@@ -0,0 +1,24 @@
+---
+"@objectstack/spec": minor
+---
+
+feat(spec)!: a form section's `columns` has no default — undeclared, the density is the renderer's (by available width); declared, it is the author's ceiling
+
+Clause-②: no
+
+**BREAKING:** a parsed form section without `columns` no longer carries `columns: 1`. `FormSectionSchema.columns` drops `.default(1)`: the key stays optional with values `1`–`4`, and the string spellings `'1'`–`'4'` still parse to the number.
+
+| A form section authored as | Parsed before | Parsed now |
+|:---|:---|:---|
+| `{ fields: [...] }` (no `columns`) | `columns: 1` | no `columns` key |
+| `{ columns: 2, fields: [...] }` | `columns: 2` | `columns: 2` (unchanged) |
+| `{ columns: '3', fields: [...] }` | `columns: 3` | `columns: 3` (unchanged) |
+
+The two meanings, stated on the schema's describe and docblock:
+
+- **Declared** — the author's ceiling: at most that many fields per row where the container is wide enough. A renderer collapses it on narrow containers.
+- **Undeclared** — the renderer's choice, by available width. After parse a renderer can now tell "the author said nothing" apart from "the author asked for one column", which the old default erased. No pixel or breakpoint value enters the protocol.
+
+Nothing to rewrite: every input accepted before is accepted now with the same declared value, and none refused before is accepted. A section that must stay single-column on a wide container declares `columns: 1`. A consumer that reads a parsed section's `columns` treats an absent key as "the renderer decides" rather than as `1`. `FormViewSchema.columns` (the form body) was already optional with no default and is unchanged.
+
+<!-- adr-0087: not-required (no-migration-prescription) no key is removed, renamed or moved and no stored or authored value changes meaning when declared; only the parse-added default for an undeclared key goes away, which no conversion can restore without defeating the change -->
@@ -242,6 +242,12 @@ regions:
   are written in the vocabulary the schemas accept.
 </Callout>
 
+A section's `columns` has no default. Declared, it is the author's **ceiling**:
+at most that many fields per row where the container is wide enough, collapsed
+by the renderer on narrow containers — so `columns: 1` is how to keep a section
+single-column. Undeclared, the density is the **renderer's** choice by available
+width. No pixel or breakpoint value is part of the protocol.
+
 All layouts use a responsive grid that divides space into columns.
 
