xum

xum (maintained by Coder) is an open-source agent harness and orchestration framework built to manage, coordinate, and execute developer-focused AI agent sessions across local and cloud environments. xum structures agent execution around standardized tool configurations, custom skills, and environment context. It natively integrates Model Context Protocol (MCP) servers and LLM configurations (such as Claude), coordinating tool calls, background workflows, and editor extensions through dedicated workspace definitions. What distinguishes xum from standard interactive CLI chat tools is its focus on harness orchestration: it manages state persistence, session retry routines, compaction identity across restarts, and modular skill directories (`.agents/skills`) rather than functioning merely as a single-turn conversational interface. The project is open source and hosted publicly under Coder's GitHub repository, fitting into modern automated agent setups and developer workspace stacks.

Tags: agent harness, ai agent, cli, coding agent, developer tools, OpenSource

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Key features

• Model Context Protocol (MCP) Support — Loads and coordinates tools and resources via .mcp.json specifications. - Agent Skills Architecture — Supports modular, repository-defined capabilities located in .agents/skills. - Claude Configuration Compatibility — Natively ingests .claude workspace settings and prompt configurations. - Editor Integration — Provides tooling and extension bindings for VS Code-based developer workflows. - Session & Compaction Management — Handles context compaction identity and state recovery across automated retries. - Customizable Workflows — Supports scripted and declarative agent execution workflows across codebases.

Use cases

Use Case: Standardizing Workspace Agent Tooling A platform team defines repository-level tool definitions using .mcp.json and .agents/skills. Developers launch xum to execute agent tasks with a pre-configured, predictable set of development tools and security boundaries.

Use Case: Automated Multi-Step Coding Workflows A developer sets up complex workflow definitions to refactor legacy code, run benchmarks, and format test suites. xum orchestrates the execution pipeline while maintaining session state across tasks.

Use Case: VS Code Integrated Agent Execution An engineer runs orchestrated agent tasks directly within their VS Code workspace, utilizing xum's editor bindings to inspect agent actions and apply workspace patches directly.

Who it is for

Designed for developers, DevOps engineers, and teams building custom agent harnesses using the Model Context Protocol and structured agent skills. It is less suitable for users looking for a standalone, single-binary conversational chat tool without workspace configuration requirements.

Install guide

Installation Clone the repository and build from source using Node/npm package tooling: bash git clone https://github.com/coder/xum.git cd xum npm install npm run build

First Run Configure your environment variables and tool connections by copying the example environment file: bash cp .env.example .env # Add your model provider credentials (e.g., ANTHROPIC_API_KEY) to .env Verify that .mcp.json is configured with your desired MCP servers and tools.

Example Session Run the agent harness against your local workspace: bash xum start --mcp-config .mcp.json

Part of CLI Coding Agents

Categories: AI Coding Agents, Code Assistants, Developer Tools

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