Mitsuhiko: Pi's hookable system prompt makes long-term prefix stability the hard problem

mitsuhiko · x · 2026-09-02

Armin Ronacher explains Pi's design: a hookable, non-persisted system prompt, which makes keeping the prefix stable over long sessions trickier than model switching. He also notes that today, loading or removing a skill mid-session drops reasoning, and making Pi compatible with that world is a much bigger change he wants to get right.

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