hy3 vs fable 5 vs opus 4.8 vs sonnet 5

@TencentHunyuan just dropped hy3 – their new open-weight model under apache 2.0. following the april preview they scaled up post-training, and it now rivals flagship open models with 2-5x the params. api pricing: ~$0.15 in / ~$0.59 out per 1m tokens. built for coding, office work, frontend, agentic tasks

so we ran a test: hy3 vs fable 5 vs opus 4.8 vs sonnet 5
three prompts, one-shot each:

• ocean wave crumbling a sand castle (canvas)
• looping factory assembly line (html/css/js)
• interactive 3d city with three.js + orbitcontrols

self-contained files, no libraries beyond the cdn where asked

totals across all three prompts:

1. hy3 – 1231 loc / 14m34s
2. sonnet 5 – 1373 loc / 18m55s
3. fable 5 – 1546 loc / 18m32s
4. opus 4.8 – 1904 loc / 27m21s

hy3 is the fastest and the leanest by a wide margin

we had opus 4.8 analyze hy3's code. the read:

- sand castle: checklist-complete but the crumble is parametric, not physical. it shrinks and slumps the towers and fades alpha instead of dissolving into grains. the cheap-but-plausible interpretation. the tell of a smaller model

- factory line: the arm-to-part sync is actually causal, not faked. it triggers each robot early by exactly the arm's descent time, so the tap lands right as the part arrives. it also pre-seeds the belt so it never cold-starts empty. clean state machine. one latent bug – a part gets marked processed before checking if the robot is free, so at a faster spawn rate a "laptop" could ship missing a part. never fires at current timing, but the invariant isn't enforced

- 3d city: genuinely frontier-adjacent. correct modern setup (pcfsoft shadows, srgb, aces tone mapping, damped orbit + auto-rotate pause). clones the window texture per building and scales the uv repeat to each building's dimensions so windows don't stretch. downside: no instancing – ~800 texture clones across 200 buildings. runs fine, not optimized. roads are implicit gaps, not explicit planes

our observations:

• hy3 is quite fast
• its animations are simple but you can see it trying – it adds detail, and the 3d render sits at the same level as the frontier models
• sonnet 5 is weak here. hy3 beats it on the sand castle and the 3d render, level on the conveyor
• opus 4.8 is anthropic's best model after the fable 5 nerf – it beats fable on the conveyor and the 3d render

net: hy3 runs clean and well-formed across all three with zero syntax errors, even version-matching the three.js core and examples build. it's economical rather than ambitious – it does the minimum viable version of each hard requirement well, and only reaches for the expensive interpretation on the 3d task

a very coherent profile for a cost-optimized open-weight model