4.3: todo.md records the settled harness, floors and breaks, and 12's and 13b's follow-ups

AGENTS.md

@@ -229,7 +229,8 @@ editor wrote; the CommonMark spec suite against `markdownToAdf` and `markdownToH
 
 Beside the corpus, properties run over documents generated from the node tables and over generated
 markdown, on a fixed seed in the gate; `PROPERTY_RUNS=<runs>` raises the runs and randomizes the
-seed for local digging, and a counterexample found becomes a round-trip fixture.
+seed for local digging, and a counterexample found becomes a round-trip fixture. The generators and
+run parameters properties share live in `src/property-harness.ts`, outside the build and coverage.
 
 `spec/flavour.md` is read as a source too, so the node tables cannot drift from the prose they
 copy: each `- ` bullet in `## Block nodes`, `## Inline nodes` and `## Marks` declares the nodes

corpus/round-trip/combinations/link-definition-carry.json

@@ -0,0 +1,45 @@
+{
+  "content": [
+    {
+      "content": [
+        {
+          "marks": [
+            {
+              "attrs": {
+                "href": "/u"
+              },
+              "type": "link"
+            },
+            {
+              "type": "code"
+            }
+          ],
+          "text": "]: a",
+          "type": "text"
+        }
+      ],
+      "type": "paragraph"
+    },
+    {
+      "content": [
+        {
+          "attrs": {
+            "timestamp": "]:a"
+          },
+          "marks": [
+            {
+              "attrs": {
+                "href": "/u"
+              },
+              "type": "link"
+            }
+          ],
+          "type": "date"
+        }
+      ],
+      "type": "paragraph"
+    }
+  ],
+  "type": "doc",
+  "version": 1
+}

corpus/round-trip/combinations/link-definition-carry.md

@@ -0,0 +1,3 @@
+:adf{json="{\"marks\":[{\"attrs\":{\"href\":\"/u\"},\"type\":\"link\"},{\"type\":\"code\"}],\"text\":\"]: a\",\"type\":\"text\"}"}
+
+:adf{json="{\"attrs\":{\"timestamp\":\"]:a\"},\"marks\":[{\"attrs\":{\"href\":\"/u\"},\"type\":\"link\"}],\"type\":\"date\"}"}

package.json

@@ -23,7 +23,7 @@
   },
   "scripts": {
     "build": "tsc -p tsconfig.build.json",
-    "test": "node --test --experimental-test-coverage --test-coverage-exclude=\"src/**/*.test.ts\" --test-coverage-exclude=src/property-generators.ts --test-coverage-branches=98 --test-coverage-functions=100 --test-coverage-lines=100 \"src/**/*.test.ts\"",
+    "test": "node --test --experimental-test-coverage --test-coverage-exclude=\"src/**/*.test.ts\" --test-coverage-exclude=src/property-harness.ts --test-coverage-branches=98 --test-coverage-functions=100 --test-coverage-lines=100 \"src/**/*.test.ts\"",
     "typecheck": "tsc --noEmit && tsc --noEmit -p tsconfig.build.json"
   },
   "devDependencies": {

spec/flavour.md

@@ -56,8 +56,9 @@ normalizes to it through the round-trip.
   the leading delimiter of a construct that would otherwise open, re-scan from there, and repeat.
   A backtick run escapes whole, and a lone backtick escapes wherever an escaped one follows it in
   the same inline content: CommonMark reads no escape inside a code span, so `` \` `` closes one.
-  A paragraph's opening `[` escapes wherever its line reads as a link reference definition, which
+  Where a paragraph opens with what reads as a link reference definition, which resolves before
-  resolves before any inline construct binds: a `]` inside a code span or `{attrs}` counts.
+  any inline construct binds (a `]` inside a code span or `{attrs}` counts), an opening text `[`
+  escapes and an opening link's nodes ride the carry.
   An emphasis delimiter run in text escapes where CommonMark can open **or** close with it, so
   `*not emphasis*` is `\*not emphasis\*` — no delimiter the emitter did not write reaches the
   matching below, which is what lets the emitter decide its own pairings.

src/adf-property.test.ts

@@ -2,7 +2,7 @@ import fc from 'fast-check'
 import assert from 'node:assert/strict'
 import test from 'node:test'
 
-import { adfDocument, propertyRuns, propertyTimeout } from './property-generators.ts'
+import { adfDocument, propertyRuns, propertyTimeout } from './property-harness.ts'
 import { adfToMarkdown } from './markdown/emit/adf-to-markdown.ts'
 import { markdownToAdf } from './markdown/parse/markdown-to-adf.ts'
 import { toEditorNormal } from './adf/editor-normal.ts'

src/markdown-property.test.ts

@@ -5,7 +5,8 @@ import test from 'node:test'
 import type { Arbitrary, DepthIdentifier } from 'fast-check'
 import type { AttributeVocabulary } from './adf/attribute-vocabulary.ts'
 import type { JsonValue } from './json-value.ts'
-import { adfDocument, attributes, jsonKey, jsonValue, markdownPieces, propertyRuns, propertyTimeout, textOf } from './property-generators.ts'
+import type { Result } from './result.ts'
+import { adfDocument, attributes, jsonKey, jsonValue, markdownPieces, propertyRuns, propertyTimeout, textOf } from './property-harness.ts'
 import { adfToMarkdown } from './markdown/emit/adf-to-markdown.ts'
 import { blockArgument } from './markdown/block-directive-arguments.ts'
 import { blockDirectives } from './adf/block-directives.ts'
@@ -27,6 +28,13 @@ type Choice = { arbitrary: Arbitrary<string>; hostile?: true; weight: number }
 
 type Edit = [at: number, removed: number, inserted: string]
 
+type InlineMarkdown = { destination: Arbitrary<string>; inlines: Arbitrary<string>; label: Arbitrary<string>; oneLine: Arbitrary<string>; text: Arbitrary<string>; word: Arbitrary<string> }
+
+type LeafMarkdown = { fencedCode: Arbitrary<string>; leafBlock: Arbitrary<string> }
+
+const directiveShapedFloor = 350
+const directiveSpelling = /(?<!\\):[a-z][A-Za-z0-9]*[[{]|^[\t >*+.)0-9-]*::+[a-z]/m
+const fixpointFloor = 600
 const gateRuns = 1000
 
 const vocabularies = [...Object.values(blockDirectives).map((directive) => directive.attributes), ...Object.values(inlineDirectives).map((directive) => directive.attributes), ...Object.values(markAttributes)]
@@ -179,7 +187,11 @@ const indentDrift = fc.oneof({ arbitrary: fc.constant(0), weight: 6 }, { arbitra
 const closerDrift = fc.option(fc.integer({ max: 5, min: 2 }), { freq: 6 })
 
 function markdownOf(hostile: boolean): Arbitrary<string> {
-  const blockDepth = fc.createDepthIdentifier()
+  const inline = inlineMarkdown(hostile)
+  return blockMarkdown(hostile, inline, leafBlocks(hostile, inline))
+}
+
+function inlineMarkdown(hostile: boolean): InlineMarkdown {
   const inlineDepth = fc.createDepthIdentifier()
   const text = hostile ? fc.oneof(cleanText, textOf(0)) : cleanText
   const word = fc.oneof({ arbitrary: prose, weight: 3 }, { arbitrary: text.filter((held) => held !== ''), weight: 2 })
@@ -228,8 +240,10 @@ function markdownOf(hostile: boolean): Arbitrary<string> {
     ),
     inlines: fc.array(tie('inline'), { depthIdentifier: inlineDepth, maxLength: 4, minLength: 1 }).map((parts) => parts.join('')),
   }))
+  return { destination, inlines, label, oneLine: inlines.map((held) => held.replace(/[\n\r]/g, ' ')), text, word }
+}
 
-  const oneLine = inlines.map((held) => held.replace(/[\n\r]/g, ' '))
+function leafBlocks(hostile: boolean, { destination, inlines, label, oneLine, text, word }: InlineMarkdown): LeafMarkdown {
   const fencedCode = fc
     .tuple(
       fc.constantFrom('```', '```', '~~~', '````', '``'),
@@ -287,7 +301,11 @@ function markdownOf(hostile: boolean): Arbitrary<string> {
     },
     { arbitrary: fc.constantFrom(':::', '::', '::::', ':::panel', '::: panel', ':::panel info extra'), hostile: true, weight: 1 },
   ])
+  return { fencedCode, leafBlock }
+}
 
+function blockMarkdown(hostile: boolean, { inlines, oneLine }: InlineMarkdown, { fencedCode, leafBlock }: LeafMarkdown): Arbitrary<string> {
+  const blockDepth = fc.createDepthIdentifier()
   const { blocks } = fc.letrec<{ block: string; blocks: string }>((tie) => {
     const bodyByModel = { block: fc.oneof(tie('blocks'), fc.constant('')), code: fencedCode, inline: fc.oneof(oneLine, fc.constant('')) }
     const tableDirectives = Object.entries(blockDirectives).map(([name, directive]) => {
@@ -346,10 +364,10 @@ function markdownOf(hostile: boolean): Arbitrary<string> {
 const cleanMarkdown = markdownOf(false)
 const hostileMarkdown = markdownOf(true)
 
-const canonical = adfDocument.map((document) => {
+const canonical = adfDocument
-  const emitted = adfToMarkdown(document)
+  .map((document) => adfToMarkdown(document))
-  return emitted.ok ? emitted.value : ''
+  .filter((emitted): emitted is Extract<Result<string>, { ok: true }> => emitted.ok)
-})
+  .map((emitted) => emitted.value)
 
 function edited(markdown: string, edits: readonly Edit[]): string {
   let text = markdown
@@ -375,12 +393,17 @@ const document = fc
   .map(([held, ending, trailing]) => `${held}${trailing}`.replaceAll('\n', ending))
 
 test('generated markdown refuses, or what it parses to refuses to emit, or its spelling reads back and spells itself', { timeout: propertyTimeout }, () => {
+  const parameters = propertyRuns(gateRuns)
+  let directiveShaped = 0
+  let fixpoints = 0
   fc.assert(
     fc.property(document, (input) => {
       const parsed = markdownToAdf(input)
       if (!parsed.ok) return
       const emitted = adfToMarkdown(parsed.value)
       if (!emitted.ok) return
+      fixpoints += 1
+      if (directiveSpelling.test(emitted.value)) directiveShaped += 1
       const read = markdownToAdf(emitted.value)
       assert.ok(read.ok, read.ok ? '' : `${read.error.code}: ${read.error.message} — reading ${JSON.stringify(emitted.value)}`)
       assert.deepEqual(toEditorNormal(read.value), toEditorNormal(parsed.value), `reading ${JSON.stringify(emitted.value)}`)
@@ -388,7 +411,10 @@ test('generated markdown refuses, or what it parses to refuses to emit, or its s
       assert.ok(respelled.ok, respelled.ok ? '' : `${respelled.error.code}: ${respelled.error.message} — spelling ${JSON.stringify(emitted.value)} again`)
       assert.equal(respelled.value, emitted.value)
     }),
-    propertyRuns(gateRuns),
+    parameters,
   )
+  if (parameters.seed === undefined) return
+  assert.ok(fixpoints >= fixpointFloor, `${fixpoints} of ${gateRuns} runs reached the fixpoint, under the floor of ${fixpointFloor}`)
+  assert.ok(directiveShaped >= directiveShapedFloor, `${directiveShaped} runs reaching the fixpoint spelled a directive, under the floor of ${directiveShapedFloor}`)
 })
 

src/markdown/emit/inline-line.ts

@@ -292,6 +292,6 @@ function emitLink(nodes: readonly AdfNode[], mark: AdfMark, depth: number, range
   if (!inner.ok) return inner
   if (inner.value.carry !== undefined) return inner
   const spelledTarget: InlineSegment = context.bracketed ? { escaping: 'bracketed-link-target', text: escapeUnbalanced(target.value, '[', ']') } : syntax(target.value)
-  return success({ segments: [syntax('['), ...inner.value.segments, syntax(']('), spelledTarget, syntax(')')] })
+  return success({ segments: [{ escaping: 'none', nodes: range, text: '[' }, ...inner.value.segments, syntax(']('), spelledTarget, syntax(')')] })
 }
 

src/markdown/emit/line-escaping.ts

@@ -14,7 +14,8 @@ export type NodeRange = { first: number; last: number }
 
 export type InlineSegment =
   | { emphasis: EmphasisRole; escaping: 'none'; nodes: NodeRange; text: string }
-  | { emphasis?: undefined; escaping: InlineEscaping; text: string }
+  | { emphasis?: undefined; escaping: 'none'; nodes: NodeRange; text: string }
+  | { emphasis?: undefined; escaping: InlineEscaping; nodes?: undefined; text: string }
 
 export type AssembledLine = { line: string; unspellableRun: NodeRange | undefined }
 
