It's the current value when a dependency triggers reevaluation, but it's undefined, right, when you reevaluate the code of the cell itself? I think that caught me off guard/still catches me off guard.

Yup, it's the previously computed value. From what I understand, when you hit play, the whole Variable gets deleted and reinstantiated. That part is likely hidden somewhere in Observable's UI logic, but for the rest: 1. Variable._value is initialized as undefined (see https://github.com/observablehq/runtime/blob/9d4866/src/variable.js#L30) 2. last computed value is always passed as context (see https://github.com/observablehq/runtime/blob/9d4866/src/runtime.js#L231). 3. computation of the new value then happens inside a Promise (see https://github.com/observablehq/runtime/blob/9d4866/src/runtime.js#L246)

I've been thinking: What strategies exist to "reset" a stateful cell (aside from rerunning the code)? As far as I'm aware, when a cell recycles its previous value, there is no way to force a complete revert from the outside. Correct?