fix(waproto): normalize high to int32 + tighten roundtrip test

Addresses 2 review comments on PR #385:

1. CodeRabbit Major — longToString/longToNumber checked
   `value.high < 0` on the raw input. When a Long-like object carries
   high as an unsigned 32-bit value (e.g. raw {low, high} from JSON
   deserialization, not constructed via Long.fromBits/fromValue which
   normalize via `| 0`), the sign-bit detection fails and the value is
   interpreted as unsigned. Example: {low: 0, high: 0xFFFFFFFF} signed
   should be -4294967296 but returned 18446744069414584320.

   Fix: `const high = value.high | 0` before the sign check. Applied
   to both helpers in WAProto/index.js (generated artifact) and
   WAProto/fix-imports.js (template). Diverges from upstream Baileys
   PR #2333 which has the same latent bug.

   Added 2 test cases in bigint-validation.test.ts for the raw
   {low, high} scenario (Long.fromBits would mask the bug because it
   normalizes internally).

2. CodeRabbit Nitpick — the encode/decode roundtrip test in
   proto-tojson-long.test.ts used safe integers (1700000000 and
   123456789), which would silently pass even if longToString fell
   back to Number(value). Switched to uint64 values above
   MAX_SAFE_INTEGER (max uint64 and 9999999999999999999) so the
   roundtrip actually exercises the BigInt fast path.

Test suite: 789/789 passing (+2 cases for the unsigned-high scenario).

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

WAProto/fix-imports.js

@@ -18,14 +18,21 @@ try {
     '\tif (typeof value === "number") {\n' +
     '\t\treturn String(value);\n' +
     '\t}\n' +
-    '\tif (!$util.Long) {\n' +
-    '\t\treturn String(value);\n' +
+    '\t// Fast path: convert Long {low, high} directly via native BigInt\n' +
+    '\t// BigInt.toString() is a native C++ operation, much faster than Long\'s pure JS division loops\n' +
+    '\tif (value && typeof value.low === "number" && typeof value.high === "number") {\n' +
+    '\t\t// Normalize high to signed int32 so the sign-bit check works for inputs\n' +
+    '\t\t// where high is stored unsigned (e.g. raw {low, high} JSON).\n' +
+    '\t\tconst high = value.high | 0;\n' +
+    '\t\tconst lo = BigInt(value.low >>> 0);\n' +
+    '\t\tconst hi = BigInt(value.high >>> 0);\n' +
+    '\t\tconst combined = (hi << 32n) | lo;\n' +
+    '\t\tif (!unsigned && high < 0) {\n' +
+    '\t\t\treturn (combined - (1n << 64n)).toString();\n' +
+    '\t\t}\n' +
+    '\t\treturn combined.toString();\n' +
     '\t}\n' +
-    '\tconst normalized = $util.Long.fromValue(value);\n' +
-    '\tconst prepared = unsigned && normalized && typeof normalized.toUnsigned === "function"\n' +
-    '\t\t? normalized.toUnsigned()\n' +
-    '\t\t: normalized;\n' +
-    '\treturn prepared.toString();\n' +
+    '\treturn String(value);\n' +
     '}\n\n'
   const longToNumberHelper =
     'function longToNumber(value, unsigned) {\n' +
@@ -33,19 +40,20 @@ try {
     '\t\treturn value;\n' +
     '\t}\n' +
     '\tif (typeof value === "string") {\n' +
-    '\t\tconst numeric = Number(value);\n' +
-    '\t\treturn numeric;\n' +
-    '\t}\n' +
-    '\tif (!$util.Long) {\n' +
     '\t\treturn Number(value);\n' +
     '\t}\n' +
-    '\tconst normalized = $util.Long.fromValue(value);\n' +
-    '\tconst prepared = unsigned && normalized && typeof normalized.toUnsigned === "function"\n' +
-    '\t\t? normalized.toUnsigned()\n' +
-    '\t\t: typeof normalized.toSigned === "function"\n' +
-    '\t\t\t? normalized.toSigned()\n' +
-    '\t\t\t: normalized;\n' +
-    '\treturn prepared.toNumber();\n' +
+    '\t// Fast path: convert Long {low, high} directly via native BigInt\n' +
+    '\tif (value && typeof value.low === "number" && typeof value.high === "number") {\n' +
+    '\t\tconst high = value.high | 0;\n' +
+    '\t\tconst lo = BigInt(value.low >>> 0);\n' +
+    '\t\tconst hi = BigInt(value.high >>> 0);\n' +
+    '\t\tconst combined = (hi << 32n) | lo;\n' +
+    '\t\tif (!unsigned && high < 0) {\n' +
+    '\t\t\treturn Number(combined - (1n << 64n));\n' +
+    '\t\t}\n' +
+    '\t\treturn Number(combined);\n' +
+    '\t}\n' +
+    '\treturn Number(value);\n' +
     '}\n\n'
 
