One app, four clients

3 September 2026. Don: "make sure the UI and look of icons is identical between the apps … this should be as 100% consistent as the OS will allow and will hold for the MacOS and Windows clients as well … We want to leverage people's familiarity with other messaging apps and particularly with WA such that there will be almost no learning curve … the behind the scenes work is where most of the difference will live."

This is the reference the iOS, Android and future desktop clients all build against. It exists because the drift was already real after two clients; with four it would be unfixable.

The rule

Where WhatsApp has solved a layout, copy the solution. Not the branding, not the colours — the shape: what lives in which tab, what a long-press offers, where the archive sits, what tapping a name does. Every hour a user spends learning our navigation is an hour spent on something that is not the reason to use this app.

Where we differ, differ for a reason and only in the places the reason applies. Pairing has no WhatsApp equivalent because WhatsApp has phone numbers and we do not. That justifies a different setup flow. It does not justify a different contact list.

Platform idiom wins over cross-platform sameness where they collide. A back gesture, a navigation bar, a share sheet — use what the OS gives, because a user's familiarity with their phone outranks their familiarity with our other client. Everything above that layer matches.

Structure

Three top-level destinations, in this order, on every client.

Chats and Contacts are separate lists of different things and must stay so: a conversation is a thread, a contact is a person, and a person with no thread still exists.

Tapping a name opens their profile

From either list, and from the conversation header. One screen, the same on every client, in this order:

1. Name, editable in place. We own this string — there is no address book behind it — so renaming is ours to offer and must exist on every client.
2. Pairing state, and the verification code when there is one.
3. Message, which opens or creates the thread.
4. Mute, and notification sound for this conversation.
5. Block, Report, Delete.

Deliberately not here yet, and each is a Tier 2/3 item rather than an omission: shared media, disappearing-message timer, and a per-contact calling handoff.

The icon vocabulary

One meaning, one icon, everywhere. The two platforms name them differently; the shape must read the same.

Adding a row here is the cheap moment. Adding an icon to one client without adding it here is how the next divergence starts, and the drift this document was written to fix took two clients and about a week to appear.

Known divergences, to be closed

Found auditing on 3 Sep 2026:

• Rename existed on Android and not iOS. Closed.
• Pairing was one button on iOS and three on Android (Show my code / Scan their code / Enter a code). One entry point, then the choice inside — the shorter list is the better one.
• The add-contact icon differed, which is what Don noticed first.

What does not have to match

The parts a user never sees, and the parts where honesty beats symmetry:

• Transport, storage and crypto — all of it, which is where the real work is.
• Anything one platform genuinely cannot do. iOS has no system notification-sound picker, so it ships bundled sounds where Android offers every sound on the phone. Faking parity by hiding Android's picker would make both worse.

Big screens: iPad, macOS, Windows, Android tablets (J100)

Same shape and same words on every platform, never the same pixels.

Panes. Three when the window is wide (rail · list · thread), two when medium, one when phone-width. Width decides, not device, so a resized window behaves like a smaller device.

Thread header. Picture, name, status letters beneath the name, call and video at the right. Back appears only in one-pane mode.

Menu bar (macOS, iPadOS 26+, Windows -- and nothing may live only here):

Input. Pointer hover states, arrow keys through the list, Return to send wherever a keyboard exists.

A new platform implements this section. It does not copy screenshots of the others.

English is the reference text; any translation is a convenience. Help is stored on this phone and never contacts anyone.