diff --git a/.changeset/collaboration-comment-thread-a11y-names-and-dates-3441.md b/.changeset/collaboration-comment-thread-a11y-names-and-dates-3441.md
new file mode 100644
index 000000000..aa1af89df
--- /dev/null
+++ b/.changeset/collaboration-comment-thread-a11y-names-and-dates-3441.md
@@ -0,0 +1,67 @@
+---
+'@object-ui/collaboration': patch
+'@object-ui/i18n': patch
+---
+
+Name `CommentThread`'s three emoji-only buttons, and follow the session language past the 7-day mark (objectui#3441)
+
+Two leftovers from objectstack#5506 / objectui#3424, in the same component. It
+is an exported, published component with no in-repo consumer, so both only ever
+bite an external host.
+
+**One — three controls with no authored accessible name.** Each comment's two
+quick-reaction buttons (`'👍'` and `'❤️'`) and the reply banner's dismiss button
+(`'✕'`) carried no `aria-label` and no `title`. The `+` reaction picker right
+beside them has had one since #3424 (`collaboration.addThumbsUp`), which is what
+makes these three an omission rather than a design choice.
+
+`aria-label`, not the `title` the `+` uses: a `button`'s accessible name is
+computed from its CONTENT (accname §2F) before the `title` tooltip is ever
+consulted (§2I), so on a button whose only child is a glyph a `title` decorates
+the mouse and leaves the name alone. What a screen reader read out was the
+codepoint — "thumbs up", "red heart", in English whatever the session language,
+and for U+2715 MULTIPLICATION X very often nothing at all.
+
+Three new keys in all ten packs: `collaboration.reactThumbsUp`,
+`collaboration.reactHeart`, `collaboration.cancelReply`.
+
+`reactThumbsUp` is deliberately NOT a reuse of `addThumbsUp`, even though both
+dispatch the same `onReaction(id, '👍')` today. `addThumbsUp` names the reaction
+bar's picker entry point, whose copy follows the picker if it ever picks; and on
+any comment that already has reactions the two controls are on screen together,
+so one shared key would put two visibly different buttons under one name.
+`cancelReply` rather than the generic `common.cancel` for the same reason — an
+accessible name has to say what is being cancelled (only the reply target is
+dropped; anything typed into the composer survives).
+
+**Two — the >= 7 day timestamp ignored the session language.** `formatTimestamp`
+ended in a bare `date.toLocaleDateString()`, i.e. the RUNTIME's locale, so a
+`zh` session read "6 天前" for a six-day-old comment and `8/1/2026` for an
+eight-day-old one.
+
+The fix passes the session `language`, but not straight through — that is the
+trap #3424 flagged and declined to walk into. `toLocaleDateString(tag)`
+canonicalizes its argument and throws `RangeError` on anything not well-formed
+per BCP 47, and the session language reaches the component verbatim: a host that
+configures `defaultLanguage: 'en_US'` (the POSIX spelling — well-formed-looking,
+and rejected) hands `Intl` a tag it refuses. That `RangeError` would land in
+`formatTimestamp`'s outer `catch`, whose fallback is `return iso`, replacing the
+date with a raw `2026-08-01T09:30:00.000Z` — worse than the un-localized date it
+set out to fix.
+
+So the absolute-date branch gets its own local `try`/`catch` that falls back to
+the no-argument call. A malformed tag degrades to exactly the previous
+behaviour (the runtime's own locale); the worst case of following the session
+language is the status quo, never a regression. A well-formed but unknown tag
+such as `xx-YY` does not throw at all — `Intl` resolves it to the default — so
+only genuinely malformed tags reach the guard. No date library, and no month or
+weekday copy in the locale packs: `Intl` already owns the per-locale ordering
+and separators.
+
+Tests assert the computed accessible name via `getByRole('button', { name })`
+rather than the presence of an attribute, which is the distinction the fix turns
+on, and pin that no button is left answering to a bare emoji. The malformed-tag
+case is recorded honestly as green on both sides of this change — `origin/main`
+never passed a tag anywhere, so it could not trip over a bad one; its
+counterfactual is the naive fix, and dropping the inner `catch` is what turns it
+red with the raw ISO string in the DOM.
diff --git a/packages/collaboration/src/CommentThread.tsx b/packages/collaboration/src/CommentThread.tsx
index b90b55507..9be2da61b 100644
--- a/packages/collaboration/src/CommentThread.tsx
+++ b/packages/collaboration/src/CommentThread.tsx
@@ -51,23 +51,57 @@ export interface CommentThreadProps {
   className?: string;
 }
 
+/**
+ * Absolute date for the >= 7d bucket, in the session language (objectui#3441).
+ *
+ * Has its OWN try/catch, deliberately not sharing `formatTimestamp`'s. The two
+ * catches recover from different things and must recover differently:
+ *
+ *  - `formatTimestamp`'s outer catch is for an input it cannot make sense of,
+ *    and its only honest fallback is to echo the raw `iso` back.
+ *  - a throw from here says nothing about the *date* — it says the LANGUAGE TAG
+ *    is malformed. `Date.prototype.toLocaleDateString(tag)` runs the tag through
+ *    `CanonicalizeLocaleList`, which raises `RangeError` for anything not
+ *    structurally well-formed per BCP 47 (`'en_US'`, `''`, `'zh CN'`). A
+ *    well-formed but unknown tag such as `'xx-YY'` does NOT throw — it resolves
+ *    to the runtime default — so only genuinely malformed tags reach the catch.
+ *
+ * Letting the tag's `RangeError` reach the outer catch is why this was left
+ * undone in objectui#3424: a bad tag would have turned a readable date into the
+ * raw `2026-08-01T09:30:00.000Z`, i.e. WORSE than the un-localized date it
+ * replaced. Falling back to the no-argument call restores exactly the previous
+ * behaviour (the runtime's own locale) for that path, so the worst case of
+ * following the session language is the status quo, never a regression.
+ *
+ * No date library, and no month/weekday copy in the locale packs: `Intl` is
+ * already in the runtime and owns the per-locale ordering and separators.
+ */
+function formatAbsoluteDate(date: Date, language: string): string {
+  try {
+    return date.toLocaleDateString(language);
+  } catch {
+    return date.toLocaleDateString();
+  }
+}
+
 /**
  * Relative age of a comment, in the session language.
  *
- * `t` is threaded in as a parameter rather than read from a hook: this runs
- * once per rendered comment from inside `renderComment`, and the buckets are
- * unchanged — only the words moved into the locale packs. Counts are
- * interpolated as STRINGS on purpose, so i18next skips its own plural
- * resolution (`needsPluralHandling` is false for a string `count`) and cannot
- * silently start looking for `_one`/`_other` variants this repo does not ship.
+ * `t` and `language` are threaded in as parameters rather than read from a
+ * hook: this runs once per rendered comment from inside `renderComment`, and
+ * the buckets are unchanged — only the words moved into the locale packs.
+ * Counts are interpolated as STRINGS on purpose, so i18next skips its own
+ * plural resolution (`needsPluralHandling` is false for a string `count`) and
+ * cannot silently start looking for `_one`/`_other` variants this repo does not
+ * ship.
  *
- * The >= 7d branch still uses the runtime's own `toLocaleDateString()`. That is
- * not a hardcoded English literal — it already follows the environment locale —
- * and pinning it to the session language is a separate change with its own
- * failure mode (an unrecognised tag throws `RangeError` straight into the
- * `catch` below, which would render the raw ISO string). Tracked separately.
+ * The >= 7d bucket follows the session language too (objectui#3441) — a `zh`
+ * session used to read "6 天前" for a six-day-old comment and `8/1/2026` for an
+ * eight-day-old one, because that branch called `toLocaleDateString()` with no
+ * argument and got the *runtime's* locale. See {@link formatAbsoluteDate} for
+ * why the tag gets its own guard instead of being handed straight in.
  */
-function formatTimestamp(iso: string, t: CollaborationTranslate): string {
+function formatTimestamp(iso: string, t: CollaborationTranslate, language: string): string {
   try {
     const date = new Date(iso);
     const now = new Date();
@@ -79,7 +113,7 @@ function formatTimestamp(iso: string, t: CollaborationTranslate): string {
     if (hours < 24) return t('collaboration.hoursAgo', { count: String(hours) });
     const days = Math.floor(hours / 24);
     if (days < 7) return t('collaboration.daysAgo', { count: String(days) });
-    return date.toLocaleDateString();
+    return formatAbsoluteDate(date, language);
   } catch {
     return iso;
   }
@@ -367,7 +401,7 @@ export function CommentThread({
   const [mentionIndex, setMentionIndex] = useState(0);
   const [sortOrder, setSortOrder] = useState<'newest' | 'oldest'>('oldest');
   const inputRef = useRef<HTMLTextAreaElement>(null);
-  const { t } = useCollaborationTranslation();
+  const { t, language } = useCollaborationTranslation();
 
   const filteredMentions = useMemo(() => {
     if (mentionQuery === null) return [];
@@ -511,7 +545,7 @@ export function CommentThread({
         // Header
         React.createElement('div', { style: styles.commentHeader },
           React.createElement('span', { style: styles.authorName }, comment.author.name),
-          React.createElement('span', { style: styles.timestamp }, formatTimestamp(comment.createdAt, t)),
+          React.createElement('span', { style: styles.timestamp }, formatTimestamp(comment.createdAt, t, language)),
           comment.updatedAt
             ? React.createElement('span', { style: styles.timestamp }, t('collaboration.edited'))
             : null,
@@ -569,13 +603,29 @@ export function CommentThread({
             style: styles.actionBtn,
             onClick: () => setReplyTo(comment.id),
           }, t('collaboration.reply')),
+          // Quick reactions (objectui#3441). Their only content is the emoji,
+          // and for a `button` the accessible name comes from CONTENT before it
+          // ever reaches `title` (accname §2F outranks §2I) — so these two were
+          // announced as the bare glyph: "thumbs up" / "red heart" at best,
+          // nothing at all where the SR has no name for the codepoint. Hence
+          // `aria-label`, which overrides content, rather than the `title` the
+          // `+` picker above uses.
