No. Zhipu has not announced GLM-5.5-Flash. The only listing is an empty OpenCode Data placeholder, and the rumor traces back to late September.
An Oct 6 update notes no official announcement, model card, weights or API endpoint for GLM-5.5, and describes the OpenCode GLM 5.5 Flash page as an unverified placeholder.
A check of OpenCode found the GLM 5.5 Flash data page but the model ID was not in the OpenCode Zen model list; the listing does not show that the model was announced or is available.
An OpenCode Data page lists model ID glm-5.5-flash under Zhipu. Sep 20 is when this empty placeholder page's data was last updated, not a release date. It shows 0 tokens, 0 users and 1 completed session, with no context window, price or release date.
We record what sources show, with dates. We don't predict or score how likely a rumor is.