# Phase 5: Web Push Notifications - Context

**Gathered:** 2026-06-09
**Status:** Ready for planning
**Mode:** mvp (vertical slice — see ROADMAP.md `**Mode:** mvp`)

<domain>
## Phase Boundary

Deliver Web Push so both members receive timely, reliable notifications on the
installed PWA (iOS + Android) for three triggers:

1. **Event reminders** — ~15 min before a **shared Family-calendar** event starts (NOTIF-01)
2. **Event-change alerts** — when the _other_ member adds/changes a relevant event (NOTIF-03)
3. **List-change alerts** — when the _other_ member modifies a shared list (NOTIF-02)

Plus the iOS reliability machinery (subscription health-check + visible-notification
guarantee) that keeps subscriptions alive across inactivity (success criterion 4).

**Not in this phase:** quiet-hours/DND, per-event custom reminder offsets,
per-category opt-out, notifying on the member's _own_ changes, reminders for
personal calendars (see decisions + deferred).
</domain>

<decisions>
## Implementation Decisions

### Notification copy & anti-spam

- **D-01:** **Coalesce list-change pushes per list** within a short window (~30–60s).
  A grocery burst (many rapid edits) collapses into one push, not one-per-change.
  Planner must define the debounce/window mechanism. Reorder (`position`) changes
  do **not** push at all.
- **D-02:** **Detail level differs by source.** Event notifications (reminders +
  changes) show **specifics** — title, time, action (e.g. `Lucas moved Dentist → Wed 3pm`,
  `Soccer practice starts in 15 min`). **List pings stay generic** — they name the
  actor, the list, and a change count, but **not item text** (e.g. `Wife made 3 changes
to Groceries`). Rationale: lists are the chattier, lower-stakes source; generic keeps
  the lock screen cleaner.
- **D-03:** **Name the actor** in every change notification (`Wife checked off…`,
  `Lucas added…`). Two-person household — attribution is clear and useful.
- **D-04:** **Event-change trigger granularity = meaningful changes only.** New event,
  deletion, and changes to **time/date/title/location** push. **Description-only edits
  stay silent.** Avoids noise from trivial tweaks.

### Reminder scope & timing

- **D-05:** **Reminders fire for SHARED Family-calendar events only** — _by design_,
  not as a limitation. Each member's **native device calendar app** (Apple Calendar /
  Android, syncing their Fastmail personal calendar) already fires reminders for personal
  events; FamilySync must **not duplicate** those. FamilySync owns reminders for the
  **shared Family calendar** — the cross-ecosystem coordination gap the native clients
  don't reliably cover. This narrows the literal reading of NOTIF-01 deliberately;
  verification must treat "shared-calendar events" as the reminder surface.
  - **Caveat for planner:** if a member _also_ subscribes the shared calendar in their
    native calendar app they could get duplicate reminders — that's a household setup
    choice, out of our control. Do not engineer against it.
  - **Dependency:** the shared "Family" calendar is `is_shared=1`. Per Phase 2 D-16 the
    operator must first create + share the Family calendar and mark it shared. Until then
    there are no shared events, so the reminder path has nothing to fire on (correct, not
    a bug). Planner should handle the empty-shared-calendar case gracefully.
- **D-06:** **Fixed ~15 min lead time** for v1. No per-event or custom offset. (Custom/
  per-event lead time deferred to v1.x.)
- **D-07:** **All-day events get no reminder.** They have no start time; reminders are for
  timed events only. (They remain visible in the app.)

### Onboarding & opt-out

- **D-08:** **Contextual permission prompt right after PWA install** (or first installed
  launch): a one-line explainer, then trigger `Notification.requestPermission()` /
  `pushManager.subscribe()` on a **tap gesture**. iOS hard-requires installed-PWA + a user
  gesture. Highest opt-in for the non-technical member. Hook this onto the existing install
  flow (`InstallPrompt.tsx`, Phase 3).
- **D-09:** **Single master on/off toggle** for v1 — one switch for all FamilySync
  notifications. Per-category toggles (reminders / event-changes / list-changes) are
  deferred; list-noise is already handled by coalescing (D-01), so per-category control is
  low value for two people.
- **D-10:** **Dead-subscription recovery = silent auto re-subscribe.** On app open, if the
  push subscription is missing/expired **but OS permission is still granted**, silently
  re-subscribe in the background — no user action. Only surface UI if the **OS permission
  itself** was revoked. This is the user-facing half of the mandatory iOS health-check.

