fix(slack): honor documented mention_patterns wake words

The Slack docs document `slack.mention_patterns` as custom wake words that
trigger the bot alongside `@mention`, and the config layer bridges the key into
the Slack adapter's `config.extra` — but the adapter never read it. With
`require_mention` on, a channel message containing a configured wake word (and
no literal `<@BOTUID>`) was silently ignored. Every other adapter that
documents `mention_patterns` (Telegram, DingTalk, Mattermost, WhatsApp,
BlueBubbles, Photon) implements it; Slack was the odd one out.

Add `_slack_mention_patterns()` (compiled, cached; reads `slack.mention_patterns`
as a list/string or `SLACK_MENTION_PATTERNS` as a JSON/CSV/newline list, invalid
regexes warned and skipped) and `_slack_message_matches_mention_patterns()`,
mirroring the existing adapters. Channel mention detection now also triggers on
a wake-word match, so the documented field works as described.

Adds tests for pattern compilation (list/string/env/invalid-regex) and for the
channel-trigger gating with a wake word under require_mention.

plugins/platforms/slack/adapter.py

@@ -2485,7 +2485,10 @@ class SlackAdapter(BasePlatformAdapter):
         #   4. There's an existing session for this thread (survives restarts)
         bot_uid = self._team_bot_user_ids.get(team_id, self._bot_user_id)
         routing_text = original_text or ""
-        is_mentioned = bot_uid and f"<@{bot_uid}>" in routing_text
+        is_mentioned = bool(
+            (bot_uid and f"<@{bot_uid}>" in routing_text)
+            or self._slack_message_matches_mention_patterns(routing_text)
+        )
         event_thread_ts = event.get("thread_ts")
         is_thread_reply = bool(event_thread_ts and event_thread_ts != ts)
 
@@ -3812,6 +3815,62 @@ class SlackAdapter(BasePlatformAdapter):
             return {part.strip() for part in raw.split(",") if part.strip()}
         return set()
 
+    def _slack_mention_patterns(self) -> List["re.Pattern"]:
+        """Compile optional regex wake-word patterns for channel triggers.
+
+        Parity with the other adapters (Telegram, DingTalk, Mattermost,
+        WhatsApp, BlueBubbles, Photon): when ``require_mention`` is on, a
+        channel message matching one of these patterns triggers the bot even
+        without a literal ``<@BOTUID>`` mention. Reads ``slack.mention_patterns``
+        (a list or single string) or ``SLACK_MENTION_PATTERNS`` (a JSON list, or
+        newline/comma-separated values). Compiled patterns are cached on the
+        instance. Previously this documented field was silently dropped.
+        """
+        cached = getattr(self, "_compiled_mention_patterns", None)
+        if cached is not None:
+            return cached
+
+        patterns = self.config.extra.get("mention_patterns") if self.config.extra else None
+        if patterns is None:
+            raw = os.getenv("SLACK_MENTION_PATTERNS", "").strip()
+            if raw:
+                try:
+                    import json as _json
+                    patterns = _json.loads(raw)
+                except Exception:
+                    patterns = [p.strip() for p in raw.splitlines() if p.strip()] or [
+                        p.strip() for p in raw.split(",") if p.strip()
+                    ]
+
+        if isinstance(patterns, str):
+            patterns = [patterns]
+
+        compiled: List["re.Pattern"] = []
+        if isinstance(patterns, list):
+            for pat in patterns:
+                if not isinstance(pat, str) or not pat.strip():
+                    continue
+                try:
+                    compiled.append(re.compile(pat, re.IGNORECASE))
+                except re.error as exc:
+                    logger.warning("[Slack] Invalid mention pattern %r: %s", pat, exc)
+        elif patterns is not None:
+            logger.warning(
+                "[Slack] mention_patterns must be a list or string; got %s",
+                type(patterns).__name__,
+            )
+
+        if compiled:
+            logger.info("[Slack] Loaded %d mention pattern(s)", len(compiled))
+        self._compiled_mention_patterns = compiled
+        return compiled
+
+    def _slack_message_matches_mention_patterns(self, text: str) -> bool:
+        """Return True when ``text`` matches a configured wake-word pattern."""
+        if not text:
+            return False
+        return any(pattern.search(text) for pattern in self._slack_mention_patterns())
+
 
