5879b3ef82
Plugin context from pre_llm_call hooks was injected into the system prompt, breaking the prompt cache prefix every turn when content changed (typical for memory plugins). Now all plugin context goes into the current turn's user message — the system prompt stays identical across turns, preserving cached tokens. The system prompt is reserved for Hermes internals. Plugins contribute context alongside the user's input. Also adds comprehensive documentation for all 6 plugin hooks: pre_tool_call, post_tool_call, pre_llm_call, post_llm_call, on_session_start, on_session_end — each with full callback signatures, parameter tables, firing conditions, and examples. Supersedes #5138 which identified the same cache-busting bug and proposed an uncached system suffix approach. This fix goes further by removing system prompt injection entirely. Co-identified-by: OutThisLife (PR #5138)
572 lines
20 KiB
Python
572 lines
20 KiB
Python
"""
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Hermes Plugin System
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====================
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Discovers, loads, and manages plugins from three sources:
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1. **User plugins** – ``~/.hermes/plugins/<name>/``
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2. **Project plugins** – ``./.hermes/plugins/<name>/`` (opt-in via
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``HERMES_ENABLE_PROJECT_PLUGINS``)
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3. **Pip plugins** – packages that expose the ``hermes_agent.plugins``
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entry-point group.
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Each directory plugin must contain a ``plugin.yaml`` manifest **and** an
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``__init__.py`` with a ``register(ctx)`` function.
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Lifecycle hooks
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---------------
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Plugins may register callbacks for any of the hooks in ``VALID_HOOKS``.
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The agent core calls ``invoke_hook(name, **kwargs)`` at the appropriate
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points.
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Tool registration
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-----------------
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``PluginContext.register_tool()`` delegates to ``tools.registry.register()``
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so plugin-defined tools appear alongside the built-in tools.
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"""
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from __future__ import annotations
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import importlib
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import importlib.metadata
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import importlib.util
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import logging
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import os
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import sys
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import types
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from dataclasses import dataclass, field
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from pathlib import Path
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from typing import Any, Callable, Dict, List, Optional, Set
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from utils import env_var_enabled
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try:
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import yaml
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except ImportError: # pragma: no cover – yaml is optional at import time
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yaml = None # type: ignore[assignment]
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logger = logging.getLogger(__name__)
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# ---------------------------------------------------------------------------
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# Constants
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# ---------------------------------------------------------------------------
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VALID_HOOKS: Set[str] = {
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"pre_tool_call",
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"post_tool_call",
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"pre_llm_call",
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"post_llm_call",
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"on_session_start",
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"on_session_end",
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}
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ENTRY_POINTS_GROUP = "hermes_agent.plugins"
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_NS_PARENT = "hermes_plugins"
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def _env_enabled(name: str) -> bool:
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"""Return True when an env var is set to a truthy opt-in value."""
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return env_var_enabled(name)
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def _get_disabled_plugins() -> set:
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"""Read the disabled plugins list from config.yaml."""
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try:
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from hermes_cli.config import load_config
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config = load_config()
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disabled = config.get("plugins", {}).get("disabled", [])
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return set(disabled) if isinstance(disabled, list) else set()
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except Exception:
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return set()
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# ---------------------------------------------------------------------------
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# Data classes
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# ---------------------------------------------------------------------------
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@dataclass
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class PluginManifest:
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"""Parsed representation of a plugin.yaml manifest."""
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name: str
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version: str = ""
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description: str = ""
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author: str = ""
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requires_env: List[str] = field(default_factory=list)
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provides_tools: List[str] = field(default_factory=list)
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provides_hooks: List[str] = field(default_factory=list)
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source: str = "" # "user", "project", or "entrypoint"
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path: Optional[str] = None
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@dataclass
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class LoadedPlugin:
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"""Runtime state for a single loaded plugin."""
