test(discord): trim obfuscation tests to two invariants + one backfill regression

Seven near-identical predicate tests collapse into one invariant test
(flag OR sentinel name; neither on a normal channel; no flags attribute
is not obfuscated) plus the directory-filter test, per the repo's
<=2-invariant-tests-per-fix rule. The explicit-id backfill path gets its
own regression test in the existing backfill harness (fails on the
unfixed code, verified by sabotage).

tests/gateway/test_discord_channel_obfuscation.py

@@ -1,13 +1,7 @@
-"""Tests for Discord channel-obfuscation handling.
+"""Discord channel obfuscation (Aug 2026 privacy change, HTTP omission mandatory Nov 16 2026):
+channels a bot lacks VIEW_CHANNEL on arrive named "___hidden___" with flag 1 << 17 set.
+Enumeration sites must skip them. #90154"""
 
-Discord's August 2026 privacy change ("Channel Obfuscation") dispatches
-channels a bot lacks VIEW_CHANNEL on with the name "___hidden___", flag
-1 << 17 (CHANNEL_OBFUSCATED) set, and sensitive fields nulled. Enumeration
-sites (channel directory, missed-message backfill) must skip these
-placeholders — the HTTP API omits them entirely starting Nov 16, 2026.
-"""
-
-import unittest
 from types import SimpleNamespace
 
 from gateway.platforms.helpers import (
@@ -18,72 +12,35 @@ from gateway.platforms.helpers import (
 
 
 def _channel(name="general", flag_value=0, cid=123):
-    return SimpleNamespace(
-        id=cid,
-        name=name,
-        flags=SimpleNamespace(value=flag_value),
+    return SimpleNamespace(id=cid, name=name, flags=SimpleNamespace(value=flag_value))
+
+
+def test_flag_or_sentinel_name_marks_obfuscated():
+    assert is_discord_channel_obfuscated(_channel(name="secret", flag_value=DISCORD_CHANNEL_OBFUSCATED_FLAG | (1 << 4)))
+    # Older discord.py builds may not surface the flag bit; the name is the fallback signal.
+    assert is_discord_channel_obfuscated(_channel(name=DISCORD_OBFUSCATED_CHANNEL_NAME))
+    assert not is_discord_channel_obfuscated(_channel())
+    assert not is_discord_channel_obfuscated(SimpleNamespace(id=1, name="ok"))  # no flags attribute
+
+
+def test_build_discord_filters_hidden_channels(monkeypatch):
+    from gateway import channel_directory as cd
+
+    guild = SimpleNamespace(
+        name="TestGuild",
+        text_channels=[
+            _channel(name="general", cid=1),
+            _channel(name="secret", flag_value=DISCORD_CHANNEL_OBFUSCATED_FLAG, cid=2),
+            _channel(name=DISCORD_OBFUSCATED_CHANNEL_NAME, cid=3),
+        ],
+        forum_channels=[
+            _channel(name="forum-open", cid=4),
+            _channel(name="forum-secret", flag_value=DISCORD_CHANNEL_OBFUSCATED_FLAG, cid=5),
+        ],
     )
+    adapter = SimpleNamespace(_client=SimpleNamespace(guilds=[guild]))
+    monkeypatch.setattr(cd, "_build_from_sessions", lambda platform: [])
 
+    channels = cd._build_discord(adapter)
 
-class TestIsDiscordChannelObfuscated(unittest.TestCase):
-    def test_normal_channel_not_obfuscated(self):
-        self.assertFalse(is_discord_channel_obfuscated(_channel()))
-
-    def test_flag_marks_obfuscated(self):
-        ch = _channel(name="whatever", flag_value=DISCORD_CHANNEL_OBFUSCATED_FLAG)
-        self.assertTrue(is_discord_channel_obfuscated(ch))
-
-    def test_flag_combined_with_other_flags(self):
-        ch = _channel(flag_value=DISCORD_CHANNEL_OBFUSCATED_FLAG | (1 << 4))
-        self.assertTrue(is_discord_channel_obfuscated(ch))
-
-    def test_sentinel_name_marks_obfuscated_without_flag(self):
-        # Older discord.py builds may not surface the new flag bit; the
-        # sentinel name is the fallback signal.
-        ch = _channel(name=DISCORD_OBFUSCATED_CHANNEL_NAME, flag_value=0)
-        self.assertTrue(is_discord_channel_obfuscated(ch))
-
-    def test_missing_flags_attribute(self):
-        ch = SimpleNamespace(id=1, name="ok")
-        self.assertFalse(is_discord_channel_obfuscated(ch))
-
-    def test_non_int_flag_value_falls_back_to_name(self):
-        ch = SimpleNamespace(id=1, name="ok", flags=SimpleNamespace(value=None))
-        self.assertFalse(is_discord_channel_obfuscated(ch))
-
-
-class TestChannelDirectorySkipsObfuscated(unittest.TestCase):
-    def test_build_discord_filters_hidden_channels(self):
-        from gateway import channel_directory as cd
-
-        visible = _channel(name="general", cid=1)
-        hidden_flag = _channel(name="secret", flag_value=DISCORD_CHANNEL_OBFUSCATED_FLAG, cid=2)
-        hidden_name = _channel(name=DISCORD_OBFUSCATED_CHANNEL_NAME, cid=3)
-        visible_forum = _channel(name="forum-open", cid=4)
-        hidden_forum = _channel(
-            name="forum-secret", flag_value=DISCORD_CHANNEL_OBFUSCATED_FLAG, cid=5
-        )
-
-        guild = SimpleNamespace(
-            name="TestGuild",
-            text_channels=[visible, hidden_flag, hidden_name],
-            forum_channels=[visible_forum, hidden_forum],
-        )
-        adapter = SimpleNamespace(_client=SimpleNamespace(guilds=[guild]))
-
-        original = cd._build_from_sessions
-        cd._build_from_sessions = lambda platform: []
-        try:
-            channels = cd._build_discord(adapter)
-        finally:
-            cd._build_from_sessions = original
-
-        ids = {c["id"] for c in channels}
-        self.assertEqual(ids, {"1", "4"})
-        types = {c["id"]: c["type"] for c in channels}
-        self.assertEqual(types["1"], "channel")
-        self.assertEqual(types["4"], "forum")
-
-
-if __name__ == "__main__":
-    unittest.main()
+    assert {c["id"]: c["type"] for c in channels} == {"1": "channel", "4": "forum"}

tests/gateway/test_discord_missed_message_backfill.py

@@ -458,3 +458,18 @@ async def test_iter_candidates_keeps_latest_messages_when_window_exceeds_limit(a
     assert got == [2, 3, 4]
 
 
+@pytest.mark.asyncio
+async def test_iter_candidates_skips_obfuscated_channel_on_explicit_ids(adapter, monkeypatch):
+    """A channel the bot lost VIEW_CHANNEL on (Discord obfuscation) is dropped even when
+    listed by explicit id — history reads on it always fail (#90154)."""
+    from gateway.platforms.helpers import DISCORD_CHANNEL_OBFUSCATED_FLAG
+
+    visible = FakeChannel(channel_id=1, history_messages=[make_message(message_id=11)])
+    hidden = FakeChannel(channel_id=2, history_messages=[make_message(message_id=22)])
+    hidden.name = "___hidden___"
+    hidden.flags = SimpleNamespace(value=DISCORD_CHANNEL_OBFUSCATED_FLAG)
+    adapter._client.get_channel = lambda channel_id: {1: visible, 2: hidden}[channel_id]
+
+    got = [msg.id async for msg in adapter._iter_missed_message_backfill_candidates({"1", "2"})]
+
+    assert got == [11]