notes: null,
+        created_at: "",
+        updated_at: "",
+      },
+    ]);
+    queueExecutes(
+      { rowsAffected: 0 },
+      { lastInsertId: 1 },
+      { rowsAffected: 1 }
+    );
+    // 12.34 * 1.07 = 13.2038... — drift well within ε = 0.01
+    const drift = PRICED_VALUE_TOLERANCE * 0.5;
+    await expect(
+      upsertSnapshotLines(50, [
+        {
+          account_id: 7,
+          account_kind: "priced",
+          quantity: 10,
+          unit_price: 10,
+          value: 100 + drift,
+        },
+      ])
+    ).resolves.toBeUndefined();
+  });
+});
+
+// ---------------------------------------------------------------------------
+// 4. Returns: malformed period dates rejected before the Tauri invoke
+// ---------------------------------------------------------------------------
+
+describe("integration — computeAccountReturn validates dates client-side", () => {
+  it("rejects non-ISO dates without invoking the Rust command", async () => {
+    vi.mocked(loadProfiles).mockResolvedValueOnce({
+      active_profile_id: "max",
+      profiles: [
+        {
+          id: "max",
+          name: "Max",
+          color: "#000",
+          pin_hash: null,
+          db_filename: "max.db",
+          created_at: "0",
+        },
+      ],
+    });
+    await expect(
+      computeAccountReturn(7, "01/01/2026", "2026-04-25")
+    ).rejects.toBeInstanceOf(BalanceServiceError);
+    // The Tauri side must NOT have been hit — fail-fast on bad dates.
+    expect(invoke).not.toHaveBeenCalled();
+  });
+
+  it("rejects when the active profile cannot be resolved", async () => {
+    vi.mocked(loadProfiles).mockResolvedValueOnce({
+      active_profile_id: "ghost",
+      profiles: [],
+    });
+    await expect(
+      computeAccountReturn(7, "2026-01-01", "2026-04-25")
+    ).rejects.toMatchObject({ code: "transfer_active_profile_unknown" });
+    expect(invoke).not.toHaveBeenCalled();
+  });
+
+  it("forwards a partial-period AccountReturn shape unchanged", async () => {
+    // When `is_partial = true` (no V_start), the Rust side returns a payload
+    // with explicit nulls. The TS shim must not coerce them away.
+    vi.mocked(loadProfiles).mockResolvedValueOnce({
+      active_profile_id: "max",
+      profiles: [
+        {
+          id: "max",
+          name: "Max",
+          color: "#000",
+          pin_hash: null,
+          db_filename: "max.db",
+          created_at: "0",
+        },
+      ],
+    });
+    const partial = {
+      value_start: null,
+      value_end: 1500,
+      net_contributions: 200,
+      return_pct: null,
+      annualized_pct: null,
+      is_partial: true,
+      has_no_transfers_warning: false,
+    };
+    vi.mocked(invoke).mockResolvedValueOnce(partial);
+    const out = await computeAccountReturn(7, "2026-01-01", "2026-04-25");
+    expect(out).toEqual(partial);
+    expect(out.is_partial).toBe(true);
+    expect(out.value_start).toBeNull();
+  });
+});