I've tried their "shimmer" site https://shimmer.poolside.ai (seems in the same vein of products as AI Studio/ Repl.it)

Either the harness or the models are very bad in it, I'd say they feels less capable than Gemma4-E2B in virtually any harness. The larger model would plan out some steps and never actually perform them even when prompted to several times. The smaller model actually got more done. My guess is it's the harness, since you've had a good experience. Haven't tried the pool cli yet.