Amazon announced an additional $4 billion investment in Anthropic, bringing its total to $8 billion while remaining a minority investor. AWS became not just Anthropic's primary cloud provider but its primary training partner, with Anthropic working alongside AWS's Annapurna Labs to optimize Trainium accelerators — down to writing low-level kernels and contributing to the AWS Neuron software stack — in what both framed as an integrated stack from silicon to software. Claude's use through Amazon Bedrock had also spread, with Pfizer, Intuit, Perplexity, and the European Parliament named among customers.