Bret Taylor

@thygesen_allan @claybavor Allan, thank you so much for our partnership

@btaylor Congrats, @btaylor and @claybavor . Excited to be working with you.

Sierra is raising $950 million from new and existing investors, led by Tiger Global and GV, at a valuation of over $15 billion. We now have more than $1 billion to invest in becoming the global standard for companies wanting to transform their customer experiences with AI.  We’ve never had such conviction in the opportunity for Sierra and our customers. Just a couple of years ago, we had four design partners. Now, Sierra is serving over 40% of the Fortune 50, and agents built on our platform are powering billions of customer interactions — everything from refinancing homes to processing insurance claims, returning orders, and helping people raise millions in fundraisers. We’re deeply grateful to our customers for helping show what’s possible. If you’re not yet using Sierra, we’d love to partner with you. sierra.ai/blog/better-cu…

@mikebid Thank you for your partnership!

@btaylor Congrats @btaylor and Sierra team! As a customer, love what you’ve built and rooting for you all

The Sierra research team has contributed many of the leading industry benchmarks for agents grounded in our ambition to have the most robust and sophisticated agents in customer experience. 𝜏-voice is our new benchmark for real-time voice agents. 𝜏-voice measures 278 grounded customer service tasks across retail, airline, and telecom. It pairs deterministic, end-to-end task scoring with realistic, controllable audio across diverse personas, environmental noise, and free-form turn-taking. sierra.ai/blog/tau-voice…

1. We believe in iterative deployment; although GPT-5.5 is already a smart model, we expect rapid improvements. Iterative deployment is a big part of our safety strategy; we believe the world will be best equipped to win at the team sport of AI resilience this way. 2. We believe in democratization. We want people to be able to use lots of AI; we aim to have the most efficient models, the most efficient inference stack, and the most compute. We want our users to have access to the best technology and for everyone to have equal opportunity. We have been tracking cybersecurity as a preparedness category for a long time, and have built mitigations we believe in that enable us to make capable models broadly available. 3. We love you and we want you to win. We want to be a platform for every company, scientist, entrepreneur, and person. (My whole career has largely been about the magic of startups, and I think we are about to see that magic at hyperscale.)

Introducing GPT-5.5 A new class of intelligence for real work and powering agents, built to understand complex goals, use tools, check its work, and carry more tasks through to completion. It marks a new way of getting computer work done. Now available in ChatGPT and Codex.

We're excited to announce that Sierra has acquired Paris-based Fragment, which helps businesses scale their operations using AI. Fragment's cofounders are passionate about building better, more human customer experiences with AI, and bring valuable strength to our agent development efforts in France.

As coding agents have become the standard for developing software, we've transformed Sierra's engineering interview process to be AI-native. We've documented our lessons here, and very curious how others in the industry are navigating sierra.ai/blog/the-ai-na…

Introducing μ-Bench, an open multilingual transcription benchmark. At Sierra, we benchmark 79 locale variants across 42 languages and 13+ providers. Today, we're open-sourcing a subset of that evaluation as μ-Bench, which we hope will help labs improve real world transcription quality sierra.ai/blog/mu-bench-…

I had a great time speaking with Brian Roberts at Comcast headquarters in Philadelphia about the future of AI and Comcast's partnership with Sierra. I particularly loved learning more about Comcast's early bets on the Internet and the parallels to the adoption of AI.

Introducing GPT-Rosalind, our frontier reasoning model built to support research across biology, drug discovery, and translational medicine.

We’re expanding Trusted Access for Cyber with additional tiers for authenticated cybersecurity defenders. Customers in the highest tiers can request access to GPT-5.4-Cyber, a version of GPT-5.4 fine-tuned for cybersecurity use cases, enabling more advanced defensive workflows. openai.com/index/scaling-…

Modern Animal uses Sierra to help pet owners in those anxious moments that matter — when our best furry friends are in needs — instantly and empathetically ❤️

Alzheimer’s is one of medicine's hardest unsolved problems, and one of the most devastating. At the OpenAI Foundation, we believe AI is well suited to its complexity. We're directing over $100M to scientists mapping the disease, designing drugs, & more. I wrote about it here: openaifoundation.org/news/ai-for-al…

Here’s a demo of a healthcare payment phone call with the new PCI compliant payments functionality in Sierra

In a first for the conversational AI industry, Sierra agents are now Level 1 PCI compliant, which means your agent can collect card and ACH payments securely, directly in the conversation. This is a huge step forward for subscription businesses and commerce sierra.ai/blog/payments

Meet Linneaus and Darwin: Sierra’s search models that drive higher resolution rates sierra.ai/blog/meet-linn…

Liftoff. The Artemis II mission launched from @NASAKennedy at 6:35pm ET (2235 UTC), propelling four astronauts on a journey around the Moon. Artemis II will pave the way for future Moon landings, as well as the next giant leap — astronauts on Mars.

Full blog post: sierra.ai/blog/explorer

Another week, another agent. Explorer is Sierra's agent-optimizing agent. Think of of it like ChatGPT deep research, but instead of doing research on the Internet, it's doing research over your customer conversations