SpamShield

iOS Call Directory Extension that blocks numbers you mark as spam, plus a SwiftUI host app for managing the list. Built to develop on Windows: write code locally, push, GitHub Actions builds on a macOS runner and uploads to TestFlight.

What it does

• Maintains a personal blocklist of phone numbers
• Registers them with iOS via a Call Directory Extension, so calls from those numbers are auto-blocked at the system level (same mechanism Hiya / RoboKiller use)
• Optionally labels numbers (e.g. "Tax Relief Spam") so even calls that aren't blocked get a clear caller-ID label

What it does NOT do (because iOS doesn't allow it)

• Read or delete voicemails. iOS does not expose voicemail content or storage to third-party apps.
• Delete entries from Call History. Same reason.
• Filter calls by content / transcript. CallKit blocks by phone number only.

A planned follow-up is a separate server piece that ingests carrier voicemail-to-email transcripts, runs keyword detection ("tax relief", "loan", etc.), and pushes the originating number into this app's blocklist over the network so future calls from that number get auto-blocked.

Architecture

App (SwiftUI)         ←  user adds/removes numbers, hits "Reload"
    │
    ├── BlocklistStore (App Group UserDefaults: group.com.thomashart.SpamShield)
    │
CallDirectory Extension  ← reads BlocklistStore on every reload, hands list to iOS

Two targets, one shared App Group container, one bundle prefix com.thomashart.SpamShield.

Project layout

project.yml                  XcodeGen spec — generates the .xcodeproj on CI
App/
  SpamShieldApp.swift        @main app entry
  ContentView.swift          List UI for managing numbers
  BlocklistStore.swift       Shared storage helper
  Info.plist
  SpamShield.entitlements    App Group
CallDirectory/
  CallDirectoryHandler.swift The CXCallDirectoryProvider subclass
  Info.plist
  CallDirectory.entitlements App Group
fastlane/
  Fastfile                   `beta` lane: sign, build, upload to TestFlight
  Appfile
.github/workflows/build.yml  GHA macOS runner build + TestFlight upload

CI build flow

1. Push to main
2. macOS runner installs Xcode + XcodeGen
3. xcodegen generate produces SpamShield.xcodeproj from project.yml
4. fastlane builds with auto-signing (App Store Connect API key) and uploads to TestFlight
5. TestFlight processes the build (~10-15 min)
6. Open TestFlight on iPhone, install, run

End-to-end, push-to-phone is ~25 min the first time. Repeat builds are faster.

Required GitHub secrets

Set under repo Settings → Secrets and variables → Actions:

Secret	What it is
APPLE_TEAM_ID	10-char team ID from developer.apple.com → Membership
APP_STORE_CONNECT_KEY_ID	API key ID from App Store Connect → Users and Access → Integrations → Keys
APP_STORE_CONNECT_ISSUER_ID	Issuer ID from the same screen
APP_STORE_CONNECT_API_KEY	The downloaded .p8 file, base64-encoded (base64 -w0 AuthKey_XXX.p8)

You also need to create the app record in App Store Connect once (My Apps → New → bundle id com.thomashart.SpamShield). Do that after enrollment lands.

Running locally (if you ever borrow a Mac)

brew install xcodegen
xcodegen generate
open SpamShield.xcodeproj

Then use Xcode's automatic signing with your team and run on a connected iPhone.

Deploying

Commit and push to main. Watch the Actions tab. When the build is green, install via TestFlight on the iPhone, then go to Settings → Phone → Call Blocking & Identification and toggle SpamShield on.