The type now GOVERNS the composition, not just declares the slot. A Composition field carries
its grammar: {:name "body" :type "Composition" :blocks (…card types…) :allow ("cond" "each")}.
:blocks absent -> any card subtype (back-compat); :allow absent -> both control blocks.
- host/blog--{field-decl, allowed-blocks, allows-control?, block-allowed?, comp-violations}.
- The editor PALETTE is the grammar: one <option> per allowed card type (spliced as direct
<select> children), and the conditional/repeater add-forms appear only if :allow permits.
- block-add-submit ENFORCES it (was a coarse "any card subtype" check) — the type governs writes.
- comp-violations flags a composition holding a forbidden block (the save/import gate).
- article declares its :body grammar (all 7 card kinds + cond/each).
blog 179/179, full conformance 408/408 (+ grammar tests: allowed-blocks/allows-control?,
palette shows only permitted kinds, add rejects a forbidden card, violations flags one).
Part B (relations as type-governed composition) + Part C (edit the type definition) next.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
giles
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