 ### Basic Grid Layout
 
@@ -322,7 +322,7 @@ Form-view select option — the object-field option shape minus the per-option `
 | **collapsed** | `boolean` | optional (default: `false`) | Whether the section starts closed. Default `false`. ⚠️ `collapsed: true` IMPLIES `collapsible` and is sufficient ON ITS OWN — a section that starts closed always carries the disclosure control that reopens it, and it outranks an explicit `collapsible: false`, so writing `collapsed: true` alone is a correct way to say "collapsed by default". The implication is a renderer rule, never a parse-time rewrite: `{ collapsed: true }` still parses to `collapsible: false, collapsed: true`, so the parsed `collapsible` must never be read as "a control renders". Only `true` is refused on a wizard step (steps do not collapse) and beside `group`, whose field group declares the pair. |
 | **visibleWhen** | `string \| { dialect: Enum<'cel' \| 'cron' \| 'template'>; source: string; ast?: any; meta?: object }` | optional | Visibility predicate (CEL) — section shown only when TRUE. Root: `record` (+ `previous`, `parent`) in runtime forms, or `data` in metadata forms. `current_user` (and the ADR-0068 aliases `user` / `ctx.user` / `os.user`) resolves here too — CLIENT-SIDE only: nothing server-side evaluates a form-view section `visibleWhen`, so a role test here hides the controls and protects no data (declare permission-set field-level security for that), and on the public `/f/:slug` route no host publishes a scope, so the root is unbound and the predicate faults open. No `features.*` on ANY form-view predicate — refused at parse: unbound on the standalone form routes, where the predicate would fault open. |
 | **visibleOn** | `string \| { dialect: Enum<'cel' \| 'cron' \| 'template'>; source: string; ast?: any; meta?: object }` | optional | [DEPRECATED → `visibleWhen`] Visibility predicate (CEL). Hides the whole section when false. Normalized to `visibleWhen` at parse. |
-| **columns** | `Enum<'1' \| '2' \| '3' \| '4'> \| 1 \| 2 \| 3 \| 4` | optional (default: `1`) |  |
+| **columns** | `Enum<'1' \| '2' \| '3' \| '4'> \| 1 \| 2 \| 3 \| 4` | optional | Fields per row, 1–4 ('1'–'4' parse to the number). Declared: the author's ceiling — at most that many per row where the container is wide enough; a renderer collapses it on narrow containers. Undeclared: the renderer's choice by available width — the parse adds no default, so declare `columns: 1` to keep a section single-column. |
 | **pane** | `Enum<'primary' \| 'secondary'>` | optional | Split pane this section renders in (split forms only; a parse error elsewhere). Omitted → first section 'primary', others 'secondary'. |
 | **group** | `string` | optional | Field group key (snake_case) whose members and presentation this section inherits, from the bound object's `fieldGroups` (ADR-0085 §5 `deriveFieldGroupLayout`). Mutually exclusive with `fields`, and with every key the group itself declares (`name`, `label`, `description`, `collapsible`, `collapsed`, `visibleWhen`/`visibleOn`). Not valid on a wizard step. Must name a declared group — checked by reference diagnostics. |
 | **fields** | `(string \| { field: string; type?: Enum<'text' \| 'textarea' \| 'email' \| 'url' \| 'phone' \| 'password' \| 'secret' \| …>; options?: object[]; reference?: string; … })[]` | optional |  |
@@ -446,7 +446,7 @@ Form-view select option — the object-field option shape minus the per-option `
 | **collapsed** | `boolean` | optional (default: `false`) | Whether the section starts closed. Default `false`. ⚠️ `collapsed: true` IMPLIES `collapsible` and is sufficient ON ITS OWN — a section that starts closed always carries the disclosure control that reopens it, and it outranks an explicit `collapsible: false`, so writing `collapsed: true` alone is a correct way to say "collapsed by default". The implication is a renderer rule, never a parse-time rewrite: `{ collapsed: true }` still parses to `collapsible: false, collapsed: true`, so the parsed `collapsible` must never be read as "a control renders". Only `true` is refused on a wizard step (steps do not collapse) and beside `group`, whose field group declares the pair. |
 | **visibleWhen** | `string \| { dialect: Enum<'cel' \| 'cron' \| 'template'>; source: string; ast?: any; meta?: object }` | optional | Visibility predicate (CEL) — section shown only when TRUE. Root: `record` (+ `previous`, `parent`) in runtime forms, or `data` in metadata forms. `current_user` (and the ADR-0068 aliases `user` / `ctx.user` / `os.user`) resolves here too — CLIENT-SIDE only: nothing server-side evaluates a form-view section `visibleWhen`, so a role test here hides the controls and protects no data (declare permission-set field-level security for that), and on the public `/f/:slug` route no host publishes a scope, so the root is unbound and the predicate faults open. No `features.*` on ANY form-view predicate — refused at parse: unbound on the standalone form routes, where the predicate would fault open. |
 | **visibleOn** | `string \| { dialect: Enum<'cel' \| 'cron' \| 'template'>; source: string; ast?: any; meta?: object }` | optional | [DEPRECATED → `visibleWhen`] Visibility predicate (CEL). Hides the whole section when false. Normalized to `visibleWhen` at parse. |
-| **columns** | `Enum<'1' \| '2' \| '3' \| '4'> \| 1 \| 2 \| 3 \| 4` | optional (default: `1`) |  |
+| **columns** | `Enum<'1' \| '2' \| '3' \| '4'> \| 1 \| 2 \| 3 \| 4` | optional | Fields per row, 1–4 ('1'–'4' parse to the number). Declared: the author's ceiling — at most that many per row where the container is wide enough; a renderer collapses it on narrow containers. Undeclared: the renderer's choice by available width — the parse adds no default, so declare `columns: 1` to keep a section single-column. |
 | **pane** | `Enum<'primary' \| 'secondary'>` | optional | Split pane this section renders in (split forms only; a parse error elsewhere). Omitted → first section 'primary', others 'secondary'. |
 | **group** | `string` | optional | Field group key (snake_case) whose members and presentation this section inherits, from the bound object's `fieldGroups` (ADR-0085 §5 `deriveFieldGroupLayout`). Mutually exclusive with `fields`, and with every key the group itself declares (`name`, `label`, `description`, `collapsible`, `collapsed`, `visibleWhen`/`visibleOn`). Not valid on a wizard step. Must name a declared group — checked by reference diagnostics. |
 | **fields** | `(string \| { field: string; type?: Enum<'text' \| 'textarea' \| 'email' \| 'url' \| 'phone' \| 'password' \| 'secret' \| …>; options?: object[]; reference?: string; … })[]` | optional |  |
@@ -462,7 +462,7 @@ Form-view select option — the object-field option shape minus the per-option `
 | **collapsed** | `boolean` | optional (default: `false`) | Whether the section starts closed. Default `false`. ⚠️ `collapsed: true` IMPLIES `collapsible` and is sufficient ON ITS OWN — a section that starts closed always carries the disclosure control that reopens it, and it outranks an explicit `collapsible: false`, so writing `collapsed: true` alone is a correct way to say "collapsed by default". The implication is a renderer rule, never a parse-time rewrite: `{ collapsed: true }` still parses to `collapsible: false, collapsed: true`, so the parsed `collapsible` must never be read as "a control renders". Only `true` is refused on a wizard step (steps do not collapse) and beside `group`, whose field group declares the pair. |
 | **visibleWhen** | `string \| { dialect: Enum<'cel' \| 'cron' \| 'template'>; source: string; ast?: any; meta?: object }` | optional | Visibility predicate (CEL) — section shown only when TRUE. Root: `record` (+ `previous`, `parent`) in runtime forms, or `data` in metadata forms. `current_user` (and the ADR-0068 aliases `user` / `ctx.user` / `os.user`) resolves here too — CLIENT-SIDE only: nothing server-side evaluates a form-view section `visibleWhen`, so a role test here hides the controls and protects no data (declare permission-set field-level security for that), and on the public `/f/:slug` route no host publishes a scope, so the root is unbound and the predicate faults open. No `features.*` on ANY form-view predicate — refused at parse: unbound on the standalone form routes, where the predicate would fault open. |
 | **visibleOn** | `string \| { dialect: Enum<'cel' \| 'cron' \| 'template'>; source: string; ast?: any; meta?: object }` | optional | [DEPRECATED → `visibleWhen`] Visibility predicate (CEL). Hides the whole section when false. Normalized to `visibleWhen` at parse. |
-| **columns** | `Enum<'1' \| '2' \| '3' \| '4'> \| 1 \| 2 \| 3 \| 4` | optional (default: `1`) |  |
+| **columns** | `Enum<'1' \| '2' \| '3' \| '4'> \| 1 \| 2 \| 3 \| 4` | optional | Fields per row, 1–4 ('1'–'4' parse to the number). Declared: the author's ceiling — at most that many per row where the container is wide enough; a renderer collapses it on narrow containers. Undeclared: the renderer's choice by available width — the parse adds no default, so declare `columns: 1` to keep a section single-column. |
 | **pane** | `Enum<'primary' \| 'secondary'>` | optional | Split pane this section renders in (split forms only; a parse error elsewhere). Omitted → first section 'primary', others 'secondary'. |
 | **group** | `string` | optional | Field group key (snake_case) whose members and presentation this section inherits, from the bound object's `fieldGroups` (ADR-0085 §5 `deriveFieldGroupLayout`). Mutually exclusive with `fields`, and with every key the group itself declares (`name`, `label`, `description`, `collapsible`, `collapsed`, `visibleWhen`/`visibleOn`). Not valid on a wizard step. Must name a declared group — checked by reference diagnostics. |
 | **fields** | `(string \| { field: string; type?: Enum<'text' \| 'textarea' \| 'email' \| 'url' \| 'phone' \| 'password' \| 'secret' \| …>; options?: object[]; reference?: string; … })[]` | optional |  |
 
