diff --git a/plugins/platforms/simplex/__init__.py b/plugins/platforms/simplex/__init__.py
new file mode 100644
index 00000000000..d4f1d7bf0e3
--- /dev/null
+++ b/plugins/platforms/simplex/__init__.py
@@ -0,0 +1,3 @@
+from .adapter import register
+
+__all__ = ["register"]
diff --git a/plugins/platforms/simplex/adapter.py b/plugins/platforms/simplex/adapter.py
new file mode 100644
index 00000000000..b568f29bbb5
--- /dev/null
+++ b/plugins/platforms/simplex/adapter.py
@@ -0,0 +1,746 @@
+"""SimpleX Chat platform adapter (Hermes plugin).
+
+Connects to a simplex-chat daemon running in WebSocket mode.
+Inbound messages arrive via a persistent WebSocket connection.
+Outbound messages use the same WebSocket with JSON commands.
+
+This adapter ships as a Hermes platform plugin under
+``plugins/platforms/simplex/``. The Hermes plugin loader scans the
+directory at startup, calls ``register(ctx)``, and the platform
+becomes available to ``gateway/run.py`` and ``tools/send_message_tool``
+through the registry — no edits to core files are required.
+
+SimpleX chat daemon setup:
+    simplex-chat -p 5225          # start daemon on port 5225
+    # or via Docker:
+    # docker run -p 5225:5225 simplexchat/simplex-chat-cli -p 5225
+
+Required environment variables:
+    SIMPLEX_WS_URL             WebSocket URL of the daemon
+                               (default: ws://127.0.0.1:5225)
+
+Optional environment variables:
+    SIMPLEX_ALLOWED_USERS      Comma-separated contact IDs (allowlist)
+    SIMPLEX_ALLOW_ALL_USERS    Set 'true' to allow all contacts
+    SIMPLEX_HOME_CHANNEL       Default contact/group ID for cron delivery
+    SIMPLEX_HOME_CHANNEL_NAME  Human label for the home channel
+
+The ``websockets`` Python package is imported lazily — the plugin is
+discoverable and `hermes setup` can describe it even when websockets is
+not installed. ``check_requirements()`` returns False until the package
+is present, so the gateway will not attempt to instantiate the adapter.
+"""
+
+import asyncio
+import json
+import logging
+import os
+import random
+import time
+from datetime import datetime, timezone
+from typing import Any, Dict, List, Optional
+
+# Lazy import: BasePlatformAdapter and friends live in the main repo.
+# Imported at module top because they're stdlib-only inside Hermes — no
+# external dependency that would block the plugin from loading.
+from gateway.config import Platform, PlatformConfig
+from gateway.platforms.base import (
+    BasePlatformAdapter,
+    MessageEvent,
+    MessageType,
+    SendResult,
+    cache_image_from_bytes,
+    cache_audio_from_bytes,
+    cache_document_from_bytes,
+)
+
+logger = logging.getLogger(__name__)
+
+# ---------------------------------------------------------------------------
+# Constants
+# ---------------------------------------------------------------------------
+MAX_MESSAGE_LENGTH = 16_000  # SimpleX has no hard limit; keep chunking sane
+TYPING_INTERVAL = 10.0
+WS_RETRY_DELAY_INITIAL = 2.0
+WS_RETRY_DELAY_MAX = 60.0
+HEALTH_CHECK_INTERVAL = 30.0
+HEALTH_CHECK_STALE_THRESHOLD = 120.0
+
+# Correlation ID prefix for requests we send so we can ignore our own echoes.
+_CORR_PREFIX = "hermes-"
+
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+def _parse_comma_list(value: str) -> List[str]:
+    """Split a comma-separated string into a stripped list."""
+    return [v.strip() for v in value.split(",") if v.strip()]
+
+
+def _guess_extension(data: bytes) -> str:
+    """Guess file extension from magic bytes."""
+    if data[:4] == b"\x89PNG":
+        return ".png"
+    if data[:2] == b"\xff\xd8":
+        return ".jpg"
+    if data[:4] == b"GIF8":
+        return ".gif"
+    if len(data) >= 12 and data[:4] == b"RIFF" and data[8:12] == b"WEBP":
+        return ".webp"
+    if data[:4] == b"%PDF":
+        return ".pdf"
+    if len(data) >= 8 and data[4:8] == b"ftyp":
+        return ".mp4"
+    if data[:4] == b"OggS":
+        return ".ogg"
+    if len(data) >= 2 and data[0] == 0xFF and (data[1] & 0xE0) == 0xE0:
+        return ".mp3"
+    return ".bin"
+
+
+def _is_image_ext(ext: str) -> bool:
+    return ext.lower() in (".jpg", ".jpeg", ".png", ".gif", ".webp")
+
+
+def _is_audio_ext(ext: str) -> bool:
+    return ext.lower() in (".mp3", ".wav", ".ogg", ".m4a", ".aac")
+
+
+# ---------------------------------------------------------------------------
+# SimpleX Adapter
+# ---------------------------------------------------------------------------
+
+class SimplexAdapter(BasePlatformAdapter):
+    """SimpleX Chat adapter using the simplex-chat daemon WebSocket API.
+
+    Instantiated by the ``adapter_factory`` passed to
+    ``ctx.register_platform()`` in :func:`register`.
+    """
+
+    def __init__(self, config: PlatformConfig, **kwargs):
+        platform = Platform("simplex")
+        super().__init__(config=config, platform=platform)
+
+        extra = getattr(config, "extra", {}) or {}
+        self.ws_url = extra.get("ws_url", "ws://127.0.0.1:5225").rstrip("/")
+
+        # Running state
+        self._ws = None  # websockets connection
+        self._ws_task: Optional[asyncio.Task] = None
+        self._health_task: Optional[asyncio.Task] = None
+        self._typing_tasks: Dict[str, asyncio.Task] = {}
+        self._running = False
+        self._last_ws_activity = 0.0
+
+        # Track sent correlation IDs to filter echoes
+        self._pending_corr_ids: set = set()
+        self._max_pending_corr = 200
+
+        logger.info("SimpleX adapter initialized: url=%s", self.ws_url)
+
+    # ------------------------------------------------------------------
+    # Lifecycle
+    # ------------------------------------------------------------------
+
+    async def connect(self) -> bool:
+        """Connect to the simplex-chat daemon and start the WebSocket listener."""
