Merge pull request 'Offline-first support: read cache, write queue, settings redesign' (#6) from feature/offline-cache into main

Reviewed-on: #6
2026-08-15 15:47:48 +01:00
parent b28dc019aa badb206f8a
commit 41abcd5d1c
30 changed files with 2211 additions and 78 deletions
@@ -0,0 +1,18 @@
+import Foundation
+import SwiftData
+
+/// Generic key/value row backing `OfflineCacheStore` — one table for every
+/// cached response shape instead of a `@Model` per Outline type, so adding a
+/// new cached endpoint never needs a schema migration.
+@Model
+public final class CachedPayload {
+    @Attribute(.unique) public var key: String
+    public var payload: Data
+    public var cachedAt: Date
+
+    public init(key: String, payload: Data, cachedAt: Date) {
+        self.key = key
+        self.payload = payload
+        self.cachedAt = cachedAt
+    }
+}
@@ -0,0 +1,665 @@
+import Foundation
+
+/// Decorates `LiveOutlineAPIClient` (or any `OutlineAPIClient`) with offline
+/// support at the existing protocol boundary, so no view model needs to know
+/// the network exists:
+///
+/// - **Reads** (`documentInfo`, `listDocuments`, `documentsList`,
+///   `listViewedDocuments`, `listCollections`, `collectionInfo`): read-through
+///   cache. Always tries live first — never pre-checks reachability, since
+///   "did this specific request just fail" is a more honest signal than a
+///   reachability monitor, and the two can disagree (captive portals,
+///   flaky Wi-Fi). Falls back to the cache only on failure; a live success
+///   always overwrites the cache, so staleness is bounded by "last time this
+///   endpoint actually worked."
+/// - **A small set of writes** (`updateDocument`, `updateCollection`,
+///   pin/star/subscribe create+delete): applied optimistically against the
+///   cache and queued in `OfflineCacheStore`'s `PendingOperation` table on
+///   failure, then replayed in order by `flushPendingOperations()` once back
+///   online. Deliberately doesn't include anything that creates new tree
+///   structure (`createDocument`, `moveDocument`, `archiveDocument`,
+///   `deleteDocument`, `deleteCollection`, `duplicateDocument`) — those need
+///   real server-assigned ids to stay consistent with the rest of the tree,
+///   and reconciling a locally-invented id with the one the server hands
+///   back on sync is a much bigger problem than this pass takes on. Sharing,
+///   permissions, search, and export also stay live-only — read the request,
+///   they need someone else's server session, not just a network.
+/// - **Manual offline mode** (`offlineModeDefaultsKey`): when set, skips
+///   attempting `live` entirely — same fallback/queue paths as a real
+///   failure, just chosen on purpose instead of discovered.
+public actor CachingOutlineAPIClient: OutlineAPIClient {
+    public static let offlineModeDefaultsKey = "outpost.offlineModeEnabled"
+
+    private let live: OutlineAPIClient
+    private let cache: OfflineCacheStore
+    private let defaults: UserDefaults
+    private let encoder: JSONEncoder
+    private let decoder: JSONDecoder
+    private let keyEncoder: JSONEncoder
+
+    public init(live: OutlineAPIClient, cache: OfflineCacheStore, defaults: UserDefaults = .standard) {
+        self.live = live
+        self.cache = cache
+        self.defaults = defaults
+
+        let encoder = JSONEncoder()
+        encoder.dateEncodingStrategy = .iso8601
+        self.encoder = encoder
+
+        let decoder = JSONDecoder()
+        decoder.dateDecodingStrategy = .iso8601
+        self.decoder = decoder
+
+        let keyEncoder = JSONEncoder()
+        keyEncoder.outputFormatting = .sortedKeys
+        self.keyEncoder = keyEncoder
+    }
+
+    private var isManualOfflineModeEnabled: Bool {
+        defaults.bool(forKey: Self.offlineModeDefaultsKey)
+    }
+
+    // MARK: - Cached reads
+
+    public func documentInfo(id: String) async throws -> OutlineDocument {
+        try await cachedFetch(key: "document:\(id)") { try await self.live.documentInfo(id: id) }
+    }
+
+    public func listDocuments(
+        collectionId: String?,
+        parentDocumentId: String?,
+        offset: Int,
+        limit: Int
+    ) async throws -> [OutlineDocument] {
+        let key = "documents:\(collectionId ?? "-"):\(parentDocumentId ?? "-"):\(offset):\(limit)"
+        return try await cachedFetch(key: key) {
+            try await self.live.listDocuments(
+                collectionId: collectionId,
+                parentDocumentId: parentDocumentId,
+                offset: offset,
+                limit: limit
+            )
+        }
+    }
+
+    public func documentsList(_ request: DocumentsListRequest) async throws -> [OutlineDocument] {
+        try await cachedFetch(key: requestKey("documentsList", request)) { try await self.live.documentsList(request) }
+    }
+
+    public func listViewedDocuments(offset: Int, limit: Int) async throws -> [OutlineDocument] {
+        try await cachedFetch(key: "documentsViewed:\(offset):\(limit)") {
+            try await self.live.listViewedDocuments(offset: offset, limit: limit)
+        }
+    }
+
+    public func listCollections(offset: Int, limit: Int) async throws -> [OutlineCollection] {
+        try await cachedFetch(key: "collections:\(offset):\(limit)") {
+            try await self.live.listCollections(offset: offset, limit: limit)
+        }
+    }
+
+    public func collectionInfo(id: String) async throws -> OutlineCollection {
+        try await cachedFetch(key: "collection:\(id)") { try await self.live.collectionInfo(id: id) }
+    }
+
+    // MARK: - Queueable writes
+
+    /// The one exception to "no new tree structure while offline" —
+    /// synthesizes a document under a `pending-<uuid>` id (same scheme as
+    /// pin/star/subscribe), caches it so it's immediately readable/editable,
+    /// and queues the real create. On sync, the server-assigned id replaces
+    /// the placeholder in the cache; anything still referencing the old id
+    /// directly (a currently-open reader, most likely) won't follow that
+    /// rename automatically — a known, narrow limitation, not something this
+    /// pass tries to solve generally.
+    public func createDocument(_ request: CreateDocumentRequest) async throws -> OutlineDocument {
+        if !isManualOfflineModeEnabled {
+            do {
+                let result = try await live.createDocument(request)
+                await cacheDocument(result)
+                return result
+            } catch {
+                return await queueDocumentCreate(request)
+            }
+        }
+        return await queueDocumentCreate(request)
+    }
+
+    public func updateDocument(_ request: UpdateDocumentRequest) async throws -> OutlineDocument {
+        if !isManualOfflineModeEnabled {
+            do {
+                let result = try await live.updateDocument(request)
+                await cacheDocument(result)
+                return result
+            } catch {
+                return try await queueDocumentUpdate(request, dueTo: error)
+            }
+        }
+        return try await queueDocumentUpdate(request, dueTo: nil)
+    }
+
+    public func updateCollection(_ request: UpdateCollectionRequest) async throws -> OutlineCollection {
+        if !isManualOfflineModeEnabled {
+            do {
+                let result = try await live.updateCollection(request)
+                await cacheCollection(result)
+                return result
+            } catch {
+                return try await queueCollectionUpdate(request, dueTo: error)
+            }
+        }
+        return try await queueCollectionUpdate(request, dueTo: nil)
+    }
+
+    public func createPin(_ request: CreatePinRequest) async throws -> OutlinePin {
+        if !isManualOfflineModeEnabled {
+            do { return try await live.createPin(request) } catch { return await queuePinCreate(request) }
+        }
+        return await queuePinCreate(request)
+    }
+
+    public func deletePin(id: String) async throws {
+        if await cancelIfNeverSynced(id: id) { return }
+        if !isManualOfflineModeEnabled {
+            do {
+                try await live.deletePin(id: id)
+                return
+            } catch {
+                await enqueue(.deletePin, payload: IDPayload(id: id), id: "delete-pin-\(id)")
+                return
+            }
+        }
+        await enqueue(.deletePin, payload: IDPayload(id: id), id: "delete-pin-\(id)")
+    }
+
+    public func createSubscription(_ request: CreateSubscriptionRequest) async throws -> OutlineSubscription {
+        if !isManualOfflineModeEnabled {
+            do { return try await live.createSubscription(request) } catch { return await queueSubscriptionCreate(request) }
+        }
+        return await queueSubscriptionCreate(request)
+    }
+
+    public func deleteSubscription(id: String) async throws {
+        if await cancelIfNeverSynced(id: id) { return }
+        if !isManualOfflineModeEnabled {
+            do {
+                try await live.deleteSubscription(id: id)
+                return
+            } catch {
+                await enqueue(.deleteSubscription, payload: IDPayload(id: id), id: "delete-subscription-\(id)")
+                return
+            }
+        }
+        await enqueue(.deleteSubscription, payload: IDPayload(id: id), id: "delete-subscription-\(id)")
+    }
+
+    public func starDocument(_ request: StarDocumentRequest) async throws -> OutlineStar {
+        if !isManualOfflineModeEnabled {
+            do { return try await live.starDocument(request) } catch { return await queueStarDocumentCreate(request) }
+        }
+        return await queueStarDocumentCreate(request)
+    }
+
+    public func starCollection(_ request: StarCollectionRequest) async throws -> OutlineStar {
+        if !isManualOfflineModeEnabled {
+            do { return try await live.starCollection(request) } catch { return await queueStarCollectionCreate(request) }
+        }
+        return await queueStarCollectionCreate(request)
+    }
+
+    public func deleteStar(id: String) async throws {
+        if await cancelIfNeverSynced(id: id) { return }
+        if !isManualOfflineModeEnabled {
+            do {
+                try await live.deleteStar(id: id)
+                return
+            } catch {
+                await enqueue(.deleteStar, payload: IDPayload(id: id), id: "delete-star-\(id)")
+                return
+            }
+        }
+        await enqueue(.deleteStar, payload: IDPayload(id: id), id: "delete-star-\(id)")
+    }
+
+    // MARK: - Pass-through
+
+    public func authInfo() async throws -> OutlineAuthInfo {
+        try await live.authInfo()
+    }
+
+    public func searchDocuments(_ request: DocumentSearchRequest) async throws -> [OutlineDocumentSearchResult] {
+        try await live.searchDocuments(request)
+    }
+
+    public func searchDocumentTitles(_ request: DocumentSearchTitlesRequest) async throws -> [OutlineDocument] {
+        try await live.searchDocumentTitles(request)
+    }
+
+    public func templatizeDocument(_ request: TemplatizeDocumentRequest) async throws -> OutlineTemplate {
+        try await live.templatizeDocument(request)
+    }
+
+    public func duplicateDocument(_ request: DuplicateDocumentRequest) async throws -> [OutlineDocument] {
+        try await live.duplicateDocument(request)
+    }
+
+    public func unpublishDocument(_ request: UnpublishDocumentRequest) async throws -> OutlineDocument {
+        try await live.unpublishDocument(request)
+    }
+
+    public func archiveDocument(id: String) async throws -> OutlineDocument {
+        try await live.archiveDocument(id: id)
+    }
+
+    public func moveDocument(_ request: MoveDocumentRequest) async throws {
+        try await live.moveDocument(request)
+    }
+
+    public func deleteDocument(_ request: DeleteDocumentRequest) async throws {
+        try await live.deleteDocument(request)
+    }
+
+    public func documentInsights(_ request: DocumentInsightsRequest) async throws -> [OutlineDocumentInsight] {
+        try await live.documentInsights(request)
+    }
+
+    public func listRevisions(_ request: ListRevisionsRequest) async throws -> [OutlineRevision] {
+        try await live.listRevisions(request)
+    }
+
+    public func exportDocument(id: String) async throws -> String {
+        try await live.exportDocument(id: id)
+    }
+
+    public func createShare(_ request: CreateShareRequest) async throws -> OutlineShare {
+        try await live.createShare(request)
+    }
+
+    public func shareInfo(documentId: String) async throws -> OutlineShare? {
+        try await live.shareInfo(documentId: documentId)
+    }
+
+    public func updateShare(_ request: UpdateShareRequest) async throws -> OutlineShare {
+        try await live.updateShare(request)
+    }
+
+    public func listShares(_ request: ListSharesRequest) async throws -> [OutlineShare] {
+        try await live.listShares(request)
+    }
+
+    public func revokeShare(id: String) async throws {
+        try await live.revokeShare(id: id)
+    }
+
+    public func listPins(_ request: ListPinsRequest) async throws -> [OutlinePin] {
+        try await live.listPins(request)
+    }
+
+    public func listSubscriptions(_ request: ListSubscriptionsRequest) async throws -> [OutlineSubscription] {
+        try await live.listSubscriptions(request)
+    }
+
+    public func listViews(_ request: ListViewsRequest) async throws -> [OutlineView] {
+        try await live.listViews(request)
+    }
+
+    public func addDocumentUser(_ request: AddDocumentUserRequest) async throws -> OutlineMembership {
+        try await live.addDocumentUser(request)
+    }
+
+    public func removeDocumentUser(_ request: RemoveDocumentUserRequest) async throws {
+        try await live.removeDocumentUser(request)
+    }
+
+    public func documentUsers(_ request: ListDocumentUsersRequest) async throws -> [OutlineDocumentMember] {
+        try await live.documentUsers(request)
+    }
+
+    public func listUsers(_ request: ListUsersRequest) async throws -> [OutlineUser] {
+        try await live.listUsers(request)
+    }
+
+    public func deleteCollection(id: String) async throws {
+        try await live.deleteCollection(id: id)
+    }
+
+    public func exportCollection(_ request: ExportCollectionRequest) async throws -> OutlineFileOperation {
+        try await live.exportCollection(request)
+    }
+
+    public func listStars(_ request: ListStarsRequest) async throws -> [OutlineStar] {
+        try await live.listStars(request)
+    }
+
+    public func currentUser() async throws -> OutlineUser {
+        try await live.currentUser()
+    }
+
+    // MARK: - Sync management (Settings surface)
+
+    public func pendingOperations() async -> [PendingOperationSummary] {
+        await cache.pendingOperations().map {
+            PendingOperationSummary(id: $0.id, kind: $0.kind, createdAt: $0.createdAt, attemptCount: $0.attemptCount, lastError: $0.lastError)
+        }
+    }
+
+    public func cacheStorageSummary() async -> CacheStorageSummary {
+        CacheStorageSummary(itemCount: await cache.itemCount(), totalBytes: await cache.totalBytes())
+    }
+
+    public func clearCache() async {
+        await cache.clearAll()
+    }
+
+    /// Replays every queued operation against `live`, in the order they were
+    /// queued. Each is independent — one failing doesn't block the rest.
+    public func flushPendingOperations() async -> SyncFlushSummary {
+        let operations = await cache.pendingOperations()
+        var succeeded = 0
+        var failed = 0
+        for operation in operations {
+            do {
+                try await replay(operation)
+                await cache.removeOperation(id: operation.id)
+                succeeded += 1
+            } catch {
+                await cache.recordFailure(id: operation.id, error: errorDescription(error))
+                failed += 1
+            }
+        }
+        return SyncFlushSummary(succeeded: succeeded, failed: failed)
+    }
+
+    /// "Full Local Sync": eagerly walks every collection and caches every
+    /// document's full content (not just whatever's been opened), so
+    /// browsing offline works for the whole workspace, not only what was
+    /// already viewed. Goes through `self`, not `live`, directly — the
+    /// existing cached-read methods already do the caching as a side effect,
+    /// this just has to drive the walk and separately cache each document by
+    /// id (`listDocuments`'s cache key is the list, not the individual doc).
+    public func performFullSync() async -> FullSyncSummary {
+        var documentsCount = 0
+        var errors: [String] = []
+        var collections: [OutlineCollection] = []
+        var collectionsOffset = 0
+        let collectionsLimit = 100
+        // Outline rejects any `limit` over 100 outright — page in increments
+        // of that instead of guessing a total up front (the protocol doesn't
+        // expose `pagination`'s total count, only the page itself); a page
+        // shorter than the limit is what signals "that was the last one".
+        while true {
+            let page: [OutlineCollection]
+            do {
+                page = try await listCollections(offset: collectionsOffset, limit: collectionsLimit)
+            } catch {
+                errors.append(errorDescription(error))
+                break
+            }
+            collections.append(contentsOf: page)
+            guard page.count == collectionsLimit else { break }
+            collectionsOffset += collectionsLimit
+        }
+
+        for collection in collections {
+            var offset = 0
+            let limit = 100
+            while true {
+                let documents: [OutlineDocument]
+                do {
+                    documents = try await listDocuments(collectionId: collection.id, parentDocumentId: nil, offset: offset, limit: limit)
+                } catch {
+                    errors.append("\(collection.name): \(errorDescription(error))")
+                    break
+                }
+                for document in documents {
+                    await cacheDocument(document)
+                }
+                documentsCount += documents.count
+                guard documents.count == limit else { break }
+                offset += limit
+            }
+        }
+
+        return FullSyncSummary(collectionsCount: collections.count, documentsCount: documentsCount, errors: errors, finishedAt: Date())
+    }
+
+    // MARK: - Helpers
+
+    private func cachedFetch<T: Codable>(key: String, fetch: () async throws -> T) async throws -> T {
+        // Manual offline mode means "skip the network entirely," not just
+        // "prefer it" — without this check, a read would still hit `live`
+        // (and succeed, showing content beyond whatever's cached) any time
+        // the device actually had a connection, defeating the point of
+        // deliberately testing/working as if offline.
+        if isManualOfflineModeEnabled {
