diff --git a/packages/api/src/__tests__/assistant-tools-pending-vacation-approvals.test.ts b/packages/api/src/__tests__/assistant-tools-pending-vacation-approvals.test.ts
new file mode 100644
index 0000000..50c9643
--- /dev/null
+++ b/packages/api/src/__tests__/assistant-tools-pending-vacation-approvals.test.ts
@@ -0,0 +1,66 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { SystemRole } from "@capakraken/shared";
+
+vi.mock("@capakraken/application", async (importOriginal) => {
+  const actual = await importOriginal<typeof import("@capakraken/application")>();
+  return {
+    ...actual,
+    getDashboardBudgetForecast: vi.fn().mockResolvedValue([]),
+    listAssignmentBookings: vi.fn().mockResolvedValue([]),
+  };
+});
+
+vi.mock("../lib/audit.js", () => ({
+  createAuditEntry: vi.fn().mockResolvedValue(undefined),
+}));
+
+import { executeTool } from "../router/assistant-tools.js";
+import { createToolContext } from "./assistant-tools-holiday-capacity-test-helpers.js";
+
+describe("assistant pending vacation approvals tool", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("routes pending vacation approvals through the vacation router path", async () => {
+    const db = {
+      vacation: {
+        findMany: vi.fn().mockResolvedValue([
+          {
+            id: "vac_1",
+            type: "ANNUAL",
+            startDate: new Date("2026-07-01T00:00:00.000Z"),
+            endDate: new Date("2026-07-03T00:00:00.000Z"),
+            isHalfDay: false,
+            resource: { displayName: "Bruce Banner", eid: "BB-1", chapter: "CGI" },
+            requestedBy: { id: "user_2", name: "Manager", email: "manager@example.com" },
+          },
+        ]),
+      },
+    };
+    const ctx = createToolContext(db, [], SystemRole.MANAGER);
+
+    const result = await executeTool(
+      "get_pending_vacation_approvals",
+      JSON.stringify({ limit: 10 }),
+      ctx,
+    );
+
+    expect(db.vacation.findMany).toHaveBeenCalledWith({
+      where: { status: "PENDING" },
+      include: {
+        resource: { select: expect.any(Object) },
+        requestedBy: { select: { id: true, name: true, email: true } },
+      },
+      orderBy: { startDate: "asc" },
+    });
+    expect(JSON.parse(result.content)).toEqual([
+      expect.objectContaining({
+        id: "vac_1",
+        resource: "Bruce Banner",
+        eid: "BB-1",
+        chapter: "CGI",
+      }),
+    ]);
+  });
+});
diff --git a/packages/api/src/__tests__/assistant-tools-vacation-approval-errors.test.ts b/packages/api/src/__tests__/assistant-tools-vacation-approval-errors.test.ts
new file mode 100644
index 0000000..214efd9
--- /dev/null
+++ b/packages/api/src/__tests__/assistant-tools-vacation-approval-errors.test.ts
@@ -0,0 +1,115 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { SystemRole } from "@capakraken/shared";
+import { TRPCError } from "@trpc/server";
+
+vi.mock("@capakraken/application", async (importOriginal) => {
+  const actual = await importOriginal<typeof import("@capakraken/application")>();
+  return {
+    ...actual,
+    approveEstimateVersion: vi.fn(),
+    cloneEstimate: vi.fn(),
+    commitDispoImportBatch: vi.fn(),
+    countPlanningEntries: vi.fn().mockResolvedValue({ countsByRoleId: new Map() }),
+    createEstimateExport: vi.fn(),
+    createEstimatePlanningHandoff: vi.fn(),
+    createEstimateRevision: vi.fn(),
+    assessDispoImportReadiness: vi.fn(),
+    loadResourceDailyAvailabilityContexts: vi.fn().mockResolvedValue(new Map()),
+    getDashboardDemand: vi.fn().mockResolvedValue([]),
+    getDashboardBudgetForecast: vi.fn().mockResolvedValue([]),
+    getDashboardOverview: vi.fn(),
+    getDashboardSkillGapSummary: vi.fn().mockResolvedValue({
+      roleGaps: [],
+      totalOpenPositions: 0,
+      skillSupplyTop10: [],
+      resourcesByRole: [],
+    }),
