diff --git a/README.md b/README.md
index 13400dd..57a1afc 100644
--- a/README.md
+++ b/README.md
@@ -445,7 +445,7 @@ The emitter raises these, and so does a parse, which asks the emitter how to spe
 | Code | Fires when | What you can do |
 | --- | --- | --- |
 | `unsupported-nesting-depth` | blocks, marks, an attribute's JSON or a carried node's JSON nest past 500 levels | keep the ADF and pass the document over, or show it read-only; flatten the input where you are the one who wrote it |
-| `unsupported-node-shape` | parsing, in `losslessMarkdownToAdf`: markdown spells a node with an attribute, value, argument or body its type does not take, or without one it needs, wraps a directive mark around nothing or only hard breaks, writes as a directive a node or mark the lossless flavour spells as CommonMark, or puts a reserved directive out of place: `!adf:textBreak{}` parting nothing, `!adf:doc` anywhere but as the whole document, or writes as a directive a node whose CommonMark spelling would be longer than 536,870,888 characters. Emitting, in `adfToLosslessMarkdown`: a node not riding the carry that carries one mark type twice, a block or a non-text inline node holding `text`, or a leaf block or a non-text inline node holding `content`. Emitting, in `adfToPortableMarkdown`: a line or task list the portable writer cannot spell, a bug in this library. Emitting, in both writers: a document whose markdown would be longer than 536,870,888 characters, V8's longest string, on every engine. In every call: a conversion that passes the longest string or array the JavaScript engine builds | fix what the message names; [`spec/flavour.md`](https://github.com/larvit/adf-codec/blob/main/spec/flavour.md) lists every type's attributes and body. For a portable line or task list, report it as a bug. Past 536,870,888 characters or the engine's limit, set the document aside: keep the ADF and pass it over, or show it read-only |
+| `unsupported-node-shape` | parsing, in `losslessMarkdownToAdf`: markdown spells a node with an attribute, value, argument or body its type does not take, or without one it needs, wraps a directive mark around nothing or only hard breaks, writes as a directive a node or mark the lossless flavour spells as CommonMark, or puts a reserved directive out of place: `!adf:textBreak{}` parting nothing, `!adf:doc` anywhere but as the whole document, or writes as a directive a node whose CommonMark spelling would be longer than 536,870,888 characters. Emitting, in `adfToLosslessMarkdown`: a node not riding the carry that carries one mark type twice, a block or a non-text inline node holding `text`, or a leaf block or a non-text inline node holding `content`. Emitting, in `adfToPortableMarkdown`: a line or task list the portable writer cannot spell, a bug in this library. Emitting, in both writers: a document whose markdown would be longer than 536,870,888 characters, V8's longest string, on every engine; in `adfToPortableMarkdown`, also a document whose text alone is, edge whitespace included. In every call: a conversion that passes the longest string or array the JavaScript engine builds | fix what the message names; [`spec/flavour.md`](https://github.com/larvit/adf-codec/blob/main/spec/flavour.md) lists every type's attributes and body. For a portable line or task list, report it as a bug. Past 536,870,888 characters or the engine's limit, set the document aside: keep the ADF and pass it over, or show it read-only |
 
 ## The guarantees
 
diff --git a/docs/comprehension-history.md b/docs/comprehension-history.md
index 1f52385..adcea33 100644
--- a/docs/comprehension-history.md
+++ b/docs/comprehension-history.md
@@ -602,3 +602,28 @@ Inherited architect, decided by:
 - Navigation, Shape: `src/markdown/length-bound.ts:41` `withinEngineLimits`: a too-long symptom leads straight to the module named for it
 - Shape: `src/markdown/directive-syntax.ts:133` `spellDirectiveOpener`: each spelling is a string function and a pieces generator
 - Shape: `src/markdown/opaque-carry.ts:64` `carriedJson`: the lambda parameter `spelled` shadows the function's own
+
+## 2026-10-12T16:40:52Z, PR #36 at acd22aa, against 7a27f6b
+
+Ruling: worse
+
+| Seat | Navigation | Locality | Shape | Self-sufficiency | Overall |
+|---|---|---|---|---|---|
+| Mid A | better | worse | worse | same | worse |
+| Inherited architect | better | worse | worse | same | worse |
+
+Mid A, decided by:
+
+- Locality, Shape: `src/markdown/emit/adf-to-markdown.ts:374` `spelledList`: a builder's `undefined` now means either no list spelling or past the length bound, and every caller of `joinBlocks` must remember which it holds
+- Shape: `src/markdown/emit/adf-to-markdown.ts:383` `listLines`: split, map and join became generators yielding pieces into `separatedBy` and `joinedWithin`, so a reader rebuilds the string in their head
+- Locality: `src/markdown/emit/adf-to-markdown.ts:125` `readableBlock`: the memo is filled in `commonMarkSpelling` and deleted on read, a one-shot cache whose hits depend on which walk came first
+- Navigation: `src/markdown/length-bound.ts:41` `withinEngineLimits`: a too-long refusal leads to a module named for it
+
+Inherited architect, decided by:
+
+- Locality, Shape: `src/markdown/emit/adf-to-markdown.ts:374` `spelledList`: `undefined` means two things a few lines apart, told apart only by the side of a nested `boundedThen` callback
+- Locality: `src/markdown/emit/adf-to-markdown.ts:125` `readableBlock`: reading the memo is a mutation, and a second read spells again
+- Shape: `src/markdown/pipe-table-syntax.ts:43` `pipeRowPieces`: one-line templates became generators whose output cannot be read off one line
+- Locality, Shape: `src/markdown/emit/block-directive-spelling.ts:27` `spellBlockDirectiveOpener`: the opener's layout is known here and in `spellDirectiveOpener`
+- Shape: `src/markdown/portable/adf-to-portable-markdown.ts:231` `reduceCodeBlock`: an ADF-to-ADF reducer carries a markdown length bound through a callback
+- Navigation: `src/markdown/length-bound.ts:41` `withinEngineLimits`: a too-long refusal leads straight to one small, well-named module
diff --git a/docs/decisions.md b/docs/decisions.md
index 496cbaa..ca6c7d1 100644
--- a/docs/decisions.md
+++ b/docs/decisions.md
@@ -666,18 +666,20 @@ is the shortest of the engines the library claims.
 
 Every writer, and the reader's CommonMark ask, refuses markdown longer than 2^29 − 24 characters
 (`longestMarkdown`) as `unsupported-node-shape` at the document's path, so the same document
-converts alike everywhere. Each builder joins its pieces — blocks, quoted and list lines, directive
-pairs and openers, fences, pipe rows, the carry's JSON — through `joinedWithin`, which stops once
-they pass the bound, so none builds a string no engine was asked for. A writer first refuses a
-document whose text alone passes the bound, since every character of it is spelled at least once. A
-deep list or quote re-indents its whole text at each level until the level that passes the bound
-refuses (`todo.md` item 109).
+converts alike everywhere. A writer first refuses a document whose text alone passes the bound: the
+lossless writer spells every character of it, and the portable reduction refuses on the caller's
+text, edge whitespace and all, since merging that text first could build past the bound. The
+builders join as they always did, and the writer's result and the CommonMark ask's spelling are held
+to the bound once built. V8 stops at the bound itself and SpiderMonkey at its own longest string,
+and `withinEngineLimits` refuses both throws as the same `tooLong`, so every engine answers alike.
+The carry's two-space JSON, which indents every value its depth over, stops at the bound unbuilt
+(`joinedWithin`). A deep list or quote re-indents its whole text at each level before the bound
+refuses it (`todo.md` item 109).
 
