What launched
ThunderPhone, a startup whose platform runs AI agents on phone and web calls, launched a third-generation architecture and an agent-building system called Zeus on Monday, the company said. Alex Kolchinski, the chief executive, and Alec Bell, the chief technology officer, founded the business in 2025 as Autophonix, LLC. It is bootstrapped and says it is profitable, though it does not disclose precise revenue.
Models run in parallel
Rather than chaining speech-to-text, language and speech-synthesis models in sequence, the v3 architecture runs many models on each call at the same time, among them several transcription models and language models, Kolchinski said. The company has retired its fixed product tiers and now assembles a model mix for each customer use case.
The benchmark figure
ThunderPhone reported a score of 99.4% on the Big Bench Audio reasoning benchmark and posted its evaluation set online. StepFun's StepAudio 3 Realtime has a higher published score of 99.7%, but according to ThunderPhone that model is too slow for live phone calls, which the company says leaves v3 as the highest-scoring model that can handle them.
Zeus and pricing
Zeus automates the model tuning that ThunderPhone engineers previously carried out by hand for every enterprise account, Kolchinski said. It builds agents from recordings, call-centre scripts or imports from Vapi, Retell, Bland and ElevenLabs, and on simulated and live calls it locates errors, tests fixes and backtests changes against past calls within spending caps the user sets.
Under the company's cost-plus pricing, customers pay underlying vendor rates plus a margin of 17% to 25%, which ThunderPhone publishes. Kolchinski said calls start at 2 cents a minute, that 5 cents is common for more complex agents, that demanding use cases run 10 to 15 cents, and that high-volume enterprise work can be priced below 1 cent a minute.
