How to Run 4-8 Parallel Coding Agents with tmux and Markdown Specs

Parallel AI Agent Development in Practice

Manuel Schipper has shared a months-long practical experience running parallel coding agents using a lightweight setup: tmux, Markdown files, bash aliases, and six slash commands. The post earned over 100 upvotes on Hacker News and sparked significant discussion about AI-assisted development workflows.

Three Agent Roles

Each tmux window is assigned a specific role:

Planner: Builds Markdown specs for new features or fixes

Worker: Implements from a finished spec

PM: Backlog grooming and idea management

Feature Design Files: The Core Mechanism

The foundation of the system is the Feature Design (FD) file — a structured Markdown document containing: the problem being solved, all solutions considered with pros and cons, the final solution with an implementation plan, files that need updating, and verification steps. Each FD is numbered and tracked through an 8-stage lifecycle from Planned to Complete.

Practical Limits

Beyond 8 concurrent agents, decision quality degrades. The /fd-init slash command bootstraps the full system into any repository. This workflow demonstrates how developers can leverage multiple AI agents in parallel without complex orchestration infrastructure — a valuable model as AI-assisted development becomes mainstream.