+            if let data = await cache.load(forKey: key), let cached = try? decoder.decode(T.self, from: data) {
+                return cached
+            }
+            throw OutlineAPIError.transport(URLError(.notConnectedToInternet))
+        }
+        do {
+            let result = try await fetch()
+            if let data = try? encoder.encode(result) {
+                await cache.save(data, forKey: key)
+            }
+            return result
+        } catch {
+            if let data = await cache.load(forKey: key), let cached = try? decoder.decode(T.self, from: data) {
+                return cached
+            }
+            throw error
+        }
+    }
+
+    private func requestKey(_ prefix: String, _ request: some Encodable) -> String {
+        guard let data = try? keyEncoder.encode(request), let json = String(data: data, encoding: .utf8) else {
+            return prefix
+        }
+        return "\(prefix):\(json)"
+    }
+
+    private func cacheDocument(_ document: OutlineDocument) async {
+        if let data = try? encoder.encode(document) {
+            await cache.save(data, forKey: "document:\(document.id)")
+        }
+    }
+
+    private func cacheCollection(_ collection: OutlineCollection) async {
+        if let data = try? encoder.encode(collection) {
+            await cache.save(data, forKey: "collection:\(collection.id)")
+        }
+    }
+
+    private func enqueue(_ kind: PendingOperationKind, payload: some Encodable, id: String) async {
+        guard let data = try? encoder.encode(payload) else { return }
+        await cache.enqueueOperation(id: id, kind: kind.rawValue, payload: data)
+    }
+
+    /// A delete targeting a `pending-*` id can only mean "cancel the create
+    /// still sitting in the queue" — the server has never heard of that id,
+    /// so queuing the delete would just fail once synced. Returns whether it
+    /// found (and removed) a matching create, meaning the caller is done.
+    private func cancelIfNeverSynced(id: String) async -> Bool {
+        guard id.hasPrefix("pending-") else { return false }
+        return await cache.removeOperation(id: id)
+    }
+
+    private func queueDocumentCreate(_ request: CreateDocumentRequest) async -> OutlineDocument {
+        let pendingId = "pending-\(UUID().uuidString)"
+        let now = Date()
+        let synthesized = OutlineDocument(
+            id: pendingId,
+            title: request.title,
+            text: request.text,
+            emoji: nil,
+            collectionId: request.collectionId,
+            parentDocumentId: request.parentDocumentId,
+            url: "/doc/\(pendingId)",
+            revision: nil,
+            fullWidth: nil,
+            createdAt: now,
+            updatedAt: now,
+            publishedAt: request.publish ? now : nil,
+            archivedAt: nil,
+            deletedAt: nil
+        )
+        await cacheDocument(synthesized)
+        await enqueue(.createDocument, payload: request, id: pendingId)
+        return synthesized
+    }
+
+    private func queueDocumentUpdate(_ request: UpdateDocumentRequest, dueTo error: Error?) async throws -> OutlineDocument {
+        guard let baseData = await cache.load(forKey: "document:\(request.id)"),
+              let base = try? decoder.decode(OutlineDocument.self, from: baseData) else {
+            throw error ?? OutlineAPIError.transport(URLError(.notConnectedToInternet))
+        }
+        let mergedText = request.append == true ? base.text + (request.text ?? "") : (request.text ?? base.text)
+        let merged = OutlineDocument(
+            id: base.id,
+            title: request.title ?? base.title,
+            text: mergedText,
+            emoji: base.emoji,
+            collectionId: base.collectionId,
+            parentDocumentId: base.parentDocumentId,
+            url: base.url,
+            revision: base.revision,
+            fullWidth: request.fullWidth ?? base.fullWidth,
+            createdAt: base.createdAt,
+            updatedAt: Date(),
+            publishedAt: base.publishedAt,
+            archivedAt: base.archivedAt,
+            deletedAt: base.deletedAt
+        )
+        await cacheDocument(merged)
+
+        // Still-unsynced create for this exact document — fold the edit into
+        // the pending create's payload instead of queuing a separate update.
+        // A separate update would target `merged.id`, which is still the
+        // `pending-*` placeholder at replay time; the server has never heard
+        // of it and the update would just fail every retry.
+        if merged.id.hasPrefix("pending-"),
+           let createOp = await cache.pendingOperations().first(where: { $0.id == merged.id && $0.kind == PendingOperationKind.createDocument.rawValue }),
+           let createRequest = try? decoder.decode(CreateDocumentRequest.self, from: createOp.payload) {
+            let resolvedCreate = CreateDocumentRequest(
+                title: merged.title,
+                text: merged.text,
+                collectionId: createRequest.collectionId,
+                parentDocumentId: createRequest.parentDocumentId,
+                publish: createRequest.publish
+            )
+            await enqueue(.createDocument, payload: resolvedCreate, id: merged.id)
+            return merged
+        }
+
+        // Fully resolved (not the original partial request) so replaying just
+        // this one queued operation reproduces `merged` exactly — that's what
+        // makes coalescing a second edit onto the same queued id safe.
+        let resolved = UpdateDocumentRequest(id: merged.id, title: merged.title, text: merged.text, fullWidth: merged.fullWidth)
+        await enqueue(.updateDocument, payload: resolved, id: "update-document-\(merged.id)")
+        return merged
+    }
+
+    private func queueCollectionUpdate(_ request: UpdateCollectionRequest, dueTo error: Error?) async throws -> OutlineCollection {
+        guard let baseData = await cache.load(forKey: "collection:\(request.id)"),
+              let base = try? decoder.decode(OutlineCollection.self, from: baseData) else {
+            throw error ?? OutlineAPIError.transport(URLError(.notConnectedToInternet))
+        }
+        let merged = OutlineCollection(
+            id: base.id,
+            name: request.name ?? base.name,
+            description: request.description ?? base.description,
+            color: base.color,
+            icon: base.icon,
+            createdAt: base.createdAt,
+            updatedAt: Date()
+        )
+        await cacheCollection(merged)
+        let resolved = UpdateCollectionRequest(id: merged.id, name: merged.name, description: merged.description)
+        await enqueue(.updateCollection, payload: resolved, id: "update-collection-\(merged.id)")
+        return merged
+    }
+
+    private func queuePinCreate(_ request: CreatePinRequest) async -> OutlinePin {
+        let pendingId = "pending-\(UUID().uuidString)"
+        await enqueue(.createPin, payload: request, id: pendingId)
+        return OutlinePin(id: pendingId, documentId: request.documentId, collectionId: request.collectionId, index: nil)
+    }
+
+    private func queueSubscriptionCreate(_ request: CreateSubscriptionRequest) async -> OutlineSubscription {
+        let pendingId = "pending-\(UUID().uuidString)"
+        await enqueue(.createSubscription, payload: request, id: pendingId)
+        return OutlineSubscription(id: pendingId, documentId: request.documentId, collectionId: nil, event: request.event)
+    }
+
+    private func queueStarDocumentCreate(_ request: StarDocumentRequest) async -> OutlineStar {
+        let pendingId = "pending-\(UUID().uuidString)"
+        await enqueue(.starDocument, payload: request, id: pendingId)
+        return OutlineStar(id: pendingId, index: nil, documentId: request.documentId, collectionId: nil)
+    }
+
+    private func queueStarCollectionCreate(_ request: StarCollectionRequest) async -> OutlineStar {
+        let pendingId = "pending-\(UUID().uuidString)"
+        await enqueue(.starCollection, payload: request, id: pendingId)
+        return OutlineStar(id: pendingId, index: nil, documentId: nil, collectionId: request.collectionId)
+    }
+
+    private func replay(_ operation: PendingOperation) async throws {
+        guard let kind = PendingOperationKind(rawValue: operation.kind) else {
+            throw OutlineAPIError.decoding(DecodingError.dataCorrupted(
+                DecodingError.Context(codingPath: [], debugDescription: "Unknown pending operation kind: \(operation.kind)")
+            ))
+        }
+        switch kind {
+        case .createDocument:
+            let request = try decoder.decode(CreateDocumentRequest.self, from: operation.payload)
+            let result = try await live.createDocument(request)
+            await cacheDocument(result)
+            // The placeholder id (== operation.id) is now a dead orphan —
+            // nothing server-side will ever answer to it again.
+            await cache.removeCacheEntry(forKey: "document:\(operation.id)")
+        case .updateDocument:
+            let request = try decoder.decode(UpdateDocumentRequest.self, from: operation.payload)
+            let result = try await live.updateDocument(request)
+            await cacheDocument(result)
+        case .updateCollection:
+            let request = try decoder.decode(UpdateCollectionRequest.self, from: operation.payload)
+            let result = try await live.updateCollection(request)
+            await cacheCollection(result)
+        case .createPin:
+            let request = try decoder.decode(CreatePinRequest.self, from: operation.payload)
+            _ = try await live.createPin(request)
+        case .deletePin:
+            let request = try decoder.decode(IDPayload.self, from: operation.payload)
+            try await live.deletePin(id: request.id)
+        case .createSubscription:
+            let request = try decoder.decode(CreateSubscriptionRequest.self, from: operation.payload)
+            _ = try await live.createSubscription(request)
+        case .deleteSubscription:
+            let request = try decoder.decode(IDPayload.self, from: operation.payload)
+            try await live.deleteSubscription(id: request.id)
+        case .starDocument:
+            let request = try decoder.decode(StarDocumentRequest.self, from: operation.payload)
+            _ = try await live.starDocument(request)
+        case .deleteStar:
+            let request = try decoder.decode(IDPayload.self, from: operation.payload)
+            try await live.deleteStar(id: request.id)
+        case .starCollection:
+            let request = try decoder.decode(StarCollectionRequest.self, from: operation.payload)
+            _ = try await live.starCollection(request)
+        }
+    }
+
+    private func errorDescription(_ error: Error) -> String {
+        if let apiError = error as? OutlineAPIError {
+            switch apiError {
+            case .unauthorized: return "Sign-in expired."
+            case .notFound: return "Not found on the server."
+            case .server(let status, let message): return message ?? "Server error (\(status))."
+            case .decoding: return "Unexpected response shape."
+            case .transport: return "Couldn't reach the server."
+            case .tokenUnavailable: return "Couldn't access the saved sign-in."
+            }
+        }
+        return String(describing: error)
+    }
+}
@@ -0,0 +1,104 @@
+import Foundation
+import SwiftData
+
+/// Read-through cache backing `CachingOutlineAPIClient` — stores whatever it
+/// last fetched successfully, keyed by request shape, so browsing keeps
+/// working (stale) once the network stops. Also owns the offline write
+/// queue (`PendingOperation`) — same store, same actor, since both need
+/// synchronized access to the same on-disk SwiftData container.
+@ModelActor
+public actor OfflineCacheStore {
+    public static func makeContainer(inMemory: Bool = false) throws -> ModelContainer {
+        let configuration = ModelConfiguration(isStoredInMemoryOnly: inMemory)
+        return try ModelContainer(for: CachedPayload.self, PendingOperation.self, configurations: configuration)
+    }
+
+    // MARK: - Read-through cache
+
+    public func save(_ data: Data, forKey key: String) {
+        let descriptor = FetchDescriptor<CachedPayload>(predicate: #Predicate { $0.key == key })
+        if let existing = try? modelContext.fetch(descriptor).first {
+            existing.payload = data
+            existing.cachedAt = Date()
+        } else {
+            modelContext.insert(CachedPayload(key: key, payload: data, cachedAt: Date()))
+        }
+        try? modelContext.save()
+    }
+
+    public func load(forKey key: String) -> Data? {
+        let descriptor = FetchDescriptor<CachedPayload>(predicate: #Predicate { $0.key == key })
+        return try? modelContext.fetch(descriptor).first?.payload
+    }
+
+    /// Used to drop a temporary `pending-*` document's cache entry once a
+    /// queued create syncs and the server hands back the real id — the
+    /// placeholder key would otherwise sit around as a dead orphan forever.
+    public func removeCacheEntry(forKey key: String) {
+        let descriptor = FetchDescriptor<CachedPayload>(predicate: #Predicate { $0.key == key })
+        guard let existing = try? modelContext.fetch(descriptor).first else { return }
+        modelContext.delete(existing)
+        try? modelContext.save()
+    }
+
+    public func itemCount() -> Int {
+        (try? modelContext.fetchCount(FetchDescriptor<CachedPayload>())) ?? 0
+    }
+
+    public func totalBytes() -> Int {
+        let descriptor = FetchDescriptor<CachedPayload>()
+        let rows = (try? modelContext.fetch(descriptor)) ?? []
+        return rows.reduce(0) { $0 + $1.payload.count }
+    }
+
+    public func clearAll() {
+        let descriptor = FetchDescriptor<CachedPayload>()
+        guard let rows = try? modelContext.fetch(descriptor) else { return }
+        rows.forEach { modelContext.delete($0) }
+        try? modelContext.save()
+    }
+
+    // MARK: - Offline write queue
+
+    /// Upserts by `id` — a second call with the same id (an edit coalescing
+    /// onto a still-unsynced edit, or a create being cancelled by its own
+    /// synthesized id) replaces the row in place rather than piling up.
+    public func enqueueOperation(id: String, kind: String, payload: Data) {
+        let descriptor = FetchDescriptor<PendingOperation>(predicate: #Predicate { $0.id == id })
+        if let existing = try? modelContext.fetch(descriptor).first {
+            existing.kind = kind
+            existing.payload = payload
+            existing.lastError = nil
+            existing.attemptCount = 0
+        } else {
+            modelContext.insert(PendingOperation(id: id, kind: kind, payload: payload, createdAt: Date()))
+        }
+        try? modelContext.save()
+    }
+
+    public func pendingOperations() -> [PendingOperation] {
+        let descriptor = FetchDescriptor<PendingOperation>(sortBy: [SortDescriptor(\.createdAt)])
+        return (try? modelContext.fetch(descriptor)) ?? []
+    }
+
+    /// Returns whether a matching operation was actually found and removed —
+    /// callers use this to detect "this targeted something that never made
+    /// it to the server in the first place" and skip queuing a delete.
+    @discardableResult
+    public func removeOperation(id: String) -> Bool {
+        let descriptor = FetchDescriptor<PendingOperation>(predicate: #Predicate { $0.id == id })
+        guard let existing = try? modelContext.fetch(descriptor).first else { return false }
+        modelContext.delete(existing)
+        try? modelContext.save()
+        return true
+    }
+
+    public func recordFailure(id: String, error: String) {
+        let descriptor = FetchDescriptor<PendingOperation>(predicate: #Predicate { $0.id == id })
+        guard let existing = try? modelContext.fetch(descriptor).first else { return }
+        existing.lastAttemptAt = Date()
+        existing.lastError = error
+        existing.attemptCount += 1
+        try? modelContext.save()
+    }
+}
@@ -0,0 +1,40 @@
+import Foundation
+import SwiftData
+
+/// A queued mutation made while offline, waiting to replay against the live
+/// server. `id` is deliberately overloaded: for actions that create a new
+/// server-side record (pin, star, subscription), it's also the synthesized
+/// placeholder id handed back to the caller immediately — so a matching
+/// delete queued before that create ever syncs can cancel both out by id
+/// instead of hitting a server that's never heard of the placeholder. For
+/// actions that edit an existing record (document/collection updates), it's
+/// deterministic per target id, so a second edit before the first syncs
+/// coalesces into one queued operation instead of piling up.
+@Model
+public final class PendingOperation {
+    @Attribute(.unique) public var id: String
+    public var kind: String
+    public var payload: Data
+    public var createdAt: Date
+    public var lastAttemptAt: Date?
+    public var lastError: String?
+    public var attemptCount: Int
+
+    public init(
+        id: String,
+        kind: String,
+        payload: Data,
+        createdAt: Date,
+        lastAttemptAt: Date? = nil,
+        lastError: String? = nil,
+        attemptCount: Int = 0
+    ) {
+        self.id = id
+        self.kind = kind
+        self.payload = payload
+        self.createdAt = createdAt
+        self.lastAttemptAt = lastAttemptAt
+        self.lastError = lastError
+        self.attemptCount = attemptCount
+    }
+}
@@ -0,0 +1,50 @@
+import Foundation
+
+/// UI-facing snapshot of a queued offline mutation — deliberately not the
+/// `@Model` type itself, so Settings can display it without holding a
+/// reference into the SwiftData store.
+public struct PendingOperationSummary: Identifiable, Sendable {
+    public let id: String
+    public let kind: String
+    public let createdAt: Date
+    public let attemptCount: Int
+    public let lastError: String?
+}
+
+public struct CacheStorageSummary: Sendable {
+    public let itemCount: Int
+    public let totalBytes: Int
+}
+
+public struct SyncFlushSummary: Sendable {
+    public let succeeded: Int
+    public let failed: Int
+}
+
+public struct FullSyncSummary: Sendable {
+    public let collectionsCount: Int
+    public let documentsCount: Int
+    public let errors: [String]
+    public let finishedAt: Date
+}
+
+/// Every mutation `CachingOutlineAPIClient` knows how to queue offline and
+/// replay later. Deliberately a small, explicit set — see its doc comment
+/// for what's excluded and why.
+enum PendingOperationKind: String, Codable, Sendable {
+    case createDocument
+    case updateDocument
+    case updateCollection
+    case createPin
+    case deletePin
+    case createSubscription
+    case deleteSubscription
+    case starDocument
+    case deleteStar
+    case starCollection
+}
+
+/// Shared payload shape for the delete-by-id queueable operations.
+struct IDPayload: Codable, Sendable {
+    let id: String
+}
@@ -1,6 +1,6 @@
 import Foundation

