diff --git a/__tests__/unit/services/cat-account.test.ts b/__tests__/unit/services/cat-account.test.ts
new file mode 100644
index 000000000..4692cd15b
--- /dev/null
+++ b/__tests__/unit/services/cat-account.test.ts
@@ -0,0 +1,106 @@
+/**
+ * The Cat needs a row before it can speak.
+ *
+ * Everything else about tagging depends on the Cat being an ordinary account:
+ * that is what lets a Cat reply be an ordinary message row, with no branch in
+ * read receipts, search, threading or realtime. So this is the one piece that
+ * cannot be "handled in the renderer".
+ *
+ * The behaviours pinned here are the ones that decide whether it is safe to run
+ * on every tick: it must not create a second Cat, it must recover from a
+ * half-built account, and it must refuse rather than improvise when it cannot
+ * establish one — a caller that gets null must not invent a sender.
+ */
+
+import { ensureCatAccount } from '@/services/mentions/cat-account';
+
+type Row = { id: string; username: string } | null;
+
+function adminWith({
+  profile,
+  createError,
+  profileAfterCreate,
+}: {
+  profile: Row;
+  createError?: { message: string };
+  profileAfterCreate?: Row;
+}) {
+  const createUser = jest.fn().mockResolvedValue({ error: createError ?? null });
+  const update = jest.fn(() => ({ eq: jest.fn().mockResolvedValue({ error: null }) }));
+  let lookups = 0;
+
+  const admin = {
+    auth: { admin: { createUser } },
+    from: () => ({
+      select: () => ({
+        eq: () => ({
+          maybeSingle: () => {
+            lookups += 1;
+            const row = lookups === 1 ? profile : (profileAfterCreate ?? profile);
+            return Promise.resolve({ data: row, error: null });
+          },
+        }),
+      }),
+      update,
+    }),
+  };
+  return { admin: admin as never, createUser, update, lookups: () => lookups };
+}
+
+describe('ensureCatAccount', () => {
+  it('returns the existing account without creating a second one', async () => {
+    const { admin, createUser } = adminWith({ profile: { id: 'cat-1', username: 'cat' } });
+    await expect(ensureCatAccount(admin)).resolves.toEqual({ id: 'cat-1', username: 'cat' });
+    expect(createUser).not.toHaveBeenCalled();
+  });
+
+  it('creates the account with an address nobody can ever receive mail at', async () => {
+    const { admin, createUser } = adminWith({
+      profile: null,
+      profileAfterCreate: { id: 'cat-1', username: 'cat' },
+    });
+    await ensureCatAccount(admin);
+
+    const [args] = createUser.mock.calls[0];
+    // .invalid is reserved by RFC 2606. An account's email is its password-reset
+    // channel, so a bot identity with a routable address is one somebody can
+    // eventually take.
+    expect(args.email).toMatch(/@orangecat\.invalid$/);
+    expect(args.email.split('@')[0]).toBe('cat');
+    // No password is set, so it cannot be signed into with one.
+    expect(args.password).toBeUndefined();
+  });
+
+  it('recovers when the auth user already exists but the profile was deleted', async () => {
+    const { admin } = adminWith({
+      profile: null,
+      createError: { message: 'A user with this email address has already been registered' },
+      profileAfterCreate: { id: 'cat-1', username: 'cat' },
+    });
+    // The auth user survives a deleted profile row, so "already registered" is
+    // the expected path on a re-run, not a failure.
