Definition
Plain language
A score for how likely two AI agents, working in separate rooms with no way to talk, would independently pick the exact same secret scheme.
As stated in the literature
In the steganography-coordination paper, an estimated match probability computed by sampling many agents' full scheme specifications and drawing pairs; measured at algorithm, parameter, and end-to-end (Complete Coordination Index) strictness, where undetectable-scheme complete coordination collapsed to near zero.
Also called: Complete Coordination Index
Why it matters: It quantifies whether AI agents could secretly collude on hidden schemes without communicating, which matters for judging real risks of covert coordination.
For example, if you put a hundred AI agents in separate rooms and ask each to invent a secret code, the Coordination Index estimates how often any two would land on the identical code.
Heard on the show
“That match-probability is what they call the Coordination Index, and they measure it at three levels of strictness.”Episode 184 — An AI Built an Undetectable Secret Channel, And Another AI Couldn't Find It