diff --git a/gateway/platforms/slack.py b/gateway/platforms/slack.py
index 11a73461e7..020843d3ac 100644
--- a/gateway/platforms/slack.py
+++ b/gateway/platforms/slack.py
@@ -10,6 +10,7 @@ Uses slack-bolt (Python) with Socket Mode for:
 
 import asyncio
 import os
+import re
 from typing import Dict, List, Optional, Any
 
 try:
@@ -33,6 +34,8 @@ from gateway.platforms.base import (
     MessageEvent,
     MessageType,
     SendResult,
+    SUPPORTED_DOCUMENT_TYPES,
+    cache_document_from_bytes,
     cache_image_from_url,
     cache_audio_from_url,
 )
@@ -96,6 +99,13 @@ class SlackAdapter(BasePlatformAdapter):
             async def handle_message_event(event, say):
                 await self._handle_slack_message(event)
 
+            # Acknowledge app_mention events to prevent Bolt 404 errors.
+            # The "message" handler above already processes @mentions in
+            # channels, so this is intentionally a no-op to avoid duplicates.
+            @self._app.event("app_mention")
+            async def handle_app_mention(event, say):
+                pass
+
             # Register slash command handler
             @self._app.command("/hermes")
             async def handle_hermes_command(ack, command):
@@ -266,6 +276,65 @@ class SlackAdapter(BasePlatformAdapter):
         except Exception as e:
             return SendResult(success=False, error=str(e))
 
+    async def send_video(
+        self,
+        chat_id: str,
+        video_path: str,
+        caption: Optional[str] = None,
+        reply_to: Optional[str] = None,
+    ) -> SendResult:
+        """Send a video file to Slack."""
+        if not self._app:
+            return SendResult(success=False, error="Not connected")
+
+        if not os.path.exists(video_path):
+            return SendResult(success=False, error=f"Video file not found: {video_path}")
+
+        try:
+            result = await self._app.client.files_upload_v2(
+                channel=chat_id,
+                file=video_path,
+                filename=os.path.basename(video_path),
+                initial_comment=caption or "",
+                thread_ts=reply_to,
+            )
+            return SendResult(success=True, raw_response=result)
+
+        except Exception as e:
+            print(f"[{self.name}] Failed to send video: {e}")
+            return await super().send_video(chat_id, video_path, caption, reply_to)
+
+    async def send_document(
+        self,
+        chat_id: str,
+        file_path: str,
+        caption: Optional[str] = None,
+        file_name: Optional[str] = None,
+        reply_to: Optional[str] = None,
+    ) -> SendResult:
+        """Send a document/file attachment to Slack."""
+        if not self._app:
+            return SendResult(success=False, error="Not connected")
+
+        if not os.path.exists(file_path):
+            return SendResult(success=False, error=f"File not found: {file_path}")
+
+        display_name = file_name or os.path.basename(file_path)
+
+        try:
+            result = await self._app.client.files_upload_v2(
+                channel=chat_id,
+                file=file_path,
+                filename=display_name,
+                initial_comment=caption or "",
+                thread_ts=reply_to,
+            )
+            return SendResult(success=True, raw_response=result)
+
+        except Exception as e:
+            print(f"[{self.name}] Failed to send document: {e}")
+            return await super().send_document(chat_id, file_path, caption, file_name, reply_to)
+
     async def get_chat_info(self, chat_id: str) -> Dict[str, Any]:
         """Get information about a Slack channel."""