+    await expect(ensureCatAccount(admin)).resolves.toEqual({ id: 'cat-1', username: 'cat' });
+  });
+
+  it('refuses rather than improvising when creation genuinely fails', async () => {
+    const { admin } = adminWith({
+      profile: null,
+      createError: { message: 'database is on fire' },
+    });
+    await expect(ensureCatAccount(admin)).resolves.toBeNull();
+  });
+
+  it('refuses when the auth user exists but no profile ever appears', async () => {
+    const { admin } = adminWith({ profile: null, profileAfterCreate: null });
+    await expect(ensureCatAccount(admin)).resolves.toBeNull();
+  });
+
+  it('describes the account so a half-built one converges', async () => {
+    const { admin, update } = adminWith({
+      profile: null,
+      profileAfterCreate: { id: 'cat-1', username: 'cat' },
+    });
+    await ensureCatAccount(admin);
+    expect(update).toHaveBeenCalledWith(expect.objectContaining({ name: 'Cat' }));
+  });
+});
diff --git a/scripts/deploy-selfhost.sh b/scripts/deploy-selfhost.sh
index f613d9df2..045aba082 100755
--- a/scripts/deploy-selfhost.sh
+++ b/scripts/deploy-selfhost.sh
@@ -253,40 +253,44 @@ echo "=== ship ops scripts + nightly Cat-eval timer ==="
     "$OC_BOX:$OC_APP_BASE/scripts/eval-cat-outcomes.mjs"
   scp "${SSH_OPTS[@]}" -q scripts/check-data-invariants.mjs \
     "$OC_BOX:$OC_APP_BASE/scripts/check-data-invariants.mjs"
-  scp "${SSH_OPTS[@]}" -q scripts/systemd/orangecat-cat-eval.service \
-    scripts/systemd/orangecat-cat-eval.timer \
-    scripts/systemd/orangecat-cat-outcomes.service \
-    scripts/systemd/orangecat-cat-outcomes.timer \
-    scripts/systemd/orangecat-data-invariants.service \
-    scripts/systemd/orangecat-data-invariants.timer \
-    "scripts/systemd/orangecat-cron@cat-brief.timer" \
-    "scripts/systemd/orangecat-cron@cat-watches.timer" \
-    "scripts/systemd/orangecat-cron@reindex-embeddings.timer" "$OC_BOX:/tmp/"
-  ssh "${SSH_OPTS[@]}" "$OC_BOX" 'bash -s' <<'EVAL_UNITS'
+  # ONE list. It used to be written three times — the scp arguments, the
+  # install loop and the enable calls — so adding a timer meant editing three
+  # places, and missing the third shipped a unit file that never ran. That is
+  # the same silent-failure shape as a cron route nothing invokes.
+  UNITS=(
+    orangecat-cat-eval.service
+    orangecat-cat-eval.timer
+    orangecat-cat-outcomes.service
+    orangecat-cat-outcomes.timer
+    orangecat-data-invariants.service
+    orangecat-data-invariants.timer
+    "orangecat-cron@cat-account.timer"
+    "orangecat-cron@cat-brief.timer"
+    "orangecat-cron@cat-watches.timer"
+    "orangecat-cron@reindex-embeddings.timer"
+  )
+  scp "${SSH_OPTS[@]}" -q "${UNITS[@]/#/scripts/systemd/}" "$OC_BOX:/tmp/"
+  ssh "${SSH_OPTS[@]}" "$OC_BOX" 'bash -s' "${UNITS[@]}" <<'EVAL_UNITS'
 set -e
+units=("$@")
 changed=0
-for u in orangecat-cat-eval.service orangecat-cat-eval.timer \
-         orangecat-cat-outcomes.service orangecat-cat-outcomes.timer \
-         orangecat-data-invariants.service orangecat-data-invariants.timer \
-         orangecat-cron@cat-brief.timer orangecat-cron@cat-watches.timer \
-         orangecat-cron@reindex-embeddings.timer; do
+for u in "${units[@]}"; do
   if ! cmp -s "/tmp/$u" "/etc/systemd/system/$u" 2>/dev/null; then
     install -m 644 "/tmp/$u" "/etc/systemd/system/$u"; changed=1
   fi
   rm -f "/tmp/$u"
 done
 [ "$changed" = 1 ] && systemctl daemon-reload
-systemctl enable --now orangecat-cat-eval.timer >/dev/null
-systemctl enable --now orangecat-cat-outcomes.timer >/dev/null
-systemctl enable --now orangecat-data-invariants.timer >/dev/null
-systemctl enable --now orangecat-cron@cat-brief.timer >/dev/null
-systemctl enable --now orangecat-cron@cat-watches.timer >/dev/null
-systemctl enable --now orangecat-cron@reindex-embeddings.timer >/dev/null
-echo "cat-eval timer: $(systemctl is-enabled orangecat-cat-eval.timer) / $(systemctl is-active orangecat-cat-eval.timer)"
-echo "cat-outcomes timer: $(systemctl is-enabled orangecat-cat-outcomes.timer) / $(systemctl is-active orangecat-cat-outcomes.timer)"
-echo "data-invariants timer: $(systemctl is-enabled orangecat-data-invariants.timer) / $(systemctl is-active orangecat-data-invariants.timer)"
-echo "cat-brief timer: $(systemctl is-enabled 'orangecat-cron@cat-brief.timer') / $(systemctl is-active 'orangecat-cron@cat-brief.timer')"
-echo "cat-watches timer: $(systemctl is-enabled 'orangecat-cron@cat-watches.timer') / $(systemctl is-active 'orangecat-cron@cat-watches.timer')"
+# Enable every TIMER we shipped, derived from the same list — a timer that is
+# installed but never enabled is a job that silently never runs.
