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Opus 5.5: what it is and how one builder used it

Opus 5.5 is the model a builder used inside Claude Code to write a WebGPU ocean renderer. Here is the run and what it shows, from the repository itself.

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A frosted glass block with a wave crest glowing soft violet sits on a clay disc, with a small lens on a stand beside it.
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Opus 5.5 is the model that, by its author’s account, wrote a WebGPU ocean renderer from scratch inside Claude Code. The sources show one real build: a one-line goal, a self-checking loop and a 61 KB result.

What the sources say about Opus 5.5

The repository states plainly that it was built with Claude Code (Opus 5.5). That is the model claim the table below rests on.

Question Answer from the sources
What is it? The model Claude Code ran on for this build
What did it make? A real-time ocean renderer with no engine

If you pay for a plan, the limits matter more than the build. The limits page on this site, Claude Code usage limits, covers what spends a quota, and Creating my logo with Opus 5.5 is a smaller run on the same model.

How the build was run

The author asked for the most realistic water it could produce, in WebGPU, with a floating camera, and left the architecture to the model. The model then checked its own work by rendering screenshots in headless Chrome, with separate critic subagents reviewing them, so it was not grading its own output.

That split is the part to copy. A reviewer that did not write the code usually catches more than the writer does.

Step Who did it
Goal and constraints Author, in one request
Architecture and code The model
Screenshots in headless Chrome The model
Review of the screenshots Separate critic subagents
Feedback, mainly on clouds Author

The feedback led to replacing the volumetric clouds with the flat layers, then fixing their edge aliasing.

What it produced

The renderer is a Tessendorf FFT sea. The numbers below are the author’s own, and only the frame time is a measurement.

Part Stated value
Wave cascades six cascades of 256 by 256 samples
Patch sizes 1103 m down to 0.26 m
Mesh 17 levels, 6.25 cm vertex spacing near the camera
Reach 160 km
Cloud layers Two flat layers
Frame time about 6 to 8 ms per frame at 2560 by 1440 on an RTX 5070 Ti

The frame time was taken while other programs were also using the GPU, so treat it as one run on one card. Far water is still somewhat darker than the horizon sky, and the scene is open ocean only.

Run it yourself this week

You need a recent Chrome with WebGPU and a reasonably capable GPU. Opening the HTML file directly works, though running from source needs three commands.

Terminal window
npm install
npm start      # serves http://localhost:8080/
npm run build  # after editing anything under js/

The repo has 601 stars and 97 forks, and the page is self-contained. To test a camera angle, add URL parameters.

?w=2560&h=1440&ui=0&windSpeed=12&swellHs=2&sunElev=8

For a different cost view, A week on Sonnet 5.5 compares agent numbers after a move off Opus 5.5.

Verdict

Opus 5.5 is a Claude Code model, and the sources show what it can build. Copy the loop of one goal, self-made screenshots and separate critics, then check your own plan’s usage before you run it for hours.

Try it on your own plan: open the web-ocean repository

Sources:GitHub - Noniv/web-ocean: Real-time WebGPU ocean renderer written from scratch, no engine. FFT waves, whitecaps, sun glitter, physically bas, Watch Me Vibe Code an Animated App with Claude Opus 5.5 (It's Super Smooth) - YouTube, Reddit.

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