Features, pricing, and fit
Compare Line and Ultravox on voice capabilities, pricing, and fit.
Compare Cartesia Line and Ultravox for AI phone agents, Voice AI platforms, then match channels, workflows, and deployment models to your call flow.
Managed Line runtime for voice agents with no-code Agent Builder, SDK-defined reasoning, Cartesia Ink STT, Sonic TTS, deployment, and observability.
Teams that want managed audio plumbing while retaining code-level control over reasoning, tools, and external APIs.
Explore its buying criteria: AI phone agents · Voice AI platforms.
API-first native speech-language model with a no-code Console, custom tools, and bring-your-own telephony for phone, web, and native apps.
Engineering teams that want direct speech processing and control over telephony or app transports.
Explore its buying criteria: AI phone agents · Voice AI platforms.
Both profiles checked 2026-09-04.
Use the table below to compare each provider’s documented scope.
Before you decide
Cartesia Line: Not publicly documented Ultravox: Pay-as-you-go and Pro plans combine a published per-minute rate with monthly plan fees; Enterprise is custom, and SIP is priced separately. Ask both vendors to quote the same expected workload, required channels, and implementation scope. Include required subscriptions and usage charges before comparing the total; the listed starting prices alone may cover different work.
The recorded knowledge and data sources for Cartesia Line include Not publicly documented. For Ultravox, they include Not publicly documented. Ask each provider to demonstrate access for the exact systems you use, with permissions, freshness, and failure behavior. A source missing from this directory is not proof that a provider cannot support it.
Use the same representative calls, approved instructions, and escalation rules in both pilots. How does it handle interruption and uncertainty? Which actions can it complete, and which require approval? What context reaches a human during transfer? Record conversation quality, completed tasks, human handoffs, and total cost in the buyer worksheet. Check these specific cautions before launch: Cartesia Line: Confirm product availability, carrier coverage, models, data handling, and generally available features. Ultravox: Open weights do not remove hosting, latency, safety, evaluation, voice, and telephony work. Review license and SLA.
Record your requirements and pilot results in the buyer worksheet →
Swipe or scroll the table to see every column.
| Criterion | Line | Ultravox |
|---|---|---|
| Provider type | Voice agent platform and speech API | Native speech-language model API |
| Best fit | Teams that want managed audio plumbing while retaining code-level control over reasoning, tools, and external APIs. | Engineering teams that want direct speech processing and control over telephony or app transports. |
| Key capabilities | realtime voices; agent configuration; telephony; tools; API | direct speech-language interaction; open weights; hosted API; tools; realtime sessions |
| Team sizes | startup; mid-market; enterprise; developer | startup; mid-market; enterprise; developer |
| Call surfaces | phone / PSTN; API / SDK | phone / PSTN; API / SDK |
| Voice stack | Cascaded STT-LLM-TTS using Cartesia TTS | Native speech-language model |
| Telephony | Not publicly documented | Not publicly documented |
| Call controls | Not publicly documented | Not publicly documented |
| Languages | Not publicly documented | Not publicly documented |
| Integrations | Not publicly documented | Not publicly documented |
| Knowledge and data | Not publicly documented | Not publicly documented |
| Pricing model | Not publicly documented | Pay-as-you-go and Pro plans combine a published per-minute rate with monthly plan fees; Enterprise is custom, and SIP is priced separately. |
| Pricing signal | Approximately $0.06/min plus about $0.014/min managed telephony; verify current calculator. | 30 free minutes; $0.05/min pay-as-you-go; Pro $100/month; SIP about $0.005/min. |
| Free plan or trial | Not publicly documented | 30 free minutes; open weights under published license. |
| What stands out | Line separates reasoning from audio operations: it offers a no-code builder or SDK for custom logic while managing deployment/observability and pairing Ink with Sonic. | Ultravox documents a native speech path without a separate ASR stage, then exposes both Console prototyping and REST/SDK integration with BYOT telephony. |
| Considerations | Confirm product availability, carrier coverage, models, data handling, and generally available features. | Open weights do not remove hosting, latency, safety, evaluation, voice, and telephony work. Review license and SLA. |
Teams that want managed audio plumbing while retaining code-level control over reasoning, tools, and external APIs.
Line separates reasoning from audio operations: it offers a no-code builder or SDK for custom logic while managing deployment/observability and pairing Ink with Sonic.
Engineering teams that want direct speech processing and control over telephony or app transports.
Ultravox documents a native speech path without a separate ASR stage, then exposes both Console prototyping and REST/SDK integration with BYOT telephony.
Verify current pricing, limits, security, and required integrations directly with each provider before purchasing.
Test recognition, speech quality, interruptions, language switching, tool use, and human transfer with your own calls in the required language. Availability can vary by model, plan, and phone route.
DocsBot documents multilingual voice workflows and Japanese support. Verify the exact voice, phone path, and transfer behavior in your pilot. Review DocsBot language information ↗
Other providers’ language claims reflect cited vendor material; confirm Japanese and other required languages directly with each provider.
Listing does not imply endorsement or a performance guarantee. This directory is published by DocsBot. Editorial policy
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