diff --git a/packages/api/src/__tests__/assistant-tools-estimate-generate-weekly-phasing-errors.test.ts b/packages/api/src/__tests__/assistant-tools-estimate-generate-weekly-phasing-errors.test.ts
new file mode 100644
index 0000000..e2fd533
--- /dev/null
+++ b/packages/api/src/__tests__/assistant-tools-estimate-generate-weekly-phasing-errors.test.ts
@@ -0,0 +1,174 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { PermissionKey, SystemRole } from "@capakraken/shared";
+
+vi.mock("@capakraken/application", async (importOriginal) => {
+  const actual = await importOriginal<typeof import("@capakraken/application")>();
+  return {
+    ...actual,
+    approveEstimateVersion: vi.fn(),
+    cloneEstimate: vi.fn(),
+    createEstimateExport: vi.fn(),
+    createEstimatePlanningHandoff: vi.fn(),
+    createEstimateRevision: vi.fn(),
+    getDashboardBudgetForecast: vi.fn().mockResolvedValue([]),
+    getDashboardPeakTimes: vi.fn().mockResolvedValue([]),
+    getEstimateById: vi.fn(),
+    listAssignmentBookings: vi.fn().mockResolvedValue([]),
+    submitEstimateVersion: vi.fn(),
+    updateEstimateDraft: vi.fn(),
+  };
+});
+
+import { getEstimateById } from "@capakraken/application";
+
+import { executeTool } from "../router/assistant-tools.js";
+import {
+  createToolContext,
+  resetEstimateToolMocks,
+} from "./assistant-tools-estimate-test-helpers.js";
+
+const managerOptions = {
+  userRole: SystemRole.MANAGER,
+  permissions: [PermissionKey.MANAGE_PROJECTS],
+} as const;
+
+describe("assistant estimate weekly phasing generation errors", () => {
+  beforeEach(() => {
+    resetEstimateToolMocks();
+  });
+
+  it("returns a stable error when generate_estimate_weekly_phasing cannot find the estimate", async () => {
+    vi.mocked(getEstimateById).mockResolvedValueOnce(null as never);
+
+    const ctx = createToolContext({}, managerOptions);
+    const result = await executeTool(
+      "generate_estimate_weekly_phasing",
+      JSON.stringify({
+        estimateId: "est_missing",
+        startDate: "2026-04-01",
+        endDate: "2026-04-30",
+      }),
+      ctx,
+    );
+
+    expect(JSON.parse(result.content)).toEqual({
+      error: "Estimate not found with the given criteria.",
+    });
+  });
+
+  it("returns a stable error when generate_estimate_weekly_phasing has no working version", async () => {
+    vi.mocked(getEstimateById).mockResolvedValueOnce({
+      id: "est_1",
+      name: "Estimate One",
+      versions: [],
+    } as Awaited<ReturnType<typeof getEstimateById>>);
+
+    const ctx = createToolContext({}, managerOptions);
+    const result = await executeTool(
+      "generate_estimate_weekly_phasing",
+      JSON.stringify({
+        estimateId: "est_1",
+        startDate: "2026-04-01",
+        endDate: "2026-04-30",
+      }),
+      ctx,
+    );
+
+    expect(JSON.parse(result.content)).toEqual({
+      error: "Estimate has no working version.",
+    });
+  });
+
+  it("returns a stable error when generate_estimate_weekly_phasing loses a demand line with model metadata", async () => {
+    vi.mocked(getEstimateById).mockResolvedValueOnce({
+      id: "est_2",
+      name: "Estimate Two",
+      versions: [
+        {
+          id: "ver_1",
+          status: "WORKING",
+          demandLines: [
+            {
+              id: "line_missing",
+              hours: 40,
+              metadata: {},
+            },
+          ],
+        },
+      ],
+    } as Awaited<ReturnType<typeof getEstimateById>>);
+
+    const ctx = createToolContext(
+      {
+        estimateDemandLine: {
+          update: vi.fn().mockRejectedValue({
+            code: "P2025",
+            message: "Record not found",
+            meta: { modelName: "EstimateDemandLine" },
+          }),
+        },
+      },
+      managerOptions,
+    );
+
+    const result = await executeTool(
+      "generate_estimate_weekly_phasing",
+      JSON.stringify({
+        estimateId: "est_2",
