diff --git a/.eslintrc.js b/.eslintrc.js
index 4869ff14..10e56c08 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -215,7 +215,13 @@ module.exports = {
                 '@typescript-eslint/no-dynamic-delete': 'off',
                 '@typescript-eslint/no-unsafe-member-access': 'off',
                 'no-restricted-globals': ['error', 'Buffer', '__dirname', 'require'],
-                'no-restricted-imports': ['error', 'buffer', 'crypto', 'fs', 'path', 'stream'],
+                'no-restricted-imports': [
+                    'error',
+                    {
+                        paths: ['buffer', 'crypto', 'fs', 'path', 'stream'],
+                        patterns: ['@mtcute/*/dist/**'],
+                    },
+                ],
             },
             reportUnusedDisableDirectives: false,
             settings: {
@@ -229,7 +235,12 @@ module.exports = {
             files: ['**/scripts/**', '*.test.ts', 'packages/create-*/**', '**/build.config.cjs'],
             rules: {
                 'no-console': 'off',
-                'no-restricted-imports': 'off',
+                'no-restricted-imports': [
+                    'error',
+                    {
+                        patterns: ['@mtcute/*/dist/**'],
+                    },
+                ],
             },
         },
         {
diff --git a/.lintstagedrc.cjs b/.lintstagedrc.cjs
index 0bd80c35..027814cc 100644
--- a/.lintstagedrc.cjs
+++ b/.lintstagedrc.cjs
@@ -13,10 +13,10 @@ module.exports = {
         }
 
         return [
+            ...[...modifiedPackages].map((pkg) => `pnpm -C packages/${pkg} exec tsc --build`),
             `prettier --write ${filenames.join(' ')}`,
             `eslint -c ${eslintCiConfig} --fix ${filenames.join(' ')}`,
             'pnpm run lint:dpdm',
-            ...[...modifiedPackages].map((pkg) => `pnpm -C packages/${pkg} run --if-present build --noEmit`)
         ]
     }
 }
diff --git a/packages/core/package.json b/packages/core/package.json
index 8d3fe741..0ecc6d05 100644
--- a/packages/core/package.json
+++ b/packages/core/package.json
@@ -53,6 +53,8 @@
     "devDependencies": {
         "@types/ws": "8.5.4",
         "node-forge": "1.3.1",
+        "@mtcute/test": "workspace:^",
+        "@mtcute/dispatcher": "workspace:^",
         "ws": "8.13.0"
     }
 }
diff --git a/packages/core/src/network/transports/intermediate.test.ts b/packages/core/src/network/transports/intermediate.test.ts
index fc017d36..fb9c7a33 100644
--- a/packages/core/src/network/transports/intermediate.test.ts
+++ b/packages/core/src/network/transports/intermediate.test.ts
@@ -2,7 +2,8 @@ import { describe, expect, it } from 'vitest'
 
 import { hexDecodeToBuffer, hexEncode } from '@mtcute/tl-runtime'
 
-import { IntermediatePacketCodec, TransportError } from '../../index.js'
+import { IntermediatePacketCodec, PaddedIntermediatePacketCodec, TransportError } from '../../index.js'
+import { concatBuffers, dataViewFromBuffer } from '../../utils/index.js'
 
 describe('IntermediatePacketCodec', () => {
     it('should return correct tag', () => {
@@ -76,4 +77,35 @@ describe('IntermediatePacketCodec', () => {
             codec.reset()
             codec.feed(hexDecodeToBuffer('050000000102030405'))
         }))
+
+    it('should correctly frame packets', () => {
+        const data = hexDecodeToBuffer('6cfeffff')
+
+        // eslint-disable-next-line no-restricted-globals
+        expect(Buffer.from(new IntermediatePacketCodec().encode(data))).toEqual(
+            concatBuffers([new Uint8Array([0x04, 0x00, 0x00, 0x00]), data]),
+        )
+    })
+})
+
+describe('PaddedIntermediatePacketCodec', () => {
+    it('should return correct tag', () => {
+        expect(hexEncode(new PaddedIntermediatePacketCodec().tag())).eq('dddddddd')
+    })
+
+    it('should correctly frame packets', () => {
+        // todo: once we have predictable random, test this properly
+
+        const data = hexDecodeToBuffer('6cfeffff')
+        const encoded = new PaddedIntermediatePacketCodec().encode(data)
+        const dv = dataViewFromBuffer(encoded)
+
+        const packetSize = dv.getUint32(0, true)
+        const paddingSize = packetSize - data.length
+
+        // padding size, 0-15
+        expect(paddingSize).toBeGreaterThanOrEqual(0)
+        expect(paddingSize).toBeLessThanOrEqual(15)
+        expect([...encoded.slice(4, 4 + packetSize - paddingSize)]).toEqual([...data])
+    })
 })
diff --git a/packages/core/src/storage/json.test.ts b/packages/core/src/storage/json.test.ts
new file mode 100644
index 00000000..7a9a0b3f
--- /dev/null
+++ b/packages/core/src/storage/json.test.ts
@@ -0,0 +1,42 @@
+import { describe, expect, it } from 'vitest'
+
+import { JsonMemoryStorage } from './json.js'
+import { stubPeerUser } from './storage.test-utils.js'
+
+describe('JsonMemoryStorage', () => {
+    class ExtJsonMemoryStorage extends JsonMemoryStorage {
+        loadJson(json: string): void {
+            this._loadJson(json)
+        }
+
+        saveJson(): string {
+            return this._saveJson()
+        }
+
+        getInternalState() {
+            return this._state
+        }
+    }
+
+    it('should allow importing and exporting to json', () => {
+        const s = new ExtJsonMemoryStorage()
+
+        s.setUpdatesPts(123)
+        s.setUpdatesQts(456)
+        // eslint-disable-next-line no-restricted-globals
+        s.setAuthKeyFor(1, Buffer.from([1, 2, 3]))
+        // eslint-disable-next-line no-restricted-globals
+        s.setTempAuthKeyFor(2, 0, Buffer.from([4, 5, 6]), 1234567890)
+        s.setState('someState', 'someValue')
+        s.updatePeers([{ ...stubPeerUser, updated: 0 }])
+
+        const json = s.saveJson()
+        const s2 = new ExtJsonMemoryStorage()
+        s2.loadJson(json)
+
+        expect(s2.getInternalState()).toEqual({
+            ...s.getInternalState(),
+            entities: new Map(), // entities are not saved
+        })
+    })
+})
diff --git a/packages/core/src/storage/json.ts b/packages/core/src/storage/json.ts
index 21922cb2..14801874 100644
--- a/packages/core/src/storage/json.ts
+++ b/packages/core/src/storage/json.ts
@@ -1,8 +1,6 @@
 /* eslint-disable @typescript-eslint/no-unsafe-return */
-import { tl } from '@mtcute/tl'
 import { base64DecodeToBuffer, base64Encode } from '@mtcute/tl-runtime'
 
