In the fourth quarter Microsoft’s Anthropic investment produced a $3.2 billion gain while its OpenAI position was marked down by roughly $600 million, against a $5 billion gain on that same OpenAI position for the full year. Two frontier lab stakes, held by one company, moving $3.8 billion in opposite directions inside ninety days. There is no operating business inside Microsoft that swings that hard that fast, which makes the other income line the most volatile input in the model and the least analyzed.