XStats/ARCHITECTURE.md

XStats architecture

macOS 14+ menu-bar system monitor. Swift 6 language mode, AppKit status item and panels hosting SwiftUI. The Xcode project is generated from project.yml by XcodeGen; the app's testable components live in the local Swift package. For directory layout, build, test, and release instructions, see DEVELOPMENT.md.

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.

The sandboxed WidgetKit extension samples CPU, memory, disk, and battery through Metrics independently, so it remains useful when the app is not running. AI, IP, and calendar widgets instead read a credential-free App Group snapshot. The main app precomputes an eight-day holiday and almanac window; missing coverage is shown as unavailable, not guessed from weekdays. The large month-calendar widget reads lightweight six-week grids for the current and next month from the same snapshot. It keeps Gregorian dates visible if that cache is missing, without inventing lunar or holiday annotations. The daily Token widget receives only per-provider totals and the local day, never session logs; its displayed count resets at local midnight even if the main app has not refreshed yet. The tomorrow-work widget uses the official 2026 holiday schedule to distinguish statutory holidays, adjusted days off, ordinary weekends, and makeup workdays; later years need their own confirmed schedule before receiving those specific labels. The single seasonal-calendar setting covers dog days, traditional plum-rain days, and the nine cold periods. Month cells and the large month widget show only phase starts and the plum-rain exit; the small daily widget and selected-day details keep the exact day count. Existing dog-day or plum-rain preferences migrate to the combined setting.

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, derived from the helper's own signing team rather than a hard-coded team ID. 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.

AI process explanations

ProcessExplainer uses only the on-device Apple Intelligence model. It checks framework and macOS support before exposing the action, then checks model availability at request time. If the device, system setting or model is unavailable, the explanation card shows the reason and does not call another provider. Successful requests stream local output and can be cancelled. The model receives process identity, path, signer and resource usage; nothing is sent to a CLI or network service. Model response instructions follow the resolved application language.

Calendar

CalendarMenuBarController owns a separate, opt-in status item, independent of the metrics layout and MetricsHub. It reuses StatusPanel, updates the displayed date every minute and on day/time-zone changes or wake, and stops its timer when disabled. CalendarPopover uses a six-week Gregorian grid (1900–2100) and month/year navigation. Clicking a day opens an almanac page in the same panel; returning preserves the selected date and month. CalendarAlmanac loads Tyme's daily advice, deities and hour fortunes only for the selected day and caches the value model by civil-date ID. The twelve-hour grid uses early Zi through Hai, excluding the next day's late Zi entry at 23:00; each cell exposes its exact time range in a tooltip. Browsing history preserves the selection across midnight; a selection on today follows the new day.

CalendarEngine is the sole adapter for the pinned MIT-licensed Tyme4Swift 1.5.0 dependency. All Tyme calls run on MainActor because upstream exposes mutable static tables; only value models leave the adapter. Civil dates use the system time zone and calendar day arithmetic, not 24-hour intervals. Tibetan conversion is guarded to the upstream Gregorian coverage 1951-01-08 through 2051-02-11. Holiday data currently ends in 2026; unknown years show a notice. Plum-rain dates describe traditional calendar rules, not observed or forecast weather.

Calendar enablement, visible features and week start persist through AppSettings and the optional fields in SettingsDocument. Older backups preserve those settings. Additional calendars default off and appear only in selected-day details. There is no event access or network request at runtime. Use --snapshot <directory> --calendar-only for deterministic light/dark calendar screenshots without starting unrelated samplers or scans.

