Hermes Agent Plugin -- Intaris

A Hermes Agent plugin that evaluates every tool call through Intaris safety pipeline before allowing execution.

Features

• Tool Call Guardrails: Every tool call is evaluated via POST /api/v1/evaluate before execution -- including built-in tools
• Full Blocking: Denied and escalated tool calls are blocked and return an error to the LLM
• Session Management: Creates/manages Intaris sessions mirroring Hermes agent sessions
• Escalation Handling: Escalated tool calls enter a polling loop waiting for human approval via the Intaris UI
• Session Recording: Optional audit trail recording of all messages, tool calls, and results
• MCP Tool Proxy: Fetches and registers MCP tools from Intaris-connected MCP servers as native Hermes tools
• Reasoning Context: Forwards user messages and assistant responses to Intaris for informed safety decisions
• Context Injection: Injects behavioral alerts into the agent's system prompt via pre_llm_call
• Fail-open/Fail-closed: Configurable behavior when Intaris is unreachable

Prerequisites

A running Intaris server accessible via HTTP.

Install

Via pip (recommended)

pip install hermes-intaris

The plugin is auto-discovered by Hermes via the hermes_agent.plugins entry point.

Via directory

git clone https://github.com/fpytloun/intaris.git
cp -r intaris/integrations/hermes/hermes_intaris ~/.hermes/plugins/intaris
cp intaris/integrations/hermes/hermes_intaris/plugin.yaml ~/.hermes/plugins/intaris/

Configure

Set environment variables:

export INTARIS_API_KEY=your-api-key
export INTARIS_URL=http://localhost:8060  # default

Configuration Options

How It Works

Tool Wrapping

The plugin uses a tool wrapping approach: during initialization, it captures every tool handler registered in Hermes's tool registry and re-registers each with a guarded wrapper. The wrapper calls POST /api/v1/evaluate before dispatching to the original handler.

This works because Hermes plugins load after built-in tools, and the tool registry allows handler replacement. The wrapper is transparent -- same schema, same toolset, same availability checks.

Hook Flow

1. on_session_start: Creates an Intaris session via POST /api/v1/intention
2. pre_llm_call: Forwards user message as reasoning context via POST /api/v1/reasoning
3. Tool wrapper: Evaluates every tool call via POST /api/v1/evaluate
   • approve: calls original handler, returns result
   • deny: returns {"error": "BLOCKED by Intaris: ..."} to the LLM
   • escalate: polls for user decision, blocks until resolved
4. pre_tool_call: Records tool call events for session recording
5. post_tool_call: Records tool results, sends periodic checkpoints
6. post_llm_call: Captures assistant response for reasoning context
7. on_session_end: Signals session completion to Intaris

MCP Tool Proxy

When INTARIS_MCP_TOOLS=true (default), the plugin fetches MCP tools from Intaris and registers them as native Hermes tools. These tools proxy execution through POST /api/v1/mcp/call with full safety evaluation server-side.

Risks and Caveats

Registry internal access

The plugin accesses registry._tools (a private attribute of Hermes's ToolRegistry) to enumerate and wrap existing tool handlers. While this is a stable internal API used by Hermes's own model_tools.py, it is not part of the public plugin contract and could change in future Hermes versions. The public registry.register() method is used for re-registration.

Latency on every tool call

Every tool call goes through Intaris evaluation, adding network round-trip latency. Read-only tools are fast-pathed by Intaris (<1ms server-side), but the HTTP round-trip adds ~5-20ms depending on network conditions. Write operations that require LLM evaluation add up to 4 seconds.

Synchronous blocking

Tool evaluation is synchronous -- the Hermes agent loop blocks while waiting for Intaris to respond. For escalated tool calls, the agent blocks until a human approves or denies in the Intaris UI (or the timeout expires). This is by design for safety, but means the agent cannot proceed with other work during escalation.

No sub-agent linking

Hermes's delegate_task tool spawns sub-agents, but the plugin system does not expose pre/post hooks for sub-agent lifecycle. Each sub-agent gets its own on_session_start but without parent session linkage. Sub-agent sessions appear as independent sessions in Intaris.

No session reset hook

Hermes has no equivalent of a "session reset" event. If the user runs /new or /reset, the on_session_end hook fires with completed=False, but the plugin cannot distinguish a reset from an idle timeout.

Plugin load order dependency

The tool wrapping approach depends on plugins loading after built-in tools. This is the current Hermes behavior (built-in tools register at import time, plugins load via discover_plugins() afterward), but is not a guaranteed contract.

Verify

After starting Hermes with the plugin, open the Intaris management UI at http://localhost:8060/ui. You should see a new session appear in the Sessions tab when Hermes starts a conversation.

License

MIT