Vocabulary

   ASK  (produce a <stamp>, then freeze)
     @choice    one-of-N or many-of-N, text rows
     @gallery   the same, but visual: images, swatches, typefaces, cards
     @input     typed fields
     @upload    file drop. Real attachments, not links.
     @link      paste a URL, get a fetched preview card
     @scale     one or more sliders between two named poles
     @order     drag N items into a ranking
     @connect   a key to somewhere the agent cannot reach on its own

   SHOW (never produce a stamp, never freeze)
     @note      prose, hints, warnings. Body is markdown.
     @code      a verbatim literal, inside the block
     @example   a canned value that fills an ASK block
     @board     task rows grouped into lanes
     @chart     one series of numbers, drawn as a shape
     @flow      steps and arrows, drawn as a diagram

   SHOW, until ask= (a record; with ask= it is an ASK block and stamps once)
     @card      one work item: subtasks, counted progress, status
     @message   a message an agent proposes to send

   LAYOUT (holds blocks, has no identity, cannot be answered)
     @grid      up to N columns, collapsing on the container
     @stack     one column, controlled gap
     @end       closes the innermost container

   CONTROL
     @void      retract an unanswered block the conversation moved past

Sixteen blocks, two containers and one directive. The set is closed on purpose. Almost everything an implementer is tempted to add (@confirm, @yesno, @palette, @rate, @multi, @markdown) is one of these with an attribute set.

The set splits on what the human sees, not on what the data is. That line has been here since the beginning — @choice and @gallery hold identical rows and differ only in how they are drawn — and it is the test a new block has to pass. @board is @card’s rows in lanes, and it earns a name for the same reason @gallery does: lanes and a checklist are two different things to look at, and an attribute that silently changes what a block is on screen is harder to read than a second name.

@card passes a stronger test than that. A work item drawn as a @note full of markdown has a progress number the agent typed by hand, and a number typed by hand is a number that can disagree with the list underneath it. A block that counts cannot.

Two blocks change category on an attribute, and both say so out loud: @card and @message are records until ask= turns them into questions. Nothing else in the set does this, and nothing else should.

@markdown in particular does not exist and should not be added: it would be @note with different escaping. @note renders markdown. @code lang=markdown is a third thing again — show markdown source rather than render it — so the two are deliberately not aliased.