GLM 5.3 Fast or Flash: which one does Sume list?

Sume's model catalog lists GLM 5.3 Flash, routed to Z.ai's glm-5.3-flash through OpenRouter, and it does not list a GLM 5.3 Fast. The row is enabled in the in-app agent model picker behind a feature gate that the catalog calls openrouter. If you search for GLM 5.3 Fast and want it in Sume, the honest answer is that there is no such row; Flash is the nearby entry.

What Z.ai's own page covers

The GLM-5.3 page on Z.ai's docs, read on 2026-10-08, describes a 1M-token context window with a 128K maximum output, always-on reasoning, function calling, streaming, context caching and structured output. It does not mention a Flash or Fast variant, so those names should be checked against your provider's own model list. A third-party host may sell a separate speed-tuned tier under a different name.

What the Sume API accepts

The model picker belongs to Sume's chat. The Agent Completions API takes model as sume-agent only, and a different value returns 400 invalid_request. So you cannot request GLM, Haiku or any other model by name through that endpoint; the Sume agent chooses its own models. If you need GLM 5.3 in your own agent loop, call it from your own client and use Sume's hosted MCP server for the media tools.

Check the catalog behind the gate before promising a user a model. A listed row is enabled for the picker only for workspaces that have the gate.

How to decide

For another retirement-driven catalog change, see Haiku 4.5 retirement and the Sume agent model row.

• Need the model by name in an API call to Sume: not supported; sume-agent is the only value.
• Need GLM in a chat in Sume: look for GLM 5.3 Flash in the picker.
• Need a faster GLM tier: read the vendor or host page for that tier, not this catalog.
• Need cost control on either path: generation_spend_cap_usd or max_spend_usd.

Why the name matters in a search

People type both names because hosts use different labels for lighter or faster tiers of the same family. A label on one provider's page is not evidence of a model on another's. Sume's catalog entry is a concrete string, z-ai/glm-5.3-flash, which you can check against OpenRouter's listing yourself.

If you are comparing GLM options for an agent, compare on the same terms: context, output limit, tool support and price, each from the provider you will call. Do not carry a number from one host to another.