We keep a short list of default tools so that every project starts fast and every engineer can move between projects. Defaults are reviewed twice a year.
For web apps we use React with a server-rendering framework, TypeScript throughout, and PostgreSQL as the main database. Most products never need anything more exotic.
AI features run as separate services with their own logging and evaluation, so model changes do not require redeploying the product.
We change the defaults when a client already has a stack their team knows well. A codebase the client can maintain is worth more than our preferences.