Solar Mini 4: How I Run It Free Inside Hermes Agent

Solar Mini 4 is a new small AI model from Upstage, and right now you can run it for free inside Hermes Agent through Nous Portal.

I set it up on video in a few minutes, so this page is the operator version of that walkthrough.

You'll learn what Solar Mini 4 actually is, every free way to reach it, how to wire it into Hermes Cloud and Hermes Desktop, and the one setting that quietly turns a free model into a paid one.

I'll also give you my honest view on where it's good and where it isn't, because it's fast and free but it's not a frontier model.

What Is Solar Mini 4?

Solar Mini 4 is a compact language model built by Upstage, an AI company from South Korea.

It's a mixture-of-experts model, which means only a small slice of the model switches on for each word it writes.

Upstage's own model page lists it at 35 billion parameters in total with 3 billion active at any one time.

That small active size is the reason it feels so quick when you chat with it.

Upstage describes it as a "cost-efficient compact model for agentic use", and that's exactly the job I tested it on.

Here's the spec sheet I checked against Upstage's console docs, OpenRouter and Artificial Analysis.

Spec	What the official sources say
Maker	Upstage, a South Korean AI lab
Model type	Mixture-of-experts with 35B total and 3B active parameters
Context window	Upstage's docs list 512K tokens, and OpenRouter and Nous Portal serve 524,288 tokens
Max output	Upstage lists up to 128K output tokens
Languages	Korean, English and Japanese for both input and output
Features	Reasoning mode, tool calling, structured outputs and chat
Release	Upstage lists 22 September 2026, with a February 2026 training data cut-off
Weights	Proprietary, so you can't download it and run it locally
Artificial Analysis Intelligence Index	24

In my video I rounded the context window to 500,000 tokens, and the official figure is 512K on Upstage's docs, so use that one.

Artificial Analysis scores it 24 on its Intelligence Index, which is the number I quoted on camera.

Their write-up says it beats Qwen 3.6 35B by 6 points with the same 3B active parameters, and it lands 16 points above Upstage's previous flagship, Solar Pro 3.

Who Made Solar Mini 4, And What Does It Cost?

Upstage makes Solar Mini 4, and it sells the model through its own console and API.

The normal API price on Upstage's console is $0.10 per million input tokens and $0.40 per million output tokens.

Upstage was running a 70% discount through 10 October (UTC) when I checked, so the price you see may be lower for a few days.

OpenRouter lists it at $0.05 per million input tokens and $0.20 per million output tokens.

The part most people care about is the free route, and there are two of them right now.

The first free route is Nous Portal, which is giving Solar Mini 4 away for a two-week window inside Hermes Agent.

The second free route is the Upstage Console Playground, which says you can chat with Solar Mini 4 in your browser with no API key needed.

The Playground is great for a quick feel, but it isn't an agent, so for real work I use the Nous Portal route.

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The Problem Solar Mini 4 Solves For Agent Operators

Running an AI agent all day burns tokens, and frontier models get expensive fast.

Most of what an agent does isn't hard thinking, because it's checking news, summarising pages, sorting files and answering simple questions.

Paying top-tier prices for that grunt work is the old way, and it adds up quickly.

A fast, cheap small model that handles basic agentic tasks lets you save the expensive brain for the jobs that actually need it.

Solar Mini 4 slots into that "everyday worker" lane, and while the free window is open it costs you nothing to try.

How To Set Up Solar Mini 4 In Hermes Cloud

Hermes Cloud lets you deploy a Hermes Agent instance in the cloud and use the free models on Nous Portal, so you don't need anything installed on your computer.

Here's the exact order I followed.

Go to portal.nousresearch.com/cloud and sign in to Nous Portal.
Click to create a new agent.
Open the model section for that agent.
Scroll down the model list and click the "Free" filter.
Pick Upstage Solar Mini 4 from the free list.
Save the agent, and it's ready to chat.

When I opened that free list, Solar Mini 4 sat next to a handful of other free models.

Free model I saw on Nous Portal	Maker
Solar Mini 4	Upstage
Nemotron	NVIDIA
Laguna XS 2.1	Poolside
Ling 3.1 Flash	inclusionAI
Ling 3.0 Flash	inclusionAI
Step 3.7 Flash	StepFun
LongCat 2.0	Meituan

The free list rotates, so treat this table as a snapshot from the day I recorded rather than a permanent menu.

How To Set Up Solar Mini 4 In Hermes Desktop

Hermes Desktop is where I do most of my testing, and I keep one profile per model.

That habit lets me switch between models in two clicks and compare them on the same job.

I've got the full step-by-step for this in my Solar Mini 4 Hermes setup walkthrough, so here's the short version.

Open Hermes Desktop and create a new profile.
Name the profile after the model, so I called mine "solar mini 4".
Go to the model setup for that profile and choose Nous Portal as the provider.
Refresh the models list so the newest free models show up.
Pick Solar Mini 4 from the free models.
Start a new chat and send a test message.

If you've never installed Hermes before, start with my guide on setting up Hermes Agent in one click and come back here.

The One Setting You Must Get Right: Free vs Paid Solar Mini 4

This is the trap that catches people, and it's the one thing I told everyone to check in the video.

Nous Portal lists Solar Mini 4 twice.

One entry is the free variant, and its model ID ends in ":free", which is upstage/solar-mini4:free.

