What the post said
- The claim: on 23 September 2026, a day after Claude Opus 5.5 came out, Jacob Sansbury posted on X: "I had 26 Opus 5.5 agents build a game overnight."
- The game: Portal Heist, a heist through five worlds that you play with friends in a browser, with no download.
- The tool: Spawn, which describes itself as "a place to make multiplayer games by talking". Its AI builder uses Claude Opus 5.5 by default, and can send helpers (the agents in the post) to work on separate parts of a game at once (Spawn's site, read 28 September 2026).
- Who posted it: Spawn's own page says the company was "founded by Jacob Sansbury", so this is a founder showing what his product can do.
The four missing facts
- How long it took. "Overnight" is the only measure given.
- What it cost, in money or in usage.
- How much a person steered. The post does not say how many instructions, corrections or restarts it took.
- The record. No log of the session was shared, so nobody outside can check the claim.
How to read a demo like this
Two things from the past six weeks are worth holding next to it.
- Anthropic's own test went badly six weeks earlier. In research published on 13 August 2026, it set groups of agents to build a text-based fantasy game, playable on the web, for 12 hours. The games "did not run at human speed, their interfaces were inscrutable, and they had precipitous learning curves". Opus 5.5 came out after the test.
- Readers are asking to see the working. In a Hacker News thread on Opus 5.5 demos, one commenter wrote that "people putting out these demos should share their sessions to really show what was going on".
The two are hard to compare, since the post does not say how much direction this game had from a person.
What you can try yourself
- Play the game. Open Portal Heist in a browser and judge the claim with your own hands. The post says it needs no download and no account.
- Make a small one on Spawn. Open spawn.co, select “make a game” and describe the game you want. Spawn says creating is free, and it may ask you to sign in first.
- Ask Claude for a tiny browser game. In a chat, ask for a simple game as an artifact, the page Claude builds beside your chat. Artifacts work on every plan, Free included (Anthropic help page, read 28 September 2026). If no page appears, turn on Cloud code execution and file creation under Settings, then Capabilities.
The honest bit
- A page loading proves little. The game's page opens and describes it. Whether it is fun, or holds up with a full room, is for you to judge by playing.
- A playable game is a real result. The post hands you the thing itself to test, which is the fairest kind of claim.
- This story is from 23 September 2026. Details may change, and the missing facts may yet be published.
A few quick questions
Can I run lots of agents in Claude or ChatGPT?
Not in an ordinary chat, where you talk to one assistant. Tools built for it, such as Spawn and Claude Code, send several helpers to work on separate parts of a job at once.
Is Spawn free to try?
Yes. Spawn's own page says creating is free, and that its AI builder is included, so you do not connect a Claude or ChatGPT account to use it.