diff --git a/CHANGELOG.md b/CHANGELOG.md
index db12a66..c187029 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -66,10 +66,10 @@
 - **Breaking:** `adfToLosslessMarkdown` writes a centered, uncaptioned external image whose one
   mark is a link holding only `href` and `title` as `[![alt](url)](href "title")`, where it wrote the
   `mediaSingle` directive. Convert stored markdown per `MIGRATION.md`.
-- **Breaking:** `colwidth` is spelled as its widths joined by commas, `colwidth="340,420"`, where it
-  was a JSON array, and a block's `marks` names each mark with its attributes,
-  `marks="breakout{mode=wide}"`, where it was a JSON array. The JSON array stays only where the
-  flavour does not list a mark's type, one of its attributes, or the type of one's value. Convert stored markdown per `MIGRATION.md`.
+- **Breaking:** `adfToLosslessMarkdown` writes `colwidth` as its widths joined by commas,
+  `colwidth="340,420"`, and a block's `marks` as each mark's type and attributes,
+  `marks="breakout{mode=wide}"`, where it wrote both as JSON arrays, and `losslessMarkdownToAdf`
+  refuses the arrays. Convert stored markdown per `MIGRATION.md`.
 - Fix the time `adfToLosslessMarkdown` and `adfToPortableMarkdown` take on text holding a long run of
   `*`, `_`, `~` or backticks, or a heading ending in a long run of `#`: the time is linear in the
   run, and a run of 20000 `*` takes milliseconds where it took seconds.
diff --git a/MIGRATION.md b/MIGRATION.md
index 24d0e4d..4578288 100644
--- a/MIGRATION.md
+++ b/MIGRATION.md
@@ -67,8 +67,8 @@ function migrateMarkdown(stored: string) {
 | `\:` keeps a directive literal | `\!adf:` keeps a directive literal |
 | `:adf{json="…"}` carrying a link for its `collection`, `id` or `occurrenceKey` | `!adf:link[text]{attrs}` |
 | `::listBreak` between two lists of a kind | no separator: adjacent lists of a kind alternate `- ` and `* `, or `1.` and `1)` |
-| `colwidth="[340,420]"` | `colwidth="340,420"` |
-| `marks="[{\"attrs\":{\"mode\":\"wide\"},\"type\":\"breakout\"}]"` on a block | `marks="breakout{mode=wide}"`; the JSON array stays where the flavour does not list a mark's type, one of its attributes, or the type of one's value |
+| `colwidth="[340,420]"` | `colwidth="340,420"`; a `colwidth` holding no number, or a value that is not a number, rides the `adf:tableCell` or `adf:tableHeader` carry |
+| `marks="[{\"attrs\":{\"mode\":\"wide\"},\"type\":\"breakout\"}]"` on a block | `marks="breakout{mode=wide}"`; `marks` stays a JSON array where the flavour does not list a mark's type or one of its attributes, or a value holds another type than the flavour gives it |
 
 A colon run and `:name[` are plain text now, and `adf` an ordinary code block language; text
 holding an unescaped `!adf:` and a code fence whose info string opens `adf:` are claimed instead.
diff --git a/README.md b/README.md
index 8da3321..5eaf82e 100644
--- a/README.md
+++ b/README.md
@@ -316,11 +316,11 @@ Ping !adf:mention[@Mikael]{id=5b10a2} — !adf:status[In review]{color=yellow} 
 