+    getDashboardProjectHealth: vi.fn().mockResolvedValue([]),
+    getDashboardPeakTimes: vi.fn().mockResolvedValue([]),
+    getDashboardTopValueResources: vi.fn().mockResolvedValue([]),
+    getEstimateById: vi.fn(),
+    listAssignmentBookings: vi.fn().mockResolvedValue([]),
+    stageDispoImportBatch: vi.fn(),
+    submitEstimateVersion: vi.fn(),
+    updateEstimateDraft: vi.fn(),
+  };
+});
+
+import { executeTool, type ToolContext } from "../router/assistant-tools.js";
+import { createToolContext } from "./assistant-tools-vacation-entitlement-test-helpers.js";
+
+describe("assistant vacation approval error paths", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("returns a stable assistant error when vacation approval cannot resolve the request", async () => {
+    const ctx = createToolContext(
+      {
+        vacation: {
+          findUnique: vi.fn().mockRejectedValue(
+            new TRPCError({ code: "NOT_FOUND", message: "Vacation not found" }),
+          ),
+        },
+      },
+      { userRole: SystemRole.MANAGER },
+    );
+
+    const result = await executeTool(
+      "approve_vacation",
+      JSON.stringify({ vacationId: "vac_missing" }),
+      ctx,
+    );
+
+    expect(JSON.parse(result.content)).toEqual({
+      error: "Vacation not found with the given criteria.",
+    });
+  });
+
+  it("returns a stable assistant error when vacation approval violates lifecycle preconditions", async () => {
+    const ctx = createToolContext(
+      {
+        vacation: {
+          findUnique: vi.fn().mockResolvedValue({
+            id: "vac_approved",
+            resource: { displayName: "Alice Example" },
+          }),
+        },
+      },
+      { userRole: SystemRole.MANAGER },
+    );
+
+    const result = await executeTool(
+      "approve_vacation",
+      JSON.stringify({ vacationId: "vac_approved" }),
+      {
+        ...ctx,
+        db: {
+          ...ctx.db,
+          vacation: {
+            ...((ctx.db as Record<string, unknown>).vacation as Record<string, unknown>),
+            findUnique: vi.fn()
+              .mockResolvedValueOnce({
+                id: "vac_approved",
+                resource: { displayName: "Alice Example" },
+              })
+              .mockResolvedValueOnce({
+                id: "vac_approved",
+                resource: { displayName: "Alice Example" },
+              }),
+            update: vi.fn().mockRejectedValue(
+              new TRPCError({
+                code: "BAD_REQUEST",
+                message: "Only PENDING, CANCELLED, or REJECTED vacations can be approved",
+              }),
+            ),
+          },
+        } as ToolContext["db"],
+      },
+    );
+
+    expect(JSON.parse(result.content)).toEqual({
+      error: "Vacation cannot be approved in its current status.",
+    });
+  });
+});
diff --git a/packages/api/src/__tests__/assistant-tools-vacation-cancellation-errors.test.ts b/packages/api/src/__tests__/assistant-tools-vacation-cancellation-errors.test.ts
new file mode 100644
index 0000000..c65be47
--- /dev/null
+++ b/packages/api/src/__tests__/assistant-tools-vacation-cancellation-errors.test.ts
@@ -0,0 +1,119 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { VacationStatus } from "@capakraken/db";
+import { SystemRole } from "@capakraken/shared";
+import { TRPCError } from "@trpc/server";
+
+vi.mock("@capakraken/application", async (importOriginal) => {
+  const actual = await importOriginal<typeof import("@capakraken/application")>();
+  return {
+    ...actual,
+    approveEstimateVersion: vi.fn(),
+    cloneEstimate: vi.fn(),
+    commitDispoImportBatch: vi.fn(),
+    countPlanningEntries: vi.fn().mockResolvedValue({ countsByRoleId: new Map() }),
+    createEstimateExport: vi.fn(),
+    createEstimatePlanningHandoff: vi.fn(),
+    createEstimateRevision: vi.fn(),
+    assessDispoImportReadiness: vi.fn(),
