XStats/ARCHITECTURE.md

XStats

macOS 14+ menu-bar system monitor. Swift 6 language mode, AppKit status item and panels hosting SwiftUI, no third-party dependencies. The Xcode project is generated from project.yml by XcodeGen; everything testable lives in the local Swift package.

• App/ — main.swift and the asset catalog.
• Widget/ — the sandboxed WidgetKit extension (“System overview”), embedded in Contents/PlugIns. It samples CPU, memory, disk and battery itself through Metrics, so it works without the app.
• Helper/ — the privileged helper (XStatsHelper) and its launchd plist, embedded in the app bundle for SMAppService.daemon.
• Packages/XStatsKit/Sources/Localization — tr(_:), language resolution and nine-language catalogs (see below).
• Packages/XStatsKit/Sources/SMC — the AppleSMC user client, fan control, temperature key discovery.
• Packages/XStatsKit/Sources/Metrics — one sampler per metric and MetricsHub; power and CPU frequency (PowerSampler), disk activity and NVMe SMART (DiskSamplers), Bluetooth battery, the SQLite history store.
• Packages/XStatsKit/Sources/Cleaner — cleanup rules, SafetyGuard, CleanEngine, the app uninstaller's leftover search and the launchd startup-item list.
• Packages/XStatsKit/Sources/Updates — the update manifest and the download → verify → replace → relaunch steps.
• Packages/XStatsKit/Sources/HelperShared — the XPC protocol and maintenance commands shared by the app and the helper.
• Packages/XStatsKit/Sources/WebDAVSync — manual WebDAV GET/PUT and endpoint-specific Keychain passwords.
• Packages/XStatsKit/Sources/XStatsUI — design tokens, panel pages, settings, menu-bar renderer, app controller, snapshot renderer.
• Packages/XStatsKit/Tests — metrics, SMC decoding, cleanup safety, updates, UI logic and localization.
• server/api — the Fiber/GORM update API, SQLite installation counters and server-rendered statistics dashboard.

Build

Xcode 26 or later is required — CommandLineTools does not ship the SwiftUI macro plugins.

brew install go-task xcodegen
task build            # Release build, then replace /Applications/XStats.app and relaunch
task test             # swift test in the package

Versions read 2026.09.21.01 (0106): MARKETING_VERSION uses the build date plus a daily index. The first build of a day ends in .01, later builds increment the index, and a new day resets it to .01. The four-digit CURRENT_PROJECT_VERSION independently goes up by one on every task build (BUMP=0 skips both changes). Internal build numbers never reset, so every package has a larger CFBundleVersion than the one before. Every task build runs Scripts/install_local.sh: it ends the running app (the helper restores fans and sleep when the connection drops), deletes the old /Applications/XStats.app, moves the new bundle there so no copy stays in the build folder, re-registers it with Launch Services, and relaunches. Only one XStats ever exists on the machine, so Spotlight and the widget gallery never show duplicates. INSTALL=0 compiles without installing; Scripts/release.sh uses it and installs the notarized build at the end.

project.yml defaults to ad-hoc signing so the project opens anywhere. The Taskfile.yml passes the first Developer ID Application identity from the keychain (and --timestamp for Release) when there is one. task release runs Scripts/release.sh: build, verify team, timestamp and hardened runtime on both binaries, notarize and staple the app, build and notarize the DMG, write the online-update zip and appcast.json, and write a Homebrew cask (auto_updates true). The helper derives its client requirement from its own signing team at run time, so no team ID is hard-coded.

Sampling

MetricsHub is an actor that runs one loop. AppModel.demand describes what is on screen — which menu-bar items are enabled, whether the panel is open and on which tab — and the hub samples only that: CPU always; memory and network cheaply; GPU, disk, processes, sensors and fans only when a visible surface needs them. Disk is read at most every 30 s, battery every 10 s. The loop pauses on screen sleep, system sleep and session switch.

Things that are easy to get wrong and are handled on purpose:

• host_processor_info returns kernel-allocated memory; it is vm_deallocated every sample.
• getifaddrs' if_data counters are 32-bit and wrap at 4 GiB; network uses NET_RT_IFLIST2 and if_data64.
• Memory follows Activity Monitor: app memory is internal − purgeable pages; the page size comes from host_page_size (16 KB on Apple Silicon).
• Process CPU time and wall time are both in mach absolute units, so their ratio needs no timebase conversion.
• Core types come from hw.perflevelN; logical CPUs are numbered from the lowest performance level up.