-A line is held to its text's length alone; what its spelling adds — escapes, link targets,
-attributes — passes V8's longest string only by throwing, and `withinEngineLimits` refuses that
-throw, and SpiderMonkey's, as the same refusal: both mean a string past the bound. `todo.md` item
-108 bounds the line itself. The engines' throws past their own longest array, and JavaScriptCore's
-`Out of memory`, which also reports a heap running short, stay refused with the engine's message.
+JavaScriptCore builds up to its own longest string, 2^31 − 1, before the check. A throw past that,
+past any engine's longest array, or JavaScriptCore's `Out of memory`, which also reports a heap
+running short, is refused with the engine's message. `todo.md` item 108 bounds the line's own
+memory.
 
 ## Nothing recurses unbounded
 
diff --git a/src/conformance/markdown-property.test.ts b/src/conformance/markdown-property.test.ts
index 7d17ea7..126d4f6 100644
--- a/src/conformance/markdown-property.test.ts
+++ b/src/conformance/markdown-property.test.ts
@@ -25,7 +25,7 @@ import {
   spellStringAttribute,
   spellVocabulary,
 } from '../markdown/directive-syntax.ts'
-import { fencePieces } from '../markdown/commonmark/backtick-runs.ts'
+import { fencedCodeBlock } from '../markdown/commonmark/backtick-runs.ts'
 import { inlineNodes } from '../adf/inline-nodes.ts'
 import { markAttributes } from '../adf/mark-attributes.ts'
 import { markSpelling } from '../markdown/mark-spellings.ts'
@@ -174,8 +174,8 @@ const carriedNode = fc.oneof(
 const spellCarry = (json: string) => spellInlineLeafDirective(carryName, `{json=${spellStringAttribute(json)}}`)
 const inlineCarry = carriedNode.map((node) => spellCarry(serializeCanonicalJson(node, 'compact')))
 const hostileInlineCarry = fc.oneof(carriedNode, jsonValue).map((node) => spellCarry(JSON.stringify(node, null, 1)))
-const blockCarry = carriedNode.map((node) => fencePieces(carryName, serializeCanonicalJson(node, 'two-space')).join(''))
-const hostileBlockCarry = fc.oneof(carriedNode, jsonValue).map((node) => fencePieces(carryName, JSON.stringify(node)).join(''))
+const blockCarry = carriedNode.map((node) => fencedCodeBlock(carryName, serializeCanonicalJson(node, 'two-space')))
+const hostileBlockCarry = fc.oneof(carriedNode, jsonValue).map((node) => fencedCodeBlock(carryName, JSON.stringify(node)))
 
 function prefixLines(body: string, first: string, rest: (index: number) => string): string {
   return body
diff --git a/src/markdown/commonmark/backtick-runs.ts b/src/markdown/commonmark/backtick-runs.ts
index 8cdce83..b64f9f9 100644
--- a/src/markdown/commonmark/backtick-runs.ts
+++ b/src/markdown/commonmark/backtick-runs.ts
@@ -15,9 +15,9 @@ export function closingBacktickRun(text: string, from: number, opener: number):
   return undefined
 }
 
-export function fencePieces(info: string, body: string): string[] {
+export function fencedCodeBlock(info: string, body: string): string {
   const fence = '`'.repeat(Math.max(3, longestBacktickRun(body) + 1))
-  return body === '' ? [fence, info, '\n', fence] : [fence, info, '\n', body, '\n', fence]
+  return body === '' ? `${fence}${info}\n${fence}` : `${fence}${info}\n${body}\n${fence}`
 }
 
 export function longestBacktickRun(text: string): number {
diff --git a/src/markdown/directive-syntax.ts b/src/markdown/directive-syntax.ts
index a46dec6..e91da0b 100644
--- a/src/markdown/directive-syntax.ts
+++ b/src/markdown/directive-syntax.ts
@@ -112,18 +112,9 @@ export function slotFault(type: string, text: string): ConvertFault | undefined
 }
 
 export function spellAttributes(pairs: readonly (readonly [string, string])[]): string {
-  return [...attributePieces(pairs)].join('')
-}
-
-export function* attributePieces(pairs: readonly (readonly [string, string])[]): Generator<string> {
-  if (pairs.length === 0) return
-  yield '{'
-  for (const [index, [key, value]] of [...pairs].sort(([left], [right]) => keyOrder(left, right)).entries()) {
-    if (index > 0) yield ' '
-    yield `${key}=`
-    yield value
-  }
-  yield '}'
+  if (pairs.length === 0) return ''
+  const spelled = [...pairs].sort(([left], [right]) => keyOrder(left, right)).map(([key, value]) => `${key}=${value}`)
+  return `{${spelled.join(' ')}}`
 }
 
 export function spellDirectiveCloser(name: string): string {
diff --git a/src/markdown/emit/adf-to-markdown.test.ts b/src/markdown/emit/adf-to-markdown.test.ts
index 65b282d..cd3e40c 100644
--- a/src/markdown/emit/adf-to-markdown.test.ts
+++ b/src/markdown/emit/adf-to-markdown.test.ts
@@ -46,7 +46,7 @@ test('refuses a value that is not an ADF document, naming the check it failed',
 
 const tooLong = 'unsupported-node-shape: spelled as markdown, this would be longer than 536870888 characters, the longest string V8 holds'
 
