feat(slack): add link unfurl controls

cli-config.yaml.example

@@ -1214,6 +1214,10 @@ platform_toolsets:
 #       # Render live tool calls as Slack-native plan/task cards. This explicit
 #       # opt-in works even though Slack text tool_progress defaults to off.
 #       native_task_cards: false
+#       # Suppress automatic link-preview cards without removing clickable links.
+#       # Omit either key to preserve Slack's default for that preview type.
+#       unfurl_links: false
+#       unfurl_media: false
 #   webhook:
 #     extra:
 #       # Route scripts default to a 30 second timeout. Scripts must live under

plugins/platforms/slack/adapter.py

@@ -79,6 +79,21 @@ _HERMES_SLACK_USER_AGENT_PREFIX = f"HermesAgent/{_HERMES_VERSION}"
 _SLACK_ERROR_BODY_LIMIT_BYTES = 8 * 1024
 
 
+def _slack_unfurl_kwargs(extra: Optional[Dict[str, Any]]) -> Dict[str, bool]:
+    """Return explicitly configured Slack link-preview controls.
+
+    Omitting a key preserves Slack's existing default.  Passing ``False``
+    suppresses only the automatic preview while leaving the link text and URL
+    in the message untouched.
+    """
+    settings = extra or {}
+    return {
+        key: settings[key]
+        for key in ("unfurl_links", "unfurl_media")
+        if isinstance(settings.get(key), bool)
+    }
+
+
 async def _read_error_text_limited(
     response: Any,
     *,
@@ -2988,6 +3003,7 @@ class SlackAdapter(BasePlatformAdapter):
                     "channel": chat_id,
                     "text": chunk,
                     "mrkdwn": True,
+                    **_slack_unfurl_kwargs(self.config.extra),
                 }
                 if blocks and i == 0:
                     kwargs["blocks"] = blocks
@@ -9474,6 +9490,7 @@ async def _standalone_send(
                 "channel": chat_id,
                 "text": text_to_send,
                 "mrkdwn": True,
+                **_slack_unfurl_kwargs(pconfig.extra),
             }
             if thread_id:
                 post_kwargs["thread_ts"] = thread_id
@@ -9589,7 +9606,12 @@ async def _standalone_send(
         async with aiohttp.ClientSession(
             timeout=aiohttp.ClientTimeout(total=30), **_sess_kw
         ) as session:
-            payload = {"channel": chat_id, "text": formatted, "mrkdwn": True}
+            payload = {
+                "channel": chat_id,
+                "text": formatted,
+                "mrkdwn": True,
+                **_slack_unfurl_kwargs(pconfig.extra),
+            }
             if thread_id:
                 payload["thread_ts"] = thread_id
             for tok in tokens:

tests/gateway/test_slack.py

@@ -1180,6 +1180,30 @@ class TestStandaloneSendUserDmResolution:
         assert session.post.call_count == 1
         assert "chat.postMessage" in session.post.call_args.args[0]
 
+    @pytest.mark.asyncio
+    async def test_channel_delivery_honors_unfurl_config(self):
+        _slack_mod._slack_dm_cache.clear()
+        post_resp = self._mock_resp({"ok": True, "ts": "123.456"})
+        session = self._mock_session(post_resp)
+        config = PlatformConfig(
+            enabled=True,
+            token="«redacted:xox…»",
+            extra={"unfurl_links": False, "unfurl_media": False},
+        )
+
+        with patch.object(_slack_mod.aiohttp, "ClientSession", return_value=session):
+            result = await _slack_mod._standalone_send(
+                config,
+                "C123",
+                "[Hermes](https://example.com/hermes)",
+            )
+
+        assert result["success"] is True
+        payload = session.post.call_args.kwargs["json"]
+        assert payload["text"] == "<https://example.com/hermes|Hermes>"
+        assert payload["unfurl_links"] is False
+        assert payload["unfurl_media"] is False
+
 
     @pytest.mark.asyncio
     async def test_user_id_media_delivery_resolves_dm_before_upload(self, tmp_path):

tests/gateway/test_slack_block_kit_adapter.py

@@ -66,6 +66,20 @@ class TestSendMessageBlocks:
         assert "blocks" not in kwargs
         assert kwargs["text"]  # plain text still sent
 
+    @pytest.mark.asyncio
+    async def test_unfurl_config_suppresses_previews_without_changing_link_text(self):
+        adapter, client = _make_adapter(
+            {"unfurl_links": False, "unfurl_media": False}
+        )
+        content = "[Hermes](https://example.com/hermes)"
+
+        await adapter.send("C1", content)
+
+        kwargs = client.chat_postMessage.await_args.kwargs
+        assert kwargs["text"] == "<https://example.com/hermes|Hermes>"
+        assert kwargs["unfurl_links"] is False
+        assert kwargs["unfurl_media"] is False
+
 
     @pytest.mark.asyncio
     async def test_enabled_but_unrenderable_falls_back_to_text(self):

website/docs/user-guide/messaging/slack.md

@@ -410,6 +410,12 @@ platforms:
       # Only the first chunk of the first reply is broadcast.
       reply_broadcast: false
 
+      # Control Slack's automatic link-preview cards without changing or
+      # removing clickable links from message text. Omit either key to keep
+      # Slack's default behavior for that preview type.
+      unfurl_links: false
+      unfurl_media: false
+
       # Render agent messages as Slack Block Kit blocks (default: false).
       # When true, the final agent message is sent with structured blocks —
       # section headers, dividers, true nested lists (via rich_text), and
@@ -458,6 +464,8 @@ platforms:
 | `platforms.slack.reply_to_mode` | `"first"` | Threading mode for multi-part messages: `"off"`, `"first"`, or `"all"` |
 | `platforms.slack.extra.reply_in_thread` | `true` | When `false`, channel messages get direct replies instead of threads. Messages inside existing threads still reply in-thread. |
 | `platforms.slack.extra.reply_broadcast` | `false` | When `true`, thread replies are also posted to the main channel. Only the first chunk is broadcast. |
+| `platforms.slack.extra.unfurl_links` | Slack default | Set to `false` to suppress automatic previews for linked web pages while preserving clickable links. |
+| `platforms.slack.extra.unfurl_media` | Slack default | Set to `false` to suppress automatic media previews while preserving clickable links. |
 | `platforms.slack.extra.rich_blocks` | `false` | When `true`, agent messages are rendered as [Block Kit](https://docs.slack.dev/block-kit/) blocks (headers, dividers, true nested lists, and native tables). A plain-text fallback is always sent. Tables over Slack's limits fall back to aligned monospace. No app reinstall required — it's a send-side change only. |
 | `platforms.slack.extra.feedback_buttons` | `false` | When `true` with `rich_blocks`, appends Slack-native feedback controls to final replies. |
 | `platforms.slack.extra.native_task_cards` | `false` | When `true`, renders live tool calls as Slack-native plan/task cards. This is an explicit progress opt-in independent of Slack's default `tool_progress: off`; native API failures fall back to one continuously edited text update. |