+        startDate: "2026-04-01",
+        endDate: "2026-04-30",
+      }),
+      ctx,
+    );
+
+    expect(JSON.parse(result.content)).toEqual({
+      error: "Estimate demand line not found with the given criteria.",
+    });
+  });
+
+  it("returns a stable error when generate_estimate_weekly_phasing loses a demand line with generic P2025 metadata", async () => {
+    vi.mocked(getEstimateById).mockResolvedValueOnce({
+      id: "est_3",
+      name: "Estimate Three",
+      versions: [
+        {
+          id: "ver_2",
+          status: "WORKING",
+          demandLines: [
+            {
+              id: "line_missing_generic",
+              hours: 40,
+              metadata: {},
+            },
+          ],
+        },
+      ],
+    } as Awaited<ReturnType<typeof getEstimateById>>);
+
+    const ctx = createToolContext(
+      {
+        estimateDemandLine: {
+          update: vi.fn().mockRejectedValue({
+            code: "P2025",
+            message: "Record to update not found",
+          }),
+        },
+      },
+      managerOptions,
+    );
+
+    const result = await executeTool(
+      "generate_estimate_weekly_phasing",
+      JSON.stringify({
+        estimateId: "est_3",
+        startDate: "2026-04-01",
+        endDate: "2026-04-30",
+      }),
+      ctx,
+    );
+
+    expect(JSON.parse(result.content)).toEqual({
+      error: "Estimate demand line not found with the given criteria.",
+    });
+  });
+});
diff --git a/packages/api/src/__tests__/assistant-tools-estimate-get-weekly-phasing-errors.test.ts b/packages/api/src/__tests__/assistant-tools-estimate-get-weekly-phasing-errors.test.ts
new file mode 100644
index 0000000..80e73d7
--- /dev/null
+++ b/packages/api/src/__tests__/assistant-tools-estimate-get-weekly-phasing-errors.test.ts
@@ -0,0 +1,72 @@
+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,
+    approveEstimateVersion: vi.fn(),
+    cloneEstimate: vi.fn(),
+    createEstimateExport: vi.fn(),
+    createEstimatePlanningHandoff: vi.fn(),
+    createEstimateRevision: vi.fn(),
+    getDashboardBudgetForecast: vi.fn().mockResolvedValue([]),
+    getDashboardPeakTimes: vi.fn().mockResolvedValue([]),
+    getEstimateById: vi.fn(),
+    listAssignmentBookings: vi.fn().mockResolvedValue([]),
+    submitEstimateVersion: vi.fn(),
+    updateEstimateDraft: vi.fn(),
+  };
+});
+
+import { getEstimateById } from "@capakraken/application";
+
+import { executeTool } from "../router/assistant-tools.js";
+import {
+  createToolContext,
+  resetEstimateToolMocks,
+} from "./assistant-tools-estimate-test-helpers.js";
+
+describe("assistant estimate weekly phasing read errors", () => {
+  beforeEach(() => {
+    resetEstimateToolMocks();
+  });
+
+  it("returns a stable error when get_estimate_weekly_phasing cannot find the estimate", async () => {
+    vi.mocked(getEstimateById).mockResolvedValueOnce(null as never);
+
+    const ctx = createToolContext({}, {
+      userRole: SystemRole.CONTROLLER,
+    });
+    const result = await executeTool(
+      "get_estimate_weekly_phasing",
+      JSON.stringify({ estimateId: "est_missing" }),
+      ctx,
+    );
+
+    expect(JSON.parse(result.content)).toEqual({
+      error: "Estimate not found with the given criteria.",
+    });
+  });
+
+  it("returns a stable error when get_estimate_weekly_phasing cannot find a working version", async () => {
+    vi.mocked(getEstimateById).mockResolvedValueOnce({
+      id: "est_empty",
+      name: "Estimate Empty",
+      versions: [],
+    } as Awaited<ReturnType<typeof getEstimateById>>);
+
+    const ctx = createToolContext({}, {
+      userRole: SystemRole.CONTROLLER,
+    });
+    const result = await executeTool(
+      "get_estimate_weekly_phasing",
+      JSON.stringify({ estimateId: "est_empty" }),
+      ctx,
+    );
+
+    expect(JSON.parse(result.content)).toEqual({
+      error: "Estimate version not found with the given criteria.",
+    });
+  });
+});