AI usage and quotas

The local Codex provider reads JSONL rollouts from CODEX_HOME (default ~/.codex), including sessions and archived_sessions. It never reads credentials or calls quota APIs; independent quota providers do that only while the master AI Usage switch is enabled. Parsing runs in a background actor pinned to a dedicated serial executor, so a cold scan (tens of seconds over a multi-gigabyte log directory) never occupies a Swift concurrency cooperative thread and cannot stall per-second metric sampling. It uses bounded line buffers and a SQLite checkpoint store at ~/Library/Application Support/XStats/ai-usage.sqlite. Each source/path row atomically stores file identity, size, mtime, newline-aligned byte offset and Codable parser/aggregate state. The preview state is stored only when the final line is still unterminated, so the common case keeps one copy. Rows whose files were not seen in a completed scan are pruned, which covers rollouts moved to archived_sessions, deleted project directories and superseded parser namespaces. Unchanged files reuse stored results even after restart. Appends validate prefix/boundary hashes and read only the suffix; truncation, replacement, parser namespace or time-zone changes rebuild that file. An unterminated final line is previewed separately from committed state, so completing it cannot double-count usage. No raw log lines, prompts or credentials are persisted. Directory metadata is still enumerated on each scheduled refresh; only currently discovered files contribute to totals. The dashboard defaults to the last 365 local-calendar days by model, and shows input/output tokens, cache hit rate, record count, daily totals and model ranking. The menu bar shows today's token total. Cached input is a subset of input; reasoning is a subset of output, so neither is added twice. Rows are aggregated by day and model before leaving the provider, and ordered by day then model, so ModelTokenUsage.id stays unique and an unchanged corpus produces an equal report. Duplicate session IDs and unchanged cumulative snapshots are excluded. Child replayed history only seeds the cumulative baseline until the first task_started, which always follows that history; started_at is not compared against the session creation time, because a subagent's started_at is its parent turn's start and recent Codex builds omit the field entirely. Unknown models remain unknown. Local logs cannot reliably identify the paying account or usage on other devices. No cost, subscription limits or HTTP success rates are inferred from them. The separate quota snapshot prefers the installed Codex CLI's local app-server account/rateLimits/read; the CLI owns token refresh and XStats receives only rate-limit data. If that path is unavailable, XStats queries Codex wham/usage using its cached CLI OAuth token. Claude uses its CLI OAuth token for api/oauth/usage. It maps five-hour and seven-day windows, plus Claude's model-specific weekly windows, without combining them with local token totals. Direct credential discovery is repeated on each refresh; Codex reads auth.json under CODEX_HOME or the standard locations, while Claude reads its CLI credential file or a non-interactive Keychain item. Tokens are not persisted by XStats. Each provider's last successful quota snapshot is stored in a separate table of ai-usage.sqlite, without credentials. The controller restores it before the first network request and labels it with its fetch time. Requests use isolated URL sessions and reject redirects so bearer tokens cannot be forwarded. Codex app-server uses bounded stdio JSONL and falls back to direct HTTP if unavailable. An HTML 403 from an intermediary is a transient network failure, not proof of expired login. The existing per-provider Sub2API option is tried only after both automatic Codex paths fail. Missing or expired credentials clear that provider's quota display; transient errors keep the last successful result marked stale across restarts. Authentication failures or removal of a manual account delete that provider's cached snapshot. Both quota readers stop when AI Usage is disabled; disabled providers are hidden while their cached snapshot remains available on re-enable. Codex and Claude Code each have an optional, independently configured Sub2API source, tried only when that provider's direct quota fetch fails. Each HTTPS base URL, admin email and account ID remain in local preferences outside settings backups; passwords use separate Keychain items. The fallback signs in to its configured server, reads the account record to verify its platform (openai or anthropic), then reads /api/v1/admin/accounts/{id}/usage with source=active&force=false. If the detailed endpoint is unavailable, the account's extra fields provide coarser five-hour and weekly windows. Claude may also expose Sonnet and Fable weekly windows. Credentials and quota results are never sent to XStats servers; the UI marks fallback results as Sub2API. When one provider has a subscription snapshot, the menu bar AI reading shows its name and remaining percentage. It prefers the weekly window (or five-hour window if weekly is unavailable); the tooltip shows the chosen window and reset time without crowding the 22-point menu bar. When both sources are enabled and either has quota data, the item shows a compact named reading for each source; one without quota data shows a dash. The tooltip lists reset times and missing data by source. Without any subscription snapshot it keeps the local daily Token reading. The AI menu bar item follows the global or per-item style. Ring, pie, meter, and dot styles show remaining quota beside its percentage for each available source; a source without quota shows a dash rather than a zero gauge. Since quota history is not stored, global history or line styles use a current-value ring for this item. Icon style uses the bundled OpenAI and Claude logo shapes for the corresponding quota source, including a dash when that source has no quota; aggregated local-only tokens keep the generic AI icon. The quota detail card presents remaining allowance (not used allowance) and, when the server provides a reset date, a separate bar for elapsed time in that five-hour or seven-day window. Allowance turns red as it runs low; the reset bar turns green as reset approaches and updates while the view is open. The UI follows CC Switch's filter/summary/trend/model-table organization, implemented in SwiftUI. The desktop toolbar groups source controls and actions. In the compact menu-bar popover, its header owns refresh and AI Usage settings; the content shows a source switch only when multiple sources are enabled. Token totals use compact notation with exact hover/VoiceOver values. Cache details are disclosed on demand. AI usage settings open in a separate window so users can copy account details from another app without closing the form. Unsaved Sub2API fields stay in memory for the current app session across page changes; passwords are not written to preferences. Since source data is aggregated by day, all three activity modes cover the same trailing 365 days: daily uses one cell per day; weekly uses a seven-cell-high bar per calendar week; cumulative sums usage from the window start through the selected week and uses the same bar grid. Zero weeks have no lit cells. Partial weeks include only days inside the window through today. The mode switch lives in the Token activity header, not in a date-range toolbar. Summary and model ranking follow the mode: daily means today, weekly means the current calendar week, and cumulative means the current calendar month (all through now, using the local calendar). The heatmap independently keeps its 365-day window. Pointer hover immediately shows exact daily/weekly/cumulative counts above the chart; the same label is available to accessibility. The narrow popover lays cells out at their design size and scrolls the year grid horizontally, initially at the recent end; the wide panel shrinks cells to fit instead. Numbers and dates follow the app language rather than the system locale. Pointer selection fades only the selected control background (180 ms); keyboard selection and background data refresh do not animate the data layout. Reduced motion uses the existing quick fade.

Claude Code is a second local provider. It scans projects/ recursively (including subagents) under CLAUDE_CONFIG_DIR when set, otherwise ~/.claude and XDG_CONFIG_HOME/claude (default ~/.config/claude). A checkpoint keeps every assistant event for its file, because the retention window is recomputed from the current date on each fetch: a stored cutoff would freeze at the first scan and keep aged-out events forever instead of dropping them. Assistant message IDs are deduplicated across files: completed messages win over partial snapshots, then the greater output count wins. Claude input is normalized as fresh input + cache reads + cache creation; nested 5-minute/1-hour creation counts are a fallback, never added to the aggregate twice. Independent local source switches enable Codex and Claude Code (both default on under the master opt-in). Disabled sources are not scanned or included in cached reports/menu totals, and are hidden from the source selector. Disabling the selected source resets the filter to all enabled sources. Both switches may be off, in which case polling stops and the page offers the source settings. The menu bar totals enabled sources for today; enabling the menu-bar item also turns scanning on, since that item is the most natural place to discover the feature. Refreshes are queued rather than dropped: a refresh arriving while another is in flight runs after it, so rebuilding the polling cadence cannot mistake a skipped call for a completed initial refresh and then sleep out the whole interval. Stopping cancels the in-flight scan. These settings are local and not synced through WebDAV. Cache creation is shown separately but already included in the input total. Claude credentials, account data, Cowork containers and subscription limits remain outside the local scanner's scope; the quota reader has no access to session-log content.

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.
• Menu bar IP location — optional flag or localized region name after network speeds, disabled by default. It reads the same NetworkController.publicAddresses.countryCode as network details, including the selected IPv4 / IPv6 family and its fallback. It follows the existing cache and manual refresh, adds no network requests or timers, and hides when public-IP lookup is disabled or no region is available. Only the display preference is included in settings backups.
• 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.

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. Charging state comes from named pmset -g accps accessory entries. For anonymous entries, it is attached only when the reported percentage matches exactly one connected Bluetooth battery device; ambiguous matches remain unknown. Disconnected cached devices never retain a charging label.

Online updates

UpdateController posts the current version and a hashed installation ID according to the user's update-check schedule. China-region locales prefer https://x-stats.china.12306.work/api/v1/update/check; other locales prefer https://xstats-apps.12306.work/api/v1/update/check. Failures fall back serially to the other endpoint, and the first success stops further requests so one check is not reported twice. Requests use the stable XStats/<app-version> (macOS <system-version>) User-Agent format for regional routing and diagnostics. Existing installations retain the hash of their saved 32-byte random value, which remains in local UserDefaults and is excluded from WebDAV settings sync. New installations without a saved value hash the Mac serial number read through IOKit. If the serial is unavailable, they generate and save a random value with SecRandomCopyBytes. None of these paths invokes Keychain authorization, and the raw serial is never sent. Clearing preferences on an older installation can produce a new ID; historical rows are not merged. 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 with open -n. LaunchServices can retain the old instance after its PID disappears; requesting a new instance prevents the relaunch from being routed to that terminated process. 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 the dmg and zip to object storage with mc, verifies each one by re-reading it from the CDN, creates the GitHub Release that carries the dmg for manual downloads, and only then submits the generated appcast through scripts/publish_api.py to both regional services. The manifest lands last, so an installed app never sees a version whose package is not yet in place.

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.