Open source is the cheapest long-term way to run an SMS chatbot, and the most work. The code costs nothing. Everything around it (servers, phone numbers, carrier fees, AI tokens, and your time) still costs real money, and nobody is on call for you at 2am when the webhook stops responding.
This list covers only projects that are actually maintained as of September 28, 2026. The chatbot graveyard is full of frameworks that look alive on a features page and have not had a commit in two years. We also name the retired projects explicitly, because outdated tutorials will happily point you at them.
One thing to understand before you pick: no open-source framework “includes” SMS the way a SaaS platform does. Every project here needs a messaging provider (Twilio, Plivo, or similar) to carry the actual texts, plus a registered 10DLC brand and campaign in the US. The framework handles the conversation logic. The provider handles the network.
How we ranked these
- Maintenance: recent commits, releases, and responsive issue handling.
- SMS wiring: how cleanly it connects to Twilio, Plivo, or another SMS gateway.
- Conversation capability: from simple flows to full NLU and LLM agent support.
- Self-hosting reality: honest deployment effort, not just a Dockerfile that exists.
- License: what you can actually do with the code commercially.
The short version
| Framework | License model | SMS wiring | Best for |
|---|---|---|---|
| Rasa | Free Developer Edition, paid enterprise | Twilio/Plivo adapter | Complex controlled dialogue |
| Chatwoot | Open source, paid hosted option | Twilio or Bandwidth | Support inbox with automation |
| Typebot | Open source, paid cloud | Webhook to Twilio | Visual flow building |
| Microsoft 365 Agents SDK | Open source SDK | Via Azure/Bot channels | Microsoft ecosystem teams |
| Botpress | Source available, managed cloud | Via integrations | Caution: not self-hostable now |
1. Rasa: the serious framework for controlled conversations
Rasa is the most capable open-source option for teams that need precise control over dialogue. Instead of a black-box LLM deciding everything, you define intents, stories, and rules, and the framework manages the conversation state. That makes it the pick for regulated or high-stakes conversations where “the bot said something surprising” is not an acceptable incident report.
The Developer Edition is free and self-hostable, limited to one bot and 1,000 external conversations a month. Paid enterprise tiers with Rasa Studio are custom priced. SMS connects through the Twilio channel (or a Plivo adapter), so inbound texts flow into Rasa and replies flow back out over the carrier network.
The honest cost: Rasa needs Python developers, hosting, and model operations. It is a framework, not a product. Teams that have the engineering capacity get unmatched control. Teams that do not will ship faster with a SaaS builder.
2. Chatwoot: the open-source inbox with SMS and AI assistance
Chatwoot is the most practical pick for support-driven SMS chatbots. It is an open-source customer engagement suite with a unified inbox, and its official SMS integration page confirms two-way texting through your own Twilio or Bandwidth account, with routing, assignment, labels, and automations.
For chatbot behavior, Chatwoot offers Captain AI: reply suggestions and common-question automation layered over the inbox, so routine SMS questions get answered automatically and complex ones route to a human with full context. The repository is actively maintained, including Twilio messaging-service handling and delivery status callbacks. A 15-day hosted trial with no credit card lets you test before self-hosting.
The cost reality: the software is free, but you pay for hosting, the Twilio or Bandwidth account (numbers, per-message rates, carrier fees), and Captain AI usage on top. It is the best open-source option when the goal is “support inbox that texts,” less so for pure marketing automation.
3. Typebot: the visual builder you can self-host
Typebot is a visual, open-source conversational builder with an active repository (commits indexed as recently as late September 2026) and an official cloud offering with a free tier around 200 chats a month.
The SMS caveat matters here: Typebot does not have Twilio as a native provider. The official repository documentation says it requires a custom adapter, which in practice means HTTP and webhook blocks wired to Twilio or another SMS gateway. That is entirely doable and well within no-code-plus-webhooks territory, but it is not the turnkey “connect your number” experience of a SaaS platform.
Pick Typebot when you want a self-hosted visual builder and are comfortable wiring one webhook integration. Skip it when you need native SMS channel support with zero integration work.
