fix(gateway): mark unconfigured platforms as non-retryable to stop reconnect loop

A platform with a missing dependency or missing credentials can never
succeed on retry, but connect() returned bare False, so the gateway
treated the failure as transient and queued it for background
reconnection — looping forever at the backoff cap. Set
_set_fatal_error(..., retryable=False) for missing-dependency and
missing-credential failures in the Slack, Telegram, and Discord
adapters so the reconnect watcher drops them from the retry queue.

Salvaged from PR #31057 by @dskwe (reapplied onto the plugin-migrated
adapter paths). Fixes #31049.

plugins/platforms/discord/adapter.py

@@ -1037,6 +1037,7 @@ class DiscordAdapter(BasePlatformAdapter):
         """Connect to Discord and start receiving events."""
         if not DISCORD_AVAILABLE:
             logger.error("[%s] discord.py not installed. Run: pip install discord.py", self.name)
+            self._set_fatal_error("missing_dependency", "discord.py not installed", retryable=False)
             return False
 
         # Load opus codec for voice channel support
@@ -1073,6 +1074,7 @@ class DiscordAdapter(BasePlatformAdapter):
 
         if not self.config.token:
             logger.error("[%s] No bot token configured", self.name)
+            self._set_fatal_error("missing_credentials", "No bot token configured", retryable=False)
             return False
 
         try:

plugins/platforms/slack/adapter.py

@@ -1115,6 +1115,7 @@ class SlackAdapter(BasePlatformAdapter):
             logger.error(
                 "[Slack] slack-bolt not installed. Run: pip install slack-bolt",
             )
+            self._set_fatal_error("missing_dependency", "slack-bolt not installed", retryable=False)
             return False
 
         raw_token = self.config.token

plugins/platforms/telegram/adapter.py

@@ -3434,10 +3434,12 @@ class TelegramAdapter(BasePlatformAdapter):
                 "[%s] python-telegram-bot not installed. Run: pip install python-telegram-bot",
                 self.name,
             )
+            self._set_fatal_error("missing_dependency", "python-telegram-bot not installed", retryable=False)
             return False
         
         if not self.config.token:
             logger.error("[%s] No bot token configured", self.name)
+            self._set_fatal_error("missing_credentials", "No bot token configured", retryable=False)
             return False
         
         try:

tests/gateway/test_discord_connect.py

@@ -1076,3 +1076,37 @@ async def test_safe_sync_detects_contexts_drift():
     fake_http.edit_global_command.assert_not_awaited()
     fake_http.delete_global_command.assert_awaited_once_with(999, 77)
     fake_http.upsert_global_command.assert_awaited_once_with(999, desired)
+
+
+# ============================================================================
+# #31049: unconfigured platform skips reconnection (non-retryable fatal error)
+# ============================================================================
+
+class TestDiscordUnconfiguredNonRetryable:
+    """Verify that missing dependency/token sets a non-retryable fatal error
+    so the gateway does not queue the platform for background reconnection."""
+
+    @pytest.mark.asyncio
+    async def test_no_discord_lib_sets_non_retryable_fatal(self, monkeypatch):
+        """connect() with discord.py unavailable → non-retryable fatal error."""
+        _ensure_discord_mock()
+        adapter = DiscordAdapter(PlatformConfig(enabled=True, token="fake"))
+        # Simulate discord.py not installed
+        monkeypatch.setattr(discord_platform, "DISCORD_AVAILABLE", False)
+        result = await adapter.connect()
+        assert result is False
+        assert adapter.has_fatal_error is True
+        assert adapter.fatal_error_retryable is False
+        assert adapter.fatal_error_code == "missing_dependency"
+
+    @pytest.mark.asyncio
+    async def test_no_bot_token_sets_non_retryable_fatal(self, monkeypatch):
+        """connect() with empty token → non-retryable fatal error."""
+        _ensure_discord_mock()
+        monkeypatch.setattr(discord_platform, "DISCORD_AVAILABLE", True)
+        adapter = DiscordAdapter(PlatformConfig(enabled=True, token=""))
+        result = await adapter.connect()
+        assert result is False
+        assert adapter.has_fatal_error is True
+        assert adapter.fatal_error_retryable is False
+        assert adapter.fatal_error_code == "missing_credentials"

tests/gateway/test_telegram_connect.py

@@ -0,0 +1,66 @@
+"""Tests for Telegram connect() non-retryable fatal error on missing credentials.
+
+When Telegram has no bot token or no python-telegram-bot installed, connect()
+must set a non-retryable fatal error so the gateway does not queue it for
+background reconnection (#31049).
+"""
+
+import sys
+from unittest.mock import MagicMock
+
+import pytest
+
+from gateway.config import PlatformConfig
+
+
+def _ensure_telegram_mock():
+    if "telegram" in sys.modules and hasattr(sys.modules["telegram"], "__file__"):
+        return
+
+    telegram_mod = MagicMock()
+    telegram_mod.ext.ContextTypes.DEFAULT_TYPE = type(None)
+    telegram_mod.constants.ParseMode.MARKDOWN_V2 = "MarkdownV2"
+    telegram_mod.constants.ChatType.GROUP = "group"
+    telegram_mod.constants.ChatType.SUPERGROUP = "supergroup"
+    telegram_mod.constants.ChatType.CHANNEL = "channel"
+    telegram_mod.constants.ChatType.PRIVATE = "private"
+
+    telegram_mod.error.NetworkError = type("NetworkError", (OSError,), {})
+    telegram_mod.error.TimedOut = type("TimedOut", (OSError,), {})
+    telegram_mod.error.BadRequest = type("BadRequest", (Exception,), {})
+
+    for name in ("telegram", "telegram.ext", "telegram.constants", "telegram.request"):
+        sys.modules.setdefault(name, telegram_mod)
+    sys.modules.setdefault("telegram.error", telegram_mod.error)
+
+
+_ensure_telegram_mock()
+
+import plugins.platforms.telegram.adapter as telegram_mod  # noqa: E402
+from plugins.platforms.telegram.adapter import TelegramAdapter  # noqa: E402
+
+
+class TestTelegramUnconfiguredNonRetryable:
+    """Verify that missing dependency/token sets a non-retryable fatal error."""
+
+    @pytest.mark.asyncio
+    async def test_no_telegram_lib_sets_non_retryable_fatal(self, monkeypatch):
+        """connect() with python-telegram-bot unavailable → non-retryable fatal error."""
+        adapter = TelegramAdapter(PlatformConfig(enabled=True, token="fake"))
+        monkeypatch.setattr(telegram_mod, "TELEGRAM_AVAILABLE", False)
+        result = await adapter.connect()
+        assert result is False
+        assert adapter.has_fatal_error is True
+        assert adapter.fatal_error_retryable is False
+        assert adapter.fatal_error_code == "missing_dependency"
+
+    @pytest.mark.asyncio
+    async def test_no_bot_token_sets_non_retryable_fatal(self, monkeypatch):
+        """connect() with empty token → non-retryable fatal error."""
+        monkeypatch.setattr(telegram_mod, "TELEGRAM_AVAILABLE", True)
+        adapter = TelegramAdapter(PlatformConfig(enabled=True, token=""))
+        result = await adapter.connect()
+        assert result is False
+        assert adapter.has_fatal_error is True
+        assert adapter.fatal_error_retryable is False
+        assert adapter.fatal_error_code == "missing_credentials"