   if (!content.includes('function longToString(')) {

WAProto/index.js

@@ -12,14 +12,21 @@ function longToString(value, unsigned) {
 	if (typeof value === "number") {
 		return String(value);
 	}
-	if (!$util.Long) {
-		return String(value);
+	// Fast path: convert Long {low, high} directly via native BigInt
+	// BigInt.toString() is a native C++ operation, much faster than Long's pure JS division loops
+	if (value && typeof value.low === "number" && typeof value.high === "number") {
+		// Normalize high to signed int32 so the sign-bit check works for inputs
+		// where high is stored unsigned (e.g. raw {low, high} JSON).
+		const high = value.high | 0;
+		const lo = BigInt(value.low >>> 0);
+		const hi = BigInt(value.high >>> 0);
+		const combined = (hi << 32n) | lo;
+		if (!unsigned && high < 0) {
+			return (combined - (1n << 64n)).toString();
+		}
+		return combined.toString();
 	}
-	const normalized = $util.Long.fromValue(value);
-	const prepared = unsigned && normalized && typeof normalized.toUnsigned === "function"
-		? normalized.toUnsigned()
-		: normalized;
-	return prepared.toString();
+	return String(value);
 }
 
 function longToNumber(value, unsigned) {
@@ -27,19 +34,20 @@ function longToNumber(value, unsigned) {
 		return value;
 	}
 	if (typeof value === "string") {
-		const numeric = Number(value);
-		return numeric;
-	}
-	if (!$util.Long) {
 		return Number(value);
 	}
-	const normalized = $util.Long.fromValue(value);
-	const prepared = unsigned && normalized && typeof normalized.toUnsigned === "function"
-		? normalized.toUnsigned()
-		: typeof normalized.toSigned === "function"
-			? normalized.toSigned()
-			: normalized;
-	return prepared.toNumber();
+	// Fast path: convert Long {low, high} directly via native BigInt
+	if (value && typeof value.low === "number" && typeof value.high === "number") {
+		const high = value.high | 0;
+		const lo = BigInt(value.low >>> 0);
+		const hi = BigInt(value.high >>> 0);
+		const combined = (hi << 32n) | lo;
+		if (!unsigned && high < 0) {
+			return Number(combined - (1n << 64n));
+		}
+		return Number(combined);
+	}
+	return Number(value);
 }
 
 export const proto = $root.proto = (() => {

src/Utils/history.ts

@@ -1,5 +1,6 @@
+import { pipeline } from 'stream/promises'
 import { promisify } from 'util'
-import { inflate } from 'zlib'
+import { createInflate, inflate } from 'zlib'
 import { proto } from '../../WAProto/index.js'
 import type { Chat, Contact, LIDMapping, WAMessage } from '../Types'
 import { WAMessageStubType } from '../Types'
@@ -29,16 +30,15 @@ const inflatePromise = promisify(inflate)
  */
 export const downloadHistory = async (msg: proto.Message.IHistorySyncNotification, options: RequestInit) => {
 	const stream = await downloadContentFromMessage(msg, 'md-msg-hist', { options })
-	const bufferArray: Buffer[] = []
-	for await (const chunk of stream) {
-		bufferArray.push(chunk)
-	}
-
-	let buffer: Buffer = Buffer.concat(bufferArray)
-
-	// decompress buffer
-	buffer = await inflatePromise(buffer)
+	// Pipe decrypted stream directly through zlib inflate.
+	// Avoids allocating an intermediate buffer for the compressed payload —
+	// memory peaks during 50MB history syncs drop ~50% (PR upstream #2333).
+	const inflater = createInflate()
+	const chunks: Buffer[] = []
+	inflater.on('data', (chunk: Buffer) => chunks.push(chunk))
+	await pipeline(stream, inflater)
 
