fix(history-sync): serialise tcToken persistence + drop external doc reference

Addresses 4 PR #390 review findings (Codex P1 + Copilot ×3):

#1 Codex P1 (real, MAJOR) — `storeTcTokensFromHistorySync` fire-and-forget
   created a write race when multiple history-sync chunks arrived in parallel
   (common during reconnect/QR scan). The function does a non-atomic
   read-then-merge-then-write: chunk B could read `existing` before chunk A
   wrote, then commit later and overwrite chunk A's newer timestamp. Even
   worse, the merged `__index` write could drop JIDs added by the other
   chunk, leaving stale tcTokens and persistent 463 send errors.

   FIX: introduced `scheduleHistoryTcTokenSync()` — a module-scoped
   single-concurrency promise chain that sequentialises all calls in order.
   The chain swallows prior errors so a single failure can't stall future
   runs. Call site stays fire-and-forget so the `messaging-history.set`
   emit is still instant (which is the whole point of PR #389).

#2 Copilot (same root as #1) — already covered by the chain.

#3+#4 Copilot — code comments referenced
   `Downloads/InfiniteAPI-Inbound-Latency-Fix-Documentation.md` which is
   intentionally out-of-tree (user keeps it locally). Replaced the broken
   refs with self-contained explanations covering the same rationale —
   future maintainers no longer need an external file to understand the
   trade-offs.

Skipped: CodeRabbit nitpick to extract a `fireAndForgetMappingStore` helper
(stylistic, current explicit form makes the lid/pn argument order obvious to
reviewers — keeping it).

Tests: 35/35 suites, 824/824 still passing. Customizations untouched.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

WAProto/WAProto.proto

@@ -1,7 +1,7 @@
 syntax = "proto3";
 package proto;
 
-/// WhatsApp Version: 2.3000.1038024963
+/// WhatsApp Version: 2.3000.1038164556
 
 message ADVDeviceIdentity {
     optional uint32 rawId = 1;

src/Defaults/baileys-version.json

@@ -1 +1 @@
-{"version":[2,3000,1038147544]}
+{"version":[2,3000,1038167900]}

src/Socket/messages-recv.ts

@@ -2330,44 +2330,54 @@ export const makeMessagesRecvSocket = (config: SocketConfig) => {
 		)
 
 		const alt = msg.key.participantAlt || msg.key.remoteJidAlt
-		// Handle LID/PN mappings with hybrid approach:
-		// - Store mapping operation runs in background (non-critical for decrypt)
-		// - Session migration MUST complete before decrypt() to avoid "No session record" errors
-		// This addresses Codex/Copilot review concerns about race conditions with decrypt()
+		// Handle LID/PN mappings with optimized hot-path:
+		// - storeLIDPNMappings is fire-and-forget (background) — does NOT block decrypt
+		// - migrateSession is SYNC (await) — REQUIRED for decrypt to find session
+		//
+		// SAFETY: normalizeMessageJids has a fast-path that uses key.*Alt directly without
+		// hitting the store, so the just-arrived message normalizes correctly even before
+		// the background store completes. Subsequent messages in the same chat hit the
+		// store after the background write is done (ms later).
+		//
+		// Pre-check (getPNForLID/getLIDForPN) was removed — storeLIDPNMappings has internal
+		// LRU cache + dedup, the pre-check was a redundant store round-trip per inbound
+		// message that added latency under load.
+		//
+		// HISTORICAL: this restores the intent of d73cd28d39 (2026-02-03) which was
+		// partially reverted by c3fc792351 the same day due to a race-condition concern
+		// with migrateSession (kept sync here). storeLIDPNMappings was over-protected:
+		// it persists a mapping that downstream consumers can re-derive from key.*Alt,
+		// while migrateSession actually moves the Signal session record that decrypt()
+		// will load microseconds later — those two have very different criticality.
+		//
+		// DO NOT make migrateSession async — decrypt() depends on the session being at
+		// the correct identifier (LID vs PN) when it runs. Other code paths (USync
+		// device lookup in messages-send.ts) create LID/PN mappings without migrating
+		// the session, so we cannot skip migration even when the mapping already exists.
 		if (!!alt) {
 			const altServer = jidDecode(alt)?.server
 			const primaryJid = msg.key.participant || msg.key.remoteJid!
 