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manifest: PluginManifest
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module: Optional[types.ModuleType] = None
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tools_registered: List[str] = field(default_factory=list)
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hooks_registered: List[str] = field(default_factory=list)
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enabled: bool = False
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error: Optional[str] = None
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# ---------------------------------------------------------------------------
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# PluginContext – handed to each plugin's ``register()`` function
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# ---------------------------------------------------------------------------
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class PluginContext:
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"""Facade given to plugins so they can register tools and hooks."""
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def __init__(self, manifest: PluginManifest, manager: "PluginManager"):
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self.manifest = manifest
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self._manager = manager
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# -- tool registration --------------------------------------------------
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def register_tool(
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self,
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name: str,
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toolset: str,
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schema: dict,
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handler: Callable,
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check_fn: Callable | None = None,
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requires_env: list | None = None,
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is_async: bool = False,
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description: str = "",
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emoji: str = "",
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) -> None:
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"""Register a tool in the global registry **and** track it as plugin-provided."""
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from tools.registry import registry
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registry.register(
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name=name,
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toolset=toolset,
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schema=schema,
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handler=handler,
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check_fn=check_fn,
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requires_env=requires_env,
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is_async=is_async,
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description=description,
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emoji=emoji,
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)
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self._manager._plugin_tool_names.add(name)
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logger.debug("Plugin %s registered tool: %s", self.manifest.name, name)
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# -- message injection --------------------------------------------------
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def inject_message(self, content: str, role: str = "user") -> bool:
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"""Inject a message into the active conversation.
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If the agent is idle (waiting for user input), this starts a new turn.
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If the agent is running, this interrupts and injects the message.
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This enables plugins (e.g. remote control viewers, messaging bridges)
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to send messages into the conversation from external sources.
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Returns True if the message was queued successfully.
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"""
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cli = self._manager._cli_ref
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if cli is None:
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logger.warning("inject_message: no CLI reference (not available in gateway mode)")
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return False
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msg = content if role == "user" else f"[{role}] {content}"
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if getattr(cli, "_agent_running", False):
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# Agent is mid-turn — interrupt with the message
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cli._interrupt_queue.put(msg)
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else:
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# Agent is idle — queue as next input
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cli._pending_input.put(msg)
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return True
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# -- hook registration --------------------------------------------------
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def register_hook(self, hook_name: str, callback: Callable) -> None:
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"""Register a lifecycle hook callback.
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Unknown hook names produce a warning but are still stored so
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forward-compatible plugins don't break.
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"""
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if hook_name not in VALID_HOOKS:
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logger.warning(
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"Plugin '%s' registered unknown hook '%s' "
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"(valid: %s)",
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self.manifest.name,
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hook_name,
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", ".join(sorted(VALID_HOOKS)),
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)
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self._manager._hooks.setdefault(hook_name, []).append(callback)
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logger.debug("Plugin %s registered hook: %s", self.manifest.name, hook_name)
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# ---------------------------------------------------------------------------
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# PluginManager
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# ---------------------------------------------------------------------------
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class PluginManager:
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"""Central manager that discovers, loads, and invokes plugins."""
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def __init__(self) -> None:
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self._plugins: Dict[str, LoadedPlugin] = {}
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self._hooks: Dict[str, List[Callable]] = {}
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self._plugin_tool_names: Set[str] = set()
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self._discovered: bool = False
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self._cli_ref = None # Set by CLI after plugin discovery
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# -----------------------------------------------------------------------
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# Public
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# -----------------------------------------------------------------------
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def discover_and_load(self) -> None:
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"""Scan all plugin sources and load each plugin found."""