+        try:
+            import websockets  # noqa: F401
+        except ImportError:
+            logger.error(
+                "SimpleX: 'websockets' package not installed. "
+                "Run: pip install websockets"
+            )
+            return False
+
+        if not self.ws_url:
+            logger.error("SimpleX: SIMPLEX_WS_URL is required")
+            return False
+
+        # Quick connectivity check — try to open and immediately close
+        try:
+            import websockets as _wsclient
+            async with _wsclient.connect(self.ws_url, open_timeout=10):
+                pass
+        except Exception as e:
+            logger.error("SimpleX: cannot reach daemon at %s: %s", self.ws_url, e)
+            return False
+
+        self._running = True
+        self._last_ws_activity = time.time()
+        self._ws_task = asyncio.create_task(self._ws_listener())
+        self._health_task = asyncio.create_task(self._health_monitor())
+
+        logger.info("SimpleX: connected to %s", self.ws_url)
+        return True
+
+    async def disconnect(self) -> None:
+        """Stop WebSocket listener and clean up."""
+        self._running = False
+
+        if self._ws_task:
+            self._ws_task.cancel()
+            try:
+                await self._ws_task
+            except asyncio.CancelledError:
+                pass
+
+        if self._health_task:
+            self._health_task.cancel()
+            try:
+                await self._health_task
+            except asyncio.CancelledError:
+                pass
+
+        for task in self._typing_tasks.values():
+            task.cancel()
+        self._typing_tasks.clear()
+
+        if self._ws:
+            try:
+                await self._ws.close()
+            except Exception:
+                pass
+            self._ws = None
+
+        logger.info("SimpleX: disconnected")
+
+    # ------------------------------------------------------------------
+    # WebSocket listener
+    # ------------------------------------------------------------------
+
+    async def _ws_listener(self) -> None:
+        """Maintain a persistent WebSocket connection to the daemon."""
+        import websockets as _wsclient
+        import websockets as _wsexc
+
+        backoff = WS_RETRY_DELAY_INITIAL
+
+        while self._running:
+            try:
+                logger.debug("SimpleX WS: connecting to %s", self.ws_url)
+                async with _wsclient.connect(
+                    self.ws_url,
+                    ping_interval=20,
+                    ping_timeout=20,
+                ) as ws:
+                    self._ws = ws
+                    backoff = WS_RETRY_DELAY_INITIAL
+                    self._last_ws_activity = time.time()
+                    logger.info("SimpleX WS: connected")
+
+                    async for raw in ws:
+                        if not self._running:
+                            break
+                        self._last_ws_activity = time.time()
+                        try:
+                            msg = json.loads(raw)
+                            await self._handle_event(msg)
+                        except json.JSONDecodeError:
+                            logger.debug("SimpleX WS: invalid JSON: %.100s", raw)
+                        except Exception:
+                            logger.exception("SimpleX WS: error handling event")
+
+            except asyncio.CancelledError:
+                break
+            except _wsexc.WebSocketException as e:
+                if self._running:
+                    logger.warning(
+                        "SimpleX WS: error: %s (reconnecting in %.0fs)", e, backoff
+                    )
+            except Exception as e:
+                if self._running:
+                    logger.warning(
+                        "SimpleX WS: unexpected error: %s (reconnecting in %.0fs)",
+                        e, backoff,
+                    )
+            finally:
+                self._ws = None
+
+            if self._running:
+                jitter = backoff * 0.2 * random.random()
+                await asyncio.sleep(backoff + jitter)
+                backoff = min(backoff * 2, WS_RETRY_DELAY_MAX)
+
+    # ------------------------------------------------------------------
+    # Health monitor
+    # ------------------------------------------------------------------
+
+    async def _health_monitor(self) -> None:
+        """Force reconnect if the WebSocket has been idle too long."""
+        while self._running:
+            await asyncio.sleep(HEALTH_CHECK_INTERVAL)
+            if not self._running:
+                break
+
+            elapsed = time.time() - self._last_ws_activity
+            if elapsed > HEALTH_CHECK_STALE_THRESHOLD:
+                logger.warning(
+                    "SimpleX: WS idle for %.0fs, forcing reconnect", elapsed
+                )
+                self._last_ws_activity = time.time()
+                if self._ws:
+                    try:
+                        await self._ws.close()
+                    except Exception:
+                        pass
+
+    # ------------------------------------------------------------------
+    # Inbound event handling
+    # ------------------------------------------------------------------
+
+    async def _handle_event(self, event: dict) -> None:
+        """Dispatch a daemon event to the appropriate handler."""
+        resp_type = event.get("type") or event.get("resp", {}).get("type", "")
+
+        # Filter responses to our own commands (echoes)
+        corr_id = event.get("corrId", "")
+        if corr_id and corr_id.startswith(_CORR_PREFIX):
+            self._pending_corr_ids.discard(corr_id)
+            return
+
+        if resp_type == "newChatItem":
+            await self._handle_new_chat_item(event)
+        elif resp_type == "newChatItems":
+            # Batch variant — process each item
+            items = event.get("chatItems") or []
+            for item_wrapper in items:
+                await self._handle_new_chat_item(item_wrapper)
+        # Ignore all other event types (delivery receipts, contact updates, etc.)
+
+    async def _handle_new_chat_item(self, wrapper: dict) -> None:
+        """Process a single newChatItem event into a MessageEvent."""
+        # The daemon wraps the chat item differently depending on version;
+        # normalise both layouts.
+        chat_info = wrapper.get("chatInfo") or wrapper.get("chat") or {}
+        chat_item = wrapper.get("chatItem") or wrapper.get("item") or {}
+
+        # Only process messages (not calls, deleted items, etc.)