-import { longFromFastString, longToFastString } from '../utils/long-utils.js'
 import { MemorySessionState, MemoryStorage } from './memory.js'
 
 /**
@@ -16,25 +14,26 @@ export class JsonMemoryStorage extends MemoryStorage {
                 switch (key) {
                     case 'authKeys':
                     case 'authKeysTemp': {
-                        const ret: Record<string, Uint8Array> = {}
+                        const ret = new Map<string | number, Uint8Array>()
 
                         ;(value as string).split('|').forEach((pair: string) => {
                             const [dcId, b64] = pair.split(',')
-                            ret[dcId] = base64DecodeToBuffer(b64)
+                            const mapKey = key === 'authKeysTemp' ? dcId : parseInt(dcId)
+
+                            ret.set(mapKey, base64DecodeToBuffer(b64))
                         })
 
                         return ret
                     }
                     case 'authKeysTempExpiry':
-                    case 'entities':
                     case 'phoneIndex':
                     case 'usernameIndex':
                     case 'pts':
                     case 'fsm':
                     case 'rl':
                         return new Map(Object.entries(value as Record<string, string>))
-                    case 'accessHash':
-                        return longFromFastString(value as string)
+                    case 'entities':
+                        return new Map()
                 }
 
                 return value
@@ -55,15 +54,14 @@ export class JsonMemoryStorage extends MemoryStorage {
                         .join('|')
                 }
                 case 'authKeysTempExpiry':
-                case 'entities':
                 case 'phoneIndex':
                 case 'usernameIndex':
                 case 'pts':
                 case 'fsm':
                 case 'rl':
                     return Object.fromEntries([...(value as Map<string, string>).entries()])
-                case 'accessHash':
-                    return longToFastString(value as tl.Long)
+                case 'entities':
+                    return {}
             }
 
             return value
diff --git a/packages/core/src/storage/localstorage.test.ts b/packages/core/src/storage/localstorage.test.ts
new file mode 100644
index 00000000..3e041277
--- /dev/null
+++ b/packages/core/src/storage/localstorage.test.ts
@@ -0,0 +1,26 @@
+import { afterAll, beforeAll, describe, expect, it, vi } from 'vitest'
+
+import { LocalstorageStorage } from './localstorage.js'
+
+const localStorageStub = {
+    getItem: vi.fn().mockImplementation(() => null),
+    setItem: vi.fn(),
+}
+describe('LocalstorageStorage', () => {
+    beforeAll(() => void vi.stubGlobal('localStorage', localStorageStub))
+    afterAll(() => void vi.unstubAllGlobals())
+
+    it('should load from localstorage', () => {
+        const s = new LocalstorageStorage('test')
+        s.load()
+
+        expect(localStorageStub.getItem).toHaveBeenCalledWith('test')
+    })
+
+    it('should save to localstorage', () => {
+        const s = new LocalstorageStorage('test')
+        s.save()
+
+        expect(localStorageStub.setItem).toHaveBeenCalledWith('test', expect.any(String))
+    })
+})
diff --git a/packages/core/src/storage/localstorage.ts b/packages/core/src/storage/localstorage.ts
index beef3a29..d041740c 100644
--- a/packages/core/src/storage/localstorage.ts
+++ b/packages/core/src/storage/localstorage.ts
@@ -16,11 +16,14 @@ export class LocalstorageStorage extends JsonMemoryStorage {
 
     load(): void {
         try {
-            this._loadJson(localStorage[this._key] as string)
+            const val = localStorage.getItem(this._key)
+            if (val === null) return
+
+            this._loadJson(val)
         } catch (e) {}
     }
 
     save(): void {
-        localStorage[this._key] = this._saveJson()
+        localStorage.setItem(this._key, this._saveJson())
     }
 }
diff --git a/packages/core/src/storage/memory.test.ts b/packages/core/src/storage/memory.test.ts
new file mode 100644
index 00000000..dc74cd18
--- /dev/null
+++ b/packages/core/src/storage/memory.test.ts
@@ -0,0 +1,52 @@
+import { describe, expect, it } from 'vitest'
+
+import { MemoryStorage } from './memory.js'
+import { testStateStorage, testStorage } from './storage.test-utils.js'
+
+describe('MemoryStorage', () => {
+    testStorage(new MemoryStorage())
+    testStateStorage(new MemoryStorage())
+
+    describe('extending', () => {
+        it('should allow populating from an object', () => {
+            class ExtendedMemoryStorage extends MemoryStorage {
+                constructor() {
+                    super()
+                    this._setStateFrom({
+                        $version: 1,
+                        defaultDcs: null,
+                        authKeys: new Map(),
+                        authKeysTemp: new Map(),
+                        authKeysTempExpiry: new Map(),
+                        entities: new Map(),
+                        phoneIndex: new Map(),
+                        usernameIndex: new Map(),
+                        gpts: [1, 2, 3, 4],
+                        pts: new Map(),
+                        fsm: new Map(),
+                        rl: new Map(),
+                        self: null,
+                    })
+                }
+            }
+
+            const s = new ExtendedMemoryStorage()
+
+            expect(s.getUpdatesState()).toEqual([1, 2, 3, 4])
+        })
+
+        it('should silently fail if version is wrong', () => {
+            class ExtendedMemoryStorage extends MemoryStorage {
+                constructor() {
+                    super()
+                    // eslint-disable-next-line
+                    this._setStateFrom({ $version: 0 } as any)
+                }
+            }
+
+            const s = new ExtendedMemoryStorage()
+
+            expect(s.getUpdatesState()).toEqual(null)
+        })
+    })
+})
diff --git a/packages/core/src/storage/memory.ts b/packages/core/src/storage/memory.ts
index 0467b17d..8541590d 100644
--- a/packages/core/src/storage/memory.ts
+++ b/packages/core/src/storage/memory.ts
@@ -1,6 +1,6 @@
+import { IStateStorage } from '@mtcute/dispatcher'
 import { tl } from '@mtcute/tl'
 