+          //
+          // Their own key pair, NOT a reuse of `collaboration.addThumbsUp`: the
+          // `+` above happens to fire the same `onReaction(id, '👍')` today, but
+          // it is the reaction PICKER's entry point (`styles.reactionPicker`)
+          // whose copy follows the picker if it ever picks. Sharing one key
+          // would also give a comment that already has reactions two visible
+          // controls answering to one name.
           onReaction && React.createElement('button', {
             style: styles.actionBtn,
             onClick: () => onReaction(comment.id, '👍'),
+            'aria-label': t('collaboration.reactThumbsUp'),
           }, '👍'),
           onReaction && React.createElement('button', {
             style: styles.actionBtn,
             onClick: () => onReaction(comment.id, '❤️'),
+            'aria-label': t('collaboration.reactHeart'),
           }, '❤️'),
           isOwner && onEditComment && React.createElement('button', {
             style: styles.actionBtn,
@@ -649,9 +699,16 @@ export function CommentThread({
           ? t('collaboration.replyingTo', { name: replyToName })
           : t('collaboration.replyingToComment');
       })()),
+      // Dismisses the banner and clears the reply target (objectui#3441). Its
+      // content is U+2715 MULTIPLICATION X — a math symbol, not an icon with a
+      // name — so name-from-content gave a screen reader either nothing or
+      // "multiplication x". `aria-label` overrides it; `cancelReply` rather
+      // than the generic `common.cancel` because an accessible name has to say
+      // WHAT is being cancelled (the composer keeps its text either way).
       React.createElement('button', {
         style: styles.actionBtn,
         onClick: () => setReplyTo(null),
+        'aria-label': t('collaboration.cancelReply'),
       }, '✕'),
     ),
     // Input area
diff --git a/packages/collaboration/src/__tests__/comment-thread-i18n.test.tsx b/packages/collaboration/src/__tests__/comment-thread-i18n.test.tsx
index 82908ae6f..1dc596e90 100644
--- a/packages/collaboration/src/__tests__/comment-thread-i18n.test.tsx
+++ b/packages/collaboration/src/__tests__/comment-thread-i18n.test.tsx
@@ -292,6 +292,188 @@ describe('CommentThread per-comment actions (objectstack#5506)', () => {
   });
 });
 
+/**
+ * objectui#3441 — the three emoji-only controls objectstack#5506 left unnamed.
+ *
+ * These assert the computed ACCESSIBLE NAME (`getByRole('button', { name })`,
+ * which runs dom-accessibility-api's accname implementation), not the presence
+ * of an attribute. That distinction is the whole point of the fix: for a
+ * `button`, name-from-content (accname §2F) is consulted BEFORE the `title`
+ * tooltip (§2I), so hanging a `title` on `'👍'` the way the `+` picker does
+ * would have left the computed name as the glyph. `aria-label` is the only one
+ * of the three that outranks content.
+ *
+ * ── Direction ─────────────────────────────────────────────────────────────
+ * RED before / GREEN after in EVERY language, `en` included — unlike the
+ * copy-pin cases above, these names did not exist in any locale on
+ * `origin/main`, so there is no "English was already right" half here. The
+ * `queryAllByRole(… { name: '👍' })` assertions are the mirror image: they
+ * pass ONLY after the fix, because the glyph was the name until `aria-label`
+ * displaced it.