         if not self._app:
@@ -347,6 +416,58 @@ class SlackAdapter(BasePlatformAdapter):
                     msg_type = MessageType.VOICE
                 except Exception as e:
                     print(f"[Slack] Failed to cache audio: {e}", flush=True)
+            elif url:
+                # Try to handle as a document attachment
+                try:
+                    original_filename = f.get("name", "")
+                    ext = ""
+                    if original_filename:
+                        _, ext = os.path.splitext(original_filename)
+                        ext = ext.lower()
+
+                    # Fallback: reverse-lookup from MIME type
+                    if not ext and mimetype:
+                        mime_to_ext = {v: k for k, v in SUPPORTED_DOCUMENT_TYPES.items()}
+                        ext = mime_to_ext.get(mimetype, "")
+
+                    if ext not in SUPPORTED_DOCUMENT_TYPES:
+                        continue  # Skip unsupported file types silently
+
+                    # Check file size (Slack limit: 20 MB for bots)
+                    file_size = f.get("size", 0)
+                    MAX_DOC_BYTES = 20 * 1024 * 1024
+                    if not file_size or file_size > MAX_DOC_BYTES:
+                        print(f"[Slack] Document too large or unknown size: {file_size}", flush=True)
+                        continue
+
+                    # Download and cache
+                    raw_bytes = await self._download_slack_file_bytes(url)
+                    cached_path = cache_document_from_bytes(
+                        raw_bytes, original_filename or f"document{ext}"
+                    )
+                    doc_mime = SUPPORTED_DOCUMENT_TYPES[ext]
+                    media_urls.append(cached_path)
+                    media_types.append(doc_mime)
+                    msg_type = MessageType.DOCUMENT
+                    print(f"[Slack] Cached user document: {cached_path}", flush=True)
+
+                    # Inject text content for .txt/.md files (capped at 100 KB)
+                    MAX_TEXT_INJECT_BYTES = 100 * 1024
+                    if ext in (".md", ".txt") and len(raw_bytes) <= MAX_TEXT_INJECT_BYTES:
+                        try:
+                            text_content = raw_bytes.decode("utf-8")
+                            display_name = original_filename or f"document{ext}"
+                            display_name = re.sub(r'[^\w.\- ]', '_', display_name)
+                            injection = f"[Content of {display_name}]:\n{text_content}"
+                            if text:
+                                text = f"{injection}\n\n{text}"
+                            else:
+                                text = injection
+                        except UnicodeDecodeError:
+                            pass  # Binary content, skip injection
+
+                except Exception as e:
+                    print(f"[Slack] Failed to cache document: {e}", flush=True)
 
         # Build source
         source = self.build_source(
@@ -427,3 +548,16 @@ class SlackAdapter(BasePlatformAdapter):
         else:
             from gateway.platforms.base import cache_image_from_bytes
             return cache_image_from_bytes(response.content, ext)
+
+    async def _download_slack_file_bytes(self, url: str) -> bytes:
+        """Download a Slack file and return raw bytes."""
+        import httpx
+
+        bot_token = self.config.token
+        async with httpx.AsyncClient(timeout=30.0, follow_redirects=True) as client:
+            response = await client.get(
+                url,
+                headers={"Authorization": f"Bearer {bot_token}"},
+            )
+            response.raise_for_status()
+        return response.content
diff --git a/tests/gateway/test_slack.py b/tests/gateway/test_slack.py
new file mode 100644
index 0000000000..efdb62ce49
--- /dev/null
+++ b/tests/gateway/test_slack.py
@@ -0,0 +1,532 @@
+"""
+Tests for Slack platform adapter.
+
+Covers: app_mention handler, send_document, send_video,
+        incoming document handling, message routing.
+
+Note: slack-bolt may not be installed in the test environment.
+We mock the slack modules at import time to avoid collection errors.
+"""
+
+import asyncio
+import os
+import sys
+from unittest.mock import AsyncMock, MagicMock, patch
+
+import pytest
+
+from gateway.config import Platform, PlatformConfig
+from gateway.platforms.base import (
+    MessageEvent,
+    MessageType,
+    SendResult,
+    SUPPORTED_DOCUMENT_TYPES,
+)
+
+
+# ---------------------------------------------------------------------------
+# Mock the slack-bolt package if it's not installed
+# ---------------------------------------------------------------------------
+
+def _ensure_slack_mock():
+    """Install mock slack modules so SlackAdapter can be imported."""