+for u in "${units[@]}"; do
+  case "$u" in
+    *.timer)
+      systemctl enable --now "$u" >/dev/null
+      echo "$u: $(systemctl is-enabled "$u") / $(systemctl is-active "$u")"
+      ;;
+  esac
+done
 EVAL_UNITS
 } || echo "WARN: cat-eval ship step failed (non-fatal)" >&2
 
diff --git a/scripts/systemd/orangecat-cron@cat-account.timer b/scripts/systemd/orangecat-cron@cat-account.timer
new file mode 100644
index 000000000..c7a481a15
--- /dev/null
+++ b/scripts/systemd/orangecat-cron@cat-account.timer
@@ -0,0 +1,17 @@
+# SSOT: repo scripts/systemd/ — installed by deploy-selfhost.sh.
+# Instance of the generic orangecat-cron@.service template (curls
+# /api/cron/cat-account with CRON_SECRET).
+#
+# Asserts that the Cat has a profile. @cat is linked wherever it is written, so
+# a missing account makes every mention resolve to nobody — daily re-assertion
+# turns that from a support ticket into a self-healing invariant.
+[Unit]
+Description=OrangeCat Cat account invariant (daily)
+
+[Timer]
+OnCalendar=daily
+Persistent=true
+RandomizedDelaySec=15m
+
+[Install]
+WantedBy=timers.target
diff --git a/src/app/api/cron/cat-account/route.ts b/src/app/api/cron/cat-account/route.ts
new file mode 100644
index 000000000..a9a5407d2
--- /dev/null
+++ b/src/app/api/cron/cat-account/route.ts
@@ -0,0 +1,39 @@
+/**
+ * Cat Account Invariant Cron Route
+ *
+ * Schedule: systemd timer `orangecat-cron@cat-account.timer` on bitbaum, daily.
+ *
+ * Asserts that the Cat has an account. `@cat` is already tokenized and linked by
+ * utils/markdown.tsx, so if the profile row ever goes missing, every mention of
+ * the Cat across the platform silently resolves to nobody. Re-asserting it
+ * daily makes that self-healing instead of a support ticket.
+ *
+ * Cheap when it is a no-op, which is almost always: one indexed lookup.
+ */
+
+import { createAdminClient } from '@/lib/supabase/admin';
+import { ensureCatAccount } from '@/services/mentions/cat-account';
+import { logger } from '@/utils/logger';
+import { apiSuccess, apiError, apiUnauthorized } from '@/lib/api/standardResponse';
+import { verifyCronSecret } from '@/lib/api/cronAuth';
+
+export const dynamic = 'force-dynamic';
+export const maxDuration = 60;
+
+export async function GET(request: Request) {
+  if (!verifyCronSecret(request)) {
+    return apiUnauthorized();
+  }
+  try {
+    const account = await ensureCatAccount(createAdminClient());
+    if (!account) {
+      // Loud rather than silent: a missing Cat account breaks every @cat.
+      logger.error('Cat account could not be established', {}, 'CronCatAccount');
+      return apiError('Cat account unavailable', 'INTERNAL_ERROR', 500);
+    }
+    return apiSuccess({ id: account.id, username: account.username });
+  } catch (error) {
+    logger.error('Cat account check crashed', { error }, 'CronCatAccount');
+    return apiError('Cat account check failed', 'INTERNAL_ERROR', 500);
+  }
+}
diff --git a/src/services/mentions/cat-account.ts b/src/services/mentions/cat-account.ts
new file mode 100644
index 000000000..95a5c2edb
--- /dev/null
+++ b/src/services/mentions/cat-account.ts
@@ -0,0 +1,111 @@
+/**
+ * The Cat's account — created once, then re-asserted.