-import { MaybeAsync } from '../types/index.js'
 import { LruMap, toggleChannelIdMark } from '../utils/index.js'
 import { ITelegramStorage } from './abstract.js'
 
@@ -56,7 +56,7 @@ export interface MemorySessionState {
 
 const USERNAME_TTL = 86400000 // 24 hours
 
-export class MemoryStorage implements ITelegramStorage /*, IStateStorage*/ {
+export class MemoryStorage implements ITelegramStorage, IStateStorage {
     protected _state!: MemorySessionState
     private _cachedInputPeers: LruMap<number, tl.TypeInputPeer> = new LruMap(100)
 
@@ -131,11 +131,11 @@ export class MemoryStorage implements ITelegramStorage /*, IStateStorage*/ {
         // populate indexes if needed
         let populate = false
 
-        if (!obj.phoneIndex) {
+        if (!obj.phoneIndex?.size) {
             obj.phoneIndex = new Map()
             populate = true
         }
-        if (!obj.usernameIndex) {
+        if (!obj.usernameIndex?.size) {
             obj.usernameIndex = new Map()
             populate = true
         }
@@ -229,7 +229,7 @@ export class MemoryStorage implements ITelegramStorage /*, IStateStorage*/ {
         }
     }
 
-    updatePeers(peers: PeerInfoWithUpdated[]): MaybeAsync<void> {
+    updatePeers(peers: PeerInfoWithUpdated[]): void {
         for (const peer of peers) {
             this._cachedFull.set(peer.id, peer.full)
 
@@ -326,26 +326,26 @@ export class MemoryStorage implements ITelegramStorage /*, IStateStorage*/ {
         return this._state.pts.get(entityId) ?? null
     }
 
-    getUpdatesState(): MaybeAsync<[number, number, number, number] | null> {
+    getUpdatesState(): [number, number, number, number] | null {
         return this._state.gpts ?? null
     }
 
-    setUpdatesPts(val: number): MaybeAsync<void> {
+    setUpdatesPts(val: number): void {
         if (!this._state.gpts) this._state.gpts = [0, 0, 0, 0]
         this._state.gpts[0] = val
     }
 
-    setUpdatesQts(val: number): MaybeAsync<void> {
+    setUpdatesQts(val: number): void {
         if (!this._state.gpts) this._state.gpts = [0, 0, 0, 0]
         this._state.gpts[1] = val
     }
 
-    setUpdatesDate(val: number): MaybeAsync<void> {
+    setUpdatesDate(val: number): void {
         if (!this._state.gpts) this._state.gpts = [0, 0, 0, 0]
         this._state.gpts[2] = val
     }
 
