Umbel

Umbel is a command-line tool that controls interactive agent CLIs in tmux sessions.

Umbel is a command-line tool designed for solo developers to automate work by driving interactive agent CLIs like Claude, Codex, Gemini, and OpenCode inside tmux sessions. It functions via a CLI, Model Context Protocol server, or declarative YAML workflow, allowing an agent session to spawn, send prompts to, wait for, and read outputs from multiple worker agents in parallel. The host maintains a clean context while workers handle the execution tasks. It uses native lifecycle events for completion detection and reads transcripts directly rather than relying on terminal scraping. Supported providers include Claude, Codex, Gemini, and OpenCode, with support for local models, free-tiers, and custom Anthropic-compatible endpoints.

Umbel at a glance

Best for: Software engineer
Runs on: macOS, Linux, CLI
Pricing: Free
Released: November 2026
Category: AI agent tool
Website: github.com/jahala/umbel

Key features

Spawn agent workers interactively
Run mixed-provider pipelines
Control workers via MCP server
Execute declarative YAML workflows
Detect completion via native events
Auto-route commands per session

Use it for

Orchestrate multiple AI coding agents in parallel
Automate tasks using existing vendor subscriptions
Run local models alongside subscription agents
Execute multi-step declarative workflows

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