The open-source alternatives to Retell AI are Pipecat, LiveKit Agents, TEN Framework and Bolna. Retell's product is phone-call automation, so telephony is the test: Pipecat ships serialisers for Twilio, Telnyx, Plivo, Vonage, Exotel and Genesys; LiveKit Agents uses LiveKit's open-source SIP service; TEN has a SIP extension with a Twilio example; Bolna runs on Twilio or Plivo. Pipecat and LiveKit Agents carry plain open licences. TEN is source available with conditions from Agora. A team switches when it wants to choose every model in the call and keep the recordings on its own systems.
3 of 4 carry an OSI licence. 4 of 4 run on your own machines. Figures read from GitHub on October 26, 2026.
One project per need, with the reason from its own README and the one thing to know before you choose it.
BSD-2-Clause, maintained by Daily. Over twenty speech-to-text and language providers, over thirty voices including local Whisper, Ollama, Kokoro and Piper, and telephony serialisers for Twilio, Telnyx, Plivo, Vonage, Exotel and Genesys.
Know firstInterruption handling is not described beyond voice activity detection, and every provider is its own account and bill.
Apache-2.0. Semantic turn detection, native MCP tool support, a built-in test framework, and a media server plus SIP service that are open source too, so the entire path can run on your machines.
Know firstBeyond console testing it needs a LiveKit server, cloud or self-hosted, and the turn-detection models carry a separate model licence.
A visual designer, a SIP extension with a Twilio example, turn detection, and avatar extensions, run with Docker Compose.
Know firstSource available, not open source: Apache-2.0 plus Agora conditions that forbid competing deployments, and the quick start requires an Agora account.
MIT. Define the agent in a file, start four containers, and take calls on Twilio or Plivo with language models routed through LiteLLM.
Know firstThe README says the maintainers are looking for help and that maintenance has fluctuated with their time.
The facts that decide most choices. Each project's page carries the full panel.
| Project | Best for | Openness | Licence | Runs as | Own machines | Stars |
|---|---|---|---|---|---|---|
| Pipecat | The widest provider and carrier list | OSI | BSD-2-Clause | pip, CLI | Yes | 16,834 |
| LiveKit Agents | The whole stack on your own servers | OSI | Apache-2.0 | pip (Python), npm (the separate AgentsJS repository) | Yes | 14,943 |
| TEN Framework | A visual designer, if Agora fits | Source available | See LICENSE | Docker Compose, GitHub Codespaces | Yes | 11,201 |
| Bolna | A phone agent from a JSON file | OSI | MIT | Docker Compose, Python library | Yes | 803 |
Licence and star figures read from GitHub on October 26, 2026. Stars are shown as a dated fact and were not used to rank this page.
A Python framework under BSD-2-Clause, maintained by Daily, for real-time voice and multimodal agents, with the widest provider list on this site and telephony serialisers for Twilio, Telnyx, Plivo, Vonage, Exotel and Genesys.
BSD-2-Clause, maintained by Daily. Over twenty speech-to-text and language providers, over thirty voices including local Whisper, Ollama, Kokoro and Piper, and telephony serialisers for Twilio, Telnyx, Plivo, Vonage, Exotel and Genesys.
Know firstInterruption handling is not described beyond voice activity detection, and every provider is its own account and bill.
An Apache-2.0 framework for real-time voice agents that connects any speech, language and voice provider, with semantic turn detection, native MCP tool support, a test framework, and an open-source media and SIP stack it can run on entirely.
Apache-2.0. Semantic turn detection, native MCP tool support, a built-in test framework, and a media server plus SIP service that are open source too, so the entire path can run on your machines.
Know firstBeyond console testing it needs a LiveKit server, cloud or self-hosted, and the turn-detection models carry a separate model licence.
A real-time conversational AI framework from Agora with a visual designer, a SIP extension and turn detection, released under Apache-2.0 plus conditions that forbid competing deployments, which makes it source available rather than open source.
A visual designer, a SIP extension with a Twilio example, turn detection, and avatar extensions, run with Docker Compose.
Know firstSource available, not open source: Apache-2.0 plus Agora conditions that forbid competing deployments, and the quick start requires an Agora account.
An MIT voice-agent platform that defines an agent in a JSON file and orchestrates speech to text, a language model and text to speech over websockets, with Twilio and Plivo for phone calls, whose maintainers say they are looking for help.
MIT. Define the agent in a file, start four containers, and take calls on Twilio or Plivo with language models routed through LiteLLM.
Know firstThe README says the maintainers are looking for help and that maintenance has fluctuated with their time.
The questions that settle it, in the order they usually come up.
Pipecat covers Twilio, Telnyx, Plivo, Vonage, Exotel and Genesys. Bolna covers Twilio and Plivo. LiveKit brings its own SIP service. TEN has a SIP extension.
Everything including the media server: LiveKit Agents. The pipeline only, with a transport of your choice: Pipecat. A quick start in four containers: Bolna.
LiveKit Agents describes semantic turn detection. TEN has a turn-detection extension. Pipecat and Bolna's READMEs do not describe it beyond voice activity detection.
Retell AI, in the vendor's own words, is an "AI voice agent platform for automating phone calls" to "build, deploy, and manage" voice agents that execute tasks, by its own description. retellai.com. The cases below are where that still wins.
Stars, licence, last commit and last release are read from the GitHub API by a script every week and carry the date they were read. Nobody types them.
What each project does is written from its own README and LICENSE, read in full on the date shown, and phrased as the project's claim. The sources are listed at the end.
That a project is faster, better or cheaper than Retell AI. A price for anyone. A user count. A roadmap. If a fact is not on this page, it was not in the source.
Pipecat (BSD-2-Clause) has the widest carrier support on this page, with serialisers for Twilio, Telnyx, Plivo, Vonage, Exotel and Genesys and a CLI that scaffolds a phone bot. LiveKit Agents (Apache-2.0) pairs with LiveKit's open-source SIP service so the whole path can run on your own servers. Bolna (MIT) is built around Twilio and Plivo specifically.
LiveKit Agents says yes: the framework, the media server and the SIP service are all open source, though the phone number itself still comes from a carrier. Pipecat runs locally and connects to a carrier through a serialiser. TEN's documented setup depends on Agora's real-time service. Bolna needs a Twilio or Plivo account and ngrok.
Pipecat's CLI creates a phone or web bot from a template, and Bolna defines an agent in a JSON file and starts four containers with one command. LiveKit Agents has a console mode that needs no external servers for a first test. TEN uses Docker Compose and a visual designer.
LiveKit Agents describes semantic turn detection that uses a transformer model to reduce interruptions. TEN's ecosystem lists a turn-detection extension. Pipecat lists voice activity detection through Silero VAD. Bolna's README does not describe interruption handling.
Its licence is Apache-2.0 with additional conditions from Agora: you may not host it on end-user devices, and you may not deploy it in a way that competes with Agora's offerings or enables others to. That is a field-of-use restriction, so this page labels TEN source available rather than open source. Its packages directory is plain Apache-2.0.
Reveneau sets up the replacement on your own servers, connects it to your product, and builds the software around it.