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+# Base `page` Property Type — Design Spec
+
+**Date:** 2026-04-20
+**Status:** Draft
+**Feature area:** `apps/server/src/core/base`, `apps/client/src/features/base`, `apps/server/src/core/page`
+
+## Goal
+
+Add a new base property type `page` that lets a user search for and link **one existing page** per cell. Modeled on how the editor's `@` page-mention works — the picker searches existing pages workspace-wide (with current-space prioritized) and the cell renders a live pill with the page's icon and title. No page is auto-created from the picker; users can only link pages that already exist.
+
+Why: today users who want a page-reference column would have to paste a URL into a `url` cell, which loses the icon + title and doesn't validate. We also want to avoid the Focalboard-style pattern of auto-creating a page-row per table row, which would bloat the pages tree.
+
+## Non-goals (v1)
+
+- **Multiple pages per cell.** Single page only. Forward-compatible: the schema widens trivially to `z.union([z.uuid(), z.array(z.uuid())])` + an `allowMultiple` type option later, with zero data migration (see "Future extension" below).
+- **Sorting by page title.** Would require a JOIN against `pages` in the row-list query; skip in v1. Filter suffices.
+- **Creating pages from within the picker.**
+- **Cross-workspace page linking.**
+- **Rich previews / hover cards** showing page excerpts — pill-only.
+- **Confluence-style section grouping** in the property type picker (e.g. the "Page and live doc" section in the screenshot). Flat list for v1; grouping is a separate polish task.
+
+## UX overview
+
+### Picker (edit mode)
+
+- Popover modeled on [cell-person.tsx](../../../apps/client/src/features/base/components/cells/cell-person.tsx) but stripped for single-select. `width=300`, `position="bottom-start"`, `trapFocus`.
+- Top: search input, auto-focused. If a page is currently linked, a removable "tag" for it sits above the search (same shape as `personTag`).
+- Body: results list (max 25), fed by `searchSuggestions({ query, includePages: true, spaceId: base.spaceId, limit: 25 })` — reuses the existing suggestion endpoint, which prioritizes `spaceId` results.
+- Each row: `{icon or IconFileDescription} {title}` + muted space name on the right (so cross-space picks are visually distinct).
+- Empty-query state: if pulling recent-pages is easy to plug in, show recent pages; otherwise "Type to search…" hint.
+- Click or Enter on a highlighted row → `onCommit(pageId)`, popover closes.
+- Esc / click-outside → `onCancel`.
+- Clicking the "Remove" affordance on the current tag → `onCommit(null)`.
+- Keyboard: reuse `useListKeyboardNav`.
+
+### View mode
+
+- Empty cell → empty placeholder (same class as `cellClasses.emptyValue`).
+- Resolved page → pill `{icon or IconFileDescription} {title}`, anchor that navigates to `buildPageUrl(space.slug, slugId, title)` using the helper that [mention-view.tsx](../../../apps/client/src/features/editor/components/mention/mention-view.tsx) already uses.
+- Unresolved (deleted or viewer has no access) → greyed pill "Page not found", no link, `aria-disabled`.
+- Single click on the pill = navigate. Double-click on the cell = open picker (same rule grid-cell applies to other types).
+
+### Sort / filter UI
+
+- [view-sort-config.tsx](../../../apps/client/src/features/base/components/views/view-sort-config.tsx): exclude `page` properties from the sortable set.
+- [view-filter-config.tsx](../../../apps/client/src/features/base/components/views/view-filter-config.tsx): filter editor branch for `page` with operators `isEmpty`, `isNotEmpty`, `any`, `none`. The value picker reuses the same search dropdown from the cell picker.
+
+## Data model
+
+### Cell value
+
+- **Stored shape:** `string` (page UUID) or `null`. Parallels `person` in single mode.
+- **Example:** `{ "01998b7e-...": "01998b80-..." }` — property UUID → page UUID.
+
+### Property type options
+
+- **v1:** empty `{}` (reuse `emptyTypeOptionsSchema`).
