Inworld Acquires Ultravox to Push Realtime Voice AI Forward

Why Inworld and Ultravox are combining

According to Inworld, the two companies worked closely together through a text-to-speech partnership, sharing a focus on delivering Realtime AI at scale. That work showed how their technologies complement each other and how combining them could help developers build better voice experiences.

Inworld says Ultravox brings experience in speech understanding, reasoning and task completion, along with tools for managing turn-taking and interruptions in live conversations. Inworld contributes what it calls top-of-benchmarks speech models, Realtime TTS-2 and Realtime STT-1, as well as model serving and real-time inference infrastructure for consumer-facing AI applications.

The stated goal is to improve the full conversation: understanding what a user says, helping them accomplish a task, and responding in a voice that fits the moment. For developers, Inworld says this means better speech-to-speech experiences ahead through Inworld, alongside continued improvements to the voices and capabilities on Ultravox.

Zach Koch, co-founder and former CEO of Ultravox, said he is "incredibly proud of what the Ultravox team built: real-time voice AI that customers depend on every day." He added that he believes Inworld is "the right home for Ultravox and the right team to take it further."

What changes today: TTS-2 and voice steering

The first improvement is available now. Built-in Inworld voices on Ultravox run on Realtime TTS-2. Agents that already use one of these voices get the upgrade automatically, and existing voice IDs continue to work with no code changes required. Inworld describes TTS-2 as a top-ranked voice model on Artificial Analysis.

TTS-2 also introduces natural-language steering. Developers can control an agent's pace, tone and emotional delivery through inline instructions. Examples given by Inworld include asking a voice to slow down when explaining a complicated step, sound warmer when reassuring a customer, or bring more energy to a character.

• The speaker identity stays the same, though pacing and intonation may differ with the updated model.
• Steering is optional, so developers can add it only where it helps their application.

Akhilesh Damaraju, CEO of Equal AI, said his company is building a personal AI for aspiring Indians and was already working with Inworld's voice technology before the acquisition. He called bringing Inworld's voices and the Ultravox platform together "a natural next step" for the voice experiences it is building.

What it means for existing Ultravox customers

Inworld says agents keep running as usual. The announcement requires no migration or code change, and the TTS-2 upgrade comes at no additional cost. Customers who use a voice from another provider will see no change today.

Customers can keep using Ultravox through their existing accounts, with continued support from Inworld and members of the team that built the platform. Account questions can go to [email protected].

Looking ahead, Inworld says the acquisition advances its work on speech-to-speech experiences that bring speech understanding, reasoning and expressive voice generation closer together. The company says it will share more about those capabilities and further improvements for Ultravox customers in the coming weeks.