diff --git a/.github/workflows/mailbox-regressions.yml b/.github/workflows/mailbox-regressions.yml
new file mode 100644
index 00000000..4b5d8186
--- /dev/null
+++ b/.github/workflows/mailbox-regressions.yml
@@ -0,0 +1,68 @@
+name: Mailbox regressions
+on:
+  push:
+    branches: ['fix/mailbox-client-*']
+  pull_request:
+    paths:
+      - 'src/msg/plugins/mail_views.py'
+      - 'src/msg/plugins/communication.py'
+      - 'src/msg/client_subagents_remote.py'
+      - 'tests/test_mailbox_contacts.py'
+      - 'tests/test_todo_due_inbox.py'
+      - 'tests/test_bounty.py'
+      - 'tests/test_client_subagents_remote.py'
+      - '.github/workflows/mailbox-regressions.yml'
+  workflow_dispatch:
+permissions:
+  contents: read
+concurrency:
+  group: mailbox-${{ github.head_ref || github.ref_name }}
+  cancel-in-progress: true
+jobs:
+  regressions:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    services:
+      postgres:
+        image: postgres:16
+        env:
+          POSTGRES_USER: msgtest
+          POSTGRES_PASSWORD: msgtest
+          POSTGRES_DB: postgres
+        ports:
+          - 5432:5432
+        options: >-
+          --health-cmd "pg_isready -U msgtest -d postgres"
+          --health-interval 5s --health-timeout 5s --health-retries 10
+    env:
+      MSG_TEST_POSTGRES_URL_TEMPLATE: postgresql://msgtest:msgtest@127.0.0.1:5432/{database}
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          persist-credentials: false
+      - uses: actions/setup-python@v7
+        with:
+          python-version: '3.15'
+          allow-prereleases: true
+      - name: Install locked dependencies
+        run: |
+          python -m pip install uv==0.12.20
+          uv sync --locked --extra dev --python "$(command -v python)"
+      - name: Record tested source
+        run: |
+          mkdir -p artifacts
+          git rev-parse HEAD > artifacts/commit.txt
+          git rev-parse HEAD^{tree} > artifacts/tree.txt
+      - name: Check system notices, contact privacy and private agent queues
+        run: >-
+          uv run --locked --extra dev pytest
+          tests/test_mailbox_contacts.py tests/test_todo_due_inbox.py
+          tests/test_bounty.py tests/test_client_subagents_remote.py
+          tests/test_tui_mailbox_selection.py tests/test_dm.py
+          --junitxml=artifacts/mailbox.xml
+      - uses: actions/upload-artifact@v7.0.1
+        if: always()
+        with:
+          name: mailbox-regressions
+          path: artifacts/
+          if-no-files-found: error
diff --git a/src/msg/plugins/mail_views.py b/src/msg/plugins/mail_views.py
index c906a73c..ddb159ab 100644
--- a/src/msg/plugins/mail_views.py
+++ b/src/msg/plugins/mail_views.py
@@ -11,6 +11,9 @@
 async def contact(app, ctx, request, tx, subject):
     from msg.plugins.discovery import visible
 
+    # Worker reminders and settlement notices have no sending account.
+    if subject is None:
+        return {'name': 'System notification'}
     if await visible(app, ctx, request, tx, subject):
         resource = await tx.resource(subject)
         return {'name': resource.name, 'path': await tx.path(subject)}
diff --git a/tests/test_bounty.py b/tests/test_bounty.py
index df4e9af6..684a11a7 100644
--- a/tests/test_bounty.py
+++ b/tests/test_bounty.py
@@ -166,8 +166,11 @@ async def test_prefunded_bounty_pays_offline_publisher_and_stops_at_budget(insta
     assert await balance(app, publisher_key, publisher) == 10
     assert (await call(app, 'money.state', {})).data['total_supply_minor'] == 20
     inbox = await call(app, 'communication.inbox', {}, key=claimant_key, subject=claimant)
+    assert inbox.status == 'ok', wire(inbox)
     bounty_notices = [item for item in inbox.data['items'] if item.get('source') == 'bounty_claim']
     assert len(bounty_notices) == 1
+    assert bounty_notices[0]['sender'] is None
+    assert bounty_notices[0]['sender_contact'] == {'name': 'System notification'}
     assert bounty_notices[0]['claim_id'] == claimed.data['claim']['id']
     replay = await call(
         app,
diff --git a/tests/test_client_subagents_remote.py b/tests/test_client_subagents_remote.py
index 8ee4651b..8107c00b 100644
--- a/tests/test_client_subagents_remote.py
+++ b/tests/test_client_subagents_remote.py
@@ -8,6 +8,7 @@
 
 from msg.client import ClientState, MsgClient
 from msg.client_subagents_remote import RemoteAgents
+from msg.core.codec import b64, wire
 from msg.core.errors import Failure
 from msg.transports.client import HTTPTransport
 from msg.transports.http import create_app
@@ -65,6 +66,12 @@ async def test_remote_private_delivery_tail_restart_and_archive(installed, tmp_p
             await agents.send('bot1', 'bot2', 'after archive')
         history = await agents.inbox('bot2')
         assert [x['message'] for x in history['items']] == ['private handoff']
+        public = client.checked(
+            await client.call(
+                'file.create',
+                {'parent': '/main', 'name': 'public-control.txt', 'data': b64(b'Public control')},
+            )
+        )
         for anonymous in (True, False):
             visitor = client if anonymous else stranger
             for operation, args in [
@@ -77,11 +84,23 @@ async def test_remote_private_delivery_tail_restart_and_archive(installed, tmp_p
                 result = await visitor.call(operation, args, anonymous=anonymous)
                 assert result.status == 'error'
                 assert 'private handoff' not in repr(result)
-            visible = await visitor.call(
-                'discovery.list', {'type': 'file', 'limit': 200}, anonymous=anonymous
-            )
-            assert visible.status == 'ok'
-            assert not any('msg-stable-message' in item['name'] for item in visible.data['items'])
+            # Exercise every page without exhausting one request's read budget.