+ */
+describe('CommentThread emoji-only control names (objectui#3441)', () => {
+  it('names the two quick-reaction buttons in English', () => {
+    renderThread('en');
+
+    expect(screen.getAllByRole('button', { name: 'React with thumbs up' }).length).toBe(2);
+    expect(screen.getAllByRole('button', { name: 'React with heart' }).length).toBe(2);
+  });
+
+  it('names the two quick-reaction buttons in the session language', () => {
+    renderThread('zh');
+
+    expect(screen.getAllByRole('button', { name: '以点赞回应' }).length).toBe(2);
+    expect(screen.getAllByRole('button', { name: '以爱心回应' }).length).toBe(2);
+    expect(screen.queryAllByRole('button', { name: 'React with thumbs up' })).toHaveLength(0);
+  });
+
+  it('names them in German too, so the keys are really in the packs', () => {
+    renderThread('de');
+
+    expect(screen.getAllByRole('button', { name: 'Mit Daumen hoch reagieren' }).length).toBe(2);
+    expect(screen.getAllByRole('button', { name: 'Mit Herz reagieren' }).length).toBe(2);
+  });
+
+  /**
+   * The bug itself: with no `aria-label`, the button's only content IS its
+   * name. A screen reader announced "thumbs up button" / "red heart button" —
+   * the emoji's Unicode name, in English, whatever the session language.
+   */
+  it('no longer leaves a button whose accessible name is the bare emoji', () => {
+    renderThread('zh');
+
+    expect(screen.queryAllByRole('button', { name: '👍' })).toHaveLength(0);
+    expect(screen.queryAllByRole('button', { name: '❤️' })).toHaveLength(0);
+  });
+
+  /**
+   * `cancelReply`, not the generic `common.cancel`: an accessible name has to
+   * say WHAT is being cancelled. Only the reply target is dropped — anything
+   * already typed into the composer survives.
+   */
+  it('names the reply-banner dismiss button in the session language', () => {
+    renderThread('zh');
+
+    // The banner only exists once a reply target is picked.
+    fireEvent.click(screen.getAllByText('回复')[0]);
+
+    expect(screen.getByRole('button', { name: '取消回复' })).toBeTruthy();
+    // U+2715 MULTIPLICATION X — a math symbol with no reliable spoken name.
+    expect(screen.queryAllByRole('button', { name: '✕' })).toHaveLength(0);
+  });
+
+  it('names the reply-banner dismiss button in English', () => {
+    renderThread('en');
+
+    fireEvent.click(screen.getAllByText('Reply')[0]);
+
+    expect(screen.getByRole('button', { name: 'Cancel reply' })).toBeTruthy();
+  });
+
+  /**
+   * The `+` picker keeps `collaboration.addThumbsUp` (objectstack#5506) and the
+   * quick 👍 gets its own `reactThumbsUp`, even though both dispatch the same
+   * `onReaction(id, '👍')` today. This case is what pins the two apart: on a
+   * comment that already has reactions both controls are on screen at once, so
+   * sharing one key would put two visibly different controls under one name.
+   */
+  it('keeps the reaction-bar picker distinct from the quick thumbs-up', () => {
+    renderThread('en');
+
+    expect(screen.getByTitle('Add thumbs up')).toBeTruthy();
+    expect(screen.queryAllByRole('button', { name: 'Add thumbs up' })).toHaveLength(0);
+    expect(screen.getAllByRole('button', { name: 'React with thumbs up' }).length).toBe(2);
+  });
+});
+
+/**
+ * objectui#3441, part two — the >= 7d bucket follows the SESSION language.
+ *
+ * `formatTimestamp`'s last branch called `toLocaleDateString()` with no
+ * argument, i.e. the RUNTIME's locale. In a `zh` console a six-day-old comment
+ * read "6 天前" and a seven-day-old one read `8/1/2026`.
+ *
+ * ── Direction ─────────────────────────────────────────────────────────────
+ * The `zh` and `de` cases are RED before / GREEN after: on `origin/main` every
+ * session renders the same runtime-default string. The `en` case is green on
+ * both sides in a runtime whose default locale is already `en-US`, and it is
+ * kept as a copy pin, not offered as evidence.
+ */
+describe('CommentThread absolute timestamps (objectui#3441)', () => {
+  const eightDaysAgo = new Date(Date.now() - 8 * 24 * 60 * 60 * 1000);
+  const oldComment: Comment = {
+    id: 'old',
+    author: alice,
+    content: 'From last week.',
+    mentions: [],
+    createdAt: eightDaysAgo.toISOString(),
+  };
+
+  const dateCell = () =>
+    Array.from(document.querySelectorAll('[data-comment-id="old"] span'))
+      .map((n) => n.textContent)
+      .filter((v): v is string => Boolean(v));
+
+  it('formats a week-old comment in the session language', () => {
+    renderThread('zh', { comments: [oldComment] });
+    expect(dateCell()).toContain(eightDaysAgo.toLocaleDateString('zh'));
+    cleanup();
+
+    renderThread('de', { comments: [oldComment] });
+    expect(dateCell()).toContain(eightDaysAgo.toLocaleDateString('de'));
+  });
+
+  /**
+   * Doubles as an ICU-availability assertion: on a runtime built without the
+   * full locale data every tag collapses to the same output, and the two
+   * assertions above would pass while proving nothing.
