Cartesia Sonic vs ElevenLabs Conversational AI (now ElevenAgents)
Cartesia Sonic vs ElevenLabs Conversational AI (now ElevenAgents): side-by-side comparison of two voice agent platforms systems — architecture, taxonomy, license, pricing, MCP/A2A support, and direct edges.
Cartesia Sonic · ElevenLabs Conversational AI (now ElevenAgents)
Cost & capability
| Cartesia Sonic | ElevenLabs Conversational AI (now ElevenAgents) | |
|---|---|---|
| Capability band | competent | competent |
| Capability composite | 58 | 62 |
| Cost tier | mid | — |
| Use cases | Latency Sensitive, Scoped Agentic | Latency Sensitive, Scoped Agentic |
Where they differ (12)
Rows where both sides have data and the values disagree — the shortlist of dimensions that actually distinguish these two systems.
| Cartesia Sonic | ElevenLabs Conversational AI (now ElevenAgents) | |
|---|---|---|
| Capability composite | 58 | 62 |
| Type | Real-time TTS + voice-agent platform (Cartesia) | Voice-agent platform from a TTS-first vendor (ElevenLabs) |
| Created | 2024 (founded) | 2024-11 (launch) |
| GitHub | github.com/cartesia-ai (SDKs) | github.com/elevenlabs (SDKs only) |
| Pricing | Free (20K credits/mo); Pro $5/mo; Startup $49/mo; Scale $299/mo; Enterprise custom; managed voice agents $0.06/min | Per-minute usage (Conv AI tier); free + Pro + Enterprise |
| Funding | $64M Series A Q1-2025 (Index + Lightspeed) | $180M Series C Jan-2025 (a16z + ICONIQ; $3.3B val) |
| Backend storage | Stateless API; caller manages state | Conversation state in ElevenLabs cloud |
| Deployment | Both (self-hosted + managed cloud) — managed API; on-prem (incl. air-gapped), customer VPC and OEM under enterprise contract | Cloud-managed |
| API surface | REST + WebSocket APIs + Python/JS SDKs | REST + WebSocket APIs + SDKs (Python, JS, Swift, Android) |
| MCP | yes — official Cartesia MCP server (cartesia-ai/cartesia-mcp) | yes — hosted ElevenLabs MCP server (recommended); local elevenlabs-mcp server deprecated/archived 2026-08-20 |
| Optimised for | Lowest-latency TTS substrate for voice agents | Natural-sounding multilingual voice agents leveraging ElevenLabs TTS |
| Anti-fit | TTS-led platform — not turnkey for full call orchestration (use with Vapi/Pipecat/LiveKit) | TTS-led — strongest at voice naturalness, less specialised for high-volume telephony routing |
At a glance
| Cartesia Sonic | ElevenLabs Conversational AI (now ElevenAgents) | |
|---|---|---|
| Section | Voice agent platforms | Voice agent platforms |
| Tier | T1 | T1 |
| Type | Real-time TTS + voice-agent platform (Cartesia) | Voice-agent platform from a TTS-first vendor (ElevenLabs) |
| Created | 2024 (founded) | 2024-11 (launch) |
| Latest release | Sonic-3.6 (current model; release date not stated) | — |
| GitHub | github.com/cartesia-ai (SDKs) | github.com/elevenlabs (SDKs only) |
| Pricing | Free (20K credits/mo); Pro $5/mo; Startup $49/mo; Scale $299/mo; Enterprise custom; managed voice agents $0.06/min | Per-minute usage (Conv AI tier); free + Pro + Enterprise |
| Funding | $64M Series A Q1-2025 (Index + Lightspeed) | $180M Series C Jan-2025 (a16z + ICONIQ; $3.3B val) |
| Backend storage | Stateless API; caller manages state | Conversation state in ElevenLabs cloud |
| Deployment | Both (self-hosted + managed cloud) — managed API; on-prem (incl. air-gapped), customer VPC and OEM under enterprise contract | Cloud-managed |
| API surface | REST + WebSocket APIs + Python/JS SDKs | REST + WebSocket APIs + SDKs (Python, JS, Swift, Android) |
| Multi-tenancy | Multi-tenant Cloud | Multi-tenant cloud |
| MCP | yes — official Cartesia MCP server (cartesia-ai/cartesia-mcp) | yes — hosted ElevenLabs MCP server (recommended); local elevenlabs-mcp server deprecated/archived 2026-08-20 |
| A2A | searched not found | searched not found |
| OpenTelemetry | searched not found | searched not found |
| Optimised for | Lowest-latency TTS substrate for voice agents | Natural-sounding multilingual voice agents leveraging ElevenLabs TTS |
| Anti-fit | TTS-led platform — not turnkey for full call orchestration (use with Vapi/Pipecat/LiveKit) | TTS-led — strongest at voice naturalness, less specialised for high-volume telephony routing |
Pros & cons
Cartesia Sonic
Pros: Lowest-latency TTS in market; Mamba-author founders; $64M Series A; SOC 2.
Cons: TTS-only at platform layer — needs orchestrator; SSM voice quality polarising vs Eleven.
ElevenLabs Conversational AI (now ElevenAgents)
Pros: Best-in-class TTS; $3.3B val parent; SOC 2 + HIPAA; multilingual 30+ languages.
Cons: Newer entrant in agent platform (Nov 2024 launch); strongest at TTS, less mature at full orchestration.