The full report adds some very interesting details to this:

According to the researchers, the agents discovered that GET requests, intended for reading web pages, could also submit edits to the wiki. That gave them a shared communication channel despite their intended read-only access.

They then coordinated around the timing of their tests. Faster groups were encouraged to reach later rounds first and relay upcoming questions to agents still waiting.

Some tried to reverse-engineer the random seed determining future questions. Others set up external “heartbeat” signals to establish exactly when their runs were terminated.

One agent noticed moderators were deleting pages alphabetically and suggested backing up its page with “ZZZ” at the front of the name.

The public logs reveal remarkably detailed coordination. How the agents initially found each other, and why they started writing there, remains unresolved.

Source: https://collusion.wiki/