gstack/docs/design-lint.md

design-lint: the free, deterministic design check

bin/gstack-design-lint reads a page (or a directory of pages, stylesheets and components) and prints every machine-checkable design tell it finds, with a file and line, in under a second. With --render it also measures the page in gstack's own browser: the fold, the word budget per screen, contrast against the painted pixels, focus rings by tabbing, crowded headings, text painted under other elements, the share of the page that is photographs. Nothing is installed and nothing is paid for: the static tier is TypeScript over the files, and the render tier drives the same engine gstack-render picks (Aside when it is running, otherwise the browse daemon ./setup built).

The rules are ported from Nutlope/hallmark's sloplint (MIT; see NOTICE.md and licenses/MIT-hallmark.txt), rewritten in gstack's voice and mapped onto gstack's severity words. The copy tier is the content-realism and ship-floor check adapted from Elaya's design skills (MIT; see NOTICE.md), each tell at its line. /design-html runs the lint on every finalized page and /design-review on each audited page.

Usage

gstack-design-lint <file-or-dir ...> [--render] [--url <http://…>] [--scope page|component] [--job <job>] [--json] [--rules]
gstack-design-lint --scope app (--url <http://…> ... | --state-file <states.json>) --within <selector> [--viewport WxH ...] [--wait-for <selector>] [--waivers <file>] [--json] [--verbose]

The second form is the render-only app profile; see App profile.

• Reads .html, .css, .jsx, .tsx, .vue, .svelte and .astro. Tailwind class strings in components are read too, including cn(), clsx(), cva() and their kin. node_modules, dot folders and build output below the top level are skipped; a symlink is followed once and lint roots and the working directory are read through their real paths; a file over 2 MB is a bundle, not a page, and is skipped with a warning on stderr. A page or stylesheet the lint skipped (over the cap, unreadable, unparseable; a linked sheet or an inline <style> block included) is also one internal-error finding at ask, so a page whose CSS the lint could not read is not a pass; only a linked stylesheet that does not exist is warned about and otherwise ignored (its tokens are simply absent). A relative stylesheet href may not climb out of the project (the nearest directory holding a package.json or .git), by its path and by its real path, so a symlink inside the project that points outside it is not read either; outside any project it is bounded by the working directory the lint runs in, and only .css files are read.
• Markup inside an HTML comment is dead for every rule, a commented-out <style> or <script> included; a comment that never closes runs to the end of the file, as it does in the browser. A tag start with no > (a stray <img ) and any < that starts no tag (<1, a < b) are read as text and dropped from the markup, so a page whose tail is ten thousand of them costs its length; a <!doctype> or <?xml?> declaration stays. A tree nests at most 512 elements deep (the browser's own cap); a start tag deeper than that is read as empty. An open heading is closed by the next heading start tag, an open <p> by the next block start, and a repeated <li>, <button>, <a>, <label>, <select>, <form> or table cell by its next start tag, as the browser does, so a page of unclosed elements costs its length to lint. A nested CSS selector is expanded against its parent (& replaced, a bare selector descendant-joined) up to 8192 characters, and a sheet may store at most four times its length plus 64 KB of expanded selectors; past either bound the nested selector stands as written, so a sheet costs its length too. Nesting is read 64 levels deep; a rule nested below that is dropped, not parsed.
• A page is linted with the stylesheets it links (<link rel=stylesheet>, @import, and anything they reach); a directory of components shares the project's tokens and global state styles, so a focus ring declared once in globals.css is not reported missing on every component.
• --render measures every HTML page found; --url measures a running dev server (and implies --render). When no browser is available the render tier is skipped and the summary says why. With --url, under any scope, a skipped render also prints gstack-design-lint: RENDER_UNAVAILABLE: nothing was measured at <url> (<reason>) | fix: gstack-browser-ensure, then rerun on stderr and exits 4: a URL nobody measured is never a pass. --render over files without a browser keeps the skip and its exit code.
• --scope component skips the page-only rules (the nav, the footer, the eyebrow, section gaps, the wireframe count) when linting a component alone.
• --job <job> names what the visitor came to do (book, buy, subscribe, attend, visit, hire, listen, join, try, sign up): an email sign-up as the page's close is only a finding when the job is not one where a mailing list is native.
• --json prints { summary, files, findings }; --rules prints the table below.

Output

One line per finding, then one summary line:

LINT: <blocks|ask|polish|waived> <rule-id> <file>:<line> <evidence> | fix: <fix>
LINT_SUMMARY: blocks=N ask=N waived=N polish=N render=<ran|skipped: reason>

Page-supplied text in a finding never holds the line's own | fix: separator (it is printed as / fix:), so splitting a line on its first | fix: always reads the fix; a program reading many fields should take --json.

Exit 2 when anything blocks, 1 when an ask is unanswered, 0 otherwise (3 on a usage error, 4 when --url was given and no browser measured it). Findings sort blocks, ask, waived, polish, then by rule, file and line. --scope app has its own verdict and exit codes: see App profile.

Tiers

The lint uses gstack's severity words, not a fourth scale:

Tier	Meaning	hallmark's word
blocks	Never waivable. Correctness, access, honesty and the bans: a card in a card, a purple-blue gradient, a missing focus ring, contrast under threshold, a reveal that hides content until JavaScript runs.	Floor
ask	A default a model falls into. Fix it, or waive it on the record with a reason about this page.	Reflex
polish	Craft detail invisible at arm's length. Printed, never blocks.	Finish

waived marks an ask or polish finding a waiver answered. Blocking and waived are never summed: blocks=0 is always a true sentence about the Floor. Three house rules hallmark holds at Floor stay at ask here on purpose: the eyebrow (kicker-above-heading; a figure caption or a plan name above a heading is often right), the 80-word screen (screen-word-budget; a Read-mode page legitimately exceeds it) and the dash (em-dash-overuse; gstack's rule is overuse, not a ban). A blocking rule the lint can only suspect (an invented metric it cannot prove invented) reports at ask so a person confirms it.

Waivers

A finding is answered in a comment that names the rule and gives a reason about this page:

<!-- gstack-lint-disable kicker-above-heading: the chapter number is the reader's bookmark through a forty-page spec -->

/* gstack-lint-disable section-gap: the ledger separates its rows with rules, not air */

// gstack-lint-disable template-nav: the three links are the product's three modes

impeccable-disable <rule>: <reason> is accepted as an alias, so a comment that already silences the impeccable engine answers the same tell here. The lint refuses, each as its own waiver finding at ask: a rule it does not know; the lint's own rules (render, waiver, house-style, internal-error: a fallback face or a failed measurement is never signed off); a blocking rule (the Floor is never waivable; the one exception is a blocking rule the lint could only suspect on this page, which it reports at ask and which a waiver answers like any ask); a reason under 24 characters, boilerplate ("by design", "intentional", "looks better"), reused word for word on another waiver, or sharing no word of four letters or more with the page's own text; a second waiver of one rule. More than three waivers on one page is a house style and belongs in DESIGN.md: reported once at polish as house-style.

A claim written in a stylesheet answers for that stylesheet on every page that links it, and only for findings located in it: the shared-word check does not apply (a stylesheet has no prose), so the claim cannot reach a finding in the page's own markup. A claim written in the page answers for that page, including a finding in a stylesheet it links; a second page linking the same sheet without answering still reports it, so the sheet's finding may print once waived and once at ask, each from its own page. Which of these a context gets follows its shape, not the --scope flag: one html page keeps page semantics under either scope. In a directory of components, or a lone component file beside a stylesheet (under either scope), each file's claim answers for that file alone, weighed against that file's own text and its own suspected rules, so a sibling component is never covered and a sibling that measures a blocking rule does not turn this file's suspected finding into the Floor; a stylesheet beside the components answers for itself as on a page. Two claims on one line are both read. A blocking copy tell (generic-hero-copy) is the Floor inside the hero, the section or header that holds the h1; the same line, or a "Meet " or three-word triad heading, in body copy further down is suspected and reported at ask, so a waiver can answer it.

Rules

Rule	Tier	Source gate	The tell	The fix
purple-blue-gradient	blocks	2a	purple-to-blue, purple-to-pink or cyan-on-dark gradient	one anchor hue and solid ink
gradient-text	ask	2b	gradient text	solid ink; carry emphasis with weight or a display face
pure-black-white	blocks	7a	#000 or #fff as a colour outside the token block	tint toward the anchor hue: chroma 0.005 or more
absolute-surface-token	ask	7b	a surface token that resolves to pure black or white	tint the paper
zero-chroma-neutrals	ask	22	zero-chroma oklch() neutrals	give the neutrals chroma 0.005 or more
accent-footprint	ask	23	accent colour past about 5% of a viewport	retreat the accent to actions and one signal
glow-wash	ask	29	glow and wash: blurred orbs, a radial halo or a zero-offset coloured glow	a solid or grained surface; elevation by lightness, shadows with offset and blur
cream-palette	ask	65	the cream paper, serif display and terracotta accent look	move one axis: the accent first, the paper second, the display last
framework-palette	ask	74	a framework default palette (Tailwind indigo-500, slate-900 and kin) as a token or utility	a colour mixed for the page in OKLCH
overused-font	ask	1	a training-data display face (Inter, Roboto, Fraunces, Playfair Display, Space Grotesk and the rest of gstack's catalog) or a system stack as the display	a display face chosen for the page
banned-font	ask	catalog	a face gstack bans in any role (Papyrus, Comic Sans, Impact, Lobster, Raleway, Courier New and the rest of lib/design-catalog.ts BANNED_FONTS)	a face chosen for the page; the body face for body and labels
line-length	ask	25	running prose outside 45 to 75 characters a line	max-width: 65ch
font-family-count	ask	37	more than three font families	display, body and one outlier
italic-word-in-heading	blocks	38i	one italic word inside an otherwise roman heading	a line break, or the whole head set one way
italic-serif-display	ask	38ii	an italic display system	roman display, or declare it on --font-display with font-synthesis: none
accented-word	ask	38iii	one word in a heading set apart by colour, weight, a highlight or an underline	the whole head one way; a line break; a second line at a second size
caps-leading	blocks	55a	an uppercase display head that can wrap with line-height under 1.0	line-height 1.0 at least (1.02 to 1.08 recommended)
caps-lockup-leading	ask	55b	a single-line caps lockup under 1.02	line-height 1.02, or make sure it cannot wrap at 320px
monospace-costume	ask	64	monospace on labels, captions or small type when the content is not code	labels in the body face, a step smaller, normal case
tiny-text	ask	75	running text under 12px, functional text under 11px, or prose leaded under 1.3 (render)	body 16px at 1.5 to 1.65; labels one step smaller
wide-tracking	blocks	67	the tracked-caps label: small text set uppercase or letter-spaced past 0.03em	the body face, a step smaller, sentence case, untracked
template-cards	ask	3	three equal icon-above-heading tiles, an icon in a rounded tile, or a thick coloured side stripe	vary widths and heights, inline icons, hairline or no border
nested-cards	blocks	4	a card inside a card	one containment layer
vh-height	blocks	6a	a hero sized in vh	dvh or svh
raw-spacing	blocks	24a	a raw padding, margin or gap length where a --space-* token exists	the token
off-scale-spacing	ask	24b	spacing off the page's scale	the scale; three optical nudges at most
overflow-x-unclipped	ask	34	overflow-x missing on html and body, or a 100vw width	overflow-x: clip on both; width: 100%
horizontal-scroll	blocks	34	horizontal scroll at a width between 320 and 1920 (render)	find the element wider than its viewport and cap it
hero-balance	ask	44a/44c	the hero's content sits off centre for its screen, or its visual stands apart from the text (render)	centre the content in its screen; put the visual beside the text
hero-fold	blocks	44b	the headline's bottom or the hero's first action below the 800px fold at 1280 wide; the lede and the visual are not measured (render)	pull the display clamp down, tighten leading, a two-line lede, trim padding
wide-container	blocks	44d	at 1920x1080 the container has no max-width, gutters under 120px, or a grid gains columns	cap 1360 to 1520px and centre; hold column counts; cap vw visuals
bare-fr-track	blocks	50	an image-bearing grid track on bare 1fr	minmax(0, 1fr)
display-head-unwrapped	blocks	50	a display head without overflow-wrap: break-word and min-width: 0	overflow-wrap: break-word; min-width: 0 (never anywhere)
radio-tab-jump	blocks	53	CSS-only radio tabs at position: absolute; top: 0 with no JS guard	radios in flow at zero size, or a handler with preventScroll
double-sticky	blocks	56	two position: sticky; top: 0 elements	top: var(--banner-height) on the second
screen-word-budget	ask	58	more than about 80 words in one 900px window, or a hero with more than two text blocks before its actions	headline, one sentence, actions; a section is a head block, then its composition
section-gap	ask	59	a gap under 120px between sections at 1440, every gap the same, or more than nine sections (render)	120px at least, varied; six to nine sections a page
heading-rhythm	ask	71	a heading nearer what precedes it than what it heads (render)	at least twice the space above a head as below it
cramped-padding	ask	72	text closer than 8px (or half an em) to the side of its filled box (render)	pad the box; a 16px gutter
thin-section	ask	77	a section below the hero with no mass: a narrow body on a wide canvas (render)	widen the body, add a visual, set a statement, or merge the section
small-section-heads	ask	78	the median h2 below the hero renders under 40px at 1440 (render)	h2 at the section size, item titles at the title size
dead-band	ask	79	more than 160px of nothing between the hero's lowest content and the fold (render)	centre the content and grow the visual or the head; never fill with copy
hand-drawn-svg	ask	80	an inline SVG of 120px or more with three curves or fills and no text: a drawn illustration (render)	a photograph, the product built, or type at scale
empty-picture	ask	81	a slot or gradient block of 300x200px or more showing nothing but its wash (render)	the user's image, a credited photograph, or the product at full fidelity
counting-marks	ask	82	24 or more identical marks standing for a quantity (render)	set the number in type
photo-wall	ask	83	photographs cover more than a third of the page below the hero (render)	keep the strongest pictures, set big; carry the rest in type, figures, the product, a table
email-band-close	ask	85	the page ends on an email sign-up form (one or two fields, one of them the email; never a form with a password or a sign-in button) on a page whose job is not subscribe, join, attend, listen or visit	end on what the visitor came to do, or on the last strong section
aphoristic-cadence	blocks	19	the rebuttal cadence three or more times ("Not a feature. A platform.")	say what the product does, in its own nouns
generic-hero-copy	blocks	19	a filler opener ("Built for the modern team", "In today's landscape"), "quietly trusted by", or the catalog's "Welcome to" and "all-in-one solution"	say what the product does, in its own nouns
generic-cta-copy	ask	19/42	a stock second action beside the primary (Learn more, Get started, Book a demo)	one action, or a second that names where it goes
em-dash-overuse	ask	19	em or en dashes carrying the prose	a comma, a colon, a full stop or a line break
template-footer-line	ask	19	a stock footer line (All rights reserved)	the page's own line, or nothing
template-nav	ask	42	the reflex nav: wordmark left, inline links, a button right, hairline under	decide the nav and build another shape, or keep it on the record
template-footer	ask	42	the reflex footer: four link columns, a social row, a copyright	decide the footer and build another shape, or keep it on the record
invented-proof	blocks	46a	an invented metric, testimonial, logo wall or case-study count	the user's number, a text slot, or nothing
drawn-browser-chrome	blocks	47a	a hand-drawn browser bar (traffic lights, URL pill) or OS window title bar	a real screenshot in a , or no chrome
device-frame	ask	47b	a phone, laptop, terminal or editor frame	one frame with real content inside, or none
imitation-material	ask	47c	styled divs standing in for a product, a photo edge or a physical object	the product built inside a slot, a real asset, or nothing
kicker-above-heading	ask	54	the eyebrow: short inert type before a heading that only announces it	open the section another way; where the heading is figurative, the label becomes the heading
template-punctuation	blocks	63	template punctuation: middle-dot meta strings, an arrow glued to link text, decorative status dots	line breaks, columns, hairlines; a verb as the label
wireframe-slots	ask	68	more than five empty slots on one page, or four or more in one row	set the set in type; a slot that stays holds a real photo or the product
repeated-fact	ask	69	one fact (a price, a time, a count) printed in four or more sections	say each fact once, where it does work
fake-send	blocks	70	a form that prints success with no request behind it	validate, post nowhere and say so plainly until the endpoint exists
layout-transition	blocks	10a	transition: all, or animating width, height, top or left	list the properties; transform and opacity
spacing-transition	ask	10b	transitioning margin or padding	transform
hover-tells	ask	11	the same lift on every card, two effects on one element, an image scaling on hover, or a hover on something inert	one signal per element, on the container, not the image
bounce-easing	ask	12	bounce or overshoot easing on UI state	an exponential ease-out
focus-ring-fade	blocks	15	a focus ring that fades in	instant: exclude outline and box-shadow from the transition
tooltip-focus-delay	blocks	17	a tooltip whose focus delay equals its hover delay	hover 800 to 1000ms, focus 0
autorotate-no-pause	blocks	18	auto-rotating content with no pause on hover and focus	pause on hover and focus; a visible pause control past 5 seconds
missing-focus-visible	blocks	26a	an interactive element with no :focus-visible ring, or an outline removed with nothing in its place	a ring at 3:1 or better, instant
missing-states	ask	26b	no :active or :disabled state	all the states a control can be in
