diff --git a/tests/conftest.py b/tests/conftest.py
index f9ad9d9b..65f40024 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -440,6 +440,19 @@ def _reset_module_state():
     except Exception:
         pass
 
+    # --- gateway.platforms.discord — module reload anti-pattern guard ---
+    # ``test_discord_imports.py`` deletes and re-imports this module with
+    # ``DISCORD_AVAILABLE=False``, corrupting state for every subsequent
+    # discord test in the same xdist worker (including e2e tests). Reset
+    # the flag and module reference before every test.
+    try:
+        import gateway.platforms.discord as _dp_mod
+        _dp_mod.DISCORD_AVAILABLE = True
+        if getattr(_dp_mod, "discord", None) is None and "discord" in sys.modules:
+            _dp_mod.discord = sys.modules["discord"]
+    except Exception:
+        pass
+
     yield
 
 
diff --git a/tests/e2e/conftest.py b/tests/e2e/conftest.py
index 76b14e31..ce87e643 100644
--- a/tests/e2e/conftest.py
+++ b/tests/e2e/conftest.py
@@ -37,6 +37,10 @@ def _ensure_telegram_mock():
     telegram_mod.Update.ALL_TYPES = []
     telegram_mod.Bot = MagicMock
     telegram_mod.constants.ParseMode.MARKDOWN_V2 = "MarkdownV2"
+    telegram_mod.constants.ChatType.PRIVATE = "private"
+    telegram_mod.constants.ChatType.GROUP = "group"
+    telegram_mod.constants.ChatType.SUPERGROUP = "supergroup"
+    telegram_mod.constants.ChatType.CHANNEL = "channel"
     telegram_mod.ext.Application = MagicMock()
     telegram_mod.ext.Application.builder = MagicMock
     telegram_mod.ext.ContextTypes.DEFAULT_TYPE = type(None)
@@ -123,6 +127,29 @@ _slack_mod.SLACK_AVAILABLE = True
 from gateway.platforms.slack import SlackAdapter  # noqa: E402
 
 
+@pytest.fixture(autouse=True)
+def _ensure_e2e_discord_state():
+    """Synchronise gateway.platforms.discord.discord with the e2e mock.
+
+    Other test files may replace ``sys.modules['discord']`` or reload
+    ``gateway.platforms.discord``, causing the cached ``DiscordAdapter``
+    class (imported at module level above) to reference a stale ``discord``
+    module.  If ``discord.MessageType`` or ``discord.DMChannel`` become
+    different MagicMock objects, ``isinstance`` checks in
+    ``DiscordAdapter._handle_message`` silently drop messages.
+
+    This fixture forces ``gateway.platforms.discord.discord`` back to the
+    same mock object the e2e conftest uses, so message-type comparisons
+    match.
+    """
+    import gateway.platforms.discord as _dp_mod
+
+    _dp_mod.DISCORD_AVAILABLE = True
+    if "discord" in sys.modules:
+        _dp_mod.discord = sys.modules["discord"]
+    yield
+
+
 # Platform-generic factories
 
 def make_source(platform: Platform, chat_id: str = "e2e-chat-1", user_id: str = "e2e-user-1", chat_type: str = "dm") -> SessionSource:
@@ -329,12 +356,28 @@ def make_fake_text_channel(channel_id: int = CHANNEL_ID, name: str = "general",
     )
 
 
+def _discord_for_helpers():
+    """Return the ``discord`` module that DiscordAdapter uses at runtime.
+
+    The module-level ``discord`` import in this conftest may diverge from
+    the one cached in DiscordAdapter's globals after other tests reload or
+    replace ``gateway.platforms.discord``.  Using the same object for
+    ``__class__`` assignment ensures ``isinstance`` checks in
+    ``_handle_message`` match.
+    """
+    _d = DiscordAdapter.__init__.__globals__.get("discord")
+    if _d is not None:
+        return _d
+    # Fallback to the module-level import (should never be needed).
+    return discord
+
+
 def make_fake_dm_channel(channel_id: int = 55555):
     ch = MagicMock(spec=[])
     ch.id = channel_id
     ch.name = "DM"
     ch.topic = None
-    ch.__class__ = discord.DMChannel
+    ch.__class__ = _discord_for_helpers().DMChannel
     return ch
 
 
@@ -347,7 +390,7 @@ def make_fake_thread(thread_id: int = THREAD_ID, name: str = "test-thread", pare
     th.guild = th.parent.guild
     th.topic = None
     th.type = 11
-    th.__class__ = discord.Thread
+    th.__class__ = _discord_for_helpers().Thread
     return th
 
 
@@ -372,7 +415,7 @@ def make_discord_message(
         id=message_id, content=content, author=author, channel=channel,
         guild=getattr(channel, "guild", None),
         mentions=mentions, attachments=attachments,
-        type=getattr(discord, "MessageType", SimpleNamespace()).default,
+        type=getattr(_discord_for_helpers(), "MessageType", SimpleNamespace()).default,
         reference=None, created_at=datetime.now(timezone.utc),
         create_thread=AsyncMock(),
     )
diff --git a/tests/gateway/conftest.py b/tests/gateway/conftest.py
index b159c1b2..d4bc8be1 100644
--- a/tests/gateway/conftest.py
+++ b/tests/gateway/conftest.py
@@ -82,6 +82,13 @@ def _ensure_telegram_mock() -> None:
         sys.modules[name] = mod
     sys.modules["telegram.error"] = mod.error
 
+    # If another test file (e.g. e2e/conftest) imported gateway.platforms.telegram
+    # while a different mock was in sys.modules, the cached production module still
+    # holds stale references. Reload so it picks up the comprehensive mock above.
+    if "gateway.platforms.telegram" in sys.modules:
+        import importlib
+        importlib.reload(sys.modules["gateway.platforms.telegram"])
+
 
 def _ensure_openai_mock() -> None:
     """Install a minimal openai mock in sys.modules.
diff --git a/tests/integration/test_modal_terminal.py b/tests/integration/test_modal_terminal.py
index a4fc2699..170323f7 100644
--- a/tests/integration/test_modal_terminal.py
+++ b/tests/integration/test_modal_terminal.py
@@ -44,11 +44,24 @@ sys.path.insert(0, str(parent_dir))
 
 # Import terminal_tool module directly using importlib to avoid tools/__init__.py
 import importlib.util
+from tools.registry import registry
+
 terminal_tool_path = parent_dir / "tools" / "terminal_tool.py"
 spec = importlib.util.spec_from_file_location("terminal_tool", terminal_tool_path)
 terminal_module = importlib.util.module_from_spec(spec)
+
+# Save the original registry entry before exec_module overwrites it with the
+# re-executed module's check_terminal_requirements.
+_original_terminal_entry = registry.get_entry("terminal")
+
 spec.loader.exec_module(terminal_module)
 
+# Restore the original registry entry so that subsequent tests which
+# monkeypatch tools.terminal_tool._get_env_config still affect the
+# check_fn that the registry actually uses.
+if _original_terminal_entry is not None:
+    registry._tools["terminal"] = _original_terminal_entry
+
 terminal_tool = terminal_module.terminal_tool
 check_terminal_requirements = terminal_module.check_terminal_requirements
 _get_env_config = terminal_module._get_env_config