+        item_content = chat_item.get("content") or {}
+        msg_content = item_content.get("msgContent") or {}
+        if not msg_content:
+            return
+
+        # Filter out messages sent by us (direction == "snd")
+        meta = chat_item.get("meta") or {}
+        direction = (meta.get("itemStatus") or {}).get("type", "")
+        if direction in ("sndSent", "sndSentDirect", "sndSentViaProxy", "sndNew"):
+            return
+
+        # Determine chat type and IDs
+        chat_type_raw = chat_info.get("type", "")
+        is_group = chat_type_raw in ("group", "groupInfo")
+
+        if is_group:
+            group_info = chat_info.get("groupInfo") or chat_info.get("group") or {}
+            group_id = str(group_info.get("groupId") or group_info.get("id") or "")
+            group_name = group_info.get("displayName") or group_info.get("groupProfile", {}).get("displayName", "")
+            chat_id = f"group:{group_id}" if group_id else ""
+            chat_name = group_name
+        else:
+            contact_info = chat_info.get("contact") or {}
+            contact_id = str(contact_info.get("contactId") or contact_info.get("id") or "")
+            contact_name = (
+                contact_info.get("displayName")
+                or contact_info.get("localDisplayName")
+                or contact_id
+            )
+            chat_id = contact_id
+            chat_name = contact_name
+
+        if not chat_id:
+            logger.debug("SimpleX: ignoring event with no chat_id")
+            return
+
+        # Sender — for groups the message includes a chatItemMember sub-object
+        member = chat_item.get("chatItemMember") or {}
+        if is_group and member:
+            sender_id = str(member.get("memberId") or member.get("id") or chat_id)
+            sender_name = (
+                member.get("displayName")
+                or member.get("localDisplayName")
+                or sender_id
+            )
+        else:
+            sender_id = chat_id
+            sender_name = chat_name
+
+        # Extract text
+        text = msg_content.get("text") or ""
+
+        # Media attachments
+        media_urls: List[str] = []
+        media_types: List[str] = []
+        file_info = chat_item.get("file") or {}
+        if file_info and file_info.get("fileStatus") not in ("cancelled", "error"):
+            file_id = file_info.get("fileId")
+            file_name = file_info.get("fileName", "file")
+            if file_id:
+                try:
+                    cached = await self._fetch_file(file_id, file_name)
+                    if cached:
+                        ext = cached.rsplit(".", 1)[-1]
+                        if _is_image_ext("." + ext):
+                            media_types.append("image/" + ext.replace("jpg", "jpeg"))
+                        elif _is_audio_ext("." + ext):
+                            media_types.append("audio/" + ext)
+                        else:
+                            media_types.append("application/octet-stream")
+                        media_urls.append(cached)
+                except Exception:
+                    logger.exception("SimpleX: failed to fetch file %s", file_id)
+
+        # Timestamp
+        ts_str = meta.get("itemTs") or meta.get("createdAt") or ""
+        try:
+            timestamp = datetime.fromisoformat(ts_str.replace("Z", "+00:00"))
+        except (ValueError, AttributeError):
+            timestamp = datetime.now(tz=timezone.utc)
+
+        # Build source
+        source = self.build_source(
+            chat_id=chat_id,
+            chat_name=chat_name,
+            chat_type="group" if is_group else "dm",
+            user_id=sender_id,
+            user_name=sender_name,
+        )
+
+        # Message type
+        msg_type = MessageType.TEXT
+        if media_types:
+            if any(mt.startswith("audio/") for mt in media_types):
+                msg_type = MessageType.VOICE
+            elif any(mt.startswith("image/") for mt in media_types):
+                msg_type = MessageType.PHOTO
+
+        event_obj = MessageEvent(
+            source=source,
+            text=text,
+            message_type=msg_type,
+            media_urls=media_urls,
+            media_types=media_types,
+            timestamp=timestamp,
+            raw_message=wrapper,
+        )
+
+        await self.handle_message(event_obj)
+
+    async def _fetch_file(self, file_id: Any, file_name: str) -> Optional[str]:
+        """Ask the daemon to receive and return a file attachment."""
+        # simplex-chat exposes `/api/v1/files/{fileId}` on an HTTP port
+        # when started with --http-port. However, the canonical WebSocket API
+        # does not have a direct binary download command; files are stored on
+        # the local filesystem after the daemon accepts them.
+        #
+        # We request acceptance first, then read from the daemon's local path.
+        corr_id = self._make_corr_id()
+        cmd = {
+            "corrId": corr_id,
+            "cmd": f"/freceive {file_id}",
+        }
+        await self._send_ws(cmd)
+        # The daemon will emit a chatItemUpdated event when the file lands;
+        # for simplicity we just wait briefly and rely on the daemon's default path.
+        await asyncio.sleep(2)
+
+        # simplex-chat stores received files in ~/Downloads or a configured path.
+        # We try common locations.
+        for search_dir in (
+            os.path.expanduser("~/Downloads"),
+            os.path.expanduser("~/.simplex/files"),
+            "/tmp/simplex_files",
+        ):
+            candidate = os.path.join(search_dir, file_name)
+            if os.path.exists(candidate):
+                with open(candidate, "rb") as f:
+                    data = f.read()
+                ext = _guess_extension(data)
+                if _is_image_ext(ext):
+                    return cache_image_from_bytes(data, ext)
+                elif _is_audio_ext(ext):
+                    return cache_audio_from_bytes(data, ext)
+                else:
+                    return cache_document_from_bytes(data, file_name)
+        return None
+
+    # ------------------------------------------------------------------
+    # Outbound messages
+    # ------------------------------------------------------------------
+
+    def _make_corr_id(self) -> str:
+        """Generate a unique correlation ID for a request."""
+        corr_id = f"{_CORR_PREFIX}{int(time.time() * 1000)}-{random.randint(0, 9999)}"
+        self._pending_corr_ids.add(corr_id)
+        if len(self._pending_corr_ids) > self._max_pending_corr:
+            # Trim oldest — sets are unordered so just clear the oldest half
+            to_remove = list(self._pending_corr_ids)[:self._max_pending_corr // 2]
+            self._pending_corr_ids -= set(to_remove)
+        return corr_id
+
+    async def _send_ws(self, payload: dict) -> None:
+        """Send a JSON payload over the WebSocket, queuing if not yet connected."""
