Open source Retell AI alternatives
Every project in the catalog is MIT, Apache or BSD licensed. 0 projects explicitly describe themselves as a Retell AI alternative; 14 more are in the category where Retell AI is a typical product.
Open source projects in the same category: AI Call Agents & Telephony
Category-level information: these projects are the same kind of software as Retell AI; they have not claimed to be a one-to-one replacement.
LangChain
100langchain-ai · AI Call Agents & Telephony
Common commercial products in this category: Vapi, Bland AI, Retell AI
- You develop language model-based applications by chaining models, tools, and data sources together.
- By switching easily between different model providers, you ensure model compatibility.
- Thanks to modular component architecture, you quickly prototype and implement AI projects.
- • High number of open issues (701)
- • NeutralHacker News
Why we no longer use LangChain for building our AI agents
“I don’t think that’s fair to Llama-Index. LI is much more focused, better documented and frankly way easier to use than LangChain, with much lower - or negligible - cognitive overhead. Plus, it plays nice with most everything else. Even if you’re mostly working just with a…”
- • NeutralHacker News
Why we no longer use LangChain for building our AI agents
“I think this is another crucial part. Right now, writing prompts is kinda like writing hand-crafted assembly back in the day where that was routine because there was simply no other way to get good results out of hardware in many cases - but also because the tasks that are…”
Verified against README · Oct 26, 2026 · source
openai · AI Call Agents & Telephony
Common commercial products in this category: Vapi, Bland AI, Retell AI
- You can convert audio recordings to text
- You can translate conversations in languages other than English into English text with multilingual models.
- You can define spoken language in audio content
Verified against README · Oct 26, 2026 · source
Bark
55suno-ai · AI Call Agents & Telephony
Common commercial products in this category: Vapi, Bland AI, Retell AI
- You get multi-language speech output from text entries with automatic language detection feature
- You generate nonverbal audio communications such as laughter or sighing with text commands
- You perform sound synthesis by uploading pre-trained models in the Python environment
- • Last update 2 years ago
- • NeutralHacker News
Bark – Text-prompted generative audio model
“This tech will be used by crooks to automate attacks. Generate the language using GPT-4 and the audio using Bark, and then start making phone calls. Because it’s open source, all you need is GPUs. This is not a criticism. I’m impressed and grateful for the openness. Everyone…”
- ↓ NegativeHacker News
Bark: A transformer based text to audio system
“>Yeah I was trying to figure out how good it was in Korean. The cadence and flow was pretty good but there was kind of artifacts in the audio. Then I check the samples of the default audio prompts for Korean any my god, they were godawful. Switching it up made a world of…”
Verified against README · Oct 26, 2026 · source
SYSTRAN · AI Call Agents & Telephony
Common commercial products in this category: Vapi, Bland AI, Retell AI
- By applying 8-bit quantization on both CPU and GPU, you provide less memory consumption
- You also decrypt audio files through the PyAV Python library, without installing FFmpeg on the system.
- With word-level time stamps and a VAD filter, you write down audio files by extracting quiet sections.
- ↓ NegativeGitHub Issue
Windows process crashes when the GPU model is unloaded
“Thanks for your work first. It's useful. Howerver, there's still something wrong. It returns -1073740791 (0xC0000409) when dealing with a audio file in chinese. I have defined a function in which the variable 'result' is used to accept the 'segments' returned by the…”
- • NeutralGitHub Issue
Could not load library libcudnn_ops_infer.so.8
“` Could not load library libcudnn_ops_infer.so.8. Error: libcudnn_ops_infer.so.8: cannot open shared object file: No such file or directory ` I'm using "nvidia/cuda:12.2.0-base-ubuntu20.04" image on google cloud with nvidia t4 gpus. The normal whisper package model works fine on…”
Verified against README · Oct 26, 2026 · source
Pipecat
100pipecat-ai · AI Call Agents & Telephony
Common commercial products in this category: Vapi, Bland AI, Retell AI
- You design voice assistants that deliver fluent conversations in natural language.
- You set up multi-agent systems that are tasked or parallel to each other.
- You develop multi-mode interactive interfaces that process audio, image and text data.
- • High number of open issues (502)
- • NeutralHacker News
Show HN: Open-source customizable AI voice dictation built on Pipecat
“Hey, sorry if the examples given were not robust, but because this is built on Pipecat, you can actually very easily swap to a local LLM if you prefer that, and the project is already set up to allow you to do that via environment variables. The integration to set up the WebRTC…”
- • NeutralHacker News
Show HN: Open-source customizable AI voice dictation built on Pipecat
“Thanks for the feedback, probably should have been clearer in my original post and in the README as well. Local inference is already supported via Pipecat, you can use ollama or any custom OpenAI endpoint. Local STT is also supported via whisper, which pipecat will download and…”
F5-TTS
100SWivid · AI Call Agents & Telephony
Common commercial products in this category: Vapi, Bland AI, Retell AI
- By giving a reference audio recording and text, you convert the text from the command line or from the Gradio interface into that voice speech.