+	const buffer = Buffer.concat(chunks)
 	const syncData = proto.HistorySync.decode(buffer)
 	return syncData
 }
@@ -361,7 +361,7 @@ export const processHistoryMessage = (item: proto.IHistorySync, logger?: ILogger
 					}
 				}
 
-				chats.push({ ...chat })
+				chats.push(chat)
 			}
 
 			break

src/Utils/messages-media.ts

@@ -618,7 +618,7 @@ export const downloadEncryptedContent = async (
 
 	const output = new Transform({
 		transform(chunk, _, callback) {
-			let data = Buffer.concat([remainingBytes, chunk])
+			let data = remainingBytes.length ? Buffer.concat([remainingBytes, chunk]) : chunk
 
 			const decryptLength = toSmallestChunkSize(data.length)
 			remainingBytes = data.slice(decryptLength)

src/__tests__/bigint-validation.test.ts

@@ -0,0 +1,209 @@
+import Long from 'long'
+import $protobuf from 'protobufjs/minimal.js'
+
+const $util = $protobuf.util
+
+// proto implementation
+function longToStringOld(value: any, unsigned?: boolean): string {
+	if (typeof value === 'string') return value
+	if (typeof value === 'number') return String(value)
+	if (!$util.Long) return String(value)
+	const normalized = ($util.Long as any).fromValue(value)
+	const prepared =
+		unsigned && normalized && typeof normalized.toUnsigned === 'function' ? normalized.toUnsigned() : normalized
+	return prepared.toString()
+}
+
+// bigint implementation
+function longToStringNew(value: any, unsigned?: boolean): string {
+	if (typeof value === 'string') return value
+	if (typeof value === 'number') return String(value)
+	if (value && typeof value.low === 'number' && typeof value.high === 'number') {
+		const high = value.high | 0
+		const lo = BigInt(value.low >>> 0)
+		const hi = BigInt(value.high >>> 0)
+		const combined = (hi << 32n) | lo
+		if (!unsigned && high < 0) {
+			return (combined - (1n << 64n)).toString()
+		}
+
+		return combined.toString()
+	}
+
+	return String(value)
+}
+
+function longToNumberOld(value: any, unsigned?: boolean): number {
+	if (typeof value === 'number') return value
+	if (typeof value === 'string') return Number(value)
+	if (!$util.Long) return Number(value)
+	const normalized = ($util.Long as any).fromValue(value)
+	const prepared =
+		unsigned && normalized && typeof normalized.toUnsigned === 'function'
+			? normalized.toUnsigned()
+			: typeof normalized.toSigned === 'function'
+				? normalized.toSigned()
+				: normalized
+	return prepared.toNumber()
+}
+
+function longToNumberNew(value: any, unsigned?: boolean): number {
+	if (typeof value === 'number') return value
+	if (typeof value === 'string') return Number(value)
+	if (value && typeof value.low === 'number' && typeof value.high === 'number') {
+		const high = value.high | 0
+		const lo = BigInt(value.low >>> 0)
+		const hi = BigInt(value.high >>> 0)
+		const combined = (hi << 32n) | lo
+		if (!unsigned && high < 0) {
+			return Number(combined - (1n << 64n))
+		}
+
+		return Number(combined)
+	}
+
+	return Number(value)
+}
+
+describe('BigInt vs Long equivalence validation', () => {
+	// Test cases: [description, Long value, unsigned flag]
+	const testCases: [string, Long, boolean][] = [
+		// Basic values
+		['zero unsigned', Long.fromNumber(0, true), true],
+		['zero signed', Long.fromNumber(0, false), false],
+		['one unsigned', Long.fromNumber(1, true), true],
+		['one signed', Long.fromNumber(1, false), false],
+
+		// Typical WhatsApp timestamps (seconds since epoch)
+		['timestamp 2023', Long.fromNumber(1700000000, true), true],
+		['timestamp 2025', Long.fromNumber(1750000000, true), true],
+		['timestamp as signed', Long.fromNumber(1700000000, false), false],
+
+		// File sizes
+		['small file', Long.fromNumber(1024, true), true],
+		['medium file 10MB', Long.fromNumber(10485760, true), true],
+		['large file 2GB', Long.fromNumber(2147483648, true), true],
+
+		// Boundary values - 32-bit
+		['max int32', Long.fromNumber(2147483647, false), false],
+		['min int32', Long.fromNumber(-2147483648, false), false],
+		['max uint32', Long.fromNumber(4294967295, true), true],
+
+		// Around MAX_SAFE_INTEGER
+		['MAX_SAFE_INTEGER', Long.fromString('9007199254740991', false), false],
+		['MAX_SAFE_INTEGER + 1', Long.fromString('9007199254740992', false), false],
+		['MAX_SAFE_INTEGER unsigned', Long.fromString('9007199254740991', true), true],
+
+		// Large unsigned values
+		['large unsigned', Long.fromString('9999999999999999999', true), true],
+		['max uint64', Long.fromString('18446744073709551615', true), true],
+		['max uint64 - 1', Long.fromString('18446744073709551614', true), true],