### Carried forward — locked, NOT re-discussed

- **D-11:** **iOS reliability is mandatory from day one (STATE.md):** subscription
  health-check + `event.waitUntil()` in the SW + **every push must display a visible
  notification** (no silent pushes — iOS revokes after ~3). This is non-negotiable
  infrastructure, the spine of success criterion 4.
- **D-12:** **In-memory `EventEmitter` fan-out, no Redis (Phase 4).** `ioredis` is **not**
  installed; the API is a single Node process. Push dispatch hooks the **same publish
  points** as SSE — do not introduce Redis for push.
- **D-13:** **Broker is the only Fastmail I/O boundary (Phase 3 D-12).** Event-change
  detection reads from the MariaDB cache / poller / outbox — no tsdav in notification code.
- **D-14:** **react-router is installed (Phase 4 D-17)** specifically to enable push
  deep-linking. Tap targets use real URLs.

### Claude's Discretion (researcher / planner decide)

- **No quiet-hours / DND in v1** — reminders and alerts always fire immediately.
  (Deferred; revisit if it proves annoying in use.)
- **Tap-to-open deep-link targets** (obvious mapping, not separately discussed):
  reminder + event-change → open that event (calendar at its day / event popover);
  list-change → deep-link to that list (`/lists/:id`).
- **Service-worker strategy:** current setup is vite-plugin-pwa `generateSW` + `autoUpdate`;
  adding a `push` + `notificationclick` handler likely requires switching to `injectManifest`
  with a custom SW source. Planner decides and addresses Workbox-precache continuity.
- **VAPID key generation + storage**, push-subscription table schema (member-count-agnostic
  per project D-18 / Phase 4 D-18), reminder-scheduler mechanism (cron/interval scanning
  shared-calendar timed events in the MariaDB cache), and the coalescing debounce
  implementation.
- **Event-change detection source:** poller (`broker/poller.ts`, external changes) vs
  outbox-confirm (`broker/outboxWorker.ts`, this-member writes) — pick the trigger point(s)
  that fire for the _other_ member without notifying the actor (D-03 implies suppress
  self-notifications).
  </decisions>

<canonical_refs>

## Canonical References

**Downstream agents MUST read these before planning or implementing.**

### Push / iOS / VAPID constraints

- `CLAUDE.md` — "React PWA Stack" iOS push requirements table (iOS 16.4 min, Home-Screen
  install required, user-gesture subscribe, silent push unsupported → visible notification
  mandatory, no BackgroundSync) AND the `web-push` (VAPID) stack entry. **Authoritative
  constraint list for this phase.**
- `.planning/STATE.md` — Phase 5 note: iOS revokes subscriptions after ~3 silent pushes;
  health-check + `event.waitUntil()` mandatory from day one.

### Phase scope & requirements

- `.planning/ROADMAP.md` §"Phase 5: Web Push Notifications" — goal, 4 success criteria,
  NOTIF-01/02/03, MVP mode, Depends on Phase 3 + 4.
- `.planning/REQUIREMENTS.md` — NOTIF-01 (event reminder), NOTIF-02 (list-change alert),
  NOTIF-03 (event add/change alert).

### Prior locked decisions this phase builds on

- `.planning/phases/04-shared-lists-live-sync/04-CONTEXT.md` — D-04 (scoped SSE fan-out),
  D-17 (react-router for deep-linking), D-18 (member-count-agnostic schema/auth/fan-out),
  fan-out mechanism justification (in-memory emitter, no Redis).
- `.planning/phases/03-event-write-back-pwa-install/03-CONTEXT.md` — D-12 (broker is the
  only Fastmail I/O boundary), PWA install onboarding, outbox/sync architecture (D-05/D-06).
- `.planning/phases/02-calendar-display/02-CONTEXT.md` (D-16, via STATE deferred items) —
  shared "Family" calendar must be created + shared + `is_shared=1` before shared events
  (and thus reminders) exist.

