feat(polls): "See who voted" — per-answer voter list

The poll card showed vote counts but never who voted, even though
computePollState already parses a sender for every response. Surface it:

- tallyResponses now also returns voters: Map<answerId, senderId[]>, built in the
  same latest-response-per-sender loop as the counts, so voters can never disagree
  with the numbers (voters.get(id).length === counts.get(id)). +5 unit tests.
- PollContent adds a "Show who voted" toggle, shown only when results are visible
  (disclosed live, or undisclosed after end — so a secret ballot stays secret).
  When on, each answer lists its voters' display names (getMemberName), rendered
  as a sibling of the answer button so the radiogroup keyboard model is untouched.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

LOTUS_FEATURES.md

@@ -864,10 +864,11 @@ player.kick).
 
 - **Vote / change / clear** in place — sends stable `m.poll.response` (`m.selections`); latest response per voter wins; clearing removes you from the tally. Multi-choice enforces `max_selections` ("Select up to N").
 - **Disclosed vs undisclosed** — undisclosed polls hide counts/percentages/bars (and the vote total) until the poll ends; disclosed polls show live results.
+- **See who voted** — a "Show who voted" toggle (shown only when results are visible, i.e. disclosed live or undisclosed-after-end) reveals the voter names under each answer. The voter list rides the same tally as the counts (`voters: Map<answerId, senderId[]>` populated in `tallyResponses`'s latest-response-per-sender loop), so it can never disagree with the numbers; a re-vote moves the voter, and a cleared vote drops them. Names via `getMemberName`; undisclosed polls stay secret until close.
 - **End a poll** — the poll's creator or a moderator (redact power) can end it via an inline confirm; sends stable `m.poll.end`. Ended polls lock voting, show "Poll closed · Final results", reveal results, and highlight the winner(s) (ties supported). Only responses cast on/before the end event count.
 - **Cross-client** — reads **both** the stable (`m.poll`/`m.id`/`m.selections`) and unstable (`org.matrix.msc3381.poll.*`) wire formats by hand (matrix-js-sdk 41.7.0's poll parsers only speak unstable), and uses the SDK `Poll` model for end-event validation (creator / redact-PL) + before-end response filtering. Polls authored in Element render/vote/end correctly and vice-versa.
 - **Accessibility** — `radiogroup`/`radio` (single, with arrow-key roving) or `group`/`checkbox` (multi) semantics, `aria-checked`/`aria-disabled`, winner announced to AT.
-- Pure tally/visibility/winner + wire-format parsing live in `utils/poll.ts` (+ `poll.test.ts`, 14 tests incl. the stable/unstable round-trip).
+- Pure tally/visibility/winner/voters + wire-format parsing live in `utils/poll.ts` (+ `poll.test.ts`, 18 tests incl. the stable/unstable round-trip and voter attribution).
 
 ### Voice Message Playback (waveform + speed)
 

src/app/components/message/content/PollContent.tsx

@@ -4,6 +4,7 @@ import { Box, Chip, color, config, Icon, Icons, Text, toRem } from 'folds';
 import { RelationsEvent } from 'matrix-js-sdk/lib/models/relations';
 import { MatrixEvent, Room, RoomEvent, PollEvent } from 'matrix-js-sdk';
 import { useMatrixClient } from '../../../hooks/useMatrixClient';
+import { getMemberName } from '../../../utils/room';
 import {
   ParsedPoll,
   PollResponse,
@@ -16,7 +17,12 @@ import {
   winningAnswerIds,
 } from '../../../utils/poll';
 
-const EMPTY_TALLY: PollTally = { counts: new Map(), myVotes: new Set(), total: 0 };
+const EMPTY_TALLY: PollTally = {
+  counts: new Map(),
+  voters: new Map(),
+  myVotes: new Set(),
+  total: 0,
+};
 
 type PollState = { tally: PollTally; isEnded: boolean };
 
@@ -106,6 +112,7 @@ export function PollContent({
   const [pending, setPending] = useState<Set<string> | null>(null);
   const [confirmEnd, setConfirmEnd] = useState(false);
   const [ending, setEnding] = useState(false);
+  const [showVoters, setShowVoters] = useState(false);
 
   const refresh = useCallback(() => {
     if (!eventId || !parsed) return;
@@ -194,8 +201,11 @@ export function PollContent({
   const canEnd = !!eventId && !isEnded && (senderId === mx.getUserId() || canRedact);
 
   const myVotes = pending ?? tally.myVotes;
-  const { counts, total } = tally;
+  const { counts, total, voters } = tally;
   const winners = isEnded && showResults ? new Set(winningAnswerIds(counts)) : new Set<string>();
+  // Voter identities are shown under the same rule as the counts: disclosed polls
+  // reveal them live, undisclosed polls only once ended.
+  const canShowVoters = showResults && total > 0;
 
