Follow-up to the cherry-picked #68258 base: the cross-session-stable
prefix (_cached_system_prompt_static) was only recorded on fresh
builds, so two paths silently degraded to the legacy single-breakpoint
layout (flagged in review of #68258/#69341/#69704):
- Session restore: gateway surfaces build a fresh AIAgent per turn and
restore the persisted prompt verbatim from the session DB; the static
prefix stayed None from turn 2 onward, flip-flopping the wire layout.
- Post-compression cached-prompt reuse: _invalidate_system_prompt()
clears the static prefix, and the keep-cached-prompt branch never
restored it.
Both sites now reconstruct the stable tier and adopt it ONLY when the
authoritative prompt string literally startswith() it — stable-tier
drift (skills edited, identity changed) falls back to the legacy layout
with the stored bytes untouched. Fail-open on any builder error. The
restore-path rebuild is gated on _use_prompt_caching so non-Anthropic
routes skip it entirely.
Refs #68191
Co-authored-by: JonthanaHanh <92574114+JonthanaHanh@users.noreply.github.com>
Co-authored-by: joaomarcos <joaomarcosdias444@gmail.com>
Co-authored-by: webtecnica <webtecnica@users.noreply.github.com>
teknium1
18af81bb5b