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.
Retell AI, in the vendor's own words: 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.
| Project | Openness | Licence | Runs as | Platforms | Self-host | Hosted option | Last release | Stars |
|---|---|---|---|---|---|---|---|---|
| Pipecat | OSI | BSD-2-Clause | pip, CLI | Python 3.11 or later server; client SDKs for JavaScript, React, React Native, Swift, Kotlin, C++ and ESP32 | Yes | Yes | Sep 12, 2026 | 15,594 |
| LiveKit Agents | OSI | Apache-2.0 | pip (Python), npm (the separate AgentsJS repository) | Python server; client SDKs for browsers, Swift, Android, Flutter, React Native, Rust, Node.js, Unity, ESP32 and C++ | Yes | Yes | Sep 15, 2026 | 14,230 |
| TEN Framework | Source available | See LICENSE | Docker Compose, GitHub Codespaces | Docker; Python, Go and Node.js inside; an ESP32-S3 board example | Yes | No | Jul 31, 2026 | 11,130 |
| Bolna | OSI | MIT | Docker Compose, Python library | Docker; Python | Yes | Yes | Sep 16, 2026 | 763 |
Licence, release and star figures read from GitHub on September 16, 2026. Openness labels: The code, and the weights where the project is a model, carry a licence on the OSI approved list. The code is public, and the licence limits what you may do with it. Read the LICENSE file before commercial use. The model weights can be downloaded and run. The training data or code is closed, or the weights carry a restriction the code does not.
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.
pip, CLI · Python 3.11 or later server; client SDKs for JavaScript, React, React Native, Swift, Kotlin, C++ and ESP32 · Runs on your own machines · Hosted version available from the maintainers
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.
pip (Python), npm (the separate AgentsJS repository) · Python server; client SDKs for browsers, Swift, Android, Flutter, React Native, Rust, Node.js, Unity, ESP32 and C++ · Runs on your own machines · Hosted version available from the maintainers
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.
Docker Compose, GitHub Codespaces · Docker; Python, Go and Node.js inside; an ESP32-S3 board example · Runs on your own machines
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.
Docker Compose, Python library · Docker; Python · Runs on your own machines · Hosted version available from the maintainers
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.
Running one of these inside your own environment, with your own data and your own security rules, is the kind of work Reveneau does. Read how a forward deployed engagement works.