+- **Future:** `{ allowMultiple?: boolean }`.
+
+### Schema additions
+
+**Server — [base.schemas.ts](../../../apps/server/src/core/base/base.schemas.ts):**
+
+```ts
+export const BasePropertyType = {
+  // ...existing entries...
+  PAGE: 'page',
+} as const;
+
+// typeOptionsSchemaMap
+[BasePropertyType.PAGE]: emptyTypeOptionsSchema,
+
+// cellValueSchemaMap
+[BasePropertyType.PAGE]: z.uuid(),
+```
+
+**Client — [base.types.ts](../../../apps/client/src/features/base/types/base.types.ts):**
+
+```ts
+export type BasePropertyType = ... | 'page';
+export type PageTypeOptions = Record<string, never>;
+```
+
+### Property kind & engine
+
+**[engine/kinds.ts](../../../apps/server/src/core/base/engine/kinds.ts):**
+
+```ts
+export const PropertyKind = {
+  // ...existing...
+  PAGE: 'page',
+} as const;
+
+// propertyKind()
+case BasePropertyType.PAGE:
+  return PropertyKind.PAGE;
+```
+
+**[engine/predicate.ts](../../../apps/server/src/core/base/engine/predicate.ts):** new `pageCondition()` handler — shape follows `selectCondition()` (single UUID stored as text):
+
+- `isEmpty` / `isNotEmpty` → `textCell` is null or empty
+- `eq` / `neq` → text equality / inequality (null-safe for `neq`)
+- `any` → `textCell IN (...)`
+- `none` → `textCell NOT IN (...)` or null
+
+Wired into the `switch (kind)` in `buildCondition`:
+```ts
+case PropertyKind.PAGE:
+  return pageCondition(eb, cond);
+```
+
+**[engine/sort.ts](../../../apps/server/src/core/base/engine/sort.ts):** no new branch. `page` falls into the default text-sentinel path (sorts by raw UUID string, which is unhelpful but harmless — the sort UI won't expose this type in v1).
+
+### Type conversion
+
+**[base.schemas.ts `CellConversionContext`](../../../apps/server/src/core/base/base.schemas.ts:191):** add a new field:
+
+```ts
+export type CellConversionContext = {
+  fromTypeOptions?: unknown;
+  userNames?: Map<string, string>;
+  attachmentNames?: Map<string, string>;
+  pageTitles?: Map<string, string>; // NEW
+};
+```
+
+**[base-type-conversion.task.ts](../../../apps/server/src/core/base/tasks/base-type-conversion.task.ts):** when `fromType === 'page'`, batch-load titles via the same page repo path used by the new resolver endpoint (see below) and populate `ctx.pageTitles`.
+
+**`attemptCellConversion` branches:**
+- `page → text`: resolve `ctx.pageTitles.get(uuid)` → title (or `""` if missing).
+- `page → *` (anything else): return `{converted: true, value: null}`.
+- `* → page`: return `{converted: true, value: null}` (free text or other IDs can't be coerced to a valid page UUID).
+
+## Server: page resolver endpoint
+
+New endpoint for cell hydration on the client. Reusing `/pages/info` is inappropriate — it returns full page content and is one-at-a-time.
+
+### `POST /bases/pages/resolve`
+
+**Request:**
+```ts
+{ pageIds: string[] }  // 1 <= length <= 100, enforced server-side; 400 on violation
+```
+
+**Response:**
+```ts
+{
+  items: Array<{
+    id: string;
+    slugId: string;
+    title: string | null;
+    icon: string | null;
+    spaceId: string;
+    space: { id: string; slug: string; name: string };
+  }>;
+}
+```
+
+### Behavior
+
+1. Deduplicate input IDs.
+2. Select from `pages` where `id IN (...)` AND `deletedAt IS NULL` AND `workspaceId = current`.
+3. Filter the result set through `pagePermissionRepo.filterAccessiblePageIds({ pageIds, userId })` — same mechanism used by [search.service.ts:131-139](../../../apps/server/src/core/search/search.service.ts).