-public struct CreateDocumentRequest: Encodable, Sendable {
+public struct CreateDocumentRequest: Codable, Sendable {
    public let title: String
    public let text: String
    public let collectionId: String
@@ -2,7 +2,7 @@ import Foundation

 /// See `OutlinePin`. `collectionId: nil` = "Pin to Home", non-nil = "Pin to
 /// Collection" — these are distinct actions on the real server.
-public struct CreatePinRequest: Encodable, Sendable {
+public struct CreatePinRequest: Codable, Sendable {
    public let documentId: String
    public let collectionId: String?

@@ -1,7 +1,7 @@
 import Foundation

 /// See `OutlineSubscription` — best-effort shape, not in the vendored spec.
-public struct CreateSubscriptionRequest: Encodable, Sendable {
+public struct CreateSubscriptionRequest: Codable, Sendable {
    public let documentId: String
    public let event: String

@@ -1,6 +1,6 @@
 import Foundation

-public struct StarCollectionRequest: Encodable, Sendable {
+public struct StarCollectionRequest: Codable, Sendable {
    public let collectionId: String

    public init(collectionId: String) {
@@ -1,6 +1,6 @@
 import Foundation

-public struct StarDocumentRequest: Encodable, Sendable {
+public struct StarDocumentRequest: Codable, Sendable {
    public let documentId: String

    public init(documentId: String) {
@@ -1,6 +1,6 @@
 import Foundation

-public struct UpdateCollectionRequest: Encodable, Sendable {
+public struct UpdateCollectionRequest: Codable, Sendable {
    public let id: String
    public let name: String?
    public let description: String?
@@ -1,6 +1,6 @@
 import Foundation

