Bret Taylor’s artificial intelligence startup Sierra has announced it is raising $950 million in a funding round led by Tiger Global and GV, pushing its post-money valuation past $15 billion. The raise gives Sierra over $1 billion in capital to work with — money the company says it will use to become the “global standard” for AI-powered customer experiences.

Like many AI companies, Sierra has been smartly proactive about highlighting its own growth in a crowded market. The company says it started with just four design partners a couple of years ago. Today, it claims that more than 40% of the Fortune 50 are customers, and that the agents running on its platform are handling billions of interactions — from refinancing mortgages and processing insurance claims to managing returns and powering nonprofit fundraising campaigns.

Indeed, the funding news follows a period of breakneck revenue growth for Sierra. The company first announced it had hit $100 million in annual recurring revenue (ARR) in late November, then published another post in early February saying it had reached $150 million in ARR. That pace reflects both the urgency enterprises feel about deploying AI and the costs that come with it.

Taylor, who also serves as chairman of OpenAI and was formerly co-CEO of Salesforce, has said that the best-case outcome for agentic AI is lower costs and higher revenue for clients. But before those returns materialize, the ramp-up phase can be expensive. Uber CTO Praveen Neppalli Naga put it plainly in conversation with this editor, saying that Uber “blew through our [AI] budget” soon after opening the door to agentic AI tools late last year. He also said the company is starting to see meaningful results. Across a staff of roughly 8,000 engineers and technical workers, about 10% of all code being produced at the company is now generated autonomously, he said, adding that “10% at our scale is huge.” As a proof-of-concept, Uber tasked one team with building a new hotel-booking integration using only agentic workflows. Work that would normally take a year was completed in six months, he said.

Sierra is also moving to expand what its platform can do beyond customer-facing agents. In April, the company launched Ghostwriter, an “agent as a service” tool designed to build other agents. Users describe what they need in natural language, and Ghostwriter autonomously creates and deploys a specialized agent to handle it. For Taylor, the tool underscores a broader thesis he laid out at the HumanX conference in San Francisco last month. Many enterprise software tools, he argued, are barely used. Employees log into Workday when they onboard and again at open enrollment, and that’s about it. The future Sierra and its investors are betting on is one where people never need to navigate complex systems at all.