GLM 5.1

GLM 5.1 is the oldest Z.ai checkpoint still on the gateway. It is a 355B text-only model with a 1M context window and an intelligence index of 26, the same published index as GLM 5.2. It exists so existing integrations pinned to 5.1 keep working. New tool-calling work should use GLM 5.3, which adds image input and a higher index.