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Sierra

What Sierra does

Sierra (sierra.ai) builds an enterprise “customer-experience agent” platform designed for deploying and continuously improving AI agents that handle customer interactions across business systems and channels. The company positions its platform—"Agent OS"—as the underlying system that lets customer experience teams (and developers) move from conversation-based experiences to end-to-end outcomes, with an emphasis on reliability, testing/quality controls, and observability for ongoing improvement. Sierra’s products include tools aimed at building agents (including “agent-building” workflows) and tools aimed at analyzing agent performance over time so teams can diagnose issues and iterate quickly.

Sierra targets large, regulated enterprises and customer service organizations that need higher-assurance agent behavior (e.g., safety, governance, and compliance controls) rather than one-off chat experiences. Its customer stories emphasize production deployments in support, member services, and sales operations, and Sierra’s public posts also highlight expansion to voice and integrations that connect agents to business outcomes (for example, linking to external systems and enabling actions beyond answering questions).

News

Company record

Aug 14, 2026 · Official · Sierra (author page: Clay Bavor)Sierra opens an office in Munich (Germany, Austria, Switzerland)

Sierra announced an office opening in Munich to serve companies across Germany, Austria, and Switzerland.

Aug 07, 2026 · Official · Sierra (author page: Clay Bavor)Sierra launches Voice Personas

Sierra announced Voice Personas, describing the ability to design both what an agent does and how it expresses itself for voice experiences.

Aug 03, 2026 · Official · Sierra (author page: Clay Bavor)Plaid and Sierra partner to move AI agents from conversations to business outcomes

Sierra announced a partnership with Plaid, describing secure in-agent bank-account connectivity through Plaid as part of enabling business-outcome actions.

Jun 10, 2026 · Official · Sierra (author page: Bret Taylor)Sierra is certified FedRAMP High

Sierra announced it was certified FedRAMP High for cloud companies working with U.S. federal agencies.

May 04, 2026 · Official · SierraSierra raises $950M at a valuation of over $15B

Sierra announced raising $950 million led by Tiger Global and GV, describing use of capital to invest in its platform and expansion.

Apr 23, 2026 · Official · Sierra (author page: Bret Taylor)Sierra acquires Fragment in France

Sierra announced the acquisition of Paris-based Fragment, described as helping businesses scale operations using AI.

Apr 01, 2026 · Official · SierraEric Eyken-Sluyters joins Sierra as President of Field Operations

Sierra announced Eric Eyken-Sluyters joining to lead global Sales, Sales Engineering, and Partnerships teams.

Apr 01, 2026 · Official · SierraSierra launches Explorer as an “agent-optimizing agent”

Sierra described Explorer as a continuous, analytics-based agent that analyzes background conversation performance and recommends what to improve.

Show 4 earlier updates
Mar 27, 2026 · Official · Sierra (author page: Bret Taylor)Sierra acquires Opera Tech in Japan

Sierra announced the acquisition of Opera Tech, described as a Tokyo-based enterprise AI startup.

Mar 25, 2026 · Official · Sierra (author page: Bret Taylor)Sierra releases Ghostwriter as “Agents as a Service”

Sierra announced Ghostwriter as an agent-building agent for creating and optimizing other agents and described it as enabling production-ready customer experiences.

Sep 04, 2025 · Official · SierraSierra raises $350M at a $10B valuation (additional capital)

Sierra announced an additional $350M raise led by Greenoaks at a $10B valuation.

Date not disclosed · Official · Sierra customer storyCarMax teams with Sierra to enhance inbound sales call experience

CarMax announced it is working with Sierra on voice-enabled AI agents for inbound sales call experiences, including faster routing and smoother transitions to associates.

Source map · 2 recurring channels · 16 references

Still resolving: Newsroom · Official X

Funding

Latest disclosed valuation$15B
Tracked capital$1.7B5 sourced rounds
DateRoundRaisedValuationLead / investorsEvidence
May 04, 2026Series E (as reported by press; company blog announcement)$950M$15B
Sep 04, 2025Funding round (additional capital)$350M$10B
Oct 28, 2024Funding round$175M$4.5B
Feb 19, 2024Initial funding / launch funding reported as $110M total$110M$1B
Not attributed
+2 investors
Feb 13, 2024Seed / launch round (reported)$110M$1B

What it builds

Agent OS

Sierra’s platform intended to support both no-code and programmatic development of customer-experience AI agents and to power deployment and continuous improvement.

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Agent Studio

A product for enabling customer experience teams to build and manage agents without writing code, including configuring knowledge and brand guidelines.

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Ghostwriter

An “agent-building” tool designed to create and optimize other customer-experience agents, described by Sierra as enabling teams to build and refine agents by prompting rather than clicking or coding.

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Explorer

An “agent-optimizing” capability designed to analyze customer conversations and surface what is happening, why it is happening, and what to improve in the agent experience.

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Horizon

A Sierra capability positioned around “long-horizon” agent interactions that can orchestrate outbound and inbound interactions over days or weeks rather than only single conversations.

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Context Engine

A Sierra platform component referenced in Sierra’s product navigation, described as part of the agent system for providing contextual capabilities.

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Voice (and Voice Personas)

Sierra describes voice agents for customer assistance, and “Voice Personas” as a way to design how an agent expresses itself for voice experiences.

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Live Assist

A Sierra product described as providing AI “superpowers” for live support interactions, including real-time guidance and one-click AI-assisted responses/actions for improved service consistency.

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Trust Center / Trust and reliability

Sierra’s trust and reliability positioning, which Sierra links as a product area in its navigation and trust center positioning (governance, security, and compliance claims are described via its trust materials).

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Milestones & partnerships