-public struct UpdateDocumentRequest: Encodable, Sendable {
+public struct UpdateDocumentRequest: Codable, Sendable {
    public let id: String
    public let title: String?
    public let text: String?
@@ -0,0 +1,500 @@
+import XCTest
+@testable import OutlineKit
+
+private struct NotStubbed: Error {}
+
+/// Conforms to the full protocol (so it can stand in for `live`), but only
+/// the two methods under test in this file have real behavior — everything
+/// else throws loudly if a test accidentally exercises it.
+private final class StubOutlineAPIClient: OutlineAPIClient, @unchecked Sendable {
+    var documentInfoHandler: (@Sendable (String) async throws -> OutlineDocument)?
+    var listCollectionsHandler: (@Sendable (Int, Int) async throws -> [OutlineCollection])?
+    var updateDocumentHandler: (@Sendable (UpdateDocumentRequest) async throws -> OutlineDocument)?
+    var createPinHandler: (@Sendable (CreatePinRequest) async throws -> OutlinePin)?
+    var deletePinHandler: (@Sendable (String) async throws -> Void)?
+    var listDocumentsHandler: (@Sendable (String?, String?, Int, Int) async throws -> [OutlineDocument])?
+    var createDocumentHandler: (@Sendable (CreateDocumentRequest) async throws -> OutlineDocument)?
+
+    func authInfo() async throws -> OutlineAuthInfo { throw NotStubbed() }
+
+    func documentInfo(id: String) async throws -> OutlineDocument {
+        guard let handler = documentInfoHandler else { throw NotStubbed() }
+        return try await handler(id)
+    }
+
+    func listDocuments(collectionId: String?, parentDocumentId: String?, offset: Int, limit: Int) async throws -> [OutlineDocument] {
+        guard let handler = listDocumentsHandler else { throw NotStubbed() }
+        return try await handler(collectionId, parentDocumentId, offset, limit)
+    }
+
+    func documentsList(_ request: DocumentsListRequest) async throws -> [OutlineDocument] { throw NotStubbed() }
+    func listViewedDocuments(offset: Int, limit: Int) async throws -> [OutlineDocument] { throw NotStubbed() }
+    func searchDocuments(_ request: DocumentSearchRequest) async throws -> [OutlineDocumentSearchResult] { throw NotStubbed() }
+    func searchDocumentTitles(_ request: DocumentSearchTitlesRequest) async throws -> [OutlineDocument] { throw NotStubbed() }
+    func createDocument(_ request: CreateDocumentRequest) async throws -> OutlineDocument {
+        guard let handler = createDocumentHandler else { throw NotStubbed() }
+        return try await handler(request)
+    }
+
+    func updateDocument(_ request: UpdateDocumentRequest) async throws -> OutlineDocument {
+        guard let handler = updateDocumentHandler else { throw NotStubbed() }
+        return try await handler(request)
+    }
+
+    func starDocument(_ request: StarDocumentRequest) async throws -> OutlineStar { throw NotStubbed() }
+    func templatizeDocument(_ request: TemplatizeDocumentRequest) async throws -> OutlineTemplate { throw NotStubbed() }
+    func duplicateDocument(_ request: DuplicateDocumentRequest) async throws -> [OutlineDocument] { throw NotStubbed() }
+    func unpublishDocument(_ request: UnpublishDocumentRequest) async throws -> OutlineDocument { throw NotStubbed() }
+    func archiveDocument(id: String) async throws -> OutlineDocument { throw NotStubbed() }
+    func moveDocument(_ request: MoveDocumentRequest) async throws { throw NotStubbed() }
+    func deleteDocument(_ request: DeleteDocumentRequest) async throws { throw NotStubbed() }
+    func documentInsights(_ request: DocumentInsightsRequest) async throws -> [OutlineDocumentInsight] { throw NotStubbed() }
+    func listRevisions(_ request: ListRevisionsRequest) async throws -> [OutlineRevision] { throw NotStubbed() }
+    func exportDocument(id: String) async throws -> String { throw NotStubbed() }
+    func createShare(_ request: CreateShareRequest) async throws -> OutlineShare { throw NotStubbed() }
+    func shareInfo(documentId: String) async throws -> OutlineShare? { throw NotStubbed() }
+    func updateShare(_ request: UpdateShareRequest) async throws -> OutlineShare { throw NotStubbed() }
+    func listShares(_ request: ListSharesRequest) async throws -> [OutlineShare] { throw NotStubbed() }
+    func revokeShare(id: String) async throws { throw NotStubbed() }
+    func createPin(_ request: CreatePinRequest) async throws -> OutlinePin {
+        guard let handler = createPinHandler else { throw NotStubbed() }
+        return try await handler(request)
+    }
+
+    func listPins(_ request: ListPinsRequest) async throws -> [OutlinePin] { throw NotStubbed() }
+
+    func deletePin(id: String) async throws {
+        guard let handler = deletePinHandler else { throw NotStubbed() }
+        try await handler(id)
+    }
+    func createSubscription(_ request: CreateSubscriptionRequest) async throws -> OutlineSubscription { throw NotStubbed() }
+    func listSubscriptions(_ request: ListSubscriptionsRequest) async throws -> [OutlineSubscription] { throw NotStubbed() }
+    func deleteSubscription(id: String) async throws { throw NotStubbed() }
+    func listViews(_ request: ListViewsRequest) async throws -> [OutlineView] { throw NotStubbed() }
+    func addDocumentUser(_ request: AddDocumentUserRequest) async throws -> OutlineMembership { throw NotStubbed() }
+    func removeDocumentUser(_ request: RemoveDocumentUserRequest) async throws { throw NotStubbed() }
+    func documentUsers(_ request: ListDocumentUsersRequest) async throws -> [OutlineDocumentMember] { throw NotStubbed() }
+    func listUsers(_ request: ListUsersRequest) async throws -> [OutlineUser] { throw NotStubbed() }
+
+    func listCollections(offset: Int, limit: Int) async throws -> [OutlineCollection] {
+        guard let handler = listCollectionsHandler else { throw NotStubbed() }
+        return try await handler(offset, limit)
+    }
+
+    func collectionInfo(id: String) async throws -> OutlineCollection { throw NotStubbed() }
+    func updateCollection(_ request: UpdateCollectionRequest) async throws -> OutlineCollection { throw NotStubbed() }
+    func deleteCollection(id: String) async throws { throw NotStubbed() }
+    func exportCollection(_ request: ExportCollectionRequest) async throws -> OutlineFileOperation { throw NotStubbed() }
+    func starCollection(_ request: StarCollectionRequest) async throws -> OutlineStar { throw NotStubbed() }
+    func listStars(_ request: ListStarsRequest) async throws -> [OutlineStar] { throw NotStubbed() }
+    func deleteStar(id: String) async throws { throw NotStubbed() }
+    func currentUser() async throws -> OutlineUser { throw NotStubbed() }
+}
+
+private struct StubTransportError: Error {}
+
+final class CachingOutlineAPIClientTests: XCTestCase {
+    private func makeCache() throws -> OfflineCacheStore {
+        OfflineCacheStore(modelContainer: try OfflineCacheStore.makeContainer(inMemory: true))
+    }
+
+    private func makeDocument(id: String = "doc-1", title: String = "Hello") -> OutlineDocument {
+        OutlineDocument(
+            id: id,
+            title: title,
+            text: "body",
+            url: "/doc/\(id)",
+            createdAt: Date(timeIntervalSince1970: 0),
+            updatedAt: Date(timeIntervalSince1970: 0)
+        )
+    }
+
+    private func makeCollection(id: String = "col-1", name: String = "Engineering") -> OutlineCollection {
+        OutlineCollection(
+            id: id,
+            name: name,
+            createdAt: Date(timeIntervalSince1970: 0),
+            updatedAt: Date(timeIntervalSince1970: 0)
+        )
+    }
+
+    func testDocumentInfoWritesThroughToCacheOnSuccess() async throws {
+        let stub = StubOutlineAPIClient()
+        let document = makeDocument()
+        stub.documentInfoHandler = { _ in document }
+        let sut = CachingOutlineAPIClient(live: stub, cache: try makeCache())
+
+        let result = try await sut.documentInfo(id: "doc-1")
+
+        XCTAssertEqual(result, document)
+    }
+
+    func testDocumentInfoFallsBackToCacheWhenLiveFails() async throws {
+        let stub = StubOutlineAPIClient()
+        let document = makeDocument()
+        var callCount = 0
+        stub.documentInfoHandler = { _ in
+            callCount += 1
+            if callCount == 1 { return document }
+            throw StubTransportError()
+        }
+        let sut = CachingOutlineAPIClient(live: stub, cache: try makeCache())
+
+        // First call succeeds and populates the cache.
+        _ = try await sut.documentInfo(id: "doc-1")
+        // Second call fails live — should transparently return the cached value.
+        let result = try await sut.documentInfo(id: "doc-1")
+
+        XCTAssertEqual(result, document)
+        XCTAssertEqual(callCount, 2)
+    }
+
+    func testDocumentInfoRethrowsWhenLiveFailsAndCacheIsEmpty() async throws {
+        let stub = StubOutlineAPIClient()
+        stub.documentInfoHandler = { _ in throw StubTransportError() }
+        let sut = CachingOutlineAPIClient(live: stub, cache: try makeCache())
+
+        do {
+            _ = try await sut.documentInfo(id: "doc-1")
+            XCTFail("Expected an error")
+        } catch is StubTransportError {
+            // expected
+        }
+    }
+
+    func testListCollectionsFallsBackToCacheWhenLiveFails() async throws {
+        let stub = StubOutlineAPIClient()
+        let collections = [makeCollection()]
+        var callCount = 0
+        stub.listCollectionsHandler = { _, _ in
+            callCount += 1
+            if callCount == 1 { return collections }
+            throw StubTransportError()
+        }
+        let sut = CachingOutlineAPIClient(live: stub, cache: try makeCache())
+
+        _ = try await sut.listCollections(offset: 0, limit: 25)
+        let result = try await sut.listCollections(offset: 0, limit: 25)
+
+        XCTAssertEqual(result, collections)
+    }
+
+    func testDifferentDocumentIdsAreCachedSeparately() async throws {
+        let stub = StubOutlineAPIClient()
+        let docOne = makeDocument(id: "doc-1", title: "One")
+        let docTwo = makeDocument(id: "doc-2", title: "Two")
+        stub.documentInfoHandler = { id in id == "doc-1" ? docOne : docTwo }
+        let sut = CachingOutlineAPIClient(live: stub, cache: try makeCache())
+
+        _ = try await sut.documentInfo(id: "doc-1")
+        _ = try await sut.documentInfo(id: "doc-2")
+        stub.documentInfoHandler = { _ in throw StubTransportError() }
+
+        let cachedOne = try await sut.documentInfo(id: "doc-1")
+        let cachedTwo = try await sut.documentInfo(id: "doc-2")
+
+        XCTAssertEqual(cachedOne, docOne)
+        XCTAssertEqual(cachedTwo, docTwo)
+    }
+
+    // MARK: - Offline writes
+
+    func testUpdateDocumentQueuesAndAppliesOptimisticallyWhenLiveFails() async throws {
+        let stub = StubOutlineAPIClient()
+        let original = makeDocument(id: "doc-1", title: "Original")
+        stub.documentInfoHandler = { _ in original }
+        stub.updateDocumentHandler = { _ in throw StubTransportError() }
+        let sut = CachingOutlineAPIClient(live: stub, cache: try makeCache())
+
+        // Populate the cache with the base document first (as a real open would).
+        _ = try await sut.documentInfo(id: "doc-1")
+
+        let updated = try await sut.updateDocument(UpdateDocumentRequest(id: "doc-1", title: "Edited Offline"))
+        XCTAssertEqual(updated.title, "Edited Offline")
+
+        // Re-opening the document (still offline) should reflect the optimistic edit.
+        stub.documentInfoHandler = { _ in throw StubTransportError() }
+        let reopened = try await sut.documentInfo(id: "doc-1")
+        XCTAssertEqual(reopened.title, "Edited Offline")
+
+        let pending = await sut.pendingOperations()
+        XCTAssertEqual(pending.count, 1)
+        XCTAssertEqual(pending.first?.kind, "updateDocument")
+    }
+
+    func testUpdateDocumentRethrowsWhenDocumentWasNeverCached() async throws {
+        let stub = StubOutlineAPIClient()
+        stub.updateDocumentHandler = { _ in throw StubTransportError() }
+        let sut = CachingOutlineAPIClient(live: stub, cache: try makeCache())
+
+        do {
+            _ = try await sut.updateDocument(UpdateDocumentRequest(id: "never-seen", title: "x"))
+            XCTFail("Expected an error")
+        } catch is StubTransportError {
+            // expected — nothing to optimistically merge onto
+        }
+    }
+
+    func testSecondOfflineEditCoalescesIntoOneQueuedOperation() async throws {
+        let stub = StubOutlineAPIClient()
+        let original = makeDocument(id: "doc-1", title: "Original")
+        stub.documentInfoHandler = { _ in original }
+        stub.updateDocumentHandler = { _ in throw StubTransportError() }
+        let sut = CachingOutlineAPIClient(live: stub, cache: try makeCache())
+
+        _ = try await sut.documentInfo(id: "doc-1")
+        _ = try await sut.updateDocument(UpdateDocumentRequest(id: "doc-1", title: "First Edit"))
+        _ = try await sut.updateDocument(UpdateDocumentRequest(id: "doc-1", title: "Second Edit"))
+
+        let pending = await sut.pendingOperations()
+        XCTAssertEqual(pending.count, 1)
+    }
+
+    func testPinThenUnpinBeforeSyncCancelsOutWithoutQueuingADelete() async throws {
+        let stub = StubOutlineAPIClient()
+        stub.createPinHandler = { _ in throw StubTransportError() }
+        let sut = CachingOutlineAPIClient(live: stub, cache: try makeCache())
+
+        let pin = try await sut.createPin(CreatePinRequest(documentId: "doc-1"))
+        XCTAssertTrue(pin.id.hasPrefix("pending-"))
+        let pendingCount1 = await sut.pendingOperations().count
+        XCTAssertEqual(pendingCount1, 1)
+
+        try await sut.deletePin(id: pin.id)
+
+        let pendingCount0 = await sut.pendingOperations().count
+        XCTAssertEqual(pendingCount0, 0)
+    }
+
+    func testFlushPendingOperationsReplaysAndClearsOnSuccess() async throws {
+        let stub = StubOutlineAPIClient()
+        let original = makeDocument(id: "doc-1", title: "Original")
+        stub.documentInfoHandler = { _ in original }
+        stub.updateDocumentHandler = { _ in throw StubTransportError() }
+        let sut = CachingOutlineAPIClient(live: stub, cache: try makeCache())
+
+        _ = try await sut.documentInfo(id: "doc-1")
+        _ = try await sut.updateDocument(UpdateDocumentRequest(id: "doc-1", title: "Edited Offline"))
+        let pendingCount1 = await sut.pendingOperations().count
+        XCTAssertEqual(pendingCount1, 1)
+
+        // Network's back — replay should now succeed.
+        stub.updateDocumentHandler = { request in
+            self.makeDocument(id: request.id, title: request.title ?? "")
+        }
+        let summary = await sut.flushPendingOperations()
+
+        XCTAssertEqual(summary.succeeded, 1)
+        XCTAssertEqual(summary.failed, 0)
+        let pendingCount0 = await sut.pendingOperations().count
+        XCTAssertEqual(pendingCount0, 0)
+    }
+
+    func testFlushPendingOperationsRecordsErrorAndKeepsFailedOperation() async throws {
+        let stub = StubOutlineAPIClient()
+        let original = makeDocument(id: "doc-1", title: "Original")
+        stub.documentInfoHandler = { _ in original }
+        stub.updateDocumentHandler = { _ in throw StubTransportError() }
+        let sut = CachingOutlineAPIClient(live: stub, cache: try makeCache())
+
+        _ = try await sut.documentInfo(id: "doc-1")
+        _ = try await sut.updateDocument(UpdateDocumentRequest(id: "doc-1", title: "Edited Offline"))
+
+        // Still offline — replay should fail and keep the operation queued.
+        let summary = await sut.flushPendingOperations()
+
+        XCTAssertEqual(summary.succeeded, 0)
+        XCTAssertEqual(summary.failed, 1)
+        let pending = await sut.pendingOperations()
+        XCTAssertEqual(pending.count, 1)
+        XCTAssertEqual(pending.first?.attemptCount, 1)
+        XCTAssertNotNil(pending.first?.lastError)
+    }
+
+    func testManualOfflineModeSkipsLiveEntirely() async throws {
+        let defaults = UserDefaults(suiteName: "CachingOutlineAPIClientTests.manualOffline")!
+        defaults.removePersistentDomain(forName: "CachingOutlineAPIClientTests.manualOffline")
+        defaults.set(true, forKey: CachingOutlineAPIClient.offlineModeDefaultsKey)
+
+        let stub = StubOutlineAPIClient()
+        var liveCallCount = 0
+        stub.createPinHandler = { _ in
+            liveCallCount += 1
+            return OutlinePin(id: "real-id", documentId: "doc-1", collectionId: nil, index: nil)
+        }
+        let sut = CachingOutlineAPIClient(live: stub, cache: try makeCache(), defaults: defaults)
+
+        let pin = try await sut.createPin(CreatePinRequest(documentId: "doc-1"))
+
+        XCTAssertEqual(liveCallCount, 0, "Manual offline mode should never attempt the live call")
+        XCTAssertTrue(pin.id.hasPrefix("pending-"))
+    }
+
+    /// Regression test: manual offline mode used to only gate writes —
+    /// reads (listCollections, documentInfo, etc.) still hit `live` first
+    /// any time the device actually had a connection, silently defeating
+    /// "skip the network entirely" for the one thing that mattered most:
+    /// the sidebar showing more than what was actually cached.
+    func testManualOfflineModeSkipsLiveForReadsToo() async throws {
+        let defaults = UserDefaults(suiteName: "CachingOutlineAPIClientTests.manualOfflineReads")!
+        defaults.removePersistentDomain(forName: "CachingOutlineAPIClientTests.manualOfflineReads")
+
+        let stub = StubOutlineAPIClient()
+        let cachedCollection = makeCollection(id: "col-1")
+        var liveCallCount = 0
+        stub.listCollectionsHandler = { _, _ in
+            liveCallCount += 1
+            return [cachedCollection]
+        }
+        let cache = try makeCache()
+        let sut = CachingOutlineAPIClient(live: stub, cache: cache, defaults: defaults)
+
+        // Online first — populates the cache normally.
+        let firstResult = try await sut.listCollections(offset: 0, limit: 25)
+        XCTAssertEqual(firstResult, [cachedCollection])
+        XCTAssertEqual(liveCallCount, 1)
+
+        // Flip manual offline mode on, still "connected" (stub would happily
+        // answer) — the live call must not be attempted at all.
+        defaults.set(true, forKey: CachingOutlineAPIClient.offlineModeDefaultsKey)
+        let secondResult = try await sut.listCollections(offset: 0, limit: 25)
+
+        XCTAssertEqual(secondResult, [cachedCollection])
+        XCTAssertEqual(liveCallCount, 1, "listCollections should have served entirely from cache")
+    }
+
+    func testCacheStorageSummaryReflectsCachedItems() async throws {
+        let stub = StubOutlineAPIClient()
+        stub.documentInfoHandler = { _ in self.makeDocument() }
+        let sut = CachingOutlineAPIClient(live: stub, cache: try makeCache())
+
+        _ = try await sut.documentInfo(id: "doc-1")
+        let summary = await sut.cacheStorageSummary()
+
+        XCTAssertEqual(summary.itemCount, 1)
+        XCTAssertGreaterThan(summary.totalBytes, 0)
+
+        await sut.clearCache()
+        let clearedSummary = await sut.cacheStorageSummary()
+        XCTAssertEqual(clearedSummary.itemCount, 0)
+    }
+
+    // MARK: - Full sync
+
+    func testPerformFullSyncNeverRequestsMoreThan100CollectionsPerPage() async throws {
+        let stub = StubOutlineAPIClient()
+        var requestedLimits: [Int] = []
+        // 105 collections across two pages (100 + 5) — regression test for a
+        // real bug: this used to ask for `limit: 250` in one shot, which
+        // Outline's server rejects outright ("Pagination limit is too large
+        // (max 100)"), turning the whole sync into a single silent failure.
+        stub.listCollectionsHandler = { offset, limit in
+            requestedLimits.append(limit)
+            let remaining = max(0, 105 - offset)
+            let count = min(limit, remaining)
+            return (0..<count).map { self.makeCollection(id: "col-\(offset + $0)") }
+        }
+        stub.listDocumentsHandler = { _, _, _, _ in [] }
+        let sut = CachingOutlineAPIClient(live: stub, cache: try makeCache())
+
+        let summary = await sut.performFullSync()
+
+        XCTAssertEqual(summary.collectionsCount, 105)
+        XCTAssertTrue(summary.errors.isEmpty)
+        XCTAssertTrue(requestedLimits.allSatisfy { $0 <= 100 }, "requested limits: \(requestedLimits)")
+    }
+
+    func testPerformFullSyncCachesEachDocumentIndividually() async throws {
+        let stub = StubOutlineAPIClient()
+        stub.listCollectionsHandler = { offset, _ in offset == 0 ? [self.makeCollection(id: "col-1")] : [] }
+        stub.listDocumentsHandler = { _, _, offset, _ in
+            offset == 0 ? [self.makeDocument(id: "doc-1"), self.makeDocument(id: "doc-2")] : []
+        }
+        let cache = try makeCache()
+        let sut = CachingOutlineAPIClient(live: stub, cache: cache)
+
+        let summary = await sut.performFullSync()
+        XCTAssertEqual(summary.documentsCount, 2)
+
+        // A plain documentInfo read (no live call available) should now hit
+        // the cache full sync populated, not just the list-shaped cache key.
+        stub.documentInfoHandler = { _ in throw StubTransportError() }
+        let cachedDoc = try await sut.documentInfo(id: "doc-2")
+        XCTAssertEqual(cachedDoc.id, "doc-2")
+    }
+
+    // MARK: - Offline document creation
+
+    func testCreateDocumentQueuesAndReturnsUsableDocumentWhenOffline() async throws {
+        let stub = StubOutlineAPIClient()
+        stub.createDocumentHandler = { _ in throw StubTransportError() }
+        let sut = CachingOutlineAPIClient(live: stub, cache: try makeCache())
+
+        let created = try await sut.createDocument(
+            CreateDocumentRequest(title: "New Doc", text: "hello", collectionId: "col-1")
+        )
+
+        XCTAssertTrue(created.id.hasPrefix("pending-"))
+        XCTAssertEqual(created.title, "New Doc")
+        XCTAssertEqual(created.text, "hello")
+
+        // It's immediately readable, same as any other cached document.
+        stub.documentInfoHandler = { _ in throw StubTransportError() }
+        let reopened = try await sut.documentInfo(id: created.id)
+        XCTAssertEqual(reopened.title, "New Doc")
+
+        let pending = await sut.pendingOperations()
+        XCTAssertEqual(pending.count, 1)
+        XCTAssertEqual(pending.first?.kind, "createDocument")
+    }
+
+    func testEditingAnUnsyncedCreatedDocumentFoldsIntoTheCreateInsteadOfQueuingAnUpdate() async throws {
+        let stub = StubOutlineAPIClient()
+        stub.createDocumentHandler = { _ in throw StubTransportError() }
+        stub.updateDocumentHandler = { _ in throw StubTransportError() }
+        let sut = CachingOutlineAPIClient(live: stub, cache: try makeCache())
+
+        let created = try await sut.createDocument(
+            CreateDocumentRequest(title: "Untitled", text: "", collectionId: "col-1")
+        )
+        _ = try await sut.updateDocument(UpdateDocumentRequest(id: created.id, title: "Real Title", text: "Real body"))
+
+        let pending = await sut.pendingOperations()
+        XCTAssertEqual(pending.count, 1, "the edit should have folded into the pending create, not added a second operation")
+        XCTAssertEqual(pending.first?.kind, "createDocument")
+
+        stub.documentInfoHandler = { _ in throw StubTransportError() }
+        let reopened = try await sut.documentInfo(id: created.id)
+        XCTAssertEqual(reopened.title, "Real Title")
+        XCTAssertEqual(reopened.text, "Real body")
+    }
+
+    func testFlushingAPendingCreateReconcilesThePlaceholderIdToTheRealOne() async throws {
+        let stub = StubOutlineAPIClient()
+        stub.createDocumentHandler = { _ in throw StubTransportError() }
+        let sut = CachingOutlineAPIClient(live: stub, cache: try makeCache())
+
+        let created = try await sut.createDocument(
+            CreateDocumentRequest(title: "New Doc", text: "hello", collectionId: "col-1")
+        )
+        let realDocument = makeDocument(id: "real-server-id", title: "New Doc")
+        stub.createDocumentHandler = { _ in realDocument }
+
+        let summary = await sut.flushPendingOperations()
+        XCTAssertEqual(summary.succeeded, 1)
+        XCTAssertEqual(summary.failed, 0)
+
+        // The real document is now readable under its real id...
+        stub.documentInfoHandler = { _ in throw StubTransportError() }
+        let byRealId = try await sut.documentInfo(id: "real-server-id")
+        XCTAssertEqual(byRealId.id, "real-server-id")
+
+        // ...and the placeholder is gone rather than left as a dead orphan.
+        do {
+            _ = try await sut.documentInfo(id: created.id)
+            XCTFail("Expected the placeholder cache entry to have been removed")
+        } catch {
+            // expected — nothing left under the old id
+        }
+    }
+}
@@ -408,7 +408,7 @@
 				LD_RUNPATH_SEARCH_PATHS = "@executable_path/Frameworks";
 				"LD_RUNPATH_SEARCH_PATHS[sdk=macosx*]" = "@executable_path/../Frameworks";
 				MACOSX_DEPLOYMENT_TARGET = 27.0;
-				MARKETING_VERSION = 0.0.2;
+				MARKETING_VERSION = 0.0.3;
 				PRODUCT_BUNDLE_IDENTIFIER = com.psmattas.Outpost;
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				REGISTER_APP_GROUPS = YES;
@@ -453,7 +453,7 @@
 				LD_RUNPATH_SEARCH_PATHS = "@executable_path/Frameworks";
 				"LD_RUNPATH_SEARCH_PATHS[sdk=macosx*]" = "@executable_path/../Frameworks";
 				MACOSX_DEPLOYMENT_TARGET = 27.0;
-				MARKETING_VERSION = 0.0.2;
+				MARKETING_VERSION = 0.0.3;
 				PRODUCT_BUNDLE_IDENTIFIER = com.psmattas.Outpost;
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				REGISTER_APP_GROUPS = YES;
@@ -2,11 +2,15 @@
 import AppKit
 import SwiftUI