+
+		// Signed negative values
+		['negative one', Long.fromNumber(-1, false), false],
+		['negative small', Long.fromNumber(-100, false), false],
+		['negative large', Long.fromNumber(-2147483648, false), false],
+		['min int64', Long.fromString('-9223372036854775808', false), false],
+		['max int64', Long.fromString('9223372036854775807', false), false],
+		['-1 as signed Long', Long.fromBits(-1, -1, false), false],
+
+		// Tricky bit patterns
+		['high=1, low=0', Long.fromBits(0, 1, true), true],
+		['high=0, low=-1 (0xFFFFFFFF)', Long.fromBits(-1, 0, true), true],
+		['high=-1, low=-1 unsigned (max uint64)', Long.fromBits(-1, -1, true), true],
+		['high=0x7FFFFFFF, low=0xFFFFFFFF (max int64)', Long.fromBits(-1, 0x7fffffff, false), false],
+		['high=0x80000000, low=0 (min int64)', Long.fromBits(0, -2147483648, false), false],
+
+		// Powers of 2
+		['2^32', Long.fromString('4294967296', true), true],
+		['2^32 signed', Long.fromString('4294967296', false), false],
+		['2^48', Long.fromString('281474976710656', true), true],
+		['2^63', Long.fromString('9223372036854775808', true), true]
+	]
+
+	describe('longToString equivalence', () => {
+		for (const [desc, longVal, unsigned] of testCases) {
+			it(`${desc}: Long(${longVal.low}, ${longVal.high}, ${unsigned})`, () => {
+				const oldResult = longToStringOld(longVal, unsigned)
+				const newResult = longToStringNew(longVal, unsigned)
+				expect(newResult).toBe(oldResult)
+			})
+		}
+	})
+
+	describe('longToNumber equivalence', () => {
+		for (const [desc, longVal, unsigned] of testCases) {
+			it(`${desc}: Long(${longVal.low}, ${longVal.high}, ${unsigned})`, () => {
+				const oldResult = longToNumberOld(longVal, unsigned)
+				const newResult = longToNumberNew(longVal, unsigned)
+				// For large values, both may lose precision equally (Number limitation)
+				// So we compare string representations
+				expect(newResult.toString()).toBe(oldResult.toString())
+			})
+		}
+	})
+
+	describe('non-Long inputs (fallback paths)', () => {
+		it('string passthrough', () => {
+			expect(longToStringNew('12345')).toBe('12345')
+			expect(longToStringNew('0')).toBe('0')
+		})
+		it('number passthrough', () => {
+			expect(longToStringNew(42)).toBe('42')
+			expect(longToStringNew(0)).toBe('0')
+			expect(longToStringNew(-1)).toBe('-1')
+		})
+		it('null/undefined fallback', () => {
+			expect(longToStringNew(null)).toBe('null')
+			expect(longToStringNew(undefined)).toBe('undefined')
+		})
+		it('object without low/high', () => {
+			expect(longToStringNew({ foo: 'bar' })).toBe('[object Object]')
+		})
+
+		// Defensive: a raw {low, high} JSON object can carry `high` as an
+		// unsigned 32-bit value (Long.fromBits would normalize via `| 0`,
+		// but plain JSON deserialization does not). Without `value.high | 0`
+		// the sign-bit check fails and the result is interpreted as unsigned.
+		// Upstream Baileys PR #2333 has this latent bug; InfiniteAPI fixes it.
+		it('signed sign-bit detection on raw unsigned high (-1 as {low: -1, high: 4294967295})', () => {
+			const raw = { low: -1, high: 0xffffffff }
+			// signed: -1
+			expect(longToStringNew(raw, false)).toBe('-1')
+			// unsigned: max uint64
+			expect(longToStringNew(raw, true)).toBe('18446744073709551615')
+		})
+
+		it('signed sign-bit detection on raw unsigned high (-4294967296 as {low: 0, high: 4294967295})', () => {
+			const raw = { low: 0, high: 0xffffffff }
+			// signed: -4294967296 (high word = -1 after normalization)
+			expect(longToStringNew(raw, false)).toBe('-4294967296')
+			// unsigned: 0xFFFFFFFF00000000 = 18446744069414584320
+			expect(longToStringNew(raw, true)).toBe('18446744069414584320')
+		})
+	})
+
+	describe('fuzz: random Long values', () => {
+		it('100 random unsigned values match', () => {
+			for (let i = 0; i < 100; i++) {
+				const low = (Math.random() * 0xffffffff) | 0
+				const high = (Math.random() * 0xffffffff) | 0
+				const longVal = Long.fromBits(low, high, true)
+				const oldResult = longToStringOld(longVal, true)
+				const newResult = longToStringNew(longVal, true)
+				expect(newResult).toBe(oldResult)
+			}
+		})
+
+		it('100 random signed values match', () => {
+			for (let i = 0; i < 100; i++) {
+				const low = (Math.random() * 0xffffffff) | 0
+				const high = (Math.random() * 0xffffffff) | 0
+				const longVal = Long.fromBits(low, high, false)
+				const oldResult = longToStringOld(longVal, false)
+				const newResult = longToStringNew(longVal, false)
+				expect(newResult).toBe(oldResult)
+			}
+		})
+	})
+})

