diff --git a/cli.py b/cli.py
index 20996aecc..3a3e8108f 100644
--- a/cli.py
+++ b/cli.py
@@ -5484,7 +5484,8 @@ class HermesCLI:
                         version = f" v{p['version']}" if p["version"] else ""
                         tools = f"{p['tools']} tools" if p["tools"] else ""
                         hooks = f"{p['hooks']} hooks" if p["hooks"] else ""
-                        parts = [x for x in [tools, hooks] if x]
+                        commands = f"{p['commands']} commands" if p.get("commands") else ""
+                        parts = [x for x in [tools, hooks, commands] if x]
                         detail = f" ({', '.join(parts)})" if parts else ""
                         error = f" — {p['error']}" if p["error"] else ""
                         print(f"  {status} {p['name']}{version}{detail}{error}")
diff --git a/hermes_cli/commands.py b/hermes_cli/commands.py
index c8a0628fa..48ea5bb59 100644
--- a/hermes_cli/commands.py
+++ b/hermes_cli/commands.py
@@ -450,7 +450,7 @@ def _collect_gateway_skill_entries(
             name = sanitize_name(cmd_name) if sanitize_name else cmd_name
             if not name:
                 continue
-            desc = "Plugin command"
+            desc = plugin_cmds[cmd_name].get("description", "Plugin command")
             if len(desc) > desc_limit:
                 desc = desc[:desc_limit - 3] + "..."
             plugin_pairs.append((name, desc))
@@ -1139,6 +1139,22 @@ class SlashCommandCompleter(Completer):
                     display_meta=f"⚡ {short_desc}",
                 )
 
+        # Plugin-registered slash commands
+        try:
+            from hermes_cli.plugins import get_plugin_commands
+            for cmd_name, cmd_info in get_plugin_commands().items():
+                if cmd_name.startswith(word):
+                    desc = str(cmd_info.get("description", "Plugin command"))
+                    short_desc = desc[:50] + ("..." if len(desc) > 50 else "")
+                    yield Completion(
+                        self._completion_text(cmd_name, word),
+                        start_position=-len(word),
+                        display=f"/{cmd_name}",
+                        display_meta=f"🔌 {short_desc}",
+                    )
+        except Exception:
+            pass
+
 
 # ---------------------------------------------------------------------------
 # Inline auto-suggest (ghost text) for slash commands
diff --git a/hermes_cli/plugins.py b/hermes_cli/plugins.py
index 9d78ca47f..5e8ff8e4f 100644
--- a/hermes_cli/plugins.py
+++ b/hermes_cli/plugins.py
@@ -112,6 +112,7 @@ class LoadedPlugin:
     module: Optional[types.ModuleType] = None
     tools_registered: List[str] = field(default_factory=list)
     hooks_registered: List[str] = field(default_factory=list)
+    commands_registered: List[str] = field(default_factory=list)
     enabled: bool = False
     error: Optional[str] = None
 
@@ -211,6 +212,53 @@ class PluginContext:
         }
         logger.debug("Plugin %s registered CLI command: %s", self.manifest.name, name)
 
+    # -- slash command registration -------------------------------------------
+
+    def register_command(
+        self,
+        name: str,
+        handler: Callable,
+        description: str = "",
+    ) -> None:
+        """Register a slash command (e.g. ``/lcm``) available in CLI and gateway sessions.
+
+        The handler signature is ``fn(raw_args: str) -> str | None``.
+        It may also be an async callable — the gateway dispatch handles both.
+
+        Unlike ``register_cli_command()`` (which creates ``hermes <subcommand>``
+        terminal commands), this registers in-session slash commands that users
+        invoke during a conversation.
+
+        Names conflicting with built-in commands are rejected with a warning.
+        """
+        clean = name.lower().strip().lstrip("/").replace(" ", "-")
+        if not clean:
+            logger.warning(
+                "Plugin '%s' tried to register a command with an empty name.",
+                self.manifest.name,
+            )
+            return
+
+        # Reject if it conflicts with a built-in command
+        try:
+            from hermes_cli.commands import resolve_command
+            if resolve_command(clean) is not None:
+                logger.warning(
+                    "Plugin '%s' tried to register command '/%s' which conflicts "
+                    "with a built-in command. Skipping.",
+                    self.manifest.name, clean,
+                )
+                return
+        except Exception:
+            pass  # If commands module isn't available, skip the check
+
+        self._manager._plugin_commands[clean] = {
+            "handler": handler,
+            "description": description or "Plugin command",
+            "plugin": self.manifest.name,
+        }
+        logger.debug("Plugin %s registered command: /%s", self.manifest.name, clean)
+
     # -- context engine registration -----------------------------------------
 