-struct AboutView: View {
+/// Bare content (icon, name, version, links) with no window chrome — reused
+/// by both the standalone "About Outpost" window (`AboutView`, the standard
+/// macOS app-menu affordance) and the Settings page's own About section, so
+/// the two can't drift out of sync.
+struct AboutInfoView: View {
    private let repositoryURL = URL(string: "https://git.psmattas.com/psmattas/Outpost")!
    private let releasesURL = URL(string: "https://git.psmattas.com/psmattas/Outpost/releases")!

-    private var appName: String {
+    var appName: String {
        Bundle.main.object(forInfoDictionaryKey: "CFBundleName") as? String ?? "Outpost"
    }

@@ -15,7 +19,7 @@ struct AboutView: View {
    /// expected to stay a plain dotted-numeric string, not `0.0.1-ALPHA`.
    private let releaseStage = "ALPHA"

-    private var versionString: String {
+    var versionString: String {
        let shortVersion = Bundle.main.object(forInfoDictionaryKey: "CFBundleShortVersionString") as? String ?? "0.0.1"
        let buildNumber = Bundle.main.object(forInfoDictionaryKey: "CFBundleVersion") as? String ?? "1"
        let stageSuffix = releaseStage.isEmpty ? "" : "-\(releaseStage)"
@@ -66,8 +70,6 @@ struct AboutView: View {
                .font(.caption2)
                .foregroundStyle(.tertiary)
        }
-        .padding(32)
-        .frame(width: 320)
    }

    // No Sparkle-style in-app updater yet — this just opens the releases page
@@ -76,4 +78,12 @@ struct AboutView: View {
        NSWorkspace.shared.open(releasesURL)
    }
 }
+
+struct AboutView: View {
+    var body: some View {
+        AboutInfoView()
+            .padding(32)
+            .frame(width: 320)
+    }
+}
 #endif
@@ -1,5 +1,6 @@
 #if os(macOS)
 import SwiftUI
+import OutlineKit

 /// Uses a plain `Button` + `.popover` rather than `Menu`. A `Menu` whose label
 /// contains the avatar image reliably broke its own sizing on click (even after
@@ -7,10 +8,11 @@ import SwiftUI
 /// label rendering, which a `Button` doesn't go through.
 struct AccountFooter: View {
    @Environment(SessionStore.self) private var session
+    @Environment(AppNavigation.self) private var navigation
    @Environment(\.openURL) private var openURL
    @Environment(\.openWindow) private var openWindow
-    @Environment(\.openSettings) private var openSettings
    @AppStorage("outpost.appearance") private var appearance: AppAppearance = .system
+    @AppStorage(CachingOutlineAPIClient.offlineModeDefaultsKey) private var isOfflineModeEnabled = false
    @State private var isMenuPresented = false
    @State private var isShowingLogoutConfirmation = false
    @State private var isShowingProfile = false
@@ -93,8 +95,17 @@ struct AccountFooter: View {
            .padding(.horizontal, 6)
            .padding(.vertical, 4)

+            Toggle("Offline Mode", isOn: $isOfflineModeEnabled)
+                .padding(.horizontal, 6)
+                .padding(.vertical, 4)
+
            menuItem("Profile…") { isShowingProfile = true }
-            menuItem("Preferences…") { openSettings() }
+            // Deferred a tick: setting this synchronously in the same call
+            // that dismisses this popover collides two AppKit window/layer
+            // transactions in the same runloop turn (visible in the console
+            // as "Invalid attempt to open a new transaction during CA
+            // commit") — letting the popover's dismissal finish first avoids it.
+            menuItem("Settings…") { Task { @MainActor in navigation.isShowingSettings = true } }

            Divider()

