platform/docs/push-notifications.md

# Push notifications — design

**Status (2026-08-19):** server side **built and core**; app side **not started**. This is the second
design. It supersedes the 2026-07-31 one, which is summarised under "What changed and why" so the
reversals are legible rather than silently overwritten.

The app-side contract and build order is **`docs/push-notifications-app.md`** — hand that to whoever builds
the client. This file is the design and the reasoning.

## The shape, in one paragraph

One app on the device — the main Officer app — receives every push and is the only one that can. It is a
**hub**: the payload it gets is a **code** plus a few numbers, and the app turns that into the notification
you actually see, deep-linked to whichever app and event it concerns. The code's meaning lives in a
**mapping owned by the server** and synced to the device ahead of time, so adding a new kind of
notification is a server change and never an app build. Plugins declare their own codes the same way they
declare affordances.

## What changed and why

The first design was a **doorbell**: a category and an id, never content, with the visible text composed
server-side from the category alone. It called that "the load-bearing decision, and it is not optional".

Three things moved.

**1. Privacy relaxed, but not abandoned.** The original weighting — nothing readable may reach Apple or
Google — was reconsidered on 2026-08-19 as stricter than the owner actually wanted. What replaced it is
not "send plaintext": it is **codes**, which keeps content off Apple's and Google's servers while removing
the reason the doorbell was painful (a rigid category enum). The privacy property survives almost intact;
what was given up is the claim that it was inviolable.

**2. One receiver, not many.** The first design had each app register its own token and `appSlug` select
which app a notification went to. Now a single hub app receives everything and `appSlug` names the
**deep-link destination** instead. Same field, opposite direction — see "Migration notes".

**3. Extensibility became the priority.** The binding constraint is now "a new notification kind must not
require an app store build". That single requirement is what forces the server-owned mapping, and it is
worth more than the category purity the first design optimised for.

**What did not change:** content still does not travel. Apple and Google see a code and some integers.

## Why a hub app

- **One entitlement, one topic, one sender.** A single bundle id means one `aps-environment`, one APNs
  topic and one FCM sender, instead of credentials multiplying per app.
- **It resolves an existing contradiction.** `apps/chat` ships `withoutPushEntitlement.js`, a config plugin
  that deliberately STRIPS `aps-environment` because chat uses local notifications only. Under the first
  design that was a blocker. Under this one it is correct and stays — chat is not a push receiver, the hub
  is.
- **It concentrates the Android problem** rather than multiplying it (see "Android and GrapheneOS").

## The payload

An ordinary **alert** push — not a silent one — carrying a code and numbers:

```jsonc
{
  "aps": {
    "alert": { "title": "Officer" }, // fallback only; see "What the OS shows"
    "mutable-content": 1,
    "sound": "default",
    "thread-id": "officerdev/music",
    "badge": 3,
  },
  "officer": {
    "c": "officerdev/music:12.3", // the code — namespaced, see below
    "n": 3, // variable numbers, never content
    "id": 412, // what to fetch/open, never a human-readable string
    "mv": 47, // mapping version the server rendered against
  },
}
```

**Codes are namespaced, for the same reason affordances are.** `<publisher>/<appName>:<code>`. Plugins from
different publishers will otherwise collide on a bare integer, and a code in a log should say whose it is
without a lookup. `core` occupies the appName slot for the platform's own.

**Variable data rides beside the code, never inside it.** The mapping holds a template — `"{n} new emails"` —
and the push supplies `n`. Numbers and ids are not content, so the privacy property survives templating.

**What does NOT go in:** subject lines, senders, filenames, error strings, agent output, paths. If a value
would embarrass you in a Google log, it belongs behind `id` and gets fetched over the tailnet on tap.

## What the OS shows, and why `mutable-content` is required

A normal alert push is rendered **by the operating system, not by the app**. Send `alert.title = "12.3"`
and the user sees `12.3` on the lock screen — the app never gets a chance to touch it.

So the hub needs a **Notification Service Extension**, enabled per-push by `mutable-content: 1`. The
extension runs before display, resolves the code, and rewrites the banner.

**Crucially, the extension does a LOCAL lookup, not a network fetch.** The mapping is synced in advance by
the app into a shared App Group container; at notification time it is a dictionary read. This is what makes
the design work where a fetch-on-arrival design would not:

- no dependence on the tailnet being connected when the push lands
- no 30-second budget to overrun
- no partial failure mode on cellular with the VPN off

**This costs exactly one app build, ever — never one per notification kind.** An extension that hardcoded a
`switch` on type would need rebuilding for every new kind; this one is a generic resolver and does not.

**The alert text you send is the degraded case.** If the extension does not run — low memory, a crash, an
older OS — the user sees exactly what was in `alert`. So it is a graceful generic ("Officer"), deliberately
**not** plausible-looking decoy text: a convincing fake sentence would mislead the one person who most needs
to trust it.

