Sierra
Unicorn Β· $15.8BSan Francisco, US Β· Founded 2023 Β· 989 employees on LinkedIn Β· 15 known investors
Sierra builds AI agents that handle customer service for large companies β answering questions and completing transactions in a brand's own voice across chat, voice, email and messaging, in 59 languages. It was founded in 2023 by Bret Taylor, former co-CEO of Salesforce and chair of OpenAI's board, and Clay Bavor, who spent 18 years at Google running Labs and its AR/VR effort. Sierra passed $150 million in annual recurring revenue within eight quarters and raised $950 million in May 2026 at a $15.8 billion valuation.
Also known as Sierra Technologies, Inc. Β· Sierra AI
Founders & leadership
Sierra was founded in 2023 by Bret Taylor and Clay Bavor.
Investors Β· 15
.jpeg)
Funding
SEC filings, press & company announcements$1.6B disclosed across 4 rounds Β· 2024β2026
- $950MSeries EMay 2026 Β· 5 sources
GV (lead), Tiger Global (lead), Benchmark, Greenoaks, Sequoia Capital
Source β - $350MSeries CSep 2025 Β· 3 sources
Greenoaks (lead), Greenoaks Capital (lead), Benchmark, ICONIQ Capital, Sequoia Capital, Thrive Capital
Source β - $175MSeries BOct 2024 Β· 2 sources
Greenoaks (lead), Benchmark, ICONIQ Capital, Sequoia Capital, Thrive Capital
Source β - $110MLaunch / SeedFeb 2024 Β· 2 sources
Benchmark (lead), Sequoia Capital (lead), ICONIQ Capital, Thrive Capital
Source β
Source: company announcements and press reports β follow each round's link for the claim.
Valuation Β· disclosed
Disclosed eventsSource: SEC prospectus filings, and round valuations the company or its investors disclosed β follow each entry's link for the claim.
Company profile
researched Aug 2026Sierra is a San Francisco-based conversational AI platform for enterprise customer experience. Companies use Sierra to deploy AI agents that answer customer questions and take actions in systems of record β updating CRM entries, processing returns and refunds, handling insurance claims, or originating mortgages β across chat, SMS, WhatsApp, email, voice and ChatGPT, in 59 languages and around the clock. Agents can be tuned to a company's brand voice and are supported by guardrails, testing and escalation to human staff.
The platform includes Ghostwriter, an agent-building agent that turns SOPs, transcripts, images and audio recordings or plain-language goals into a production-ready multichannel agent and automates subsequent agent updates; an Insights suite with Explorer (natural-language analysis of conversations), Monitors, Experiments and observability into tool calls, knowledge lookups and latency; and Horizon, which covers long-horizon planning, customer memory across conversations and systems, outcome optimization and proactive engagement triggered by real-world signals. Sierra describes a multi-model architecture, combining large language models from providers including OpenAI, Anthropic and Meta with its own fine-tuned layers, and cites enterprise security controls such as encryption, access controls and SOC 2.
Sierra was co-founded in 2023 by Bret Taylor and Clay Bavor and sells primarily to large enterprises in financial services, telecom, technology, healthcare, travel and retail. It says more than 40% of the Fortune 50 are customers and reported surpassing $150 million in annual recurring revenue within eight quarters.
Founding story
Bret Taylor and Clay Bavor first met while working together at Google and co-founded Sierra in 2023 to redefine AI assistance for businesses. Taylor previously served as co-CEO of Salesforce, founded Quip, was CTO of Facebook, co-created Google Maps and serves on the board of OpenAI as its chair. Bavor spent 18 years at Google, most recently leading Google Labs, and earlier started Google's AR/VR effort and Project Starline, led Google Lens and ran product and design for Google Workspace.
Business model
Sierra licenses an enterprise AI agent platform and works alongside customers as an agent-development partner, supporting deployments that it says typically launch within weeks. Pricing is described as tiered subscription plus usage, with Sierra promoting an outcome-based model in which customers pay only when the software achieves specific, valuable outcomes; specific list prices are not published.
Recurring enterprise contracts with outcome-based pricing, where charges are tied to delivered outcomes rather than seats, reportedly scaling with interaction volume, customization and integration complexity.