- By cloning the local source code, you can perform model training and fine-tuning.
- Using Docker, you can run the application in a container environment.
Verified against README · Oct 25, 2026 · source
livekit · AI Call Agents & Telephony
Common commercial products in this category: Vapi, Bland AI, Retell AI
- By combining different model providers, you can develop speech-based voice agents.
- You can connect users to agents using built-in business timing and distribution API.
- With phone stack integration, you can make or receive phone calls.
- • High number of open issues (885)
Silero VAD
100snakers4 · AI Call Agents & Telephony
Common commercial products in this category: Vapi, Bland AI, Retell AI
- Using Python and pips, you can integrate speech in audio files into your project to search for time.
- By calling the model via the PyTorch Hub, you can process audio data and get speech times in seconds.
- Using ONNX Runtime, you can customize and execute audio I/O operations in different system architectures.
- • NeutralGitHub Issue
[CHANGELOG] v6.2 just released!
“Just a handy issue to be notified of latest changes and micro-releases (we will mostly changing the models)”
- • NeutralGitHub Issue
[FORMATS] Most important export formats?
“As everybody knows, the VAD now exists as an ONNX model (`onnx-runtime`) and as a `jit` (PyTorch TorchScript) model. Can you please shorlist the remaining most important export formats, i.e. TF, OpenVINO, etc? We need some data / votes to make a shortlist. To make it simpler - I…”
Kokoro
55hexgrad · AI Call Agents & Telephony
Common commercial products in this category: Vapi, Bland AI, Retell AI
- You include the library in your project using Pip
- Run with basic or advanced code blocks on Google Colab
- You convert text into sound using different language codes
- • Last update over 1 year ago
- • NeutralHacker News
Local, CPU-Friendly, High-Quality TTS (Text-to-Speech) with Kokoro
“Kokoro voices were the non-human actors directed by Opus, featured in the sound performance "God Bless the United States of Aliens". A theatrical adaptation of a liturgical texts, a surveilled mass ceremony at a protesting Christian church, being exhibited at the 61st Venice…”
- ↑ PositiveHacker News
Local, CPU-Friendly, High-Quality TTS (Text-to-Speech) with Kokoro
“I love Kokoro. I use it to read ebooks that don't have audiobooks and it works pretty good for that. I have a Python script that reads epub/html, runs the model and writes mp3s. Kokoro supports a limited number of languages. I've had to resort to other models to support Dutch,…”
Ultravox
69fixie-ai · AI Call Agents & Telephony
Common commercial products in this category: Vapi, Bland AI, Retell AI
- Develop AI applications that do not require a separate voice recognition stage
- You build voice interaction systems with Llama 3, Mistral or Gemma-based open-weight models
- You get text output in streaming by processing audio inputs directly
Bolna
85bolna-ai · AI Call Agents & Telephony
Common commercial products in this category: Vapi, Bland AI, Retell AI
- You start phone calls using telecommunications providers such as Twilio or Plivo.
- With services like Deepgram or Azure, you convert conversations into text and process it with models like OpenAI and Llama.
- You synthesize LLM responses aloud through providers such as AWS Polly or ElevenLabs.
- • NeutralGitHub Issue
Request is not going to eleven labs
“2ager} [__init__] task initialization completed 2025-07-10 22:28:42.395 | 2025-07-10 16:58:42.394 INFO {task_manager} [__init__] Conversation config {'optimize_latency': True, 'hangup_after_silence': 10, 'incremental_delay': 1200, 'number_of_words_for_interruption': 2,…”
pipecat-ai · AI Call Agents & Telephony
Common commercial products in this category: Vapi, Bland AI, Retell AI
- By installing the Pipecat package, you use the flops component without additional installation.
- Update import paths by new pipecat.flows namespace
- You apply flow management by following Pipecat guides and examples
- • Repository is archived (no longer maintained)
twilio-labs · AI Call Agents & Telephony
Common commercial products in this category: Vapi, Bland AI, Retell AI
- Using Twilio Media Streams and WebSocket to process audio streaming on phone calls
- Chat with voice assistant by integrating Deepgram and OpenAI services
- GPT You get the assistant to call external tools during the conversation
- • Last update over 1 year ago
- • NeutralGitHub Issue
Got the repo kinda working
“Right now these are my logs from a recent call ``` Server running on port 3000 Twilio -> Starting Media Stream for MZ1cbaeb64da6297ccb08a8cf316d2fe6c Interaction 1: TTS -> TWILIO: Hello! I understand you're looking for a pair of AirPods, is that correct? Twilio -> Audio…”
- • NeutralGitHub Issue
I get this issue
“when i run "npm run outbound" i get this issue  – Library for voice conversation with LLMs
“Enterprise is not in Vocode's target market. Target market is startups and individual devs. There are bloated and over engineered voice chat services for LLMs for Enterprise already.”