Inworld, an AI research lab and inference provider based in Mountain View, California, said on October 1, 2026, that it had acquired Ultravox, a Seattle platform developers use to build voice agents that talk with users in real time. The deal was announced through Business Wire.
The companies did not disclose the price or other terms. GeekWire also reported the deal as being for an undisclosed sum.
Members of the Ultravox team who have joined Inworld will keep developing the platform, Inworld said. GeekWire noted it was unclear whether the whole team made the move. For existing Ultravox customers, all built-in Inworld voices were upgraded to Inworld's Realtime TTS-2 speech model as part of the deal.
What Ultravox built
Ultravox sells tools for building voice agents, with a focus on the mechanics of live conversation: knowing when a speaker has finished, handling interruptions and delivering a natural-sounding voice. Inworld said those capabilities help developers build agents that respond to users without awkward delays.
Those are the parts of a voice conversation where agents often stumble: talking over a user, waiting too long after the user stops, or failing to stop when interrupted. GeekWire said Inworld expects Ultravox's turn-taking and interruption technology to improve performance in real-time chats.
The company began life as Fixie, founded in 2022 by veterans of Google and Apple, and later took the Ultravox name as it concentrated on a speech model for real-time AI voice agents, according to GeekWire. Its original chief executive, Matt Welsh, left about two years ago and now leads AI systems at Palantir, GeekWire reported, while co-founder and most recent chief executive Zach Koch now lists himself as a vice president of product at Shopify.
GeekWire put Ultravox's headcount at about 10 people, based on LinkedIn.
“Ultravox has built a platform that developers rely on for real-time voice agents. We're excited to welcome members of the Ultravox team and continue building the platform. Bringing Realtime TTS-2 to the Inworld voices customers already use is the first benefit we're delivering.”
The funding
As Fixie, the company announced a $17 million seed round in March 2023 led by Redpoint Ventures. Madrona Venture Group, Zetta Venture Partners, SignalFire, Bloomberg Beta and Kearny Jackson also took part, along with current and former executives from Google, Amazon and Apple, GeekWire reported. PitchBook valued the company at about $51.5 million at the time.
No later funding rounds were reported. Inworld itself has raised $119.8 million since it launched in 2021 and is valued at $515 million, according to PitchBook figures cited by GeekWire.
Why Inworld is buying
Inworld builds its own speech models, serves large language models and runs real-time inference behind APIs used by consumer AI apps. It said the Ultravox deal speeds up its speech-to-speech research and its work on voice agents.
That positions Inworld as both a model maker and a provider of the infrastructure that runs models in production. Adding a developer platform for voice agents gives it a direct channel to companies that build those agents, rather than only selling speech models and APIs to them.
The first visible change is on the voice side. Inworld says Realtime TTS-2 is ranked first on the Artificial Analysis text-to-speech leaderboard, supports more than 200 languages with latency under 100 milliseconds, and lets developers steer pacing, tone and emotion through plain-language instructions written into the text.
Chief executive Kylan Gibbs described Ultravox as a platform developers rely on for real-time voice agents and called the voice upgrade the first benefit Inworld was delivering to its customers.
What happens to customers
Inworld said the Ultravox platform will continue, with the team members who joined it carrying on development. Customers using built-in Inworld voices inside Ultravox did not need to migrate to receive the Realtime TTS-2 upgrade.
Inworld did not say whether Ultravox's pricing, brand or own speech model would change, or how the platform would be combined with Inworld's other APIs over time.
The deal also marks the end of Ultravox as an independent company about three and a half years after its seed round. Its founding leaders had already moved on before the sale, according to GeekWire, leaving the platform's remaining staff and customers as the main assets Inworld acquired alongside the technology.
