hermes-agent/AGENTS.md

Hermes Agent - Development Guide

Instructions for AI coding assistants and developers working on the hermes-agent codebase.

Development Environment

source .venv/bin/activate  # ALWAYS activate before running Python

Project Structure

hermes-agent/
├── run_agent.py          # AIAgent class — core conversation loop
├── model_tools.py        # Tool orchestration, _discover_tools(), handle_function_call()
├── toolsets.py           # Toolset definitions, _HERMES_CORE_TOOLS list
├── cli.py                # HermesCLI class — interactive CLI orchestrator
├── hermes_state.py       # SessionDB — SQLite session store (FTS5 search)
├── agent/                # Agent internals
│   ├── prompt_builder.py     # System prompt assembly
│   ├── context_compressor.py # Auto context compression
│   ├── prompt_caching.py     # Anthropic prompt caching
│   ├── auxiliary_client.py   # Auxiliary LLM client (vision, summarization)
│   ├── model_metadata.py     # Model context lengths, token estimation
│   ├── display.py            # KawaiiSpinner, tool preview formatting
│   ├── skill_commands.py     # Skill slash commands (shared CLI/gateway)
│   └── trajectory.py         # Trajectory saving helpers
├── hermes_cli/           # CLI subcommands and setup
│   ├── main.py           # Entry point — all `hermes` subcommands
│   ├── config.py         # DEFAULT_CONFIG, OPTIONAL_ENV_VARS, migration
│   ├── commands.py       # Slash command definitions + SlashCommandCompleter
│   ├── callbacks.py      # Terminal callbacks (clarify, sudo, approval)
│   └── setup.py          # Interactive setup wizard
├── tools/                # Tool implementations (one file per tool)
│   ├── registry.py       # Central tool registry (schemas, handlers, dispatch)
│   ├── approval.py       # Dangerous command detection
│   ├── terminal_tool.py  # Terminal orchestration
│   ├── process_registry.py # Background process management
│   ├── file_tools.py     # File read/write/search/patch
│   ├── web_tools.py      # Firecrawl search/extract
│   ├── browser_tool.py   # Browserbase browser automation
│   ├── code_execution_tool.py # execute_code sandbox
│   ├── delegate_tool.py  # Subagent delegation
│   ├── mcp_tool.py       # MCP client (~1050 lines)
│   └── environments/     # Terminal backends (local, docker, ssh, modal, daytona, singularity)
├── gateway/              # Messaging platform gateway
│   ├── run.py            # Main loop, slash commands, message dispatch
│   ├── session.py        # SessionStore — conversation persistence
│   └── platforms/        # Adapters: telegram, discord, slack, whatsapp, homeassistant, signal
├── cron/                 # Scheduler (jobs.py, scheduler.py)
├── environments/         # RL training environments (Atropos)
├── tests/                # Pytest suite (~2500+ tests)
└── batch_runner.py       # Parallel batch processing

User config: ~/.hermes/config.yaml (settings), ~/.hermes/.env (API keys)

File Dependency Chain

tools/registry.py  (no deps — imported by all tool files)
       ↑
tools/*.py  (each calls registry.register() at import time)
       ↑
model_tools.py  (imports tools/registry + triggers tool discovery)
       ↑
run_agent.py, cli.py, batch_runner.py, environments/

---

AIAgent Class (run_agent.py)

class AIAgent:
    def __init__(self,
        model: str = "anthropic/claude-opus-4.6",
        max_iterations: int = 90,
        enabled_toolsets: list = None,
        disabled_toolsets: list = None,
        quiet_mode: bool = False,
        save_trajectories: bool = False,
        platform: str = None,           # "cli", "telegram", etc.
        session_id: str = None,
        skip_context_files: bool = False,
        skip_memory: bool = False,
        # ... plus provider, api_mode, callbacks, routing params
    ): ...

    def chat(self, message: str) -> str:
        """Simple interface — returns final response string."""

    def run_conversation(self, user_message: str, system_message: str = None,
                         conversation_history: list = None, task_id: str = None) -> dict:
        """Full interface — returns dict with final_response + messages."""

Agent Loop

The core loop is inside run_conversation() — entirely synchronous:

while api_call_count < self.max_iterations and self.iteration_budget.remaining > 0:
    response = client.chat.completions.create(model=model, messages=messages, tools=tool_schemas)
    if response.tool_calls:
        for tool_call in response.tool_calls:
            result = handle_function_call(tool_call.name, tool_call.args, task_id)
            messages.append(tool_result_message(result))
        api_call_count += 1
    else:
        return response.content

Messages follow OpenAI format: {"role": "system/user/assistant/tool", ...}. Reasoning content is stored in assistant_msg["reasoning"].