+    if "slack_bolt" in sys.modules and hasattr(sys.modules["slack_bolt"], "__file__"):
+        return  # Real library installed
+
+    slack_bolt = MagicMock()
+    slack_bolt.async_app.AsyncApp = MagicMock
+    slack_bolt.adapter.socket_mode.async_handler.AsyncSocketModeHandler = MagicMock
+
+    slack_sdk = MagicMock()
+    slack_sdk.web.async_client.AsyncWebClient = MagicMock
+
+    for name, mod in [
+        ("slack_bolt", slack_bolt),
+        ("slack_bolt.async_app", slack_bolt.async_app),
+        ("slack_bolt.adapter", slack_bolt.adapter),
+        ("slack_bolt.adapter.socket_mode", slack_bolt.adapter.socket_mode),
+        ("slack_bolt.adapter.socket_mode.async_handler", slack_bolt.adapter.socket_mode.async_handler),
+        ("slack_sdk", slack_sdk),
+        ("slack_sdk.web", slack_sdk.web),
+        ("slack_sdk.web.async_client", slack_sdk.web.async_client),
+    ]:
+        sys.modules.setdefault(name, mod)
+
+
+_ensure_slack_mock()
+
+# Patch SLACK_AVAILABLE before importing the adapter
+import gateway.platforms.slack as _slack_mod
+_slack_mod.SLACK_AVAILABLE = True
+
+from gateway.platforms.slack import SlackAdapter  # noqa: E402
+
+
+# ---------------------------------------------------------------------------
+# Fixtures
+# ---------------------------------------------------------------------------
+
+@pytest.fixture()
+def adapter():
+    config = PlatformConfig(enabled=True, token="xoxb-fake-token")
+    a = SlackAdapter(config)
+    # Mock the Slack app client
+    a._app = MagicMock()
+    a._app.client = AsyncMock()
+    a._bot_user_id = "U_BOT"
+    a._running = True
+    # Capture events instead of processing them
+    a.handle_message = AsyncMock()
+    return a
+
+
+@pytest.fixture(autouse=True)
+def _redirect_cache(tmp_path, monkeypatch):
+    """Point document cache to tmp_path so tests don't touch ~/.hermes."""
+    monkeypatch.setattr(
+        "gateway.platforms.base.DOCUMENT_CACHE_DIR", tmp_path / "doc_cache"
+    )
+
+
+# ---------------------------------------------------------------------------
+# TestAppMentionHandler
+# ---------------------------------------------------------------------------
+
+class TestAppMentionHandler:
+    """Verify that the app_mention event handler is registered."""
+
+    def test_app_mention_registered_on_connect(self):
+        """connect() should register both 'message' and 'app_mention' handlers."""
+        config = PlatformConfig(enabled=True, token="xoxb-fake")
+        adapter = SlackAdapter(config)
+
+        # Track which events get registered
+        registered_events = []
+        registered_commands = []
+
+        mock_app = MagicMock()
+
+        def mock_event(event_type):
+            def decorator(fn):
+                registered_events.append(event_type)
+                return fn
+            return decorator
+
+        def mock_command(cmd):
+            def decorator(fn):
+                registered_commands.append(cmd)
+                return fn
+            return decorator
+
+        mock_app.event = mock_event
+        mock_app.command = mock_command
+        mock_app.client = AsyncMock()
+        mock_app.client.auth_test = AsyncMock(return_value={
+            "user_id": "U_BOT",
+            "user": "testbot",
+        })
+
+        with patch.object(_slack_mod, "AsyncApp", return_value=mock_app), \
+             patch.object(_slack_mod, "AsyncSocketModeHandler", return_value=MagicMock()), \
+             patch.dict(os.environ, {"SLACK_APP_TOKEN": "xapp-fake"}), \
+             patch("asyncio.create_task"):
+            asyncio.get_event_loop().run_until_complete(adapter.connect())
+
+        assert "message" in registered_events
+        assert "app_mention" in registered_events
+        assert "/hermes" in registered_commands
+
+
+# ---------------------------------------------------------------------------
+# TestSendDocument
+# ---------------------------------------------------------------------------
+
+class TestSendDocument:
+    @pytest.mark.asyncio
+    async def test_send_document_success(self, adapter, tmp_path):
+        test_file = tmp_path / "report.pdf"
+        test_file.write_bytes(b"%PDF-1.4 fake content")
+
+        adapter._app.client.files_upload_v2 = AsyncMock(return_value={"ok": True})
+
+        result = await adapter.send_document(
+            chat_id="C123",
+            file_path=str(test_file),
+            caption="Here's the report",
+        )
+
+        assert result.success
+        adapter._app.client.files_upload_v2.assert_called_once()
+        call_kwargs = adapter._app.client.files_upload_v2.call_args[1]
+        assert call_kwargs["channel"] == "C123"
+        assert call_kwargs["file"] == str(test_file)
+        assert call_kwargs["filename"] == "report.pdf"
+        assert call_kwargs["initial_comment"] == "Here's the report"
+
+    @pytest.mark.asyncio
