You're going to want to wait until it's done, and then wait another week or so before cold crashing.
Even after the bulk of fermentation is finished, the yeast are still working. After the fermentable sugars are gone, the yeast then begin to digest their own waste products like diacetyl. That works best if you allow the yeast to finish up at fermentation temperature. After that, you can cold crash if you want. Yeast still in suspension will flocculate out and give you a clearer beer, and haze-inducing proteins will fall out too, given enough time.
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