SMC

Temperatures are not hard-coded per chip. On first use the sampler enumerates every SMC key once (≈3,800 keys in about 10 ms on an M5 Max), groups Tp*/Te* as CPU, Tg* as GPU, Tm* as memory, TB* as battery and Ts0P/Ts1P as palm rest, keeps keys whose first reading is plausible, and samples at most 12 per group.

Fans are read without privileges. Writing needs root and goes through the helper. On M5 the mode key (F0md) accepts a direct write; M1–M4 first need Ftst=1 and a pause while thermalmonitord lets go. The firmware records only manual or automatic, not who set it, so a fan in manual mode that XStats did not set is shown as controlled by another program.

Helper

Protocol 5 removes the identifier-only ad-hoc authentication fallback. Ad-hoc apps refuse helper registration and unregister any previously registered helper without connecting to it. Fan and lid-closed controls require team signing; maintenance operations keep their existing admin-prompt fallback. Readiness requires an authenticated version handshake, not just an enabled SMAppService registration. For older helpers, the client unregisters the service before re-registering the current bundle and verifying its version. Unregister/handshake failures leave privileged calls disabled and surface an error.

Registered with SMAppService.daemon; RunAtLoad so that an unclean exit is repaired at boot. The XPC interface is a fixed list of operations — no arbitrary commands — and each connection gets setCodeSigningRequirement. State that must be undone (manual fans, disabled sleep) is persisted to /Library/Application Support/XStats/helper-state.plist and reverted when the last client disconnects or at the next start. The helper exits after 30 s without clients.

Cleanup

Every rule lists candidate items; every item passes SafetyGuard twice — at scan and again right before deletion, because apps start in between.

• Deny by default: an item must sit strictly inside an allow-listed root under the home folder, never be the root itself, contain no .. or control characters, and still pass after symlinks are resolved (resolution can only reject, never allow).
• Under Application Support, only folders named like caches (Code Cache, GPUCache, CacheStorage, …) are allowed.
• Any path component matching a protected keyword (keychains, password managers, VPNs, cookies, history, …) is rejected.
• Reverse-DNS cache folders whose app is running are skipped; browser rules are blocked while the browser runs; items modified in the last two minutes count as in use.

Regenerable caches are deleted outright; user files go to the Trash. Each action is appended to ~/Library/Logs/XStats/cleanup.log as a JSON line.

Disk tools

The disk page is also where users act on the disk. DiskToolsController (XStatsUI/State) fronts four pieces of read-mostly logic in Cleaner/DiskTools.swift, each testable without the UI:

• SpaceScanner walks a root (the home folder) once, sums every top-level entry and keeps the largest files; packages (.app, .photoslibrary, …) count as one item. It never follows symlinks and skips folders it cannot read. canTrash allows Trash only for files inside the home folder, outside Library, with no hidden path component, checked again after resolving symlinks; everything else only gets "reveal in Finder".
• VolumeVerifier runs diskutil verifyVolume / (read-only, no privileges) and reduces the output to OK / problem plus the offending line.
• LocalSnapshots parses tmutil listlocalsnapshots /. Deleting goes through the helper (deleteLocalSnapshots, protocol version 4) and falls back to a one-off administrator prompt; both paths only accept identifiers shaped like 2026-09-14-120000 (HelperShared/LocalSnapshotCommand).
• MountedVolumes lists browsable non-root volumes; ejecting uses NSWorkspace.

Menu bar, popovers and main window

MenuBarController owns the status items. In the separate layout every enabled metric gets its own NSStatusItem (created in reverse so they read left to right) and opens a 320 pt popover for that metric; in the combined layout a single item opens CombinedPopoverView: a status overview with one row per enabled metric, plus tabs that switch to each metric's full popover content (PopoverDetail, shared with the separate layout). While a detail tab is showing, AppModel.openPopover is set to that metric so sampling matches the standalone popover.

Popovers are borderless, non-activating NSPanels. The SwiftUI tree is created on open and destroyed on close, so a hidden popover costs nothing. Height comes from measuring a flat, scroll-free copy of the same view; placeholders keep that height stable until data arrives, and the window is resized without animation because animating it makes SwiftUI re-lay out every frame. Charts are drawn with Canvas, not Swift Charts.