     def register_context_engine(self, engine) -> None:
@@ -323,6 +371,7 @@ class PluginManager:
         self._plugin_tool_names: Set[str] = set()
         self._cli_commands: Dict[str, dict] = {}
         self._context_engine = None  # Set by a plugin via register_context_engine()
+        self._plugin_commands: Dict[str, dict] = {}  # Slash commands registered by plugins
         self._discovered: bool = False
         self._cli_ref = None  # Set by CLI after plugin discovery
         # Plugin skill registry: qualified name → metadata dict.
@@ -485,6 +534,10 @@ class PluginManager:
                         for h in p.hooks_registered
                     }
                 )
+                loaded.commands_registered = [
+                    c for c in self._plugin_commands
+                    if self._plugin_commands[c].get("plugin") == manifest.name
+                ]
                 loaded.enabled = True
 
         except Exception as exc:
@@ -598,6 +651,7 @@ class PluginManager:
                     "enabled": loaded.enabled,
                     "tools": len(loaded.tools_registered),
                     "hooks": len(loaded.hooks_registered),
+                    "commands": len(loaded.commands_registered),
                     "error": loaded.error,
                 }
             )
@@ -699,6 +753,20 @@ def get_plugin_context_engine():
     return get_plugin_manager()._context_engine
 
 
+def get_plugin_command_handler(name: str) -> Optional[Callable]:
+    """Return the handler for a plugin-registered slash command, or ``None``."""
+    entry = get_plugin_manager()._plugin_commands.get(name)
+    return entry["handler"] if entry else None
+
+
+def get_plugin_commands() -> Dict[str, dict]:
+    """Return the full plugin commands dict (name → {handler, description, plugin}).
+
+    Safe to call before discovery — returns an empty dict if no plugins loaded.
+    """
+    return get_plugin_manager()._plugin_commands
+
+
 def get_plugin_toolsets() -> List[tuple]:
     """Return plugin toolsets as ``(key, label, description)`` tuples.
 
diff --git a/tests/hermes_cli/test_plugins.py b/tests/hermes_cli/test_plugins.py
index 7be1be617..acc63e906 100644
--- a/tests/hermes_cli/test_plugins.py
+++ b/tests/hermes_cli/test_plugins.py
@@ -18,6 +18,8 @@ from hermes_cli.plugins import (
     PluginManager,
     PluginManifest,
     get_plugin_manager,
+    get_plugin_command_handler,
+    get_plugin_commands,
     get_pre_tool_call_block_message,
     discover_plugins,
     invoke_hook,
@@ -605,7 +607,160 @@ class TestPreLlmCallTargetRouting:
         assert "plain text C" in _plugin_user_context
 