 			if (altServer === 'lid') {
-				// Check if mapping already exists to avoid unnecessary storage operations
-				const existingMapping = await signalRepository.lidMapping.getPNForLID(alt)
-				if (!existingMapping) {
-					// MUST await: normalizeMessageJids() runs after this and needs the mapping
-					// in the LIDMappingStore to resolve LID→PN for events delivered to consumers
-					await signalRepository.lidMapping
-						.storeLIDPNMappings([{ lid: alt, pn: primaryJid }])
-						.catch(error => logger.warn({ error, alt, primaryJid }, 'LID mapping storage failed'))
-				}
+				// Fire-and-forget: storeLIDPNMappings has internal cache+dedup,
+				// pre-check (getPNForLID) was redundant.
+				signalRepository.lidMapping
+					.storeLIDPNMappings([{ lid: alt, pn: primaryJid }])
+					.catch(error => logger.warn({ error, alt, primaryJid }, 'background LID mapping store failed'))
 
-				// CRITICAL: ALWAYS migrate session, even if mapping exists
-				// Other code paths (e.g., USync device lookup in messages-send.ts:310-319)
-				// may create mappings via storeLIDPNMappings() without calling migrateSession()
-				// This leaves sessions under PN format while decrypt() expects LID format
-				// Skipping migration based on mapping existence causes "No session record" errors
+				// CRITICAL: ALWAYS migrate session SYNC, even if mapping exists.
+				// Other code paths (e.g., USync device lookup in messages-send.ts) may create
+				// mappings via storeLIDPNMappings() without calling migrateSession(). This
+				// leaves sessions under PN format while decrypt() expects LID format.
+				// Skipping migration based on mapping existence causes "No session record" errors.
 				await signalRepository.migrateSession(primaryJid, alt)
 			} else {
-				// Check if reverse mapping exists
-				const existingMapping = await signalRepository.lidMapping.getLIDForPN(alt)
-				if (!existingMapping) {
-					// MUST await: normalizeMessageJids() runs after this and needs the mapping
-					// in the LIDMappingStore to resolve LID→PN for events delivered to consumers
-					await signalRepository.lidMapping
-						.storeLIDPNMappings([{ lid: primaryJid, pn: alt }])
-						.catch(error => logger.warn({ error, alt, primaryJid }, 'LID mapping storage failed'))
-				}
+				// Fire-and-forget: same rationale as above.
+				signalRepository.lidMapping
+					.storeLIDPNMappings([{ lid: primaryJid, pn: alt }])
+					.catch(error => logger.warn({ error, alt, primaryJid }, 'background LID mapping store failed'))
 
-				// CRITICAL: ALWAYS migrate session, even if mapping exists
-				// Same reasoning as above - mapping existence doesn't guarantee session migration
+				// CRITICAL: ALWAYS migrate session SYNC.
 				await signalRepository.migrateSession(alt, primaryJid)
 			}
 		}

src/Utils/process-message.ts

@@ -40,7 +40,7 @@ import { getKeyAuthor, toNumber } from './generics'
 import { downloadAndProcessHistorySyncNotification } from './history'
 import type { ILogger } from './logger'
 import { metrics, recordHistorySyncMessages } from './prometheus-metrics.js'
-import { buildMergedTcTokenIndexWrite, resolveTcTokenJid } from './tc-token-utils'
+import { buildMergedTcTokenIndexWrite } from './tc-token-utils'
 
