OpenStats/ARCHITECTURE.md

OpenStats

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.
• Helper/ — the privileged helper (OpenStatsHelper) and its launchd plist, embedded in the app bundle for SMAppService.daemon.
• Packages/OpenStatsKit/Sources/SMC — the AppleSMC user client, fan control, temperature key discovery.
• Packages/OpenStatsKit/Sources/Metrics — one sampler per metric and MetricsHub.
• Packages/OpenStatsKit/Sources/Cleaner — cleanup rules, SafetyGuard, CleanEngine.
• Packages/OpenStatsKit/Sources/HelperShared — the XPC protocol and maintenance commands shared by the app and the helper.
• Packages/OpenStatsKit/Sources/OpenStatsUI — design tokens, panel pages, settings, menu-bar renderer, app controller, snapshot renderer.
• Packages/OpenStatsKit/Tests — metrics, SMC decoding and cleanup safety.

Build

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

brew install xcodegen
make build            # Debug
make install          # Release into /Applications
make test             # swift test in the package

project.yml defaults to ad-hoc signing so the project opens anywhere. The Makefile passes the first Developer ID Application identity from the keychain (and --timestamp for Release) when there is one. make 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, and write a Homebrew cask. 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 OpenStats did not set is shown as controlled by another program.

Helper

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/OpenStats/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/OpenStats/cleanup.log as a JSON line.

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 the main window.

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 — ipinfo.io for address, region and ASN; Cloudflare trace and ipify for IPv6 and fallback. Country codes are validated before being used as flag file names.
• 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.

--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.