OpenAI Codex Caught Secretly Altering Text, Possibly Linked to SynthID Watermarking

cephaloform · x · 2026-08-12

A developer reported that when asking OpenAI Codex to output source text verbatim, the model automatically swapped synonyms and mildly paraphrased parts of the content.

When confronted, Codex claimed it was genuinely surprised and had not intentionally modified the text. This behavior might be related to OpenAI's adoption of Google's SynthID text watermarking technology, which they signed on to use in May.

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