-    setUpdatesSeq(val: number): MaybeAsync<void> {
+    setUpdatesSeq(val: number): void {
         if (!this._state.gpts) this._state.gpts = [0, 0, 0, 0]
         this._state.gpts[3] = val
     }
diff --git a/packages/core/src/storage/storage.test-utils.ts b/packages/core/src/storage/storage.test-utils.ts
new file mode 100644
index 00000000..cbed3ee7
--- /dev/null
+++ b/packages/core/src/storage/storage.test-utils.ts
@@ -0,0 +1,332 @@
+import Long from 'long'
+import { afterAll, beforeAll, beforeEach, describe, expect, it, vi } from 'vitest'
+
+import type { IStateStorage } from '@mtcute/dispatcher'
+import { createStub } from '@mtcute/test'
+import { tl } from '@mtcute/tl'
+import { __tlReaderMap } from '@mtcute/tl/binary/reader.js'
+import { __tlWriterMap } from '@mtcute/tl/binary/writer.js'
+
+import { defaultProductionDc } from '../utils/default-dcs.js'
+import { LogManager } from '../utils/index.js'
+import { ITelegramStorage } from './abstract.js'
+
+export const stubPeerUser: ITelegramStorage.PeerInfo = {
+    id: 123123,
+    accessHash: Long.fromBits(123, 456),
+    type: 'user',
+    username: 'some_user',
+    phone: '78005553535',
+    full: createStub('user', { id: 123123 }),
+}
+const peerUserInput: tl.TypeInputPeer = {
+    _: 'inputPeerUser',
+    userId: 123123,
+    accessHash: Long.fromBits(123, 456),
+}
+
+const peerChannel: ITelegramStorage.PeerInfo = {
+    id: -1001183945448,
+    accessHash: Long.fromBits(666, 555),
+    type: 'channel',
+    username: 'some_channel',
+    full: createStub('channel', { id: 123123 }),
+}
+
+const peerChannelInput: tl.TypeInputPeer = {
+    _: 'inputPeerChannel',
+    channelId: 1183945448,
+    accessHash: Long.fromBits(666, 555),
+}
+
+export function testStorage(s: ITelegramStorage): void {
+    beforeAll(async () => {
+        await s.load?.()
+
+        const logger = new LogManager()
+        logger.level = 0
+        s.setup?.(logger, __tlReaderMap, __tlWriterMap)
+    })
+
+    afterAll(() => s.destroy?.())
+    beforeEach(() => s.reset?.())
+
+    describe('default dc', () => {
+        it('should store', async () => {
+            await s.setDefaultDcs(defaultProductionDc)
+            expect(await s.getDefaultDcs()).toBe(defaultProductionDc)
+        })
+
+        it('should remove', async () => {
+            await s.setDefaultDcs(null)
+            expect(await s.getDefaultDcs()).toBeNull()
+        })
+    })
+
+    describe('auth keys', () => {
+        beforeAll(() => void vi.useFakeTimers())
+        afterAll(() => void vi.useRealTimers())
+
+        const key2 = new Uint8Array(256).fill(0x42)
+        const key3 = new Uint8Array(256).fill(0x43)
+
+        const key2i0 = new Uint8Array(256).fill(0x44)
+        const key2i1 = new Uint8Array(256).fill(0x45)
+        const key3i0 = new Uint8Array(256).fill(0x46)
+        const key3i1 = new Uint8Array(256).fill(0x47)
+
+        it('should store perm auth key', async () => {
+            await s.setAuthKeyFor(2, key2)
+            await s.setAuthKeyFor(3, key3)
+
+            expect(await s.getAuthKeyFor(2)).toEqual(key2)
+            expect(await s.getAuthKeyFor(3)).toEqual(key3)
+        })
+
+        it('should store temp auth keys', async () => {
+            const expire = Date.now() + 1000
+
+            await s.setTempAuthKeyFor(2, 0, key2i0, expire)
+            await s.setTempAuthKeyFor(2, 1, key2i1, expire)
+            await s.setTempAuthKeyFor(3, 0, key3i0, expire)
+            await s.setTempAuthKeyFor(3, 1, key3i1, expire)
+
+            expect(await s.getAuthKeyFor(2, 0)).toEqual(key2i0)
+            expect(await s.getAuthKeyFor(2, 1)).toEqual(key2i1)
+            expect(await s.getAuthKeyFor(3, 0)).toEqual(key3i0)
+            expect(await s.getAuthKeyFor(3, 1)).toEqual(key3i1)
+        })
+
+        it('should expire temp auth keys', async () => {
+            const expire = Date.now() + 1000
+
+            await s.setTempAuthKeyFor(2, 0, key2i0, expire)
+            await s.setTempAuthKeyFor(2, 1, key2i1, expire)
+            await s.setTempAuthKeyFor(3, 0, key3i0, expire)
+            await s.setTempAuthKeyFor(3, 1, key3i1, expire)
+
+            vi.advanceTimersByTime(10000)
+
+            expect(await s.getAuthKeyFor(2, 0)).toBeNull()
+            expect(await s.getAuthKeyFor(2, 1)).toBeNull()
+            expect(await s.getAuthKeyFor(3, 0)).toBeNull()
+            expect(await s.getAuthKeyFor(3, 1)).toBeNull()
+        })
+
+        it('should remove auth keys', async () => {
+            const expire = Date.now() + 1000
+
+            await s.setTempAuthKeyFor(2, 0, key2i0, expire)
+            await s.setTempAuthKeyFor(2, 1, key2i1, expire)
+            await s.setAuthKeyFor(2, key2)
+            await s.setAuthKeyFor(3, key3)
+
+            await s.setAuthKeyFor(2, null)
+            await s.setTempAuthKeyFor(2, 0, null, 0)
+            await s.setTempAuthKeyFor(2, 1, null, 0)
+
+            expect(await s.getAuthKeyFor(2)).toBeNull()
+            expect(await s.getAuthKeyFor(2, 0)).toBeNull()
+            expect(await s.getAuthKeyFor(2, 1)).toBeNull()
+            expect(await s.getAuthKeyFor(3)).toEqual(key3) // should not be removed
+        })
+
+        it('should remove all auth keys with dropAuthKeysFor', async () => {
+            const expire = Date.now() + 1000
+
+            await s.setTempAuthKeyFor(2, 0, key2i0, expire)
+            await s.setTempAuthKeyFor(2, 1, key2i1, expire)
+            await s.setAuthKeyFor(2, key2)
+            await s.setAuthKeyFor(3, key3)
+
+            await s.dropAuthKeysFor(2)
+
+            expect(await s.getAuthKeyFor(2)).toBeNull()
+            expect(await s.getAuthKeyFor(2, 0)).toBeNull()
+            expect(await s.getAuthKeyFor(2, 1)).toBeNull()
+            expect(await s.getAuthKeyFor(3)).toEqual(key3) // should not be removed
+        })
+    })
+
+    describe('peers', () => {
+        it('should cache and return peers', async () => {
+            await s.updatePeers([stubPeerUser, peerChannel])
+
+            expect(await s.getPeerById(stubPeerUser.id)).toEqual(peerUserInput)
+            expect(await s.getPeerById(peerChannel.id)).toEqual(peerChannelInput)
+        })
+
+        it('should cache and return peers by username', async () => {
+            await s.updatePeers([stubPeerUser, peerChannel])
+
+            expect(await s.getPeerByUsername(stubPeerUser.username!)).toEqual(peerUserInput)
+            expect(await s.getPeerByUsername(peerChannel.username!)).toEqual(peerChannelInput)
+        })
+
+        it('should cache and return peers by phone', async () => {
+            await s.updatePeers([stubPeerUser])
+
+            expect(await s.getPeerByPhone(stubPeerUser.phone!)).toEqual(peerUserInput)
+        })
+
+        it('should overwrite existing cached peers', async () => {
+            await s.updatePeers([stubPeerUser])
