pi's `transformContext` hook fired on every LLM call but returned
the transcript unchanged, so a long-running agent paid per-token
for its entire history on every turn. The README promised "sessions
persist + auto-compact" but the main loop had no compaction wired
in at all — only rotation at the long-cycle boundary.
`context-compactor` closes that gap. A pure, provider-free function
estimates tokens (~4 chars/token), short-circuits below a 120K
threshold, and on overflow keeps the last 20 messages verbatim
while collapsing older ones into a single "context summary" user
turn. The summary preserves the original task and the first twelve
assistant highlights so the agent has continuity without forwarding
every historical turn.
Compaction is non-destructive: the Agent's in-memory transcript
and the SQLite session store still hold the full history, feeding
UI timelines and audit. Only the LLM payload shrinks. Rotation
remains the long-cycle boundary (separate commit) — compaction is
what keeps each individual LLM call within budget.
ZacharyZhang-NY