EffectKey

One external effect, the identity its replay evidence is kept under (design §4.24): the SHA-256 of the thread that performs it, a base key - the tool call's IdempotencyKey or the task's RunContext.taskKey - the operation (the kind of effect, such as file.edit) and a discriminator naming what it touches (a path, sorted source ids). Effects of one task differ in operation or discriminator, so they never suppress one another; a fork's re-run of its source's call is a new effect, because the thread is part of the key.

Built only by RunContext.effectKey and ToolContext.effectKey. value is the identity; operation stays readable so that refusals can name it. scope names the thread that performs the effect, without revealing it (the SHA-256 of its id): a Transactional target fences its keys per scope, because a thread's claim tokens only grow (AppliedKeys).