**Silent pushes were considered and rejected.** `content-available: 1` with no alert would let the app
compose everything and leak least, but Apple throttles silent pushes and explicitly does not guarantee
delivery. For notifications that must arrive, that is the wrong tool.

**Android needs no extension.** An FCM **data-only message at high priority** wakes the app, which composes
the notification itself. Same codes, same mapping.

## The mapping

The server owns it; the device caches it.

```
GET /api/notify/mapping        → { version: 47, entries: { "officerdev/music:12.3": {...} } }
```

An entry says how to render and where to go:

| field    | note                                                           |
| -------- | -------------------------------------------------------------- |
| `title`  | template, `{n}`-style placeholders                             |
| `body`   | template, optional                                             |
| `target` | which app the deep link opens                                  |
| `route`  | the deep link, with `{id}` interpolated                        |
| `thread` | grouping key, so like-notifications collapse rather than stack |

**Plugins declare their own**, on the affordances pattern (`src/servers/affordances/publish.ts`): a
directory in the plugin repository, copied to a platform-managed store on install, removed on uninstall,
namespaced `<publisher>/<appName>/`. That mechanism already exists and is understood; a second one for
notifications would drift from it. The platform aggregates every installed plugin's catalogue plus its own
into the response above, and `version` increments whenever that aggregate changes.

### Staying in sync, and the fallback

Every push carries `mv`, the mapping version it was rendered against. The app compares it to its cached
version and **resyncs in the background when it is behind** — so the mapping normally catches up before an
unknown code can arrive.

When a push still outruns the sync, the fallback renders:

> **Unknown notification**
> code `officerdev/music:12.3` — tap to sync

deep-linking to `officer://resync-notification-mapping`. The code goes **in the body on purpose**: when this
fires on the owner's own phone, the first useful question is which code the server sent that the app did not
have, and without it that is debugged blind.

**The resync screen must be able to give up.** If a plugin is uninstalled its codes leave the catalogue, so
a queued notification for one will resync, still not resolve, and otherwise loop forever. That path ends
with "this came from something no longer installed", not another retry.

## What this still leaks

Apple and Google see **which code, how often, at what time, to which device**. Over months that is a
fingerprint of the owner's category vocabulary even though every code is opaque. That is much less than
plaintext and is judged acceptable — but it is not nothing, and this document does not claim otherwise.

## Where it lives

`officer-notify`, a **core** PM2 process since 2026-08-19 (built 2026-07-31; spent 2026-08-13 to 08-19
switched off after being slated for plugin extraction and never extracted). Core rather than a plugin
because the producers are the platform's own — the job queue, an agent turn ending, mail arriving — and a
notifier the owner can uninstall is one those producers cannot rely on.

```
producer (queue / email / agent / platform / plugin)
        │  POST /_officer/notify { c, userId, n?, id? }
        ▼
  officer-notify ─┬─ apns   → api.push.apple.com        (HTTP/2, ES256 JWT)
                  ├─ fcm    → fcm.googleapis.com/v1     (OAuth2 bearer)
                  └─ discord→ webhook
```

It boots with **no credentials at all** — every channel reports `isConfigured() === false` and `dispatch`
resolves empty — so an install that never sets an APNs key runs it as a no-op rather than crash-looping.
That is what makes it safe as core.

## Credentials

Env only, on the sidecar, never in the platform process and never in the database. All read
`OFFICERDEV_<NAME> ?? <NAME>`.

| var                   | what                                             |
| --------------------- | ------------------------------------------------ |
| `APNS_KEY_P8`         | contents of the `.p8` auth key (PKCS#8 EC P-256) |
| `APNS_KEY_ID`         | the key's 10-char Key ID                         |
| `APNS_TEAM_ID`        | Apple Developer Team ID                          |
| `FCM_SERVICE_ACCOUNT` | the service-account JSON                         |
| `DISCORD_WEBHOOK_URL` | existing                                         |

The `.p8` does not expire and can push to your apps forever. Treat it as spending-grade.

`APNS_ENV` appeared in the first design's table and is deliberately **not** implemented: the host is chosen
per device from the `environment` column, not per process, so one server pushes to a TestFlight build and a
release build at the same time.

## Both protocols, verified in Bun before designing around them

- **APNs**: HTTP/2 only. `node:http2` works in Bun. Auth is an ES256 JWT signed with the `.p8`, valid ≤1h,
  refreshed no more often than every 20 min or Apple rejects it. **The signature must be raw `r||s`
  (64 bytes)** — `createSign(...).sign({ key, dsaEncoding: 'ieee-p1363' })`. Node's default DER encoding is
  silently rejected.
- **FCM v1**: ordinary HTTPS. Sign an RS256 JWT with the service-account key, exchange it at
  `oauth2.googleapis.com/token` for a 1-hour access token, cache it, then POST to
  `fcm.googleapis.com/v1/projects/<id>/messages:send`.

