diff --git a/extensions/llama-cpp/src/llama-server-install.test.ts b/extensions/llama-cpp/src/llama-server-install.test.ts
new file mode 100644
index 000000000000..5fff8c0ccdbb
--- /dev/null
+++ b/extensions/llama-cpp/src/llama-server-install.test.ts
@@ -0,0 +1,150 @@
+import { createHash } from "node:crypto";
+import fs from "node:fs/promises";
+import os from "node:os";
+import path from "node:path";
+import { afterEach, describe, expect, it, vi } from "vitest";
+
+const mocks = vi.hoisted(() => ({
+  fetchWithSsrFGuard: vi.fn(),
+}));
+
+vi.mock("openclaw/plugin-sdk/ssrf-runtime", async (importOriginal) => ({
+  ...(await importOriginal<typeof import("openclaw/plugin-sdk/ssrf-runtime")>()),
+  fetchWithSsrFGuard: mocks.fetchWithSsrFGuard,
+}));
+
+import { downloadVerifiedFile } from "./llama-server-install.js";
+
+type FileHandle = Awaited<ReturnType<typeof fs.open>>;
+
+const tempRoots: string[] = [];
+
+afterEach(async () => {
+  vi.restoreAllMocks();
+  mocks.fetchWithSsrFGuard.mockReset();
+  await Promise.all(
+    tempRoots.splice(0).map((root) => fs.rm(root, { recursive: true, force: true })),
+  );
+});
+
+async function createDestination(): Promise<{ destination: string; root: string }> {
+  const root = await fs.mkdtemp(path.join(os.tmpdir(), "llama-server-download-"));
+  tempRoots.push(root);
+  return { destination: path.join(root, "model.gguf"), root };
+}
+
+function mockDownload(payload: Buffer): ReturnType<typeof vi.fn> {
+  const release = vi.fn();
+  mocks.fetchWithSsrFGuard.mockResolvedValue({
+    response: new Response(new Uint8Array(payload), {
+      headers: { "content-length": String(payload.byteLength) },
+    }),
+    release,
+  });
+  return release;
+}
+
+function injectFileHandle(customize: (handle: FileHandle) => void): void {
+  const actualOpen = fs.open.bind(fs);
+  vi.spyOn(fs, "open").mockImplementation(async (...args) => {
+    const handle = await actualOpen(...args);
+    customize(handle);
+    return handle;
+  });
+}
+
+function installWriteFileThroughWrite(handle: FileHandle): void {
+  handle.writeFile = (async (data: string | NodeJS.ArrayBufferView) => {
+    const buffer =
+      typeof data === "string"
+        ? Buffer.from(data)
+        : Buffer.from(data.buffer, data.byteOffset, data.byteLength);
+    let offset = 0;
+    while (offset < buffer.byteLength) {
+      const { bytesWritten } = await handle.write(buffer, offset, buffer.byteLength - offset);
+      if (bytesWritten === 0) {
+        throw new Error("injected zero-byte write");
+      }
+      offset += bytesWritten;
+    }
+  }) as typeof handle.writeFile;
+}
+
+describe("downloadVerifiedFile", () => {
+  it("persists complete chunks before reporting progress under positive short writes", async () => {
+    const payload = Buffer.from("short writes must not truncate verified downloads");
+    const { destination, root } = await createDestination();
+    const release = mockDownload(payload);
+    const onProgress = vi.fn();
+    const writes: number[] = [];
+    injectFileHandle((handle) => {
+      const actualWrite = handle.write.bind(handle);
+      let firstWrite = true;
+      handle.write = (async (
+        buffer: Uint8Array,
+        offset?: number | null,
+        length?: number | null,
+        position?: number | null,
+      ) => {
+        const start = offset ?? 0;
+        const requested = length ?? buffer.byteLength - start;
+        const result = await actualWrite(
+          buffer,
+          start,
+          firstWrite ? Math.min(7, requested) : requested,
+          position,
+        );
+        firstWrite = false;
+        writes.push(result.bytesWritten);
+        return result;
+      }) as typeof handle.write;
+      installWriteFileThroughWrite(handle);
+    });
+
+    await downloadVerifiedFile({
+      url: "https://downloads.example/model.gguf",
+      destination,
+      expectedSha256: createHash("sha256").update(payload).digest("hex"),
+      expectedSize: payload.byteLength,
+      onProgress,
+    });
+
+    expect(await fs.readFile(destination)).toEqual(payload);
+    expect(writes[0]).toBe(7);
+    expect(writes.length).toBeGreaterThan(1);
+    expect(writes.reduce((total, size) => total + size, 0)).toBe(payload.byteLength);
+    const published = await fs.stat(destination);
+    expect(onProgress).toHaveBeenLastCalledWith(
+      expect.objectContaining({ downloadedSize: published.size, totalSize: payload.byteLength }),
+    );
+    if (process.platform !== "win32") {
+      expect(published.mode & 0o777).toBe(0o600);
+    }
+    expect(release).toHaveBeenCalledOnce();
+    expect(await fs.readdir(root)).toEqual(["model.gguf"]);
+  });
+
+  it("keeps the destination absent and removes the partial file after a write failure", async () => {
+    const payload = Buffer.from("a download that cannot be persisted");
+    const { destination, root } = await createDestination();
+    const release = mockDownload(payload);
+    injectFileHandle((handle) => {
+      handle.write = vi.fn(async () => {
+        throw new Error("injected write failure");
+      }) as typeof handle.write;
+      installWriteFileThroughWrite(handle);
+    });
+
+    await expect(
+      downloadVerifiedFile({
+        url: "https://downloads.example/model.gguf",
+        destination,
+        expectedSha256: createHash("sha256").update(payload).digest("hex"),
+        expectedSize: payload.byteLength,
+      }),
+    ).rejects.toThrow("injected write failure");
+    await expect(fs.stat(destination)).rejects.toMatchObject({ code: "ENOENT" });
+    expect(await fs.readdir(root)).toEqual([]);
+    expect(release).toHaveBeenCalledOnce();
+  });
+});
diff --git a/extensions/llama-cpp/src/llama-server-install.ts b/extensions/llama-cpp/src/llama-server-install.ts
index 191c6f14b8d3..b033e031bb93 100644
--- a/extensions/llama-cpp/src/llama-server-install.ts
+++ b/extensions/llama-cpp/src/llama-server-install.ts
@@ -142,7 +142,7 @@ export async function downloadVerifiedFile(params: {
             break;
           }
           const chunk = Buffer.from(value);
-          await handle.write(chunk);
+          await handle.writeFile(chunk);
           hash.update(chunk);
           downloadedSize += chunk.byteLength;
           const now = Date.now();