The other entry is the paid variant, upstage/solar-mini4, which Nous Portal lists at $0.05 per million input tokens and $0.20 per million output tokens.

If you pick the wrong one, your agent works perfectly and quietly bills you.

Here's how to set the free one as your main model through the Hermes dashboard.

Run hermes dashboard in your terminal, or open it from the manage section of the Agent OS.
Go to Models.
Click "Set main model".
Type "solar" into the search box.
Choose Nous Portal as the provider.
Pick the variant labelled as the free Solar Mini 4, not the paid one.

I'd double-check the model ID after you save, because the two names look almost the same at a glance.

How To Use Solar Mini 4 Once It's Running

The first thing I typed was simply "test".

It came back fast with a reply saying the session was live, and it noted that memory was switched off for that profile.

Then I gave it a real job, which was to find AI automation news from the last seven days.

It came back quickly with a breakdown, the sources it used and a short "what stands out" section.

It even surfaced an Oracle launch I hadn't heard about, which is exactly what I want from a news-scanning agent.

Here are the jobs I'd give it first as an operator.

It handles quick research sweeps where you want a summary and sources rather than deep analysis.
It works well for drafting first passes of emails, notes and outlines that a stronger model or a human will tidy later.
It's a decent fit for long-document reading, because Upstage built it for long-context workloads.
It suits multilingual work in Korean, English and Japanese, since Upstage supports all three for input and output.
It can call tools, because Upstage lists tool calling and structured outputs as supported features.

Running Solar Mini 4 From The Agent OS

I run all of this inside my Agent OS, which is my own dashboard for Hermes and every other agent I use.

Open the Hermes tab, pick the solar mini 4 profile, and you're chatting with Hermes running on Solar Mini 4 directly.

The manage section in the Agent OS also opens the Hermes dashboard, so you can swap the main model without touching the terminal.

If you want Hermes talking to other tools as well, my Hermes MCP server setup shows how I connect it.

Solar Mini 4 Rate Limits, Gotchas And Limits

Free models get rate limited, and Solar Mini 4 is no different.

If you hit a limit, switch your profile to another free model from the same list and carry on.

If Solar Mini 4 doesn't appear in your model list, refresh the models list first, because new free models don't always show up straight away.

The free window on Nous Portal is two weeks, so don't build a client workflow that depends on it staying free forever.

Artificial Analysis flags it as very verbose, with about 88,000 output tokens per Intelligence Index task, so long answers can eat into any paid budget.

The weights aren't released, so you can't run Solar Mini 4 offline on your own machine.

One viewer commented that it ran badly for them, and I believe them, because quality varies with the task and the prompt.

That's why I always say test it on your own work before you trust it.

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My Honest Verdict On Solar Mini 4

Solar Mini 4 is not frontier level.

It isn't in the same league as Claude Opus 5.5, and I wouldn't hand it your hardest coding or strategy work.

What it does well is respond fast, cost nothing during the free window and handle basic agentic tasks without fuss.

For an operator, that makes it a great second profile for news checks, summaries and first drafts.

Keep your strongest model for the hard jobs, and let Solar Mini 4 do the cheap, repetitive work.

Also On Our Network

Solar Mini 4 FAQ

What is Solar Mini 4?

Solar Mini 4 is a compact mixture-of-experts language model from Upstage in South Korea.

Upstage lists it at 35 billion total parameters with 3 billion active, a 512K context window and support for reasoning, tool calling and structured outputs.

Is Solar Mini 4 free?

Solar Mini 4 is free for a two-week window on Nous Portal, where you can use it inside Hermes Agent.

The Upstage Console Playground also lets you chat with it in your browser with no API key, while the paid API costs $0.10 per million input tokens and $0.40 per million output tokens on Upstage.

How do I use Solar Mini 4 in Hermes Agent?

Create a Hermes Cloud agent at portal.nousresearch.com/cloud and pick Solar Mini 4 from the free models, or create a Hermes Desktop profile and choose it from the Nous Portal model list.

Then set it as your main model in the Hermes dashboard and make sure you select the free variant.

Why does Solar Mini 4 appear twice in Nous Portal?

Nous Portal lists a free variant ending in :free and a paid variant without it.

If you pick the paid one, your agent still works but you get billed, so always choose the free variant during the promo.

Can I run Solar Mini 4 locally?

No, you can't run it locally, because Upstage has not released the weights.

You reach it through Upstage's API, OpenRouter, Nous Portal or the Upstage Playground.

Is Solar Mini 4 as good as Claude Opus 5.5?

No, it isn't frontier level, and I'd keep Claude Opus 5.5 or another top model for hard work.

Solar Mini 4 is fast and cheap and handles basic agentic tasks like news checks and summaries well.

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About Julian

I'm Julian Goldie, an SEO entrepreneur, author and founder of the AI Profit Boardroom, which has 3,400+ members.

I help business owners scale with AI agents, automation and SEO.

I've built a 7-figure agency, Goldie Agency, with a team of around 50 people.
I've grown a YouTube channel to 400,000+ subscribers.
I wrote the Amazon best-sellers "SEO Link Building Mastery" and "Agency Marketing Mastery".
My Udemy courses have taught over 50,000 students.

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Set up the free variant today, give it one real job, and you'll know within ten minutes whether Solar Mini 4 earns a profile in your agent stack.