### Integration code (read before implementing)

- `apps/api/src/lib/listEmitter.ts` — list-change publish points; push dispatch hooks here.
- `apps/api/src/broker/poller.ts`, `apps/api/src/broker/outboxWorker.ts` — event-change
  detection sources.
- `apps/pwa/src/components/InstallPrompt.tsx` — existing install flow to attach the
  contextual permission prompt (D-08).
- `apps/pwa/vite.config.*` — current vite-plugin-pwa `generateSW`/`autoUpdate` config (SW
  strategy decision, D-discretion).
  </canonical_refs>

<code_context>

## Existing Code Insights

### Reusable Assets

- **`apps/api/src/lib/listEmitter.ts` (`publishListEvent`)** — list-change events are already
  emitted at the right points for Phase 4 SSE. Push dispatch for NOTIF-02 hooks the same call
  sites; coalescing (D-01) wraps the dispatch.
- **`broker/poller.ts` + `broker/outboxWorker.ts`** — the existing change-detection plumbing
  (ctag-gated poll + outbox drain) is where event add/change is observed for NOTIF-03.
- **react-router (Phase 4 D-17)** — already installed; gives `/lists/:id` and event URLs for
  tap-to-open deep links (D-14).
- **`InstallPrompt.tsx`** — Phase 3 install onboarding; natural anchor for the contextual
  permission prompt (D-08).

### Established Patterns

- **Broker-only Fastmail I/O (D-13):** notification code reads the MariaDB cache, never tsdav.
- **In-memory single-process fan-out (D-12):** no Redis/ioredis; push mirrors SSE topology.
- **vite-plugin-pwa `generateSW` + `autoUpdate`:** adding `push`/`notificationclick` handlers
  likely means moving to `injectManifest` — planner must preserve Workbox precache + autoupdate.
- **Optimistic UI + scoped access checks (Phase 4 D-04/D-18):** push fan-out must be scoped to
  who can see a list/event — never broadcast to all members. Suppress self-notifications.

### Integration Points

- **New reminder scheduler:** a server-side interval/cron scanning _shared-calendar timed
  events_ in the MariaDB cache, firing ~15 min pre-start (D-05/D-06/D-07). New infra — no
  analog exists yet.
- **New push-subscription store:** member-count-agnostic table for VAPID subscriptions
  (per D-18); SW push handler; `web-push` server dispatch (`web-push` not yet installed).
- **Permission/subscription lifecycle** on the PWA: request → subscribe → persist → health-check
  → silent re-subscribe (D-08/D-10/D-11).
  </code_context>

<specifics>
## Specific Ideas

- List-change copy shape: `"{Actor} made {N} changes to {ListName}"` (generic, coalesced).
- Event copy shape: `"{Actor} {action} {EventTitle} · {when}"` (specific); reminder shape:
  `"{EventTitle} starts in 15 min"`.
- Reminder surface is the **shared Family calendar only** to avoid double-notifying against
  native device calendar reminders — this is the load-bearing rationale behind D-05.
  </specifics>

<deferred>
## Deferred Ideas

- **Quiet hours / Do-Not-Disturb** — suppress non-urgent pushes in a quiet window. v1.x.
- **Per-event / custom reminder lead time** (5/15/30/60 min, per-event field). v1.x.
- **Per-category opt-out** (independent reminder / event-change / list-change toggles). v1.x.
- **Reminders for personal-calendar events** — intentionally excluded (native clients cover
  these, D-05). Only revisit if the household stops relying on native reminders.
- **Notifying on the member's own changes** — out of scope; alerts are for the _other_ member.

### Reviewed Todos (not folded)

- **"Adopt drizzle generate+migrate workflow (retire db:push on MariaDB)"** — keyword match
  on "push" was a false positive (DB migrations, not Web Push). BUT the underlying constraint
  still applies: Phase 5 adds a push-subscription table; new tables MUST use
  `drizzle-kit generate` + `migrate`, never `db:push` (unsafe on populated MariaDB). Noted as a
  schema constraint for the planner, not folded as discussion scope.
- **"Kick off FamilySync with /gsd:new-project"** — stale kickoff todo; not relevant.
  </deferred>

---

_Phase: 05-web-push-notifications_
_Context gathered: 2026-06-09_