+        import websockets as _wsexc
+        ws = self._ws
+        if not ws:
+            logger.debug("SimpleX: WS not connected, dropping outbound command")
+            return
+        try:
+            await ws.send(json.dumps(payload))
+        except _wsexc.ConnectionClosed:
+            logger.warning("SimpleX: WS closed while sending")
+        except Exception as e:
+            logger.warning("SimpleX: WS send error: %s", e)
+
+    async def send(
+        self,
+        chat_id: str,
+        content: str,
+        reply_to: Optional[str] = None,
+        metadata: Optional[Dict[str, Any]] = None,
+    ) -> SendResult:
+        """Send a text message to a contact or group."""
+        corr_id = self._make_corr_id()
+
+        if chat_id.startswith("group:"):
+            group_id = chat_id[6:]
+            cmd_str = f"#[{group_id}] {content}"
+        else:
+            cmd_str = f"@[{chat_id}] {content}"
+
+        payload = {
+            "corrId": corr_id,
+            "cmd": cmd_str,
+        }
+
+        await self._send_ws(payload)
+        return SendResult(success=True)
+
+    async def send_typing(self, chat_id: str, metadata=None) -> None:
+        """SimpleX does not expose a typing indicator API — no-op."""
+        pass
+
+    async def send_image(
+        self,
+        chat_id: str,
+        image_url: str,
+        caption: Optional[str] = None,
+        reply_to: Optional[str] = None,
+        metadata: Optional[Dict[str, Any]] = None,
+    ) -> SendResult:
+        """Send an image (URL) as a message with optional caption.
+
+        SimpleX has no native ``send_image`` over the WebSocket API — file
+        attachments require the daemon's filesystem-backed flow which is
+        not driven from this adapter. Fall back to a plain text message
+        containing the URL and caption.
+        """
+        text = f"{caption}\n{image_url}".strip() if caption else image_url
+        return await self.send(chat_id, text, reply_to=reply_to, metadata=metadata)
+
+    async def get_chat_info(self, chat_id: str) -> dict:
+        """Return basic chat info."""
+        if chat_id.startswith("group:"):
+            return {"chat_id": chat_id, "type": "group", "name": chat_id[6:]}
+        return {"chat_id": chat_id, "type": "dm", "name": chat_id}
+
+
+# ---------------------------------------------------------------------------
+# Plugin entry-point hooks
+# ---------------------------------------------------------------------------
+
+def check_requirements() -> bool:
+    """Plugin gate: require SIMPLEX_WS_URL AND the websockets package.
+
+    Returning False keeps the platform out of ``get_connected_platforms()``
+    so the gateway never instantiates the adapter when the dependency is
+    missing or no daemon URL is configured.
+    """
+    if not os.getenv("SIMPLEX_WS_URL"):
+        return False
+    try:
+        import websockets  # noqa: F401
+    except ImportError:
+        return False
+    return True
+
+
+def validate_config(config) -> bool:
+    """Validate that the platform config has enough info to connect."""
+    extra = getattr(config, "extra", {}) or {}
+    ws_url = os.getenv("SIMPLEX_WS_URL") or extra.get("ws_url", "")
+    return bool(ws_url)
+
+
+def is_connected(config) -> bool:
+    """Check whether SimpleX is configured (env or config.yaml)."""
+    extra = getattr(config, "extra", {}) or {}
+    ws_url = os.getenv("SIMPLEX_WS_URL") or extra.get("ws_url", "")
+    return bool(ws_url)
+
+
+def _env_enablement() -> dict | None:
+    """Seed ``PlatformConfig.extra`` from env vars during gateway config load.
+
+    Called by the platform registry's env-enablement hook BEFORE adapter
+    construction, so ``gateway status`` and ``get_connected_platforms()``
+    reflect env-only configuration without instantiating the WebSocket
+    client. Returns ``None`` when SimpleX isn't minimally configured.
+
+    The special ``home_channel`` key in the returned dict is handled by
+    the core hook — it becomes a proper ``HomeChannel`` dataclass on the
+    ``PlatformConfig`` rather than being merged into ``extra``.
+    """
+    ws_url = os.getenv("SIMPLEX_WS_URL", "").strip()
+    if not ws_url:
+        return None
+    seed: dict = {"ws_url": ws_url}
+    home = os.getenv("SIMPLEX_HOME_CHANNEL", "").strip()
+    if home:
+        seed["home_channel"] = {
+            "chat_id": home,
+            "name": os.getenv("SIMPLEX_HOME_CHANNEL_NAME", "").strip() or home,
+        }
+    return seed
+
+
+async def _standalone_send(
+    pconfig,
+    chat_id: str,
+    message: str,
+    *,
+    thread_id: Optional[str] = None,
+    media_files: Optional[List[str]] = None,
+    force_document: bool = False,
+) -> Dict[str, Any]:
+    """Open an ephemeral WebSocket to the daemon, send, and close.
+
+    Used by ``tools/send_message_tool._send_via_adapter`` when the gateway
+    runner is not in this process (e.g. ``hermes cron`` running as a
+    separate process from ``hermes gateway``). Without this hook,
+    ``deliver=simplex`` cron jobs fail with "No live adapter for platform".
+
+    ``thread_id`` and ``force_document`` are accepted for signature parity
+    with other plugins but are not meaningful here. ``media_files`` is
+    accepted but only the text body is delivered — SimpleX requires the
+    daemon's filesystem-backed file flow which an ephemeral connection
+    cannot drive safely.
+    """
+    try:
+        import websockets as _wsclient
+    except ImportError:
+        return {"error": "websockets not installed. Run: pip install websockets"}
+
+    extra = getattr(pconfig, "extra", {}) or {}
+    ws_url = os.getenv("SIMPLEX_WS_URL") or extra.get("ws_url", "ws://127.0.0.1:5225")
+    if not ws_url:
+        return {"error": "SimpleX standalone send: SIMPLEX_WS_URL is required"}
+
+    try:
+        if chat_id.startswith("group:"):
+            group_id = chat_id[6:]
+            cmd_str = f"#[{group_id}] {message}"
+        else:
+            cmd_str = f"@[{chat_id}] {message}"
+
+        payload = {
+            "corrId": f"hermes-snd-{int(time.time() * 1000)}",
+            "cmd": cmd_str,
+        }
+
+        async with _wsclient.connect(ws_url, open_timeout=10, close_timeout=5) as ws:
+            await ws.send(json.dumps(payload))
+            # Give the daemon a moment to process the command before closing.
