Open Source AI Development Platforms using CSS

A curated collection of the best free and open source platforms for building AI applications, covering agent frameworks, retrieval pipelines, prompt orchestration and model gateways using CSS.

Hermes Agent

A self-improving agent from Nous Research that learns skills, keeps memory across sessions and reaches you on any chat platform.

Alternative to:

ChatGPT

Desktop AI agent with persistent memory across platforms

Stars
257,810
Forks
56,545
Last commit
17 hours ago

Dify

An open source platform for building LLM applications, combining visual workflows, RAG pipelines, agents and model management in one interface.

Alternative to:

Voiceflow

Build and deploy AI agents and RAG pipelines visually

Stars
159,754

Paperclip

A self-hosted control plane that gives teams of AI agents an org chart, budgets, approvals and audit trails from one dashboard.

Alternative to:

Lindy

Org chart, budgets, and governance for AI agent teams

Stars
108,076

LobeChat

Open source workspace for hiring, scheduling and supervising a team of AI agents that keeps working while you are away.

Alternative to:

ChatGPT

Manage, build, and run AI agent teams around the clock

Stars
83,541

LiteLLM

An open source gateway exposing more than a hundred LLM providers behind one OpenAI-compatible interface, for teams centralising model access.

Alternative to:

Cloudflare AI Gateway

LLM gateway for auth, load balancing, and spend tracking

Stars
62,198

Mem0

A memory layer that lets AI assistants and agents remember user preferences and past sessions instead of restarting context every conversation.

Alternative to:

Supermemory

Persistent memory layer for AI agents and apps

Stars
67,951

Multica

A self-hostable workspace where AI coding agents are assigned issues like teammates, for engineering teams running several agent CLIs at once.

Alternative to:

Jira

Project management for teams mixing humans and AI agents

Stars
54,033

LibreChat

A self-hosted chat interface that puts every model provider, agent, tool and file workflow behind one familiar conversation UI.

Alternative to:

ChatGPT

One interface for all your AI models and conversations

Stars
46,400

Agno

Python framework and runtime for building agent platforms, serving them as an API and managing them through a web control plane.

Alternative to:

Microsoft Copilot Studio

Model-agnostic platform for building intelligent AI agents

Stars
42,926

CopilotKit

SDK for developers building agent-native apps, adding chat, generative UI, shared state and human-in-the-loop across web, mobile and chat platforms.

Alternative to:

Voiceflow

Build AI copilots for your product in hours, not months

Stars
38,294

OpenWork

A desktop app and MCP server for sharing AI skills, plugins and connected services across your agents, teammates and machines.

Alternative to:

OpenAI Codex

Multi-model AI workspace with org-wide skill sharing

Stars
24,295

Suna

Open source AI management system where agents, skills, memory and connectors live in a git repository your company owns.

Alternative to:

ChatGPT

AI agent that autonomously handles real-world tasks

Stars
20,323

Parlant

Interaction control harness for customer-facing AI agents, giving teams precise behavioral control in regulated and high-stakes conversations.

Alternative to:

Google Dialogflow

Structured control layer for customer-facing AI agents

Stars
18,312

Portkey AI Gateway

An API gateway that routes requests to hundreds of model providers, with retries, fallbacks, caching and guardrails in front.

Alternative to:

Cloudflare AI Gateway

Complete production stack for AI teams

Stars
13,284

Nango

An integration platform that handles auth, execution and observability for 900 plus APIs, for teams shipping product integrations.

Alternative to:

Composio

Build product integrations with 500+ APIs in hours

Stars
13,014

Bifrost

An AI gateway that fronts more than twenty model providers behind one OpenAI-compatible API, with failover, load balancing, and caching.

Alternative to:

Cloudflare AI Gateway

Ultra-fast AI gateway with enterprise-grade reliability

Stars
9,155

Rivet

A library for stateful backends where each agent, session, document or tenant runs as a long-lived actor with in-memory state.

Alternative to:

Azure Durable Functions

Build stateful backends with in-memory actors

Stars
6,379

ACI.dev

A tool-calling platform that connects AI agents to hundreds of services with managed authentication, permissions and dynamic tool discovery.

Alternative to:

Composio

Build reliable AI agents with unified tool integration

Stars
4,924

Envoy AI Gateway

Open source gateway that routes application traffic to generative AI services, built on Envoy Gateway for teams standardizing model access.

Alternative to:

Cloudflare AI Gateway

Route GenAI traffic with confidence using open source

Stars
2,306

LLM Gateway

An API gateway that routes requests to multiple LLM providers through one OpenAI-compatible endpoint while tracking tokens, costs, and response times.

Alternative to:

Cloudflare AI Gateway

Unified API for all LLM providers with analytics

Stars
1,714

Hexabot

Self-hosted platform for building agentic workflows in YAML and running them across conversational channels with tools, memory and RAG.

Alternative to:

Voiceflow

Self-hosted AI agents and workflows across any channel

Stars
1,148

ByteChef

A workflow automation platform where AI agents run as ordinary steps and 250 plus connectors double as agent tools and MCP tools.

Alternative to:

Zapier

Build AI agents and automate complex workflows seamlessly

Stars
1,050

OpenComputer

Deploy TypeScript agents to durable cloud sessions that hibernate when idle, aimed at developers who build agents as code.

Alternative to:

Modal

Persistent cloud VMs that hibernate and wake in seconds

Stars
574

Giselle

Visual builder for AI agent workflows that chains several models and plugs into GitHub, for teams automating product delivery work.

Alternative to:

Lindy

Build and deploy AI agents through visual workflows

Stars
557

Tiledesk

An open source live chat and chatbot platform for building customer support across web, WhatsApp, Messenger and Telegram from one script.

Alternative to:

Voiceflow

No-code platform to build AI agents and automate support

Stars
15

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Open Source AI Development Platforms using CSS

A curated collection of the best free and open source platforms for building AI applications, covering agent frameworks, retrieval pipelines, prompt orchestration and model gateways using CSS.

Hermes Agent

Dify

Paperclip

LobeChat

LiteLLM

Mem0

Multica

LibreChat

Agno

CopilotKit

OpenWork

Suna

Parlant

Portkey AI Gateway

Nango

Bifrost

Rivet

ACI.dev

Envoy AI Gateway

LLM Gateway

Hexabot

ByteChef

OpenComputer

Giselle

Tiledesk

Hermes Agent

Dify

Paperclip

LobeChat

LiteLLM

Mem0

Multica

LibreChat

Agno

CopilotKit

OpenWork

Suna

Parlant

Portkey AI Gateway

Nango

Bifrost

Rivet

ACI.dev

Envoy AI Gateway

LLM Gateway

Hexabot

ByteChef

OpenComputer

Giselle

Tiledesk

Langflow