Synthflow review

Synthflow is a voice AI platform from AgentFlow AI GmbH in Berlin ²⁹. Its agents answer and place phone calls, and the same agent can also run over chat, SMS and WhatsApp ^11,12. You build agents without code in a node-based Flow Designer or a Prompt Builder ²⁷, and connect them to numbers bought in Synthflow, your own Twilio account or a SIP trunk from systems such as Genesys Cloud and Five9 ^27,28.

Synthflow has moved to enterprise sales. It no longer sells its Pro, Growth and Agency plans ³, and new contracts start at $30,000 a year ¹. Since August 25, 2026, non-enterprise workspaces run only on the in-house Synthflow LLM ⁶, and in-product reselling for agency partners ended on September 15, 2026 ². Synthflow raised a $20 million Series A led by Accel in June 2025, for $30 million in total funding ³⁰.

Custom actions send HTTP requests to your APIs before or during a call, so the agent can create a CRM record or check an order status and use the result in its next turn ⁸. Built-in actions book meetings, send SMS or WhatsApp messages mid-call and transfer calls ²⁷. Transfers can be cold, warm with a whisper message, or warm with an AI-written summary, and office hours, phone books or a destination fetched during the call decide where they go ⁹. Campaigns dial lists of up to 10,000 recipients per API request, inside the calling hours you allow ¹⁰.

Before launch, the Test Center generates simulated callers from your agent's setup and scores each run against success criteria ¹³. Every publish saves a version you can compare, export or restore, though changes to actions are not versioned ¹⁴. Per agent, you can stop saving recordings or transcripts, delete data after 30 days and redact PII from transcripts and logs ¹⁵. After calls, logs show transcripts and the agent version used, and the analytics dashboard tracks outcomes and sentiment ^16,17.

Synthflow lists one plan. Enterprise contracts start at $30,000 a year, about $2,500 a month, and are scoped around call volume, concurrency, telephony, integrations, security and launch support ¹. Per-minute rates, included minutes, overage and carryover are set in each agreement ^4,5. Calls are billed per second from the moment the caller and agent connect, unanswered calls count as 5 seconds, and every 5 AI chat messages count as one minute ⁵. With no public minute rate, the cost of 1,000 minutes a month cannot be worked out. The older self-serve Pro, Growth and Agency plans are no longer sold ³.

Synthflow's Trust Vault lists SOC 2 Type 2, ISO/IEC 27001, ISO/IEC 42001, HIPAA, GDPR and PCI DSS v4.0.1, with reports behind an access request ²⁰. A Business Associate Agreement is published for HIPAA customers ²³. Each workspace picks a US, EU or legacy Global cluster at creation, and US and EU keep storage and compute in one region ²¹. The Subscriber Terms state that Synthflow does not use customer input or output to train its own or any third party's AI models ²². PII redaction covers transcripts, webhooks and logs but not live audio ¹⁵. SSO through WorkOS and enforced two-factor sign-in are available, with SSO on the Enterprise plan ¹⁹. Listed sub-processors include OpenAI, ElevenLabs and Deepgram ²⁰.

Synthflow holds 4.5 stars from about 1,015 G2 reviews ³¹. Trustpilot shows 4.1 from 215 reviews, but recent reviews complain about billing after cancellation and slow support ³². Synthflow says it powers 130+ enterprises and publishes stories from Freshworks, Thryv, Smartcat, Euro Paper and Niagara Region Transit ²⁴. Through a partnership, its voice AI runs inside Freshworks' Freshcaller, Freshdesk and Freshservice ²⁵. Independent coverage centered on its $20 million Series A in 2025 ³⁰.