September 20, 2026 — Groups public surface redesign

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Breaking changes

• GroupOverview — new slim, display-oriented type: id, subject, hierarchy, and participant_count. Canonical source of subject, community hierarchy, parent, and subgroup kind for high-level callers.
• GroupMetadata — unchanged full object, still the entry point for participants, roles, and settings.
• Routing snapshots — the old GroupInfo (now GroupRoutingInfo) is pub(crate). It powers the send path only; sending a message consults it for you.

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Renames

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New APIs

• Groups::fetch_overviews(&[Jid]) — batch fetch slim overviews for a chosen set of groups. Returns Found / Truncated / Forbidden / NotFound per JID. Same wire request as fetch_metadata_batch, but each <group> node is parsed with a slim parser that never materializes participants.
• Groups::resolve_participant_addresses(&mut GroupMetadata) — opt-in LID → PN backfill. fetch_metadata no longer runs this implicitly; call it at the callsite when you need PN-keyed display data. The extra cache/database cost now reads at the point of use.
• Community::list_participating — parent-community-only overview list.

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Behavior changes

• GroupMetadata.subject and GroupMetadataResponse.subject are now Option<String>. Protocol absence (None) is kept distinct from an explicit empty subject (Some("")).
• Strict batch refusal classification. Only 403 maps to Forbidden and only 404 maps to NotFound. Any other server error fails the whole batch call rather than being misreported as a missing group.
• Empty batches never send a wire-invalid zero-group request. fetch_metadata_batch(&[]) and fetch_overviews(&[]) return an empty vector directly.
• list_participating omits <participants> and <description> presence flags from its request, matching WhatsApp Web’s overview projection. It never fans out per group and never runs LID/PN backfill.

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Migration

// Before
let groups = client.groups().get_participating().await?;
for (jid, metadata) in groups {
    println!("{}: {}", jid, metadata.subject);
}

// After
let overviews = client.groups().list_participating().await?;
for overview in overviews {
    let subject = overview.subject.as_deref().unwrap_or("(no subject)");
    println!("{}: {subject}", overview.id);
}

// Before
let metadata = client.groups().get_metadata(&jid).await?;

// After — participant PN backfill is now opt-in
let mut metadata = client.groups().fetch_metadata(&jid).await?;
client.groups().resolve_participant_addresses(&mut metadata).await;

// Before
use whatsapp_rust::features::groups::BatchGroupResult;
let results = client.groups().batch_get_info(jids).await?;

// After
use whatsapp_rust::features::groups::GroupMetadataResult;
let results = client.groups().fetch_metadata_batch(&jids).await?;