+   */
+  it('produces visibly different strings for zh and de', () => {
+    expect(eightDaysAgo.toLocaleDateString('zh')).not.toBe(
+      eightDaysAgo.toLocaleDateString('de'),
+    );
+  });
+
+  it('keeps the English form under an en session', () => {
+    renderThread('en', { comments: [oldComment] });
+    expect(dateCell()).toContain(eightDaysAgo.toLocaleDateString('en'));
+  });
+
+  /**
+   * The trap the issue was really about, and the reason objectstack#5506 left
+   * this branch alone.
+   *
+   * `toLocaleDateString(tag)` canonicalizes its argument and throws
+   * `RangeError` on anything not well-formed per BCP 47. `'en_US'` — the POSIX
+   * spelling, a plausible thing for a host to put in `defaultLanguage` — is
+   * exactly such a tag, and the session `language` reaches the component
+   * verbatim. Handed straight to `toLocaleDateString`, that `RangeError` lands
+   * in `formatTimestamp`'s OUTER catch, whose fallback is `return iso`: the
+   * comment's date would have been replaced by a raw
+   * `2026-07-29T…Z`, worse than the un-localized date it set out to fix.
+   *
+   * ── Direction, stated honestly ────────────────────────────────────────────
+   * This case is GREEN on BOTH sides of the change, and reverting
+   * `CommentThread.tsx` does NOT turn it red — `origin/main` never passed the
+   * tag anywhere, so it could not trip over a bad one. Its counterfactual is
+   * not the old code but the NAIVE fix, and that is what it was reverse-checked
+   * against: dropping the inner try/catch in `formatAbsoluteDate` (passing
+   * `language` straight through) turns this case red with the raw ISO string in
+   * the DOM. Recorded rather than dressed up as a red-before regression pin.
+   */
+  it('falls back to the runtime locale on a malformed session tag, never to raw ISO', () => {
+    const { container } = renderThread('en_US', { comments: [oldComment] });
+
+    expect(dateCell()).toContain(eightDaysAgo.toLocaleDateString());
+    expect(container.textContent).not.toContain(oldComment.createdAt);
+    // The shape of the raw value, in case the ISO string is ever reformatted.
+    expect(container.textContent).not.toMatch(/\d{4}-\d{2}-\d{2}T\d{2}:\d{2}/);
+    // The rest of the thread still speaks (fallbackLng) English — the guard is
+    // local to the date, it does not disable the session.
+    expect(screen.getByText('Send')).toBeTruthy();
+  });
+});
+
 describe('CommentThread composer (objectstack#5506)', () => {
   it('translates the placeholder and the send button', () => {
     renderThread('zh');
diff --git a/packages/collaboration/src/__tests__/comment-thread-no-provider-fallback.test.tsx b/packages/collaboration/src/__tests__/comment-thread-no-provider-fallback.test.tsx
index 5823e2dc9..2cbf63656 100644
--- a/packages/collaboration/src/__tests__/comment-thread-no-provider-fallback.test.tsx
+++ b/packages/collaboration/src/__tests__/comment-thread-no-provider-fallback.test.tsx
@@ -159,6 +159,57 @@ describe('CommentThread with no I18nProvider — English fallback (objectstack#5
     expect(screen.queryByText('1 comments')).toBeNull();
   });
 
+  /**
+   * objectui#3441 — the three emoji-only controls, named from the same map.
+   *
+   * `getByRole(… { name })` computes the accessible name rather than reading an
+   * attribute: for a `button`, name-from-content outranks `title`, so only an
+   * `aria-label` can displace the glyph. With no provider that label has to come
+   * out of `COLLAB_DEFAULT_TRANSLATIONS`, or a standalone host gets a control
+   * announced as `collaboration.reactThumbsUp`.
+   *
+   * Unlike the copy pins in this file these are RED before / GREEN after: the
+   * names did not exist in any language on `origin/main`.