Traction
Sierra says it began with four design partners and now counts more than 40% of the Fortune 50 as customers, with agents on its platform handling billions of interactions spanning mortgage refinancing, insurance claims, returns and nonprofit fundraising. It reported reaching $100 million in ARR in late November and $150 million in ARR by early February, describing the $150 million milestone as achieved within eight quarters of launch.
Latest developments
Sierra closed a $950 million Series E in May 2026 at a $15.8 billion post-money valuation, led by Tiger Global and Alphabet's GV with Benchmark, Sequoia and Greenoaks participating β its second raise in eight months.
Since then the company has spent the capital on reach rather than on a single product bet. It acquired Takeoff in July 2026 and folded its team into Horizon, a platform for agents that plan and act across days or weeks instead of one conversation; shipped Voice Personas in August on the voice stack the Receptive AI acquisition brought in; announced a go-to-market partnership with Plaid so agents can act on account data rather than only discuss it; launched in Korea; and opened a European push in Germany, Austria and Switzerland. Bret Taylor has said an IPO is in Sierra's future but that it stays private for now, and has forecast an AI market correction within two years.
βΈFull profile β market position, technology, go-to-market, geography, history, risks & controversies
Market position
Positioned as a leading platform in the enterprise customer-experience AI agent category. Sierra says it serves more than 40% of the Fortune 50 and one in three of the world's largest banks, and CEO Bret Taylor has said the company is multiples larger than its next biggest competitor; Benchmark general partner Peter Fenton described Sierra as the category winner by revenue scale and customer quality. Taylor estimates roughly $400 billion is spent annually on customer service, much of which he expects to shift to AI agents. Competing vendors in enterprise CX agents include Voiceflow, which differentiates on customer-owned agent building and bring-your-own-model deployment.
Sierra emphasizes outcome-based pricing, a vendor-operated model in which its agent-development team builds and maintains agents for customers, multi-model orchestration across LLM providers, deployment of a single agent across chat, SMS, WhatsApp, email, voice and ChatGPT in 59 languages, and agents that execute transactions inside enterprise systems rather than only answering questions. Comparisons by competitor Voiceflow note the trade-off: Sierra operates the agent on the customer's behalf, whereas alternatives give customers direct control over flows, prompts and model selection.
Technology
A conversational AI platform that orchestrates multiple third-party large language models β described by the company as a "constellation of models" from providers such as OpenAI, Anthropic and Meta β with proprietary fine-tuned layers. Agents connect securely to enterprise systems of record to complete transactions end to end. Supporting tooling covers agent generation and automated updating (Ghostwriter), conversation analytics and monitoring, multivariate experiments, observability of tool calls and latency, long-horizon planning with cross-conversation memory, and evaluation benchmarks including a voice extension of its πΒ³-bench agent evaluation work.
Go-to-market
Direct enterprise sales paired with a long-term partnership model in which a Sierra agent-development team supports deployment and ongoing optimization. Marketing runs through customer case studies, webinars for healthcare, financial services and travel verticals, product demos, executive keynotes and podcast and conference appearances by its founders.
Large enterprises and Fortune 50-scale brands, concentrated in financial services and insurance, healthcare, telecom, technology, travel and hospitality, retail and consumer goods. Customers Sierra names on its own site include Rocket Mortgage, SoFi, Chime, Ramp, Kraken, Capital on Tap, Imprint, Paychex, CLEAR, Wayfair, Redfin, CarMax, Airtable, SiriusXM, Tubi, Singtel Group, SoftBank, LINE MAN Wongnai, Sutter Health, R1 RCM, Modern Animal, GoFundMe, BARK, Casper, Minted, Guild, Safelite, Homebase, Vivid Seats, ecoATM and ScottsMiracle-Gro.
Geography
Headquartered in San Francisco, with offices in New York, Atlanta, London, Singapore, Tokyo, Paris, Madrid and Toronto. Acquisitions in France and Japan extended its European and Asia-Pacific presence.
History
Founded in 2023, Sierra raised $175 million at a $4.5 billion valuation in October 2024 led by Greenoaks, followed by $350 million at a $10 billion valuation in September 2025 and a $950 million Series E in May 2026 at a $15.8 billion post-money valuation led by Tiger Global and GV.