+            await asyncio.sleep(0.5)
+
+        return {"success": True, "platform": "simplex", "chat_id": chat_id}
+    except Exception as e:
+        return {"error": f"SimpleX send failed: {e}"}
+
+
+def interactive_setup() -> None:
+    """Minimal stdin wizard for ``hermes setup gateway`` → SimpleX.
+
+    Prompts for the WebSocket URL and the optional allowlist / home channel.
+    Writes to ``~/.hermes/.env`` via ``hermes_cli.config``.
+    """
+    print()
+    print("SimpleX Chat setup")
+    print("------------------")
+    print("Requirements:")
+    print("  1. simplex-chat daemon running (e.g. `simplex-chat -p 5225`).")
+    print("  2. Python package `websockets` installed (`pip install websockets`).")
+    print()
+
+    try:
+        from hermes_cli.config import get_env_value, save_env_value
+    except ImportError:
+        print("hermes_cli.config not available; set SIMPLEX_* vars manually in ~/.hermes/.env")
+        return
+
+    def _prompt(var: str, prompt: str, *, secret: bool = False) -> None:
+        existing = get_env_value(var) if callable(get_env_value) else None
+        suffix = " [keep current]" if existing else ""
+        try:
+            if secret:
+                import getpass
+                value = getpass.getpass(f"{prompt}{suffix}: ")
+            else:
+                value = input(f"{prompt}{suffix}: ").strip()
+        except (EOFError, KeyboardInterrupt):
+            print()
+            return
+        if value:
+            save_env_value(var, value)
+
+    _prompt("SIMPLEX_WS_URL", "Daemon WebSocket URL (default ws://127.0.0.1:5225)")
+    _prompt("SIMPLEX_ALLOWED_USERS", "Allowed contact IDs (comma-separated; blank=skip)")
+    _prompt("SIMPLEX_HOME_CHANNEL", "Home channel contact/group ID (or empty)")
+    print("Done. Make sure the simplex-chat daemon is running before starting the gateway.")
+
+
+def register(ctx) -> None:
+    """Plugin entry point — called by the Hermes plugin system at startup."""
+    ctx.register_platform(
+        name="simplex",
+        label="SimpleX Chat",
+        adapter_factory=lambda cfg: SimplexAdapter(cfg),
+        check_fn=check_requirements,
+        validate_config=validate_config,
+        is_connected=is_connected,
+        required_env=["SIMPLEX_WS_URL"],
+        install_hint="pip install websockets   # SimpleX adapter requires the websockets package",
+        setup_fn=interactive_setup,
+        # Env-driven auto-configuration: seeds PlatformConfig.extra so
+        # env-only setups show up in `hermes gateway status` without
+        # instantiating the adapter.
+        env_enablement_fn=_env_enablement,
+        # Cron home-channel delivery support — `deliver=simplex` cron jobs
+        # route to SIMPLEX_HOME_CHANNEL when set.
+        cron_deliver_env_var="SIMPLEX_HOME_CHANNEL",
+        # Out-of-process cron delivery. Without this hook, deliver=simplex
+        # cron jobs fail with "No live adapter" when cron runs separately
+        # from the gateway.
+        standalone_sender_fn=_standalone_send,
+        # Auth env vars for _is_user_authorized() integration
+        allowed_users_env="SIMPLEX_ALLOWED_USERS",
+        allow_all_env="SIMPLEX_ALLOW_ALL_USERS",
+        # SimpleX has no hard line length; we still chunk for sanity.
+        max_message_length=MAX_MESSAGE_LENGTH,
+        # Display
+        emoji="🔒",
+        # SimpleX uses opaque contact IDs only — no phone numbers or
+        # email addresses to redact.
+        pii_safe=True,
+        allow_update_command=True,
+        # LLM guidance
+        platform_hint=(
+            "You are chatting via SimpleX Chat, a private decentralised "
+            "messenger. Contacts are identified by opaque internal IDs, "
+            "not phone numbers or usernames. SimpleX supports standard "
+            "markdown formatting. There is no typing indicator and no "
+            "hard message length limit, but keep responses conversational."
+        ),
+    )
diff --git a/plugins/platforms/simplex/plugin.yaml b/plugins/platforms/simplex/plugin.yaml
new file mode 100644
index 00000000000..2bb87641b63
--- /dev/null
+++ b/plugins/platforms/simplex/plugin.yaml
@@ -0,0 +1,37 @@
+name: simplex-platform
+label: SimpleX Chat
+kind: platform
+version: 1.0.0
+description: >
+  SimpleX Chat gateway adapter for Hermes Agent.
+  Connects to a local simplex-chat daemon via WebSocket and relays
+  messages between SimpleX contacts/groups and the Hermes agent.
+  SimpleX is decentralised and assigns no persistent user IDs —
+  every contact is an opaque internal ID generated at connection
+  time, making it one of the most private messengers available.
+author: Mibayy
+# ``requires_env`` and ``optional_env`` entries are surfaced in the
+# ``hermes config`` UI via the platform-plugin env var injector in
+# ``hermes_cli/config.py``.
+requires_env:
+  - name: SIMPLEX_WS_URL
+    description: "WebSocket URL of the simplex-chat daemon (e.g. ws://127.0.0.1:5225)"
+    prompt: "SimpleX daemon WebSocket URL"
+    password: false
+optional_env:
+  - name: SIMPLEX_ALLOWED_USERS
+    description: "Comma-separated SimpleX contact IDs allowed to talk to the bot"
+    prompt: "Allowed contact IDs (comma-separated)"
+    password: false
+  - name: SIMPLEX_ALLOW_ALL_USERS
+    description: "Allow any contact to talk to the bot (dev only — disables allowlist)"
+    prompt: "Allow all contacts? (true/false)"
+    password: false
+  - name: SIMPLEX_HOME_CHANNEL
+    description: "Default contact/group ID for cron / notification delivery"
+    prompt: "Home channel contact/group ID (or empty)"
+    password: false
+  - name: SIMPLEX_HOME_CHANNEL_NAME
+    description: "Human label for the home channel (defaults to the ID)"
+    prompt: "Home channel display name (or empty)"
+    password: false
diff --git a/tests/gateway/test_simplex_plugin.py b/tests/gateway/test_simplex_plugin.py
new file mode 100644
index 00000000000..0b1b1b21a85
--- /dev/null
+++ b/tests/gateway/test_simplex_plugin.py
@@ -0,0 +1,347 @@
+"""Tests for the SimpleX Chat platform-plugin adapter.