+    async def test_send_document_custom_name(self, adapter, tmp_path):
+        test_file = tmp_path / "data.csv"
+        test_file.write_bytes(b"a,b,c\n1,2,3")
+
+        adapter._app.client.files_upload_v2 = AsyncMock(return_value={"ok": True})
+
+        result = await adapter.send_document(
+            chat_id="C123",
+            file_path=str(test_file),
+            file_name="quarterly-report.csv",
+        )
+
+        assert result.success
+        call_kwargs = adapter._app.client.files_upload_v2.call_args[1]
+        assert call_kwargs["filename"] == "quarterly-report.csv"
+
+    @pytest.mark.asyncio
+    async def test_send_document_missing_file(self, adapter):
+        result = await adapter.send_document(
+            chat_id="C123",
+            file_path="/nonexistent/file.pdf",
+        )
+
+        assert not result.success
+        assert "not found" in result.error.lower()
+
+    @pytest.mark.asyncio
+    async def test_send_document_not_connected(self, adapter):
+        adapter._app = None
+        result = await adapter.send_document(
+            chat_id="C123",
+            file_path="/some/file.pdf",
+        )
+
+        assert not result.success
+        assert "Not connected" in result.error
+
+    @pytest.mark.asyncio
+    async def test_send_document_api_error_falls_back(self, adapter, tmp_path):
+        test_file = tmp_path / "doc.pdf"
+        test_file.write_bytes(b"content")
+
+        adapter._app.client.files_upload_v2 = AsyncMock(
+            side_effect=RuntimeError("Slack API error")
+        )
+
+        # Should fall back to base class (text message)
+        result = await adapter.send_document(
+            chat_id="C123",
+            file_path=str(test_file),
+        )
+
+        # Base class send() is also mocked, so check it was attempted
+        adapter._app.client.chat_postMessage.assert_called_once()
+
+    @pytest.mark.asyncio
+    async def test_send_document_with_thread(self, adapter, tmp_path):
+        test_file = tmp_path / "notes.txt"
+        test_file.write_bytes(b"some notes")
+
+        adapter._app.client.files_upload_v2 = AsyncMock(return_value={"ok": True})
+
+        result = await adapter.send_document(
+            chat_id="C123",
+            file_path=str(test_file),
+            reply_to="1234567890.123456",
+        )
+
+        assert result.success
+        call_kwargs = adapter._app.client.files_upload_v2.call_args[1]
+        assert call_kwargs["thread_ts"] == "1234567890.123456"
+
+
+# ---------------------------------------------------------------------------
+# TestSendVideo
+# ---------------------------------------------------------------------------
+
+class TestSendVideo:
+    @pytest.mark.asyncio
+    async def test_send_video_success(self, adapter, tmp_path):
+        video = tmp_path / "clip.mp4"
+        video.write_bytes(b"fake video data")
+
+        adapter._app.client.files_upload_v2 = AsyncMock(return_value={"ok": True})
+
+        result = await adapter.send_video(
+            chat_id="C123",
+            video_path=str(video),
+            caption="Check this out",
+        )
+
+        assert result.success
+        call_kwargs = adapter._app.client.files_upload_v2.call_args[1]
+        assert call_kwargs["filename"] == "clip.mp4"
+        assert call_kwargs["initial_comment"] == "Check this out"
+
+    @pytest.mark.asyncio
+    async def test_send_video_missing_file(self, adapter):
+        result = await adapter.send_video(
+            chat_id="C123",
+            video_path="/nonexistent/video.mp4",
+        )
+
+        assert not result.success
+        assert "not found" in result.error.lower()
+
+    @pytest.mark.asyncio
+    async def test_send_video_not_connected(self, adapter):
+        adapter._app = None
+        result = await adapter.send_video(
+            chat_id="C123",
+            video_path="/some/video.mp4",
+        )
+
+        assert not result.success
+        assert "Not connected" in result.error
+
+    @pytest.mark.asyncio
+    async def test_send_video_api_error_falls_back(self, adapter, tmp_path):
+        video = tmp_path / "clip.mp4"
+        video.write_bytes(b"fake video")
+
+        adapter._app.client.files_upload_v2 = AsyncMock(
+            side_effect=RuntimeError("Slack API error")
+        )
+
+        # Should fall back to base class (text message)
+        result = await adapter.send_video(
+            chat_id="C123",
+            video_path=str(video),
+        )
+
+        adapter._app.client.chat_postMessage.assert_called_once()
+
+
+# ---------------------------------------------------------------------------
+# TestIncomingDocumentHandling
+# ---------------------------------------------------------------------------
+
+class TestIncomingDocumentHandling:
+    def _make_event(self, files=None, text="hello", channel_type="im"):
+        """Build a mock Slack message event with file attachments."""
