Module: Xeno::Compaction

Included in:

TurnRunner

Defined in:

lib/xeno/compaction.rb

Overview

Summarize-and-replace compaction, mixed into TurnRunner and executed as a claimed turn (kind: "compaction"). Riding the turn machinery buys the hard properties for free: the claim CAS makes it exclusive, session ordering queues it behind an active or parked turn, the heartbeat covers the summary model call, and a crash replays it (the applied result is recorded on the turn row, so replay never compacts twice).

Shape: the system prompt survives untouched; the most recent compaction_tail_turns user-anchored turns survive verbatim (a tail cut at a user row can never separate an assistant's tool calls from their results); everything between is summarized by a throwaway model call (the active model, never persisted) and REPLACED — the summary is written into the earliest compacted row so both id- and created_at- ordering keep it in place, and the remaining rows are destroyed newest-first (results before the tool_calls they reference).

Constant Summary

SUMMARY_PREFIX =

"[Conversation summary — earlier messages were compacted]".freeze

COMPACTION_PROMPT =

<<~PROMPT.freeze
  You are compacting an agent conversation to reclaim context space.
  Write a dense summary of the transcript below; it will REPLACE those
  messages permanently. Separate completed work and decisions from
  remaining or open work. Retain every constraint, preference, fact,
  identifier, amount, and reference a future turn could need. Output
  only the summary text.
PROMPT