One env var change broke ticket tagging: GLM 5.3 no longer accepts thinking off

sweetcake_1530 · reddit · 2026-09-29

A solid incident postmortem: a support-ticket tagging service ran on GLM 5.2 with thinking disabled. After a dev bumped a shared env var to GLM 5.3 — which no longer accepts thinking disabled — every tagging request failed. Fixing the parameter first made things worse: someone deleted the flag entirely, requests resumed but the queue ballooned as the model defaulted to deepest reasoning on every ticket. Setting effort to low restored normal speed. Lessons: config tweaks skip code review, mocked unit tests passed throughout the outage, and nothing ever sent real requests with production settings. Fixes include a dedicated env var and a test hitting the real API with production parameters.

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