-// A code block of 300 lines, two of them some 1000 characters short of V8's longest string, so only what their spelling adds passes it.
+// A code block of 300 lines; two of these together fall some 1000 characters short of V8's longest string, so only what their spelling adds passes it.
 function nearlyHalfTheBound(): AdfNode {
   return { attrs: {}, content: [{ text: `${'a'.repeat(894_782)}\n`.repeat(300), type: 'text' }], type: 'codeBlock' }
 }
diff --git a/src/markdown/emit/adf-to-markdown.ts b/src/markdown/emit/adf-to-markdown.ts
index 0449581..e3f46e6 100644
--- a/src/markdown/emit/adf-to-markdown.ts
+++ b/src/markdown/emit/adf-to-markdown.ts
@@ -5,14 +5,14 @@ import { adfDocumentFault, heldTextLength, holdsOnlyAttributes, isUnmarkedSpella
 import { alertMarker, flavourClaims, foldedAlertMarker, leadingMarker, readAlertMarker, readTaskMarker, taskMarker } from '../portable/conventions.ts'
 import { blockDirectiveForm, documentSpelling } from '../block-directive.ts'
 import { blockNodeModel, blockNodes, isTaskItem } from '../../adf/block-nodes.ts'
-import { boundedThen, joinedWithin, longestMarkdown, separatedBy, tooLong, withinEngineLimits } from '../length-bound.ts'
 import { carriedBlock } from '../opaque-carry.ts'
 import { emitInlineLine } from './inline-line.ts'
 import { failure, faulted, success, type ConvertErrorPath, type Result } from '../../result.ts'
-import { fencePieces } from '../commonmark/backtick-runs.ts'
+import { fencedCodeBlock } from '../commonmark/backtick-runs.ts'
 import { holdsNullCharacter, isBlankLine, isThematicBreak, markerInterruptsParagraph } from '../commonmark/grammar.ts'
 import { languageSlot, type LanguageSlot } from '../code-language.ts'
 import { largestNesting } from '../../nesting.ts'
+import { longestMarkdown, tooLong, withinEngineLimits, withinLongest } from '../length-bound.ts'
 import { spellBlockDirectiveOpener } from './block-directive-spelling.ts'
 import { spellDirectiveCloser, spellDirectiveOpener } from '../directive-syntax.ts'
 import { tryImage } from './image.ts'
@@ -28,9 +28,9 @@ type PlacedBlocks = { blocks: readonly PlacedBlock[]; headroom: number }
 // CommonMark starts a new list where the marker changes, so every second list in a run of one kind takes `alternateText`.
 type SpelledBlock = { spelling: 'commonmark' | 'directive'; text: string } | { alternateText: string; spelling: 'list'; text: string }
 // Keyed by reference: only a caller building one object per position (the parse, the portable reduction) passes one; a consumer's document may share a node.
+// Holds the spelling of each node the CommonMark ask was put to, until the walk above reads it.
 export type SpellingMemo = Map<AdfNode, KeptSpelling>
-// inner: the item's blocks joined, for the list form; walk: the blocks themselves, for the directive form.
-type WalkedItem = { inner: string; node: AdfNode; walk: PlacedBlocks }
+type WalkedItem = { node: AdfNode; walk: PlacedBlocks }
 export type Writing = { flavour: WrittenFlavour; memo: SpellingMemo | undefined }
 
 const bulletDelimiters: Delimiters = ['-', '*']
@@ -52,8 +52,8 @@ export function writeMarkdown(document: AdfDocument, flavour: WrittenFlavour): R
   if (heldTextLength(document.content) > longestMarkdown) return tooLong()
   const walk = walkBlocks(document.content, [], 0, { flavour, memo: undefined })
   if (!walk.ok) return walk
-  const text = joinedWithin(walk.value.blocks.length === 0 ? [] : [...blockPieces(walk.value.blocks, 'document'), '\n'])
-  return boundedThen(text, success)
+  const text = joinBlocks(walk.value.blocks, 'document')
+  return withinLongest(text === '' ? '' : `${text}\n`)
 }
 
 function walkBlocks(nodes: readonly AdfNode[], path: ConvertErrorPath, depth: number, writing: Writing): Result<PlacedBlocks> {
@@ -73,18 +73,16 @@ function tooDeep(path: ConvertErrorPath): Result<never> {
   return failure('unsupported-nesting-depth', `the document nests deeper than the ${largestNesting} levels the emitter carries`, path)
 }
 
-function joinBlocks(blocks: readonly PlacedBlock[], container: BlockContainer): string | undefined {
-  return joinedWithin(blockPieces(blocks, container))
-}
-
-function* blockPieces(blocks: readonly PlacedBlock[], container: BlockContainer): Generator<string> {
+function joinBlocks(blocks: readonly PlacedBlock[], container: BlockContainer): string {
+  let text = ''
   let alternated = false
   for (const [index, block] of blocks.entries()) {
     const previous = blocks[index - 1]
-    if (previous !== undefined) yield separationBetween(previous, block, container)
+    if (previous !== undefined) text += separationBetween(previous, block, container)
     alternated = !alternated && previous !== undefined && sharesMarker(previous, block)
-    yield alternated && block.spelling === 'list' ? block.alternateText : block.text
+    text += alternated && block.spelling === 'list' ? block.alternateText : block.text
   }
+  return text
 }
 
 // A task list is spelled as a bullet list.
@@ -119,6 +117,8 @@ export function commonMarkSpelling(node: AdfNode, path: ConvertErrorPath, depth:
   else if (readable.ok) writing.memo.set(node, { block: readable.value, depth })
   if (readable === undefined) return undefined
   if (!readable.ok) return readable
+  // V8 throws past the bound while building the spelling; an engine holding longer strings refuses here alike.
+  if (readable.value.text.length > longestMarkdown) return tooLong()
   return readable.value.spelling === 'directive' ? undefined : success(null)
 }
 
@@ -139,15 +139,12 @@ function spellReadableBlock(node: AdfNode, path: ConvertErrorPath, depth: number
   if (portable !== undefined) return portable
   if (node.type === 'blockquote') return tryBlockquote(node, path, depth, writing)
   if (node.type === 'bulletList' || node.type === 'orderedList') return tryList(node, path, depth, writing)
-  if (node.type === 'codeBlock') return tryCodeBlock(node, writing.flavour)
+  if (node.type === 'codeBlock') return readableText(tryCodeBlock(node, writing.flavour))
   if (node.type === 'heading') return tryHeading(node, path, writing.flavour)
   if (node.type === 'mediaSingle') return readableText(tryImage(node))
   if (node.type === 'paragraph') return tryParagraph(node, path, writing.flavour)
   if (node.type === 'rule') return readableText(tryRule(node))
-  if (node.type === 'table') {
-    const table = tryPipeTable(node, path, writing.flavour)
-    return table === undefined || !table.ok ? table : success(commonMarkText(table.value))
-  }
+  if (node.type === 'table') return readableText(tryPipeTable(node, path, writing.flavour))
   return undefined
 }
 
@@ -165,25 +162,15 @@ function spellPortableBlock(node: AdfNode, path: ConvertErrorPath, depth: number
 function quotedUnder(head: string, node: AdfNode, path: ConvertErrorPath, depth: number, writing: Writing): Result<EmittedBlock> {
   const inner = walkBlocks(nodeContent(node), path, depth + 1, writing)
   if (!inner.ok) return inner
-  const text = joinedWithin(inner.value.blocks.length === 0 ? [head] : [head, '\n\n', ...blockPieces(inner.value.blocks, 'document')])
-  return quotedBlock(text, inner.value.headroom)
+  const body = joinBlocks(inner.value.blocks, 'document')
+  return success(commonMarkText(quoted(body === '' ? head : `${head}\n\n${body}`), inner.value.headroom))
 }
 