+            query = {'type': 'file', 'limit': 20}
+            cursors, seen = set(), set()
+            while True:
+                visible = await visitor.call('discovery.list', query, anonymous=anonymous)
+                assert visible.status == 'ok', wire(visible.error)
+                for item in visible.data['items']:
+                    assert 'msg-stable-message' not in item['name']
+                    assert item['id'] not in seen
+                    seen.add(item['id'])
+                cursor = visible.data.get('cursor')
+                if cursor is None:
+                    break
+                assert cursor not in cursors
+                cursors.add(cursor)
+                query['cursor'] = cursor
+            assert public.resources[0].id in seen
             feed = await visitor.call('discovery.recommendations', {}, anonymous=anonymous)
             assert 'private handoff' not in repr(feed)
         users = client.checked(
diff --git a/tests/test_mailbox_contacts.py b/tests/test_mailbox_contacts.py
new file mode 100644
index 00000000..eaa4c838
--- /dev/null
+++ b/tests/test_mailbox_contacts.py
@@ -0,0 +1,80 @@
+"""System notices remain readable without bypassing real contact privacy."""
+
+from dataclasses import replace
+from datetime import timedelta
+
+import pytest
+from read_only_evidence import readonly_evidence
+from test_oauth import browser_login, oauth as oauth
+from test_service import call, register
+
+from msg.core.codec import wire
+from msg.workers.maintenance import run_maintenance
+
+
+@pytest.mark.asyncio
+async def test_browser_system_notice_has_no_fake_user_and_reads_have_no_effects(oauth, monkeypatch):
+    app, key, subject, http = oauth
+    todo = await call(
+        app,
+        'identity.todo_put',
+        {
+            'name': 'browser-due',
+            'title': 'Private browser reminder',
+            'due_at': wire(app.clock() - timedelta(hours=1)),
+        },
+        key=key,
+        subject=subject,
+    )
+    assert todo.status == 'ok', wire(todo)
+    assert await run_maintenance(app, 'deliver_due_todos', scheduled=True) == {
+        'delivered_todo_reminders': 1
+    }
+    assert (await http.get('/@oauth-owner/in')).status_code == 401
+    await browser_login(oauth)
+    async with readonly_evidence(app, monkeypatch):
+        for accept in ('text/html', 'text/markdown'):
+            response = await http.get('/@oauth-owner/in', headers={'Accept': accept})
+            assert response.status_code == 200, response.text
+            assert 'System notification' in response.text
+            assert '/@None' not in response.text
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize('mailbox', ['inbox', 'outbox'])
+async def test_real_private_contact_still_hides_name_and_path(installed, monkeypatch, mailbox):
+    app, _ = installed
+    author_key, author, _ = await register(app, 'contact-author')
+    recipient_key, recipient, _ = await register(app, 'contact-recipient')
+    post = await call(
+        app,
+        'content.post_create',
+        {'parent': '/main', 'body': '# Reference\n\nReadable reference with a private contact'},
+        key=author_key,
+        subject=author,
+    )
+    assert post.status == 'ok', wire(post)
+    sent = await call(
+        app,
+        'communication.send',
+        {'recipient': recipient, 'resource': {'id': post.resources[0].id}},
+        key=author_key,
+        subject=author,
+    )
+    assert sent.status == 'ok', wire(sent)
+    key, subject, hidden, label = (
+        (recipient_key, recipient, author, 'sender_contact')
+        if mailbox == 'inbox'
+        else (author_key, author, recipient, 'recipient_contact')
+    )
+    async with app.metadata.transaction(write=True) as tx:
+        resource = await tx.resource(hidden)
+        await tx.replace(
+            replace(resource, mode=0o600, generation=resource.generation + 1), resource.generation
+        )
+    async with readonly_evidence(app, monkeypatch):
+        result = await call(app, 'communication.' + mailbox, {}, key=key, subject=subject)
+        assert result.status == 'ok', wire(result)
+        item = next(item for item in result.data['items'] if item['id'] == sent.data['message_id'])
+        assert item[label] == {'name': 'Private account'}
+        assert item['preview']['excerpt'] == 'Readable reference with a private contact'
diff --git a/tests/test_todo_due_inbox.py b/tests/test_todo_due_inbox.py
index 8df87e36..f62843a6 100644
--- a/tests/test_todo_due_inbox.py
+++ b/tests/test_todo_due_inbox.py
@@ -47,9 +47,13 @@ async def test_due_todo_is_only_in_owner_inbox_and_repeated_maintenance_is_noop(
         assert tx.one('SELECT COUNT(*) FROM audit')[0] == before + 1
         assert tx.one('SELECT COUNT(*) FROM messages WHERE resource=?', (rid,))[0] == 1
     own = await call(app, 'communication.inbox', {}, key=owner_key, subject=owner)
+    assert own.status == 'ok', wire(own)
     notices = [item for item in own.data['items'] if item['resource']['id'] == rid]
     assert len(notices) == 1 and notices[0]['source'] == 'todo_due'
     assert notices[0]['recipient'] == owner
+    assert notices[0]['sender'] is None
+    assert notices[0]['sender_contact'] == {'name': 'System notification'}
+    assert notices[0]['recipient_contact'] == {'name': '@due-owner', 'path': '/@due-owner'}
     assert notices[0]['todo_revision_at_delivery'] == todo.resources[0].revision
     assert not [
         item