2026 was also the year Sierra started buying: voice-agent platform Receptive AI and Japan-based Opera Tech in March, French Y Combinator alumnus Fragment in April, and long-horizon agent startup Takeoff in July. Product releases tracked the same arc β Agent OS 2.0 in November 2025, Ghostwriter and "Agents as a Service" in March 2026, the Horizon platform built out of the Takeoff team in July, and Voice Personas in August.
Risks & controversies
Sierra operates in a crowded and rapidly funded market for customer-service AI agents, and Taylor has publicly anticipated an AI market correction and a "culling effect" in which capital concentrates in market leaders. Enterprises adopting agentic AI can face significant ramp-up costs before returns materialize. Sierra's voice channel capability was added through the March 2026 acquisition of Receptive AI rather than being native at launch, and its pricing is not publicly disclosed.
Compiled by commissioned research from 17 cited public sources β announcements, filings, and press listed under research sources below.
Key figures
latest reportedCompany-reported or press-reported figures, each dated to when it was claimed β not independently audited.
Founder mafia
The Sierra mafia β7 people who came through Sierra went on to found or lead other companies.
Competitors Β· 2
by search overlap
Companies competing with Sierra for the same Google search keywords, organic and paid, via search-intersection analysis.
Customers & partners
Named customers Β· 37
Partnerships Β· 2
Relationships the company or its partners disclosed publicly β case studies, joint announcements, press.
Timeline Β· 16
launches, deals, and filingsLocalised agents and a Korean go-to-market, the company's second Asia-Pacific launch of 2026.
Configurable voice identities for Sierra's voice agents β the product line the March 2026 Receptive AI acquisition seeded.
Plaid's financial data network is wired into Sierra agents so they can complete account actions rather than only answer questions.
Sierra acquired Takeoff and said the combined teams would build Horizon, a platform for long-horizon AI agents.
The platform built out of the Takeoff acquisition: agents that plan and act across days or weeks, carrying customer memory between conversations and systems.
Sierra and SoftBank announced a partnership making SoftBank the exclusive sales channel in Japan for Sierra's conversational AI platform.
Led by Tiger Global and Alphabet's GV, with Benchmark, Sequoia and Greenoaks participating β the largest of Sierra's four rounds and its second in eight months.
$950M source β
Sierra acquired Fragment, a French Y Combinator-backed startup integrating AI into business workflows; co-founders Olivier Moindrot and Guillaume Genthial joined Sierra, expanding its European agent-development capacity.
Ghostwriter, an agent that builds agents: SOPs, transcripts or a plain-language goal become a production multichannel agent, and it handles the updates afterwards.
Sierra published an expansion of its πΒ³-bench agent evaluation benchmark to cover voice agents.
Sierra acquired Opera Tech, a Japan-based enterprise AI company, expanding its Asia-Pacific presence.
Sierra acquired voice-agent platform Receptive AI, adding native voice capability to a product that had been chat-focused at launch.
The platform release that moved Sierra's agents from answering to remembering and acting, alongside the Agent Data Platform.
Company confirmed it was raising $350 million, with Greenoaks Capital expected to lead.
$350M source β
Round led by Greenoaks Capital with participation from Thrive Capital and ICONIQ, bringing total funding to $285 million.
$175M source β
Company came out of stealth with a pitch for a conversational AI platform for businesses, alongside a $110 million seed/launch round.
Dated company events from announcements, filings, and press; legal rows summarize public dockets and regulator releases.
In the news
βΈResearch sources Β· 17
primary sources listed
- Better customer experiences. Built on SierraSierra Β· company site
- Sierrasierra.ai Β· web
17 public sources were cited for this profile; the first-party ones are listed here.
Frequently asked questions
- What does Sierra do?
- Sierra builds conversational AI agents that handle customer service and customer-experience workflows for large enterprises.
- Who founded Sierra?
- Sierra was founded by Bret Taylor, Clay Bavor in 2023.
- Who are Sierra's investors?
- Sierra's investors include Comcast Ventures, Conviction, Everybody Ventures, GV (Google Ventures), ICONIQ, Kleiner Perkins, Mech Ventures, Sequoia Capital and 7 more.
- How much funding has Sierra raised?
- Sierra has disclosed $1.6B raised across 4 rounds.
- Where is Sierra headquartered?
- Sierra is headquartered in San Francisco, US.