Function insertCompactionMarker

packages/cli/src/commands/migrate.ts:665–699

(
    entries: PiJson[],
    boundaryEntryId: string | undefined,
)

}

function insertCompactionMarker(
    entries: PiJson[],
    boundaryEntryId: string | undefined,
): CompactionMarkerResult {
    if (boundaryEntryId === undefined) return { written: false };

    const boundaryIndex = entries.findIndex((entry) => entry.id === boundaryEntryId);
    if (boundaryIndex < 0) return { written: false };

    const firstKept = entries[boundaryIndex + 1];
    if (!firstKept?.id) return { written: false };

    const compactedPrefixChars = entries
        .slice(0, boundaryIndex + 1)
        .reduce((total, entry) => total + JSON.stringify(entry.message ?? "").length, 0);
    const compactionId = shortId();
    const marker: PiJson = {
        type: "compaction",
        id: compactionId,
        parentId: boundaryEntryId,
        timestamp: String(entries[boundaryIndex].timestamp),
        summary: MIGRATION_COMPACTION_SUMMARY,
        firstKeptEntryId: firstKept.id,
        tokensBefore: Math.ceil(compactedPrefixChars / 4),
        fromHook: true,
    };

    firstKept.parentId = compactionId;
    entries.splice(boundaryIndex + 1, 0, marker);
    return {
        written: true,
        boundaryEntryId,
        firstKeptEntryId: firstKept.id as string,
    };
}

/**
 * Copy compartments + session_facts from the source OpenCode session