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if self._discovered:
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return
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self._discovered = True
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manifests: List[PluginManifest] = []
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# 1. User plugins (~/.hermes/plugins/)
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hermes_home = os.environ.get("HERMES_HOME", os.path.expanduser("~/.hermes"))
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user_dir = Path(hermes_home) / "plugins"
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manifests.extend(self._scan_directory(user_dir, source="user"))
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# 2. Project plugins (./.hermes/plugins/)
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if _env_enabled("HERMES_ENABLE_PROJECT_PLUGINS"):
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project_dir = Path.cwd() / ".hermes" / "plugins"
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manifests.extend(self._scan_directory(project_dir, source="project"))
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# 3. Pip / entry-point plugins
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manifests.extend(self._scan_entry_points())
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# Load each manifest (skip user-disabled plugins)
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disabled = _get_disabled_plugins()
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for manifest in manifests:
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if manifest.name in disabled:
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loaded = LoadedPlugin(manifest=manifest, enabled=False)
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loaded.error = "disabled via config"
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self._plugins[manifest.name] = loaded
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logger.debug("Skipping disabled plugin '%s'", manifest.name)
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continue
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self._load_plugin(manifest)
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if manifests:
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logger.info(
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"Plugin discovery complete: %d found, %d enabled",
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len(self._plugins),
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sum(1 for p in self._plugins.values() if p.enabled),
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)
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# -----------------------------------------------------------------------
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# Directory scanning
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# -----------------------------------------------------------------------
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def _scan_directory(self, path: Path, source: str) -> List[PluginManifest]:
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"""Read ``plugin.yaml`` manifests from subdirectories of *path*."""
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manifests: List[PluginManifest] = []
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if not path.is_dir():
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return manifests
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for child in sorted(path.iterdir()):
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if not child.is_dir():
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continue
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manifest_file = child / "plugin.yaml"
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if not manifest_file.exists():
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manifest_file = child / "plugin.yml"
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if not manifest_file.exists():
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logger.debug("Skipping %s (no plugin.yaml)", child)
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continue
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try:
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if yaml is None:
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logger.warning("PyYAML not installed – cannot load %s", manifest_file)
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continue
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data = yaml.safe_load(manifest_file.read_text()) or {}
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manifest = PluginManifest(
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name=data.get("name", child.name),
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version=str(data.get("version", "")),
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description=data.get("description", ""),
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author=data.get("author", ""),
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requires_env=data.get("requires_env", []),
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provides_tools=data.get("provides_tools", []),
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provides_hooks=data.get("provides_hooks", []),
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source=source,
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path=str(child),
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)
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manifests.append(manifest)
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except Exception as exc:
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logger.warning("Failed to parse %s: %s", manifest_file, exc)
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return manifests
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# -----------------------------------------------------------------------
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# Entry-point scanning
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# -----------------------------------------------------------------------
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def _scan_entry_points(self) -> List[PluginManifest]:
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"""Check ``importlib.metadata`` for pip-installed plugins."""
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manifests: List[PluginManifest] = []
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try:
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eps = importlib.metadata.entry_points()
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# Python 3.12+ returns a SelectableGroups; earlier returns dict
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if hasattr(eps, "select"):
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group_eps = eps.select(group=ENTRY_POINTS_GROUP)
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elif isinstance(eps, dict):
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group_eps = eps.get(ENTRY_POINTS_GROUP, [])
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else:
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group_eps = [ep for ep in eps if ep.group == ENTRY_POINTS_GROUP]
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for ep in group_eps:
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manifest = PluginManifest(
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name=ep.name,
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source="entrypoint",
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path=ep.value,
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)
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manifests.append(manifest)
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except Exception as exc:
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logger.debug("Entry-point scan failed: %s", exc)
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return manifests
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# -----------------------------------------------------------------------
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# Loading
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# -----------------------------------------------------------------------
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def _load_plugin(self, manifest: PluginManifest) -> None:
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"""Import a plugin module and call its ``register(ctx)`` function."""
