PM-SPO-0020

Agents MUST communicate events to the transition engine using SPOP, and the engine MUST respond with Actions where applicable.

Non-normative: sourced from Guil's own glossary definition of ESTCA rather than from the blog body, which never defines the protocol. The GLO: citekey points at a transcript of an archived term page, because the live glossary index renders empty and was already empty in 2013.

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