@@ -1,40 +0,0 @@
-#if os(macOS)
-import SwiftUI
-
-struct PreferencesView: View {
-    @Environment(SessionStore.self) private var session
-    @AppStorage("outpost.appearance") private var appearance: AppAppearance = .system
-    @State private var isShowingLogoutConfirmation = false
-
-    var body: some View {
-        Form {
-            Section("Appearance") {
-                Picker("Appearance", selection: $appearance) {
-                    ForEach(AppAppearance.allCases) { option in
-                        Text(option.label).tag(option)
-                    }
-                }
-                .pickerStyle(.segmented)
-                .labelsHidden()
-            }
-
-            Section("Account") {
-                LabeledContent("Signed in as", value: session.userName ?? "—")
-                if let email = session.userEmail {
-                    LabeledContent("Email", value: email)
-                }
-                if let teamName = session.teamName {
-                    LabeledContent("Workspace", value: teamName)
-                }
-
-                Button("Log Out…", role: .destructive) {
-                    isShowingLogoutConfirmation = true
-                }
-            }
-        }
-        .formStyle(.grouped)
-        .frame(width: 380, height: 300)
-        .logoutConfirmationDialog(isPresented: $isShowingLogoutConfirmation, session: session)
-    }
-}
-#endif
@@ -0,0 +1,41 @@
+#if os(macOS)
+import SwiftUI
+
+/// Swapped into the real sidebar's content slot (search field, collections
+/// tree, account footer) while Settings is open — same sidebar, different
+/// content, rather than a separate mini sidebar nested inside a page. "Done"
+/// clears `AppNavigation.isShowingSettings`, which puts the collections tree
+/// back.
+struct SettingsSidebarList: View {
+    @Binding var selection: SettingsSection?
+    let onDone: () -> Void
+
+    var body: some View {
+        VStack(spacing: 0) {
+            HStack {
+                Text("Settings")
+                    .font(.headline)
+                Spacer()
+            }
+            .padding(.horizontal, 16)
+            .padding(.vertical, 12)
+
+            Divider()
+
+            List(SettingsSection.allCases, selection: $selection) { section in
+                Label(section.title, systemImage: section.icon)
+                    .tag(section)
+            }
+            .listStyle(.sidebar)
+
+            Divider()
+
+            Button("Done", action: onDone)
+                .keyboardShortcut(.cancelAction)
+                .buttonStyle(.borderedProminent)
+                .frame(maxWidth: .infinity)
+                .padding(12)
+        }
+    }
+}
+#endif
@@ -0,0 +1,420 @@
+#if os(macOS)
+import SwiftUI
+import OutlineKit
+
+/// Settings *detail* content for one section — the section list itself now
+/// lives in `ContentView_macOS`'s real sidebar (swapped in over the
+/// collections tree while `AppNavigation.isShowingSettings` is set, not a
+/// separate mini sidebar of its own), so this view only ever renders
+/// whichever section is currently selected.
+struct SettingsView: View {
+    let section: SettingsSection
+
+    @Environment(SessionStore.self) private var session
+    @AppStorage("outpost.appearance") private var appearance: AppAppearance = .system
+    @AppStorage(CachingOutlineAPIClient.offlineModeDefaultsKey) private var isOfflineModeEnabled = false
+    @AppStorage("outpost.fullLocalSyncEnabled") private var isFullLocalSyncEnabled = false
+    @AppStorage("outpost.advancedOptionsEnabled") private var isAdvancedOptionsEnabled = false
+    @State private var isShowingLogoutConfirmation = false
+    @State private var isShowingAdvancedWarning = false
+    @State private var storageSummary: CacheStorageSummary?
+    @State private var pendingOperations: [PendingOperationSummary] = []
+    @State private var isSyncing = false
+    @State private var isClearingCache = false
+    @State private var didClearCache = false
+    @State private var lastFullSyncSummary: FullSyncSummary?
+    @State private var lastFlushSummary: SyncFlushSummary?
+
+    /// Full Local Sync and cache-clearing both need a real connection to be
+    /// safe — clearing while offline (or letting Full Local Sync think it
+    /// should be running) can leave the app with nothing local to show and
+    /// no way to refetch it. "Offline" here means either a real dropped
+    /// connection or the user's own manual toggle — both leave the app with
+    /// no server to talk to.
+    private var isEffectivelyOnline: Bool {
+        session.networkMonitor.isOnline && !isOfflineModeEnabled
+    }
+
+    var body: some View {
+        // GeometryReader + `minHeight` (not `maxHeight`) is the actual fix for
+        // "center short content inside a ScrollView" — a ScrollView proposes
+        // effectively unbounded height to its content, so `maxHeight: .infinity`
+        // alone just resolves to the content's own intrinsic size and does
+        // nothing; forcing a `minHeight` equal to the real viewport height is
+        // what gives `aboutDetail`'s own centered alignment somewhere to
+        // actually center within. Harmless for the other (already
+        // top/leading-aligned) sections — short ones just get blank space
+        // below, same as before.
+        GeometryReader { geometry in
+            ScrollView {
+                sectionDetail
+                    .padding(28)
+                    .frame(maxWidth: .infinity, minHeight: geometry.size.height, alignment: .topLeading)
+            }
+        }
+        .frame(maxWidth: .infinity, maxHeight: .infinity)
+        .background(.background)
+        .task { await refreshSyncState() }
+        .logoutConfirmationDialog(isPresented: $isShowingLogoutConfirmation, session: session)
+    }
+
+    @ViewBuilder
+    private var sectionDetail: some View {
+        switch section {
+        case .appearance: appearanceDetail
+        case .account: accountDetail
+        case .offlineSync: offlineSyncDetail
+        case .advanced: advancedDetail
+        case .about: aboutDetail
+        }
+    }
+
+    private var sectionHeader: some View {
+        Text(section.title)
+            .font(.title.bold())
+    }
+
+    // MARK: - Appearance
+
+    private var appearanceDetail: some View {
+        VStack(alignment: .leading, spacing: 16) {
+            sectionHeader
+            Picker("Appearance", selection: $appearance) {
+                ForEach(AppAppearance.allCases) { option in
+                    Text(option.label).tag(option)
+                }
+            }
+            .pickerStyle(.segmented)
+            .labelsHidden()
+            .frame(maxWidth: 320)
+        }
+    }
+
+    // MARK: - Account
+
+    private var accountDetail: some View {
+        VStack(alignment: .leading, spacing: 16) {
+            sectionHeader
+            VStack(alignment: .leading, spacing: 10) {
+                labeledRow("Signed in as", session.userName ?? "—")
+                if let email = session.userEmail {
+                    labeledRow("Email", email)
+                }
+                if let teamName = session.teamName {
+                    labeledRow("Workspace", teamName)
+                }
+            }
+            .frame(maxWidth: 420)
+
+            Button("Log Out…", role: .destructive) {
+                isShowingLogoutConfirmation = true
+            }
+        }
+    }
+
+    // MARK: - Offline & Sync
+
+    private var offlineSyncDetail: some View {
+        VStack(alignment: .leading, spacing: 20) {
+            sectionHeader
+
+            VStack(alignment: .leading, spacing: 6) {
+                Toggle("Offline Mode", isOn: $isOfflineModeEnabled)
+                Text("Skip the network entirely and work from what's already been cached. Turn this off to reconnect.")
+                    .font(.caption)
+                    .foregroundStyle(.secondary)
+            }
+            .frame(maxWidth: 480, alignment: .leading)
+
+            VStack(alignment: .leading, spacing: 6) {
+                Toggle("Full Local Sync", isOn: $isFullLocalSyncEnabled)
+                    .disabled(!isEffectivelyOnline)
+                Text("Keep a complete local copy of every collection and document, not just what's been opened — the whole workspace stays browsable offline. Runs automatically in the background once on; no need to trigger it by hand.")
+                    .font(.caption)
+                    .foregroundStyle(.secondary)
+                if !isEffectivelyOnline {
+                    Text("Requires an internet connection to turn on or off.")
+                        .font(.caption2)
+                        .foregroundStyle(.orange)
+                }
+            }
+            .frame(maxWidth: 480, alignment: .leading)
+            .help(isEffectivelyOnline ? "" : "Full Local Sync needs a real connection — it can't safely turn on (or off) while offline.")
+
+            if isFullLocalSyncEnabled {
+                VStack(alignment: .leading, spacing: 6) {
+                    HStack(spacing: 8) {
+                        if isSyncing {
+                            ProgressView().controlSize(.small)
+                            Text("Syncing…")
+                                .font(.caption)
+                                .foregroundStyle(.secondary)
+                        } else {
+                            Button("Sync Now") { Task { await runFullSync() } }
+                                .controlSize(.small)
+                                .disabled(!isEffectivelyOnline)
+                            if let lastFullSyncSummary {
+                                Text(fullSyncSummaryText(lastFullSyncSummary))
+                                    .font(.caption)
+                                    .foregroundStyle(lastFullSyncSummary.errors.isEmpty ? Color.secondary : Color.red)
+                            }
+                        }
+                    }
+                    if let lastFullSyncSummary, !isSyncing {
+                        ForEach(Array(lastFullSyncSummary.errors.enumerated()), id: \.offset) { _, message in
+                            Text(message)
+                                .font(.caption2)
+                                .foregroundStyle(.red)
+                        }
+                    }
+                }
+            }
+
+            Divider()
+                .frame(maxWidth: 480)
+
+            pendingOperationsRow
+                .frame(maxWidth: 480, alignment: .leading)
+        }
+    }
+
+    private var pendingOperationsRow: some View {
+        VStack(alignment: .leading, spacing: 8) {
+            HStack {
+                Text("Pending Sync")
+                    .font(.subheadline.weight(.medium))
+                Spacer()
+                if isSyncing {
+                    ProgressView().controlSize(.small)
+                } else {
+                    Button("Retry") { Task { await retrySync() } }
+                        .buttonStyle(.plain)
+                        .font(.caption)
+                        .foregroundStyle(Color.accentColor)
+                        .disabled(pendingOperations.isEmpty)
+                }
+            }
+
+            if pendingOperations.isEmpty {
+                Text("Everything's synced.")
+                    .font(.caption)
+                    .foregroundStyle(.secondary)
+            } else {
+                VStack(alignment: .leading, spacing: 6) {
+                    ForEach(pendingOperations) { operation in
+                        pendingOperationRow(operation)
+                    }
+                }
+            }
+        }
+    }
+
+    private func pendingOperationRow(_ operation: PendingOperationSummary) -> some View {
+        HStack(alignment: .top, spacing: 6) {
+            Image(systemName: operation.lastError == nil ? "clock" : "exclamationmark.triangle.fill")
+                .foregroundStyle(operation.lastError == nil ? Color.secondary : Color.orange)
+                .font(.caption)
+            VStack(alignment: .leading, spacing: 2) {
+                Text(operationLabel(operation.kind))
+                    .font(.caption)
+                if let lastError = operation.lastError {
+                    Text(lastError)
+                        .font(.caption2)
+                        .foregroundStyle(.red)
+                }
+            }
+        }
+    }
+
+    private func operationLabel(_ kind: String) -> String {
+        switch kind {
+        case "updateDocument": return "Document edit"
+        case "updateCollection": return "Collection rename"
+        case "createPin": return "Pin"
+        case "deletePin": return "Unpin"
+        case "createSubscription": return "Subscribe"
+        case "deleteSubscription": return "Unsubscribe"
+        case "starDocument", "starCollection": return "Star"
+        case "deleteStar": return "Unstar"
+        default: return kind
+        }
+    }
+
+    // MARK: - Advanced
+
+    /// Everything here either does something destructive (clearing the
+    /// cache Full Local Sync just spent minutes building) or doesn't exist
+    /// yet — gating all of it behind an off-by-default master toggle plus a
+    /// confirmation to turn that toggle on is the safeguard: nothing here
+    /// can be reached by accident, and nothing outside this section can
+    /// touch the cache at all, so there's no path to "messed up Full Local
+    /// Sync" that doesn't go through this screen on purpose.
+    private var advancedDetail: some View {
+        VStack(alignment: .leading, spacing: 20) {
+            sectionHeader
+
+            VStack(alignment: .leading, spacing: 6) {
+                Toggle("Enable Advanced Options", isOn: advancedOptionsBinding)
+                Text("Off by default on purpose. Turning this on unlocks things that can cause unintended behavior, including permanently losing your local cache.")
+                    .font(.caption)
+                    .foregroundStyle(.secondary)
+            }
+            .frame(maxWidth: 480, alignment: .leading)
+
+            Divider()
+                .frame(maxWidth: 480)
+
+            VStack(alignment: .leading, spacing: 12) {
+                comingSoonRow("Export All Data")
+                comingSoonRow("Developer Diagnostics")
+                comingSoonRow("Reset Local Database")
+            }
+            .frame(maxWidth: 480, alignment: .leading)
+
+            Divider()
+                .frame(maxWidth: 480)
+
+            VStack(alignment: .leading, spacing: 6) {
+                HStack(spacing: 10) {
+                    Text("Clear All Cache")
+                    Spacer()
+                    if didClearCache {
+                        Label("Cleared", systemImage: "checkmark")
+                            .font(.caption)
+                            .foregroundStyle(.secondary)
+                    }
+                    Button(role: .destructive) {
+                        Task { await clearCache() }
+                    } label: {
+                        if isClearingCache {
+                            ProgressView().controlSize(.small)
+                        } else {
+                            Text("Clear")
+                        }
+                    }
+                    .buttonStyle(.borderedProminent)
+                    .tint(.red)
+                }
+                if let storageSummary {
+                    Text("\(storageSummary.itemCount) items — \(formattedBytes(storageSummary.totalBytes))")
+                        .font(.caption)
+                        .foregroundStyle(.secondary)
+                }
+                Text("Deletes every cached collection and document, including anything Full Local Sync built, and anything still waiting to sync. Doesn't touch the server. This is the only place that can — it works even while offline, which is exactly why it's behind this toggle.")
+                    .font(.caption2)
+                    .foregroundStyle(.secondary)
+            }
+            .disabled(!isAdvancedOptionsEnabled || isClearingCache)
+            .opacity(isAdvancedOptionsEnabled ? 1 : 0.4)
+            .frame(maxWidth: 480, alignment: .leading)
+        }
+        .confirmationDialog(
+            "Enable Advanced Options?",
+            isPresented: $isShowingAdvancedWarning,
+            titleVisibility: .visible
+        ) {
+            Button("Enable", role: .destructive) { isAdvancedOptionsEnabled = true }
+            Button("Cancel", role: .cancel) {}
+        } message: {
+            Text("These settings can cause unintended behavior, including permanently losing your local cache. Only continue if you know what you're doing.")
+        }
+    }
+
+    /// Never writes `true` directly — turning the toggle on only opens the
+    /// warning dialog; only that dialog's own "Enable" button actually sets
+    /// it. Turning off doesn't need confirmation.
+    private var advancedOptionsBinding: Binding<Bool> {
+        Binding(
+            get: { isAdvancedOptionsEnabled },
+            set: { newValue in
+                if newValue {
+                    isShowingAdvancedWarning = true
+                } else {
+                    isAdvancedOptionsEnabled = false
+                }
+            }
+        )
+    }
+
+    private func comingSoonRow(_ title: String) -> some View {
+        HStack {
+            Text(title)
+            Spacer()
+            Text("Coming Soon")
+                .font(.caption)
+                .foregroundStyle(.secondary)
+        }
+        .disabled(true)
+        .opacity(0.5)
+    }
+
+    // MARK: - About
+
+    private var aboutDetail: some View {
+        VStack(spacing: 16) {
+            sectionHeader
+            AboutInfoView()
+                .frame(maxWidth: 420)
+        }
+        .frame(maxWidth: .infinity, maxHeight: .infinity, alignment: .center)
+    }
+
+    // MARK: - Helpers
+
+    private func labeledRow(_ label: String, _ value: String) -> some View {
+        HStack {
+            Text(label)
+                .foregroundStyle(.secondary)
+            Spacer()
+            Text(value)
+        }
+        .font(.callout)
+    }
+
+    private func formattedBytes(_ bytes: Int) -> String {
+        ByteCountFormatter.string(fromByteCount: Int64(bytes), countStyle: .file)
+    }
+
+    private func fullSyncSummaryText(_ summary: FullSyncSummary) -> String {
+        if summary.errors.isEmpty {
+            return "Synced \(summary.documentsCount) documents across \(summary.collectionsCount) collections."
+        }
+        return "Synced with \(summary.errors.count) error\(summary.errors.count == 1 ? "" : "s")."
+    }
+
+    private func refreshSyncState() async {
+        guard let cachingClient = session.cachingClient else { return }
+        storageSummary = await cachingClient.cacheStorageSummary()
+        pendingOperations = await cachingClient.pendingOperations()
+    }
+
+    private func runFullSync() async {
+        guard let cachingClient = session.cachingClient, !isSyncing else { return }
+        isSyncing = true
+        defer { isSyncing = false }
+        lastFullSyncSummary = await cachingClient.performFullSync()
+        await refreshSyncState()
+    }
+
+    private func retrySync() async {
+        guard let cachingClient = session.cachingClient, !isSyncing else { return }
+        isSyncing = true
+        defer { isSyncing = false }
+        lastFlushSummary = await cachingClient.flushPendingOperations()
+        await refreshSyncState()
+    }
+
+    private func clearCache() async {
+        guard let cachingClient = session.cachingClient else { return }
+        isClearingCache = true
+        defer { isClearingCache = false }
+        await cachingClient.clearCache()
+        await refreshSyncState()
+        didClearCache = true
+        Task {
+            try? await Task.sleep(for: .seconds(2))
+            didClearCache = false
+        }
+    }
+}
+#endif
@@ -10,7 +10,7 @@ struct CollectionRowView: View {
        } icon: {
            if let emoji = collection.emojiIcon {
                Text(emoji)
-            } else if let symbolName = collection.icon.flatMap(OutlineIconMapping.sfSymbolName) {
+            } else if let symbolName = collection.icon.flatMap({ OutlineIconMapping.sfSymbolName(for: $0) }) {
                Image(systemName: symbolName)
                    .foregroundStyle(tintColor)
            } else {
@@ -4,6 +4,8 @@ import OutlineKit