+
+Loaded via the ``_plugin_adapter_loader`` helper so this lives under
+``plugin_adapter_simplex`` in ``sys.modules`` and cannot collide with
+sibling platform-plugin tests on the same xdist worker.
+"""
+
+from __future__ import annotations
+
+import json
+import os
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+
+from tests.gateway._plugin_adapter_loader import load_plugin_adapter
+
+_simplex = load_plugin_adapter("simplex")
+
+SimplexAdapter = _simplex.SimplexAdapter
+check_requirements = _simplex.check_requirements
+validate_config = _simplex.validate_config
+is_connected = _simplex.is_connected
+register = _simplex.register
+_env_enablement = _simplex._env_enablement
+_standalone_send = _simplex._standalone_send
+_guess_extension = _simplex._guess_extension
+_is_image_ext = _simplex._is_image_ext
+_is_audio_ext = _simplex._is_audio_ext
+_CORR_PREFIX = _simplex._CORR_PREFIX
+
+
+# ---------------------------------------------------------------------------
+# 1. Platform enum (plugin-discovered, not bundled)
+# ---------------------------------------------------------------------------
+
+def test_platform_enum_resolves_via_plugin_scan():
+    """The plugin filesystem scan should expose Platform("simplex")."""
+    from gateway.config import Platform
+    p = Platform("simplex")
+    assert p.value == "simplex"
+    # Identity stability — repeated lookups return the same pseudo-member
+    assert Platform("simplex") is p
+
+
+# ---------------------------------------------------------------------------
+# 2. check_requirements / validate_config / is_connected
+# ---------------------------------------------------------------------------
+
+def test_check_requirements_needs_url(monkeypatch):
+    monkeypatch.delenv("SIMPLEX_WS_URL", raising=False)
+    assert check_requirements() is False
+
+
+def test_check_requirements_true_when_configured(monkeypatch):
+    monkeypatch.setenv("SIMPLEX_WS_URL", "ws://127.0.0.1:5225")
+    # websockets is a dev dep in this repo via the test plugins; the
+    # check_requirements() gate also asserts the package imports.
+    websockets_present = True
+    try:
+        import websockets  # noqa: F401
+    except ImportError:
+        websockets_present = False
+    assert check_requirements() is websockets_present
+
+
+def test_validate_config_uses_env_or_extra():
+    from gateway.config import PlatformConfig
+    # Empty extra + no env → invalid
+    cfg = PlatformConfig(enabled=True)
+    assert validate_config(cfg) is False
+    # extra-only path → valid
+    cfg2 = PlatformConfig(enabled=True, extra={"ws_url": "ws://localhost:5225"})
+    assert validate_config(cfg2) is True
+
+
+def test_is_connected_mirrors_validate(monkeypatch):
+    from gateway.config import PlatformConfig
+    monkeypatch.delenv("SIMPLEX_WS_URL", raising=False)
+    cfg = PlatformConfig(enabled=True, extra={"ws_url": "ws://x"})
+    assert is_connected(cfg) is True
+    assert is_connected(PlatformConfig(enabled=True)) is False
+
+
+# ---------------------------------------------------------------------------
+# 3. _env_enablement seeds PlatformConfig.extra
+# ---------------------------------------------------------------------------
+
+def test_env_enablement_none_when_unset(monkeypatch):
+    monkeypatch.delenv("SIMPLEX_WS_URL", raising=False)
+    assert _env_enablement() is None
+
+
+def test_env_enablement_seeds_ws_url(monkeypatch):
+    monkeypatch.setenv("SIMPLEX_WS_URL", "ws://127.0.0.1:5225")
+    monkeypatch.delenv("SIMPLEX_HOME_CHANNEL", raising=False)
+    seed = _env_enablement()
+    assert seed == {"ws_url": "ws://127.0.0.1:5225"}
+
+
+def test_env_enablement_seeds_home_channel(monkeypatch):
+    monkeypatch.setenv("SIMPLEX_WS_URL", "ws://127.0.0.1:5225")
+    monkeypatch.setenv("SIMPLEX_HOME_CHANNEL", "42")
+    monkeypatch.setenv("SIMPLEX_HOME_CHANNEL_NAME", "Personal")
+    seed = _env_enablement()
+    assert seed["home_channel"] == {"chat_id": "42", "name": "Personal"}
+
+
+def test_env_enablement_home_channel_defaults_name_to_id(monkeypatch):
+    monkeypatch.setenv("SIMPLEX_WS_URL", "ws://127.0.0.1:5225")
+    monkeypatch.setenv("SIMPLEX_HOME_CHANNEL", "42")
+    monkeypatch.delenv("SIMPLEX_HOME_CHANNEL_NAME", raising=False)
+    seed = _env_enablement()
+    assert seed["home_channel"] == {"chat_id": "42", "name": "42"}
+
+
+# ---------------------------------------------------------------------------
+# 4. Adapter init
+# ---------------------------------------------------------------------------
+
+def test_adapter_init_custom_url():
+    from gateway.config import PlatformConfig
+    cfg = PlatformConfig(enabled=True, extra={"ws_url": "ws://localhost:5225"})
+    adapter = SimplexAdapter(cfg)
+    assert adapter.ws_url == "ws://localhost:5225"
+    assert adapter._running is False
+    assert adapter._ws is None
+
+
+def test_adapter_init_default_url():
+    from gateway.config import PlatformConfig
+    cfg = PlatformConfig(enabled=True)
+    adapter = SimplexAdapter(cfg)
+    assert adapter.ws_url == "ws://127.0.0.1:5225"
+
+
+def test_adapter_platform_identity():
+    """Adapter should expose Platform("simplex") identity."""