+   */
+  it('names the emoji-only reaction and dismiss buttons in English', () => {
+    renderBare();
+
+    expect(screen.getAllByRole('button', { name: 'React with thumbs up' }).length).toBe(2);
+    expect(screen.getAllByRole('button', { name: 'React with heart' }).length).toBe(2);
+    expect(screen.queryAllByRole('button', { name: '👍' })).toHaveLength(0);
+
+    fireEvent.click(screen.getAllByText('Reply')[0]);
+    expect(screen.getByRole('button', { name: 'Cancel reply' })).toBeTruthy();
+    expect(screen.queryAllByRole('button', { name: '✕' })).toHaveLength(0);
+  });
+
+  /**
+   * objectui#3441 — with no provider the session language is whatever
+   * react-i18next reports (in practice `'en'`), and the >= 7d branch now hands
+   * that to `toLocaleDateString`. What must hold on this path is narrower than
+   * under a provider but is the part a standalone host would notice: a real
+   * formatted date, never the raw ISO string `formatTimestamp`'s outer catch
+   * would produce if a bad tag reached `Intl`.
+   */
+  it('formats a week-old comment as a date, not a raw ISO string', () => {
+    const eightDaysAgo = new Date(Date.now() - 8 * 24 * 60 * 60 * 1000);
+    const { container } = renderBare({
+      comments: [
+        {
+          id: 'old',
+          author: alice,
+          content: 'From last week.',
+          mentions: [],
+          createdAt: eightDaysAgo.toISOString(),
+        },
+      ],
+    });
+
+    expect(container.textContent).not.toContain(eightDaysAgo.toISOString());
+    expect(container.textContent).not.toMatch(/\d{4}-\d{2}-\d{2}T\d{2}:\d{2}/);
+    expect(screen.getByText(eightDaysAgo.toLocaleDateString('en'))).toBeTruthy();
+  });
+
   /**
    * The failure mode this whole file exists to catch: a key wired into the
    * component but absent from the defaults map renders as its own dotted name.
@@ -202,4 +253,40 @@ describe('COLLAB_DEFAULT_TRANSLATIONS is the package-wide English source', () =>
     expect(COLLAB_DEFAULT_TRANSLATIONS['collaboration.reactionCount']).toBe('{{count}} reactions');
     expect(COLLAB_DEFAULT_TRANSLATIONS['collaboration.reactionCountOne']).toBe('{{count}} reaction');
   });
+
+  /**
+   * objectui#3441. `reactThumbsUp` and `addThumbsUp` dispatch the same reaction
+   * today but name two different controls that render side by side, so their
+   * copy must not collapse into one string — that is the thing a later
+   * "de-duplicate these two keys" cleanup would break, and this is where it
+   * fails.
+   */
+  it('gives the quick thumbs-up its own copy, distinct from the picker', () => {
+    expect(COLLAB_DEFAULT_TRANSLATIONS['collaboration.reactThumbsUp']).toBeTruthy();
+    expect(COLLAB_DEFAULT_TRANSLATIONS['collaboration.reactHeart']).toBeTruthy();
+    expect(COLLAB_DEFAULT_TRANSLATIONS['collaboration.cancelReply']).toBeTruthy();
+    expect(COLLAB_DEFAULT_TRANSLATIONS['collaboration.reactThumbsUp']).not.toBe(
+      COLLAB_DEFAULT_TRANSLATIONS['collaboration.addThumbsUp'],
+    );
+  });
+
+  /**
+   * An accessible name lives in an attribute, so `container.textContent` — what
+   * the "never renders a raw i18n key" case above scans — cannot see it. A
+   * missing default would surface as `aria-label="collaboration.reactHeart"`
+   * and nothing else in this file would notice.
+   */
+  it('never leaves a raw key or placeholder in an accessible name', () => {
+    const { container } = renderBare();
+    fireEvent.click(screen.getAllByText('Reply')[0]);
+
+    const names = Array.from(container.querySelectorAll('[aria-label]')).map((n) =>
+      n.getAttribute('aria-label'),
+    );
+    expect(names.length).toBeGreaterThan(0);
+    for (const name of names) {
+      expect(name).not.toMatch(/^(collaboration|common)\.\w+$/);
+      expect(name).not.toMatch(/\{\{\w+\}\}/);
+    }
+  });
 });
diff --git a/packages/collaboration/src/useCollaborationTranslation.ts b/packages/collaboration/src/useCollaborationTranslation.ts
index 5afee12e7..2d0b0dca5 100644
--- a/packages/collaboration/src/useCollaborationTranslation.ts
+++ b/packages/collaboration/src/useCollaborationTranslation.ts
@@ -70,6 +70,18 @@ export const COLLAB_DEFAULT_TRANSLATIONS: Record<string, string> = {
   'collaboration.addThumbsUp': 'Add thumbs up',
   // Per-comment actions and the reply banner
   'collaboration.reply': 'Reply',
+  // Accessible names for the three emoji-only controls (objectui#3441). For a
+  // `button` the accessible name is computed from CONTENT before `title` is
+  // consulted, so an emoji button is named by its glyph until an `aria-label`
+  // overrides it — these three keys ARE those names, not decoration.