 
-# NOTE: TestPluginCommands removed – register_command() was never implemented
-# in PluginContext (hermes_cli/plugins.py).  The tests referenced _plugin_commands,
-# commands_registered, get_plugin_command_handler, and GATEWAY_KNOWN_COMMANDS
-# integration — all of which are unimplemented features.
+# ── TestPluginCommands ────────────────────────────────────────────────────
+
+
+class TestPluginCommands:
+    """Tests for plugin slash command registration via register_command()."""
+
+    def test_register_command_basic(self):
+        """register_command() stores handler, description, and plugin name."""
+        mgr = PluginManager()
+        manifest = PluginManifest(name="test-plugin", source="user")
+        ctx = PluginContext(manifest, mgr)
+
+        handler = lambda args: f"echo {args}"
+        ctx.register_command("mycmd", handler, description="My custom command")
+
+        assert "mycmd" in mgr._plugin_commands
+        entry = mgr._plugin_commands["mycmd"]
+        assert entry["handler"] is handler
+        assert entry["description"] == "My custom command"
+        assert entry["plugin"] == "test-plugin"
+
+    def test_register_command_normalizes_name(self):
+        """Names are lowercased, stripped, and leading slashes removed."""
+        mgr = PluginManager()
+        manifest = PluginManifest(name="test-plugin", source="user")
+        ctx = PluginContext(manifest, mgr)
+
+        ctx.register_command("/MyCmd ", lambda a: a, description="test")
+        assert "mycmd" in mgr._plugin_commands
+        assert "/MyCmd " not in mgr._plugin_commands
+
+    def test_register_command_empty_name_rejected(self, caplog):
+        """Empty name after normalization is rejected with a warning."""
+        mgr = PluginManager()
+        manifest = PluginManifest(name="test-plugin", source="user")
+        ctx = PluginContext(manifest, mgr)
+
+        with caplog.at_level(logging.WARNING):
+            ctx.register_command("", lambda a: a)
+        assert len(mgr._plugin_commands) == 0
+        assert "empty name" in caplog.text
+
+    def test_register_command_builtin_conflict_rejected(self, caplog):
+        """Commands that conflict with built-in names are rejected."""
+        mgr = PluginManager()
+        manifest = PluginManifest(name="test-plugin", source="user")
+        ctx = PluginContext(manifest, mgr)
+
+        with caplog.at_level(logging.WARNING):
+            ctx.register_command("help", lambda a: a)
+        assert "help" not in mgr._plugin_commands
+        assert "conflicts" in caplog.text.lower()
+
+    def test_register_command_default_description(self):
+        """Missing description defaults to 'Plugin command'."""
+        mgr = PluginManager()
+        manifest = PluginManifest(name="test-plugin", source="user")
+        ctx = PluginContext(manifest, mgr)
+
+        ctx.register_command("status-cmd", lambda a: a)
+        assert mgr._plugin_commands["status-cmd"]["description"] == "Plugin command"
+
+    def test_get_plugin_command_handler_found(self):
+        """get_plugin_command_handler() returns the handler for a registered command."""
+        mgr = PluginManager()
+        manifest = PluginManifest(name="test-plugin", source="user")
+        ctx = PluginContext(manifest, mgr)
+
+        handler = lambda args: f"result: {args}"
+        ctx.register_command("mycmd", handler, description="test")
+
+        with patch("hermes_cli.plugins._plugin_manager", mgr):
+            result = get_plugin_command_handler("mycmd")
+            assert result is handler
+
+    def test_get_plugin_command_handler_not_found(self):
+        """get_plugin_command_handler() returns None for unregistered commands."""
+        mgr = PluginManager()
+        with patch("hermes_cli.plugins._plugin_manager", mgr):
+            assert get_plugin_command_handler("nonexistent") is None
+
+    def test_get_plugin_commands_returns_dict(self):
+        """get_plugin_commands() returns the full commands dict."""
+        mgr = PluginManager()
+        manifest = PluginManifest(name="test-plugin", source="user")
+        ctx = PluginContext(manifest, mgr)
+        ctx.register_command("cmd-a", lambda a: a, description="A")
+        ctx.register_command("cmd-b", lambda a: a, description="B")
+
+        with patch("hermes_cli.plugins._plugin_manager", mgr):
+            cmds = get_plugin_commands()
+            assert "cmd-a" in cmds
+            assert "cmd-b" in cmds
+            assert cmds["cmd-a"]["description"] == "A"
+
+    def test_commands_tracked_on_loaded_plugin(self, tmp_path, monkeypatch):
+        """Commands registered during discover_and_load() are tracked on LoadedPlugin."""
+        plugins_dir = tmp_path / "hermes_test" / "plugins"
+        _make_plugin_dir(
+            plugins_dir, "cmd-plugin",
+            register_body=(
+                'ctx.register_command("mycmd", lambda a: "ok", description="Test")'
+            ),
+        )
+        monkeypatch.setenv("HERMES_HOME", str(tmp_path / "hermes_test"))
+
+        mgr = PluginManager()
+        mgr.discover_and_load()
+
+        loaded = mgr._plugins["cmd-plugin"]
+        assert loaded.enabled
+        assert "mycmd" in loaded.commands_registered
+
+    def test_commands_in_list_plugins_output(self, tmp_path, monkeypatch):
+        """list_plugins() includes command count."""
+        plugins_dir = tmp_path / "hermes_test" / "plugins"
+        _make_plugin_dir(
+            plugins_dir, "cmd-plugin",
+            register_body=(
+                'ctx.register_command("mycmd", lambda a: "ok", description="Test")'
+            ),
+        )
+        monkeypatch.setenv("HERMES_HOME", str(tmp_path / "hermes_test"))
+
+        mgr = PluginManager()
+        mgr.discover_and_load()
+
+        info = mgr.list_plugins()
+        assert len(info) == 1
+        assert info[0]["commands"] == 1
+
+    def test_handler_receives_raw_args(self):
+        """The handler is called with the raw argument string."""
+        mgr = PluginManager()
+        manifest = PluginManifest(name="test-plugin", source="user")
+        ctx = PluginContext(manifest, mgr)
+
+        received = []
+        ctx.register_command("echo", lambda args: received.append(args) or "ok")
+
+        handler = mgr._plugin_commands["echo"]["handler"]
+        handler("hello world")
+        assert received == ["hello world"]
+
+    def test_multiple_plugins_register_different_commands(self):
+        """Multiple plugins can each register their own commands."""
+        mgr = PluginManager()
+
+        for plugin_name, cmd_name in [("plugin-a", "cmd-a"), ("plugin-b", "cmd-b")]:
+            manifest = PluginManifest(name=plugin_name, source="user")
+            ctx = PluginContext(manifest, mgr)
+            ctx.register_command(cmd_name, lambda a: a, description=f"From {plugin_name}")
+
+        assert "cmd-a" in mgr._plugin_commands
+        assert "cmd-b" in mgr._plugin_commands
+        assert mgr._plugin_commands["cmd-a"]["plugin"] == "plugin-a"
+        assert mgr._plugin_commands["cmd-b"]["plugin"] == "plugin-b"