 - Attributes are `{key=value key2="two words"}`: keys alphabetical, a value bare where it is
   `[A-Za-z0-9_-]+`, else double-quoted with JSON string escaping. A number or JSON value is spelled as
-  canonical JSON, but `colwidth` is its widths joined by commas, `colwidth="340,420"`, and a block's
-  `marks` names each mark with its attributes, `marks="breakout{mode=wide}"`, keeping the JSON array
-  where the flavour does not list a mark's type, one of its attributes, or the type of one's value.
-  An empty `attrs`, `content` or `marks` key is spelled `{attrs=empty}`, `{content=empty}` or
-  `{marks=empty}`.
+  canonical JSON, with two exceptions. `colwidth` joins its widths with commas: `colwidth="340,420"`.
+  A block's `marks` names each mark followed by its attributes, `marks="breakout{mode=wide}"`, and
+  stays a JSON array where the flavour does not list a mark's type or one of its attributes, or a
+  value holds another type than the flavour gives it. An empty `attrs`, `content` or `marks` key is
+  spelled `{attrs=empty}`, `{content=empty}` or `{marks=empty}`.
 - Three reserved names build no node: `!adf:carry` is the inline opaque carry, `!adf:doc {content=none}`
   spells a document holding no `content` key, and `!adf:textBreak{}` parts two adjacent text nodes
   CommonMark would read back as one.
diff --git a/docs/decisions.md b/docs/decisions.md
index e267ace..196ee66 100644
--- a/docs/decisions.md
+++ b/docs/decisions.md
@@ -109,9 +109,10 @@ managers, engineers and support agents. Goal 6. Valid while ADF types these attr
 `colwidth` is its widths joined by commas, `colwidth="340,420"`, where it was a JSON array. A
 block's `marks` names each mark with its `{attrs}`, in order,
 `marks="indentation{level=2} fragment{localId=f1 name=\"Price list\"}"`, chosen over the escaped
-JSON array and an unquoted one. All three writers first sketched a key per mark, `{align=center}`,
-which loses the marks' order and can clash with the node's own attributes. A mark `src/adf/` does not
-type keeps the whole array as JSON, the general form (§Readable spellings take the `try` prefix).
+JSON array and the JSON array unquoted. All three writers first sketched a key per mark,
+`{align=center}`, which loses the marks' order and can clash with the node's own attributes. Where
+`src/adf/` does not type a mark or one of its attributes, or a value holds another type, the whole
+array stays JSON, the general form (§Readable spellings take the `try` prefix).
 The grammar: `spec/flavour.md` §Block nodes.
 
 ## Empty markdown is a document of no blocks
diff --git a/spec/flavour.md b/spec/flavour.md
index dbd2118..2cd9e63 100644
--- a/spec/flavour.md
+++ b/spec/flavour.md
@@ -204,20 +204,22 @@ node the emitter would have written as CommonMark is a named error.
 
 Each section lists attributes as `name (type)`. A parenthesized value set documents what real
 payloads hold; the type stays string and any value round-trips verbatim. Values map to attrs by
-type: strings verbatim, numbers and booleans in canonical JSON spelling — quoted where not bare
-(`width="33.33"`) — `numbers`, a list of one number or more, as those spellings joined by commas
-(`colwidth="340,420"`), and `json` values as the inline carry's serialization (compact, keys
-sorted), quoted, `-0` spelled `-0`. `losslessMarkdownToAdf` builds an `attrs`, `content` or `marks` key only
-where the markdown spells one, an empty one through its reserved key (Attributes), so a document
+type: strings verbatim; numbers and booleans in canonical JSON spelling, quoted where not bare
+(`width="33.33"`); `numbers`, a list of one number or more, as those spellings joined by commas
+(`colwidth="340,420"`); and `json` values as the inline carry's serialization (compact, keys
+sorted), quoted. `-0` is spelled `-0`. `losslessMarkdownToAdf` builds an `attrs`, `content` or
+`marks` key only where the markdown spells one, an empty one through its reserved key (Attributes), so a document
 reads back deep-equal (`docs/decisions.md` §Equality is deep). A node CommonMark spells takes the
 directive form to hold an empty key.
 
-Marks on a block node ride the reserved attribute key `marks`: each mark's type followed by its
-`{attrs}` spelled as a directive's, one space apart in the array's order, and `marks=empty` where
-the array is empty: `!adf:layoutSection {marks="breakout{mode=wide}"}`,
-`!adf:paragraph {marks="indentation{level=2} fragment{localId=f1 name=\"Price list\"}"}`. Where §Marks
-does not list a mark's type, one of its attributes, or the type of one's value, the whole array is
-a `json` value instead: `marks="[{\"attrs\":{\"color\":\"#fff\"},\"type\":\"backgroundColor\"}]"`.
+Marks on a block node ride the reserved attribute key `marks`. It holds the marks in the array's
+order, one space apart, each as its type followed by its `{attrs}` as a directive spells them:
+`!adf:layoutSection {marks="breakout{mode=wide}"}`,
+`!adf:paragraph {marks="indentation{level=2} fragment{localId=f1 name=\"Price list\"}"}`. Where
+§Marks does not list a mark's type or one of its attributes, or a value holds another type than
+§Marks gives it, the whole array is a `json` value instead:
+`marks="[{\"attrs\":{\"color\":\"#fff\"},\"type\":\"backgroundColor\"}]"`. An empty array is
+`marks=empty`.
 A section saying its body is inline takes at most one paragraph, whose inline content becomes
 the node's `content`; any other body is a named error, and an empty pair is a node holding none.
 
