8 Best Astra Assistant API Alternatives in 2026 (Open Source)
Astra Assistant API — Drop in replacement for the OpenAI Assistants API . Drop-in OpenAI Assistants API v2 replacement supporting 30+ LLM providers via LiteLLM, backed by AstraDB vector storage
These 8 open-source tools do the same job. They are ordered by how closely they match Astra Assistant API, with live GitHub data so you can see which projects are actively maintained.
| Tool | GitHub stars | Stars / 30d | Last commit |
|---|---|---|---|
| Astra Assistant API(original) | 207 | +-0 | 2025-08-18 |
| Open Assistant API | 367 | +1 | 2024-12-14 |
| LiteLLM | 59.9k | +3,007 | 2026-09-30 |
| OpenLLM | 12.5k | +53 | 2026-05-29 |
| Ollama | 182.0k | +2,511 | 2026-09-30 |
| LibreChat | 45.2k | +1,629 | 2026-09-30 |
| private-gpt | 57.6k | +56 | 2026-09-21 |
| Open WebUI | 153.6k | +3,958 | 2026-09-21 |
| NadirClaw | 655 | +46 | 2026-09-23 |
1. Open Assistant API
The Open Assistant API is a ready-to-use, open-source, self-hosted agent/gpts orchestration creation framework, supporting customized extensions for LLM, RAG, function call, and tools capabilities. It
What sets it apart: Open-source OpenAI Assistant API compatible service supporting multiple LLMs via One API, with RAG, web search, and local deployment
Best for: self-hosted-openai-assistant-alternative; multi-llm-assistant-apps; enterprise-local-deployment
2. LiteLLM
Python SDK, Proxy Server (AI Gateway) to call 100+ LLM APIs in OpenAI (or native) format, with cost tracking, guardrails, loadbalancing and logging. [Bedrock, Azure, OpenAI, VertexAI, Cohere, Anthropi
What sets it apart: Unlike OpenRouter (hosted-only routing), LiteLLM is self-hostable and provides a full gateway with per-user spend tracking, virtual keys, and A2A/MCP protocol support — making it the enterprise LLM traffic controller
Best for: ML platform teams managing multi-provider LLM access with centralized cost tracking and auth; Developers switching between LLM providers without changing application code
3. OpenLLM
Run any open-source LLMs, such as DeepSeek and Llama, as OpenAI compatible API endpoint in the cloud.
What sets it apart: Unlike Ollama which focuses on local/desktop usage, OpenLLM bridges local development and cloud production through unified BentoML tooling — providing the same CLI workflow from laptop to Kubernetes cluster with OpenAI API compatibility
Best for: Teams wanting the fastest path from model selection to OpenAI-compatible API endpoint; DevOps engineers deploying open-source LLMs to production with Docker/Kubernetes
4. Ollama
Get up and running with Kimi-K2.5, GLM-5, MiniMax, DeepSeek, gpt-oss, Qwen, Gemma and other models.
What sets it apart: Unlike vLLM (production server focus) or LM Studio (GUI-first), Ollama is the simplest CLI-first tool for running local LLMs with one-command setup, an OpenAI-compatible API, and the largest ecosystem of 100+ community integrations.
Best for: Developers who want to run open-source LLMs locally with zero configuration; Privacy-sensitive use cases requiring fully offline LLM inference
5. LibreChat
Enhanced ChatGPT Clone: Features Agents, MCP, DeepSeek, Anthropic, AWS, OpenAI, Responses API, Azure, Groq, o1, GPT-5, Mistral, OpenRouter, Vertex AI, Gemini, Artifacts, AI model switching, message se
What sets it apart: Most feature-complete self-hosted ChatGPT alternative — uniquely combines agents, MCP, code interpreter, image gen, and multi-user auth in one package, unlike single-provider UIs
Best for: Organizations wanting a private, self-hosted ChatGPT replacement; Teams needing multi-user AI platform with access control and audit
6. private-gpt
Interact with your documents using the power of GPT, 100% privately, no data leaks
What sets it apart: vs LocalGPT / other private RAG: production-ready OpenAI-compatible API with LlamaIndex backend, dependency injection architecture, and enterprise upgrade path via Zylon — the most mature private document AI platform
Best for: Regulated industries needing fully private document Q&A (healthcare, legal, finance); Teams wanting an OpenAI-compatible API for private RAG; Developers building private AI apps with production-ready primitives
7. Open WebUI
User-friendly AI Interface (Supports Ollama, OpenAI API, ...)
What sets it apart: Unlike LM Studio (desktop-only, personal use), Open WebUI is a full multi-user platform with RAG, RBAC, SCIM provisioning, 9 vector DBs, and Google Drive/OneDrive integration — the most feature-complete self-hosted ChatGPT alternative
Best for: Teams wanting a self-hosted ChatGPT alternative with full data control and Ollama integration; Organizations needing enterprise-grade AI platform with LDAP/SCIM/SSO and multiple vector DB backends
8. NadirClaw
Open-source LLM router & AI cost optimizer. Routes simple prompts to cheap/local models, complex ones to premium — automatically. Drop-in OpenAI-compatible proxy for Claude Code, Codex, Cursor, OpenCl
What sets it apart: Local-first LLM cost optimizer — classifies prompt complexity in 10ms and routes simple requests to 10-20x cheaper models, with no third-party proxy or middleman
Best for: Teams spending heavily on LLM APIs wanting 40-70% cost reduction; AI coding assistants (Claude Code, Cursor) with mixed complexity prompts; Budget-conscious developers using multiple LLM providers