portalbackfill: keep never-bridged messages in forward backfill dedup#517
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portalbackfill: keep never-bridged messages in forward backfill dedup#517Fizzadar wants to merge 2 commits into
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Forward backfill could permanently lose messages when a reconnect snapshot advanced the sync cursor past threads it didn't include, leaving mid-timeline gaps older than the portal anchor. Skip the forward timestamp prefix-trim in cutoffMessages when AggressiveDeduplication is set so the ID-based dedup pass decides what is already bridged, retaining never-bridged messages older than the anchor.
Fizzadar
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Jun 16, 2026
| messages = messages[cutoff+1:] | ||
| } | ||
| } else { | ||
| } else if !forward { |
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Should we apply the aggressiveDedup guard here too so both forward/backward are the same (aggressive is forced and any prefix shortcuts disabled).
Fizzadar
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See mautrix/meta#286
But basically - aggressive dupe should probably not do prefix deleting as it breaks the "check each message" approach, which in meta's case can lead to permanently lost messages.