 # ──────────────────────────────────────────────────────────────────────────
 # Plugin migration glue (#41112 / #3823)

tests/gateway/test_slack_mention.py

@@ -55,7 +55,8 @@ CHANNEL_ID = "C0AQWDLHY9M"
 OTHER_CHANNEL_ID = "C9999999999"
 
 
-def _make_adapter(require_mention=None, strict_mention=None, free_response_channels=None, allowed_channels=None):
+def _make_adapter(require_mention=None, strict_mention=None, free_response_channels=None,
+                  allowed_channels=None, mention_patterns=None):
     extra = {}
     if require_mention is not None:
         extra["require_mention"] = require_mention
@@ -65,6 +66,8 @@ def _make_adapter(require_mention=None, strict_mention=None, free_response_chann
         extra["free_response_channels"] = free_response_channels
     if allowed_channels is not None:
         extra["allowed_channels"] = allowed_channels
+    if mention_patterns is not None:
+        extra["mention_patterns"] = mention_patterns
 
     adapter = object.__new__(SlackAdapter)
     adapter.platform = Platform.SLACK
@@ -249,7 +252,10 @@ def _would_process(adapter, *, is_dm=False, channel_id=CHANNEL_ID,
     bot_uid = adapter._team_bot_user_ids.get("T1", adapter._bot_user_id)
     if mentioned:
         text = f"<@{bot_uid}> {text}"
-    is_mentioned = bot_uid and f"<@{bot_uid}>" in text
+    is_mentioned = bool(
+        (bot_uid and f"<@{bot_uid}>" in text)
+        or adapter._slack_message_matches_mention_patterns(text)
+    )
 
     if not is_dm and bot_uid:
         # allowed_channels check (whitelist — must pass before other gating)
@@ -687,3 +693,51 @@ def test_config_bridges_slack_allowed_channels_env_takes_precedence(monkeypatch,
     import os as _os
     # env var must not be overwritten by config.yaml
     assert _os.environ["SLACK_ALLOWED_CHANNELS"] == OTHER_CHANNEL_ID
+
+
+# ---------------------------------------------------------------------------
+# Tests: mention_patterns (wake words) — parity with other adapters (#50732)
+# ---------------------------------------------------------------------------
+
+def test_mention_patterns_default_no_match(monkeypatch):
+    monkeypatch.delenv("SLACK_MENTION_PATTERNS", raising=False)
+    adapter = _make_adapter()
+    assert adapter._slack_mention_patterns() == []
+    assert adapter._slack_message_matches_mention_patterns("hello there") is False
+
+
+def test_mention_patterns_list_matches():
+    adapter = _make_adapter(mention_patterns=["hey hermes", "hermes,"])
+    assert adapter._slack_message_matches_mention_patterns("hey hermes, you there?") is True
+    assert adapter._slack_message_matches_mention_patterns("just chatting") is False
+
+
+def test_mention_patterns_case_insensitive():
+    adapter = _make_adapter(mention_patterns=["hey hermes"])
+    assert adapter._slack_message_matches_mention_patterns("HEY HERMES!") is True
+
+
+def test_mention_patterns_single_string():
+    adapter = _make_adapter(mention_patterns="^hermes")
+    assert adapter._slack_message_matches_mention_patterns("hermes do this") is True
+    assert adapter._slack_message_matches_mention_patterns("ok hermes") is False
+
+
+def test_mention_patterns_invalid_regex_skipped_without_crash():
+    # An invalid pattern is dropped; valid siblings still work.
+    adapter = _make_adapter(mention_patterns=["(unclosed", "hey hermes"])
+    assert adapter._slack_message_matches_mention_patterns("hey hermes") is True
+
+
+def test_mention_patterns_env_var_fallback(monkeypatch):
+    monkeypatch.setenv("SLACK_MENTION_PATTERNS", '["hey hermes", "hermes,"]')
+    adapter = _make_adapter()  # no config value -> falls back to env
+    assert adapter._slack_message_matches_mention_patterns("hey hermes") is True
+
+
+def test_mention_patterns_trigger_in_channel_without_literal_mention():
+    """A wake word triggers the bot in a channel even with require_mention on."""
+    adapter = _make_adapter(require_mention=True, mention_patterns=["hey hermes"])
+    assert _would_process(adapter, text="hey hermes what's the status") is True
+    # Unrelated channel chatter is still ignored.
+    assert _would_process(adapter, text="lunch anyone?") is False