feat: built-in boot-md hook — run BOOT.md on gateway startup (#3733)

The gateway now ships with a built-in boot-md hook that checks for
~/.hermes/BOOT.md on every startup. If the file exists, the agent
executes its instructions in a background thread. No installation
or configuration needed — just create the file.

No BOOT.md = zero overhead (the hook silently returns).

Implementation:
- gateway/builtin_hooks/boot_md.py: handler with boot prompt,
  background thread, [SILENT] suppression, error handling
- gateway/hooks.py: _register_builtin_hooks() called at the start
  of discover_and_load() to wire in built-in hooks
- Docs updated: hooks page documents BOOT.md as a built-in feature

gateway/builtin_hooks/__init__.py

@@ -0,0 +1 @@
+"""Built-in gateway hooks that are always registered."""

gateway/builtin_hooks/boot_md.py

@@ -0,0 +1,86 @@
+"""Built-in boot-md hook — run ~/.hermes/BOOT.md on gateway startup.
+
+This hook is always registered. It silently skips if no BOOT.md exists.
+To activate, create ``~/.hermes/BOOT.md`` with instructions for the
+agent to execute on every gateway restart.
+
+Example BOOT.md::
+
+    # Startup Checklist
+
+    1. Check if any cron jobs failed overnight
+    2. Send a status update to Discord #general
+    3. If there are errors in /opt/app/deploy.log, summarize them
+
+The agent runs in a background thread so it doesn't block gateway
+startup. If nothing needs attention, it replies with [SILENT] to
+suppress delivery.
+"""
+
+import logging
+import os
+import threading
+from pathlib import Path
+
+logger = logging.getLogger("hooks.boot-md")
+
+HERMES_HOME = Path(os.environ.get("HERMES_HOME", Path.home() / ".hermes"))
+BOOT_FILE = HERMES_HOME / "BOOT.md"
+
+
+def _build_boot_prompt(content: str) -> str:
+    """Wrap BOOT.md content in a system-level instruction."""
+    return (
+        "You are running a startup boot checklist. Follow the BOOT.md "
+        "instructions below exactly.\n\n"
+        "---\n"
+        f"{content}\n"
+        "---\n\n"
+        "Execute each instruction. If you need to send a message to a "
+        "platform, use the send_message tool.\n"
+        "If nothing needs attention and there is nothing to report, "
+        "reply with ONLY: [SILENT]"
+    )
+
+
+def _run_boot_agent(content: str) -> None:
+    """Spawn a one-shot agent session to execute the boot instructions."""
+    try:
+        from run_agent import AIAgent
+
+        prompt = _build_boot_prompt(content)
+        agent = AIAgent(
+            quiet_mode=True,
+            skip_context_files=True,
+            skip_memory=True,
+            max_iterations=20,
+        )
+        result = agent.run_conversation(prompt)
+        response = result.get("final_response", "")
+        if response and "[SILENT]" not in response:
+            logger.info("boot-md completed: %s", response[:200])
+        else:
+            logger.info("boot-md completed (nothing to report)")
+    except Exception as e:
+        logger.error("boot-md agent failed: %s", e)
+
+
+async def handle(event_type: str, context: dict) -> None:
+    """Gateway startup handler — run BOOT.md if it exists."""
+    if not BOOT_FILE.exists():
+        return
+
+    content = BOOT_FILE.read_text(encoding="utf-8").strip()
+    if not content:
+        return
+
+    logger.info("Running BOOT.md (%d chars)", len(content))
+
+    # Run in a background thread so we don't block gateway startup.
+    thread = threading.Thread(
+        target=_run_boot_agent,
+        args=(content,),
+        name="boot-md",
+        daemon=True,
+    )
+    thread.start()

gateway/hooks.py

@@ -51,14 +51,33 @@ class HookRegistry:
         """Return metadata about all loaded hooks."""
         return list(self._loaded_hooks)
 
+    def _register_builtin_hooks(self) -> None:
+        """Register built-in hooks that are always active."""
+        try:
+            from gateway.builtin_hooks.boot_md import handle as boot_md_handle
+
+            self._handlers.setdefault("gateway:startup", []).append(boot_md_handle)
+            self._loaded_hooks.append({
+                "name": "boot-md",
+                "description": "Run ~/.hermes/BOOT.md on gateway startup",
+                "events": ["gateway:startup"],
+                "path": "(builtin)",
+            })
+        except Exception as e:
+            print(f"[hooks] Could not load built-in boot-md hook: {e}", flush=True)
+
     def discover_and_load(self) -> None:
         """
         Scan the hooks directory for hook directories and load their handlers.
 
+        Also registers built-in hooks that are always active.
+
         Each hook directory must contain:
           - HOOK.yaml with at least 'name' and 'events' keys
           - handler.py with a top-level 'handle' function (sync or async)
         """
+        self._register_builtin_hooks()
+
         if not HOOKS_DIR.exists():
             return
 

website/docs/user-guide/features/hooks.md

@@ -88,6 +88,26 @@ Handlers registered for `command:*` fire for any `command:` event (`command:mode
 
 ### Examples
 
+#### Boot Checklist (BOOT.md) — Built-in
+
+The gateway ships with a built-in `boot-md` hook that looks for `~/.hermes/BOOT.md` on every startup. If the file exists, the agent runs its instructions in a background session. No installation needed — just create the file.
+
+**Create `~/.hermes/BOOT.md`:**
+
+```markdown
+# Startup Checklist
+
+1. Check if any cron jobs failed overnight — run `hermes cron list`
+2. Send a message to Discord #general saying "Gateway restarted, all systems go"
+3. Check if /opt/app/deploy.log has any errors from the last 24 hours
+```
+
+The agent runs these instructions in a background thread so it doesn't block gateway startup. If nothing needs attention, the agent replies with `[SILENT]` and no message is delivered.
+
+:::tip
+No BOOT.md? The hook silently skips — zero overhead. Create the file whenever you need startup automation, delete it when you don't.
+:::
+
 #### Telegram Alert on Long Tasks
 
 Send yourself a message when the agent takes more than 10 steps: