tai/research/tui-framework-design/textual-constants-theme-env.md

Textual constants.py — TEXTUAL_THEME environment default

Metadata

Field	Value
Institute	Molodetz Institute — Research & Retrieval Division
Subject	tui-framework-design
Document type	Source Dossier
Tier	1
Source title	Textual src/textual/constants.py — TEXTUAL_THEME env handling
Source URL	https://raw.githubusercontent.com/Textualize/textual/main/src/textual/constants.py
Source publisher / author	Textualize (Textual project)
Source type	repository
Source date (published)	Unknown — not stated
Date researched	2026-10-11
Researched by	tai (agent), model: Muse Spark, on behalf of retoor
Research method	direct page fetch
Confidence	Medium
Status	Active

Summary

A thin source with one finding: the TEXTUAL_THEME environment variable sets the default theme, taking a first-existing-wins list. It exists here as the precedent for tai's TAI_THEME variable.

Key findings

• TEXTUAL_THEME sets the default theme from the environment, accepting a list where the first existing theme wins.

Pros / strengths

• Env-var default with first-existing-wins fallback is a small, robust precedence mechanism worth copying exactly.

Cons / limitations / caveats

• Thin source: one mechanism only, no interaction with flags or runtime switching visible here.

Relevance to tai

• Direct precedent for the palette-role conclusion's precedence chain (flag > TAI_THEME env var > default).

Changelog

Date	Change
2026-10-11	Initial dossier created from 2026-10-11 research-pass evidence (body opened via web_fetch by researching agent).