src/__tests__/binary/reconnection-sync-skip.test.ts

@@ -0,0 +1,146 @@
+import { jest } from '@jest/globals'
+import { proto, type WAMessage } from '../..'
+import { DEFAULT_CONNECTION_CONFIG } from '../../Defaults'
+import makeWASocket from '../../Socket'
+import { makeSession, mockWebSocket } from '../TestUtils/session'
+
+mockWebSocket()
+
+// chats.ts treats a connection as a reconnection when EITHER signal is true:
+//   1. authState.creds.accountSyncCounter > 0
+//      (at least one full history sync completed in a previous session)
+//   2. socketSkippedOfflineBuffer (forwarded from socket.ts as `skipOfflineBuffer`)
+//      (socket.ts already decided to skip the offline buffer, e.g. because
+//       routingInfo was stale and was discarded on startup)
+// On reconnection, AwaitingInitialSync is skipped and the buffer is flushed
+// immediately so live messages are not held in the initial-sync window.
+describe('Reconnection Sync Skip', () => {
+	it('should skip the history sync wait on reconnection (accountSyncCounter > 0)', async () => {
+		const { state, clear } = await makeSession()
+
+		state.creds.me = { id: '1234567890:1@s.whatsapp.net', name: 'Test User' }
+		// Simulate a session that has already synced before
+		state.creds.accountSyncCounter = 1
+
+		const sock = makeWASocket({
+			...DEFAULT_CONNECTION_CONFIG,
+			auth: state
+		})
+
+		const messageListener = jest.fn()
+		sock.ev.on('messages.upsert', messageListener)
+
+		// Simulate receiving pending notifications (triggers AwaitingInitialSync)
+		sock.ev.emit('connection.update', { receivedPendingNotifications: true })
+
+		// Emit a message immediately after — if the wait is skipped,
+		// the buffer should already be flushed and this message should be delivered.
+		const msg = proto.WebMessageInfo.fromObject({
+			key: { remoteJid: '1234567890@s.whatsapp.net', fromMe: false, id: 'MSG_AFTER_RECONNECT' },
+			messageTimestamp: Date.now() / 1000,
+			message: { conversation: 'Hello after reconnect' }
+		}) as WAMessage
+		sock.ev.emit('messages.upsert', { messages: [msg], type: 'notify' })
+
+		await new Promise(resolve => setTimeout(resolve, 50))
+
+		// Message should be delivered immediately, NOT buffered
+		expect(messageListener).toHaveBeenCalledTimes(1)
+		expect(messageListener).toHaveBeenCalledWith(
+			expect.objectContaining({
+				messages: expect.arrayContaining([expect.objectContaining({ key: msg.key })]),
+				type: 'notify'
+			})
+		)
+
+		await sock.end(new Error('Test completed'))
+		await clear()
+	})
+
+	it('should skip the history sync wait when socketSkippedOfflineBuffer is true (stale routingInfo, accountSyncCounter === 0)', async () => {
+		const { state, clear } = await makeSession()
+
+		state.creds.me = { id: '1234567890:1@s.whatsapp.net', name: 'Test User' }
+		// Fresh-looking session from the counter perspective
+		state.creds.accountSyncCounter = 0
+		// But routingInfo is present and we ask the socket to discard it on start.
+		// socket.ts will set hadStaleRoutingInfo=true → skipOfflineBuffer=true,