+    from gateway.config import Platform, PlatformConfig
+    cfg = PlatformConfig(enabled=True)
+    adapter = SimplexAdapter(cfg)
+    assert adapter.platform is Platform("simplex")
+
+
+# ---------------------------------------------------------------------------
+# 5. Helper functions (magic-byte detection)
+# ---------------------------------------------------------------------------
+
+def test_guess_extension_png():
+    assert _guess_extension(b"\x89PNG\r\n\x1a\n") == ".png"
+
+
+def test_guess_extension_jpg():
+    assert _guess_extension(b"\xff\xd8\xff\xe0") == ".jpg"
+
+
+def test_guess_extension_ogg():
+    assert _guess_extension(b"OggS\x00\x02") == ".ogg"
+
+
+def test_guess_extension_unknown():
+    assert _guess_extension(b"\x00\x01\x02\x03") == ".bin"
+
+
+def test_is_image_ext():
+    assert _is_image_ext(".png") is True
+    assert _is_image_ext(".webp") is True
+    assert _is_image_ext(".ogg") is False
+
+
+def test_is_audio_ext():
+    assert _is_audio_ext(".ogg") is True
+    assert _is_audio_ext(".mp3") is True
+    assert _is_audio_ext(".pdf") is False
+
+
+# ---------------------------------------------------------------------------
+# 6. Correlation IDs
+# ---------------------------------------------------------------------------
+
+def test_corr_id_starts_with_prefix_and_tracks_pending():
+    from gateway.config import PlatformConfig
+    cfg = PlatformConfig(enabled=True, extra={"ws_url": "ws://localhost:5225"})
+    adapter = SimplexAdapter(cfg)
+    corr_id = adapter._make_corr_id()
+    assert corr_id.startswith(_CORR_PREFIX)
+    assert corr_id in adapter._pending_corr_ids
+
+
+def test_corr_id_pending_set_self_trims():
+    from gateway.config import PlatformConfig
+    cfg = PlatformConfig(enabled=True, extra={"ws_url": "ws://localhost:5225"})
+    adapter = SimplexAdapter(cfg)
+    adapter._max_pending_corr = 4
+    for _ in range(10):
+        adapter._make_corr_id()
+    # After many additions, the pending set should be bounded by the trim
+    # logic — at most one trim window above the cap.
+    assert len(adapter._pending_corr_ids) <= adapter._max_pending_corr + 1
+
+
+# ---------------------------------------------------------------------------
+# 7. Outbound send (mocked WS)
+# ---------------------------------------------------------------------------
+
+@pytest.mark.asyncio
+async def test_send_dm():
+    from gateway.config import PlatformConfig
+    cfg = PlatformConfig(enabled=True, extra={"ws_url": "ws://localhost:5225"})
+    adapter = SimplexAdapter(cfg)
+
+    mock_ws = AsyncMock()
+    adapter._ws = mock_ws
+
+    result = await adapter.send("contact-42", "Hello, SimpleX!")
+    mock_ws.send.assert_called_once()
+    payload = json.loads(mock_ws.send.call_args[0][0])
+    assert payload["cmd"] == "@[contact-42] Hello, SimpleX!"
+    assert payload["corrId"].startswith(_CORR_PREFIX)
+    assert result.success is True
+
+
+@pytest.mark.asyncio
+async def test_send_group():
+    from gateway.config import PlatformConfig
+    cfg = PlatformConfig(enabled=True, extra={"ws_url": "ws://localhost:5225"})
+    adapter = SimplexAdapter(cfg)
+
+    mock_ws = AsyncMock()
+    adapter._ws = mock_ws
+
+    result = await adapter.send("group:grp-99", "Hello, group!")
+    payload = json.loads(mock_ws.send.call_args[0][0])
+    assert payload["cmd"] == "#[grp-99] Hello, group!"
+    assert result.success is True
+
+
+@pytest.mark.asyncio
+async def test_send_when_ws_not_connected_does_not_crash():
+    from gateway.config import PlatformConfig
+    cfg = PlatformConfig(enabled=True, extra={"ws_url": "ws://localhost:5225"})
+    adapter = SimplexAdapter(cfg)
+    # No _ws assigned — _send_ws should drop quietly
+    result = await adapter.send("contact-42", "hi")
+    assert result.success is True  # send() always returns success — fire-and-forget
+
+
+# ---------------------------------------------------------------------------
+# 8. Inbound: filter own-echo by corrId prefix
+# ---------------------------------------------------------------------------
+
+@pytest.mark.asyncio
+async def test_handle_event_filters_own_corr_id():
+    from gateway.config import PlatformConfig
+    cfg = PlatformConfig(enabled=True, extra={"ws_url": "ws://localhost:5225"})
+    adapter = SimplexAdapter(cfg)
+    # Pretend we sent a command with this corrId
+    own = adapter._make_corr_id()
+    handler_mock = AsyncMock()
+    adapter._handle_new_chat_item = handler_mock  # type: ignore
+
+    await adapter._handle_event({"corrId": own, "type": "newChatItem"})
+    handler_mock.assert_not_called()
+    assert own not in adapter._pending_corr_ids  # discarded
+
+
+# ---------------------------------------------------------------------------
+# 9. Standalone (out-of-process) send for cron
+# ---------------------------------------------------------------------------
+
+@pytest.mark.asyncio
+async def test_standalone_send_missing_websockets(monkeypatch):
+    """When websockets is unimportable, return a clean error dict.
+
+    Implementation detail: the standalone path does ``import websockets``
+    inside the function body. We simulate the package being absent by
+    pulling it out of ``sys.modules`` and pointing the finder at None.
+    """
+    import sys
+    saved_websockets = sys.modules.pop("websockets", None)
+    saved_meta = list(sys.meta_path)
+
+    class _Blocker:
+        @staticmethod
+        def find_spec(name, path=None, target=None):
+            if name == "websockets" or name.startswith("websockets."):
+                raise ImportError("websockets blocked for test")
+            return None
+
+    sys.meta_path.insert(0, _Blocker())
+    try:
+        pconfig = MagicMock()
+        pconfig.extra = {"ws_url": "ws://localhost:5225"}
+        result = await _standalone_send(pconfig, "contact-42", "hi")
+        assert isinstance(result, dict)
+        assert "error" in result
+        assert "websockets" in result["error"]
+    finally:
+        sys.meta_path[:] = saved_meta
+        if saved_websockets is not None:
+            sys.modules["websockets"] = saved_websockets
+
+
+@pytest.mark.asyncio
+async def test_standalone_send_missing_url(monkeypatch):
+    monkeypatch.delenv("SIMPLEX_WS_URL", raising=False)
+    pconfig = MagicMock()
+    pconfig.extra = {}
+    # We expect the URL fallback (extra+env both empty) to be empty string,
+    # producing an error. We also need websockets to be importable for the
+    # url-check branch to be reached, so skip when it's not.
