# Alternatives to Synthflow > Source: https://theagentsindex.com/synthflow-ai/alternatives (current datasheets, evidence-ranked) Candidates share the baseline category or are previously researched peers. Requirements, preserved strengths, explicit trade-offs and research coverage decide the order; paid tier does not. ## Shortlist ### 1. ElevenLabs Agents Hosted platform for building voice and chat agents, with telephony, SDKs and a choice of LLM. **Research coverage:** 35/35 criteria **Where it improves on Synthflow:** - [Claude: yes — Anthropic models are natively selectable in agent settings; a few older Claude models drop out in EU data-residency workspaces.](https://elevenlabs.io/docs/eleven-agents/customization/llm) - [Open models: yes — Open-weight models run two ways: ElevenLabs-hosted Qwen in the native model list, or Llama and Mixtral through a custom LLM endpoint such as Together AI, Groq or SambaNova.](https://elevenlabs.io/docs/eleven-agents/customization/llm/custom-llm/together-ai) - [Model choice: yes — You pick the model per agent, plus a backup cascade; LLM usage is billed on top of the plan and varies by model.](https://elevenlabs.io/docs/eleven-agents/customization/llm) **Trade-offs against Synthflow:** - [In your editor: no — The vendor enumerates its surfaces as web widgets, mobile apps, phone systems and custom integrations; no editor or IDE extension appears in that list.](https://elevenlabs.io/docs/eleven-agents/integrate/overview) - [Admin controls: partial — Guardrails constrain what an agent may say and per-tool approval constrains what it may do, but Guardrails is in Alpha and enabling MCP servers is not restricted to admins.](https://elevenlabs.io/docs/eleven-agents/best-practices/guardrails) - [Data residency: partial — US by default; EU, India and Singapore exist as separate Enterprise workspaces with their own accounts, API hosts and reduced model choice, and processing may still leave the region.](https://elevenlabs.io/docs/overview/administration/data-residency) [View ElevenLabs Agents](https://theagentsindex.com/elevenlabs-conversational-ai) ### 2. AudioCodes Live Hub Self-service cloud platform for building voice AI agents and connecting them to real telephony channels. **Research coverage:** 33/35 criteria **Where it improves on Synthflow:** - [Claude: partial — Claude models are supported only as bring-your-own custom models configured with your own Anthropic API key; the pre-deployed model list carries OpenAI and Google models only.](https://techdocs.audiocodes.com/livehub/Content/AI-Agents/Bring%20your%20own%20models.htm) - [Open models: partial — Open-weight models such as gpt-oss and Gemma are reachable only through the bring-your-own-model path with your own Groq, Cerebras or OpenAI keys, not from the pre-deployed set.](https://techdocs.audiocodes.com/livehub/Content/AI-Agents/Bring%20your%20own%20models.htm) - [Model choice: yes — You choose the LLM per agent from pre-deployed models or add your own provider, and you can equally bring an entirely external conversational AI platform instead.](https://techdocs.audiocodes.com/livehub/Content/AI-Agents/Bring%20your%20own%20models.htm) **Trade-offs against Synthflow:** - [Agent permissions: partial — An agent calls any tool you configured without a per-call approval step, so control is exercised up front by choosing its tools; the MCP management connection does offer an explicit read-only mode.](https://techdocs.audiocodes.com/livehub/Content/AI-Agents/Tools.htm) - [In your editor: no — There is no editor or IDE extension: authoring happens in the web portal, and the only documented developer-tool integrations are the two MCP clients named below.](https://techdocs.audiocodes.com/livehub/Content/AI-Agents/MCP%20server.htm) - [Free tier: partial — You can sign up and test without a credit card on $10 of complimentary credit, but that is a limited Trial plan that goes inactive at a zero balance rather than a standing free tier.](https://techdocs.audiocodes.com/livehub/Content/LiveHub/Account%20plans.htm) [View AudioCodes Live Hub](https://theagentsindex.com/audiocodes-live-hub) ### 3. Vapi Developer platform for building, testing and deploying voice AI agents that make and receive phone calls. **Research coverage:** 35/35 criteria **Where it improves on Synthflow:** - [Claude: yes — Claude is selectable as the assistant's LLM, on Vapi's integration or your own Anthropic account.](https://docs.vapi.ai/providers/model/anthropic) - [Open models: yes — Open-weight models reach the pipeline through Groq, Together AI, Mistral, DeepSeek and OpenRouter, or a self-hosted server.](https://vapi.ai/platform) - [Model choice: yes — You choose transcriber, LLM and voice independently and can swap any of them.](https://vapi.ai/platform) **Trade-offs against Synthflow:** - [Agent permissions: partial — Tools fire mid-call without human approval; a per-tool rejection plan is the mechanism that withholds an action.](https://docs.vapi.ai/tools/tool-rejection-plan) - [Opt out of training: partial — The privacy policy reserves call content for model training and names no toggle; the $1,000/month ZDR add-on is the only documented way to stop it being kept at all.](https://vapi.ai/privacy) - [Data residency: partial — US is the default region; the EU region is frozen to existing