+            await s.updatePeers([{ ...stubPeerUser, username: 'whatever' }])
+
+            expect(await s.getPeerById(stubPeerUser.id)).toEqual(peerUserInput)
+            expect(await s.getPeerByUsername(stubPeerUser.username!)).toBeNull()
+            expect(await s.getPeerByUsername('whatever')).toEqual(peerUserInput)
+        })
+
+        it('should cache full peer info', async () => {
+            await s.updatePeers([stubPeerUser, peerChannel])
+
+            expect(await s.getFullPeerById(stubPeerUser.id)).toEqual(stubPeerUser.full)
+            expect(await s.getFullPeerById(peerChannel.id)).toEqual(peerChannel.full)
+        })
+    })
+
+    describe('current user', () => {
+        const self: ITelegramStorage.SelfInfo = {
+            userId: 123123,
+            isBot: false,
+        }
+
+        it('should store and return self info', async () => {
+            await s.setSelf(self)
+            expect(await s.getSelf()).toEqual(self)
+        })
+
+        it('should remove self info', async () => {
+            await s.setSelf(self)
+            await s.setSelf(null)
+            expect(await s.getSelf()).toBeNull()
+        })
+    })
+
+    describe('updates state', () => {
+        it('should store and return updates state', async () => {
+            await s.setUpdatesPts(1)
+            await s.setUpdatesQts(2)
+            await s.setUpdatesDate(3)
+            await s.setUpdatesSeq(4)
+            expect(await s.getUpdatesState()).toEqual([1, 2, 3, 4])
+        })
+
+        it('should store and return channel pts', async () => {
+            await s.setManyChannelPts(
+                new Map([
+                    [1, 2],
+                    [3, 4],
+                ]),
+            )
+
+            expect(await s.getChannelPts(1)).toEqual(2)
+            expect(await s.getChannelPts(3)).toEqual(4)
+            expect(await s.getChannelPts(2)).toBeNull()
+        })
+
+        it('should be null after reset', async () => {
+            expect(await s.getUpdatesState()).toBeNull()
+        })
+    })
+}
+
+export function testStateStorage(s: IStateStorage) {
+    describe('key-value state', () => {
+        beforeAll(() => void vi.useFakeTimers())
+        afterAll(() => void vi.useRealTimers())
+
+        it('should store and return state', async () => {
+            await s.setState('a', 'b')
+            await s.setState('c', 'd')
+            await s.setState('e', 'f')
+
+            expect(await s.getState('a')).toEqual('b')
+            expect(await s.getState('c')).toEqual('d')
+            expect(await s.getState('e')).toEqual('f')
+        })
+
+        it('should remove state', async () => {
+            await s.setState('a', 'b')
+            await s.setState('c', 'd')
+            await s.setState('e', 'f')
+
+            await s.deleteState('a')
+            await s.deleteState('c')
+            await s.deleteState('e')
+
+            expect(await s.getState('a')).toBeNull()
+            expect(await s.getState('c')).toBeNull()
+            expect(await s.getState('e')).toBeNull()
+        })
+
+        it('should expire state', async () => {
+            await s.setState('a', 'b', 1)
+            await s.setState('c', 'd', 1)
+            await s.setState('e', 'f', 1)
+
+            vi.advanceTimersByTime(10000)
+
+            expect(await s.getState('a')).toBeNull()
+            expect(await s.getState('c')).toBeNull()
+            expect(await s.getState('e')).toBeNull()
+        })
+    })
+
+    describe('scenes', () => {
+        it('should store and return scenes', async () => {
+            await s.setCurrentScene('a', 'b')
+            await s.setCurrentScene('c', 'd')
+            await s.setCurrentScene('e', 'f')
+
+            expect(await s.getCurrentScene('a')).toEqual('b')
+            expect(await s.getCurrentScene('c')).toEqual('d')
+            expect(await s.getCurrentScene('e')).toEqual('f')
+        })
+
+        it('should remove scenes', async () => {
+            await s.setCurrentScene('a', 'b')
+            await s.setCurrentScene('c', 'd')
+            await s.setCurrentScene('e', 'f')
+
+            await s.deleteCurrentScene('a')
+            await s.deleteCurrentScene('c')
+            await s.deleteCurrentScene('e')
+
+            expect(await s.getCurrentScene('a')).toBeNull()
+            expect(await s.getCurrentScene('c')).toBeNull()
+            expect(await s.getCurrentScene('e')).toBeNull()
+        })
+    })
+
+    describe('rate limit', () => {
+        beforeAll(() => void vi.useFakeTimers())
+        afterAll(() => void vi.useRealTimers())
+
+        const check = () => s.getRateLimit('test', 3, 1)
+
+        it('should implement basic rate limiting', async () => {
+            vi.setSystemTime(0)
+
+            expect(await check()).toEqual([3, 1000])
+            expect(await check()).toEqual([2, 1000])
+            expect(await check()).toEqual([1, 1000])
+            expect(await check()).toEqual([0, 1000])
+
+            vi.setSystemTime(1001)
+
+            expect(await check()).toEqual([3, 2001])
+        })
+
+        it('should allow resetting rate limit', async () => {
+            vi.setSystemTime(0)
+
+            await check()
+            await check()
+
+            await s.resetRateLimit('test')
+            expect(await check()).toEqual([3, 1000])
+        })
+    })
+}
diff --git a/packages/core/src/utils/async-lock.test.ts b/packages/core/src/utils/async-lock.test.ts
new file mode 100644
index 00000000..54e879c1
--- /dev/null
+++ b/packages/core/src/utils/async-lock.test.ts
@@ -0,0 +1,32 @@
+import { describe, expect, it } from 'vitest'
+
+import { AsyncLock } from './async-lock.js'
+import { sleep } from './misc-utils.js'
+
+describe('AsyncLock', () => {
+    it('should correctly lock execution', async () => {
+        const lock = new AsyncLock()
+
+        const log: number[] = []
+        await Promise.all(
+            Array.from({ length: 10 }, (_, idx) =>
+                lock.with(async () => {
+                    await sleep(10 - idx)
+                    log.push(idx)
+                }),
+            ),
+        )
+
+        expect(log).toEqual([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
+    })
+
+    it('should correctly propagate errors', async () => {
+        const lock = new AsyncLock()
+
+        await expect(async () => {
+            await lock.with(() => {
+                throw new Error('test')
+            })
+        }).rejects.toThrow('test')
+    })
+})
diff --git a/packages/core/src/utils/bigint-utils.test.ts b/packages/core/src/utils/bigint-utils.test.ts
index 54dd72af..44a24a94 100644
--- a/packages/core/src/utils/bigint-utils.test.ts
+++ b/packages/core/src/utils/bigint-utils.test.ts
@@ -2,7 +2,28 @@ import { describe, expect, it } from 'vitest'
 
 import { hexDecodeToBuffer } from '@mtcute/tl-runtime'
 
-import { bigIntToBuffer, bufferToBigInt } from './index.js'
+import {
+    bigIntBitLength,
+    bigIntGcd,
+    bigIntModInv,
+    bigIntModPow,
+    bigIntToBuffer,
+    bufferToBigInt,
+    randomBigInt,
+    randomBigIntBits,
+    randomBigIntInRange,
+    twoMultiplicity,
+} from './index.js'
+
+describe('bigIntBitLength', () => {
+    it('should correctly calculate bit length', () => {
+        expect(bigIntBitLength(0n)).eq(0)
+        expect(bigIntBitLength(1n)).eq(1)
+        expect(bigIntBitLength(2n)).eq(2)
+        expect(bigIntBitLength(255n)).eq(8)
+        expect(bigIntBitLength(256n)).eq(9)
+    })
+})
 
 describe('bigIntToBuffer', () => {
     it('should handle writing to BE', () => {
@@ -63,3 +84,111 @@ describe('bufferToBigInt', () => {
         expect(bufferToBigInt(buf.reverse(), true).toString()).eq(num.toString())
     })
 })
+
+describe('randomBigInt', () => {
+    it('should return a random bigint', () => {
+        const a = randomBigInt(32)
+        const b = randomBigInt(32)
+
+        expect(a).not.toEqual(b)
+    })
+
+    it('should return a random bigint up to specified byte length', () => {
+        const a = randomBigInt(32)
+        const b = randomBigInt(64)
+
+        expect(bigIntBitLength(a)).toBeLessThanOrEqual(32 * 8)
+        expect(bigIntBitLength(b)).toBeLessThanOrEqual(64 * 8)
+    })
+})
+
+describe('randomBigIntBits', () => {
+    it('should return a random bigint', () => {
+        const a = randomBigIntBits(32)
+        const b = randomBigIntBits(32)
+
+        expect(a).not.toEqual(b)
+    })
+
+    it('should return a random bigint up to specified bit length', () => {
+        const a = randomBigIntBits(32)
+        const b = randomBigIntBits(64)
+
+        expect(bigIntBitLength(a)).toBeLessThanOrEqual(32)
+        expect(bigIntBitLength(b)).toBeLessThanOrEqual(64)
+    })
+})
+
+describe('randomBigIntInRange', () => {
+    it('should return a random bigint', () => {
+        const a = randomBigIntInRange(10000n)
+        const b = randomBigIntInRange(10000n)
+
+        expect(a).not.toEqual(b)
+    })
+
+    it('should return a bigint within a given range', () => {
+        const a = randomBigIntInRange(200n, 100n)
+
+        expect(a).toBeGreaterThanOrEqual(100n)
+        expect(a).toBeLessThan(200n)
+    })
+})
+
+describe('twoMultiplicity', () => {
+    it('should return the multiplicity of 2 in the prime factorization of n', () => {
+        expect(twoMultiplicity(0n)).toEqual(0n)
+        expect(twoMultiplicity(1n)).toEqual(0n)
+        expect(twoMultiplicity(2n)).toEqual(1n)
+        expect(twoMultiplicity(4n)).toEqual(2n)
+        expect(twoMultiplicity(65536n)).toEqual(16n)
+        expect(twoMultiplicity(65537n)).toEqual(0n)
+    })
+})
+
+describe('bigIntGcd', () => {
+    it('should return the greatest common divisor of a and b', () => {
+        expect(bigIntGcd(123n, 456n)).toEqual(3n)
+    })
+
+    it('should correctly handle zeros', () => {
+        expect(bigIntGcd(0n, 0n)).toEqual(0n)
+        expect(bigIntGcd(0n, 1n)).toEqual(1n)
+        expect(bigIntGcd(1n, 0n)).toEqual(1n)
+    })
+
+    it('should correctly handle equal values', () => {
+        expect(bigIntGcd(1n, 1n)).toEqual(1n)
+    })
+})
+
+describe('bigIntModPow', () => {
+    it('should correctly calculate modular exponentiation', () => {
+        expect(bigIntModPow(2n, 3n, 5n)).toEqual(3n)
+        expect(bigIntModPow(2n, 3n, 6n)).toEqual(2n)
+        expect(bigIntModPow(2n, 3n, 7n)).toEqual(1n)
+        expect(bigIntModPow(2n, 3n, 8n)).toEqual(0n)
+    })
+
+    it('should correctly handle very large numbers', () => {
+        // calculating this with BigInt would either take forever or error with "Maximum BigInt size exceeded
+        expect(bigIntModPow(2n, 100000000000n, 100n)).toEqual(76n)
+    })
+})
+
+describe('bigIntModInv', () => {
+    it('should correctly calculate modular inverse', () => {
+        expect(bigIntModInv(2n, 5n)).toEqual(3n)
+        expect(bigIntModInv(2n, 7n)).toEqual(4n)
+    })
+
+    it("should error if there's no modular inverse", () => {
+        expect(() => bigIntModInv(2n, 6n)).toThrow(RangeError)
+        expect(() => bigIntModInv(2n, 8n)).toThrow(RangeError)
+    })
+
+    it('should correctly handle very large numbers', () => {
+        // calculating this with BigInt would either take forever or error with "Maximum BigInt size exceeded
+        expect(bigIntModInv(123123123123n, 1829n)).toEqual(318n)
+    })
+})
diff --git a/packages/core/src/utils/buffer-utils.test.ts b/packages/core/src/utils/buffer-utils.test.ts
index da722589..6cd025f0 100644
--- a/packages/core/src/utils/buffer-utils.test.ts
+++ b/packages/core/src/utils/buffer-utils.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it } from 'vitest'
+import { afterEach, describe, expect, it, vi } from 'vitest'
 
 import { hexEncode, utf8Decode, utf8EncodeToBuffer } from '@mtcute/tl-runtime'
 
@@ -121,6 +121,19 @@ describe('concatBuffers', () => {
         buf[0] = 0xff
         expect(buf1[0]).not.eql(0xff)
     })
+
+    it('should work without native Buffer', () => {
+        vi.stubGlobal('Buffer', undefined)
+        const buf1 = new Uint8Array([1, 2, 3])
+        const buf2 = new Uint8Array([4, 5, 6])
+        const buf = concatBuffers([buf1, buf2])
+
+        buf1[0] = 0xff
+
+        expect([...buf]).eql([1, 2, 3, 4, 5, 6])
+    })
+
+    afterEach(() => void vi.unstubAllGlobals())
 })
 
 describe('bufferToReversed', () => {
diff --git a/packages/core/src/utils/condition-variable.test.ts b/packages/core/src/utils/condition-variable.test.ts
new file mode 100644
index 00000000..eb0e312a
--- /dev/null
+++ b/packages/core/src/utils/condition-variable.test.ts
@@ -0,0 +1,36 @@
+import { describe, expect, it } from 'vitest'
+
+import { ConditionVariable } from './condition-variable.js'
+
+describe('ConditionVariable', () => {
+    it('should correctly unlock execution', async () => {
+        const cv = new ConditionVariable()
+
+        setTimeout(() => cv.notify(), 10)
+
+        await cv.wait()
+
+        expect(true).toBeTruthy()
+    })
+
+    it('should correctly time out', async () => {
+        const cv = new ConditionVariable()
+
+        await cv.wait(10)
+
+        expect(true).toBeTruthy()
+    })
+
+    it('should only unlock once', async () => {
+        const cv = new ConditionVariable()
+
+        setTimeout(() => {
+            cv.notify()
+            cv.notify()
+        }, 10)
+
+        await cv.wait()
+
+        expect(true).toBeTruthy()
+    })
+})
diff --git a/packages/core/src/utils/controllable-promise.test.ts b/packages/core/src/utils/controllable-promise.test.ts
new file mode 100644
index 00000000..a638de51
--- /dev/null
+++ b/packages/core/src/utils/controllable-promise.test.ts
@@ -0,0 +1,17 @@
+import { describe, expect, it } from 'vitest'
+
+import { createControllablePromise } from './controllable-promise.js'
+
+describe('createControllablePromise', () => {
+    it('should resolve', async () => {
+        const p = createControllablePromise()
+        p.resolve(1)
+        await expect(p).resolves.toBe(1)
+    })
+
+    it('should reject', async () => {
+        const p = createControllablePromise()
+        p.reject(1)
+        await expect(p).rejects.toBe(1)
+    })
+})
diff --git a/packages/core/src/utils/crypto/crypto.test-utils.ts b/packages/core/src/utils/crypto/crypto.test-utils.ts
index 6cd5b6ce..e9614f11 100644
--- a/packages/core/src/utils/crypto/crypto.test-utils.ts
+++ b/packages/core/src/utils/crypto/crypto.test-utils.ts
@@ -1,8 +1,10 @@
 import { beforeAll, expect, it } from 'vitest'
+import { gzipSync, inflateSync } from 'zlib'
 
 import { hexDecodeToBuffer, hexEncode, utf8EncodeToBuffer } from '@mtcute/tl-runtime'
 
 import { ICryptoProvider } from './abstract.js'
+import { factorizePQSync } from './factorization.js'
 
 export function testCryptoProvider(c: ICryptoProvider): void {
     beforeAll(() => c.initialize?.())
@@ -93,4 +95,46 @@ export function testCryptoProvider(c: ICryptoProvider): void {
             ),
         ).to.eq('99706487a1cde613bc6de0b6f24b1c7aa448c8b9c3403e3467a8cad89340f53b')
     })
+
+    it(
+        'should decompose PQ to prime factors P and Q',
+        () => {
+            const testFactorization = (pq: string, p: string, q: string) => {
+                const [p1, q1] = factorizePQSync(hexDecodeToBuffer(pq))
+                expect(hexEncode(p1)).eq(p.toLowerCase())
+                expect(hexEncode(q1)).eq(q.toLowerCase())
+            }
+
+            // from samples at https://core.telegram.org/mtproto/samples-auth_key
+            testFactorization('17ED48941A08F981', '494C553B', '53911073')
+            // random example
+            testFactorization('14fcab4dfc861f45', '494c5c99', '494c778d')
+        },
+        // since PQ factorization relies on RNG, it may take a while (or may not!)
+        { timeout: 10000 },
+    )
+
+    it('should correctly gzip', () => {
+        const data = new Uint8Array(1000).fill(0x42)
+
+        const compressed = c.gzip(data, 100)
+
+        expect(compressed).not.toBeNull()
+
+        const decompressed = inflateSync(compressed!)
+
+        expect(compressed!.length).toBeLessThan(data.length)
+        // eslint-disable-next-line no-restricted-globals
+        expect(decompressed).toEqual(Buffer.from(data))
+    })
+
+    it('should correctly gunzip', () => {
+        const data = new Uint8Array(1000).fill(0x42)
+
+        const compressed = gzipSync(data)
+        const decompressed = c.gunzip(compressed)
+
+        // eslint-disable-next-line no-restricted-globals
+        expect(Buffer.from(decompressed)).toEqual(Buffer.from(data))
+    })
 }
diff --git a/packages/core/src/utils/crypto/factorization.test.ts b/packages/core/src/utils/crypto/factorization.test.ts
deleted file mode 100644
index 665891f3..00000000
--- a/packages/core/src/utils/crypto/factorization.test.ts
+++ /dev/null
@@ -1,24 +0,0 @@
-import { describe, expect, it } from 'vitest'
-
-import { hexDecodeToBuffer, hexEncode } from '@mtcute/tl-runtime'
-
-import { factorizePQSync } from './factorization.js'
-
-describe(
-    'prime factorization',
-    function () {
-        it('should decompose PQ to prime factors P and Q', () => {
-            const testFactorization = (pq: string, p: string, q: string) => {
-                const [p1, q1] = factorizePQSync(hexDecodeToBuffer(pq))
-                expect(hexEncode(p1)).eq(p.toLowerCase())
-                expect(hexEncode(q1)).eq(q.toLowerCase())
-            }
-
-            // from samples at https://core.telegram.org/mtproto/samples-auth_key
-            testFactorization('17ED48941A08F981', '494C553B', '53911073')
-            // random example
-            testFactorization('14fcab4dfc861f45', '494c5c99', '494c778d')
-        })
-    },
-    { timeout: 10000 },
-) // since PQ factorization relies on RNG, it may take a while (or may not!)
diff --git a/packages/core/src/utils/crypto/keys.test.ts b/packages/core/src/utils/crypto/keys.test.ts
index a0c9a508..965160b5 100644
--- a/packages/core/src/utils/crypto/keys.test.ts
+++ b/packages/core/src/utils/crypto/keys.test.ts
@@ -1,6 +1,6 @@
 import { describe, expect, it } from 'vitest'
 