+  //
+  // `reactThumbsUp` is deliberately distinct from `addThumbsUp` above even
+  // though both currently dispatch `onReaction(id, '👍')`: `addThumbsUp` names
+  // the reaction-bar `+` picker, and the two render side by side on any comment
+  // that already has reactions.
+  'collaboration.reactThumbsUp': 'React with thumbs up',
+  'collaboration.reactHeart': 'React with heart',
+  'collaboration.cancelReply': 'Cancel reply',
   'collaboration.replyingTo': 'Replying to {{name}}...',
   'collaboration.replyingToComment': 'Replying to comment...',
   // Composer
diff --git a/packages/i18n/src/locales/ar.ts b/packages/i18n/src/locales/ar.ts
index 7c67217cc..b8e16c7af 100644
--- a/packages/i18n/src/locales/ar.ts
+++ b/packages/i18n/src/locales/ar.ts
@@ -3071,6 +3071,9 @@ const ar = {
     reactionCountOne: "{{count}} تفاعل",
     addThumbsUp: "إضافة إعجاب",
     reply: "رد",
+    reactThumbsUp: "التفاعل بإعجاب",
+    reactHeart: "التفاعل بقلب",
+    cancelReply: "إلغاء الرد",
     replyingTo: "الرد على {{name}}…",
     replyingToComment: "الرد على التعليق…",
     commentPlaceholder: "أضف تعليقًا… (استخدم @ للإشارة)",
diff --git a/packages/i18n/src/locales/de.ts b/packages/i18n/src/locales/de.ts
index f4964ab7c..2bfb17cba 100644
--- a/packages/i18n/src/locales/de.ts
+++ b/packages/i18n/src/locales/de.ts
@@ -3071,6 +3071,9 @@ const de = {
     reactionCountOne: "{{count}} Reaktion",
     addThumbsUp: "Daumen hoch hinzufügen",
     reply: "Antworten",
+    reactThumbsUp: "Mit Daumen hoch reagieren",
+    reactHeart: "Mit Herz reagieren",
+    cancelReply: "Antwort abbrechen",
     replyingTo: "Antwort an {{name}} …",
     replyingToComment: "Antwort auf Kommentar …",
     commentPlaceholder: "Kommentar hinzufügen … (@ für Erwähnungen)",
diff --git a/packages/i18n/src/locales/en.ts b/packages/i18n/src/locales/en.ts
index 7aaebe2f3..c5e60c847 100644
--- a/packages/i18n/src/locales/en.ts
+++ b/packages/i18n/src/locales/en.ts
@@ -3212,6 +3212,20 @@ const en = {
     reactionCountOne: '{{count}} reaction',
     addThumbsUp: 'Add thumbs up',
     reply: 'Reply',
+    // Accessible names for the three emoji-only controls (objectui#3441).
+    // A `button`'s accessible name is computed from its CONTENT before `title`
+    // is ever consulted, so '👍' / '❤️' / '✕' named themselves — these keys are
+    // wired as `aria-label`, which overrides content.
+    //
+    // `reactThumbsUp` stays distinct from `addThumbsUp` above even though both
+    // dispatch the same reaction today: that one names the reaction-bar `+`
+    // picker, and the two render side by side on a comment that already has
+    // reactions.
+    reactThumbsUp: 'React with thumbs up',
+    reactHeart: 'React with heart',
+    // Not `common.cancel`: an accessible name has to say what is cancelled.
+    // Only the reply TARGET is dropped — the composer keeps whatever was typed.
