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+# Mirror the 2.x CSS export surface in eds-tokens 3.0.0: one bundled `./css/variables` entry
+
+- **Status:** Proposed (accept after the bundle has been exercised on the
+  beta line — see validation plan below)
+- **Date:** 2026-07-20
+- **Decision makers:** Frida Erdal, EDS Core Team
+
+## Context
+
+[ADR-0009](./0009-temporary-next-subpaths-for-eds-tokens-beta.md) left one
+consequence open: what CSS export surface should eds-tokens 3.0.0 offer at
+the flip — the beta release that drops the legacy `build/` output and moves
+the Tokens Studio output onto the final specifiers?
+
+The Tokens Studio pipeline generates granular, attribute-scoped CSS files
+(`src/tokens/css/{colors,color-scheme,semantic,primitives,font,density}/*`,
+nine files, ≈ 44 kB unminified), currently published under the temporary
+`./next/css/*` wildcard. Legacy 2.x publishes exactly one CSS entry:
+`./css/variables` → `variables.min.css`, a bundle of everything. 2.x has
+no granular CSS exports at all — granular paths exist only for the data
+formats (`./json/*`, `./js/*`, `./ts/*`). No consumer has ever assembled
+EDS token CSS from parts.
+
+Facts verified against the repo (2026-07-20):
+
+- **Publishing granular files is an API commitment.** Export paths cannot
+  be removed or renamed without a breaking change. Publishing the nine
+  files freezes the internal file layout into public API while the token
+  architecture is still being reworked in Figma. Keeping them internal
+  preserves freedom to reorganize.
+- **Payload is not a differentiator.** Full nine-file bundle: 4.6 kB
+  minified + gzipped. The minimal subset (light-only, one density):
+  3.7 kB. Subset loading saves under 1 kB.
+- **Component consumers never see the specifiers.** `eds-core-react`'s
+  rollup build inlines the token CSS (postcss-import) into its shipped
+  `dist/**/index.css`. Only teams importing the tokens package directly
+  are affected.
+- **CSS variables fail silently.** A consumer who omits one required file
+  from a granular set (e.g. `color-scheme/light.css`) gets no error —
+  semantic tokens resolve to nothing and the UI renders unstyled. Several
+  import lines are several chances to get this wrong without a signal.
+- **The new output is attribute-mandatory, unlike 2.x.** The scheme
+  aliases exist only under `[data-color-scheme="light"|"dark"]`; without
+  the attribute nothing resolves — not even light mode. The 2.x bundle
+  works with no attribute (light values at `:root`, dark via explicit
+  attribute, plus a `prefers-color-scheme` media fallback appended by
+  `build-dark-scope` — added in #4864 to preserve the system-dark
+  behaviour that `light-dark()` had provided implicitly).
+
+## Decision Drivers
+
+- The one-import habit (`@import '@equinor/eds-tokens/css/variables'`) is
+  the only import pattern EDS consumers have ever had
+- Smallest possible public API surface: keep the generated file layout an
+  internal pipeline detail while the token architecture is in motion
+- No demand for granular CSS exists, and the measured payload gain of
+  subsetting is negligible
+- A semver major legitimizes changing the content behind a kept
+  specifier; consumers upgrading across a major expect breaking changes
+  and read the migration guide
+
+## Options Considered
+
+### Option A: Granular files only
+
+**Pros:** no bundle step; consumers load only the modes they use.
+
+**Cons:** every direct consumer needs six-plus `@import` lines and must
+learn which files are required versus opt-in, with silent failure as the
+error mode; breaks the only established import habit; freezes the internal
+file layout into public API; measured payload gain under 1 kB.
+
+### Option B: Granular files plus a bundled convenience entry
+
+**Pros:** one-import DX preserved; payload-sensitive consumers keep
+subsetting.
+
+**Cons:** still publishes the granular layout as permanent API (the real
+cost of A) for a benefit measured at under 1 kB; two documented ways to do
+the same thing.
+
+### Option C: One bundled entry, granular files stay internal (chosen)
+
+Mirror 2.x: publish a single generated bundle as `./css/variables`; the
+granular files remain committed pipeline artifacts that are not exported.
+
+**Pros:** identical consumer surface to 2.x (the variable *names* change,
+the *shape* of the package does not); internal file layout stays free to
+change; no subset footgun; shortest possible setup docs.
+
+**Cons:** consumers cannot skip unused modes (costs < 1 kB); a blind 2.x →
+3.0 upgrade keeps resolving the import and fails visually instead of at
+build time (mitigated: with every variable renamed, the unstyled result is
+unmissable, and the major-version migration guide is the intended path).
+
+## Decision
+
+**Option C.** eds-tokens 3.0.0 publishes one bundled CSS entry on the
+reused `./css/variables` specifier, mirroring the 2.x export surface. The
+granular files stay internal.
