describeEvent relies on ev.getPrevContent() to distinguish "joined" vs. "profile update", "kicked" vs. "invite withdrawn", and "banned"/"unbanned" transitions. prev_content for m.room.member events is reliably populated by the SDK for live, forward-synced events, but is not guaranteed to be present on events fetched via mx.paginateEventTimeline(..., { backwards: true }) (the mechanism handleLoadMore uses to backfill this log), since the homeserver's /messages response does not always include unsigned.prev_content for historical state events. When prevContent comes back empty for a paginated (i.e. essentially all, since state events are rare in the initial sync window per the code's own comment) event, describeEvent's membership === 'join' branch treats prevMembership === undefined the same as a fresh invite/knock-based join, and a leave with no prior context falls through to the generic "was kicked by" case — potentially mislabeling e.g. a voluntary-leave-then-rejoin or a rescinded-then-reissued invite as a kick.
How to trigger
Load older mod-log history (click "Load more") in a room where the historical /messages response for m.room.member events lacks unsigned.prev_content (varies by homeserver implementation) — some join/leave entries can show the wrong description.
Suggested fix
When prevContent is empty/undefined for a paginated event, fall back to a neutral phrasing ("membership changed to ") rather than assuming the same defaults used for live events, or fetch the member's actual prior state via /state at that point in the timeline if precision matters.
Filed from the September 2026 client audit (branch lotus @ 4bea4895).
**Severity:** low · **Type:** bug · **Confidence:** medium
**Location:** `src/app/features/room-settings/RoomActivityLog.tsx:51-170, 333-349`
### Problem
`describeEvent` relies on `ev.getPrevContent()` to distinguish "joined" vs. "profile update", "kicked" vs. "invite withdrawn", and "banned"/"unbanned" transitions. `prev_content` for `m.room.member` events is reliably populated by the SDK for live, forward-synced events, but is not guaranteed to be present on events fetched via `mx.paginateEventTimeline(..., { backwards: true })` (the mechanism `handleLoadMore` uses to backfill this log), since the homeserver's `/messages` response does not always include `unsigned.prev_content` for historical state events. When `prevContent` comes back empty for a paginated (i.e. essentially all, since state events are rare in the initial sync window per the code's own comment) event, `describeEvent`'s `membership === 'join'` branch treats `prevMembership === undefined` the same as a fresh invite/knock-based join, and a `leave` with no prior context falls through to the generic "was kicked by" case — potentially mislabeling e.g. a voluntary-leave-then-rejoin or a rescinded-then-reissued invite as a kick.
### How to trigger
Load older mod-log history (click "Load more") in a room where the historical `/messages` response for `m.room.member` events lacks `unsigned.prev_content` (varies by homeserver implementation) — some join/leave entries can show the wrong description.
### Suggested fix
When `prevContent` is empty/undefined for a paginated event, fall back to a neutral phrasing ("membership changed to <X>") rather than assuming the same defaults used for live events, or fetch the member's actual prior state via `/state` at that point in the timeline if precision matters.
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_Filed from the September 2026 client audit (branch `lotus` @ 4bea4895)._
jared
added this to the Audit 2026-09 · Medium & Low milestone 2026-09-12 01:51:32 -04:00
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Severity: low · Type: bug · Confidence: medium
Location:
src/app/features/room-settings/RoomActivityLog.tsx:51-170, 333-349Problem
describeEventrelies onev.getPrevContent()to distinguish "joined" vs. "profile update", "kicked" vs. "invite withdrawn", and "banned"/"unbanned" transitions.prev_contentform.room.memberevents is reliably populated by the SDK for live, forward-synced events, but is not guaranteed to be present on events fetched viamx.paginateEventTimeline(..., { backwards: true })(the mechanismhandleLoadMoreuses to backfill this log), since the homeserver's/messagesresponse does not always includeunsigned.prev_contentfor historical state events. WhenprevContentcomes back empty for a paginated (i.e. essentially all, since state events are rare in the initial sync window per the code's own comment) event,describeEvent'smembership === 'join'branch treatsprevMembership === undefinedthe same as a fresh invite/knock-based join, and aleavewith no prior context falls through to the generic "was kicked by" case — potentially mislabeling e.g. a voluntary-leave-then-rejoin or a rescinded-then-reissued invite as a kick.How to trigger
Load older mod-log history (click "Load more") in a room where the historical
/messagesresponse form.room.memberevents lacksunsigned.prev_content(varies by homeserver implementation) — some join/leave entries can show the wrong description.Suggested fix
When
prevContentis empty/undefined for a paginated event, fall back to a neutral phrasing ("membership changed to ") rather than assuming the same defaults used for live events, or fetch the member's actual prior state via/stateat that point in the timeline if precision matters.Filed from the September 2026 client audit (branch
lotus@4bea4895).