Anthropic engineer says Claude's writing worsened because models learned to write for AI
An attributed explanation: RL rewards favoring AI comprehension produced dense prose; Opus 5.5 reportedly rebalances, with no benchmark behind it.
Original event 2026-09-23
Jackson Kernion, an Anthropic engineer working on Claude fine-tuning, attributes the regression in Claude's writing to the reinforcement-learning reward structure: some rewards optimize for comprehension by other AI models, and the more training leans on math and code, the more the model learns to write for AI rather than people, producing what humans experience as "overly-dense info dumps."
Per The Decoder's relay of his X posts, he compares the resulting "Claudeish" style to habits formed inside a closed communication group, and says Opus 4.6 remains Anthropic's last good writing model.
He says Opus 5.5 strikes a better balance but does not claim it surpasses the older model. These are his personal statements, with no evaluation data behind them.