Monospace Design TUI Standard

Package: mono-tui

This document defines the authoritative design rules for Monospace TUI-compliant terminal applications. It distills the research in the Foundational Research into falsifiable, auditable requirements. A companion Rendering Reference provides exact character codes, SGR sequences, and measurements. A Textual Appendix maps these rules to the Textual framework.

Monospace TUI explicitly supports aesthetic-first terminal applications — character user interfaces (CUIs) that treat the terminal as a high-fidelity visual medium rather than as a purely utilitarian text transport.¹

For reusable interaction strategies that cut across multiple archetypes, see the companion Pattern Library.

Conventions

The key words “MUST”, “MUST NOT”, “SHOULD”, “SHOULD NOT”, and “MAY” are to be interpreted as described in RFC 2119.

Falsifiability: Every rule in this document is written so that a reviewer can declare a specific implementation “compliant” or “in violation.” If a rule cannot be tested, it is not a rule.

Traceability: Rules cite their research basis in parentheses — e.g., (CUA §1.3) refers to monospace-design-tui-research.md §1 “IBM Common User Access,” (M3 §3.2) to §3 “Material Design 3,” etc.