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loaded = LoadedPlugin(manifest=manifest)
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try:
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if manifest.source in ("user", "project"):
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module = self._load_directory_module(manifest)
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else:
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module = self._load_entrypoint_module(manifest)
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loaded.module = module
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# Call register()
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register_fn = getattr(module, "register", None)
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if register_fn is None:
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loaded.error = "no register() function"
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logger.warning("Plugin '%s' has no register() function", manifest.name)
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else:
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ctx = PluginContext(manifest, self)
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register_fn(ctx)
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loaded.tools_registered = [
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t for t in self._plugin_tool_names
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if t not in {
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n
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for name, p in self._plugins.items()
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for n in p.tools_registered
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}
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]
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loaded.hooks_registered = list(
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{
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h
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for h, cbs in self._hooks.items()
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if cbs # non-empty
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}
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- {
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h
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for name, p in self._plugins.items()
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for h in p.hooks_registered
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}
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)
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loaded.enabled = True
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except Exception as exc:
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loaded.error = str(exc)
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logger.warning("Failed to load plugin '%s': %s", manifest.name, exc)
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self._plugins[manifest.name] = loaded
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def _load_directory_module(self, manifest: PluginManifest) -> types.ModuleType:
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"""Import a directory-based plugin as ``hermes_plugins.<name>``."""
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plugin_dir = Path(manifest.path) # type: ignore[arg-type]
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init_file = plugin_dir / "__init__.py"
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if not init_file.exists():
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raise FileNotFoundError(f"No __init__.py in {plugin_dir}")
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# Ensure the namespace parent package exists
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if _NS_PARENT not in sys.modules:
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ns_pkg = types.ModuleType(_NS_PARENT)
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ns_pkg.__path__ = [] # type: ignore[attr-defined]
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ns_pkg.__package__ = _NS_PARENT
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sys.modules[_NS_PARENT] = ns_pkg
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module_name = f"{_NS_PARENT}.{manifest.name.replace('-', '_')}"
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spec = importlib.util.spec_from_file_location(
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module_name,
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init_file,
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submodule_search_locations=[str(plugin_dir)],
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)
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if spec is None or spec.loader is None:
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raise ImportError(f"Cannot create module spec for {init_file}")
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module = importlib.util.module_from_spec(spec)
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module.__package__ = module_name
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module.__path__ = [str(plugin_dir)] # type: ignore[attr-defined]
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sys.modules[module_name] = module
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spec.loader.exec_module(module)
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return module
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def _load_entrypoint_module(self, manifest: PluginManifest) -> types.ModuleType:
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"""Load a pip-installed plugin via its entry-point reference."""
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eps = importlib.metadata.entry_points()
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if hasattr(eps, "select"):
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group_eps = eps.select(group=ENTRY_POINTS_GROUP)
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elif isinstance(eps, dict):
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group_eps = eps.get(ENTRY_POINTS_GROUP, [])
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else:
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group_eps = [ep for ep in eps if ep.group == ENTRY_POINTS_GROUP]
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for ep in group_eps:
|
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if ep.name == manifest.name:
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return ep.load()
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raise ImportError(
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f"Entry point '{manifest.name}' not found in group '{ENTRY_POINTS_GROUP}'"
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)
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# -----------------------------------------------------------------------
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# Hook invocation
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# -----------------------------------------------------------------------
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def invoke_hook(self, hook_name: str, **kwargs: Any) -> List[Any]:
|
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"""Call all registered callbacks for *hook_name*.
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Each callback is wrapped in its own try/except so a misbehaving
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plugin cannot break the core agent loop.
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Returns a list of non-``None`` return values from callbacks.
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|
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For ``pre_llm_call``, callbacks may return a dict describing
|
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context to inject into the current turn's user message::
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{"context": "recalled text..."}
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"recalled text..." # plain string, equivalent
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|
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Context is ALWAYS injected into the user message, never the
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system prompt. This preserves the prompt cache prefix — the
|
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system prompt stays identical across turns so cached tokens
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are reused. All injected context is ephemeral — never
|
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persisted to session DB.