-function quotedBlock(text: string | undefined, headroom: number): Result<EmittedBlock> {
-  const quoted = text === undefined ? undefined : joinedWithin(quotedPieces(text))
-  return boundedThen(quoted, (spelled) => success(commonMarkText(spelled, headroom)))
-}
-
-function* quotedPieces(text: string): Generator<string> {
-  for (let start = 0; ; ) {
-    const end = text.indexOf('\n', start)
-    const line = text.slice(start, end === -1 ? text.length : end)
-    yield line === '' ? '>' : '> '
-    yield line
-    if (end === -1) return
-    yield '\n'
-    start = end + 1
-  }
+function quoted(text: string): string {
+  return text
+    .split('\n')
+    .map((line) => (line === '' ? '>' : `> ${line}`))
+    .join('\n')
 }
 
 function tryTaskList(node: AdfNode, path: ConvertErrorPath, depth: number, writing: Writing): Result<EmittedBlock> {
@@ -199,21 +186,14 @@ function tryTaskList(node: AdfNode, path: ConvertErrorPath, depth: number, writi
     if (task || previous === undefined) items.push([...walk.value.blocks])
     else for (const block of walk.value.blocks) previous.push(block)
   }
-  const inners = joinedItems(items.map((blocks) => blockPieces(blocks, 'list-item')))
+  const list = spelledList(
+    items.map((blocks) => joinBlocks(blocks, 'list-item')),
+    () => '',
+    bulletDelimiters,
+    headroom,
+  )
   // The portable reduction leaves no task a list item cannot hold: a directive here would break the flavour.
-  const unspellable = failure<EmittedBlock>('unsupported-node-shape', 'a task holds blocks no list item spells', path)
-  return boundedThen(inners, (spelled) => spelledList(spelled, () => '', bulletDelimiters, headroom) ?? unspellable)
-}
-
-// Each item's text, or `undefined` where one would pass the bound.
-function joinedItems(items: readonly Iterable<string>[]): string[] | undefined {
-  const inners: string[] = []
-  for (const pieces of items) {
-    const inner = joinedWithin(pieces)
-    if (inner === undefined) return undefined
-    inners.push(inner)
-  }
-  return inners
+  return list === undefined ? failure('unsupported-node-shape', 'a task holds blocks no list item spells', path) : success(list)
 }
 
 function placedBlock(node: AdfNode, path: ConvertErrorPath, depth: number, writing: Writing): Result<PlacedBlocks> {
@@ -229,15 +209,13 @@ function taskBlocks(task: AdfNode, path: ConvertErrorPath, depth: number, writin
     const content = nodeContent(task)
     const line = content.length === 0 ? success('') : emitInlineLine(content, 'paragraph', path, writing.flavour)
     if (!line.ok) return line
-    const text = joinedWithin(line.value === '' ? [marker] : [marker, ' ', line.value])
-    return boundedThen(text, (spelled) => success({ blocks: [{ ...markerBlock, text: spelled }], headroom: Number.POSITIVE_INFINITY }))
+    return success({ blocks: [{ ...markerBlock, text: line.value === '' ? marker : `${marker} ${line.value}` }], headroom: Number.POSITIVE_INFINITY })
   }
   const walk = walkBlocks(nodeContent(task), path, depth, writing)
   if (!walk.ok) return walk
   const [first, ...rest] = walk.value.blocks
-  if (first?.node.type !== 'paragraph') return success({ blocks: [markerBlock, ...walk.value.blocks], headroom: walk.value.headroom })
-  const text = joinedWithin([marker, ' ', first.text])
-  return boundedThen(text, (spelled) => success({ blocks: [{ ...first, text: spelled }, ...rest], headroom: walk.value.headroom }))
+  const blocks = first?.node.type === 'paragraph' ? [{ ...first, text: `${marker} ${first.text}` }, ...rest] : [markerBlock, ...walk.value.blocks]
+  return success({ blocks, headroom: walk.value.headroom })
 }
 
 function readableText(text: string | undefined): Result<EmittedBlock> | undefined {
@@ -253,10 +231,8 @@ function commonMarkText(text: string, headroom: number = Number.POSITIVE_INFINIT
   return { headroom, spelling: 'commonmark', text }
 }
 
-function directivePair(node: AdfNode, opener: string, body: string, headroom: number = Number.POSITIVE_INFINITY): Result<EmittedBlock> {
-  const closer = spellDirectiveCloser(node.type)
-  const text = joinedWithin(body === '' ? [opener, '\n', closer] : [opener, '\n', body, '\n', closer])
-  return boundedThen(text, (spelled) => success({ headroom, spelling: 'directive', text: spelled }))
+function directivePair(node: AdfNode, opener: string, body: string, headroom: number = Number.POSITIVE_INFINITY): EmittedBlock {
+  return { headroom, spelling: 'directive', text: `${opener}\n${body === '' ? '' : `${body}\n`}${spellDirectiveCloser(node.type)}` }
 }
 
 function emitDirectiveBlock(node: AdfNode, model: BlockNodeModel, path: ConvertErrorPath, depth: number, walkBody: () => Result<PlacedBlocks>): Result<EmittedBlock> {
@@ -274,12 +250,11 @@ function emitDirectiveBody(node: AdfNode, model: BlockNodeModel, opener: string,
   if (model.contentModel === 'inline') {
     const line = emitInlineLine(nodeContent(node), 'paragraph', path, 'lossless')
     if (!line.ok) return line
-    return directivePair(node, opener, line.value)
+    return success(directivePair(node, opener, line.value))
   }
   const walk = walkBody()
   if (!walk.ok) return walk
-  const body = joinBlocks(walk.value.blocks, 'directive')
-  return boundedThen(body, (spelled) => directivePair(node, opener, spelled, walk.value.headroom))
+  return success(directivePair(node, opener, joinBlocks(walk.value.blocks, 'directive'), walk.value.headroom))
 }
 
 function tryBlockquote(node: AdfNode, path: ConvertErrorPath, depth: number, writing: Writing): Result<EmittedBlock> | undefined {
@@ -287,18 +262,17 @@ function tryBlockquote(node: AdfNode, path: ConvertErrorPath, depth: number, wri
   const inner = walkBlocks(nodeContent(node), path, depth + 1, writing)
   if (!inner.ok) return inner
   const text = joinBlocks(inner.value.blocks, 'document')
-  const alert = text !== undefined && flavourClaims[writing.flavour].alerts && leadingMarker(text, readAlertMarker) !== undefined
-  return quotedBlock(alert ? joinedWithin(['\\', text]) : text, inner.value.headroom)
+  const alert = flavourClaims[writing.flavour].alerts && leadingMarker(text, readAlertMarker) !== undefined
+  return success(commonMarkText(quoted(alert ? `\\${text}` : text), inner.value.headroom))
 }
 
