Claude Sonnet 5.5 vs Opus 5.5: same prompt, same starting point
On 22 September, Claude Opus 5.5 built Planet Pop from one prompt, in 14 minutes for $2.54. Claude Sonnet 5.5 came out on 28 September, so we put it in exactly the same spot: the same instructions and notes Opus had loaded that day, the same message, and the same lookups Opus had already made before it wrote any code, word for word. Then we ran it 4 times. Every run was a fresh one-shot: new session, empty folder, no memory of the other runs.
output a ThreeJS 3D cartoony/comics-like planet, with vibrant life on it: clouds, mountains, city buildings, cars and plane romaing it. It should be possible to orbit around and zoom and see the details. No harness is to be used
Time and cost
Measured from each session's own log (every request to the model), priced at Anthropic list rates.
| Run | Time | Requests | Output tokens | List price |
|---|---|---|---|---|
| Opus 5.5, 22 Sept (Planet Pop) | 14.0 min | 15 | 56.6k | $2.54 |
| Sonnet 5.5, average of 4 | 11.2 min | 11.5 | 64.9k | $1.69 |
| Sonnet 5.5, run 1 | 7.0 min | 9 | 44.5k | $1.28 |
| Sonnet 5.5, run 2 | 15.2 min | 12 | 78.3k | $1.92 |
| Sonnet 5.5, run 3 | 8.1 min | 10 | 54.4k | $1.45 |
| Sonnet 5.5, run 4 | 14.3 min | 15 | 82.6k | $2.11 |
Sonnet 5.5 cost about two thirds of Opus 5.5 ($1.69 vs $2.54) and was about 20% faster. The 4 runs ranged from 7.0 to 15.2 minutes and $1.28 to $2.11. All 4 delivered a working, playable planet.
Play them
Drag to spin, scroll or pinch to zoom.
Other Sonnet runs: run 2 · run 3 · run 4
Same camera, every planet
Left to right: Opus 5.5, then Sonnet 5.5 runs 1 to 4, captured by the same automatic check.
Tech stack
All five are one self-contained HTML file using three.js from jsDelivr: no framework, no build step.
| Opus 5.5 · Planet Pop | Sonnet 5.5 · 4 runs | |
|---|---|---|
| three.js | 0.170 | 0.160.1 in all 4 |
| Comic look | custom shaders plus a post-processing pass: ink outlines, halftone shadows | toon shading, no post-processing (all 4) |
| Extras | shadows, many instanced meshes, Google Fonts | lighter: 1 to 3 instanced meshes, no web fonts, shadows in 1 of 4 |
| Size | 48 KB | 28 to 41 KB |
Our take
- Price: Sonnet 5.5 built a complete planet for about two thirds of Opus 5.5's cost, and a bit faster.
- Look: Opus 5.5's Planet Pop is still the richer planet: real comic ink and halftone, ring roads with traffic, and a zoom that lands you in a forest. Sonnet makes cleaner, simpler planets and is weakest up close.
- Consistency: the 4 Sonnet runs stayed within $1.28 to $2.11. Same prompt, different planet every time.
Earlier, looser test (28 Sept): 4 runs each on a later version of the prompt
Before this, we compared the two models on a later variant of the brief (it also pointed at a reference planet) with a trimmed version of the same notes, 4 runs each. Sonnet 5.5 averaged 21.7 minutes and $2.63, Opus 5.5 24.1 minutes and $4.49. Play those 8 planets: Sonnet 1 · Sonnet 2 · Sonnet 3 · Sonnet 4 · Opus 1 · Opus 2 · Opus 3 · Opus 4.
What this does not show
- Opus has one run (the original 22 September session); Sonnet has four.
- Live session vs one-shot: Opus worked in a live Claude Code session; each Sonnet run was a one-shot Claude Code call carrying the same context. Sonnet also had one extra rule: only write files in its own folder.
- Not blind, no real-GPU frame rate measured, not tested on a phone. Needs internet (three.js from jsDelivr).
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