Fusion AI API Review: Can It Match Fable 5?

01What Is Fusion AI API and How Does It Work?

Fusion AI API is an API from OpenRouter that uses five models working as a panel, with a judge fusing their answers into one. It aims to achieve Fable 5 level intelligence, but it also works well for creative tasks like building games.

You send one prompt through the API once. The panel generates five responses, and a judge critiques them, fuses them, and returns a single answer. This one-shot process creates detailed outputs, as Julian demonstrated with games made from a single prompt.

The idea is simple: multiple minds are better than one. By comparing and critiquing answers, Fusion avoids mistakes that individual models might make.

02Key Features: Fusing Models, Cost Savings, and More

Fusion's main feature is its panel system. You can choose a budget panel or a premium panel, depending on your needs. With a budget panel, you use cheap models; with a premium panel, you use expensive ones for better outputs.

One key benefit is cost: Fusion can achieve Fable 5 level intelligence on benchmarks while being 50% of the cost of using a top model alone.

The judge model synthesizes the best answers. For example, OpenRouter's tests showed that GPT-5.5 synthesized by Opus 4.8 worked best. Fusion also works well inside the agent operating system, where you can chat, generate responses, and save outputs to your workspace.

Here are some practical uses shown in the episode:

• Creating 3D games, like a maze game or a racer.
• Building websites and web apps.
• Improving or comparing outputs side by side with other models.

03How to Get Started with Fusion AI API

Getting started with Fusion requires access to the API and some basic setup. Here are the steps Julian showed or implied:

1. Sign up for OpenRouter to get API access.
2. Choose Fusion as the model in your API calls.
3. Select a panel type: budget or premium, based on your task and budget.
4. Configure the judge model (e.g., Opus 4.8) if you want to control the synthesis.
5. Send a single prompt via the API. Fusion will return one fused response.
6. Test the output, and if needed, refine your prompt and repeat.

Julian also mentioned you can plug Fusion into the agent operating system. He created something with Claude, plugged it into his workspace, then used Fusion to improve it or compare side by side.

04Using Fusion: Examples and Walkthroughs

Julian showed several examples of what Fusion can create with a single prompt. Here are the highlights:

• A 3D maze game that is fun to play.
• A 'Dragon Realm' game, which looks cool and is engaging.
• A basic open-world block-breaking game that is fun.
• A futuristic neon racer that is smooth and visually impressive.
• A pool game emulator that looks really good.
• A voxel dash game with nice visuals.

To use Fusion, you send one detailed prompt describing what you want. Fusion then generates the full output in one go. Julian emphasized that he didn't need to iterate or test; it worked straight out of the box.

He also showed how to use Fusion inside the agent operating system. You can chat with it, ask questions, and receive generated responses that are saved to your workspace for later use. This integration makes it easier to incorporate Fusion into larger workflows.

05Test Results: Fusion vs Opus 4.8 and Goldie Bench

Julian compared Fusion against Opus 4.8 using the same prompts. Here are the results he showed:

• Pool game: Opus 4.8 made a basic version with the ball behind the wall; Fusion's version was more interesting, with a moving background, though slightly laggy.
• Raycast game: Fusion's version worked smoothly; Opus 4.8's was buggy, with weird graphics and minimal design.
• Outrun game: Fusion's output had cool visuals and was fun; Opus 4.8's was sideways and hard to control.

On Julian's Goldie Bench, Fusion scored the best out of everything on all 42 tasks. Draco Deep Research scored 69 with a budget panel. Fusion also achieved high scores on OpenRouter's benchmarks, sometimes matching or beating solo Fable 5 when synthesized with Opus 4.8.

However, Julian noted that Fusion is not for everyday use. It's best for big, important tasks due to its cost and speed.

06Tips, Limits, and Mistakes to Avoid with Fusion

Fusion has a major limitation: it is slow. Julian noted that asking a question can take five minutes for a response. This adds friction, making it unsuitable for quick back-and-forth.

Another limit is that you can only use Fusion via the API, not as a CLI like Claude's subscription. This means you can't use it in terminal workflows easily.

Here are some tips from the episode:

• Use Fusion for large, complex tasks, not daily queries.
• Choose a premium panel when you need top quality; budget panels are cheaper but may reduce output quality.
• Use Fusion inside the agent operating system to save results and compare models side by side.
• Test Fusion yourself; don't rely only on benchmarks.

Avoid the mistake of expecting quick responses. Plan for the wait. Also, remember that you can combine Fusion with other models—like using Claude to create something and then Fusion to improve it.

07Who Should Use Fusion and Why It Matters

Fusion is for anyone who needs high-quality AI outputs for substantial projects. If you are building games, websites, or doing deep research, Fusion can save time by producing polished results in one shot.

It matters because it shows how combining models can beat any single model. The idea of fusing multiple minds is powerful, and Fusion makes it easy via a single API call.

Julian recommends it for his community, especially for testing and creating with AI. He uses it in his AI Profit Boardroom, where members get training, benchmarks, and daily updates. Fusion tops his leaderboards, which is why he calls it 'definitely worth checking out'.

If you are a beginner, you can start with Fusion for projects, but be prepared for the cost and wait times. For experts, it's a tool to push the boundaries of what AI can create.