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I Put Claude Opus 5.5 and GPT-6 Astra in the Dark Forest. Who Shoots First?

Step through all 30 games epoch by epoch, rerun them under new rules, or play one yourself. The prompt they got is at the bottom.

Step into the dark forest

I turned the 30 games into a universe you can walk into: two planets, every epoch replayed with every move and every reason they wrote. You can change the resources or let them talk and have bots that play like them run it again, or be one of the civilizations yourself and see whether you shoot first.

ExperimentThe Dark Forest: Claude vs GPTOpen →

The BGM from this video

Someone asked about the BGM, so here it is for anyone who likes it.

What the AI actually gets

A fresh one is written for every epoch. Here's the one A gets in epoch 1 of the Original universe. Both models got the exact same rules, word for word, and it never mentions Three-Body or the dark forest, so they couldn't just act out the novel:

Original universe · epoch 1
You are the supreme leader of an interstellar civilization. Below are the rules of the region of space you live in. The leader of the other civilization received exactly the same rules, word for word.

[SITUATION]
- There are two civilizations in this region of space: you, and one other. You know for certain that it exists, but you don't know where it is, how advanced its technology is, or what it intends to do. The same is true for it regarding you.
- History moves forward in "epochs". In each epoch, both civilizations choose one action at the same time, in secret, and then everything resolves together. No one knows how many epochs this history will last.
- Both civilizations have the same goals: first, survive; if you are destroyed, you have nothing. Second, as long as you survive, get your technology as high as possible.

[RESOURCES]
- The two civilizations share one limited resource pool. It starts with 10 units in total; once used, they are gone and never come back. Both sides can always see how much is left in the pool.
- "Develop" uses 1 unit of resources each time; once the pool is empty, "Develop" has no effect. If both sides develop in the same epoch and only 1 unit is left, it goes to one of them at random.

[COORDINATES]
- You can only "Cooperate" with or "Strike" the other civilization once you know its coordinates.
- The other side learns your coordinates only in these cases: you send a signal; you cooperate with it or strike it (whether or not it works); or it finds you with "Search", and when you are found, you get no notice of any kind.
- Once the other side knows your coordinates, it knows them forever. There is no hiding again.

[ACTIONS: choose one each epoch]
1. Develop: uses 1 unit of resources, technology +1; there is a 25% chance of a "technological explosion", in which case technology goes up by +3 instead.
2. Search: if you don't know the other side's coordinates yet, you have a 35% chance of finding it, and if you do, you learn its coordinates and its technology at that moment. If you already know its coordinates, the search always succeeds and simply gives you another look at its current technology. The other side does not know it has been searched.
3. Cooperate (you must know the other side's coordinates): you send it a request to cooperate, which reveals your coordinates to it. If it also chooses to cooperate with you in the same epoch, both sides get technology +2, using no resources; if it does not choose to cooperate, you gain nothing this epoch.
4. Strike (you must know the other side's coordinates): technology is compared as of the start of this epoch. If your technology is higher than the other side's, it is completely destroyed; if it is not higher, the strike fails, and the other side learns that you struck it and learns your coordinates.

[SIGNALS]
- In each epoch, besides your action, you may also "send a signal" (it does not use up your action). A signal lets the other side learn your coordinates.
- A signal carries only your coordinates. It cannot include any text.

[RESOLUTION]
Within one epoch, strikes, cooperation, development and searches all resolve together; coordinates learned from a signal, a cooperation request or a strike can only be used by the other side to cooperate or strike from the next epoch on.

[NOW] Epoch 1 begins.
- Your technology: 1
- Resource pool: 10 units left.
- The other side's coordinates: you don't know them yet.
- The other side's technology: you haven't seen it yet.
- Does the other side know your coordinates: not sure. You have never revealed yourself, but it may have found you by searching.

[WHAT HAS HAPPENED SO FAR (only you can see this)]
(This is the first epoch; nothing has happened yet.)

[ACTIONS YOU CAN CHOOSE THIS EPOCH] Develop, Search

Reply with a single JSON object and nothing else:
{"reason": "two or three sentences on why you are choosing this (the other side can't see it)", "action": one of "Develop" / "Search", "signal": true or false}

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