@@ -555,9 +557,9 @@ carrying an identical mark, attributes included, at that depth: `attrs: {}` diff
 and a directive spells it `{attrs=empty}`. A run breaks at every node the emitter carries, so no
 emitted carry sits inside a mark spelling.
 
-An inline node whose marks no nesting spells — a hard break holding any mark, a mark type the inline
-list above does not hold, an attrs key its spelling does not list, a value that is not the spelling's type, an attribute
-the spelling needs and the mark lacks, an empty `attrs` on a mark CommonMark spells, an order
+An inline node whose marks no nesting spells — a hard break holding any mark, a mark type the first
+list above does not hold, an attrs key its spelling does not list, a value that is not the
+spelling's type, an attribute the spelling needs and the mark lacks, an empty `attrs` on a mark CommonMark spells, an order
 putting a code span outside another mark, `code` over anything but a text node holding text, or over
 text holding a line ending or a null character, or a spelling CommonMark's flanking rules cannot
 open or close where the run sits (`un**-real**istic`), or one CommonMark's matching pairs elsewhere
diff --git a/src/adf/mark-attributes.ts b/src/adf/mark-attributes.ts
index 93e45d3..db24e2e 100644
--- a/src/adf/mark-attributes.ts
+++ b/src/adf/mark-attributes.ts
@@ -1,6 +1,5 @@
 import type { AttributeVocabulary } from './attribute-vocabulary.ts'
 
-// Marks only a block's marks key holds, so no inline spelling names them.
 export const blockMarkAttributes = {
   alignment: { align: 'string' },
   breakout: { mode: 'string', width: 'number' },
diff --git a/src/markdown/block-directive.ts b/src/markdown/block-directive.ts
index aee1bd3..ad5378f 100644
--- a/src/markdown/block-directive.ts
+++ b/src/markdown/block-directive.ts
@@ -41,7 +41,7 @@ export function markValues(marks: readonly AdfMark[]): JsonValue {
   return marks.map((mark) => (mark.attrs === undefined ? { type: mark.type } : { attrs: mark.attrs, type: mark.type }))
 }
 
-// spec/flavour.md, Block nodes: each mark by name, else the whole array as JSON, `undefined` where that array nests past largestNesting.
+// `undefined` where the JSON array nests past largestNesting.
 export function spellBlockMarks(marks: readonly AdfMark[]): string | undefined {
   const named: string[] = []
   for (const mark of marks) {
diff --git a/src/markdown/mark-spellings.ts b/src/markdown/mark-spellings.ts
index 7cad91f..b3c9bc2 100644
--- a/src/markdown/mark-spellings.ts
+++ b/src/markdown/mark-spellings.ts
@@ -74,7 +74,7 @@ export function spellMarkAttributes(mark: AdfMark, spelling: MarkSpelling): stri
   return emptyKeys(mark).length > 0 && spelling.kind !== 'directive' ? undefined : spellMarkVocabulary(mark, spelling.attributes)
 }
 
