Reserved `fields` attribute + schema dual-emit

Step 1 of SPEC-082. Introduce the typed field-data channel: rune schemas write their field values to a single reserved attribute, data-rune-fields, holding a JSON-encoded object — produced by createComponentRenderable (properties populate it). Keep emitting the legacy <meta data-field> children in parallel (dual-emit) so behavior is unchanged. No engine changes in this step.

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Criteria completion

Tracking started Jun 3 — check back for trends.

Relationships

ID:SPEC-082Status:draft

Typed node data channel

ID:v0.18.0Status:planning

v0.18.0 — Contract hardening

ID:WORK-322Status:done

Engine reads the fields attribute (dual-read)

Priority:highComplexity:moderateMilestone:v0.18.0

ID:WORK-326Status:done

Move semantic derivation out of postTransform (budget totals)

Priority:mediumComplexity:moderateMilestone:v0.18.0

ID:WORK-328Status:done

Migrate pre-engine field consumers to the fields bag

Priority:highComplexity:moderateMilestone:v0.18.0

main current done

claude/rune-contract-hardening done changeset-release/main done main done

Acceptance Criteria

Reserved attribute key chosen and documented — working name data-rune-fields; value is a JSON-encoded Record<string, FieldValue> where FieldValue = string | number | boolean | string[].
createComponentRenderable writes its properties into data-rune-fields on the node, in addition to the existing <meta data-field> emission.
Values are typed where natural (e.g. servings → number); JSON quotes are escaped against the attribute delimiter by the serializer.
No output change — the engine still reads the legacy metas this step; the rendered HTML is byte-identical. Full suite + contracts green.
Unit test at the helper level: a renderable's properties appear both in data-rune-fields (typed, parsed) and as the legacy metas.

References

SPEC-082 — typed node data channel.

Resolution

Completed: 2026-06-02

Branch: claude/rune-contract-hardening

What was done

createComponentRenderable (packages/runes/src/lib/component.ts) now projects scalar properties into a single reserved data-rune-fields attribute on the root — a JSON-encoded object — in addition to the legacy <meta data-field> children (dual-emit). Keys stay as authored (camelCase, matching modifier names — no kebab transit). Only <meta> carriers with a content attribute contribute a value; content-marker properties (cursors of real content tags, e.g. budget's category) get data-field but no field entry. Values are preserved with their JS type (a numeric content stays a number in the JSON).
Engine (packages/transform/src/engine.ts): added data-rune-fields to the consumed-attribute destructure so it is stripped from rendered output. The engine does NOT read it yet (that's WORK-322) — this keeps step 1 output-neutral.

Verification

refrakt inspect confirms api/budget/symbol now carry data-rune-fields on the (pre-strip) root with camelCase keys; the attribute is absent from final rendered output (stripped).
Full suite green (3052 tests; one heavy real-file dogfood test flaked once under parallel load, passed on rerun and in isolation). Added 3 helper-level unit tests in component.test.ts (dual-emit + typed values; content-marker exclusion; omitted-when-empty).

Notes

Reserved key: data-rune-fields (consistent with the data-* convention). FieldValue = string | number | boolean | string[].
No output change: the attribute is internal and stripped; the engine still reads the legacy metas. WORK-322 switches the engine to read fields (dual-read).