> Despite their size, I'd be surprised if Google or Amazon had uncommitted chunks of Anthropic-scale, top-tier AI compute sitting around waiting to be activated.

I doubt it was idle capacity. But for a chunk of equity in Anthropic I imagine they are willing to deprioritize other, possibly internal, uses. Certainly anything that's not contractually obligated could be on the chopping block.

When people are moving from other models (e.g. GPT, Gemini, etc) the compute that is previously powering that inference now becomes available. Of course, I'm certainly doubtful that Google would break commits and give OpenAI GPUs to Anthropic, but the underlying effect is present and probably sorted out somehow. It's not completely net new compute for the world.