GLM-5.3-Flash is live on Fireworks on day… 2 Why? Because we take quality very seriously. We found a benchmark discrepancy we couldn’t expla…

GLM-5.3-Flash is live on Fireworks on day… 2 Why? Because we take quality very seriously. We found a benchmark discrepancy we couldn’t explain, so we delayed the launch to investigate. Day 0 (Wed): we saw 2x longer thinking on reasoning-heavy benchmarks (AIME & GPQA) for open source engines compared with @Zai_org API. Same scores, worse token efficiency. Agentic benchmarks looked good. We decided to investigate further, as overthinking might become a quality problem if max_tokens are reached Day 1 (Thu): as other non-official providers launched, their APIs had thinking in the range of open-source engines: longer than http://Z.ai. We launched a private preview endpoint with disclaimers to a few customers and worked with them to assess quality Day 2 (Fri): the official http://Z.ai API updates. We rerun benchmarks: reasoning is now similarly long, consistent with vllm/sglang. Rest of the benchmarks, both public and internal, check out too. We launched GLM-5.3-Flash publicly: https://fireworks.ai/models/fireworks/glm-5p3-flash More details below

Source: Sonya Huang (X) | 2026-08-29

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