   const handleVote = (answerId: string) => {
     if (!roomId || !eventId || !canVote) return;
@@ -320,8 +330,8 @@ export function PollContent({
               ? 0
               : -1;
           return (
+            <React.Fragment key={id}>
             <button
-              key={id}
               type="button"
               data-poll-answer
               data-selected={selected}
@@ -416,9 +426,32 @@ export function PollContent({
                 )}
               </span>
             </button>
+            {showVoters && canShowVoters && (voters.get(id)?.length ?? 0) > 0 && (
+              <Text
+                size="T200"
+                priority="300"
+                style={{ padding: `0 ${config.space.S300} ${config.space.S100}` }}
+              >
+                {(voters.get(id) ?? []).map((s) => getMemberName(room, s)).join(', ')}
+              </Text>
+            )}
+            </React.Fragment>
           );
         })}
       </Box>
+      {canShowVoters && (
+        <Box>
+          <Chip
+            variant={showVoters ? 'Primary' : 'SurfaceVariant'}
+            radii="Pill"
+            aria-pressed={showVoters}
+            onClick={() => setShowVoters((v) => !v)}
+            before={<Icon size="50" src={Icons.User} />}
+          >
+            <Text size="T200">{showVoters ? 'Hide voters' : 'Show who voted'}</Text>
+          </Chip>
+        </Box>
+      )}
       <Box alignItems="Center" justifyContent="SpaceBetween" gap="200">
         <Text size="T200" priority="300" style={{ minWidth: 0 }}>
           <i>{footerNote}</i>

src/app/utils/poll.test.ts

@@ -70,6 +70,51 @@ test('tallyResponses: re-voting after an empty clear counts the newest non-empty
   assert.equal(total, 1);
 });
 
+test('tallyResponses: voters list the senders per answer, consistent with counts', () => {
+  const responses: PollResponse[] = [
+    { sender: '@a:s', ts: 1, answerIds: ['1'] },
+    { sender: '@b:s', ts: 1, answerIds: ['1'] },
+    { sender: '@c:s', ts: 1, answerIds: ['2'] },
+  ];
+  const { counts, voters } = tallyResponses(responses, me);
+  assert.deepEqual([...(voters.get('1') ?? [])].sort(), ['@a:s', '@b:s']);
+  assert.deepEqual(voters.get('2'), ['@c:s']);
+  // voters must always agree with counts
+  for (const [id, list] of voters) {
+    assert.equal(list.length, counts.get(id));
+  }
+});
+
+test('tallyResponses: a re-vote moves the sender to the new answer in voters', () => {
+  const responses: PollResponse[] = [
+    { sender: '@a:s', ts: 1, answerIds: ['1'] },
+    { sender: '@a:s', ts: 5, answerIds: ['2'] }, // changed vote
+  ];
+  const { voters } = tallyResponses(responses, me);
+  assert.equal(voters.get('1'), undefined); // no longer under the old answer
+  assert.deepEqual(voters.get('2'), ['@a:s']);
+});
+
+test('tallyResponses: a cleared latest response drops the sender from every voter list', () => {
+  const responses: PollResponse[] = [
+    { sender: '@a:s', ts: 1, answerIds: ['1', '2'] },
+    { sender: '@a:s', ts: 2, answerIds: [] }, // cleared
+  ];
+  const { voters } = tallyResponses(responses, me);
+  assert.equal(voters.get('1'), undefined);
+  assert.equal(voters.get('2'), undefined);
+});
+
+test('tallyResponses: multi-select lists a sender under each chosen answer', () => {
+  const responses: PollResponse[] = [
+    { sender: '@a:s', ts: 1, answerIds: ['1', '3'] },
+    { sender: '@b:s', ts: 1, answerIds: ['3'] },
+  ];
+  const { voters } = tallyResponses(responses, me);
+  assert.deepEqual(voters.get('1'), ['@a:s']);
+  assert.deepEqual([...(voters.get('3') ?? [])].sort(), ['@a:s', '@b:s']);
+});
+
 test('resultsVisible: disclosed always, undisclosed only when ended', () => {
   assert.equal(resultsVisible(false, false), true); // disclosed, open
   assert.equal(resultsVisible(false, true), true); // disclosed, ended

src/app/utils/poll.ts

@@ -102,6 +102,9 @@ export type PollResponse = {
 export type PollTally = {
   /** answerId → number of voters who selected it. */
   counts: Map<string, number>;
+  /** answerId → the sender ids who selected it (latest response per sender). Always
+   * consistent with `counts` — `voters.get(id).length === counts.get(id)`. */
+  voters: Map<string, string[]>;
   /** answer ids the current user selected (from their latest response). */
   myVotes: Set<string>;
   /** number of distinct voters counted. */
@@ -126,6 +129,7 @@ export function tallyResponses(responses: PollResponse[], myUserId: string): Pol
   }
 
   const counts = new Map<string, number>();
+  const voters = new Map<string, string[]>();
   const myVotes = new Set<string>();
   let total = 0;
   for (const [sender, r] of latestBySender) {
@@ -133,11 +137,14 @@ export function tallyResponses(responses: PollResponse[], myUserId: string): Pol
     total += 1;
     for (const id of r.answerIds) {
       counts.set(id, (counts.get(id) ?? 0) + 1);
+      const list = voters.get(id);
+      if (list) list.push(sender);
+      else voters.set(id, [sender]);
       if (sender === myUserId) myVotes.add(id);
     }
   }
 
-  return { counts, myVotes, total };
+  return { counts, voters, myVotes, total };
 }
 
 /**