+    try:
+        import websockets.client  # noqa: F401
+    except ImportError:
+        pytest.skip("websockets not installed")
+
+    result = await _standalone_send(pconfig, "contact-42", "hi")
+    assert isinstance(result, dict)
+    # Either error about URL or a connection attempt failure — both are valid
+    # signals that the standalone path requires configuration.
+    assert "error" in result
+
+
+# ---------------------------------------------------------------------------
+# 10. register() — plugin-side metadata
+# ---------------------------------------------------------------------------
+
+def test_register_calls_register_platform():
+    ctx = MagicMock()
+    register(ctx)
+    ctx.register_platform.assert_called_once()
+    kwargs = ctx.register_platform.call_args.kwargs
+    assert kwargs["name"] == "simplex"
+    assert kwargs["label"] == "SimpleX Chat"
+    assert kwargs["required_env"] == ["SIMPLEX_WS_URL"]
+    assert kwargs["allowed_users_env"] == "SIMPLEX_ALLOWED_USERS"
+    assert kwargs["allow_all_env"] == "SIMPLEX_ALLOW_ALL_USERS"
+    assert kwargs["cron_deliver_env_var"] == "SIMPLEX_HOME_CHANNEL"
+    assert callable(kwargs["check_fn"])
+    assert callable(kwargs["validate_config"])
+    assert callable(kwargs["is_connected"])
+    assert callable(kwargs["env_enablement_fn"])
+    assert callable(kwargs["standalone_sender_fn"])
+    assert callable(kwargs["adapter_factory"])
+    assert callable(kwargs["setup_fn"])
+    # SimpleX uses opaque IDs only — no PII to redact.
+    assert kwargs["pii_safe"] is True
diff --git a/website/docs/user-guide/messaging/simplex.md b/website/docs/user-guide/messaging/simplex.md
new file mode 100644
index 00000000000..60853acd9f8
--- /dev/null
+++ b/website/docs/user-guide/messaging/simplex.md
@@ -0,0 +1,99 @@
+# SimpleX Chat
+
+[SimpleX Chat](https://simplex.chat/) is a private, decentralised messaging platform where users own their contacts and groups. Unlike other platforms, SimpleX assigns no persistent user IDs — every contact is identified by an opaque internal ID generated at connection time, which makes it one of the most private messengers available.
+
+## Prerequisites
+
+- The **simplex-chat** CLI installed and running as a daemon
+- Python package **websockets** (`pip install websockets`)
+
+## Install simplex-chat
+
+Download the latest release from the [simplex-chat GitHub releases](https://github.com/simplex-chat/simplex-chat/releases) page, or via Docker:
+
+```bash
+# Linux / macOS binary
+curl -L https://github.com/simplex-chat/simplex-chat/releases/latest/download/simplex-chat-ubuntu-22_04-x86-64 -o simplex-chat
+chmod +x simplex-chat
+
+# Or Docker
+docker run -p 5225:5225 simplexchat/simplex-chat -p 5225
+```
+
+## Start the daemon
+
+```bash
+simplex-chat -p 5225
+```
+
+The daemon listens on WebSocket at `ws://127.0.0.1:5225` by default.
+
+## Configure Hermes
+
+### Via setup wizard
+
+```bash
+hermes setup gateway
+```
+
+Select **SimpleX Chat** and follow the prompts.
+
+### Via environment variables
+
+Add these to `~/.hermes/.env`:
+
+```
+SIMPLEX_WS_URL=ws://127.0.0.1:5225
+SIMPLEX_ALLOWED_USERS=<contact-id-1>,<contact-id-2>
+SIMPLEX_HOME_CHANNEL=<contact-id>
+```
+
+| Variable | Required | Description |
+|---|---|---|
+| `SIMPLEX_WS_URL` | Yes | WebSocket URL of the simplex-chat daemon |
+| `SIMPLEX_ALLOWED_USERS` | Recommended | Comma-separated contact IDs allowed to use the agent |
+| `SIMPLEX_ALLOW_ALL_USERS` | Optional | Set `true` to allow every contact (use carefully) |
+| `SIMPLEX_HOME_CHANNEL` | Optional | Default contact ID for cron job delivery |
+| `SIMPLEX_HOME_CHANNEL_NAME` | Optional | Human label for the home channel |
+
+## Find your contact ID
+
+After starting the daemon, open a conversation with your agent contact. The contact ID will appear in session logs or via `hermes send_message action=list`.
+
+## Authorization
+
+By default **all contacts are denied**. You must either:
+
+1. Set `SIMPLEX_ALLOWED_USERS` to a comma-separated list of contact IDs, or
+2. Use **DM pairing** — send any message to the bot and it will reply with a pairing code. Enter that code via `hermes gateway pair`.
+
+## Using SimpleX with cron jobs
+
+```python
+cronjob(
+    action="create",
+    schedule="every 1h",
+    deliver="simplex",          # uses SIMPLEX_HOME_CHANNEL
+    prompt="Check for alerts and summarise."
+)
+```
+
+Or target a specific contact:
+
+```python
+send_message(target="simplex:<contact-id>", message="Done!")
+```
+
+## Privacy notes
+
+- SimpleX never reveals phone numbers or email addresses — contacts use opaque IDs
+- The connection between Hermes and the daemon is local WebSocket (`ws://127.0.0.1:5225`) — no data leaves your machine
+- Messages are end-to-end encrypted by the SimpleX protocol before reaching the daemon
+
+## Troubleshooting
+
+**"Cannot reach daemon"** — Ensure `simplex-chat -p 5225` is running and the port matches `SIMPLEX_WS_URL`.
+
+**"websockets not installed"** — Run `pip install websockets`.
+
+**Messages not received** — Check that the contact's ID is in `SIMPLEX_ALLOWED_USERS` or approve them via DM pairing.