+
+- **Name reuse is deliberate.** ADR-0009's "path continuity is
+  misleading" argument applied to flipping specifiers mid-migration, where
+  unmigrated components would break silently on install. At a major
+  version boundary the same continuity is a feature: one import line, one
+  habit, content change signalled by the major bump and the migration
+  guide.
+- **Where the bundle is built:** a bundle step in
+  `tokens_studio_release.yaml`, committed as generated output alongside
+  the nine source files (inspectable in the release workflow's automated
+  PRs like everything else in `src/tokens/`). Concatenation is
+  conflict-free by construction — every mode file is attribute-scoped.
+  The step is a plain concatenation, deliberately not minified: the
+  committed bundle stays a pure function of the source files (no
+  minifier-version churn in release-PR diffs, no extra toolchain
+  dependency in the pipeline) and diffs stay reviewable. Gzip closes
+  the size gap (4.8 vs 4.6 kB); consumers that bundle minify with
+  their own tooling. The bundle's only added behaviour is the
+  `@layer eds-tokens` wrap decided in
+  [ADR-0014](./0014-token-code-output-architecture.md) (proposed in
+  [#5178](https://github.com/equinor/design-system/pull/5178), decision
+  point 6; not yet implemented — the shipped bundle is unlayered until
+  then). The wrap is deterministic, so the bundle stays a pure function
+  of the source files; beyond it the step adds nothing on top of the
+  generated files (see the colour-scheme note below).
+- **Beta validation costs nothing extra:** the existing `./next/css/*`
+  wildcard maps to `src/tokens/css/*`, so the committed bundle is
+  importable as `@equinor/eds-tokens/next/css/variables.css` in the next
+  beta with no publish-workflow change. The temporary `next/*` paths
+  (including the granular files) disappear at the flip as ADR-0009 already
+  prescribes.
+
+### Colour-scheme behaviour: governed by ADR-0004, not by 2.x
+
+The bundle keeps the generated output's attribute-scoped behaviour as-is:
+consumers set `data-color-scheme` once at root level, per the theming
+convention decided in
+[ADR-0004](./0004-component-conventions-for-eds-2.md). There is no
+`prefers-color-scheme` media fallback in 3.0. 2.x behaves differently
+(light at `:root`, automatic system-dark via a media fallback), but that
+behaviour is inherited from `light-dark()` in the original 2024 build
+setup (#3447) and a bug-fix rewrite that preserved its semantics (#4864),
+not from a design decision — it does not carry over. Apps that want to
+follow the OS make that choice themselves by setting the attribute (e.g.
+from a `matchMedia` listener); the design system provides the switch, the
+app decides the policy.
+
+### Open question (must be settled before Accepted)
+
+- **Whether anything beyond colour needs mode files bundled** as the
+  token architecture rework lands (density set may change shape).
+
+### Validation plan
+
+1. Add the concat step; the bundle ships in the next beta as
+   `next/css/variables.css`
+2. Use it in the `/next` component migration and let beta testers exercise
+   it
+3. Settle the open questions; at the flip, map `./css/variables` to the
+   bundle per ADR-0009's exit plan
+4. Mark this ADR Accepted when at least one beta has exposed the exact
+   3.0.0 surface
+
+### Consequences
+
+- Good, because 2.x consumers keep their single import line through the
+  major upgrade; only variable names migrate
+- Good, because the granular file layout stays changeable while designers
+  rework the token architecture
+- Good, because the bundle is validated on the beta line before the flip,
+  matching ADR-0009's exit plan
+- Bad, because the pipeline gains a small generated artifact whose build
+  step must follow future changes to the export set (mitigated: the step
+  should glob `src/tokens/css/`, not hard-code file names)
+- Bad, because 2.x's automatic system-dark does not carry over: apps that
+  relied on it must set `data-color-scheme` themselves — the migration
+  guide must call this out explicitly
+
+## Related
+
+- [ADR-0009](./0009-temporary-next-subpaths-for-eds-tokens-beta.md) — the
+  open consequence this ADR settles
+- [ADR-0004](./0004-component-conventions-for-eds-2.md) — the theming
+  convention (`data-color-scheme` set once at root by the consumer) that
+  governs the bundle's colour-scheme behaviour
+- [ADR-0013](./0013-attribute-scoped-custom-properties-not-light-dark.md)
+  — why the token CSS uses attribute-scoped rules and never
+  `light-dark()`
+- [ADR-0014](./0014-token-code-output-architecture.md) (proposed in
+  [#5178](https://github.com/equinor/design-system/pull/5178)) — the
+  output architecture; decides the `@layer eds-tokens` wrap this
+  bundle step applies
+- PR [#4864](https://github.com/equinor/design-system/pull/4864) — why the
+  2.x bundle has explicit dark scopes + the `prefers-color-scheme`
+  fallback (`build-dark-scope`)
+- `.github/workflows/tokens_studio_release.yaml` — where the concat step
+  will live
+- Epic [#4740](https://github.com/equinor/design-system/issues/4740);
+  issue [#5108](https://github.com/equinor/design-system/issues/5108)