The main window reuses the popover content with isDetailPage set (all sections, taller charts) next to the dashboard and tool pages. Windows use a transparent, full-size-content title bar with an empty compact toolbar, so the traffic lights sit on the same ground colour as the sidebar and line up with the 40 pt page header; the app switches to a regular activation policy while a window is open and back to accessory when all are closed.

Network details

NetworkController runs only while it is needed:

• Connection probe — an unprivileged SOCK_DGRAM ICMP echo (ConnectivityProbe), matched on sequence number and a random payload token because the kernel rewrites the identifier.
• Interface and addresses — SCDynamicStore / SCPreferences for the primary and physical service, getifaddrs for addresses, CoreWLAN for signal and rate.
• Public IP — Cloudflare trace (ipify as fallback) for the address only. Location, ASN, network type, native / broadcast and the cleanliness score come from cleanip.io/cli?json=1, queried directly from each Mac by PublicAddressLookup. The endpoint only reports the caller's own address, so AddressFamilyRequest opens one Network.framework connection pinned to IPv4 and one pinned to IPv6 (URLSession cannot choose the family) and speaks plain HTTP/1.1 over TLS; when a pinned connection cannot be set up it falls back to URLSession and keeps the answer only if it is for the same family. If cleanip.io sees a different exit than Cloudflare (split-routing proxies), its address is shown. Results are cached per IP for an hour in memory and for a week on disk (failed lookups are not cached), and a 429 stops further calls until the next UTC day. Country codes are validated before being used as flag file names. server/geoip/ still holds the systemd timer that syncs MaxMind GeoLite2 onto getopenstats.com/geoip/ (account and key in /etc/openstats/maxmind.env on the server); the app no longer downloads those files, they are kept for other uses.
• Per-process traffic — cumulative bytes from /usr/bin/nettop, diffed between samples.
• DNS — networksetup -setdnsservers through the helper (protocol 3), which re-validates the service name and every address; without the helper, a one-off administrator prompt runs the same fixed command.

Online updates

Battery and Bluetooth

The battery item reuses BatterySampler (IOKit power sources, sampled every 10 s while the item is in the menu bar or its popover / page is open). BatteryPopover is both the popover and the main-window page (DetailPage). The 24-hour charge curve comes from the history database, which gained a battery column (migrated with ALTER TABLE on first open); HistoryRecorder.loadBattery() queries it independently of the History page's range. Macs without a battery show only Bluetooth devices, and the menu-bar segment falls back to the Bluetooth device with the lowest battery.

BluetoothController (XStatsUI/State) wraps BluetoothBatteryReader, which shells out to system_profiler and takes a second or two, so it polls only on demand: every minute while the battery popover / page or the System page is open, every five minutes when the menu bar needs it (the low-battery hint or a Mac without a battery), otherwise not at all. AppModel.bluetoothDemand derives that from the same visibility state as demand.

UpdateController posts the current version and a hashed random installation ID to https://getopenstats.com/api/v1/update/check at launch and daily. The original 32-byte random value is generated with SecRandomCopyBytes and remains in the device-only Keychain; no hardware serial number is used. The response has the same release manifest fields previously read from the static appcast (version, date, notes taken from CHANGELOG.md by Scripts/appcast.py, zip URL, sha256 and size). An update is installed only after: sha256 matches, the zip holds exactly one .app, its bundle ID and version match, SecStaticCodeCheckValidity passes with a requirement pinned to the running app's team, and spctl --assess accepts it (notarized). The old bundle is renamed into a same-volume temporary folder, the new one moved into place (restored on failure; an administrator prompt is used when the folder is not writable), and a detached shell waits for the process to exit before reopening the app. After an update the old helper may still be running; the app unregisters an outdated helper, re-registers the bundled version, and verifies the protocol before privileged calls resume.

server/api is one Go program. Fiber exposes POST /api/v1/update/check, authenticated PUT /api/v1/releases/current, and the aggregate GET /stats dashboard. GORM uses github.com/libtnb/sqlite with WAL and one database connection so concurrent checks cannot compete for SQLite's single writer. Each installation row stores only the SHA-256 installation ID, current version, first/last check times and check count; request IPs and monitoring data are not persisted. The release endpoint requires XSTATS_RELEASE_TOKEN. Scripts/publish_release.sh uploads artifacts first and then submits the generated appcast through Scripts/publish_api.py, keeping the static and API manifests based on the same release metadata.

server/api/Dockerfile cross-compiles a CGO-free binary for amd64 and arm64, then runs it as the distroless nonroot user with /data as the writable SQLite volume. When a branch push changes server/**, .github/workflows/server-image.yml builds both platforms and publishes ghcr.io/<owner>/xstats-server:<sanitized-branch>-<full-commit-sha>. Pull requests do not run this workflow.

