GPT-5.4 quirk: one diacritic changes output rate by 47%

rayanpal_ · reddit · 2026-08-25

A study on GPT-5.4 found that adding or removing diacritics on specific Hebrew and Arabic characters in the system prompt drastically changes compliance rates, jumping from 47.3% to 94.3%. This phenomenon reveals extreme sensitivity to specific character features, potentially linked to internal tokenization or safety mechanisms.

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