Auth & local state

The Asomium MCP server is stateless across runs — every credential is read fresh from your macOS Keychain, and the small amount of state the server does keep (tracking, snapshots, counters) lives in plain JSON files under ~/Library/Application Support/ReleaseKit/.

Credentials flow

When the MCP server starts up, it does two things:

1. Reads the handoff file at ~/Library/Application Support/ReleaseKit/com.mariopek.releasekit/mcp-handoff.json to learn which workspace it should authenticate as. The Mac app writes this file the first time you enable MCP access in Settings → AI Integration.
2. Reads the ASC API key from the per-workspace Keychain entry pointed to by the handoff. Both the GUI and the MCP process share the same Keychain entry — they run as the same user, so plain POSIX file permissions are enough; no entitlement gymnastics required.

For one-off CLI invocations (testing locally, scripted runs without the Mac app open), env vars override the handoff path:

• ASOMIUM_ASC_KEY_ID
• ASOMIUM_ASC_ISSUER_ID
• ASOMIUM_ASC_KEY_PEM (inline) or ASOMIUM_ASC_KEY_PEM_PATH (file path)

Anthropic credentials

How translation reaches Claude depends on your subscription tier:

• BYO — the MCP server reads your Anthropic key from the same Keychain entry the Mac app uses (or ASOMIUM_ANTHROPIC_API_KEY env var). Your Anthropic account is billed for each translate_field call.
• Pro Monthly / Annual — translations route through Asomium’s managed AI account. You don’t supply an Anthropic key; the MCP server uses team credentials and decrements your monthly token bucket. A future quota handoff file lets the Mac app pass the remaining token count to MCP for client-side enforcement.

Nothing goes anywhere else

• The AI client (Claude, Cursor, etc.) never sees your ASC .p8 key — only the structured JSON results of MCP tool calls.
• The MCP process never writes credentials to disk; it reads them fresh from Keychain each session.
• Network traffic from the MCP server hits exactly three destinations: Apple (App Store Connect API + iTunes Search), Anthropic (translate_field only), and — for Pro tiers — RevenueCat for subscription state. Nothing else.

MCP-owned on-disk state

The server keeps these files under ~/Library/Application Support/ReleaseKit/com.mariopek.releasekit/:

File	What it stores	Written by
mcp-handoff.json	Active workspace identifier	Mac app
mcp-build-configs.json	Per-app Xcode project / scheme / platform for build_and_ship	Mac app (mirrored from BuildConfigStore)
keyword-tracking.json	Tracked keywords + rank-snapshot history	MCP (track_keyword, refresh_tracked_ranks)
snapshots/<bundleId>/*.json	Saved metadata snapshots for diff_metadata	MCP (snapshot_metadata)
usage-counter.json	Current-month translate-call counter	MCP (translate_field increments)

All files use 0600 POSIX permissions — readable only by your user account. The Mac app and MCP server both run as you, so no shared group or App Group is needed.

Concurrency

The MCP server doesn’t lock the Keychain or these JSON files — Mac OS serialises access at the filesystem layer, and the JSON writes are atomic (Data.write(options: [.atomic])). The Mac app polls ASC every 30 seconds, so any change made through MCP appears in the GUI on the next poll without manual refresh.

Multiple machines

Each machine has its own Asomium install with its own Keychain entries and its own local JSON files. Subscription state syncs cross-device via your Apple ID (Apple StoreKit + RevenueCat), but per-machine state — tracked keywords, saved snapshots, build configs — stays local. If you want any of that to sync, file an issue.

Disconnecting

To revoke MCP access without uninstalling:

1. Open Asomium → Settings → AI Integration.
2. Click Disconnect — the handoff file is deleted; MCP can no longer authenticate as your workspace.
3. Reconnect at any time to re-enable.