@@ -75,8 +76,12 @@ function escape(segments: readonly InlineSegment[], container: LineContainer): A
     placements.push(output.length)
     output += scan.charAt(index)
   }
-  const line = container === 'paragraph' && opensLinkDefinition(output) ? `\\${output}` : output
+  if (container === 'paragraph' && opensLinkDefinition(output)) {
-  return { line, unspellableRun: unspellableRun(segments, output, placements) }
+    const opener = segments[0]?.nodes
+    if (opener !== undefined) return { line: output, unspellableRun: opener }
+    return { line: `\\${output}`, unspellableRun: unspellableRun(segments, output, placements) }
+  }
+  return { line: output, unspellableRun: unspellableRun(segments, output, placements) }
 }
 
 function escapedIndexes(scan: string, escapings: readonly InlineEscaping[], container: LineContainer): Set<number> {

todo.md

@@ -59,6 +59,18 @@ proves 12, 13 spells 11's gaps in 12's grammar, and 12 rewrites code 4b and 4c c
   - [ ] **4.3 — The markdown property.** Generated markdown through `markdownToAdf` never throws,
         and the runs fit the budget; where it parses and `adfToMarkdown` spells the result, that
         spelling parses and emits to itself byte for byte (§2).
+        **Settled** (the maintainer, 2026-09-15): the generators and run parameters 4.2 and 4.3
+        share live in one test-only module in `src/`, kept out of the build and coverage, with
+        10c's properties as its third user. Under the gate seed the property asserts floors on the
+        runs reaching the fixpoint and on the directive-shaped ones. It lands when hunts of several
+        hundred thousand runs per engine pass clean, since the breaks hit once per ~150,000 runs,
+        past a 10,000-run bar. Two breaks, both shipped in `0.1.0`, are fixed inside it. An escaped
+        backtick closed an earlier lone backtick's code span, since CommonMark reads no escape
+        inside one: a backtick run now escapes whole, and a lone backtick escapes wherever an
+        escaped one follows it in the same inline content. A paragraph's opening read as a link
+        reference definition across a `]` the emitter spelled: the emitter now escapes the opening
+        `[` exactly when the parser's own definition reader accepts the paragraph, and a link
+        opening it rides the carry until 13b.
   - [x] **4.4 — The real payloads.**
 - [ ] **4b — The block walk's retry (`0.2.0`).** `emitBlock` walks a subtree twice wherever
       `readableBlock` reads it whole and then gives up — a list item whose first line reads back
@@ -237,7 +249,7 @@ proves 12, 13 spells 11's gaps in 12's grammar, and 12 rewrites code 4b and 4c c
       `src/adf/block-directives.ts` + `inline-directives.ts`, `src/markdown/`'s
       `directive-syntax.ts`, `opaque-carry.ts` and the `emit/` + `parse/` readers, every corpus
       fixture (round-trip, normalization and `errors/`), the prose reader over `spec/flavour.md`,
-      and the README's examples.
+      the markdown property's generator, and the README's examples.
       **Settled** (the maintainer, 2026-09-13):
       - A line opening `!adf:name` is a block line when a space or the line's end follows the name,
         and a paragraph when `[` or `{` does. Claiming stays syntactic and structure comes from the
@@ -292,7 +304,9 @@ proves 12, 13 spells 11's gaps in 12's grammar, and 12 rewrites code 4b and 4c c
         exceptions it cures re-derived, and the README's code table and its "not every document
         converts back" guarantee following; the gap list is empty. A round-trip fixture holds the
         shape 4.2's review left refused until then: an autolink-shaped link under a directive mark
-        whose href holds `\:name{`.
+        whose href holds `\:name{`. A link opening a paragraph whose opening reads as a link
+        reference definition, which 4.3 leaves riding the carry, takes the directive link too, with
+        its round-trip fixture (the maintainer, 2026-09-15).
 
 ## The ADF inventory to cover
 

tsconfig.build.json

@@ -27,6 +27,6 @@
     "forceConsistentCasingInFileNames": true,
     "skipLibCheck": true
   },
-  "exclude": ["src/**/*.test.ts", "src/property-generators.ts"],
+  "exclude": ["src/**/*.test.ts", "src/property-harness.ts"],
   "include": ["src"]
 }