 type ProcessMessageContext = {
 	shouldProcessHistoryMsg: boolean
@@ -82,32 +82,106 @@ const REAL_MSG_REQ_ME_STUB_TYPES = new Set([WAMessageStubType.GROUP_PARTICIPANT_
  * (TC_TOKEN_INDEX_KEY) via buildMergedTcTokenIndexWrite, so the 24h prune sweep in
  * messages-recv picks them up across sessions.
  */
+/**
+ * Single-concurrency queue for `storeTcTokensFromHistorySync` calls.
+ *
+ * Why: the function does read-then-write merges (`keyStore.get('tctoken', ...)` →
+ * compute → `keyStore.set(...)`) which are NOT atomic at the store level. If two
+ * history-sync chunks invoke this concurrently (common during reconnect / QR
+ * scan), an older chunk that started first can `keyStore.set` AFTER a newer
+ * chunk, overwriting the newer entry — and worse, the merged `__index` write
+ * can drop JIDs the other chunk just added. Result: stale tcTokens / repeat 463
+ * sends until the next opportunistic refetch.
+ *
+ * Serialising via a chained Promise keeps the runs ordered while still freeing
+ * the calling `processMessage` to emit `messaging-history.set` immediately
+ * (the chain is fire-and-forget at the call site). Errors don't break the chain
+ * — each `catch` resets it to `Promise.resolve()` so a single failure can't
+ * stall future runs.
+ *
+ * The chain is module-scoped (one per Node process). Multiple Baileys instances
+ * sharing this module will serialise across instances too, but their writes
+ * target different keyStores so there's no correctness gain — only a tiny loss
+ * of inter-instance parallelism for tcToken syncs, which is acceptable given
+ * how rarely this runs vs. how rare cross-instance contention is.
+ */
+let historyTcTokenChain: Promise<void> = Promise.resolve()
+
+function scheduleHistoryTcTokenSync(
+	chats: Chat[],
+	signalRepository: SignalRepositoryWithLIDStore,
+	keyStore: SignalKeyStoreWithTransaction,
+	logger?: ILogger
+): void {
+	historyTcTokenChain = historyTcTokenChain
+		.catch(() => {
+			/* swallow prior error so chain stays alive */
+		})
+		.then(() => storeTcTokensFromHistorySync(chats, signalRepository, keyStore, logger))
+		.catch(err => {
+			logger?.warn({ err }, 'background tctoken history-sync persistence failed')
+		})
+}
+
 async function storeTcTokensFromHistorySync(
 	chats: Chat[],
 	signalRepository: SignalRepositoryWithLIDStore,
 	keyStore: SignalKeyStoreWithTransaction,
 	logger?: ILogger
 ) {
-	const getLIDForPN = signalRepository.lidMapping.getLIDForPN.bind(signalRepository.lidMapping)
-
-	const candidates: { storageJid: string; token: Buffer; ts: number; senderTs?: number }[] = []
-	for (const chat of chats) {
+	// Cheap filter first — most chats in a sync chunk don't carry tcToken at all,
+	// and we want to avoid spinning up promises for them.
+	const tokenChats = chats.filter(chat => {
 		const ts = chat.tcTokenTimestamp ? toNumber(chat.tcTokenTimestamp) : 0
-		if (chat.tcToken?.length && ts > 0) {
-			const jid = jidNormalizedUser(chat.id!)
-			const storageJid = await resolveTcTokenJid(jid, getLIDForPN)
-			candidates.push({
-				storageJid,
-				token: Buffer.from(chat.tcToken),
-				ts,
-				senderTs: chat.tcTokenSenderTimestamp ? toNumber(chat.tcTokenSenderTimestamp) : undefined
-			})
+		return !!chat.tcToken?.length && ts > 0
+	})
+
+	if (!tokenChats.length) {
+		return
+	}
+
+	// Pre-normalize so the rest of the pipeline is a synchronous join.
+	const normalized = tokenChats.map(chat => ({
+		chat,
+		ts: toNumber(chat.tcTokenTimestamp!),
+		jid: jidNormalizedUser(chat.id!)
+	}))
+
+	// BATCHED LID resolution. The previous shape called getLIDForPN once per
+	// chat (sequential await inside a for-of), which became the bottleneck
+	// during heavy history sync — every cold-cache hit was a DB round-trip,
+	// stalling messaging-history.set and spilling into the event-buffer.
+	// `getLIDsForPNs` resolves a deduped list in ONE batched query (and shares
+	// USync retry across PNs that miss cache), turning O(N) round-trips into 1.
+	//
+	// LID inputs (and `@hosted.lid`) skip the lookup entirely — they're already
+	// the storage form. Failures degrade gracefully: a missing mapping just
+	// stores under the original jid, matching `resolveTcTokenJid`'s null branch.
+	const pnsToResolve = [...new Set(normalized.filter(({ jid }) => !isLidUser(jid)).map(({ jid }) => jid))]
+	const pnToLid = new Map<string, string>()
+
+	if (pnsToResolve.length) {
+		try {
+			const mappings = await signalRepository.lidMapping.getLIDsForPNs(pnsToResolve)
+			// Flat loop (continue-on-skip) keeps max nesting depth at 4 for lint.
+			for (const { pn, lid } of mappings ?? []) {
+				if (!pn || !lid) continue
+				pnToLid.set(jidNormalizedUser(pn), lid)
+			}
+		} catch (err) {
+			// Per-chat fallback below (storageJid := jid). Don't abort the chunk —
+			// CodeRabbit noted that all-or-nothing rejection here would drop every
+			// tctoken in the batch AND prevent messaging-history.set from firing.
+			logger?.warn({ err }, 'storeTcTokensFromHistorySync: getLIDsForPNs batch failed; falling back to per-chat jid')
 		}
 	}
 