WebDAV settings sync

Account login, OAuth callbacks and the old account backend have been removed. Sync only needs the user's WebDAV server and does not run at startup, on wake or on settings changes.

WebDAVSync uses Basic authentication over HTTPS and reads/writes xstats-settings.json in an existing directory via GET/PUT. The temporary URLSession does not share cookies or credentials, uses normal certificate validation, refuses redirects, and streams downloads with a 1 MB limit. GET requires HTTP 200; PUT accepts 200, 201 or 204. Writes are not retried automatically. See WebDAV PUT semantics.

SyncController runs on the main actor and allows one request at a time. Upload requires confirmation and overwrites the remote file without merging. Download validates a SettingsBackup envelope (format, version, timestamp and SettingsDocument schema), then waits for confirmation before applying the existing per-field validation. Cancellation and failures do not change local preferences.

SettingsDocument remains an explicit allowlist. WebDAV credentials, connection settings, local page, helper state, monitoring data and history are excluded. Directory URL and username are saved separately in local defaults. Passwords use the file-based login Keychain service work.12306.xstats.webdav, with a separate account hash for each endpoint and username. Password storage must succeed before new connection details are committed. JSON backups are not additionally encrypted at rest.

Configure every Mac separately. This version does not create remote directories, poll in the background, merge concurrent edits, or use iCloud. A missing remote file requires an initial upload.

Power, disk and history

• System, adapter and battery power come from SMC PSTR, PDTR, PPBR. GPU power comes from the IOReport Energy Model GPU Energy counter; CPU energy counters on recent chips barely update, so CPU power is not shown. Cluster frequencies are residency-weighted averages of CPU Complex Performance States, using the voltage-states*-sram tables of pmgr (Hz on older chips, MHz on newer ones). Each IOReport sample costs about 5 ms of CPU, so it runs at most every 2 s and only while a page shows it.
• Disk activity diffs IOBlockStorageDriver statistics; SSD health reads the NVMe SMART log through the system NVMeSMARTLib plug-in (no root).
• HistoryRecorder folds each sample into a per-minute record (averages, CPU and temperature peaks, worst memory pressure) and writes it to history.sqlite; records older than 8 days are pruned hourly. Queries bucket by 1, 5 or 30 minutes and charts break lines across gaps.

Localization

Source strings are Simplified Chinese. Scripts/l10n_wrap.py wraps every Chinese literal in tr(...) (skipping logger calls, case patterns and multi-line strings) and lists the keys. tr returns the source for Simplified Chinese. English uses the Swift tables; Traditional Chinese, Japanese, Korean, German, Spanish, French and Arabic load bundled TSV catalogs from Localization/Resources. Exact keys take priority, followed by templates with {} or numbered placeholders. Captured strings are translated recursively; inserted values are not reinterpreted as placeholders. Missing entries fall back to English, then the source. Translation tables are immutable; global language and caches share a lock because background collectors also call tr.

The language picker uses a searchable native popover, native language names, a selected checkmark, and keyboard navigation. Search accepts Chinese, English, native names and language codes. Automatic detection walks global AppleLanguages in preference order, distinguishing zh-Hans from zh-Hant/TW/HK/MO and falling back to English if no supported language is found. Existing system, chinese and english preference values and WebDAV settings remain readable.

Changing language rebuilds SwiftUI roots and AppKit menu/window titles. Each SwiftUI window and popover receives the selected locale and layout direction; Arabic uses right-to-left layout and isolates interpolated paths/numbers with Unicode directional isolates. Dates use L10n.locale. For remote geographic data available only in Chinese/English, other languages use English names; country names use the locale. Some macOS-provided names follow the application's AppleLanguages on the next launch.

The nine supported languages are zh-Hans, zh-Hant, ja, ko, en, de, es, fr and ar. Snapshots accept these codes through --snapshot

--language , include the language picker, and record missing translations in untranslated.txt. New interface strings must be added to all catalogs; coverage and placeholder checks accompany the localization tests.

--snapshot <dir> renders every main-window page, popover, settings section and the menu bar in light and dark, through real NSHostingViews in off-screen windows — ImageRenderer washes out pages that contain bitmaps.