missing-reduced-motion	blocks	27	a keyframe or transform transition without a prefers-reduced-motion fallback	add @media (prefers-reduced-motion: reduce)
autoplay-unmuted	blocks	28a	a video autoplaying without muted	autoplay muted loop playsinline
lazy-lcp	blocks	28a	loading="lazy" on the first image or the hero video	fetchpriority="high" on the LCP image
video-without-poster	ask	28b	a video without poster or a priority hint	add them
input-state-shift	blocks	39a	input states that break: a border that changes width, a focus ring built from border, disabled by opacity alone	constant border, outline, shared height, three disabled channels
control-height	ask	39b	control height outside 44 to 52px on a marketing page	the number
content-hidden-at-rest	blocks	62	a reveal class hiding content until JavaScript runs	visible by default; hide only under a .js class, or animate from visible with @starting-style
emoji-decoration	blocks	30a	an emoji standing in for an icon	one icon library, custom SVG, or typography
two-icon-libraries	ask	30b	two icon libraries on one page	one library
unlabeled-decoration	blocks	33	a decorative	hide it or name it
broken-image	blocks	76	an with no source or one that does not load	the real file
stock-photo-hotlink	blocks	76	a stock-site photo hotlink	the user's image, or a library photograph credited on the page
text-occlusion	blocks	73	text painted under another element (render)	give the text its own space, or its own surface above the cover
low-contrast	blocks	40	text, an icon, a focus ring or a field edge under its contrast threshold	fix the pair; body 4.5:1, large text and edges 3:1
gray-on-color	blocks	41	button text within a step of its fill, or grey text on a coloured surface	the paired ink token
literal-outside-tokens	blocks	48	a colour or font-family literal outside the token block	lift it into the tokens
button-label-wraps	blocks	49a	a button label or primary nav link that wraps	shorten it; white-space: nowrap
link-wraps	ask	49b	a footer link, tab or breadcrumb that wraps	shorten it
straight-quotes	polish	F1	straight quotes in prose	curly quotes
three-dot-ellipsis	polish	F2	three dots for an ellipsis	the ellipsis character
balanced-display-head	polish	F3	a display head without text-wrap: balance	text-wrap: balance
two-primary-buttons	polish	F4	two filled primary buttons on one page, or side by side	one filled primary; the second as a text or outline action
icon-coin	polish	F5	an icon in a coloured coin	the icon inline, bare
display-figures-tabular	polish	F6	display-size figures without tabular numerals	font-variant-numeric: tabular-nums
stamped-recipe	polish	F7	one container recipe stamped on six or more selectors, or the pill radius on five or more non-controls	vary the recipe; pills on controls, tags and badges only
scroll-choreography-mix	polish	F8	more than one scroll-choreography pattern	one pattern a page
fake-avatar	blocks	F9	a fake-human avatar hotlink	the user's people, initials, or no portrait
stock-person-photo	polish	F9	a person-keyword stock photo URL	the user's photograph
page-invariants	polish	F15	page invariants broken: primary button style, container width, column gap or radius drifting	one recipe for each
unthemed-browser-surfaces	polish	F16	no ::selection, caret-color or scrollbar-color on a page with a committed palette	theme the browser surfaces
text-sliver	polish	F17	a text block squeezed into a sliver at 1440 (render)	give the block room or merge the columns
tiny-slot	polish	F18	a slot rendering under 40px in either dimension (render)	size the slot for what it will hold
font-weight-count	polish	F19	more than three font weights in running use (render)	three weights
lonely-grid-item	polish	F20	a grid or wrapping row leaving one item alone on its last row (render)	change the count or the columns
skipped-heading	polish	F21	a heading level skipped	step the levels one at a time
justified-text	polish	F22	justified text without hyphens: auto	hyphens: auto, or left-aligned
missing-lang	polish	F23	a document without lang	lang on <html>
hairline-under-shadow	polish	F24	a hairline border under a wide soft shadow on one surface	the shadow or the border, not both
placeholder-name	ask	craft	a placeholder name (John Doe)	use a supplied name, or one that fits the product in sample data
placeholder-brand	ask	craft	a placeholder brand (Acme, Nexus)	use a supplied customer, or a fitting name in sample data
lorem	ask	craft	lorem ipsum placeholder text	write real copy
marketing-buzzword	ask	craft	a marketing buzzword	say the specific thing
round-number	ask	craft	a round invented number	use the supplied figure, or drop the claim
needs-proof	ask	craft	a [Needs proof] marker left in the page	supply the proof or remove the claim before publishing
oops	ask	craft	"oops" as an error message	say what happened and what to do
scroll-listener	ask	craft	a scroll event listener	use IntersectionObserver; read scroll inside requestAnimationFrame for a scroll-linked effect
dead-link	ask	craft	a dead link (href="#")	link it, or render the control disabled
alert	ask	craft	alert() for a message	show the message inline
img-no-alt	blocks	craft	an without alt	add alt text (alt="" when decorative)
missing-title	blocks	craft	a document without a