What is the Saltline game?
Saltline is a compact first-person shooter that runs entirely in a web browser. On November 9, 2026, the day Anthropic released Claude Fable 5.2, Anthropic engineer Felix Rieseberg posted it on Xas a test of the new model. He asked for a small FPS with graphics that could keep up with AAA games, gave no further feedback, and let the model run. About eight hours later he had a playable game. By his account the models, textures and sounds were all made from scratch by the model.
The setting is Saltline Terminal, a rain-soaked container port at dusk, full of cranes, stacked boxes and wet asphalt that reflects the sodium lights. The title screen sums up the job in one line: the port's security net has gone feral, so cut its three uplinks and reach the boat. You carry a rifle with a red-dot sight and a sidearm. Players and reporters describe two kinds of enemy, which the game calls Gulls and Hounds.
How to play the Saltline game
- Open the game. Press Play Saltline above. It opens the official Claude artifact in a new tab. You do not need a Claude account.
- Wait for first light. The loading screen reads "Waiting for first light" while the game generates the port in your browser. Expect 30 to 90 seconds on the first load.
- Pick a mode. Mission is the story run: cut three relays and reach the boat in about five minutes. Holdout is the endless mode: waves keep coming, each bigger than the last, and your best score is saved in your browser.
- Pick a difficulty. Standard, Hard or Brutal. Hard was preselected when we opened it; switch to Standard if you mainly want to see the level.
- Press Deploy. Click into the game to lock the mouse, then follow the objective to each relay and press E to cut it.
The full route, tips for each difficulty and fixes for loading problems are on the Saltline walkthrough page.
Saltline game controls
| Action | Keyboard + mouse | Controller |
|---|---|---|
| Move | W A S D | Left stick |
| Look | Mouse | Right stick |
| Fire | Left mouse button | RT |
| Aim down sights | Right mouse button | LT |
| Reload | R | X |
| Cut relay | E | X |
| Switch to sidearm | Q | Y |
| Jump | Space | On-screen on touch |
| Sprint | Shift | Not listed |
| Crouch | C | Not listed |
| Pause | Esc | Not listed |
On a phone or tablet, the left thumb moves, the right thumb looks, and fire, aim, reload and jump are on-screen buttons. All bindings above come from the game's own title screen.
Why the Saltline game went viral
Browser games made by AI are not new. Saltline stood out for three reasons. First, the look: wet surfaces, volumetric light through the cranes and rain streaks that many players compared to a modern Call of Duty map. Second, the claim: one short prompt, no human feedback, every asset generated by the model. Third, the receipt. Felix shared the numbers, roughly 2.7 million output tokens and 445 million input tokens, about $550 at API prices, over about eight hours. We break those numbers down on how Saltline was made, and the prompt itself is on the Saltline prompt page.
Not everyone was convinced. Critics argued that 445 million input tokens means a long autonomous session rather than a one-shot answer, and that a level with no human enemies is an easier target than a full campaign. Some players hit freezes and stutter. Those are fair points, and they are also why the game is worth trying yourself: it takes five minutes and you can judge the result on your own hardware.
Two versions: one-shot and improved
The game you open today is not exactly the one that went viral. A note from Felix on the title screen explains that people were impressed with the one-shotted version, but he wanted to fix the weapon models, sounds and some gameplay, so he spent about two more hours improving it. If you want to see what Fable 5.2 produced with no human feedback at all, the same note has a button that opens the original: you can also play the one-shot version directly. Playing both back to back is the quickest way to see what the extra two hours changed.
Saltline game timeline
- November 9, 2026: Anthropic releases Claude Fable 5.2. Felix Rieseberg posts Saltline on X with the prompt, the eight-hour run time and the reported $550 bill.
- November 10, 2026: The post passes 400,000 views and a reposted clip passes 650,000. Tech and gaming sites start covering the game.
- After launch: Felix adds an improved version with better weapons and sound, and keeps the one-shot version one click away.
Not the Saltline mobile game
There is an unrelated mobile game called SALTLINE: one island, one war, an air combat game for iPhone and Android. This site covers the browser FPS made with Claude Fable 5.2, not that game. If you came here looking for the mobile shooter, search the App Store or Google Play for its full name.