Cartesia as Default Speech Layer

This makes Cartesia a picks and shovels supplier to the voice agent boom, not just a vendor to a handful of app companies. When Vapi and Retell make Cartesia the default speech layer, Cartesia gets pulled into every scheduler, sales bot, and support agent their customers launch. That creates a B2B2B distribution loop where one platform integration can compound into many usage based revenue streams without Cartesia selling each account directly.

• Vapi sits one layer above the speech models. It orchestrates transcription, the LLM, and voice generation, and charges a per minute platform fee on top of underlying provider costs. In that setup, the default TTS choice matters because many developers accept the preconfigured stack and ship faster.
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• Cartesia is using those partners as a distribution channel alongside direct enterprise sales. The model is similar to infrastructure getting embedded inside another developer platform, where downstream customer usage becomes the real monetization engine. That is why integrations with Vapi, Retell, LiveKit, and Together AI matter disproportionally to headcount.
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• The tradeoff is that these platforms also support multiple voice vendors and fallback routing. As Cartesia expands from Sonic into Ink and Line, it is no longer just a component supplier. It is moving toward the orchestration layer, which can push partners to multi source more aggressively or shift traffic to rivals like Rime, ElevenLabs, or in house systems.
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The next phase is a race to own more of the stack. If Cartesia keeps winning the default slot inside orchestration platforms while also moving upmarket with Line for enterprise deployments, it can turn a commodity TTS position into control over voice infrastructure budgets. The companies that hold defaults today will shape where voice agent traffic, margin, and product power accumulate tomorrow.