-function tryCodeBlock(node: AdfNode, flavour: WrittenFlavour): Result<EmittedBlock> | undefined {
+function tryCodeBlock(node: AdfNode, flavour: WrittenFlavour): string | undefined {
   if (!holdsOnlyAttributes(node, ['language'])) return undefined
   const slot = languageSlot(nodeAttrs(node)['language'], flavourClaims[flavour])
   if (slot.kind === 'attribute') return undefined
   const [only, ...others] = fencedTexts(node) ?? []
   if (only === undefined || others.length > 0) return undefined
-  const text = joinedWithin(fencePieces(slot.kind === 'fence' ? slot.info : '', only))
-  return boundedThen(text, (spelled) => success(commonMarkText(spelled)))
+  return fencedCodeBlock(slot.kind === 'fence' ? slot.info : '', only)
 }
 
 // spec/flavour.md, The CommonMark blocks: one fence per text node, the language on each; with no fence to carry it, the attribute does.
@@ -310,8 +284,7 @@ function emitCodeDirective(node: AdfNode, model: BlockNodeModel, path: ConvertEr
   if (opener === undefined) return carriedFence(carriedBlock(node, path, depth))
   if (!opener.ok) return opener
   const info = slot.kind === 'fence' ? slot.info : ''
-  const body = joinedWithin(separatedBy('\n', texts.map((text) => fencePieces(info, text))))
-  return boundedThen(body, (spelled) => directivePair(node, opener.value, spelled))
+  return success(directivePair(node, opener.value, texts.map((text) => fencedCodeBlock(info, text)).join('\n')))
 }
 
 // The text of each fence, or `undefined` where a child holds what no fence keeps, so the block carry takes the node.
@@ -349,55 +322,39 @@ function tryList(node: AdfNode, path: ConvertErrorPath, depth: number, writing:
   for (const [offset, item] of items.entries()) {
     const walk = walkBlocks(nodeContent(item), [...path, 'content', offset], depth + 1, writing)
     if (!walk.ok) return walk
-    const inner = joinBlocks(walk.value.blocks, 'list-item')
-    if (inner === undefined) return tooLong()
     headroom = Math.min(headroom, walk.value.headroom)
-    walked.push({ inner, node: item, walk: walk.value })
+    walked.push({ node: item, walk: walk.value })
   }
-  const number = ordered ? (offset: number): string => `${start + offset}` : (): string => ''
-  return spelledOrDirectiveList(node, walked, number, { depth, headroom, path, writing })
-}
-
-// The list spelling where every item holds lines a list item spells, else the directive form.
-function spelledOrDirectiveList(node: AdfNode, walked: readonly WalkedItem[], number: (offset: number) => string, at: { depth: number; headroom: number; path: ConvertErrorPath; writing: Writing }): Result<EmittedBlock> {
-  const ordered = node.type === 'orderedList'
-  // GitHub reads a task marker opening any item's first paragraph as a checkbox, whatever its siblings hold.
-  const escapesMarker = (inner: string): boolean => flavourClaims[at.writing.flavour].taskMarkers && leadingMarker(inner, readTaskMarker) !== undefined
-  const inners = walked.map(({ inner }) => (escapesMarker(inner) ? `\\${inner}` : inner))
-  const list = spelledList(inners, number, ordered ? orderedDelimiters : bulletDelimiters, at.headroom)
-  if (list !== undefined) return list
+  const inners = walked.map((item) => {
+    const inner = joinBlocks(item.walk.blocks, 'list-item')
+    // GitHub reads a task marker opening any item's first paragraph as a checkbox, whatever its siblings hold.
+    return flavourClaims[writing.flavour].taskMarkers && leadingMarker(inner, readTaskMarker) !== undefined ? `\\${inner}` : inner
+  })
+  const list = ordered ? spelledList(inners, (offset) => `${start + offset}`, orderedDelimiters, headroom) : spelledList(inners, () => '', bulletDelimiters, headroom)
+  if (list !== undefined) return success(list)
   // The directive form spends a level the walk did not count.
-  if (at.headroom < 1) return tooDeep(at.path)
-  return emitDirectiveBlock(node, ordered ? blockNodes.orderedList : blockNodes.bulletList, at.path, at.depth, () => directiveItems(walked, at.headroom - 1))
+  if (headroom < 1) return tooDeep(path)
+  return emitDirectiveBlock(node, ordered ? blockNodes.orderedList : blockNodes.bulletList, path, depth, () => success({ blocks: directiveItems(walked), headroom: headroom - 1 }))
 }
 
-function spelledList(inners: readonly string[], number: (offset: number) => string, [usual, alternate]: Delimiters, headroom: number): Result<EmittedBlock> | undefined {
-  const pieces = listLines(inners, number, usual)
-  const alternatePieces = listLines(inners, number, alternate)
-  if (pieces === undefined || alternatePieces === undefined) return undefined
-  const withAlternate = (text: string): Result<EmittedBlock> => boundedThen(joinedWithin(alternatePieces), (alternateText) => success({ alternateText, headroom, spelling: 'list', text }))
-  return boundedThen(joinedWithin(pieces), withAlternate)
+function spelledList(inners: readonly string[], number: (offset: number) => string, [usual, alternate]: Delimiters, headroom: number): EmittedBlock | undefined {
+  const text = listLines(inners, number, usual)
+  const alternateText = listLines(inners, number, alternate)
+  return text === undefined || alternateText === undefined ? undefined : { alternateText, headroom, spelling: 'list', text }
 }
 
-// `undefined` where an item holds a line no list item spells.
-function listLines(inners: readonly string[], number: (offset: number) => string, delimiter: string): Iterable<string> | undefined {
-  const items: Iterable<string>[] = []
+function listLines(inners: readonly string[], number: (offset: number) => string, delimiter: string): string | undefined {
+  const lines: string[] = []
   for (const [offset, inner] of inners.entries()) {
-    const pieces = listItemPieces(inner, `${number(offset)}${delimiter} `)
-    if (pieces === undefined) return undefined
-    items.push(pieces)
+    const line = tryListItemLines(inner, `${number(offset)}${delimiter} `)
+    if (line === undefined) return undefined
+    lines.push(line)
   }
-  return separatedBy('\n', items)
+  return lines.join('\n')
 }
 
-function directiveItems(items: readonly WalkedItem[], headroom: number): Result<PlacedBlocks> {
-  const blocks: PlacedBlock[] = []
-  for (const item of items) {
-    const pair = boundedThen(joinBlocks(item.walk.blocks, 'directive'), (body) => directivePair(item.node, listItemOpener, body))
-    if (!pair.ok) return pair
-    blocks.push({ ...pair.value, node: item.node })
-  }
-  return success({ blocks, headroom })
+function directiveItems(items: readonly WalkedItem[]): PlacedBlock[] {
+  return items.map((item) => ({ ...directivePair(item.node, listItemOpener, joinBlocks(item.walk.blocks, 'directive')), node: item.node }))
 }
 
 function listStart(node: AdfNode, items: number): number | undefined {
@@ -407,25 +364,16 @@ function listStart(node: AdfNode, items: number): number | undefined {
   return start + items - 1 > largestListMarker ? undefined : start
 }
 