@@ -261,12 +261,15 @@ describe('#7134 what the save path must NOT change', () => {
     it('[#20051] a form authored with canonical `sections` is stored as authored — no section default, no `sharing.enabled`, no undeclared key', async () => {
         // Re-judged at stage (iv): was "stored byte-identical", with an
         // `isPinned` the form member does not declare riding along. The parse
-        // adds `collapsible` / `collapsed` / `columns` to the section and
-        // `enabled: false` to `sharing`; ruling B stores none of them (ADR-0087's
-        // `storable` rule), and the undeclared `isPinned` is dropped.
+        // adds `collapsible` / `collapsed` to the section and `enabled: false`
+        // to `sharing`; ruling B stores none of them (ADR-0087's `storable`
+        // rule), and the undeclared `isPinned` is dropped. A section's `columns`
+        // has no default: undeclared, the parse adds no key (the renderer picks
+        // the density by available width).
         const authored = flatForm({ sections: [SECTION], isPinned: true });
         const parsed = (ViewMetadataSchema as any).parse(authored);
-        expect(parsed.sections[0]).toMatchObject({ collapsible: false, collapsed: false, columns: 1 });
+        expect(parsed.sections[0]).toMatchObject({ collapsible: false, collapsed: false });
+        expect('columns' in parsed.sections[0]).toBe(false);
         expect(parsed.sharing.enabled).toBe(false);
         const body = await storedViewBody('contact_us', authored);
         const { isPinned: _dropped, ...declared } = authored as Record<string, unknown>;
 
@@ -45,7 +45,6 @@
     "ui/FormField:span = \"auto\"",
     "ui/FormSection:collapsed = false",
     "ui/FormSection:collapsible = false",
-    "ui/FormSection:columns = 1",
     "ui/FormView:type = \"simple\"",
     "ui/GalleryConfig:cardSize = \"medium\"",
     "ui/GalleryConfig:coverFit = \"cover\"",
 
