AGENTS.md

@@ -296,11 +296,10 @@ someone spells it or pins it.
   attribute's and a carried node's alike — are all held to 500 levels (`largestNesting`), so a
   deep document is a `Result` rather than the stack overflow that waits near 2000. An attribute
   is counted from its value; a spelling that nests it deeper — the block directive's `marks`, the
-  carry — refuses in its own format, as its parser does. A list giving way after its walk owes
+  carry — refuses in its own format, as its parser does. A list giving way to the directive form
-  the directive form a level the walk did not count, and the walk reports its headroom — the
+  refuses at zero headroom rather than walking again; counting every list twice halved the list
-  least slack any depth guard below it has — for the fallback to refuse at zero rather than walk
+  limit, counting the directive form once doubled the parser's frames per level (the maintainer,
-  again; counting every list twice halved the list limit, counting the directive form once
+  2026-09-18).
-  doubled the parser's frames per level (the maintainer, 2026-09-18).
 - Nothing spreads an unbounded array into a call — a node's siblings, a code block's held lines, a
   mark run's segments: the argument list caps near 125k and throws a `RangeError` where a `Result`
   is owed. A walk pushes one at a time. A literal spread (`[...value]`) is not the same thing and

src/markdown/emit/adf-to-markdown.ts

@@ -19,7 +19,7 @@ type BlockContainer = 'directive' | 'document' | 'list-item'
 type BlockSpelling = 'commonmark' | 'directive' | 'list'
 type EmittedBlock = { headroom: number; spelling: BlockSpelling; text: string }
 type KeptSpelling = { block: EmittedBlock | undefined; depth: number }
-type PlacedBlock = EmittedBlock & { node: AdfNode }
+type PlacedBlock = Omit<EmittedBlock, 'headroom'> & { node: AdfNode }
 export type SpellingMemo = Map<AdfNode, KeptSpelling>
 type Walk = { blocks: readonly PlacedBlock[]; headroom: number }
 type WalkedItem = { node: AdfNode; walk: Walk }
@@ -246,6 +246,7 @@ function tryList(node: AdfNode, path: ConvertErrorPath, depth: number, memo: Spe
   for (const [offset, item] of walked.entries()) {
     const line = tryListItemLines(item.walk.blocks, ordered ? `${start + offset}. ` : '- ')
     if (line === undefined) {
+      // The directive form spends a level the walk did not count.
       if (headroom < 1) return tooDeep(path)
       return emitDirectiveBlock(node, ordered ? blockNodes.orderedList : blockNodes.bulletList, path, depth, () => success({ blocks: directiveItems(walked), headroom: headroom - 1 }))
     }
@@ -254,9 +255,8 @@ function tryList(node: AdfNode, path: ConvertErrorPath, depth: number, memo: Spe
   return success({ headroom, spelling: 'list', text: lines.join('\n') })
 }
 
-// The directive form sinks each item's blocks a level below where the walk read them.
 function directiveItems(items: readonly WalkedItem[]): PlacedBlock[] {
-  return items.map((item) => ({ ...directivePair(item.node, listItemOpener, joinBlocks(item.walk.blocks, 'directive'), item.walk.headroom - 1), node: item.node }))
+  return items.map((item) => ({ ...directivePair(item.node, listItemOpener, joinBlocks(item.walk.blocks, 'directive')), node: item.node }))
 }
 
 function listStart(node: AdfNode, items: number): number | undefined {

todo-history.md

@@ -1066,6 +1066,11 @@ The done `todo.md` items in full, as they were written. `todo.md` keeps a one-li
       pass's set read-only and returns the whole. `containerStack` is the one writer of the stack,
       `edges` and the open directives' depths by name, all read-only elsewhere; deriving `edges` from the
       stack instead makes every line walk the open directives, quadratic in their nesting.
+- [x] **27 — The dead `headroom` write goes (`0.2.0`).** `directiveItems`
+      (`emit/adf-to-markdown.ts:258`) writes `item.walk.headroom - 1` onto each `PlacedBlock`, and
+      nothing on that path reads a block's `headroom`: `joinBlocks` and `separationBetween` read
+      `text` and `spelling`, and `emitDirectiveBlock` takes the level from the `Walk`. Of the two
+      subtractions three readers flagged as double-counting, this is the one that is dead.
 
 ## 5 — Ship `0.1.0`
 

todo.md

@@ -59,11 +59,7 @@ chunk clearing a §11 seam.
 - [x] **24 — The conformance gates have a directory (`0.2.0`).**
 - [x] **25 — AGENTS.md §8 and §11 are findable (`0.2.0`).**
 - [x] **26 — The two mutable structures say what they guarantee (`0.2.0`).**
-- [ ] **27 — The dead `headroom` write goes (`0.2.0`).** `directiveItems`
+- [x] **27 — The dead `headroom` write goes (`0.2.0`).**
-      (`emit/adf-to-markdown.ts:258`) writes `item.walk.headroom - 1` onto each `PlacedBlock`, and
-      nothing on that path reads a block's `headroom`: `joinBlocks` and `separationBetween` read
-      `text` and `spelling`, and `emitDirectiveBlock` takes the level from the `Walk`. Of the two
-      subtractions three readers flagged as double-counting, this is the one that is dead.
 - [x] **0 — Scaffold.**
 - [x] **1a — The directive grammar.**
 - [x] **1b — Block node syntaxes.**