"what do we do with this part?" Not committing: "I don't have enough info, don't know". Decision: "We can only finish it once X is known. Until then we assume

"what do we do with this part?" Not committing: "I don't have enough info, don't know". Decision: "We can only finish it once X is known. Until then we assume it behaves like (…). For code that relies on it, we're prioritising flexibility to change over perfect solution at this point. Y is responsible for announcing when X is known."