+    cancelReply: 'Cancel reply',
     replyingTo: 'Replying to {{name}}...',
     // The no-author-found half of the reply banner, as a whole sentence:
     // languages that inflect around the addressee cannot build it by
diff --git a/packages/i18n/src/locales/es.ts b/packages/i18n/src/locales/es.ts
index d313942b3..1547bc6cb 100644
--- a/packages/i18n/src/locales/es.ts
+++ b/packages/i18n/src/locales/es.ts
@@ -3076,6 +3076,9 @@ const es = {
     reactionCountOne: "{{count}} reacción",
     addThumbsUp: "Agregar me gusta",
     reply: "Responder",
+    reactThumbsUp: "Reaccionar con me gusta",
+    reactHeart: "Reaccionar con corazón",
+    cancelReply: "Cancelar respuesta",
     replyingTo: "Respondiendo a {{name}}…",
     replyingToComment: "Respondiendo al comentario…",
     commentPlaceholder: "Agregar un comentario… (usa @ para mencionar)",
diff --git a/packages/i18n/src/locales/fr.ts b/packages/i18n/src/locales/fr.ts
index 19c2426b0..3cdd7aca6 100644
--- a/packages/i18n/src/locales/fr.ts
+++ b/packages/i18n/src/locales/fr.ts
@@ -3071,6 +3071,9 @@ const fr = {
     reactionCountOne: "{{count}} réaction",
     addThumbsUp: "Ajouter un pouce levé",
     reply: "Répondre",
+    reactThumbsUp: "Réagir avec un pouce levé",
+    reactHeart: "Réagir avec un cœur",
+    cancelReply: "Annuler la réponse",
     replyingTo: "Réponse à {{name}}…",
     replyingToComment: "Réponse au commentaire…",
     commentPlaceholder: "Ajouter un commentaire… (utilisez @ pour mentionner)",
diff --git a/packages/i18n/src/locales/ja.ts b/packages/i18n/src/locales/ja.ts
index ffe85e71e..55d5bcfd5 100644
--- a/packages/i18n/src/locales/ja.ts
+++ b/packages/i18n/src/locales/ja.ts
@@ -3071,6 +3071,9 @@ const ja = {
     reactionCountOne: "リアクション {{count}} 件",
     addThumbsUp: "いいねを追加",
     reply: "返信",
+    reactThumbsUp: "いいねでリアクション",
+    reactHeart: "ハートでリアクション",
+    cancelReply: "返信をキャンセル",
     replyingTo: "{{name}} に返信中…",
     replyingToComment: "このコメントに返信中…",
     commentPlaceholder: "コメントを追加…(@ でメンション)",
diff --git a/packages/i18n/src/locales/ko.ts b/packages/i18n/src/locales/ko.ts
index 391444a9a..93bb94a0c 100644
--- a/packages/i18n/src/locales/ko.ts
+++ b/packages/i18n/src/locales/ko.ts
@@ -3071,6 +3071,9 @@ const ko = {
     reactionCountOne: "반응 {{count}}개",
     addThumbsUp: "좋아요 추가",
     reply: "답글",
+    reactThumbsUp: "좋아요로 반응",
+    reactHeart: "하트로 반응",
+    cancelReply: "답글 취소",
     replyingTo: "{{name}}님에게 답글 작성 중…",
     replyingToComment: "이 댓글에 답글 작성 중…",
     commentPlaceholder: "댓글 추가…(@로 멘션)",
diff --git a/packages/i18n/src/locales/pt.ts b/packages/i18n/src/locales/pt.ts
index 5bfe4e51c..0f7f2859a 100644
--- a/packages/i18n/src/locales/pt.ts
+++ b/packages/i18n/src/locales/pt.ts
@@ -3071,6 +3071,9 @@ const pt = {
     reactionCountOne: "{{count}} reação",
     addThumbsUp: "Adicionar curtida",
     reply: "Responder",
+    reactThumbsUp: "Reagir com curtida",
+    reactHeart: "Reagir com coração",
+    cancelReply: "Cancelar resposta",
     replyingTo: "Respondendo a {{name}}…",
     replyingToComment: "Respondendo ao comentário…",
     commentPlaceholder: "Adicionar um comentário… (use @ para mencionar)",
diff --git a/packages/i18n/src/locales/ru.ts b/packages/i18n/src/locales/ru.ts
index be5555069..d9d01a217 100644
--- a/packages/i18n/src/locales/ru.ts
+++ b/packages/i18n/src/locales/ru.ts
@@ -3071,6 +3071,9 @@ const ru = {
     reactionCountOne: "{{count}} реакция",
     addThumbsUp: "Поставить лайк",
     reply: "Ответить",
+    reactThumbsUp: "Отреагировать лайком",
+    reactHeart: "Отреагировать сердечком",
+    cancelReply: "Отменить ответ",
     replyingTo: "Ответ для {{name}}…",
     replyingToComment: "Ответ на комментарий…",
     commentPlaceholder: "Добавьте комментарий… (@ — упоминание)",
diff --git a/packages/i18n/src/locales/zh.ts b/packages/i18n/src/locales/zh.ts
index 0a1055b64..161d4fceb 100644
--- a/packages/i18n/src/locales/zh.ts
+++ b/packages/i18n/src/locales/zh.ts
@@ -3125,6 +3125,9 @@ const zh = {
     reactionCountOne: '{{count}} 个回应',
     addThumbsUp: '点赞',
     reply: '回复',
+    reactThumbsUp: '以点赞回应',
+    reactHeart: '以爱心回应',
+    cancelReply: '取消回复',
     replyingTo: '正在回复 {{name}}…',
     replyingToComment: '正在回复该评论…',
     commentPlaceholder: '添加评论…(输入 @ 提及他人)',