+		// which chats.ts forwards as socketSkippedOfflineBuffer. Without this
+		// branch, the buffers would be misaligned (offline buffer skipped while
+		// AwaitingInitialSync still waits) and live messages would stall.
+		state.creds.routingInfo = Buffer.from([1, 2, 3, 4])
+
+		const sock = makeWASocket({
+			...DEFAULT_CONNECTION_CONFIG,
+			auth: state,
+			clearRoutingInfoOnStart: true
+		})
+
+		const messageListener = jest.fn()
+		sock.ev.on('messages.upsert', messageListener)
+
+		sock.ev.emit('connection.update', { receivedPendingNotifications: true })
+
+		const msg = proto.WebMessageInfo.fromObject({
+			key: { remoteJid: '1234567890@s.whatsapp.net', fromMe: false, id: 'MSG_AFTER_STALE_ROUTING' },
+			messageTimestamp: Date.now() / 1000,
+			message: { conversation: 'Hello after stale routing reconnect' }
+		}) as WAMessage
+		sock.ev.emit('messages.upsert', { messages: [msg], type: 'notify' })
+
+		await new Promise(resolve => setTimeout(resolve, 50))
+
+		expect(messageListener).toHaveBeenCalledTimes(1)
+		expect(messageListener).toHaveBeenCalledWith(
+			expect.objectContaining({
+				messages: expect.arrayContaining([expect.objectContaining({ key: msg.key })]),
+				type: 'notify'
+			})
+		)
+
+		await sock.end(new Error('Test completed'))
+		await clear()
+	})
+
+	it('should still wait for history sync on fresh pairing (both signals false)', async () => {
+		const { state, clear } = await makeSession()
+
+		state.creds.me = { id: '1234567890:1@s.whatsapp.net', name: 'Test User' }
+		// Fresh pairing — both reconnect signals are false:
+		// accountSyncCounter is 0 (default) and no stale routingInfo to clear.
+		state.creds.accountSyncCounter = 0
+
+		const sock = makeWASocket({
+			...DEFAULT_CONNECTION_CONFIG,
+			auth: state
+		})
+
+		const messageListener = jest.fn()
+		sock.ev.on('messages.upsert', messageListener)
+
+		sock.ev.emit('connection.update', { receivedPendingNotifications: true })
+
+		const msg = proto.WebMessageInfo.fromObject({
+			key: { remoteJid: '1234567890@s.whatsapp.net', fromMe: false, id: 'MSG_DURING_INITIAL_SYNC' },
+			messageTimestamp: Date.now() / 1000,
+			message: { conversation: 'Hello during initial sync' }
+		}) as WAMessage
+		sock.ev.emit('messages.upsert', { messages: [msg], type: 'notify' })
+
+		await new Promise(resolve => setTimeout(resolve, 50))
+
+		// Message should be BUFFERED (not delivered) because we're waiting for history sync
+		expect(messageListener).toHaveBeenCalledTimes(0)
+
+		// Drain the 2s AwaitingInitialSync timeout (chats.ts:1522) so its callback
+		// doesn't fire after Jest considers the test done — otherwise we get a
+		// "Cannot log after tests are done" warning from the post-teardown flush
+		// and the suite is flagged with --detectOpenHandles. After the timer
+		// fires, syncState becomes Online and the buffer flushes; that delivery
+		// is post-assertion and irrelevant to the test goal.
+		await new Promise(resolve => setTimeout(resolve, 2_100))
+
+		await sock.end(new Error('Test completed'))
+		await clear()
+	}, 10_000)
+})

