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Compaction keeps a whole long exchange verbatim when the last user message is far behind the cut #54648
Description
Description
Summary compaction keeps the newest keep tokens (default 15,000) verbatim beside the summary. But recentStart in packages/core/src/session/compaction.ts then walks back to the newest user message before that cut, however far back it is. After one user message followed by a long run of tool calls, the whole run is kept.
Seen on a worker session (one message, then ~50 tool turns): the compaction kept 434k characters of recent (~108k tokens) and summarized 61k; the context was still at 57% of the ceiling afterwards. The next compaction, 16 minutes later, had no user message since the checkpoint, so the last branch of recentStart kept everything and the summarizer re-read the previous checkpoint with those 434k characters inside (449k-character input). Over 9 consecutive compactions on two such sessions, 7 kept 1–3× the allowance. Headless or delegated runs that work for a long time on one message hit this every time.
Plugins
A compaction plugin that supplies the summary text. It does not touch recent; core picks the kept part before hooks run.
OpenCode version
2.0.24. recentStart is the same on dev (707de58) and v2.0.26.
Steps to reproduce
- Send one message that makes the agent run many tool calls (~40k tokens of tool output).
- Let auto compaction trigger, or run
/compact. - In the stored compaction row,
recentstarts at that user message and far exceedscompaction.keep.tokens.
Screenshot and/or share link
No response
Operating System
Fedora 44
Terminal
Ghostty
@superbiche · user · drafted with Claude Fable 5.1, reviewed before posting; the voice and decisions are mine.
Activity
opencode-agent commentedon Oct 11, 2026
Thanks for the detailed report and the measurements. I think this is a duplicate of #43250. It describes the same thing: the walk-back from the
keep.tokenscut to the newest user message has no limit, so a single prompt followed by a long tool run is kept verbatim inrecent. That issue already has measured cases from 2.0.15, 2.0.18 and 2.0.24 in one-prompt autonomous sessions.Possible duplicates and related issues, ordered by likelihood:
keep.tokensnot honoured because of the unbounded walk-back to the last user message in agent-driven sessionsrecent, which can make the context bigger than before compaction #51818: a related wayrecentgrows larger than intended (reasoning text kept inrecent)opencode runsessions, so long headless runs compact every ~10 minutes #47485: related symptom of long headless single-turn runs compacting again and againYour PR #54649 takes a different approach to the same bug. It would help to link it to #43250 as well, so maintainers can compare it with #53233. The bot will close this issue as a duplicate in 1 day unless you reply explaining how your problem is different.
opencode-agent commentedon Oct 12, 2026
We haven't heard back, so I'm closing this as a duplicate of #43250. That issue covers the same problem: the walk-back to the newest user message has no limit, so a long tool run after one prompt is kept whole in
recent, far pastcompaction.keep.tokens. Please follow #43250 for updates. PR #53233 targets it, and it would help to link your PR #54649 there too so maintainers can compare the two fixes. If your case turns out to be different, reply here and we can reopen. Thanks for the detailed measurements!