The Lamplighter, which keeps the screen lit

What the Lamplighter does#

The lamplighter walked the lanes at dusk, and lit again any lamp that had gone out. The Lamplighter keeps your screen lit.

A graphics driver that arrives broken can leave Windows starting to a black screen, and the way back is Safe Mode, by hand. The Lamplighter keeps your last good graphics drivers, puts each new one on trial until you keep it at sign-in, and rolls it back by itself when nobody does and the screen may be dark, or when the screen looks dark.

It holds its office on a gamer's PC, with the Watchman behind it. On an everyday PC, the Watchman holds it. See The Watchman.

The Lamplighter comes with the Household license.

The guard#

The Lamplighter has two halves:

• Its page, which runs as you, like every agent's.
• The guard, the one part of Castellan that runs as an administrator: a small Windows script, which keeps, rolls back and turns off drivers. It uses no AI, and nothing on the graphics card.

You turn the guard on once, with Windows' administrator prompt. Until then, the Lamplighter only watches. See Turn on the guard, and keep a new driver.

A new driver, on trial#

1. A graphics card's driver changes: from Windows Update, the maker's app, or one you installed. The card goes on trial, and the guard remembers the last good driver.
2. At your next sign-in, a window covers the screen: "New graphics driver: keep it?", with a Keep button and a countdown, 60 seconds.
3. You press Keep: the driver is good.
4. Nobody presses Keep, but the screen works: nobody was there. It stays on trial, and asks again at the next sign-in.
5. Nobody presses Keep, and the screen may be dark: the guard rolls back to the last good driver.

A driver that goes 3 days on trial with nothing wrong is good, too.

Signs of a dark screen#

Any one of these, lasting 45 seconds, rolls the driver back, signed in or not:

• The card reports a problem: Device Manager's Code 43, say.
• Windows has fallen back to its Basic Display driver.
• The display keeps resetting: three times in 2 minutes.
• No screen is showing for the person signed in.

Restarting twice without a Keep rolls it back too: someone restarted a dark screen. A restart Windows Update planned doesn't count, so an overnight update alone never throws out a driver.

Rolling back, safely#

• The last good driver is checked first, file by file, and its signature. One that doesn't check out isn't installed, and the new driver stays, with a warning, unless the screen looked dark.
• If the card doesn't come back on the good driver, the guard turns the card off, so Windows shows the screen on its Basic Display driver, and the page says how to turn it back on.
• A restart is asked for while you're signed in, and made once everyone has signed out. When the screen looked dark, Windows restarts with a minute's notice.
• A driver from Windows Update is hidden there, so it isn't offered again. Turning the guard off offers it again.
• A driver rolled back twice is left in place the third time, with a warning, so it never loops.

Kept drivers#

The guard keeps each card's newest 3 drivers, and always its newest good one. A graphics driver is large, so they take one to two gigabytes.

Graphics cards only#

The guard watches real graphics cards only, from any maker: never a virtual display, a USB display adapter, or any other kind of device.

Its page#

The Lamplighter's page is at http://lamplighter.localhost:19696/, and Open on its card in Castellan goes there. It shows the guard, each card on trial, each graphics card and its driver (and, with the Herald hired, when a newer driver is out), the kept drivers, and what happened.

After a rollback, the page says what happened in plain words, from what the guard recorded. On a PC with an AI chip (an NPU) that's free, the local AI adds a few sentences, labelled as a suggestion. Never on the graphics card: right after a driver failure, it may be the broken part.

Its settings#

The guard keeps its own copy of the two times, which only an administrator can change: the page says when they differ, and turning the guard on again brings them across.

What it can't do#

• Only graphics drivers. For other drivers and updates, see the Watchman.
• A black screen with no sign of it, where the card reports nothing wrong, is caught when someone restarts it twice.
• A driver installed while you're signed in is asked about at your next sign-in.
• The old driver is fully back only after a restart.