src/__tests__/proto-tojson-long.test.ts

@@ -1,3 +1,4 @@
+import Long from 'long'
 import '../index.js'
 import { proto } from '../../WAProto/index.js'
 
@@ -28,4 +29,91 @@ describe('proto serialization', () => {
 		const json = message.toJSON()
 		expect(json.message?.imageMessage?.fileLength).toBe('1234567890123456789')
 	})
+
+	it('converts Long objects to strings correctly via BigInt fast path', () => {
+		const message = proto.WebMessageInfo.fromObject({
+			key: {
+				remoteJid: '123@s.whatsapp.net',
+				id: 'ABC123',
+				fromMe: false
+			},
+			messageTimestamp: Long.fromNumber(1700000000, true),
+			message: {
+				imageMessage: {
+					fileLength: Long.fromString('9876543210', true)
+				}
+			}
+		})
+
+		const json = message.toJSON()
+		expect(json.messageTimestamp).toBe('1700000000')
+		expect(json.message?.imageMessage?.fileLength).toBe('9876543210')
+	})
+
+	it('handles large unsigned Long values (> MAX_SAFE_INTEGER)', () => {
+		const message = proto.WebMessageInfo.fromObject({
+			key: {
+				remoteJid: '123@s.whatsapp.net',
+				id: 'ABC123',
+				fromMe: false
+			},
+			messageTimestamp: Long.fromString('18446744073709551615', true), // max uint64
+			message: {
+				imageMessage: {
+					fileLength: Long.fromString('9999999999999999999', true)
+				}
+			}
+		})
+
+		const json = message.toJSON()
+		expect(json.messageTimestamp).toBe('18446744073709551615')
+		expect(json.message?.imageMessage?.fileLength).toBe('9999999999999999999')
+	})
+
+	it('handles zero and small Long values', () => {
+		const message = proto.WebMessageInfo.fromObject({
+			key: {
+				remoteJid: '123@s.whatsapp.net',
+				id: 'ABC123',
+				fromMe: false
+			},
+			messageTimestamp: Long.fromNumber(0, true),
+			message: {
+				imageMessage: {
+					fileLength: Long.fromNumber(1, true)
+				}
+			}
+		})
+
+		const json = message.toJSON()
+		expect(json.messageTimestamp).toBe('0')
+		expect(json.message?.imageMessage?.fileLength).toBe('1')
+	})
+
+	it('roundtrips encode/decode with Long fields preserving values (> MAX_SAFE_INTEGER)', () => {
+		// Use uint64 values above Number.MAX_SAFE_INTEGER (2^53 - 1) so the
+		// roundtrip actually exercises the BigInt fast path on decode->toJSON.
+		// Safe integers would silently work even if longToString fell back to
+		// Number(value).
+		const original = proto.WebMessageInfo.fromObject({
+			key: {
+				remoteJid: '123@s.whatsapp.net',
+				id: 'ABC123',
+				fromMe: false
+			},
+			messageTimestamp: Long.fromString('18446744073709551615', true),
+			message: {
+				imageMessage: {
+					fileLength: Long.fromString('9999999999999999999', true)
+				}
+			}
+		})
+
+		const encoded = proto.WebMessageInfo.encode(original).finish()
+		const decoded = proto.WebMessageInfo.decode(encoded)
+		const json = decoded.toJSON()
+
+		expect(json.messageTimestamp).toBe('18446744073709551615')
+		expect(json.message?.imageMessage?.fileLength).toBe('9999999999999999999')
+	})
 })