Ergon

An LLM chat interface built in Rust.

Features

• Models
  • Supports multiple LLMs
• Multi-modal
  • Text
  • Images
  • Audio
  • Files
• MCP
  • StreamableHTTP
  • STDIO
• Embedded models (TODO)
• Conversation management
• ACP (Agent Client Protocol)
  • Spawn external agents over stdio
  • Streaming text, thoughts, and tool calls
  • Filesystem read/write callbacks (sandboxed to a configurable workspace root)
  • Terminal create / output / kill / wait
  • Permission requests
  • Authentication (session/authenticate) with inline sign-in buttons
  • Slash commands (available_commands_update) rendered as a chip row
  • Plan rendering (plan updates) with status + priority glyphs
  • Session resume (session/load) via a "Resume last session" button
  • MCP passthrough — Ergon's configured MCP servers are forwarded to the agent (stdio always; streamable HTTP gated on the agent's mcp_capabilities.http)

Installation

cargo install ergon

MCP

Ergon can host MCP servers over stdio or StreamableHTTP. Configure them in Settings → MCP Servers:

• Name — used to identify the server in the chat-target picker.
• Type — stdio or Streamable HTTP.
• Command + args — how to spawn the server process (stdio servers only).
• Endpoint — the server's base URL (Streamable HTTP servers only).
• Auth — None, Bearer token, or OAuth2 (Streamable HTTP servers only).
• Scopes — OAuth2 scopes (Streamable HTTP servers with OAuth2 auth only).
• Redirect Port — port for receiving OAuth2 callbacks (Streamable HTTP servers with OAuth2 auth only).

ACP agents

Ergon can act as an ACP client and drive an external agent process (e.g. Claude Code, Gemini CLI, or your own implementation) over stdio. Configure agents in Settings → ACP Agents:

• Name — used to identify the agent in the chat-target picker.
• Command + args — how to spawn the agent process.
• Env — literal KEY=value, KEY=value pairs injected into the child.
• Workspace root — directory used for filesystem sandboxing and as the session's cwd. Defaults to Ergon's working directory.

Once at least one agent is configured, the chat header gains a target picker (LLM ↔ Agent). Selecting an agent spawns it (if not already running), performs the ACP initialize handshake, and creates or resumes a session.

Authentication

If an agent reports auth_required, Ergon renders a chat-bubble notice listing the advertised methods and shows a row of "Sign in: <Method>" buttons above the input. After authentication succeeds, session creation is retried automatically.

Session resume

When an agent advertises agent_capabilities.load_session, Ergon persists the most recent session id (and its workspace root) under acp_session_state in ~/.ergon/settings.json. A "Resume last session" button appears above the input whenever a stored session exists for the selected agent. Clicking it issues session/load; if the stored workspace root no longer matches, the resume is declined and a fresh session can be created.

MCP passthrough

Stdio MCP servers configured in Ergon are always forwarded to the agent. Streamable-HTTP MCP servers are forwarded only if the agent advertises agent_capabilities.mcp_capabilities.http. Bearer-token auth is converted to an Authorization: Bearer … header. OAuth2-authed servers are not forwarded (their tokens stay in Ergon).