Like items should collapse into one summary

What it is

When many like items arrive, the shade should show one summary, not a card per person, like, or parcel scan. "Like" means the same thread, the same event type on the same object, or repeated state in a short window that one intent can handle. The summary's job is to cut card count so one glance covers a set of changes.

This is presentation-layer collapse of items that have already arrived. It is not holding pushes to emit at one clock time, and not the post-focus list of what was held.

Why it happens

The shade has little scan capacity. Each card spends a title row; duplicates push genuinely different events out of the viewport. People already handle repeats as a set—"this thread has new mail"—not as third-then-fourth. Flat cards force that set operation onto the reader. Bundling does the operation in the system; the person sees pre-grouped objects.

The merge key must be stable. Sliding windows like "just now" will either bind unrelated sources or split one thread into two piles. Typical keys are thread id, or object id plus event type. Hard-merging across types (payment failure bundled with a like as "3 updates") destroys the next action, because the set has no single intent.

Studying it

Give the same arrival set as one-card-each versus thread summaries. After a timed glance, ask how many objects need handling and which is most urgent.

Independent variables: merge key (thread / app / time window), whether the summary reveals the latest body, cap on visible cards. Dependent variables: object-identification accuracy, missed high-consequence items, gestures to clear all, scan time.

Labs with few items and ample time understate bundling. Fill the shade until scrolling is required. "Looks cleaner" is not the endpoint—clean but nameless is a failed merge.

Where it stops holding

Alerts that each need their own decision (failures on different devices, cancellations of different orders) must not become "3 anomalies," or people will handle them as one. Transient collaboration cues ("is typing") should not join a durable summary. A single item forced into "1 new message" is worse than showing the body. If assistive tech reads only the count and not the members, bundling hides detail; expansion must be traversable.

Applying it

• Merge on thread or object-plus-type; do not merge across apps or types.
• Put object and count in the title, and show one recognizable latest body by default, not a number alone.
• New arrivals should join an existing card rather than inserting another of the same kind at the top.
• Verify by pushing ten to one thread and one high-consequence item to another object in five minutes. A person scanning the shade should report "one thread updating, plus a separate item," not eleven flats. If the separate object is lost, the merge key is wrong.

Related

• Within the group: H5.04.2 Bundles must still show how items differ · H5.04.3 Handled items must leave the bundle
• Adjacent: H5.10 Push frequency and quiet hours · H5.05 Badges and unread counts · H5.11 Notification history and replay
• Search terms: notification bundling · notification grouping · summary shade