4. Microsoft 365 Agents SDK: the official path for Microsoft shops
This entry needs context. The classic Microsoft Bot Framework SDK was archived by Microsoft, with support ending December 31, 2025. Old tutorials still reference it, and new projects should not start there. The official successor is the Microsoft 365 Agents SDK, which reached general availability and is the path Microsoft documents for new agent development.
For SMS specifically, this is a framework for building the agent logic, not an SMS product. You would pair it with Azure communication services or a provider like Twilio for message transport. It makes sense for teams already standardized on Microsoft infrastructure, Azure OpenAI, and enterprise identity, where the agent needs to live inside that ecosystem.
Verify the current release cadence and channel support on Microsoft’s documentation before committing, since this SDK is newer and evolving faster than the retired Framework did.
5. Botpress: powerful, but read the fine print
Botpress appears on many “open-source chatbot” lists, so it needs an honest entry. The current product is primarily a managed cloud platform: Free at $0 with 100 conversations, Plus at $150 a month billed annually, with conversation overage packs. The v12 self-hosted version is sunset. The public repository now holds integrations, SDKs, and examples rather than a full self-hostable replacement for the cloud product.
That means Botpress does not belong on a self-hosted shortlist anymore, whatever older articles claim. It remains a capable managed builder with an AI agent studio, and SMS connects through telephony and messaging integrations. Evaluate it as a SaaS product with source-available components, not as a framework you run on your own servers.
Retired projects to avoid for new builds
Two names to retire from your bookmarks. The Microsoft Bot Framework SDK is archived; Microsoft’s own documentation points new projects to the Microsoft 365 Agents SDK. Botkit is archived and discontinued; its 2026 status across reviews is unambiguous. Tutorials referencing either will still rank in search results for years. Check the repository’s commit history before following any tutorial older than 2024.
The real cost of “free”
A realistic budget for a self-hosted SMS chatbot: a small server ($5 to $20 a month), a Twilio or Plivo phone number ($1 to $2 a month for US local), per-message rates plus carrier fees on every text, US 10DLC registration (roughly $15 brand registration plus $10 per month per campaign), and LLM token costs for every AI-generated reply. At low volume that can still beat SaaS subscriptions. At high volume the engineering time usually dominates the math.
Compliance is also fully yours with self-hosted stacks. There is no vendor compliance team. You implement consent capture, STOP handling, quiet hours, and suppression lists yourself. Read our TCPA consent guide and opt-out keywords guide before your first production send. This is general information, not legal advice.
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Frequently asked questions
What is the best open-source SMS chatbot framework?
Rasa is the most capable for complex controlled dialogue, Chatwoot is the most practical for support inboxes with SMS, and Typebot is the friendliest visual builder. The right pick depends on whether you need dialogue control, a human-agent inbox, or visual flow building.
How do I connect an open-source framework to SMS?
Through a messaging provider. The standard pattern is a Twilio or Plivo account for the phone number and message transport, wired to the framework via its native channel (Rasa, Chatwoot) or webhooks (Typebot). You also need US 10DLC registration for production sending.
Is Rasa really free?
The Developer Edition is free and self-hostable with limits (one bot, 1,000 external conversations a month). Enterprise features and Rasa Studio are paid. The software being free does not make the deployment free: hosting, SMS transport, and AI costs still apply.
Can I self-host Botpress?
Not meaningfully anymore. The v12 self-hosted version is sunset and the current product is a managed cloud platform. If self-hosting is a requirement, choose Rasa, Chatwoot, or Typebot instead.
What happened to the Microsoft Bot Framework?
Microsoft archived the Bot Framework SDK with support ending December 31, 2025. New projects should use the Microsoft 365 Agents SDK, its official successor. Do not start new builds on the retired SDK regardless of what old tutorials say.
Do open-source chatbots handle opt-outs automatically?
Only if you build it. Frameworks give you the conversation engine, not compliance policy. You must implement STOP keyword detection, immediate suppression, consent logging, and quiet hours yourself. SaaS platforms ship much of this prebuilt, which is the real trade you are making.