diff --git a/src/markdown/portable/block-spelling.ts b/src/markdown/portable/block-spelling.ts
index 878649a..a67093f 100644
--- a/src/markdown/portable/block-spelling.ts
+++ b/src/markdown/portable/block-spelling.ts
@@ -7,7 +7,6 @@ import { emitBlock, joinBlocks, quotedBlocks, spelledList, walkBlocks } from '..
 import { emitInlineLine } from '../emit/inline-line.ts'
 import { failure, success } from '../../result.ts'
 import { isTaskItem } from '../../adf/block-nodes.ts'
-import { largestNesting } from '../../nesting.ts'
 import { nodeAttrs, nodeContent } from '../../adf/document.ts'
 
 const portableBlockWriters: FlavourBlockWriters = {
@@ -41,18 +40,20 @@ function headed(head: string): (body: BlockText) => BlockText {
 
 function tryTaskList(node: AdfNode, path: ConvertErrorPath, depth: number, writing: Writing): Result<EmittedBlock> {
   const items: PlacedBlock[][] = []
-  let headroom = largestNesting - depth - 1
+  // The portable reduction leaves a task list opening with a task, so `item` is set before any child nests in it.
+  let item: PlacedBlock[] = []
   // A child other than a task nests in the task before it.
   for (const [index, child] of nodeContent(node).entries()) {
     const task = isTaskItem(child)
     const walk = task ? taskBlocks(child, [...path, 'content', index], depth + 1, writing) : placedBlock(child, [...path, 'content', index], depth + 1, writing)
     if (!walk.ok) return walk
-    headroom = Math.min(headroom, walk.value.headroom)
-    const previous = items.at(-1)
-    if (task || previous === undefined) items.push([...walk.value.blocks])
-    else for (const block of walk.value.blocks) previous.push(block)
+    if (task) {
+      item = []
+      items.push(item)
+    }
+    for (const block of walk.value.blocks) item.push(block)
   }
-  const list = spelledList(items.map((blocks) => joinBlocks(blocks, 'list-item')), undefined, headroom)
+  const list = spelledList(items.map((blocks) => joinBlocks(blocks, 'list-item')), undefined, Number.POSITIVE_INFINITY)
   // The portable reduction leaves no task a list item cannot hold: a directive here would break the flavour.
   return list === undefined ? failure('unsupported-node-shape', 'a task holds blocks no list item spells', path) : success(list)
 }
diff --git a/todo.md b/todo.md
index 2be7206..05cab4d 100644
--- a/todo.md
+++ b/todo.md
@@ -13,7 +13,7 @@
 | ID | Release | Blocked by | Exempt | Item | L | E | I | R | S | Moves | Score |
 |---|---|---|---|---|---|---|---|---|---|---|---|
 | 153 | 0.4.0 |  | question | **Decide whether `src/markdown/` root may import `emit/`, `parse/` or `portable/`, and hold the answer in `.oxlintrc.json` and §The source parts by ADF and format.** | 1 | 2 | 2 | 3 | 2 | code health by 3 | 26.2 |
-| 175 | 0.4.0 |  |  | **Delete the guards in `tryTaskList` that `reduceToPortable` makes unreachable, once a test shows `adfToPortableMarkdown` reaches none of them.** | 1 | 1 | 1 | 1 | 2 | code health by 2 | 17.4 |
+| 175 | 0.4.0 |  |  | **Delete the `'a task holds blocks no list item spells'` failure and the child paths in `tryTaskList`, once `spelledList` yields a list the portable reduction can never refuse.** | 1 | 1 | 1 | 1 | 2 | code health by 2 | 17.4 |
 | 176 | 0.4.0 |  |  | **Delete `runEdge`'s `standing === 'moves'` give-up, and any code only it needs, once a test or an argument shows `runEdge` never reaches it, or else pin the case with a hand-worked line.** | 1 | 1 | 2 | 2 | 2 | code health by 2 | 17.4 |
 | 45 | 0.4.0 |  | defect | **Replace `isAdfDocument` with a reader returning `Result<AdfDocument>`.** | 2 | 1 | 3 | 4 | 3 | 1 by 2 | 13.1 |
 | 127 | 0.4.0 |  | principle | **Hold what `entity-references.test.ts`, `json-text.test.ts` and `result.test.ts` check by asserting outcomes, so none reads source text.** | 2 | 2 | 1 | 3 | 3 | code health by 2 | 13.1 |
@@ -72,14 +72,13 @@ a paragraph opening with a spellable `!adf:link` (§Nothing recurses unbounded).
 `src/markdown/**` bans only `html/`; banning `emit/`, `parse/` and `portable/` for the root's own
 files, with its `ci.sh` probe, extends the decision.
 
-### 175. Delete the guards in `tryTaskList` that `reduceToPortable` makes unreachable, once a test shows `adfToPortableMarkdown` reaches none of them.
+### 175. Delete the `'a task holds blocks no list item spells'` failure and the child paths in `tryTaskList`, once `spelledList` yields a list the portable reduction can never refuse.
 
-`reduceToPortable` runs first and turns a task list opening with a non-task into a bullet list. So
-`tryTaskList` (`portable/block-spelling.ts`) never sees `previous === undefined`, and its
-`'a task holds blocks no list item spells'` failure has no test. The `path` it passes to
-`taskBlocks` and `placedBlock`, and its `Math.min` of `headroom`, change no output, since the
-nesting refusal's path comes from `reduceToPortable`. Found by mutation testing for item 128,
-2026-11-08.
+`reduceToPortable` runs first, so `adfToPortableMarkdown` never reaches `tryTaskList`'s
+(`portable/block-spelling.ts`) failure; no test reaches it either. It stays because `spelledList`
+returns `undefined` for the blocks a list item cannot hold, and the type has no cast to drop it.
+The `path` it passes to `taskBlocks` and `placedBlock` changes no output, since the nesting
+refusal's path comes from `reduceToPortable`. Found by mutation testing for item 128, 2026-11-08.
 
 ### 176. Delete `runEdge`'s `standing === 'moves'` give-up, and any code only it needs, once a test or an argument shows `runEdge` never reaches it, or else pin the case with a hand-worked line.