+4. Join `spaces` to include `space.slug` and `space.name` for navigation.
+5. Silently omit any ID the user can't see (deleted, restricted, cross-workspace). The client treats any requested ID missing from `items` as "Page not found".
+
+### Code layout
+
+- **Controller:** add method to [base.controller.ts](../../../apps/server/src/core/base/controllers/base.controller.ts) at path `@Post('pages/resolve')`. Guarded by the same `JwtAuthGuard` + workspace check the rest of `/bases/*` uses.
+- **Service:** new file `apps/server/src/core/base/services/base-page-resolver.service.ts` with `resolvePagesForBase(pageIds, workspaceId, userId)`. Keeps the coupling to `PageRepo` + `PagePermissionRepo` isolated to this one file.
+- **Module:** wire the new service into [base.module.ts](../../../apps/server/src/core/base/base.module.ts). `PageRepo` + `PagePermissionRepo` are already shared modules.
+
+## Client: cell component & resolver
+
+### Batch resolver hook
+
+New file `apps/client/src/features/base/queries/base-page-resolver-query.ts`:
+
+```ts
+export function useResolvedPages(pageIds: string[]): Map<string, ResolvedPage | null>
+```
+
+- Deduplicate + sort IDs to form a stable React Query key.
+- Fetch `POST /bases/pages/resolve` with `{ pageIds }`.
+- Return a `Map` keyed by every requested ID — `null` for any ID absent from the server response.
+- `staleTime: 30_000`, `gcTime: 5 * 60_000`.
+- Realtime invalidation: listen for existing page-level websocket events (rename, delete) and invalidate the query when a touched ID intersects our key. Exact event names to be surveyed during plan writing.
+
+### Cell component
+
+New file `apps/client/src/features/base/components/cells/cell-page.tsx`:
+
+```ts
+type CellPageProps = {
+  value: unknown;
+  property: IBaseProperty;
+  rowId: string;
+  isEditing: boolean;
+  onCommit: (value: unknown) => void;
+  onCancel: () => void;
+};
+```
+
+**Behavior:**
+- Parse value: accept `string` only (ignore arrays — they'd be from a future multi mode that we drop until upgraded).
+- `useResolvedPages([value])` — yes even for single lookups; the hook dedupes internally so multiple cells sharing the same page ID hit one request.
+- View mode: resolved → pill with icon+title, anchor to `buildPageUrl`. Unresolved → greyed "Page not found".
+- Edit mode: popover picker (see UX overview). Search via existing `searchSuggestions`.
+
+Wire into [grid-cell.tsx](../../../apps/client/src/features/base/components/grid/grid-cell.tsx):
+
+```ts
+const cellComponents = {
+  // ...existing...
+  page: CellPage,
+};
+```
+
+### Property type picker
+
+[property-type-picker.tsx](../../../apps/client/src/features/base/components/property/property-type-picker.tsx): append one entry (after `file`):
+
+```ts
+{ type: "page", icon: IconFileDescription, labelKey: "Page" },
+```
+
+### Filter editor
+
+[view-filter-config.tsx](../../../apps/client/src/features/base/components/views/view-filter-config.tsx): new branch for `page`:
+- Operators: `isEmpty`, `isNotEmpty`, `any`, `none`.
+- Value picker for `any`/`none`: reuses the same `searchSuggestions`-backed search dropdown from the cell picker — user picks one or more pages as filter operands.
+
+### Sort editor
+
+[view-sort-config.tsx](../../../apps/client/src/features/base/components/views/view-sort-config.tsx): exclude `page` from the list of sortable property types.
+
+## Testing
+
+### Server — unit
+
+- **Schema:** `validateCellValue('page', uuid)` passes; with garbage string / number → fails; with `null` → passes (null = empty).
+- **Conversion:**
+  - `attemptCellConversion('page', 'text', uuid, { pageTitles: Map<uuid,title> })` → resolved title.
+  - Same call with empty `pageTitles` → `""`.