-function listItemPieces(inner: string, marker: string): Iterable<string> | undefined {
-  if (inner === '') return [marker.trimEnd()]
-  const [first = '', ...rest] = inner.split('\n')
-  if (rest.some((line) => line !== '' && isBlankLine(line)) || (first !== '' && isBlankLine(first))) return undefined
+function tryListItemLines(inner: string, marker: string): string | undefined {
+  if (inner === '') return marker.trimEnd()
+  const body = inner.split('\n')
+  if (body.some((line) => line !== '' && isBlankLine(line))) return undefined
+  const indent = ' '.repeat(marker.length)
+  const lines = body.map((line, index) => (index === 0 ? `${marker}${line}` : line === '' ? '' : `${indent}${line}`))
+  const first = lines[0] ?? ''
+  if (!isThematicBreak(first)) return lines.join('\n')
   // An item opens with `*` only as text, a list there taking `- ` and a rule `---`; a backslash keeps a first line reading as a rule text.
-  const rule = isThematicBreak(`${marker}${first}`)
-  if (rule && !inner.startsWith('*')) return undefined
-  return itemLinePieces(rule ? `${marker}\\` : marker, first, rest, ' '.repeat(marker.length))
-}
-
-function* itemLinePieces(opening: string, first: string, rest: readonly string[], indent: string): Generator<string> {
-  yield opening
-  yield first
-  for (const line of rest) {
-    yield '\n'
-    if (line === '') continue
-    yield indent
-    yield line
-  }
+  return inner.startsWith('*') ? [`${marker}\\${first.slice(marker.length)}`, ...lines.slice(1)].join('\n') : undefined
 }
 
 function tryParagraph(node: AdfNode, path: ConvertErrorPath, flavour: WrittenFlavour): Result<EmittedBlock> | undefined {
diff --git a/src/markdown/emit/block-directive-spelling.ts b/src/markdown/emit/block-directive-spelling.ts
index 4886211..9c42408 100644
--- a/src/markdown/emit/block-directive-spelling.ts
+++ b/src/markdown/emit/block-directive-spelling.ts
@@ -1,10 +1,9 @@
 import type { AdfNode } from '../../adf/document.ts'
 import type { BlockNodeModel } from '../../adf/block-nodes.ts'
 import { attributeNestingMessage, nodeAttrs, nodeMarks } from '../../adf/document.ts'
-import { attributePieces, isBareToken, spellDirectiveOpener, spellJsonAttribute, spellVocabulary } from '../directive-syntax.ts'
 import { blockArgument, markValues, marksAttribute } from '../block-directive.ts'
-import { boundedThen, joinedWithin } from '../length-bound.ts'
 import { failure, success, type ConvertErrorPath, type Result } from '../../result.ts'
+import { isBareToken, spellAttributes, spellDirectiveOpener, spellJsonAttribute, spellVocabulary } from '../directive-syntax.ts'
 import { overNested } from '../../json-value.ts'
 import { spellEmptyKeys } from '../empty-keys.ts'
 import { vocabularyPairs } from '../../adf/attribute-vocabulary.ts'
@@ -23,9 +22,7 @@ export function spellBlockDirectiveOpener(node: AdfNode, model: BlockNodeModel,
     if (overNested(values)) return failure('unsupported-nesting-depth', attributeNestingMessage(marksAttribute, node.type), path)
     spelledPairs.push([marksAttribute, spellJsonAttribute(values)])
   }
-  const head = spellDirectiveOpener(node.type, slot.argument, '')
-  const opener = joinedWithin(spelledPairs.length === 0 ? [head] : [head, ' ', ...attributePieces(spelledPairs)])
-  return boundedThen(opener, success)
+  return success(spellDirectiveOpener(node.type, slot.argument, spellAttributes(spelledPairs)))
 }
 
 // `undefined` where the argument slot holds a value no bare token spells.
diff --git a/src/markdown/emit/pipe-table.ts b/src/markdown/emit/pipe-table.ts
index cdf6ef9..15609f7 100644
--- a/src/markdown/emit/pipe-table.ts
+++ b/src/markdown/emit/pipe-table.ts
@@ -1,15 +1,14 @@
 import type { AdfNode } from '../../adf/document.ts'
+import type { ConvertErrorPath } from '../../result.ts'
 import type { WrittenFlavour } from '../portable/conventions.ts'
-import { boundedThen, joinedWithin, separatedBy } from '../length-bound.ts'
-import { delimiterCells, pipeRowPieces } from '../pipe-table-syntax.ts'
 import { holdsOnlyAttributes, nodeContent } from '../../adf/document.ts'
-import { success, type ConvertErrorPath, type Result } from '../../result.ts'
+import { spellPipeDelimiter, spellPipeRow } from '../pipe-table-syntax.ts'
 import { tryPipeCell } from './inline-line.ts'
 
-export function tryPipeTable(node: AdfNode, path: ConvertErrorPath, flavour: WrittenFlavour): Result<string> | undefined {
+export function tryPipeTable(node: AdfNode, path: ConvertErrorPath, flavour: WrittenFlavour): string | undefined {
   const rows = pipeRows(node)
   if (rows === undefined) return undefined
-  const spelled: string[][] = []
+  const lines: string[] = []
   for (const [rowIndex, row] of rows.entries()) {
     const cells: string[] = []
     for (const [cellIndex, paragraph] of row.entries()) {
@@ -18,17 +17,10 @@ export function tryPipeTable(node: AdfNode, path: ConvertErrorPath, flavour: Wri
       if (line === undefined) return undefined
       cells.push(line)
     }
-    spelled.push(cells)
-  }
-  const text = joinedWithin(separatedBy('\n', tableRows(spelled)))
-  return boundedThen(text, success)
-}
-
-function* tableRows(rows: readonly string[][]): Generator<Iterable<string>> {
-  for (const [index, cells] of rows.entries()) {
-    yield pipeRowPieces(cells)
-    if (index === 0) yield pipeRowPieces(delimiterCells(cells.length))
+    lines.push(spellPipeRow(cells))
+    if (rowIndex === 0) lines.push(spellPipeDelimiter(cells.length))
   }
+  return lines.join('\n')
 }
 
 function pipeRows(node: AdfNode): AdfNode[][] | undefined {
diff --git a/src/markdown/length-bound.test.ts b/src/markdown/length-bound.test.ts
index 14e6c9b..a1b571d 100644
--- a/src/markdown/length-bound.test.ts
+++ b/src/markdown/length-bound.test.ts
@@ -2,7 +2,7 @@ import assert from 'node:assert/strict'
 import test from 'node:test'
 
 import type { Result } from '../result.ts'
-import { boundedThen, joinedWithin, separatedBy, tooLong, withinEngineLimits } from './length-bound.ts'
+import { joinedWithin, tooLong, withinEngineLimits, withinLongest } from './length-bound.ts'
 import { success } from '../result.ts'
 
 function thrown(name: string, message: string): () => Result<string> {
@@ -14,14 +14,13 @@ function thrown(name: string, message: string): () => Result<string> {
 }
 
 test('joins pieces up to the bound, and builds nothing past it', () => {
-  assert.equal(joinedWithin(separatedBy(', ', [['a', 'b'], ['c']])), 'ab, c')
+  assert.deepEqual(joinedWithin(['a', 'b']), success('ab'))
   const half = 'a'.repeat(2 ** 28)
-  assert.equal(joinedWithin([half, half]), undefined)
+  assert.deepEqual(joinedWithin([half, half]), tooLong())
 })
 
