Speechmatics Flow
https://www.speechmatics.com/voice-agents
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. As of 2026-10 the Flow pages and docs redirect to Agent STT, a speech-to-text API for voice agents (Linden model, from $0.30/hour) used via LiveKit, Pipecat or the API; Flow itself is no longer listed.
Deprecated · Verified 2026-10-29 · fresh as of 2026-10-29 · 43 cited facts, 1 with a third-party source · 1 recorded change · Suggest a correction
At a glance
- Tier
- T2
- Section
- Voice agent platforms
- Latest release
- not applicable — not OSS fix
- License
- not applicable — not OSS fix
- GitHub
- github.com/speechmatics (SDKs) repo fix
- Pricing
- Enterprise / per-minute vendor fix
- Funding
- $62M Series B (2022, Susquehanna) third-party fix
- Freshness
- 2026-10-29 fix
- Layer
- agent-infra repo fix
- Licensing
- commercial vendor fix
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
Alternatives to Speechmatics Flow → live options ranked by shared design, licence, hosting and MCP support
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.
- LiveKit Agents T1
LiveKit Agents — agent framework built on LiveKit's open-source WebRTC media server. LiveKit raised $45M Series B Sep-2024 ($300M val). Powers OpenAI Realtime API's WebRTC transport (LiveKit is the substrate OpenAI chose). Agents framework formally launched 2024.
- ElevenLabs Conversational AI (now ElevenAgents) 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. As of 2026-10 ElevenLabs markets the platform as ElevenAgents.
- OpenAI Realtime API T1
OpenAI's Realtime API for native speech-to-speech multimodal interaction with GPT-4o — launched Oct 2024 (DevDay). Skips the STT → LLM → TTS pipeline by passing speech directly to GPT-4o. The platform substrate that Vapi/Retell/Bland integrate as one of their LLM choices.
- Pipecat (Daily) T1
Open-source Python framework for real-time voice + multimodal AI agents, maintained by Daily.co. Pipeline-style architecture (STT → context → LLM → TTS) wired over WebRTC. The OSS substrate that many of the voice platforms build on or compose with.
- Hume EVI T1
Hume's Empathic Voice Interface (EVI) — voice agent platform with vocal-affect understanding, using Hume's proprietary speech-prosody models. Hume will shut down the EVI and TTS APIs on 2026-11-13 (announced in its docs). Hume raised $50M Series B Mar-2024 (EQT).
Sources (42 cited facts, 1 third-party)
Each fact links to the page it came from; the badge says who published it (how to read sources).
- What it is Conversational voice-agent platform (Speechmatics) vendor
- What it does & what's distinct Speechmatics (UK; STT leader) launched Flow Q4 2024 — conversational voice-agent platfor… vendor
- Claims / benefits Speechmatics STT leader (50+ languages); Flow launched Q4 2024; SOC 2 + GDPR vendor
- Modalities voice (STT/TTS) + text vendor
- Created 2024-Q4 vendor
- GitHub github.com/speechmatics (SDKs) repo
- Mindshare Strong UK / EU enterprise mindshare; media customers vendor
- Funding $62M Series B (2022, Susquehanna) third-party
- Customers / scale BBC, Microsoft, vidispine; broad media + enterprise vendor
- Pricing Enterprise / per-minute vendor
- Compliance SOC 2; ISO 27001; GDPR; EU data residency vendor
- Data handling EU / US residency vendor
- Deployment Cloud + on-prem / private cloud vendor
- HQ UK (Cambridge) vendor
- Founders / pedigree Tony Robinson + co-founders (Cambridge spinout) vendor
- Performance Sub-1s vendor benchmark vendor
- API surface REST + WebSocket; SDKs vendor
- Latency p50/p99 Sub-1s claimed vendor
- Backend storage Cloud or on-prem; caller-controlled in on-prem vendor
- Multi-tenancy Multi-tenant cloud + dedicated vendor
- Encryption TLS + AES-256 vendor
- SSO / RBAC SSO on Enterprise vendor
- Versioning Configs versioned in console vendor
- Tombstoning User-delete; GDPR DSR vendor
- Namespace primitives per-org / per-key vendor
- Forgetting policy Configurable retention vendor
- Webhooks / events Webhooks supported vendor
- Import / export Configs exportable vendor
- Validated verticals media, broadcasting, government, customer support vendor
- Time to running <1hr (sign-up + integration) vendor
- Anti-fit Enterprise-sales motion; not a self-serve developer-platform path like Vapi vendor
- Optimised for Enterprise + government voice agents with on-prem / EU residency vendor
- Adjacent infrastructure Speechmatics STT; caller-side LLM + TTS vendor
- Pros Best-in-class STT (50+ languages); on-prem option; UK/EU residency; ISO 27001. vendor
- Cons Enterprise-sales motion; less developer-friendly than Vapi/Retell; Flow is new (Q4 2024). vendor
- Project & sources speechmatics.com/flow; docs.speechmatics.com vendor
- cost-pricing-model subscription vendor
- cost-last-verified 2026-06-29 vendor
- architecture-deployment-locus cloud vendor
- licensing-bucket commercial vendor
- positioning-platform-vs-product platform vendor
- taxonomy-three-layer-rollup agent-infra repo
What changed
Changes to this record's lifecycle, licence, release, pricing and hosting facts, from the catalog's git history. Subscribe (Atom)
- 2026-10-29
- Homepage “https://www.speechmatics.com/flow” → “https://www.speechmatics.com/voice-agents”
- Lifecycle first recorded as “superseded”
Related systems
Referenced by (3)
- LiveKit Agents integrates with — LiveKit Agents docs have a Speechmatics Flow model plugin page. (verified 2026-10-29)
- Pipecat (Daily) integrates with — Pipecat docs have a Speechmatics Flow service page. (verified 2026-10-29)
- Vapi integrates with — Vapi docs list Speechmatics Flow as a provider/integration. (verified 2026-10-29)