fix: open the navigation picker among the current page's siblings

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

frontend/src/lib/components/BreadcrumbNavPicker.svelte

@@ -4,8 +4,8 @@ The chevron after the breadcrumb's last segment: it opens the same picker a sess
 uses — the workspace pages, then the folders with their flows, scripts and apps — and picking a
 row navigates the app there.
 
-It lands where the page is: an item's folder with the item highlighted, or a page highlighted at
-the root, so moving to a sibling is one step rather than a drill from the top.
+It lands among the current page's siblings: an item opens in its folder with the item
+highlighted, a workspace page inside Pages with that page highlighted.
 -->
 <script lang="ts">
 	import { ChevronDown } from 'lucide-svelte'
@@ -34,8 +34,7 @@ the root, so moving to a sibling is one step rather than a drill from the top.
 
 	let isOpen = $state(false)
 
-	// The tree files a path under its `f/<folder>` or `u/<user>` scope, then one branch per
-	// subfolder, each keyed by its full path — so the item's own folder is its path minus the name.
+	// The item's own folder is its path minus the name.
 	const initialScope = $derived.by<Scope>(() => {
 		const parts = item?.path?.split('/') ?? []
 		return parts.length >= 3 ? { kind: 'all', dir: parts.slice(0, -1).join('/') } : undefined

frontend/src/lib/components/sessions/PreviewRouterPicker.svelte

@@ -43,6 +43,7 @@ section or the flat layout.
 		PREVIEW_PAGES,
 		artifactKey,
 		isArtifactKey,
+		isPageKey,
 		pageHref,
 		pageKey,
 		previewModeFor,
@@ -243,16 +244,18 @@ section or the flat layout.
 		)
 	])
 
-	// An artifact highlight lives under the 'artifacts' branch, which the legacy
-	// {kind, dir} scope can't express — open the picker inside that branch so the
-	// active artifact is actually visible and highlighted (not the first root row).
-	// Keyed on the highlight's shape alone: the branch itself may not have
-	// materialized yet (artifacts hydrate from IndexedDB after tabs restore), and
-	// the drill entries fill in reactively once it does.
+	// A page or artifact highlight lives under its own branch, which the legacy
+	// {kind, dir} scope can't express — open the picker inside that branch, so the
+	// reader standing on one sees its siblings with it highlighted. Keyed on the
+	// highlight's shape alone: the artifacts branch may not have materialized yet
+	// (artifacts hydrate from IndexedDB after tabs restore), and the drill entries
+	// fill in reactively once it does.
 	const computedInitialScope = untrack(() =>
 		initialHighlight && isArtifactKey(initialHighlight)
 			? ['artifacts']
-			: legacyScopeToPath(initialScope, kinds, 'flat')
+			: initialHighlight && isPageKey(initialHighlight)
+				? ['pages']
+				: legacyScopeToPath(initialScope, kinds, 'flat')
 	)
 
 	// The flat root has no branch to carry a per-kind loading flag — surface

frontend/src/lib/components/sessions/previewPaths.ts

@@ -141,6 +141,7 @@ export function triggerLabelForPath(path: string): string | undefined {
 }
 
 export const pageKey = (path: string) => `page:${path}`
+export const isPageKey = (key: string) => key.startsWith('page:')
 export const pageHref = (path: string) => `${base}${path}`
 
 /** Strip the deployment base prefix (and any query/hash) from a preview path

frontend/src/lib/components/sessions/previewRouter.ts

@@ -1,6 +1,7 @@
 import {
 	ASSETS_PATH,
 	AUDIT_LOGS_PATH,
+	isPageKey,
 	FOLDERS_PATH,
 	GROUPS_PATH,
 	isPageItemListPath,
@@ -29,6 +30,7 @@ import {
 // Re-exported so the preview code that already reads locations through this module keeps
 // one import, while a caller needing only a path can reach for the leaf instead.
 export {
+	isPageKey,
 	pageItemListPath,
 	pageItemUrl,
 	pageKey,

frontend/src/lib/components/workspaceTree.test.ts

@@ -7,7 +7,7 @@ import {
 	type WorkspaceItem,
 	type WorkspaceItemKind
 } from './workspacePicker'
-import type { DrillBranch, DrillLeaf, DrillNode } from './drillPicker'
+import { resolveScope, type DrillBranch, type DrillLeaf, type DrillNode } from './drillPicker'
 
 const item = (
 	kind: WorkspaceItemKind,
@@ -522,6 +522,17 @@ describe('legacyScopeToPath', () => {
 		])
 	})
 
+	it('walks every ancestor folder, so a nested dir resolves in the built tree', () => {
+		const loaded = { flow: [item('flow', 'f/a/b/c')], script: [] }
+		for (const layout of ['flat', 'by-kind'] as const) {
+			const tree = buildWorkspaceTree({ loaded, kinds: ['flow', 'script'], loadingKind: {}, layout })
+			const path = legacyScopeToPath({ kind: 'flow', dir: 'f/a/b' }, ['flow', 'script'], layout)
+			expect(resolveScope(tree, path)?.children.map((c) => c.key)).toEqual([
+				leafKeyFor('flow', 'f/a/b/c')
+			])
+		}
+	})
+
 	it('flat: returns [] without a dir', () => {
 		expect(legacyScopeToPath({ kind: 'all' }, ['flow', 'script'], 'flat')).toEqual([])
 	})

frontend/src/lib/components/workspaceTree.ts

@@ -271,19 +271,20 @@ export function legacyScopeToPath(
 	layout: 'by-kind' | 'flat' = 'by-kind'
 ): string[] {
 	if (!scope) return []
+	// A subfolder is a child of its parent's branch, not a root entry, so a scope into
+	// `f/a/b` must walk `f/a` first or it resolves to nothing.
+	const dirChain = (kind: WorkspaceItemKind | 'all') => {
+		if (!scope.dir) return []
+		const parts = scope.dir.split('/')
+		return parts.slice(1).map((_, i) => dirKey(kind, parts.slice(0, i + 2).join('/')))
+	}
 	// Flat layout: no kind branches at all — scope dirs live at root and are
 	// always keyed under the cross-kind 'all' namespace.
-	if (layout === 'flat') {
-		return scope.dir ? [dirKey('all', scope.dir)] : []
-	}
+	if (layout === 'flat') return dirChain('all')
 	// Single-kind mode: there's no kind branch at root; scope's `kind` is
 	// implicit. Only the dir (if any) makes it to the path.
-	if (kinds.length === 1) {
-		return scope.dir ? [dirKey(scope.kind, scope.dir)] : []
-	}
-	const path: string[] = [kindKey(scope.kind)]
-	if (scope.dir) path.push(dirKey(scope.kind, scope.dir))
-	return path
+	if (kinds.length === 1) return dirChain(scope.kind)
+	return [kindKey(scope.kind), ...dirChain(scope.kind)]
 }
 
 /** Return `absolutePath` shortened to its segment relative to the deepest