Z.ai models and APIs

About Z.ai

Z.ai's GLM families cover the long-read, long-answer middle of the text catalogue. All three publish a single chat task with a 1,048,576-token context window.

GLM 5.3 reads up to 1,048,576 tokens in one call and returns its reasoning in up to 131,072, which is a large reply ceiling for the rate. GLM 5.3 Flash keeps the same window and the same 131,072-token ceiling on the cheaper lane, and is the one to try first for volume. GLM 5.2 is the earlier family with the same window and ceiling, kept available so an existing integration does not have to move on someone else's schedule.

These three are close enough in shape that the honest way to choose is to run the same fixture against each and compare the result rather than the spec sheet. Start with 5.3 Flash, move to 5.3 when answer quality is the constraint, and pin 5.2 only if you have a reason to. Filtering tiers differ across the line, so check the tier on the family page before routing a sensitive workload.