-	if (!candidates.length) {
-		return
-	}
+	const candidates = normalized.map(({ chat, ts, jid }) => ({
+		storageJid: pnToLid.get(jid) ?? jid,
+		token: Buffer.from(chat.tcToken!),
+		ts,
+		senderTs: chat.tcTokenSenderTimestamp ? toNumber(chat.tcTokenSenderTimestamp) : undefined
+	}))
 
 	const jids = candidates.map(c => c.storageJid)
 	const existing = await keyStore.get('tctoken', jids)
@@ -532,11 +606,28 @@ const processMessage = async (
 						}
 					}
 
-					// Persist tctokens carried by history-sync chats BEFORE emitting messaging-history.set
-					// — listeners may immediately fire outbound sends that need the tctoken, and the store
-					// has to be populated first to avoid an error 463 on the first multi-device send.
-					// Runs AFTER storeLIDPNMappings (see comment above) so LID resolution works.
-					await storeTcTokensFromHistorySync(data.chats, signalRepository, keyStore, logger)
+					// Persist tctokens carried by history-sync chats in BACKGROUND, serialised.
+					//
+					// Originally awaited (PR #386) to avoid 463 on first multi-device send, but in
+					// production this drained the event buffer per-chunk and added visible delivery
+					// latency (especially after restart / QR scan when many chunks arrived at once).
+					//
+					// `scheduleHistoryTcTokenSync` enqueues onto a single-concurrency promise chain
+					// (see definition above) — chunks persist sequentially in the order they were
+					// emitted, preserving timestamp monotonicity AND keeping the `__index` write
+					// safe from concurrent merge clobbers. The call returns immediately so the
+					// `messaging-history.set` emit is not blocked.
+					//
+					// TRADE-OFF: a listener that fires an outbound send IMMEDIATELY after the emit
+					// may race the still-pending persistence and get a 463 on that specific send.
+					// The existing 463 handler in messages-recv.ts triggers a getPrivacyTokens()
+					// refetch that auto-recovers within seconds. Net result is much better UX than
+					// per-chunk stalls.
+					//
+					// DO NOT add `await` back here without re-evaluating production latency, AND
+					// DO NOT call storeTcTokensFromHistorySync directly — it must go through the
+					// chain to preserve write ordering across overlapping chunks.
+					scheduleHistoryTcTokenSync(data.chats, signalRepository, keyStore, logger)
 
 					ev.emit('messaging-history.set', {
 						...data,