+    loadResourceDailyAvailabilityContexts: vi.fn().mockResolvedValue(new Map()),
+    getDashboardDemand: vi.fn().mockResolvedValue([]),
+    getDashboardBudgetForecast: vi.fn().mockResolvedValue([]),
+    getDashboardOverview: vi.fn(),
+    getDashboardSkillGapSummary: vi.fn().mockResolvedValue({
+      roleGaps: [],
+      totalOpenPositions: 0,
+      skillSupplyTop10: [],
+      resourcesByRole: [],
+    }),
+    getDashboardProjectHealth: vi.fn().mockResolvedValue([]),
+    getDashboardPeakTimes: vi.fn().mockResolvedValue([]),
+    getDashboardTopValueResources: vi.fn().mockResolvedValue([]),
+    getEstimateById: vi.fn(),
+    listAssignmentBookings: vi.fn().mockResolvedValue([]),
+    stageDispoImportBatch: vi.fn(),
+    submitEstimateVersion: vi.fn(),
+    updateEstimateDraft: vi.fn(),
+  };
+});
+
+import { executeTool, type ToolContext } from "../router/assistant-tools.js";
+import { createToolContext } from "./assistant-tools-vacation-entitlement-test-helpers.js";
+
+describe("assistant vacation cancellation error paths", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("returns a stable assistant error when vacation cancellation cannot resolve the request", async () => {
+    const ctx = createToolContext(
+      {
+        vacation: {
+          findUnique: vi.fn().mockRejectedValue(
+            new TRPCError({ code: "NOT_FOUND", message: "Vacation not found" }),
+          ),
+        },
+      },
+      { userRole: SystemRole.MANAGER },
+    );
+
+    const result = await executeTool(
+      "cancel_vacation",
+      JSON.stringify({ vacationId: "vac_missing" }),
+      ctx,
+    );
+
+    expect(JSON.parse(result.content)).toEqual({
+      error: "Vacation not found with the given criteria.",
+    });
+  });
+
+  it("returns a stable assistant error when vacation cancellation violates lifecycle preconditions", async () => {
+    const ctx = createToolContext(
+      {
+        vacation: {
+          findUnique: vi.fn().mockResolvedValue({
+            id: "vac_cancelled",
+            requestedById: "user_1",
+            resource: { displayName: "Alice Example", userId: "user_1" },
+          }),
+        },
+      },
+      { userRole: SystemRole.USER, permissions: [] },
+    );
+
+    const result = await executeTool(
+      "cancel_vacation",
+      JSON.stringify({ vacationId: "vac_cancelled" }),
+      {
+        ...ctx,
+        db: {
+          ...ctx.db,
+          vacation: {
+            ...((ctx.db as Record<string, unknown>).vacation as Record<string, unknown>),
+            findUnique: vi.fn()
+              .mockResolvedValueOnce({
+                id: "vac_cancelled",
+                requestedById: "user_1",
+                resource: { displayName: "Alice Example", userId: "user_1" },
+              })
+              .mockResolvedValueOnce({
+                id: "vac_cancelled",
+                status: VacationStatus.CANCELLED,
+                resource: { displayName: "Alice Example" },
+              }),
+            update: vi.fn().mockRejectedValue(
+              new TRPCError({
+                code: "BAD_REQUEST",
+                message: "Already cancelled",
+              }),
+            ),
+          },
+        } as ToolContext["db"],
+      },
+    );
+
+    expect(JSON.parse(result.content)).toEqual({
+      error: "Vacation cannot be cancelled in its current status.",
+    });
+  });
+});
diff --git a/packages/api/src/__tests__/assistant-tools-vacation-rejection-errors.test.ts b/packages/api/src/__tests__/assistant-tools-vacation-rejection-errors.test.ts
new file mode 100644
index 0000000..d459967
--- /dev/null
+++ b/packages/api/src/__tests__/assistant-tools-vacation-rejection-errors.test.ts
@@ -0,0 +1,115 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { SystemRole } from "@capakraken/shared";