+        return {
+            "text": text,
+            "user": "U_USER",
+            "channel": "C123",
+            "channel_type": channel_type,
+            "ts": "1234567890.000001",
+            "files": files or [],
+        }
+
+    @pytest.mark.asyncio
+    async def test_pdf_document_cached(self, adapter):
+        """A PDF attachment should be downloaded, cached, and set as DOCUMENT type."""
+        pdf_bytes = b"%PDF-1.4 fake content"
+
+        with patch.object(adapter, "_download_slack_file_bytes", new_callable=AsyncMock) as dl:
+            dl.return_value = pdf_bytes
+            event = self._make_event(files=[{
+                "mimetype": "application/pdf",
+                "name": "report.pdf",
+                "url_private_download": "https://files.slack.com/report.pdf",
+                "size": len(pdf_bytes),
+            }])
+            await adapter._handle_slack_message(event)
+
+        msg_event = adapter.handle_message.call_args[0][0]
+        assert msg_event.message_type == MessageType.DOCUMENT
+        assert len(msg_event.media_urls) == 1
+        assert os.path.exists(msg_event.media_urls[0])
+        assert msg_event.media_types == ["application/pdf"]
+
+    @pytest.mark.asyncio
+    async def test_txt_document_injects_content(self, adapter):
+        """A .txt file under 100KB should have its content injected into event text."""
+        content = b"Hello from a text file"
+
+        with patch.object(adapter, "_download_slack_file_bytes", new_callable=AsyncMock) as dl:
+            dl.return_value = content
+            event = self._make_event(
+                text="summarize this",
+                files=[{
+                    "mimetype": "text/plain",
+                    "name": "notes.txt",
+                    "url_private_download": "https://files.slack.com/notes.txt",
+                    "size": len(content),
+                }],
+            )
+            await adapter._handle_slack_message(event)
+
+        msg_event = adapter.handle_message.call_args[0][0]
+        assert "Hello from a text file" in msg_event.text
+        assert "[Content of notes.txt]" in msg_event.text
+        assert "summarize this" in msg_event.text
+
+    @pytest.mark.asyncio
+    async def test_md_document_injects_content(self, adapter):
+        """A .md file under 100KB should have its content injected."""
+        content = b"# Title\nSome markdown content"
+
+        with patch.object(adapter, "_download_slack_file_bytes", new_callable=AsyncMock) as dl:
+            dl.return_value = content
+            event = self._make_event(files=[{
+                "mimetype": "text/markdown",
+                "name": "readme.md",
+                "url_private_download": "https://files.slack.com/readme.md",
+                "size": len(content),
+            }], text="")
+            await adapter._handle_slack_message(event)
+
+        msg_event = adapter.handle_message.call_args[0][0]
+        assert "# Title" in msg_event.text
+
+    @pytest.mark.asyncio
+    async def test_large_txt_not_injected(self, adapter):
+        """A .txt file over 100KB should be cached but NOT injected."""
+        content = b"x" * (200 * 1024)
+
+        with patch.object(adapter, "_download_slack_file_bytes", new_callable=AsyncMock) as dl:
+            dl.return_value = content
+            event = self._make_event(files=[{
+                "mimetype": "text/plain",
+                "name": "big.txt",
+                "url_private_download": "https://files.slack.com/big.txt",
+                "size": len(content),
+            }], text="")
+            await adapter._handle_slack_message(event)
+
+        msg_event = adapter.handle_message.call_args[0][0]
+        assert len(msg_event.media_urls) == 1
+        assert "[Content of" not in (msg_event.text or "")
+
+    @pytest.mark.asyncio
+    async def test_unsupported_file_type_skipped(self, adapter):
+        """A .zip file should be silently skipped."""
+        event = self._make_event(files=[{
+            "mimetype": "application/zip",
+            "name": "archive.zip",
+            "url_private_download": "https://files.slack.com/archive.zip",
+            "size": 1024,
+        }])
+        await adapter._handle_slack_message(event)
+
+        msg_event = adapter.handle_message.call_args[0][0]
+        assert msg_event.message_type == MessageType.TEXT
+        assert len(msg_event.media_urls) == 0
+
+    @pytest.mark.asyncio
+    async def test_oversized_document_skipped(self, adapter):
+        """A document over 20MB should be skipped."""