@@ -620,4 +620,27 @@ export const DEFAULT_CHANGES_BY_MAJOR: Readonly<Record<number, readonly Declared
         + '`visibility: \'private\'` (on the CLI, `--visibility private`).',
     },
   ],
+  18: [
+    {
+      key: 'ui/FormSection:columns',
+      from: '1',
+      to: '(none)',
+      reason:
+        'A RULED declaration change (maintainer ruling record 6204264665: 「不用决策卡，我同意 b) '
+        + '改协议（推荐）： 去掉分节 columns 的 default(1)」). A form section\'s `columns` now has two '
+        + 'meanings and no default: DECLARED, it is the author\'s ceiling — at most that many fields '
+        + 'per row where the container is wide enough, collapsed by the renderer on narrow '
+        + 'containers; UNDECLARED, the density is the renderer\'s choice by available width. The old '
+        + '`default(1)` materialised an authored-looking `columns: 1` onto every silent section, so '
+        + 'after parse a renderer could not tell "the author asked for one column" from "the author '
+        + 'said nothing" — on a wide dialog the second drew one long column, while the form body\'s '
+        + 'own `FormViewSchema.columns` was already optional with no default. What moves for a '
+        + 'consumer: a parsed section that omits `columns` no longer carries the key, so a reader of '
+        + 'the parsed value sees `1 | 2 | 3 | 4 | undefined`, where `undefined` means "the renderer '
+        + 'decides". To keep a section single-column on a wide container, write `columns: 1`. No '
+        + '`semantic` migration entry accompanies this: materialising `columns: 1` onto stored '
+        + 'sections would re-create exactly the reading the ruling removed, and every declared value '
+        + 'keeps its meaning.',
+    },
+  ],
 };
@@ -200,7 +200,8 @@ describe('controls — byte-identical parse output (measured on origin/main ce70
     });
     expect(branch).toBe('formOverlay');
     expect(JSON.stringify(data)).toBe(
-      '{"type":"simple","sections":[{"label":"Main","collapsible":false,"collapsed":false,"columns":1,"fields":["name"]}],'
+      // No `columns`: a section's undeclared density is the renderer's, and the parse adds no default.
+      '{"type":"simple","sections":[{"label":"Main","collapsible":false,"collapsed":false,"fields":["name"]}],'
       + '"name":"acct.f","object":"account","viewKind":"form"}',
     );
   });
 
@@ -244,7 +244,9 @@ describe('diagnoseViewMetadata names the failing branch', () => {
 // parse output re-measured, and the unbound original moves to REFUSED so the
 // flip itself is pinned rather than silently absorbed.
 describe('the acceptance face of ViewMetadataSchema — frozen by the diagnostics work; every move since is deliberate and pinned', () => {
-  const SECTION = { label: 'Main', collapsible: false, collapsed: false, columns: 1, fields: ['name'] };
+  // A section's `columns` has no default: an undeclared density is the renderer's,
+  // so the parse adds no `columns` key (it added `columns: 1` before the default was dropped).
+  const SECTION = { label: 'Main', collapsible: false, collapsed: false, fields: ['name'] };
   /** [#7741] The binding pair the write path inherits onto a shadowing overlay. */
   const BOUND_LIST = { object: 'crm_lead', viewKind: 'list' } as const;
   const BOUND_FORM = { object: 'crm_lead', viewKind: 'form' } as const;
 
@@ -625,7 +625,17 @@ describe('FormSectionSchema', () => {
     const result = FormSectionSchema.parse(section);
     expect(result.collapsible).toBe(false);
     expect(result.collapsed).toBe(false);
-    expect(result.columns).toBe(1);
+    // An undeclared density is the renderer's (by available width): the parse
+    // adds no `columns`, so "said nothing" stays distinguishable from `1`.
+    expect('columns' in result).toBe(false);
+  });
+
+  it('keeps a declared `columns` as the author\'s ceiling — string spellings parse to the number, out-of-range is refused', () => {
+    expect(FormSectionSchema.parse({ fields: ['name'], columns: 1 }).columns).toBe(1);
+    expect(FormSectionSchema.parse({ fields: ['name'], columns: '2' }).columns).toBe(2);
+    expect(FormSectionSchema.parse({ fields: ['name'], columns: 4 }).columns).toBe(4);
+    expect(FormSectionSchema.safeParse({ fields: ['name'], columns: 5 }).success).toBe(false);
+    expect(FormSectionSchema.safeParse({ fields: ['name'], columns: '0' }).success).toBe(false);
   });
 
   it('should accept form section with all properties', () => {