+import { TRPCError } from "@trpc/server";
+
+vi.mock("@capakraken/application", async (importOriginal) => {
+  const actual = await importOriginal<typeof import("@capakraken/application")>();
+  return {
+    ...actual,
+    approveEstimateVersion: vi.fn(),
+    cloneEstimate: vi.fn(),
+    commitDispoImportBatch: vi.fn(),
+    countPlanningEntries: vi.fn().mockResolvedValue({ countsByRoleId: new Map() }),
+    createEstimateExport: vi.fn(),
+    createEstimatePlanningHandoff: vi.fn(),
+    createEstimateRevision: vi.fn(),
+    assessDispoImportReadiness: vi.fn(),
+    loadResourceDailyAvailabilityContexts: vi.fn().mockResolvedValue(new Map()),
+    getDashboardDemand: vi.fn().mockResolvedValue([]),
+    getDashboardBudgetForecast: vi.fn().mockResolvedValue([]),
+    getDashboardOverview: vi.fn(),
+    getDashboardSkillGapSummary: vi.fn().mockResolvedValue({
+      roleGaps: [],
+      totalOpenPositions: 0,
+      skillSupplyTop10: [],
+      resourcesByRole: [],
+    }),
+    getDashboardProjectHealth: vi.fn().mockResolvedValue([]),
+    getDashboardPeakTimes: vi.fn().mockResolvedValue([]),
+    getDashboardTopValueResources: vi.fn().mockResolvedValue([]),
+    getEstimateById: vi.fn(),
+    listAssignmentBookings: vi.fn().mockResolvedValue([]),
+    stageDispoImportBatch: vi.fn(),
+    submitEstimateVersion: vi.fn(),
+    updateEstimateDraft: vi.fn(),
+  };
+});
+
+import { executeTool, type ToolContext } from "../router/assistant-tools.js";
+import { createToolContext } from "./assistant-tools-vacation-entitlement-test-helpers.js";
+
+describe("assistant vacation rejection error paths", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("returns a stable assistant error when vacation rejection cannot resolve the request", async () => {
+    const ctx = createToolContext(
+      {
+        vacation: {
+          findUnique: vi.fn().mockRejectedValue(
+            new TRPCError({ code: "NOT_FOUND", message: "Vacation not found" }),
+          ),
+        },
+      },
+      { userRole: SystemRole.MANAGER },
+    );
+
+    const result = await executeTool(
+      "reject_vacation",
+      JSON.stringify({ vacationId: "vac_missing", reason: "Capacity freeze" }),
+      ctx,
+    );
+
+    expect(JSON.parse(result.content)).toEqual({
+      error: "Vacation not found with the given criteria.",
+    });
+  });
+
+  it("returns a stable assistant error when vacation rejection violates lifecycle preconditions", async () => {
+    const ctx = createToolContext(
+      {
+        vacation: {
+          findUnique: vi.fn().mockResolvedValue({
+            id: "vac_approved",
+            resource: { displayName: "Alice Example" },
+          }),
+        },
+      },
+      { userRole: SystemRole.MANAGER },
+    );
+
+    const result = await executeTool(
+      "reject_vacation",
+      JSON.stringify({ vacationId: "vac_approved", reason: "Capacity freeze" }),
+      {
+        ...ctx,
+        db: {
+          ...ctx.db,
+          vacation: {
+            ...((ctx.db as Record<string, unknown>).vacation as Record<string, unknown>),
+            findUnique: vi.fn()
+              .mockResolvedValueOnce({
+                id: "vac_approved",
+                resource: { displayName: "Alice Example" },
+              })
+              .mockResolvedValueOnce({
+                id: "vac_approved",
+                resource: { displayName: "Alice Example" },
+              }),
+            update: vi.fn().mockRejectedValue(
+              new TRPCError({
+                code: "BAD_REQUEST",
+                message: "Only PENDING vacations can be rejected",
+              }),
+            ),
+          },
+        } as ToolContext["db"],
+      },
+    );
+
+    expect(JSON.parse(result.content)).toEqual({
+      error: "Vacation cannot be rejected in its current status.",
+    });
+  });
+});