 struct ContentView_macOS: View {
    @Environment(SessionStore.self) private var session
+    @Environment(AppNavigation.self) private var navigation
+    @AppStorage(CachingOutlineAPIClient.offlineModeDefaultsKey) private var isOfflineModeEnabled = false
    /// The landing state — no collection selected yet is what Home actually
    /// means, so this starts `true` rather than auto-selecting the first
    /// collection the way this used to work.
@@ -26,11 +28,73 @@ struct ContentView_macOS: View {
        globalSearchQuery.trimmingCharacters(in: .whitespacesAndNewlines)
    }

+    /// `@Environment(AppNavigation.self)` doesn't hand out `$`-bindings on its
+    /// own (that's `@Bindable`'s job, and introducing one in `body` would
+    /// mean restructuring it away from a single implicit-return expression)
+    /// — a manually-built `Binding` over the same reference is simpler here.
+    private var selectedSettingsSectionBinding: Binding<SettingsSection?> {
+        Binding(
+            get: { navigation.selectedSettingsSection },
+            set: { navigation.selectedSettingsSection = $0 }
+        )
+    }
+
    var body: some View {
+        // A totally separate top-level branch, not content swapped inside
+        // one persistent `NavigationSplitView` — that was tried first (an
+        // `if/else` inside a single split view, then an explicit `.id()` on
+        // just the detail pane) and neither reliably replaced the detail
+        // pane's content on macOS: `NavigationSplitView` bridges to
+        // `NSSplitViewController`, and swapping a `NavigationStack` with
+        // real push history for a plain view inside one persisting instance
+        // doesn't propagate the way plain SwiftUI identity rules would
+        // suggest. A different `if` branch is a genuinely different view
+        // hierarchy, so there's no existing split view instance for AppKit
+        // to get confused about reusing.
+        if navigation.isShowingSettings {
+            settingsContent
+        } else {
+            mainContent
+        }
+    }
+
+    private var settingsContent: some View {
+        NavigationSplitView {
+            SettingsSidebarList(
+                selection: selectedSettingsSectionBinding,
+                onDone: { navigation.isShowingSettings = false }
+            )
+            .navigationSplitViewColumnWidth(min: 220, ideal: 260)
+        } detail: {
+            SettingsView(section: navigation.selectedSettingsSection ?? .appearance)
+        }
+        .navigationTitle("")
+        .toolbar {
+            ToolbarItem(placement: .navigation) {
+                HStack(spacing: 6) {
+                    Image(systemName: "gearshape.fill")
+                    Text("Settings")
+                }
+                .font(.headline)
+                .padding(.horizontal, 10)
+                .padding(.vertical, 4)
+                .background(.fill.tertiary, in: Capsule())
+            }
+        }
+    }
+
+    private var mainContent: some View {
        NavigationSplitView {
            VStack(spacing: 0) {
                SidebarSearchField(text: $globalSearchQuery)
                Divider()
+                if isOfflineModeEnabled {
+                    OfflineBanner(isManual: true)
+                    Divider()
+                } else if !session.networkMonitor.isOnline {
+                    OfflineConnectionPromptBanner(onEnableOfflineMode: { isOfflineModeEnabled = true })
+                    Divider()
+                }
                sidebar
                AccountFooter()
            }
@@ -92,6 +156,7 @@ struct ContentView_macOS: View {
        isContextualSearchExpanded = false
        selectedCollection = nil
        isShowingHome = true
+        navigation.isShowingSettings = false
        replaceDocumentPath(with: [])
    }

@@ -12,6 +12,7 @@ import OutlineKit
 struct DocumentReaderView: View {
    @Environment(SessionStore.self) private var session
    @Environment(StarStore.self) private var starStore
+    @AppStorage(CachingOutlineAPIClient.offlineModeDefaultsKey) private var isOfflineModeEnabled = false

    @State private var viewModel: DocumentReaderViewModel
    let apiClient: OutlineAPIClient
@@ -56,6 +57,15 @@ struct DocumentReaderView: View {
        self.onDocumentCreated = onDocumentCreated
    }

+    /// New Document, editing, pin/star/subscribe, and Full Width all queue
+    /// and sync later (see `CachingOutlineAPIClient`) — everything else here
+    /// (sharing, permissions, move/archive/delete/duplicate/templatize,
+    /// history, insights, export) hits the server directly with no offline
+    /// path, so it's disabled rather than left to fail confusingly on tap.
+    private var isEffectivelyOnline: Bool {
+        session.networkMonitor.isOnline && !isOfflineModeEnabled
+    }
+
    var body: some View {
        ScrollView {
            VStack(alignment: .leading, spacing: 12) {
@@ -82,6 +92,7 @@ struct DocumentReaderView: View {
                    NativeTextViewWrapper(
                        text: $viewModel.text,
                        configuration: .init(heightBehavior: .fitsContent),
+                        documentId: viewModel.documentId,
                        isEditable: viewModel.isEditing
                    )

@@ -110,7 +121,8 @@ struct DocumentReaderView: View {
                } label: {
                    Image(systemName: "square.and.arrow.up")
                }
-                .help("Share")
+                .help(isEffectivelyOnline ? "Share" : "Sharing needs an internet connection")
+                .disabled(!isEffectivelyOnline)
                .popover(isPresented: $isShowingShareSheet, arrowEdge: .bottom) {
                    DocumentShareSheet(apiClient: apiClient, documentId: viewModel.documentId)
                }
@@ -235,7 +247,8 @@ struct DocumentReaderView: View {
            viewModel.isPinned,
            viewModel.isInsightsEnabled ?? false,
            viewModel.isFullWidth,
-            viewModel.isEditing
+            viewModel.isEditing,
+            isEffectivelyOnline
        ].map(String.init).joined(separator: "-")
    }

@@ -305,27 +318,33 @@ struct DocumentReaderView: View {
        Button("Permissions…") {
            isShowingShareSheet = true
        }
+        .disabled(!isEffectivelyOnline)

        Divider()

        Button("Templatize") {
            Task { await templatize() }
        }
+        .disabled(!isEffectivelyOnline)
        Button("Duplicate") {
            Task { await duplicate() }
        }
+        .disabled(!isEffectivelyOnline)
        Button("Unpublish") {
            isShowingUnpublishConfirmation = true
        }
+        .disabled(!isEffectivelyOnline)
        Button("Archive…") {
            isShowingArchiveConfirmation = true
        }
+        .disabled(!isEffectivelyOnline)

        Divider()

        Button("Move") {
            isShowingMoveSheet = true
        }
+        .disabled(!isEffectivelyOnline)
        // Multipart file upload is its own subsystem — deferred rather than
        // half-built here.
        Button("Import Document…") {}
@@ -342,9 +361,13 @@ struct DocumentReaderView: View {
        Button("History") {
            isShowingHistorySheet = true
        }
+        .disabled(!isEffectivelyOnline)
        Button("Insights") {
            isShowingInsightsSheet = true
        }
+        .disabled(!isEffectivelyOnline)
+        // Present/Search in Document both read `documents.info`, which is
+        // read-through cached — they work offline on whatever's cached.
        Button("Present") {
            isShowingPresentSheet = true
        }
@@ -354,6 +377,7 @@ struct DocumentReaderView: View {
        Button("Download") {
            Task { await download() }
        }
+        .disabled(!isEffectivelyOnline)
        Button("Copy") {
            Task { await copyMarkdown() }
        }
@@ -370,6 +394,7 @@ struct DocumentReaderView: View {
            get: { viewModel.isInsightsEnabled ?? false },
            set: { _ in Task { await toggleInsights() } }
        ))
+        .disabled(!isEffectivelyOnline)
        // Confirmed against a live server: there's no per-document embeds
        // field. Only a workspace-level setting exists, and that's not
        // reachable via the API either (no `team.update` endpoint in the
@@ -386,6 +411,7 @@ struct DocumentReaderView: View {
        Button("Delete…", role: .destructive) {
            isShowingDeleteConfirmation = true
        }
+        .disabled(!isEffectivelyOnline)
    }