+        event = self._make_event(files=[{
+            "mimetype": "application/pdf",
+            "name": "huge.pdf",
+            "url_private_download": "https://files.slack.com/huge.pdf",
+            "size": 25 * 1024 * 1024,
+        }])
+        await adapter._handle_slack_message(event)
+
+        msg_event = adapter.handle_message.call_args[0][0]
+        assert len(msg_event.media_urls) == 0
+
+    @pytest.mark.asyncio
+    async def test_document_download_error_handled(self, adapter):
+        """If document download fails, handler should not crash."""
+        with patch.object(adapter, "_download_slack_file_bytes", new_callable=AsyncMock) as dl:
+            dl.side_effect = RuntimeError("download failed")
+            event = self._make_event(files=[{
+                "mimetype": "application/pdf",
+                "name": "report.pdf",
+                "url_private_download": "https://files.slack.com/report.pdf",
+                "size": 1024,
+            }])
+            await adapter._handle_slack_message(event)
+
+        # Handler should still be called (the exception is caught)
+        adapter.handle_message.assert_called_once()
+
+    @pytest.mark.asyncio
+    async def test_image_still_handled(self, adapter):
+        """Image attachments should still go through the image path, not document."""
+        with patch.object(adapter, "_download_slack_file", new_callable=AsyncMock) as dl:
+            dl.return_value = "/tmp/cached_image.jpg"
+            event = self._make_event(files=[{
+                "mimetype": "image/jpeg",
+                "name": "photo.jpg",
+                "url_private_download": "https://files.slack.com/photo.jpg",
+                "size": 1024,
+            }])
+            await adapter._handle_slack_message(event)
+
+        msg_event = adapter.handle_message.call_args[0][0]
+        assert msg_event.message_type == MessageType.PHOTO
+
+
+# ---------------------------------------------------------------------------
+# TestMessageRouting
+# ---------------------------------------------------------------------------
+
+class TestMessageRouting:
+    @pytest.mark.asyncio
+    async def test_dm_processed_without_mention(self, adapter):
+        """DM messages should be processed without requiring a bot mention."""
+        event = {
+            "text": "hello",
+            "user": "U_USER",
+            "channel": "D123",
+            "channel_type": "im",
+            "ts": "1234567890.000001",
+        }
+        await adapter._handle_slack_message(event)
+        adapter.handle_message.assert_called_once()
+
+    @pytest.mark.asyncio
+    async def test_channel_message_requires_mention(self, adapter):
+        """Channel messages without a bot mention should be ignored."""
+        event = {
+            "text": "just talking",
+            "user": "U_USER",
+            "channel": "C123",
+            "channel_type": "channel",
+            "ts": "1234567890.000001",
+        }
+        await adapter._handle_slack_message(event)
+        adapter.handle_message.assert_not_called()
+
+    @pytest.mark.asyncio
+    async def test_channel_mention_strips_bot_id(self, adapter):
+        """When mentioned in a channel, the bot mention should be stripped."""
+        event = {
+            "text": "<@U_BOT> what's the weather?",
+            "user": "U_USER",
+            "channel": "C123",
+            "channel_type": "channel",
+            "ts": "1234567890.000001",
+        }
+        await adapter._handle_slack_message(event)
+        msg_event = adapter.handle_message.call_args[0][0]
+        assert msg_event.text == "what's the weather?"
+        assert "<@U_BOT>" not in msg_event.text
+
+    @pytest.mark.asyncio
+    async def test_bot_messages_ignored(self, adapter):
+        """Messages from bots should be ignored."""
+        event = {
+            "text": "bot response",
+            "bot_id": "B_OTHER",
+            "channel": "C123",
+            "channel_type": "im",
+            "ts": "1234567890.000001",
+        }
+        await adapter._handle_slack_message(event)
+        adapter.handle_message.assert_not_called()
+
+    @pytest.mark.asyncio
+    async def test_message_edits_ignored(self, adapter):
+        """Message edits should be ignored."""
+        event = {
+            "text": "edited message",
+            "user": "U_USER",
+            "channel": "C123",
+            "channel_type": "im",
+            "ts": "1234567890.000001",
+            "subtype": "message_changed",
+        }
+        await adapter._handle_slack_message(event)
+        adapter.handle_message.assert_not_called()