sandbox bg preset (transform-resolved)SPEC-104 §5: make a reusable sandbox backdrop applicable by name (bg="midnight-waves") like any other preset, by adding a sandbox descriptor to BgPresetDefinition — resolved at transform time (not the identity engine, which has no file access), expanding into the WORK-428 data-bg-guest body.
Tracking started Jun 15 — check back for trends.
BgPresetDefinition (packages/transform/src/types.ts) gains sandbox?: { src: string; framework?: string; dependencies?: string }, a sibling to the engine-resolved gradient/style.bg="name", finds a sandbox-typed preset, and injects the real {% sandbox %} guest into the bg body — producing the same data-bg-guest element WORK-428 relocates. The preset is sugar over the body primitive, not a parallel path.height: fill, presentational posture, eager activation come from the bg-guest mechanism; the preset describes only the scene (src/framework/dependencies). A preset may also carry gradient/style for the boot frame (both land in the same data-name="bg" div); extends resolves as for other bg presets.refrakt.config.json sites.<site>.backgrounds) per the SPEC-088 project-vs-theme split (a scene is content); project backgrounds merge over theme. refrakt.config.schema.json gains the sandbox key.BgPresetDefinition gains a sandbox descriptor (src/framework/dependencies); refrakt.config.schema.json documents it; project backgrounds merge over theme.sandbox-typed preset is resolved at transform time by an expansion step that injects the WORK-428 body guest — not in the identity engine; bg="name" reaches author-parity with a gradient preset.gradient/style (boot frame); extends resolves as for other bg presets; forced fill/posture/eager are not author-set.data-bg-guest body contract.packages/transform/src/types.ts (BgPresetDefinition) · refrakt.config.json / refrakt.config.schema.json · SPEC-088 (project-vs-theme preset home) · packages/runes/src/tags/sandbox.ts (the rune the expander instantiates).Completed: 2026-06-16
Branch: claude/v024-work429-bg-preset.
packages/transform/src/types.ts): BgPresetDefinition gains sandbox?: { src; framework?; dependencies? }, a sibling to the engine-resolved gradient/style.packages/runes/src/lib/index.ts, injectBgMetasFrom): when bg="name" resolves to a sandbox-typed preset in config.variables.__backgrounds, a synthesised {% sandbox %} is transformed (the real rune runs, with file resolution + sanitisation via the config readers), tagged data-bg-guest + data-guest-posture="backdrop" + height="fill" + eager, and hoisted — the same element WORK-428's engine relocates. The preset is sugar over the body; an inline body guest wins if both are present. extends resolves one level (own fields win), mirroring the engine's preset chain.packages/content/src/site.ts): the project bg registry (siteConfig.backgrounds) is passed into the Markdoc transform variables as __backgrounds, so the expander can resolve preset names at transform time (where the sandbox readers live).refrakt.config.schema.json): the backgrounds property documents the BgPresetDefinition shape incl. the sandbox key (kept freeform-validated).backgrounds registry + descriptor (one registry reference per build, shared across pages → cross-page dedup; the file-reading transform runs once, each consumer gets a fresh clone).packages/runes/test/bg-preset.test.ts, 4): expansion → tagged backdrop guest; non-sandbox (gradient) preset doesn't expand; extends resolution; memoisation (readers run once across two consumers).bg="name" also emits the bg-preset meta, so the engine paints the preset's gradient/style behind the live scene (WORK-428 §4) — both land in the same data-name="bg" div.siteConfig.backgrounds; the engine continues to merge theme+project for the gradient/style (boot-frame) path. A theme-defined sandbox preset is out of scope by design.