fix(session): prevent double compaction after auto-compact#26484
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sgfvamll wants to merge 1 commit into
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fix(session): prevent double compaction after auto-compact#26484sgfvamll wants to merge 1 commit into
sgfvamll wants to merge 1 commit into
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The following comment was made by an LLM, it may be inaccurate: Potential Related PR Found:
This PR appears to be related as it also addresses double compaction issues in sessions. You should verify if PR #26235 overlaps with the fix in PR #26484 or if they address different scenarios of the same problem. |
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Thanks for updating your PR! It now meets our contributing guidelines. 👍 |
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After compaction, filterCompacted retains tail assistant messages with stale cumulative token counts. The backward scan picks up these retained tails as lastFinished, and the overflow pre-check fires a second compaction immediately. Add a guard: only trigger auto-compaction when lastFinished is newer than the last compaction user message. Retained tails have older IDs, so they fail this check. Resolves anomalyco#26230 Resolves anomalyco#20621
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I'm not sure if the root cause analysis is right. But it fixed the issue I encountered. May serve as a workround. |
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Issue for this PR
Resolves #26230
Resolves #20621
Type of change
What does this PR do?
After auto-compaction,
filterCompactedretains tail assistant messages that carry stale cumulative token counts (~100K). The backward scan in the prompt loop picks up these retained tails aslastFinished, and the overflow pre-check immediately fires a second compaction — every single time. This wastes tokens and doubles Copilot request consumption.Root cause: The backward scan at
prompt.ts:1418-1426searches from the end offilterCompacted's output and breaks as soon as it findslastUser+lastFinished. After compaction, the output is:The scan finds
lastUser=[21] andlastFinished=[20] (a retained tail), then breaks — never reaching the compaction part at [0]. Sincetasksis empty, the compaction task handler is skipped. The pre-check then seeslastFinishedwith stale 103K tokens,isOverflowreturns true, and a second compaction fires.Fix: Add a guard that only triggers the overflow pre-check when
lastFinishedis newer than the last compaction user message. Retained tails have IDs older than the compaction user, so they fail this check.4-line production change in
packages/opencode/src/session/prompt.ts.How did you verify your code works?
filterCompactedfunction and traced the exact output ordering and backward scan behaviorbun typecheck— cleanbun test test/session/prompt.test.ts --test-name-pattern "double-compact"— 1 passScreenshots / recordings
N/A — no UI changes.
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