-test('refuses where a bounded builder stopped, and goes on with what it built', () => {
-  assert.deepEqual(boundedThen(undefined, success), tooLong())
-  assert.deepEqual(boundedThen('x', (text) => success(`${text}!`)), success('x!'))
+test('passes a text within the bound', () => {
+  assert.deepEqual(withinLongest('x'), success('x'))
 })
 
 test('refuses a string past the bound as too long on every engine, and names any other engine limit', () => {
diff --git a/src/markdown/length-bound.ts b/src/markdown/length-bound.ts
index 8538b40..ffef555 100644
--- a/src/markdown/length-bound.ts
+++ b/src/markdown/length-bound.ts
@@ -1,9 +1,9 @@
-import { failure, type Result } from '../result.ts'
+import { failure, success, type Result } from '../result.ts'
 
 // V8's longest string, held on every engine so a document converts alike everywhere (docs/decisions.md §Markdown past V8's longest string is refused on every engine).
 export const longestMarkdown = 2 ** 29 - 24
 
-// Measured on Firefox 155, Node 24 and Bun 1.4. The first two say a string passed longestMarkdown, so they refuse as tooLong; the others name the engine's own limit.
+// Measured on Firefox 155, Node 24 and Bun 1.4. SpiderMonkey's overflow and V8's string overflow both mean a string past longestMarkdown; the other two name the engine's own limit.
 const pastLongestString = ['InternalError: allocation size overflow', 'RangeError: Invalid string length']
 const pastEngineLimit = ['RangeError: Invalid array length', 'RangeError: Out of memory']
 
@@ -11,33 +11,23 @@ export function tooLong<T>(): Result<T> {
   return failure('unsupported-node-shape', `spelled as markdown, this would be longer than ${longestMarkdown} characters, the longest string V8 holds`, [])
 }
 
-// The pieces joined, or `undefined` once their length passes longestMarkdown, so nothing past it is built.
-export function joinedWithin(pieces: Iterable<string>): string | undefined {
+export function withinLongest(text: string): Result<string> {
+  return text.length > longestMarkdown ? tooLong() : success(text)
+}
+
+// Joins the pieces as they come, so a spelling that grows far past its input stops at the bound unbuilt.
+export function joinedWithin(pieces: Iterable<string>): Result<string> {
   const kept: string[] = []
   let length = 0
   for (const piece of pieces) {
     length += piece.length
-    if (length > longestMarkdown) return undefined
+    if (length > longestMarkdown) return tooLong()
     kept.push(piece)
   }
-  return kept.join('')
+  return success(kept.join(''))
 }
 
-// The refusal where a bounded builder stopped, else what `next` makes of what it built.
-export function boundedThen<T, U>(built: T | undefined, next: (built: T) => Result<U>): Result<U> {
-  return built === undefined ? tooLong() : next(built)
-}
-
-export function* separatedBy(separator: string, parts: Iterable<Iterable<string>>): Generator<string> {
-  let first = true
-  for (const part of parts) {
-    if (!first) yield separator
-    first = false
-    yield* part
-  }
-}
-
-// A builder this module does not bound can still pass an engine's longest string or array, so this wraps a whole conversion.
+// Any concatenation can pass an engine's longest string or array, so this wraps a whole conversion.
 export function withinEngineLimits<T>(convert: () => Result<T>): Result<T> {
   try {
     return convert()
diff --git a/src/markdown/opaque-carry.ts b/src/markdown/opaque-carry.ts
index cd91d4b..6c315c3 100644
--- a/src/markdown/opaque-carry.ts
+++ b/src/markdown/opaque-carry.ts
@@ -2,11 +2,11 @@ import type { AdfNode } from '../adf/document.ts'
 import type { DirectiveSpan, Read } from './directive-syntax.ts'
 import type { JsonSpelling } from '../canonical-json.ts'
 import type { JsonValue } from '../json-value.ts'
-import { boundedThen, joinedWithin } from './length-bound.ts'
+import { joinedWithin } from './length-bound.ts'
 import { canonicalJsonPieces, spellsCanonicalJson } from '../canonical-json.ts'
 import { directiveEscape, malformedDirective, readSoleStringAttribute, spellAttributes, spellDirectiveOpener, spellInlineLeafDirective, spellStringAttribute, unsupportedNodeShape } from './directive-syntax.ts'
 import { failure, success, type ConvertErrorPath, type Result } from '../result.ts'
-import { fencePieces } from './commonmark/backtick-runs.ts'
+import { fencedCodeBlock } from './commonmark/backtick-runs.ts'
 import { infoStringCarries } from './commonmark/grammar.ts'
 import { isAdfNode } from '../adf/document.ts'
 import { isJsonValue, nestingDepth, overNested } from '../json-value.ts'
@@ -25,8 +25,7 @@ export function carriedBlock(node: AdfNode, path: ConvertErrorPath, depth: numbe
   const named = infoStringCarries(type)
   const json = carriedJson(node, named ? untyped : node, 'two-space', path, largestNesting - depth)
   if (!json.ok) return json
-  const text = joinedWithin(fencePieces(`${carryFencePrefix}${named ? type : ''}`, json.value.json))
-  return boundedThen(text, (fence) => success({ headroom: json.value.headroom, text: fence }))
+  return success({ headroom: json.value.headroom, text: fencedCodeBlock(`${carryFencePrefix}${named ? type : ''}`, json.value.json) })
 }
 
 export function carriedInline(node: AdfNode, path: ConvertErrorPath): Result<string> {
@@ -60,8 +59,9 @@ function carriedJson(node: AdfNode, spelled: object, spelling: JsonSpelling, pat
   if (!isJsonValue(spelled) || headroom < 0) {
     return failure('unsupported-nesting-depth', `a carried node's JSON nests deeper than the ${levels} levels its position leaves`, path)
   }
+  // Two-space JSON indents every value its depth over, so it stops at the bound unbuilt.
   const json = joinedWithin(canonicalJsonPieces(spelled, spelling))
-  return boundedThen(json, (text) => success({ headroom, json: text }))
+  return json.ok ? success({ headroom, json: json.value }) : json
 }
 
 // `type` is the one the fence's info string names, `undefined` for the inline carry.
diff --git a/src/markdown/pipe-table-syntax.ts b/src/markdown/pipe-table-syntax.ts
index b94798d..8d5fc58 100644
--- a/src/markdown/pipe-table-syntax.ts
+++ b/src/markdown/pipe-table-syntax.ts
@@ -36,17 +36,12 @@ export function pipeCells(line: string): string[] | undefined {
   return claimsPipeLine(line) ? splitPipeCells(line, 1) : undefined
 }
 
