Mystery model Ox Alpha identified as GLM-5.3 Flash

Black-box fingerprinting (tokenizer, error strings, outputs) indicates Ox Alpha, a free multimodal model on OpenRouter with 1M context, is Z.ai's unreleased GLM-5.3 Flash. It reportedly outperforms GPT-5.6 Sol and Fable 5 Max on early coding benchmarks, raising pressure on US labs.