GPT-5.4 Reasoning Model Glitch: Outputs Georgian Script Mid-German Word

kumard3 · reddit · 2026-08-09

A developer recently encountered a bizarre glitch where gpt-5.4 suddenly output half a German word in Georgian script mid-sentence.

Investigation: Initial suspicions of pipeline corruption were ruled out by trace logs, which showed exact output length matches and zero string replacements. The model simply sampled cross-script phonetic tokens on its own.
Temperature Ignored: The author noted that this generation of reasoning models appears to ignore the temperature parameter. Even set to 0, it samples at a default state, allowing rare cross-script swaps to slip through.
The Fix: Because this sits below the prompt layer, the team implemented a Latin-dominant output guard. It detects script anomalies, re-rolls once, and strips characters on a second failure. It occurred only twice in 4 days but remained invisible until a customer reported it.

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