The agent rebuilds context from DB each turn and didn't know the user manually
edited the open page since its last response, so it could overwrite those edits.
Add a per-turn ephemeral <page_changed> note in the system prompt (twin of
INTERRUPT_NOTE, self-clearing) carrying a unified Markdown diff of what changed
since the END of the agent's previous turn.
- New ai_chat_page_snapshots table (migration + hand-declared db.d.ts/entity
types) storing the page Markdown per (chat,page) at each turn's end.
- Pure computePageChange util (whitespace-normalized unified diff via the
existing jsdiff dep, 6KB cap + getPage hint).
- Turn start: if the open page's updatedAt moved past the snapshot, diff current
vs snapshot; non-empty -> PAGE_CHANGED_NOTE in the safety sandwich.
- Turn end: upsert the snapshot on EVERY terminal path (onFinish/onError/onAbort,
once) so the agent's own edits are excluded by construction even on aborted
turns.
All best-effort (never breaks/latency-regresses a turn); fast path when updatedAt
is unchanged. Server-only.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
agent_coder
8c5b57ebfa