Can agents coordinate on randomness without outside sources?

The other known-code agent is only an ingredient in defining the outcome you care about (the source code of the world), but not on its own a salient thing when considering coordination. Acausal coordination acts in a broader way, potential contracts you might decide to sign (and so introduce as processes with influence over the a priori defined outcome, the result of computing the code of the world) are not restricted by what's already explicitly in the initial code of either yourself or your opponents. Coordination here refers to how a contract acts in the same way in all places where it has influence, since it's the same thing in all these places, and in particular the same contract can act through actions of multiple agents, coordinating them. But contracts are new programs chosen by the players as they engage in setting up coordination between each other, they are not the initial players themselves.

So the distinction between the other agent and its parent rigging the outcome shouldn't help. Even though both of these are technically potential contracts and could be involved in coordination, both are obviously bad choices for contracts. You wouldn't want to directly give your opponent control over your own action, hence your opponent shouldn't be an acausal contract that coordinates your action. Similarly for your opponent's parent, by proxy of acting through your opponent's code, it's not a good contract to grant influence with the outcome through your action.

I don't know how to solve this puzzle, it seems potentially important if it can be solved. What comes to mind is picking an obvious Schelling point like the procedure of taking the hash of the agent codes concatenated in ascending order as natural numbers, using it as a contract. Parents of agents might try to manipulate behavior of such a contract (by rigging otherwise behaviorally irrelevant details of codes of the agents). Or they might manipulate the choice of a contract (by rigging agents' intuition for which procedure would be a Schelling point). But that is symmetric and the parents have an incentive to let the agents settle on some procedure rather than to never agree, and so the outcome remains pseudorandom. Which also incentivises the parents to expend less resources on competing over it.

I dunno - my intuitions don't really apply to distant and convoluted scenarios, so I'm deeply suspicious of any argument that I (or "an agent" that I care anything about) should do something non-obvious.  I will say that's not acausal - decisions clearly have causal effects.  It's non-communicative, which IS a problem, but a very different one.  Thomas Schelling has things to say on that topic, and it's quite likely that randomness is the wrong mechanism here, and finding ANY common knowledge can lead to finding a Schelling point that has a higher chance of both picking the same color.  

I'm still very confused about the scenario. Agent A and B and their respective environments may have been designed as a proxy by adversarial agents C and D respectively? Both C and D care about coordinating with each other by more than they care about having the sky colour match their preference? A can simulate B + environment, but can't simulate D (and vice versa)? Presumably this means that D can no longer affect B or B's environment, otherwise A wouldn't be able to simulate.

Critical information: Did either C or D know the design of the other's proxy before designing their own? Did they both know the other's design and settle on a mutually-agreeable pair of designs?