    private func star() async {
@@ -0,0 +1,27 @@
+#if os(macOS)
+import SwiftUI
+
+/// Shown at the top of the sidebar whenever the app is offline — either for
+/// real (`NetworkMonitor` reports no connection) or because the user turned
+/// on the manual "Offline Mode" toggle. Cached collections/documents keep
+/// browsing working either way, but the user should know they might be
+/// looking at stale data.
+struct OfflineBanner: View {
+    /// Whether this is the user's own "Offline Mode" toggle rather than a
+    /// real dropped connection — same banner slot, different explanation.
+    var isManual: Bool = false
+
+    var body: some View {
+        HStack(spacing: 8) {
+            Image(systemName: "wifi.slash")
+                .foregroundStyle(.orange)
+            Text(isManual ? "Offline Mode — showing cached content" : "Offline — showing cached content")
+                .font(.callout)
+            Spacer(minLength: 0)
+        }
+        .padding(.horizontal, 12)
+        .padding(.vertical, 8)
+        .background(Color.orange.opacity(0.12))
+    }
+}
+#endif
@@ -0,0 +1,30 @@
+#if os(macOS)
+import SwiftUI
+
+/// Shown in the sidebar when the network is actually down and the user
+/// hasn't turned on Offline Mode themselves yet. Deliberately doesn't change
+/// any fetch behavior on its own — reads still try live and fall back to
+/// cache the normal way (see `CachingOutlineAPIClient`) until the user
+/// actually taps the button here, same as `RemoteChangesBanner` never
+/// auto-refreshes on their behalf either.
+struct OfflineConnectionPromptBanner: View {
+    let onEnableOfflineMode: () -> Void
+
+    var body: some View {
+        HStack(spacing: 8) {
+            Image(systemName: "wifi.slash")
+                .foregroundStyle(.orange)
+            Text("No connection")
+                .font(.callout)
+            Spacer(minLength: 8)
+            Button("Turn On Offline Mode", action: onEnableOfflineMode)
+                .buttonStyle(.borderedProminent)
+                .tint(.orange)
+                .controlSize(.small)
+        }
+        .padding(.horizontal, 12)
+        .padding(.vertical, 8)
+        .background(Color.orange.opacity(0.12))
+    }
+}
+#endif
@@ -57,25 +57,33 @@ final class HomeViewModel {
    /// Fetches fresh pinned docs and the current tab's documents to compare
    /// against what's displayed, without replacing either. Bails silently
    /// on a fetch failure rather than treating it as "changed" — a
-    /// transient network hiccup shouldn't pop the refresh banner.
+    /// transient network hiccup (or, offline, `listPins` failing outright —
+    /// it isn't one of the cached endpoints) shouldn't pop the refresh
+    /// banner. This needs the *throwing* pinned-fetch specifically: the
+    /// plain `fetchPinned()` used elsewhere collapses any failure to `[]`,
+    /// which used to read here as "pins changed" against whatever was
+    /// already displayed and falsely popped the banner on every offline
+    /// poll.
    func checkForRemoteChanges(tab: HomeTab) async {
-        async let freshPinned = fetchPinned()
+        async let freshPinnedTask = fetchPinnedThrowing()
        guard let freshTab = try? await fetch(tab: tab) else { return }
-        let pinned = await freshPinned
+        guard let pinned = try? await freshPinnedTask else { return }
        if Self.fingerprint(pinned) != Self.fingerprint(pinnedDocuments)
            || Self.fingerprint(freshTab) != Self.fingerprint(documents(for: tab)) {
            hasRemoteChanges = true
        }
    }

+    private func fetchPinned() async -> [OutlineDocument] {
+        (try? await fetchPinnedThrowing()) ?? []
+    }
+
    /// `pins.list` only returns pin records, not the documents themselves —
    /// fetches each pinned document individually. Pins are a small curated
    /// set (unlike a full collection tree), so the N+1 here is acceptable
    /// where it wouldn't be in the sidebar.
-    private func fetchPinned() async -> [OutlineDocument] {
-        guard let pins = try? await apiClient.listPins(ListPinsRequest(collectionId: nil)) else {
-            return []
-        }
+    private func fetchPinnedThrowing() async throws -> [OutlineDocument] {
+        let pins = try await apiClient.listPins(ListPinsRequest(collectionId: nil))
        var documents: [OutlineDocument] = []
        for pin in pins {
            if let document = try? await apiClient.documentInfo(id: pin.documentId) {
@@ -14,6 +14,7 @@ import AppKit
@main
 struct OutpostApp: App {
    @State private var session = SessionStore()
+    @State private var navigation = AppNavigation()
    @AppStorage("outpost.appearance") private var appearance: AppAppearance = .system

    #if os(macOS)
@@ -25,6 +26,7 @@ struct OutpostApp: App {
        WindowGroup {
            RootView()
                .environment(session)
+                .environment(navigation)
                #if os(iOS)
                .preferredColorScheme(appearance.colorScheme)
                #endif
@@ -41,6 +43,16 @@ struct OutpostApp: App {
                    openWindow(id: "about")
                }
            }
+            // No `Settings {}` scene anymore — Settings renders inside the
+            // root window (see `AppNavigation`), not a separate popup, so
+            // ⌘, has to be wired up by hand instead of coming for free.
+            CommandGroup(replacing: .appSettings) {
+                Button("Settings…") {
+                    navigation.isShowingSettings = true
+                }
+                .keyboardShortcut(",")
+                .disabled(!session.isSignedIn)
+            }
            CommandGroup(after: .appSettings) {
                Divider()
                Button("Log Out…") {
@@ -63,11 +75,6 @@ struct OutpostApp: App {
                .disablesFullScreen()
        }
        .windowResizability(.contentSize)
-
-        Settings {
-            PreferencesView()
-                .environment(session)
-        }
        #endif
    }

@@ -0,0 +1,40 @@
+import Observation
+
+enum SettingsSection: String, CaseIterable, Identifiable, Hashable {
+    case appearance, account, offlineSync, advanced, about
+
+    var id: String { rawValue }
+
+    var title: String {
+        switch self {
+        case .appearance: return "Appearance"
+        case .account: return "Account"
+        case .offlineSync: return "Offline & Sync"
+        case .advanced: return "Advanced"
+        case .about: return "About"
+        }
+    }
+
+    var icon: String {
+        switch self {
+        case .appearance: return "paintbrush"
+        case .account: return "person.crop.circle"
+        case .offlineSync: return "arrow.triangle.2.circlepath"
+        case .advanced: return "wrench.and.screwdriver"
+        case .about: return "info.circle"
+        }
+    }
+}
+
+/// Cross-cutting UI state that doesn't belong to any one screen. Lives at
+/// `OutpostApp` (so both `RootView`'s content and its `⌘,` command can reach
+/// it) and is read wherever something needs to open Settings (the profile
+/// menu) or render it — as a swap of the *existing* sidebar/detail panes in
+/// `ContentView_macOS`, not a separate popup window or an overlay that hides
+/// the sidebar.
+@Observable
+@MainActor
+final class AppNavigation {
+    var isShowingSettings = false
+    var selectedSettingsSection: SettingsSection? = .appearance
+}
@@ -5,6 +5,19 @@ struct RootView: View {
    @Environment(SessionStore.self) private var session
    @State private var welcomeName: String?
    @State private var starStore = StarStore()
+    @AppStorage("outpost.fullLocalSyncEnabled") private var isFullLocalSyncEnabled = false
+    @AppStorage(CachingOutlineAPIClient.offlineModeDefaultsKey) private var isOfflineModeEnabled = false
+
+    /// Real connectivity is only half of "can talk to the server" — the
+    /// manual Offline Mode toggle is the other half. Syncing needs to
+    /// resume on either one clearing, not just a real reconnect: turning
+    /// the toggle off while the network had been up the whole time never
+    /// changes `networkMonitor.isOnline`, so keying the flush task off that
+    /// alone left pending operations stuck until the next real network
+    /// blip.
+    private var isEffectivelyOnline: Bool {
+        session.networkMonitor.isOnline && !isOfflineModeEnabled
+    }

    var body: some View {
        ZStack {
@@ -32,6 +45,48 @@ struct RootView: View {
                starStore.reset()
            }
        }
+        // Replay whatever queued up while offline the moment either signal
+        // clears — a real reconnect, or the user turning Offline Mode back
+        // off — no need to wait for the user to open Settings and hit Retry.
+        // Also catches Full Local Sync back up immediately, rather than
+        // leaving it to wait out the rest of the periodic loop below.
+        //
+        // The flush itself gets a retry loop with a cooloff, not just one
+        // attempt: a single transient failure (one bad operation, a blip
+        // mid-flush) used to leave everything else stuck until the user
+        // manually hit Retry or connectivity changed again. Keeps retrying
+        // every 5 minutes for as long as *anything* is still pending and
+        // this signal stays on — stops on its own once the queue is empty,
+        // and `.task(id:)` cancels/restarts it automatically if
+        // isEffectivelyOnline flips again in the meantime.
+        .task(id: isEffectivelyOnline) {
+            guard isEffectivelyOnline, let cachingClient = session.cachingClient else { return }
+            if isFullLocalSyncEnabled {
+                _ = await cachingClient.performFullSync()
+            }
+            while !Task.isCancelled {
+                _ = await cachingClient.flushPendingOperations()
+                let remaining = await cachingClient.pendingOperations()
+                guard !remaining.isEmpty else { break }
+                try? await Task.sleep(for: .seconds(300))
+            }
+        }
+        // Fully automatic — this is the only place Full Local Sync actually
+        // runs from (Settings' "Sync Now" is just an on-demand nudge at the
+        // same call). Syncs immediately whenever this task (re)starts, which
+        // covers both "just switched on" and "was already on at launch" —
+        // `.task(id:)` restarts on either, an `@AppStorage`-backed toggle
+        // changing anywhere updates every view reading that key — then every
+        // 20 minutes after, for as long as it stays enabled.
+        .task(id: isFullLocalSyncEnabled) {
+            guard isFullLocalSyncEnabled else { return }
+            while !Task.isCancelled {
+                if isEffectivelyOnline, let cachingClient = session.cachingClient {
+                    _ = await cachingClient.performFullSync()
+                }
+                try? await Task.sleep(for: .seconds(1200))
+            }
+        }
    }

    private func startWelcomeTransition(_ result: AuthViewModel.AuthResult) {
@@ -17,6 +17,16 @@ final class SessionStore {
    var teamName: String?
    var teamAvatarURL: URL?
    private(set) var apiClient: OutlineAPIClient?
+    /// Same object as `apiClient` when the offline cache is available — kept
+    /// as a separately-typed reference so Settings can reach cache/sync-queue
+    /// specific methods (`flushPendingOperations`, `performFullSync`, etc.)
+    /// without downcasting the protocol-typed `apiClient` everywhere.
+    private(set) var cachingClient: CachingOutlineAPIClient?
+    let networkMonitor = NetworkMonitor()
+    /// `nil` only if the on-disk SwiftData store failed to open (e.g. disk
+    /// full) — in that case `apiClient` falls back to talking to the server
+    /// directly with no offline cache, rather than failing sign-in outright.
+    private let cacheStore: OfflineCacheStore?

    var serverURL: URL? {
        defaults.string(forKey: Self.serverURLDefaultsKey).flatMap(URL.init(string:))
@@ -26,23 +36,32 @@ final class SessionStore {
        self.tokenStore = tokenStore
        self.defaults = defaults
        self.isSignedIn = (try? tokenStore.token()) != nil
+        self.cacheStore = (try? OfflineCacheStore.makeContainer()).map(OfflineCacheStore.init(modelContainer:))

        if isSignedIn, let serverURL {
-            apiClient = LiveOutlineAPIClient(
-                configuration: OutlineConfiguration(baseURL: serverURL),
-                tokenStore: tokenStore
-            )
+            (apiClient, cachingClient) = Self.makeAPIClient(serverURL: serverURL, tokenStore: tokenStore, cache: cacheStore)
        }
    }

    func signIn(serverURL: URL, user: OutlineUser, team: OutlineTeam) {
        defaults.set(serverURL.absoluteString, forKey: Self.serverURLDefaultsKey)
-        apiClient = LiveOutlineAPIClient(
+        (apiClient, cachingClient) = Self.makeAPIClient(serverURL: serverURL, tokenStore: tokenStore, cache: cacheStore)
+        apply(user: user, team: team, serverURL: serverURL)
+        isSignedIn = true
+    }
+
+    private static func makeAPIClient(
+        serverURL: URL,
+        tokenStore: TokenStoring,
+        cache: OfflineCacheStore?
+    ) -> (OutlineAPIClient, CachingOutlineAPIClient?) {
+        let live = LiveOutlineAPIClient(
            configuration: OutlineConfiguration(baseURL: serverURL),
            tokenStore: tokenStore
        )
-        apply(user: user, team: team, serverURL: serverURL)
-        isSignedIn = true
+        guard let cache else { return (live, nil) }
+        let caching = CachingOutlineAPIClient(live: live, cache: cache)
+        return (caching, caching)
    }

    func signOut() {
@@ -55,6 +74,7 @@ final class SessionStore {
        teamName = nil
        teamAvatarURL = nil
        apiClient = nil
+        cachingClient = nil
    }

    /// Re-fetches user/workspace name/logo on relaunch, when the token survived but this
@@ -0,0 +1,36 @@
+import Foundation
+import Network
+import Observation
+
+/// Backs the sidebar's offline badge — purely a UI signal. Unrelated to
+/// `CachingOutlineAPIClient`'s own fallback logic, which reacts to actual
+/// request failures rather than pre-checking reachability.
+@Observable
+@MainActor
+final class NetworkMonitor {
+    private(set) var isOnline = true
+
+    private let monitor = NWPathMonitor()
+    private let queue = DispatchQueue(label: "com.outpost.network-monitor")
+
+    init() {
+        // Weak on the outer closure (it's held by `monitor` for the object's
+        // whole lifetime, so a strong capture here would be a retain cycle),
+        // then unwrapped once into a plain strong local — the inner `Task`
+        // closure capturing that local `self` is what a nested closure needs
+        // to be consistent about capture semantics with its enclosing one.
+        monitor.pathUpdateHandler = { [weak self] path in
+            guard let self else { return }
+     
+            let online = path.status == .satisfied
+            Task { @MainActor in
+                self.isOnline = online
+            }
+        }
+        monitor.start(queue: queue)
+    }
+
+    deinit {
+        monitor.cancel()
+    }
+}