No push library is needed for either.

## Device registry

`push_devices` — live in the schema as of 2026-08-19.

| column                                        | note                                                                                            |
| --------------------------------------------- | ----------------------------------------------------------------------------------------------- |
| `id`                                          | serial                                                                                          |
| `user_id`                                     | fk users                                                                                        |
| `token`                                       | APNs device token or FCM registration token                                                     |
| `platform`                                    | `ios` \| `android`                                                                              |
| `environment`                                 | `production` \| `sandbox` — a dev-build token fails against prod with a silent `BadDeviceToken` |
| `bundle_id`                                   | `apns-topic`                                                                                    |
| `app_slug`                                    | see migration note                                                                              |
| `last_seen_at`, `failure_count`, `created_at` | pruning                                                                                         |

Unique on `(token, bundle_id)`. Registration is idempotent: the app re-registers on every launch, since
tokens rotate.

### Migration notes from the first design

- **`appSlug` on a NOTIFICATION inverts.** It meant "deliver only to this app". It now means "the deep-link
  destination". Nothing consumes it yet, so this is a rename-in-place, not a data migration.
- **`bundle_id` / `app_slug` on a DEVICE go near-constant.** The columns exist to let several apps register
  separately; with a hub there is one bundle id per device. Keep them — a second receiver later (a watch, a
  desktop build) costs nothing this way — but "which apps has this user got" stops being a delivery question.
- **`NotifyType` is replaced by codes.** The `'job' | 'mail' | 'agent' | 'download' | 'test'` enum was the
  rigidity this design exists to remove. `test` should survive as a reserved code for first light.
- **`text.ts` moves to the device.** Server-side `renderTitle`/`renderBody` becomes the mapping. Keep a
  minimal server-side generic for the `alert` fallback.

## Failure handling

**APNs** answers inline: `410 Unregistered` or `400 BadDeviceToken` means delete the row immediately.
**FCM** likewise: `UNREGISTERED` / `INVALID_ARGUMENT` / `NOT_FOUND` means delete.

Everything else increments `failure_count`; three strikes and the row goes. Without this the registry fills
with dead tokens and delivery quietly degrades.

## Android and GrapheneOS — UNRESOLVED, and it decides Android

`apps/mobile/PUSH_NOTIFICATIONS.md` (2026-07-24) rejects FCM outright: _"requires Google Play Services; the
Pixel runs GrapheneOS without it."_ The 2026-07-31 platform design chose FCM for Android a week later and
does not mention GrapheneOS. **Nobody reconciled the two, and this design does not either.**

It matters because FCM cannot reach a device with no Play Services, so on such a phone the entire Android
path is inert regardless of anything above.

The recorded fallback is a **foreground service holding a tailnet socket**, with notifications raised
locally. It was rejected in the first design for a permanent "Officer is running" entry in the shade and
unreliability against OEM battery managers. **The hub changes that calculus**: one socket and one shade
entry for the whole platform, not one per app. The battery-manager objection is also weaker on GrapheneOS
than on Samsung or Xiaomi.

This needs an owner decision before Android work starts. iOS is unaffected and can proceed independently.

## Build order

1. ~~`push_devices` table.~~ done
2. ~~`officer-notify` sidecar, PM2 entry, `/api/notify` proxy, Discord channel.~~ done
3. ~~APNs channel + device registration endpoint.~~ done, 27 tests
4. ~~FCM channel.~~ done, 27 tests
5. **APNs credentials.** Owner action; nothing can be tested end-to-end without them.
6. **Hub app registers its token** against `POST /api/notify/_officer/devices`. Small.
7. **First light**: a `test` push rendered by the OS with plain text, no codes, no extension. Proves
   credential → APNs → device → banner as one thing, before any of the mapping exists.
8. **Codes and the mapping**: `NotifyType` → codes, `GET /api/notify/mapping`, plugin catalogues on the
   affordances pattern.
9. **The Notification Service Extension**, local lookup, App Group container.
10. **First real producer** — job finished is the obvious one.

Steps 7 and 8 are deliberately separable: the transport can be proven working before the rendering exists,
and if it is not, no amount of mapping work will help.

## Still open

- **Which events notify**, beyond the first producer. Quiet hours and batching — new mail on an 18k-mail
  account is unusable at one push per message.
- **Whether members can register devices.** The `notify` permission is `kind: 'app'`, so it is grantable per
  role and denied by default; a member with no grant cannot subscribe their own phone.
- **Android**, per above.