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Performance

History sync: gate prost decode behind secret-presence scan (#836) extract_conversation_fields previously decoded every HistorySyncMsg through prost — a 30-field struct with String allocations — to discover that most messages carry no message_secret and yield nothing useful. The CodSpeed profile showed 66% of bench_process_history_sync inside that decode path, with 56K allocations and 14.3 MB allocated per run on a 500-conversation × 40-message fixture. A shallow varint walk now runs before prost as a fast-path gate. It checks WebMessageInfo.message_secret and Message.message_context_info.message_secret; messages with no secret at any level are discarded immediately — no struct decode, no allocation. The scan mirrors prost merge semantics (repeated field occurrences count, malformed bytes degrade to the same skip a failed decode produces), and the flag logic for forwarded/poll/bot messages still runs inside prost on the subset that passes the scan. Real-world impact is larger than the bench numbers suggest. The fixture is secret-dense (2 of 3 messages carry a secret). Production InitialBootstrap blobs are secret-sparse, so the pre-scan skips proportionally more full decodes there. Benchmark (500 convos × 40 messages, 20k messages, secret-dense fixture):
MetricBeforeAfter
Allocations / run56,02039,520 (−29.5%)
Allocated bytes / run14.97 MB14.32 MB (−4.3%)
Instructions (core-pinned)2,358.7M2,301.7M (−2.4%)
Shared conversation id (#836) HistoryMsgSecretRecord.chat_id is now Arc<str>, allocated once per conversation and reference-counted into every record within that conversation. On the bench fixture: 10k clones → 500. msg_id switches to CompactString (inline up to 24 bytes for the typical 20–22 character WA message IDs), and secret switches to SecretBytes (inline up to 32 bytes, heap for larger).

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Type safety

Schema-pinned wire tags (#836) waproto now generates tags.rs at build time (alongside whatsapp.rs) from the compiled protobuf descriptor. The file exposes one pub mod per proto message with one pub const FIELD_NAME: u32 = N; per field. The history-sync wire walkers now reference these consts instead of magic numeric literals, and every #[prost(tag)] literal in the hand-written mirror structs is pinned by a compile-time assert! block. If whatsapp.proto renumbers a field the consts update automatically on next build; if a field referenced by the walkers is renamed or removed, compilation fails rather than the decoder silently reading the wrong wire data. 
use waproto::tags;

// Field number consts derived directly from whatsapp.proto
let _ = tags::web_message_info::KEY;           // 1
let _ = tags::web_message_info::MESSAGE;       // 2
let _ = tags::message::MESSAGE_CONTEXT_INFO;   // 35
let _ = tags::history_sync::CONVERSATIONS;     // 2
let _ = tags::history_sync::PUSHNAMES;         // 7

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Breaking changes

HistoryMsgSecretRecord field types (wacore) Three fields changed type. Consumers of HistoryMsgSecretRecord need the following updates: 
// chat_id: String → Arc<str>
// Borrow as &str (no move):
let chat_str: &str = &*record.chat_id;
// Clone the Arc (cheap refcount bump):
let chat_arc: Arc<str> = Arc::clone(&record.chat_id);
// Convert to owned String:
let chat_string: String = record.chat_id.to_string();

// msg_id: String → CompactString (compact_str::CompactString)
// Borrow as &str:
let id_str: &str = &*record.msg_id;
// Convert to owned String (consumes field):
let id_string: String = record.msg_id.into_string();

// secret: Vec<u8> → SecretBytes
// Borrow as &[u8]:
let key_slice: &[u8] = record.secret.as_slice();
// Convert to Vec<u8> (consumes field):
let key_vec: Vec<u8> = record.secret.into_vec();
SecretBytes stores secrets ≤32 bytes inline (no heap allocation) and falls back to Vec<u8> for larger values. It implements Deref<Target=[u8]>, From<&[u8]>, From<Vec<u8>>, PartialEq, Eq, and Debug. The INLINE_CAP: usize = 32 constant is public. waproto build process The generated src/whatsapp.rs is no longer committed to the repository. It now lives exclusively in OUT_DIR. Normal cargo build invocations are unaffected. The generate feature flag is removed. prost-build, heck, and prost-types are now unconditional [build-dependencies]. If you have --features generate in any build scripts, remove it. To regenerate after modifying whatsapp.proto, update the descriptor and rebuild: 
scripts/regenerate-proto-desc.sh   # writes waproto/src/whatsapp.desc + .sha256
cargo build -p waproto             # regenerates whatsapp.rs and tags.rs in OUT_DIR
The build verifies the descriptor’s SHA-256 against whatsapp.desc.sha256 and aborts with a clear message on mismatch.