principle. appearance lives in one home. appearance scattered per app is how a suite stops looking like one thing; the dials below live once, at suite level, and every surface inherits them.

rule — the appearance layer (law; decision 0022). appearance settings live once, at suite level, and every surface inherits them:

• the theme lane and variant (see Themes & the dynamic base);
• material strength (translucency, within the chapter’s declared range);
• motion comfort (full, reduced, off);
• the density backup dial (auto-scale first; the dial is a backup, never the mechanism usability depends on).

per-app overrides exist only where lean (zero idle cost, authored default unchanged); an app may never invent a private appearance variable. the option set is finite and authored: configurability in Distira means choosing among designed readings, never editing the grammar itself.

The findings in this section are candidates on the record, from the settings-substrate study; they amend the settings presentation only, and any conflict with a ratified decision resolves in favour of the decision log until a verdict says otherwise.

• Mode axis on top. appearance is mode first (night / day / follow), flavour second. adaptive (decision 0019) is the follow setting of this axis, not a separate feature. porcelain is the default authored day reading and oled the default authored night reading — mode readings, not lane entries — so the settings list is mode × flavour (dynamic scheme, authored palette, ported theme). in day mode the dynamic machinery still applies at paper strength: the governing hue reads as print on paper, so hue and shade controls stay live in both modes.
• Role-stepped scales. a hue is consumed as a scale of steps, each step pre-assigned a role (backgrounds, interactive fills, borders, solid accents, text). a picker scrubs steps and settles on the designed step, never a free value. hue selection takes the form of one scrubbable strip settling on designed hues, not a grid of buttons.
• Variant distinguishability rule. a scheme variant must be identifiable at a glance in its own preview and on a live surface; two variants that cannot be told apart are one variant. soft earns its slot only with a decisive delta: chroma cut plus contrast register compressed, surfaces pulled toward stone.
• Tertiary roles. beyond the governing hue, two subordinate roles may take their own hue: detail (fine elements: gauge edge, chip ring, focus ring) and ambient (secondary light: glows, window tints). both default to the governing hue; the one-hue law binds per role, not per surface. pickers for these roles are compact and visually subordinate.
• No live-looking dead controls. a control that cannot affect the current mode visibly retires (dimmed, disabled, one quiet line of explanation) rather than presenting as available. dead controls that look alive are worse than absent controls.
• Folding and prominence. prominence is priced by frequency of touch: what the hand reaches for constantly stays visible; what it touches rarely folds away, however powerful it is. the always-visible layer is one compact bar carrying the two highest-frequency decisions — the mode axis and the governing hue. the family variants, shade steps, and the detail and ambient role pickers fold behind a single tuning disclosure that opens in place: the surface grows downward, nothing is exiled to another page, and the live specimen preview stays visible at both states. a control and the fold must never compete for the same decision; each decision appears exactly once, at the prominence its touch frequency earns.
• Picker hue order is spectral. picker strips order hues by spectrum (ember, clay, brass, sage, lagoon, slate, violet, mauve), because users locate a hue by its rainbow position, not by any internal document order. stone, the non-hue, parks last. the token file’s authored order is a display order — correct for bands, charts, and any place the ramp is shown as a set — and it is never the picker order. both orders settle only on designed steps.

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Canonical text: §14, the appearance layer, in the design language document. Governed by decision 0022; candidates from docs/patterns/candidates-settings-substrate.md.