---

CLI Architecture (cli.py)

• Rich for banner/panels, prompt_toolkit for input with autocomplete
• KawaiiSpinner (agent/display.py) — animated faces during API calls, ┊ activity feed for tool results
• load_cli_config() in cli.py merges hardcoded defaults + user config YAML
• process_command() is a method on HermesCLI (not in commands.py)
• Skill slash commands: agent/skill_commands.py scans ~/.hermes/skills/, injects as user message (not system prompt) to preserve prompt caching

Adding CLI Commands

1. Add to COMMANDS dict in hermes_cli/commands.py
2. Add handler in HermesCLI.process_command() in cli.py
3. For persistent settings, use save_config_value() in cli.py

---

Adding New Tools

Requires changes in 3 files:

1. Create tools/your_tool.py:

import json, os
from tools.registry import registry

def check_requirements() -> bool:
    return bool(os.getenv("EXAMPLE_API_KEY"))

def example_tool(param: str, task_id: str = None) -> str:
    return json.dumps({"success": True, "data": "..."})

registry.register(
    name="example_tool",
    toolset="example",
    schema={"name": "example_tool", "description": "...", "parameters": {...}},
    handler=lambda args, **kw: example_tool(param=args.get("param", ""), task_id=kw.get("task_id")),
    check_fn=check_requirements,
    requires_env=["EXAMPLE_API_KEY"],
)

2. Add import in model_tools.py _discover_tools() list.

3. Add to toolsets.py — either _HERMES_CORE_TOOLS (all platforms) or a new toolset.

The registry handles schema collection, dispatch, availability checking, and error wrapping. All handlers MUST return a JSON string.

Agent-level tools (todo, memory): intercepted by run_agent.py before handle_function_call(). See todo_tool.py for the pattern.

---

Adding Configuration

config.yaml options:

1. Add to DEFAULT_CONFIG in hermes_cli/config.py
2. Bump _config_version (currently 5) to trigger migration for existing users

.env variables:

1. Add to OPTIONAL_ENV_VARS in hermes_cli/config.py with metadata:

"NEW_API_KEY": {
    "description": "What it's for",
    "prompt": "Display name",
    "url": "https://...",
    "password": True,
    "category": "tool",  # provider, tool, messaging, setting
},

Config loaders (two separate systems):

Loader	Used by	Location
load_cli_config()	CLI mode	cli.py
load_config()	hermes tools, hermes setup	hermes_cli/config.py
Direct YAML load	Gateway	gateway/run.py

---

Important Policies

Prompt Caching Must Not Break

Hermes-Agent ensures caching remains valid throughout a conversation. Do NOT implement changes that would:

• Alter past context mid-conversation
• Change toolsets mid-conversation
• Reload memories or rebuild system prompts mid-conversation

Cache-breaking forces dramatically higher costs. The ONLY time we alter context is during context compression.

Working Directory Behavior

• CLI: Uses current directory (. → os.getcwd())
• Messaging: Uses MESSAGING_CWD env var (default: home directory)

---

Known Pitfalls

DO NOT use simple_term_menu for interactive menus

Rendering bugs in tmux/iTerm2 — ghosting on scroll. Use curses (stdlib) instead. See hermes_cli/tools_config.py for the pattern.

DO NOT use \033[K (ANSI erase-to-EOL) in spinner/display code

Leaks as literal ?[K text under prompt_toolkit's patch_stdout. Use space-padding: f"\r{line}{' ' * pad}".

_last_resolved_tool_names is a process-global in model_tools.py

When subagents overwrite this global, execute_code calls after delegation may fail with missing tool imports. Known bug.

Tests must not write to ~/.hermes/

The _isolate_hermes_home autouse fixture in tests/conftest.py redirects HERMES_HOME to a temp dir. Never hardcode ~/.hermes/ paths in tests.

---

Testing

source .venv/bin/activate
python -m pytest tests/ -q          # Full suite (~2500 tests, ~2 min)
python -m pytest tests/test_model_tools.py -q   # Toolset resolution
python -m pytest tests/test_cli_init.py -q       # CLI config loading
python -m pytest tests/gateway/ -q               # Gateway tests
python -m pytest tests/tools/ -q                 # Tool-level tests

Always run the full suite before pushing changes.