Speechmatics Flow
https://www.speechmatics.com/flow
Speechmatics (UK; STT leader) launched Flow Q4 2024 — conversational voice-agent platform composed on Speechmatics STT + caller LLM. Speechmatics raised $62M Series B (2022); enterprise + media customers. UK / EU data-residency lead.
At a glance
- Type
- Conversational voice-agent platform (Speechmatics)
- Tier
- T2
- Section
- Voice agent platforms
- Created
- 2024-Q4
- Latest release
- not applicable — not OSS
- License
- not applicable — not OSS
- Pricing
- Enterprise / per-minute
- Funding
- $62M Series B (2022, Susquehanna)
Taxonomy
- storage
- kv
- retrieval
- injection
- persistence
- session
- update
- agent-controlled
- unit
- turn
- governance
- opaque
- conflict
- stateless
When to use
Optimised for: Enterprise + government voice agents with on-prem / EU residency
Anti-fit: Enterprise-sales motion; not a self-serve developer-platform path like Vapi
Pros & cons
Pros
Best-in-class STT (50+ languages); on-prem option; UK/EU residency; ISO 27001.
Cons
Enterprise-sales motion; less developer-friendly than Vapi/Retell; Flow is new (Q4 2024).
Claims & capabilities
Speechmatics STT leader (50+ languages); Flow launched Q4 2024; SOC 2 + GDPR
Technical surface
- API surface
- REST + WebSocket; SDKs
- Backend storage
- Cloud or on-prem; caller-controlled in on-prem
- Deployment
- Cloud + on-prem / private cloud
- Embedding model
- not applicable — not a memory product
- Multi-tenancy
- Multi-tenant cloud + dedicated
- MCP
- searched not found
- A2A
- searched not found
- OpenTelemetry
- searched not found
Similar systems
Other voice agent platforms in the catalog, ranked by inbound references.
- Cartesia Sonic T1
Cartesia's Sonic TTS — state-space-model-based voice generation, lowest published TTS latency (~40ms). Cartesia raised $64M Series A Q1 2025 (Index + Lightspeed); founded by Mamba authors. Agent platform layer ('Cartesia Line') wraps Sonic with telephony + LLM.
- Vapi T1
Voice-AI developer platform — STT + LLM + TTS pipelines wired to telephony (Twilio / SIP). Used to build outbound + inbound phone agents at scale. Raised $20M Series A from Bessemer + Y Combinator (Dec 2024) at $130M valuation; revenue reported >$10M ARR by Q1 2025.
- Bland AI T1
Voice-AI platform with custom STT + LLM + TTS stack ('the whole pipeline'). Raised $40M Series A Apr-2024 (Lightspeed + Anthology). Distinguished by 'pathway' graphs (deterministic call flows) and aggressive outbound-calling positioning.
- CallRail Conversation Intelligence T2
CallRail's AI-driven conversation intelligence layer atop their call-tracking product. Marketing-vertical voice analytics — auto-tagging, sentiment, lead scoring. CallRail is profitable / private (Sageview-backed); not a voice-agent runtime but the BI / analytics adjacent layer.
- ElevenLabs Conversational AI T1
ElevenLabs launched Conversational AI Nov-2024 — STT + LLM + their own market-leading TTS in one pipeline. Combines vendor's voice cloning + multilingual TTS strengths with hosted call orchestration. ElevenLabs raised $180M Series C Jan-2025 at $3.3B val.
- Hume EVI T1
Hume's Empathic Voice Interface (EVI) — voice agent platform with vocal-affect understanding. Hume raised $50M Series B Mar-2024 (EQT). Distinguished from pure LLM voice agents by emotion/prosody modelling; uses Hume's proprietary speech-prosody models.