-export function delimiterCells(columns: number): string[] {
-  return Array.from({ length: columns }, () => '---')
+export function spellPipeDelimiter(columns: number): string {
+  return spellPipeRow(Array.from({ length: columns }, () => '---'))
 }
 
-export function* pipeRowPieces(cells: readonly string[]): Generator<string> {
-  yield '|'
-  for (const cell of cells) {
-    yield ' '
-    yield cell
-    yield ' |'
-  }
+export function spellPipeRow(cells: readonly string[]): string {
+  return `| ${cells.join(' | ')} |`
 }
 
 function splitPipeCells(line: string, start: number): string[] {
diff --git a/src/markdown/portable/adf-to-portable-markdown.ts b/src/markdown/portable/adf-to-portable-markdown.ts
index 65c39da..63bdb9e 100644
--- a/src/markdown/portable/adf-to-portable-markdown.ts
+++ b/src/markdown/portable/adf-to-portable-markdown.ts
@@ -1,7 +1,7 @@
 import type { AdfDocument, AdfNode } from '../../adf/document.ts'
 import { adfDocumentFault, heldTextLength, nodeAttrs, nodeContent, nodeMarks } from '../../adf/document.ts'
 import { blockNodeModel, isTaskItem } from '../../adf/block-nodes.ts'
-import { boundedThen, joinedWithin, longestMarkdown, tooLong, withinEngineLimits } from '../length-bound.ts'
+import { longestMarkdown, tooLong, withinEngineLimits } from '../length-bound.ts'
 import { centeredImage, externalMedia } from '../external-image.ts'
 import { commonMarkSpelling, largestListMarker, writeMarkdown, type SpellingMemo } from '../emit/adf-to-markdown.ts'
 import { failure, faulted, success, type ConvertErrorPath, type Result } from '../../result.ts'
@@ -60,7 +60,7 @@ export function reduceToPortable(document: AdfDocument): Result<AdfDocument> {
   const fault = adfDocumentFault(document)
   if (fault !== undefined) return faulted(fault, [])
   if (document.version !== 1) return failure('unsupported-document-version', `no markdown spelling carries ADF version ${document.version}`, [])
-  // The reduction drops form, never text, so this much text cannot fit, and none of it is joined.
+  // Refused on the caller's text, edge whitespace and all: merging it first would build past the bound.
   if (heldTextLength(nodeContent(document)) > longestMarkdown) return tooLong()
   // Two documents the editor holds equal write the same portable markdown (docs/decisions.md §Equality is deep).
   const blocks = reduceBlocks(nodeContent(toEditorNormal(document)), { depth: 0, memo: new Map(), path: [] })
@@ -138,14 +138,14 @@ function portableSequence(blocks: readonly Sourced[], reduction: Reduction): Res
       continue
     }
     // Back on `pending`: a replacement may take the directive form itself.
-    const replacement = block === next.block ? itemBlocks(block, next.path) : [{ block, path: next.path }]
+    const replacement = block === next.block ? listItemBlocks(block, next.path) : [{ block, path: next.path }]
     for (const node of replacement.reverse()) pending.push(node)
   }
   return success(sequence)
 }
 
 // Offsets are the reduced item's, which are the caller's while the item's blocks reduce one to one.
-function itemBlocks(list: AdfNode, path: ConvertErrorPath): Sourced[] {
+function listItemBlocks(list: AdfNode, path: ConvertErrorPath): Sourced[] {
   const blocks: Sourced[] = []
   for (const [index, item] of nodeContent(list).entries()) {
     for (const [offset, block] of nodeContent(item).entries()) blocks.push({ block, path: [...path, 'content', index, 'content', offset] })
@@ -231,11 +231,10 @@ function reduceHeading(node: AdfNode, reduction: Reduction): Result<AdfNode[]> {
 function reduceCodeBlock(node: AdfNode, reduction: Reduction): Result<AdfNode[]> {
   const leaves = inlineLeaves(nodeContent(node), 'paragraph', reduction.path, reduction.depth)
   if (!leaves.ok) return leaves
+  const code = leaves.value.map((leaf) => leaf.text ?? '\n').join('')
   const slot = languageSlot(nodeAttrs(node)['language'], flavourClaims.portable)
-  return boundedThen(joinedWithin(leaves.value.map((leaf) => leaf.text ?? '\n')), (code) => {
-    const block: AdfNode = { content: code === '' ? [] : [text(code)], type: 'codeBlock' }
-    return success([slot.kind === 'fence' ? { ...block, attrs: { language: slot.info } } : block])
-  })
+  const block: AdfNode = { content: code === '' ? [] : [text(code)], type: 'codeBlock' }
+  return success([slot.kind === 'fence' ? { ...block, attrs: { language: slot.info } } : block])
 }
 
 function reduceList(node: AdfNode, reduction: Reduction): Result<AdfNode[]> {
diff --git a/todo.md b/todo.md
index c2976fc..51c9117 100644
--- a/todo.md
+++ b/todo.md
@@ -81,9 +81,7 @@ The line escaper keeps an array element per character twice (`escapings`, `place
 50 bytes a character: one 20-million-character text node took 1.2 GB on Node 24, and one of 80
 million exhausted its 2.2 GB default heap. Twenty million `*` throw `RangeError: Set maximum size
 exceeded`, which `withinEngineLimits` lets through. `losslessMarkdownToAdf` reaches both through a
-directive's CommonMark ask. Bound the line as the blocks are (`joinedWithin`): its segments and its
-escaped output, which today pass V8's longest string only by throwing. Found while shipping item
-106, 2026-10-11.
+directive's CommonMark ask. Found while shipping item 106, 2026-10-11.
 
 ### 103. Fold `unspellable-whitespace` into `unsupported-node-shape`, so a line ending and a null character in a content slot take one code.
 
@@ -215,8 +213,9 @@ Each level of a nested list or quote re-indents its whole text, so the work is t
 text. `losslessMarkdownToAdf` on 3 MB of lazy lines in a list nested 490 levels inside
 `!adf:blockquote` spends about 5 seconds re-spelling it. The same 2 MB split over two items of a
 list nested 480 levels took 11 minutes to refuse on Node 24. A deep subtree past the length bound
-refuses only at the level that passes it, after every level below re-indented its text. The writers
-do the same on such a document. Found while shipping item 106, 2026-10-11.
+refuses only once every level below has re-indented its text, so no test reaches
+`losslessMarkdownToAdf`'s length refusal in seconds: add one with this fix. The writers do the same
+on such a document. Found while shipping item 106, 2026-10-11.
 
 ### 7. Ship HTML: `adfToHtml`, `htmlToAdf`, and markdown to and from HTML composed through ADF, each call named by its flavour.