fix(sandbox): verify session-export download wrote a file before recording a bundle (#7367)

src/lib/actions/sandbox/sessions/download-verify.test.ts

@@ -0,0 +1,90 @@
+// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { assertDownloadedFile } from "./download-verify";
+
+describe("assertDownloadedFile", () => {
+  let dir: string;
+
+  beforeEach(() => {
+    dir = fs.mkdtempSync(path.join(os.tmpdir(), "nc-7367-verify-"));
+  });
+
+  afterEach(() => {
+    fs.rmSync(dir, { recursive: true, force: true });
+  });
+
+  it("passes when the download reported success and wrote a non-empty file", () => {
+    const target = path.join(dir, "bundle.tgz");
+    fs.writeFileSync(target, "payload");
+    expect(() =>
+      assertDownloadedFile({ status: 0 }, target, {
+        remoteLabel: "/sandbox/x.tgz",
+        sandboxName: "alpha",
+        requireNonEmpty: true,
+      }),
+    ).not.toThrow();
+  });
+
+  it("rejects a non-zero exit status with the exit code in the message", () => {
+    const target = path.join(dir, "bundle.tgz");
+    fs.writeFileSync(target, "payload");
+    expect(() =>
+      assertDownloadedFile({ status: 1 }, target, {
+        remoteLabel: "/sandbox/x.tgz",
+        sandboxName: "alpha",
+      }),
+    ).toThrow(/Failed to download '\/sandbox\/x\.tgz' from sandbox 'alpha' \(exit 1\)\./);
+  });
+
+  // The #7367 core: openshell can exit 0 while writing nothing. Trusting the
+  // exit code alone would record the rejected download as a valid bundle.
+  it("rejects exit 0 when no file was written", () => {
+    const target = path.join(dir, "missing.tgz");
+    expect(() =>
+      assertDownloadedFile({ status: 0 }, target, {
+        remoteLabel: "/sandbox/x.tgz",
+        sandboxName: "alpha",
+        requireNonEmpty: true,
+      }),
+    ).toThrow(/reported success \(exit 0\) but no file was written to/);
+  });
+
+  it("rejects exit 0 when the destination is a directory, not a regular file", () => {
+    const target = path.join(dir, "adir");
+    fs.mkdirSync(target);
+    expect(() =>
+      assertDownloadedFile({ status: 0 }, target, {
+        remoteLabel: "/sandbox/x.tgz",
+        sandboxName: "alpha",
+      }),
+    ).toThrow(/reported success \(exit 0\) but '.*' is not a regular file/);
+  });
+
+  it("rejects exit 0 with an empty file when requireNonEmpty is set", () => {
+    const target = path.join(dir, "empty.tgz");
+    fs.writeFileSync(target, "");
+    expect(() =>
+      assertDownloadedFile({ status: 0 }, target, {
+        remoteLabel: "/sandbox/x.tgz",
+        sandboxName: "alpha",
+        requireNonEmpty: true,
+      }),
+    ).toThrow(/reported success \(exit 0\) but wrote an empty file/);
+  });
+
+  it("allows an empty file when requireNonEmpty is not set (per-session files)", () => {
+    const target = path.join(dir, "session.jsonl");
+    fs.writeFileSync(target, "");
+    expect(() =>
+      assertDownloadedFile({ status: 0 }, target, {
+        remoteLabel: "/sandbox/.openclaw/agents/main/sessions/session.jsonl",
+        sandboxName: "alpha",
+      }),
+    ).not.toThrow();
+  });
+});

src/lib/actions/sandbox/sessions/download-verify.ts

@@ -0,0 +1,77 @@
+// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+import fs from "node:fs";
+
+export interface DownloadOutcome {
+  status: number | null;
+}
+
+export interface VerifyDownloadedFileOptions {
+  /** Sandbox-side source label used in error messages (e.g. the remote path). */
+  remoteLabel: string;
+  /** Sandbox name used in error messages. */
+  sandboxName: string;
+  /**
+   * Require the artifact to be non-empty. Set for a bundle that is never
+   * legitimately empty (a gzip tarball of at least one file); leave off for
+   * individual session files and for the hermes export, whose size we do not
+   * want to constrain (a zero-session hermes export can be legitimately empty).
+   */
+  requireNonEmpty?: boolean;
+}
+
+/**
+ * Confirm that an `openshell sandbox download` of a single file both reported
+ * success AND actually produced the artifact on the host.
+ *
+ * The exit status alone cannot be trusted: `openshell sandbox download` has a
+ * process-exit race that can report success (exit 0) even when the transfer
+ * was rejected or failed and no file was written (NVIDIA/OpenShell; NemoClaw
+ * #7367). Trusting exit 0 alone would let a rejected or partial download be
+ * recorded as a valid session bundle, so re-check the outcome against the file
+ * system before treating the download as complete.
+ *
+ * `hostPath` must be a path that did not exist before the download — a fresh
+ * per-export staging path, published to its real destination only after this
+ * check passes. The check can only establish that SOMETHING exists at
+ * `hostPath`; run against a reused destination it would accept a stale
+ * artifact left by an earlier export and mask the exit-0/no-write race it
+ * exists to catch.
+ *
+ * @throws if the download reported a non-zero status, wrote no file, wrote a
+ * non-regular file, or (when `requireNonEmpty`) wrote an empty file.
+ */
+export function assertDownloadedFile(
+  download: DownloadOutcome,
+  hostPath: string,
+  options: VerifyDownloadedFileOptions,
+): void {
+  const { remoteLabel, sandboxName, requireNonEmpty = false } = options;
+  const prefix = `Failed to download '${remoteLabel}' from sandbox '${sandboxName}'`;
+
+  if (download.status !== 0) {
+    throw new Error(`${prefix} (exit ${download.status}).`);
+  }
+
+  let stat: fs.Stats;
+  try {
+    stat = fs.statSync(hostPath);
+  } catch {
+    throw new Error(
+      `${prefix}: openshell reported success (exit 0) but no file was written to '${hostPath}'.`,
+    );
+  }
+
+  if (!stat.isFile()) {
+    throw new Error(
+      `${prefix}: openshell reported success (exit 0) but '${hostPath}' is not a regular file.`,
+    );
+  }
+
+  if (requireNonEmpty && stat.size === 0) {
+    throw new Error(
+      `${prefix}: openshell reported success (exit 0) but wrote an empty file to '${hostPath}'.`,
+    );
+  }
+}