# Vellum alternatives for developers: Kortix and Langfuse, the open-source options

> After you stop using Vellum, the developer question is what you run next and who owns it. Kortix is the open-source AI Operating System a team owns, and Langfuse is the open-source tool for tracing and evaluating LLM apps.

URL: https://vellumalternative.com/vellum-alternatives-for-developers

## Kortix, Vellum and Langfuse, and what each one leaves you

Kortix is the open-source option we recommend; every rival cell comes from that product's own site, checked October 2026.

| | Kortix (recommended) | Vellum | Langfuse |
| --- | --- | --- | --- |
| What it is | The open-source AI Operating System | A personal AI assistant for one person | Open-source tracing and evals for LLM apps |
| Open source | Yes. Open source. Read it, fork it, audit it. | Yes, its page says you can inspect the code | Yes, self-host for free |
| Where it runs | Kortix Cloud, your VPC, or your own on-prem network | Your machine or Vellum Cloud | Langfuse Cloud or your own infrastructure |
| What you own | Your agents, skills, memory and connectors in one git repo you own | One assistant's memory and credentials vault | Your traces, prompts and evaluation datasets |
| Models | Any model provider with your own keys | OpenAI, Anthropic, Gemini, or open weights via Ollama | Works with any model and framework |
| Price to start | Free is $0 with 200 credits per month and 1 project. | See Vellum's pricing page | See Langfuse's pricing page |

## What changes when you move off Vellum

When a developer looks past Vellum, what matters is what you end up holding once the assistant is gone. Vellum is one assistant for one person: [its homepage](https://www.vellum.ai/) says memory and credentials live on your machine or in Vellum Cloud, and [its pricing page](https://www.vellum.ai/pricing) says you can deploy it on your own hardware, a VPS or a private cloud. That is a real self-hostable path, and it is shaped around one person's context.

Kortix answers the same question for a team. Kortix is the open-source AI Operating System, and the configuration is one git repo you own, so the agents, skills, memory and connectors that do the work are files you can read, diff and roll back. One isolated sandbox per session. Each session has its own isolated machine and branch. Session work reaches main through a change request. Merge is default-deny for agents.

## What each option leaves you holding

- Kortix leaves you the system: the code, the configuration, the memory and the tool rules, in a repo you own. Read the docs at [Kortix](https://kortix.com/docs).
- Vellum leaves you one assistant: its memory, its credentials vault and its built-in skills, on your machine or in Vellum Cloud.
- Langfuse leaves you the observability layer: traces, prompt versions, evaluation datasets and exports for the LLM apps you build, and [its self-hosting docs](https://langfuse.com/self-hosting) run it on your own infrastructure.

Bring a project up from a repo:

```sh
curl -fsSL https://kortix.com/install | bash
kortix init
kortix ship
```

## Which one fits the job

Pick by the work you need done. If you want one assistant that remembers you and runs on your own machine, Vellum is built for that. If what you need is to trace, evaluate and improve an LLM application you are building, Langfuse is the open-source tool for that layer. If you want an open-source system where a team's agents, memory and connectors live in a repo the team owns and the work lands through a review, Kortix is the one.

The [Vellum pricing breakdown](/vellum-pricing) compares the two price shapes, and the [Kortix vs Vellum comparison](/kortix-vs-vellum) sets the products side by side.

_FAQ_

## Vellum alternatives for developers, answered

Short answers, each from the product's own site or repo.

### What is a Vellum alternative for developers?

The answer depends on what you need after Vellum. Kortix is the open-source AI Operating System a team owns, where agents, memory and connectors are files in one git repo. Langfuse is the open-source tool for tracing and evaluating LLM apps.

### Is Langfuse an alternative to Vellum?

Langfuse is a different layer from Vellum. Langfuse traces, manages prompts and runs evaluations for LLM applications, and it does not run agents or hold a team's memory. Vellum is a personal assistant, and Kortix is the system a team runs agents on.

### Can I self-host these options?

Yes. Kortix self-host is free and runs as one stack on your own server; Langfuse self-hosts with Docker on your own infrastructure; and Vellum's pricing page says you can deploy it on your own hardware, a VPS or a private cloud.

### Is Kortix open source?

Yes. Open source. Read it, fork it, audit it. Your agents, skills, company memory and connectors live in one git repo you own.

## Run a team on one repo you own.

Start on Kortix, and add Langfuse when you need tracing and evaluation.

[Try Kortix](https://kortix.com) · [Read the docs](https://kortix.com/docs)

Open source · Any model, your keys · Self-host, VPC, or on-prem