accounts and new EU residency is enterprise-only, so regional control comes from your own buckets and models.](https://docs.vapi.ai/security-and-privacy/data-flow) [View Vapi](https://theagentsindex.com/vapi) ### 4. PolyAI Enterprise platform for building voice and chat agents that resolve customer calls, priced per minute. **Research coverage:** 35/35 criteria **Where it improves on Synthflow:** - [Claude: yes — Claude is one of the third-party models you can run instead of Raven; the model docs list Claude options under the Amazon Bedrock provider tab, selectable per channel.](https://poly.ai/blog/agentic-dialog-platform-open-to-builders) - [Open models: partial — The model catalogue enumerates only Raven, OpenAI and Amazon Bedrock (Claude, Nova) with no open-weight option, but you can attach your own LLM endpoint.](https://docs.poly.ai/behavior/models/byom) - [Model choice: yes — You choose the model per channel in voice and chat configuration; Raven is the recommended default rather than the only option.](https://docs.poly.ai/behavior/models/model-use) **Trade-offs against Synthflow:** - [Multi-agent: no — The only 'team of agents' feature is assigning several TTS voices to one agent; no coordination between multiple agents on a single task is documented, and the build assistant works one branch at a time.](https://docs.poly.ai/voice-channel/multi-voice) - [Agent permissions: partial — Wren plans and waits for approval by default, always asks before writing to the live environment, never receives secret values, and its API discovery requests are GET-only.](https://docs.poly.ai/wren/building) - [Pooled budget: partial — Conversation volume draws on one account-level Subscription Volume of CX Tokens, but the Wren builder allowance is per person and not shared.](https://docs.poly.ai/wren/usage-and-limits) [View PolyAI](https://theagentsindex.com/polyai) ### 5. Retell AI Pay-as-you-go platform for building, testing and running AI phone, chat and SMS agents. **Research coverage:** 34/35 criteria **Where it improves on Synthflow:** - [Claude: yes — Claude models are selectable as the agent's conversation model and priced per minute for voice and per message for chat, alongside GPT and Gemini options.](https://www.retellai.com/pricing) - [Open models: partial — Retell's own model menu is limited to hosted GPT, Claude and Gemini, but the custom-LLM path lets you put a self-hosted open-weights model behind the agent over a WebSocket you operate.](https://docs.retellai.com/integrate-llm/overview) - [Model choice: yes — You pick the conversation model per agent from a published, per-minute-priced list, and you can substitute your own model entirely through the custom-LLM WebSocket.](https://docs.retellai.com/integrate-llm/overview) **Trade-offs against Synthflow:** - [Agent permissions: partial — Prohibited-topic guardrails screen both the agent's replies and user input, and tools are explicitly wired per node, but guardrails only swap in a placeholder message rather than stopping or escalating the call.](https://docs.retellai.com/build/guardrails) - [Free tier: partial — You can sign up and run real calls without talking to sales, but the free allowance is a one-off $10 trial credit per email address rather than a standing free plan.](https://docs.retellai.com/accounts/billing) - [Admin controls: partial — Admin, Developer and Member roles constrain who can edit agents, see raw transcripts or change limits, but the pricing comparison marks role-based access control as an Enterprise capability rather than a pay-as-you-go one.](https://docs.retellai.com/accounts/access-control) [View Retell AI](https://theagentsindex.com/retell-ai) ### 6. Cartesia Real-time speech models and a managed runtime for production phone and web voice agents. **Research coverage:** 35/35 criteria **Where it improves on Synthflow:** - [Claude: yes — Anthropic Claude models are named in the SDK's supported-models table and used in its examples.](https://docs.cartesia.ai/line/sdk/agents) - [Open models: partial — The LLM layer routes through LiteLLM to 100+ providers, but the vendor names only Anthropic, OpenAI and Google, and its own speech models are API-only.](https://docs.cartesia.ai/line/sdk/agents) - [Model choice: yes — You pick the agent's LLM and can swap it in the Playground or API; Cartesia owns the speech models and manages the LLM integration.](https://docs.cartesia.ai/agents/models) **Trade-offs against Synthflow:** - [Done-for-you service: no — Self-serve software: you build and deploy the agent yourself; sales contact exists for Enterprise terms, not for building it for you.](https://www.cartesia.ai/agents) - [Multi-agent: no — System tools enumerate three slots: end call, DTMF, and transfer to an E.164 phone number. An agent therefore hands off to a number, not to another Cartesia agent.](https://docs.cartesia.ai/agents/system-tools) - [Agent permissions: partial — Limits are prompt-level guardrails plus per-tool execution settings (timeout, immediate vs async, speak-before-acting); there is no separate policy engine.](https://docs.cartesia.ai/agents/configuration) [View Cartesia](https://theagentsindex.com/cartesia) ## Method Unknown data is never treated as a benefit or a trade-off. Featured placement is labelled but cannot alter recommendation order.