Releases

Sierra published the first draft of Personal Agent Protocol, code-named Poppy, and added 35 companies to the protocol's design process.

Sierra launched fleming-1, a real-time audio model that scores callers' speech for signs it was generated by AI and can be enabled on Sierra voice agents.

A third-party company tracker listed 53 open roles at Sierra.

Sierra and Meta, with partners including Shopify, Stripe, Walmart, Genesys, Instinct and Rocket, announced the Personal Agent Protocol, an open standard for how personal AI agents authenticate and act with businesses (read/write permissions, visibility into agent actions). A v0.1 spec is planned for later in October 2026.

Sierra expanded Ghostwriter into Slack and Microsoft Teams as an always-on, proactive and asynchronous teammate.

Sierra added agents that can move between voice, text and interactive visuals in one conversation and deploy the same experience across channels.

Sierra released hyper-τ-bench, a long-horizon evaluation in which developer agents recover requirements, build customer-service agents in sandboxes and are scored on held-out tasks.

Sierra launched Voice Personas so companies can design how an agent expresses a distinct brand personality.

Sierra announced the acquisition of Takeoff, a three-person long-horizon-agent company approaching an eight-figure annual run rate, with the teams combining to build Horizon.

Sierra launched long-horizon agents that orchestrate inbound and outbound interactions over days or weeks using persistent context and planning.

Sierra reported serving more than 40% of the Fortune 50, with agents on its platform powering billions of customer interactions.

Sierra raised $950 million from new and existing investors led by Tiger Global and GV.

Revelio Labs estimated Sierra's workforce at approximately 756 employees in the first quarter of 2026.

Sierra introduced an agent that creates, executes and continuously improves other customer-experience agents from described outcomes.

Sierra reported more than $150 million in annual recurring revenue as it entered its third year.

Sierra announced that it reached $100 million in annual recurring revenue seven quarters after its public launch.

Sierra launched Agent Data Platform to provide agents with memory, context and intelligence across interactions.

Sierra unveiled Agent OS 2.0, expanding agents from answering questions toward persistent memory, cross-channel action and customer relationships.

Sierra launched Agent Studio 2.0 with more powerful journeys, integrations and release-management capabilities available through a collaborative interface.

Sierra launched a no-code environment that enables customer experience teams to build and manage AI agents.

Sierra reported hundreds of customers across financial services, healthcare, telecommunications, retail and consumer services.

Sierra raised $350 million in additional capital led by Greenoaks to expand Agent OS and its international business.

Sierra launched full-duplex voice capabilities for customer-facing AI agents.

Sierra publicly launched its enterprise platform for building customer-facing AI agents.