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"""
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callbacks = self._hooks.get(hook_name, [])
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results: List[Any] = []
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for cb in callbacks:
|
||
try:
|
||
ret = cb(**kwargs)
|
||
if ret is not None:
|
||
results.append(ret)
|
||
except Exception as exc:
|
||
logger.warning(
|
||
"Hook '%s' callback %s raised: %s",
|
||
hook_name,
|
||
getattr(cb, "__name__", repr(cb)),
|
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exc,
|
||
)
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return results
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|
||
# -----------------------------------------------------------------------
|
||
# Introspection
|
||
# -----------------------------------------------------------------------
|
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|
||
def list_plugins(self) -> List[Dict[str, Any]]:
|
||
"""Return a list of info dicts for all discovered plugins."""
|
||
result: List[Dict[str, Any]] = []
|
||
for name, loaded in sorted(self._plugins.items()):
|
||
result.append(
|
||
{
|
||
"name": name,
|
||
"version": loaded.manifest.version,
|
||
"description": loaded.manifest.description,
|
||
"source": loaded.manifest.source,
|
||
"enabled": loaded.enabled,
|
||
"tools": len(loaded.tools_registered),
|
||
"hooks": len(loaded.hooks_registered),
|
||
"error": loaded.error,
|
||
}
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||
)
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||
return result
|
||
|
||
|
||
# ---------------------------------------------------------------------------
|
||
# Module-level singleton & convenience functions
|
||
# ---------------------------------------------------------------------------
|
||
|
||
_plugin_manager: Optional[PluginManager] = None
|
||
|
||
|
||
def get_plugin_manager() -> PluginManager:
|
||
"""Return (and lazily create) the global PluginManager singleton."""
|
||
global _plugin_manager
|
||
if _plugin_manager is None:
|
||
_plugin_manager = PluginManager()
|
||
return _plugin_manager
|
||
|
||
|
||
def discover_plugins() -> None:
|
||
"""Discover and load all plugins (idempotent)."""
|
||
get_plugin_manager().discover_and_load()
|
||
|
||
|
||
def invoke_hook(hook_name: str, **kwargs: Any) -> List[Any]:
|
||
"""Invoke a lifecycle hook on all loaded plugins.
|
||
|
||
Returns a list of non-``None`` return values from plugin callbacks.
|
||
"""
|
||
return get_plugin_manager().invoke_hook(hook_name, **kwargs)
|
||
|
||
|
||
def get_plugin_tool_names() -> Set[str]:
|
||
"""Return the set of tool names registered by plugins."""
|
||
return get_plugin_manager()._plugin_tool_names
|
||
|
||
|
||
def get_plugin_toolsets() -> List[tuple]:
|
||
"""Return plugin toolsets as ``(key, label, description)`` tuples.
|
||
|
||
Used by the ``hermes tools`` TUI so plugin-provided toolsets appear
|
||
alongside the built-in ones and can be toggled on/off per platform.
|
||
"""
|
||
manager = get_plugin_manager()
|
||
if not manager._plugin_tool_names:
|
||
return []
|
||
|
||
try:
|
||
from tools.registry import registry
|
||
except Exception:
|
||
return []
|
||
|
||
# Group plugin tool names by their toolset
|
||
toolset_tools: Dict[str, List[str]] = {}
|
||
toolset_plugin: Dict[str, LoadedPlugin] = {}
|
||
for tool_name in manager._plugin_tool_names:
|
||
entry = registry._tools.get(tool_name)
|
||
if not entry:
|
||
continue
|
||
ts = entry.toolset
|
||
toolset_tools.setdefault(ts, []).append(entry.name)
|
||
|
||
# Map toolsets back to the plugin that registered them
|
||
for _name, loaded in manager._plugins.items():
|
||
for tool_name in loaded.tools_registered:
|
||
entry = registry._tools.get(tool_name)
|
||
if entry and entry.toolset in toolset_tools:
|
||
toolset_plugin.setdefault(entry.toolset, loaded)
|
||
|
||
result = []
|
||
for ts_key in sorted(toolset_tools):
|
||
plugin = toolset_plugin.get(ts_key)
|
||
label = f"🔌 {ts_key.replace('_', ' ').title()}"
|
||
if plugin and plugin.manifest.description:
|
||
desc = plugin.manifest.description
|
||
else:
|
||
desc = ", ".join(sorted(toolset_tools[ts_key]))
|
||
result.append((ts_key, label, desc))
|
||
|
||
return result
|