from Hacker News

Show HN: Sim Studio – Open-Source Agent Workflow GUI

by waleedlatif1 on 4/28/25, 4:14 PM with 58 comments

Hi HN! We're Emir and Waleed, and we're building Sim Studio (https://simstudio.ai), an open-source drag and drop UI for building and managing multi-agent workflows as a directed graph. You can define how agents interact with each other, use tools, and handle complex logic like branching, loops, transformations, and conditional execution.

Our repo is https://github.com/simstudioai/sim, docs are at https://docs.simstudio.ai/introduction, and we have a demo here: https://youtu.be/JlCktXTY8sE?si=uBAf0x-EKxZmT9w4

Building reliable, multi-step agent systems with current frameworks often gets complicated fast. In OpenAI's 'practical guide to building agents', they claim that the non-declarative approach and single multi-step agents are the best path forward, but from experience and experimentation, we disagree. Debugging these implicit flows across multiple agent calls and tool uses is painful, and iterating on the logic or prompts becomes slow.

We built Sim Studio because we believe defining the workflow explicitly and visually is the key to building more reliable and maintainable agentic applications. In Sim Studio, you design the entire architecture, comprising of agent blocks that have system prompts, a variety of models (hosted and local via ollama), tools with granular tool use control, and structured output.

We have plenty of pre-built integrations that you can use as standalone blocks or as tools for your agents. The nodes are all connected with if/else conditional blocks, llm-based routing, loops, and branching logic for specialized agents.

Also, the visual graph isn't just for prototyping and is actually executable. You can run simulations of the workflows 1, 10, 100 times to see how modifying any small system prompt change, underlying model, or tool call change change impacts the overall performance of the workflow.

You can trigger the workflows manually, deploy as an API and interact via HTTP, or schedule the workflows to run periodically. They can also be set up to trigger on incoming webhooks and deployed as standalone chat instances that can be password or domain-protected.

We have granular trace spans, logs, and observability built-in so you can easily compare and contrast performance across different model providers and tools. All of these things enable a tighter feedback loop and significantly faster iteration.

So far, users have built deep research agents to detect application fraud, chatbots to interface with their internal HR documentation, and agents to automate communication between manufacturing facilities.

Sim Studio is Apache 2.0 licensed, and fully open source.

We're excited about bringing a visual, workflow-centric approach to agent development. We think it makes building robust, complex agentic workflows far more accessible and reliable. We'd love to hear the HN community's thoughts!

  • by monatron on 4/28/25, 6:02 PM

    Hi y'all. Love the idea and congratulations on your launch. I've used [n8n](https://github.com/n8n-io/n8n) for similar use cases in the past. Any differences in Sim Studio that you'd like to call out?

  • by skeeter2020 on 4/28/25, 6:37 PM

    > Building reliable, multi-step agent systems with current frameworks often gets complicated fast.

    In my experience so far it's not just complicated, but effectively impossible. I struggle to get a single agent to reliably & consistently use tools, and adding n+1 agents is a error multiplier.

  • by simple10 on 4/28/25, 6:01 PM

    Congrats on the launch! Looking forward to playing with it.

    Do you mind elaborating on what differentiates Sim Studio from n8n, Flowise, RAGFlow and other open source flow based AI automation platforms?

  • by ddon on 4/28/25, 5:20 PM

    Would be amazing to be able to design the workflow using your builder, and then export to code (and choose the language) and then copy paste the code into the project... just an idea.

  • by Akhiljp on 5/7/25, 7:52 AM

    Love the launch, is there a way to add observability tools like langtrace into this so that we know what kind of prompts and inputs are going into the flows?

  • by rahimnathwani on 4/29/25, 2:52 AM

    The UI looks lovely.

    If I run Sim Studio with docker compose, how do I point it to the existing `ollama serve` instance running on the host?

    I looked in settings (in the workspace UI) but don't see anywhere to configure the ollama endpoint.

  • by artem_zin on 4/28/25, 8:08 PM

    Youtube demo looks intriguing, I'm self-hosting n8n for exact this purpose with a home run LLM machine in a local k8s cluster (lol) but out of the box I can tell your tool surpasses AI integrations and workflow in n8n.

    Quick glance at GitHub suggests that GitHub package for the Docker image is missing, let me know if you need help with that — happy to contribute!

  • by gavmor on 4/28/25, 5:05 PM

    I'm sure that the complex logic and state management were not trivial to implement, but the link said GUI so I wanted to see some screenshots, but all I saw were two very dim simple forms.

    This space is REALLY struggling to graduate from Gradio-like design sensibilities.

    That being said, I'm looking forward to playing with this, congrats on the launch!

  • by joshcsimmons on 4/28/25, 7:39 PM

    Congrats on the launch the tool looks phenomenal.

    I’m conflicted because n8n does feel like the right level of abstraction but the UI and dated JS runtime environment are horrible. I don’t really want to write my own memory functionality for my AI agents but wondering if it’s worth it just to have a nicer UI and more modern JS env.

  • by dr_kiszonka on 4/28/25, 9:05 PM

    It looks very nice. What happens when a flow that takes 1 minute to complete is triggered by three different Slack messages from different users one second apart. Are flow executions queued or executed in parallel? Is it configurable?

  • by brene on 4/28/25, 9:24 PM

    I checked it out and it’s quite polished for a workflow builder. But I struggled for it to handle lists of content well. But I saw that’s already an ongoing feature request.

  • by badmonster on 4/30/25, 12:17 AM

    How can I add a custom tool or integration to Sim Studio and have it appear in the workflow builder UI?

  • by gitroom on 4/28/25, 8:01 PM

    This is pretty sick, I love having that much control without having to hack around a bunch of stuff.

  • by dmos62 on 4/29/25, 7:24 AM

    What are your main competitors for agent orchestration with observability?

  • by neil_s on 4/28/25, 8:06 PM

    Much simpler UI than n8n, congrats on the launch!

  • by djjose on 4/29/25, 3:58 AM

    Nearly 20 years later, it's fascinating to see Yahoo! Pipes for AI Agents.

  • by pjpr on 4/28/25, 10:52 PM

    congrats on the launch!!

  • by deshraj on 4/28/25, 8:11 PM

    Congratulations, Emir and Waleed! This is exactly the kind of OSS tooling I’ve been waiting for. I’ve spent countless hours wrestling with multi-step agent workflows hidden inside monolithic prompts, and every iteration felt like shooting in the dark. Having a drag-and-drop, executable graph with built-in branching, loops, and observability is a game-changer.

  • by frabonacci on 4/28/25, 5:21 PM

    This could play very well with building a managed agentic system around computer-use for RPA. Great stuff!