+  - `page → number/date/select/…` → `{converted: true, value: null}`.
+  - `text → page` with any string input → `{converted: true, value: null}`.
+- **Predicate:** for each operator (`isEmpty`, `isNotEmpty`, `eq`, `neq`, `any`, `none`), `pageCondition()` returns the expected Kysely expression shape.
+
+### Server — integration
+
+- **Resolver endpoint `POST /bases/pages/resolve`:**
+  - valid IDs in an accessible space → present in `items`
+  - deleted pages (trash) → absent
+  - pages in a space the user isn't a member of → absent
+  - pages in another workspace → absent
+  - empty array → 400
+  - array length > 100 → 400
+- **Row CRUD:** create a property of type `page`, write a cell with a UUID, read back → round-trip shape is `string`.
+- **View filter:** create a view config with `{ op: 'any', propertyId, value: [uuidA, uuidB] }`, hit row-list, verify only matching rows returned.
+
+### Client — unit (Vitest + React Testing Library)
+
+- `cell-page.test.tsx`:
+  - view mode with resolved page → renders pill with icon + title and an `<a>` to the computed URL
+  - view mode with unresolved page (null in resolver map) → renders greyed "Page not found", no `<a>`
+  - double-click opens picker
+  - Enter on highlighted result commits `pageId`
+  - Esc cancels
+  - Remove tag button commits `null`
+- `base-page-resolver-query.test.ts`:
+  - dedupes IDs
+  - stable query key across re-renders with same set
+  - missing IDs render as `null` in the returned map
+
+### Manual QA checklist
+
+- Link a page in the same space.
+- Link a page in another space → pill shows, picker shows muted space-name hint.
+- Remove link → cell empties.
+- Delete linked page (via trash) → cell flips to "Page not found" on next resolver refetch.
+- Viewer loses space access → same "Page not found" fallback.
+- Rename linked page → within ≤30s (staleTime) the pill reflects the new title; realtime event should also trigger refetch.
+- Filter: `isEmpty`, `isNotEmpty`, `any` (multi-select), `none`.
+- Conversion `page → text` populates cells with page titles.
+- Conversion `text → page` wipes cells.
+
+## Rollout
+
+- **No DB migration.** All changes are code-only: new enum value, new cell-value validator entry, new engine kind branch, new endpoint.
+- **No feature flag.** The type appears in the picker as soon as the build ships. Backwards-compatible since `'page'` is a new type identifier.
+- Existing bases continue to work unchanged.
+
+## Risks & open questions
+
+- **30s staleTime.** Renames take up to 30s to propagate without realtime invalidation. The realtime hook should shrink this to near-zero in practice; verify in QA. If it feels slow, drop `staleTime` to `0` and rely solely on realtime + refetch-on-window-focus.
+- **"Page not found" label.** i18n-friendly; run through the translation pipeline. Consider whether to differentiate deleted vs. restricted — current answer: no, one label covers both and matches Confluence's behavior.
+- **Cross-space name exposure.** The picker surfaces the space name of pages the user can access cross-space. This is already exposed via the existing page-mention flow, so no new exposure, but flag in review.
+
+## Future extension (multiple pages per cell)
+
+When `allowMultiple` lands:
+
+1. Widen cell-value schema: `z.uuid()` → `z.union([z.uuid(), z.array(z.uuid())])`. Existing single-UUID cells continue to validate.
+2. Add `allowMultiple` boolean to `pageTypeOptionsSchema` (default `false` for existing properties).
+3. In [predicate.ts](../../../apps/server/src/core/base/engine/predicate.ts), branch `pageCondition` on `allowMultiple`: `true` → reuse `arrayOfIdsCondition`; `false` → keep the current text-based path.
+4. Client cell normalizes on read (`Array.isArray(value) ? value : typeof value === 'string' ? [value] : []`), mirrors [cell-person.tsx:33](../../../apps/client/src/features/base/components/cells/cell-person.tsx).
+5. No data writes required for existing cells.
+
+This spec leaves room for that change without locking the storage shape.