diff --git a/TESTING.md b/TESTING.md
index f43da6d4..648ef497 100644
--- a/TESTING.md
+++ b/TESTING.md
@@ -86,6 +86,18 @@ timer that "usually" covers a frame is a race on a loaded runner. Library
 virtualization specs settle with `libraryObservation.settled()` (two consecutive
 frames with no Library frame queued). To look for such races, repeat a spec under
 load (`--workers 8 --repeat-each 10`, and in the image with `--cpus=1` or `2`).
+CPU limits do not reproduce disk-bound timeouts (backup, restore). For those,
+throttle writes in the image: with rootful Docker on a host with cgroup v2, add
+`--device-write-iops /dev/<disk>:20` to the `docker run`, where `<disk>` is the
+whole disk (not a partition) holding Docker's data root, because the test server
+keeps its database in the container's `/tmp`. On a plain partition,
+`lsblk -no pkname "$(df --output=source "$(docker info -f '{{.DockerRootDir}}')" | tail -1)"`
+prints it; on LVM or LUKS, `lsblk -s` walks down to the disk. A spec that waits
+on a timer then fails at its 5 s expect. A spec that waits on the response can
+still fail at the 30 s test timeout when several workers share the throttled
+disk; that means the disk is too slow for the test budget, not that the spec is
+wrong.
+
 On unsupported Linux
 distributions, browser system dependencies may need manual installation. For a
 quick browser run, use `test:workflows -- --project chromium`.
diff --git a/tests/browser/workflows.spec.mjs b/tests/browser/workflows.spec.mjs
index a3007d54..6ae6d971 100644
--- a/tests/browser/workflows.spec.mjs
+++ b/tests/browser/workflows.spec.mjs
@@ -257,6 +257,18 @@ async function chooseRestore(page, file) {
     await page.locator('#restoreFileInput').setInputFiles(file);
 }
 
+// Confirms the chosen restore and waits for the server's answer, not for a timer: a restore is disk-bound and can take
+// longer than an expect timeout on a slow runner (#359). The modal closes only after that answer.
+async function confirmRestoreAndWait(page) {
+    const restored = page.waitForResponse(response => response.url().endsWith('/prompt_manager/restore'));
+    await page.locator('#confirmRestore').click();
+    const response = await restored;
+    const body = await response.text();
+    expect(response.status(), body).toBe(200);
+    expect(JSON.parse(body)).toMatchObject({ success: true, prompt_count: 2, backup_created: expect.any(String) });
+    await expect(page.locator('#restoreModal')).toBeHidden();
+}
+
 function confirmNextDialog(page, accept, message) {
     page.once('dialog', async dialog => {
         expect(dialog.type()).toBe('confirm');
@@ -287,12 +299,7 @@ test('downloaded backup restores deleted prompts, tags, and image links through
     expect(await promptSnapshot(request)).not.toEqual(before);
     await chooseRestore(page, backup);
     confirmNextDialog(page, true, backup.name);
-    const restored = page.waitForResponse(response => response.url().endsWith('/prompt_manager/restore'));
-    await page.locator('#confirmRestore').click();
-    const response = await restored;
-    expect(response.ok()).toBe(true);
-    expect(await response.json()).toMatchObject({ success: true, prompt_count: 2, backup_created: expect.any(String) });
-    await expect(page.locator('#restoreModal')).toBeHidden();
+    await confirmRestoreAndWait(page);
     await expect(page.locator('.prompt-text')).toHaveCount(2);
     await page.reload();
     await expect(page.locator('.prompt-text').filter({ hasText: 'Cat portrait' })).toBeVisible();
@@ -335,8 +342,7 @@ test('restore validation and cancellation preserve live data and allow a valid r
     expect(await promptSnapshot(request)).toEqual(before);
     await page.locator('#restoreFileInput').setInputFiles(backup);
     confirmNextDialog(page, true, backup.name);
-    await page.locator('#confirmRestore').click();
-    await expect(page.locator('#restoreModal')).toBeHidden();
+    await confirmRestoreAndWait(page);
     expect(await promptSnapshot(request)).toEqual(before);
 });
 
@@ -356,8 +362,7 @@ test('backup and restore recover from interrupted network requests without losin
     await expect(page.locator('#restoreModal')).toBeVisible();
     expect(await promptSnapshot(request)).toEqual(before);
     confirmNextDialog(page, true, backup.name);
-    await page.locator('#confirmRestore').click();
-    await expect(page.locator('#restoreModal')).toBeHidden();
+    await confirmRestoreAndWait(page);
     expect(await promptSnapshot(request)).toEqual(before);
 });