GLM 5.2 vs. Opus

GLM-5.2 just came out, and it's another step forward for what open models can do. The internet promptly freaked out, and it's hard to tell what's real and what's hype.

So we ran it head-to-head against Claude Opus 4.8: same one-shot prompt, build a 3D platformer in raw WebGL from scratch. Here's our take after running the test and digging through the benchmarks and the buzz.

We're not switching our main off Opus. In our test Opus was faster and shipped a cleaner, more correct game, and it can check its own visual output, which the text-only GLM-5.2 can't. But GLM-5.2 earns a permanent spot in the arsenal: it's a genuinely capable model at a fraction of the price, and because it's open weights, it'll always be available. A closed model can be retired or restricted with little warning (Fable was a recent reminder); weights you can download can't be taken away.

You can play both games right now, or grab the source:

**GLM-5.2's game:3dgame-glm.d.ritzademo.comOpus's game:3dgame-opus.d.ritzademo.comSource for both:**github.com/jamesdanielwhitford/glm-5.2-vs-opus-platformers

Both are browser games written from scratch, with no game engine or 3D rendering library like Three.js. The 3D models are free CC0 assets from Kenney.

Here's how the two runs compared:

| Metric | GLM-5.2 (Pi/OpenRouter) | Opus (Claude Code) | |---|---|---| | Wall-clock build time | 1h 10m 40s | 33m 30s | | Output tokens | 131,000 | 216,809 | | Peak context window | 16% of 1M | 19% of 1M | | Tool calls | 128 | 153 | | Cost | $5.39 (real billed) | ~$21.92 (estimate, list pricing) |

GLM-5.2 cost a fraction as much. Opus finished in half the time and shipped a cleaner game.

On paper, the benchmarks put GLM-5.2 just behind the top closed models, and the online buzz is a mix of genuine signal and astroturf. We get into both below, after the game.

What is GLM-5.2â

GLM-5.2 is Z.ai's latest flagship model. It's open weights under an MIT license, so you can download it, run it yourself, or call it through Z.ai's API.

It's built for long-horizon tasks, the kind of long, multi-step coding-agent work that runs for hours. It ships with a 1M-token context window and two thinking effort levels, High and Max, that trade speed for capability.

GLM-5.2 is text-only, not multimodal. It can't read images, so workflows built around screenshots or diagrams still need a model like Claude Opus.

Z.ai positions it roughly between Claude Opus 4.7 and 4.8 at similar token usage. Here's their