-// `undefined` where an attribute is one the vocabulary does not type.
+// `undefined` where the vocabulary lacks an attribute or types its value otherwise.
 export function spellMarkVocabulary(mark: AdfMark, vocabulary: AttributeVocabulary): string | undefined {
   const pairs = vocabularyPairs(nodeAttrs(mark), vocabulary, [])
   return pairs === undefined ? undefined : spellAttributes([...spellVocabulary(pairs), ...spellEmptyKeys(mark)])
diff --git a/src/markdown/parse/directive-nodes.ts b/src/markdown/parse/directive-nodes.ts
index 218f794..a169c61 100644
--- a/src/markdown/parse/directive-nodes.ts
+++ b/src/markdown/parse/directive-nodes.ts
@@ -132,7 +132,7 @@ function readNamedMark(type: string, text: string, index: number, path: ConvertE
   const name = readDirectiveName(text, index)
   if (name === undefined) return failure('unsupported-node-shape', unnamedMarks(type), path)
   const vocabulary = markVocabularies.get(name)
-  if (vocabulary === undefined) return failure('unsupported-node-shape', `the ${marksAttribute} attribute of ${type} names ${name}, no mark the flavour lists: spell an unlisted mark in the JSON array`, path)
+  if (vocabulary === undefined) return failure('unsupported-node-shape', `the ${marksAttribute} attribute of ${type} names ${name}, no mark the flavour lists: write the marks as their JSON array, marks="[{\\"type\\":\\"${name}\\"}]"`, path)
   const start = index + name.length
   const attributes = text.charAt(start) === '{' ? readAttributes(text, start) : { value: { attributes: new Map<string, DirectiveValue>(), end: start } }
   if (attributes.fault !== undefined) {
@@ -145,7 +145,7 @@ function readNamedMark(type: string, text: string, index: number, path: ConvertE
 }
 
 function unnamedMarks(type: string): string {
-  return `the ${marksAttribute} attribute of ${type} names each mark with its {attrs}, one space apart: this one does not`
+  return `the ${marksAttribute} attribute of ${type} names its marks one space apart, each as its type and any {attrs}: this one does not`
 }
 
 function namedNode(type: string, attrs: AdfAttributes, marks: readonly AdfMark[] | undefined, empty: ReadonlySet<EmptyKey>): AdfNode {
diff --git a/src/markdown/parse/markdown-to-adf.test.ts b/src/markdown/parse/markdown-to-adf.test.ts
index cb2c58a..908f5e7 100644
--- a/src/markdown/parse/markdown-to-adf.test.ts
+++ b/src/markdown/parse/markdown-to-adf.test.ts
@@ -550,7 +550,7 @@ test('reads the reserved marks key as a JSON array where a mark is one the table
 
 test('names the marks key no marks read back from', () => {
   const array = 'unsupported-node-shape: the marks attribute of rule is its marks array in canonical JSON: this one is not'
-  const named = 'unsupported-node-shape: the marks attribute of rule names each mark with its {attrs}, one space apart: this one does not'
+  const named = 'unsupported-node-shape: the marks attribute of rule names its marks one space apart, each as its type and any {attrs}: this one does not'
   assert.equal(content(losslessMarkdownToAdf('!adf:rule {marks="[]"}\n')), array)
   assert.equal(content(losslessMarkdownToAdf('!adf:rule {marks="[1]"}\n')), array)
   assert.equal(content(losslessMarkdownToAdf('!adf:rule {marks="{}"}\n')), named)
@@ -562,7 +562,7 @@ test('names the marks key no marks read back from', () => {
   assert.equal(content(losslessMarkdownToAdf('!adf:rule {marks="breakout{mode=wide"}\n')), inBreakout('the {attrs} closing brace is missing'))
   assert.equal(content(losslessMarkdownToAdf('!adf:rule {marks="em{attrs=empty}strong"}\n')), named)
   assert.equal(content(losslessMarkdownToAdf('!adf:rule {marks="em{attrs=x}"}\n')), 'unsupported-node-shape: the reserved key attrs takes only the value empty: this one spells attrs=x')
-  assert.equal(content(losslessMarkdownToAdf('!adf:rule {marks=x}\n')), 'unsupported-node-shape: the marks attribute of rule names x, no mark the flavour lists: spell an unlisted mark in the JSON array')
+  assert.equal(content(losslessMarkdownToAdf('!adf:rule {marks=x}\n')), 'unsupported-node-shape: the marks attribute of rule names x, no mark the flavour lists: write the marks as their JSON array, marks="[{\\"type\\":\\"x\\"}]"')
   assert.equal(content(losslessMarkdownToAdf('!adf:rule {marks="breakout{width=wide}"}\n')), 'unsupported-node-shape: the width attribute of breakout is no number')
   assert.equal(content(losslessMarkdownToAdf('!adf:rule {marks="breakout{bogus=1}"}\n')), 'unsupported-node-shape: breakout holds no bogus attribute: this one spells it')
 })