diff --git a/src/lib/server/stock-pricing-service.test.ts b/src/lib/server/stock-pricing-service.test.ts
index b49dfae..dc24f7b 100644
--- a/src/lib/server/stock-pricing-service.test.ts
+++ b/src/lib/server/stock-pricing-service.test.ts
@@ -186,3 +186,95 @@ describe("updateStockItemsPricing — stock_ledger audit on cost change", () =>
     ]);
   });
 });
+
+describe("updateStockItemsPricing — input validation", () => {
+  it("rejects negative numbers", async () => {
+    const result = await updateStockItemsPricing({
+      pb: { collection: () => ({ getOne: vi.fn(), update: vi.fn(), create: vi.fn() }) } as never,
+      updates: [{ id: "abcdefghijklmno", costPrice: -1 }],
+      actor: { id: "useropid1234567", name: "Gary" },
+    });
+    expect(result.results[0]).toMatchObject({
+      ok: false,
+      reason: "validation_error",
+    });
+  });
+
+  it("rejects forbidden fields", async () => {
+    const result = await updateStockItemsPricing({
+      pb: { collection: () => ({ getOne: vi.fn(), update: vi.fn(), create: vi.fn() }) } as never,
+      updates: [
+        { id: "abcdefghijklmno", costPrice: 1, maliciousFlag: true } as never,
+      ],
+      actor: { id: "useropid1234567", name: "Gary" },
+    });
+    expect(result.results[0]).toMatchObject({
+      ok: false,
+      reason: "forbidden_field",
+    });
+  });
+});
+
+describe("updateStockItemsPricing — not_found and per-row independence", () => {
+  it("returns not_found when the row is gone", async () => {
+    const pb = {
+      collection: (name: string) => {
+        if (name === "stock_items") {
+          return {
+            getOne: vi.fn().mockRejectedValue(new Error("404 not found")),
+            update: vi.fn(),
+            create: vi.fn(),
+          };
+        }
+        if (name === "stock_ledger") {
+          return { create: vi.fn() };
+        }
+        throw new Error(`unexpected ${name}`);
+      },
+    };
+    const result = await updateStockItemsPricing({
+      pb: pb as never,
+      updates: [{ id: "missing00000000x", costPrice: 1 }],
+      actor: { id: "useropid1234567", name: "Gary" },
+    });
+    expect(result.results[0]).toMatchObject({
+      ok: false,
+      reason: "not_found",
+    });
+  });
+
+  it("does not abort sibling rows when one is not_found", async () => {
+    const updated = { id: "abcdefghijklmno", cost_price: 5, selling_price: 0, markup: 0 };
+    let nextIsMissing = true;
+    const pb = {
+      collection: (name: string) => {
+        if (name === "stock_items") {
+          return {
+            getOne: vi.fn().mockImplementation(async () => {
+              if (nextIsMissing) {
+                nextIsMissing = false;
+                throw new Error("404 not found");
+              }
+              return updated;
+            }),
+            update: vi.fn().mockResolvedValue(updated),
+            create: vi.fn(),
+          };
+        }
+        if (name === "stock_ledger") return { create: vi.fn().mockResolvedValue({ id: "l1" }) };
+        throw new Error(`unexpected ${name}`);
+      },
+    };
+    const result = await updateStockItemsPricing({
+      pb: pb as never,
+      updates: [
+        { id: "missing00000000x", costPrice: 1 },
+        { id: "abcdefghijklmno", costPrice: 5 },
+      ],
+      actor: { id: "useropid1234567", name: "Gary" },
+    });
+    expect(result.summary).toEqual({ total: 2, succeeded: 1, failed: 1 });
+    expect(result.results[0]).toMatchObject({ ok: false, reason: "not_found" });
+    expect(result.results[1]).toMatchObject({ ok: true });
+  });
+});