+ *
+ * The Cat is a real profile rather than a rendering convention, which is what
+ * lets a Cat reply be an ordinary `messages` or `timeline_events` row: read
+ * receipts, search, deletion, threading, moderation and realtime all work on it
+ * without a single branch. The cost of that is exactly this file — something has
+ * to create the row.
+ *
+ * Idempotent by design, and cheap when it is a no-op: one indexed lookup. It is
+ * safe to call on every worker tick, and doing so makes the account
+ * self-healing — if the profile is ever deleted, the Cat comes back rather than
+ * every `@cat` on the platform quietly resolving to nobody.
+ */
+
+import { CAT_USERNAME, CAT_DISPLAY_NAME } from '@/config/cat-identity';
+import { DATABASE_TABLES } from '@/config/database-tables';
+import { logger } from '@/utils/logger';
+import type { SupabaseClient } from '@supabase/supabase-js';
+
+/**
+ * The Cat's login address.
+ *
+ * `.invalid` is reserved by RFC 2606 and can never be delivered to or
+ * registered by anyone, which matters more than it looks: an account's email is
+ * its password-reset channel, so a bot identity with a routable address is a
+ * bot identity somebody else can eventually take. This one has no password and
+ * no reachable mailbox, so there is no credential to phish and no reset to
+ * intercept.
+ *
+ * The local part is also load-bearing. `handle_new_user` derives the profile's
+ * username from `split_part(email, '@', 1)`, so this address is what makes the
+ * Cat's handle `cat` at creation time.
+ */
+const CAT_EMAIL = `${CAT_USERNAME}@orangecat.invalid`;
+
+const CAT_BIO =
+  'The OrangeCat agent. Tag @cat in a message or under a post and I will answer there.';
+
+export interface CatAccount {
+  id: string;
+  username: string;
+}
+
+/**
+ * @param admin a service-role client. Creating an auth user and writing another
+ *   account's profile are both privileged, so this cannot run as the caller.
+ * @returns the Cat's account, or null if it could not be established — callers
+ *   must treat null as "do not attempt to speak as the Cat" rather than
+ *   inventing a sender.
+ */
+export async function ensureCatAccount(
+  admin: SupabaseClient
+): Promise<CatAccount | null> {
+  const existing = await findCatProfile(admin);
+  if (existing) {
+    return existing;
+  }
+
+  // No profile. Either the auth user does not exist either, or it does and its
+  // profile row was removed; both are handled by creating and then re-reading.
+  const { error: createError } = await admin.auth.admin.createUser({
+    email: CAT_EMAIL,
+    email_confirm: true,
+    // No password is set, so the account cannot be signed into with one.
+    user_metadata: { full_name: CAT_DISPLAY_NAME },
+  });
+
+  // "already registered" is the expected race and the expected second run: the
+  // auth user survives even when the profile row does not.
+  if (createError && !/already|exists|registered/i.test(createError.message)) {
+    logger.error('Could not create the Cat auth user', { error: createError.message }, 'CatAccount');
+    return null;
+  }
+
+  // handle_new_user inserts the profile from the email local part, so the
+  // username is already `cat`. Re-assert the presentation fields so a partially
+  // created account converges rather than staying half-built.
+  const profile = await findCatProfile(admin);
+  if (!profile) {
+    logger.error('Cat auth user exists but no profile row followed', {}, 'CatAccount');
+    return null;
+  }
+
+  const { error: updateError } = await admin
+    .from(DATABASE_TABLES.PROFILES)
+    .update({ name: CAT_DISPLAY_NAME, bio: CAT_BIO })
+    .eq('id', profile.id);
+
+  if (updateError) {
+    // The account exists and is usable; only its presentation is stale.
+    logger.warn('Cat profile created but could not be described', { error: updateError.message }, 'CatAccount');
+  }
+
+  logger.info('Cat account established', { id: profile.id }, 'CatAccount');
+  return profile;
+}
+
+async function findCatProfile(admin: SupabaseClient): Promise<CatAccount | null> {
+  const { data, error } = await admin
+    .from(DATABASE_TABLES.PROFILES)
+    .select('id, username')
+    .eq('username', CAT_USERNAME)
+    .maybeSingle();
+
+  if (error) {
+    logger.error('Could not look up the Cat profile', { error: error.message }, 'CatAccount');
+    return null;
+  }
+  return data ? { id: data.id as string, username: data.username as string } : null;
+}