-import { parsePublicKey } from '../index.js'
+import { findKeyByFingerprints, parsePublicKey } from '../index.js'
 import { NodeCryptoProvider } from './node.js'
 
 const crypto = new NodeCryptoProvider()
@@ -27,4 +27,23 @@ XGF710w9lwCGNbmNxNYhtIkdqfsEcwR5JwIDAQAB
             old: false,
         })
     })
+
+    it('should be able to find a key by its fingerprint', () => {
+        expect(findKeyByFingerprints(['b25898df208d2603'])).toMatchInlineSnapshot(`
+          {
+            "exponent": "010001",
+            "fingerprint": "b25898df208d2603",
+            "modulus": "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",
+            "old": false,
+          }
+        `)
+    })
+
+    it('should prefer new keys over old', () => {
+        expect(findKeyByFingerprints(['71e025b6c76033e3', 'b25898df208d2603'])?.fingerprint).toEqual('b25898df208d2603')
+    })
+
+    it('should return null if not found', () => {
+        expect(findKeyByFingerprints(['deadbeefdeadbeef'])).toBeNull()
+    })
 })
diff --git a/packages/core/src/utils/crypto/password.test.ts b/packages/core/src/utils/crypto/password.test.ts
new file mode 100644
index 00000000..020b96c6
--- /dev/null
+++ b/packages/core/src/utils/crypto/password.test.ts
@@ -0,0 +1,76 @@
+import { describe, expect, it } from 'vitest'
+
+import { tl } from '@mtcute/tl'
+import { hexDecodeToBuffer, hexEncode, utf8EncodeToBuffer } from '@mtcute/tl-runtime'
+
+import { computePasswordHash, defaultCryptoProviderFactory } from './index.js'
+
+// a real-world request from an account with "qwe123" password
+const fakeAlgo: tl.RawPasswordKdfAlgoSHA256SHA256PBKDF2HMACSHA512iter100000SHA256ModPow = {
+    _: 'passwordKdfAlgoSHA256SHA256PBKDF2HMACSHA512iter100000SHA256ModPow',
+    salt1: hexDecodeToBuffer('9b3accc457c0d5288e8cff31eb21094048bc11902f6614dbb9afb839ee7641c37619537d8ebe749e'),
+    salt2: hexDecodeToBuffer('6c619bb0786dc4ed1bf211d23f6e4065'),
+    g: 3,
+    p: hexDecodeToBuffer(
+        'c71caeb9c6b1c9048e6c522f70f13f73980d40238e3e21c14934d037563d930f' +
+            '48198a0aa7c14058229493d22530f4dbfa336f6e0ac925139543aed44cce7c37' +
+            '20fd51f69458705ac68cd4fe6b6b13abdc9746512969328454f18faf8c595f64' +
+            '2477fe96bb2a941d5bcd1d4ac8cc49880708fa9b378e3c4f3a9060bee67cf9a4' +
+            'a4a695811051907e162753b56b0f6b410dba74d8a84b2a14b3144e0ef1284754' +
+            'fd17ed950d5965b4b9dd46582db1178d169c6bc465b0d6ff9ca3928fef5b9ae4' +
+            'e418fc15e83ebea0f87fa9ff5eed70050ded2849f47bf959d956850ce929851f' +
+            '0d8115f635b105ee2e4e15d04b2454bf6f4fadf034b10403119cd8e3b92fcc5b',
+    ),
+}
+// const fakeRequest: tl.account.RawPassword = {
+//     _: 'account.password',
+//     hasRecovery: false,
+//     hasSecureValues: false,
+//     hasPassword: true,
+//     currentAlgo: fakeAlgo,
+//     srpB: hexDecodeToBuffer(
+//         '1476a7b5991d7f028bbee33b3455cad3f2cd0eb3737409fcce92fa7d4cd5c733' +
+//         'ec6d2cb3454e587d4c17eda2fd7ef9a57327215f38292cc8bd5dc77d3e1d31cd' +
+//         'dae2652f8347c4b0093f7c78242f70e6cc13137ee7acc257a49855a63113db8f' +
+//         '163992b9101551f3b6f7eb5d196cee3647c359553b1bcbe82ba8933c0fb1ac35' +
+//         '0243c535b8e634613e1f626ba8a6d141ef957c859e71a117b557c0298bfbb107' +
+//         'c91f71f5b4275fded58289aa1e87c612f44b7aa0b5e0de7def4458f58db80019' +
+//         'd2e7b181eb66dc270374af2d160dd0c53edd677b2701694d71ea8718c49df6a9' +
+//         'dbe2cbae051ffc1986336cd26f11a8ab426dfe0813d7b3f4eedf4e34182ccc3a',
+//     ),
+//     srpId: Long.fromBits(-2046015018, 875006452),
+//     newAlgo: {
+//         _: 'passwordKdfAlgoSHA256SHA256PBKDF2HMACSHA512iter100000SHA256ModPow',
+//         salt1: hexDecodeToBuffer('9b3accc457c0d528'),
+//         salt2: hexDecodeToBuffer('6c619bb0786dc4ed1bf211d23f6e4065'),
+//         g: 3,
+//         p: hexDecodeToBuffer(
+//             'c71caeb9c6b1c9048e6c522f70f13f73980d40238e3e21c14934d037563d930f' +
+//             '48198a0aa7c14058229493d22530f4dbfa336f6e0ac925139543aed44cce7c37' +
+//             '20fd51f69458705ac68cd4fe6b6b13abdc9746512969328454f18faf8c595f64' +
+//             '2477fe96bb2a941d5bcd1d4ac8cc49880708fa9b378e3c4f3a9060bee67cf9a4' +
+//             'a4a695811051907e162753b56b0f6b410dba74d8a84b2a14b3144e0ef1284754' +
+//             'fd17ed950d5965b4b9dd46582db1178d169c6bc465b0d6ff9ca3928fef5b9ae4' +
+//             'e418fc15e83ebea0f87fa9ff5eed70050ded2849f47bf959d956850ce929851f' +
+//             '0d8115f635b105ee2e4e15d04b2454bf6f4fadf034b10403119cd8e3b92fcc5b',
+//         ),
+//     },
+//     newSecureAlgo: {
+//         _: 'securePasswordKdfAlgoPBKDF2HMACSHA512iter100000',
+//         salt: hexDecodeToBuffer('fdd59abc0bffb24d'),
+//     },
+//     secureRandom: new Uint8Array(), // unused
+// }
+const password = utf8EncodeToBuffer('qwe123')
+
+describe('computePasswordHash', () => {
+    const crypto = defaultCryptoProviderFactory()
+
+    it('should correctly compute password hash as defined by MTProto', async () => {
+        const actual = await computePasswordHash(crypto, password, fakeAlgo.salt1, fakeAlgo.salt2)
+
+        expect(hexEncode(actual)).toEqual('750f1fe282965e63ce17b98427b35549fb864465211840f6a7c1f2fb657cc33b')
+    })
+
+    // todo: computeNewPasswordHash and computeSrpParams both require predictable random
+})
diff --git a/packages/core/src/utils/deque.test.ts b/packages/core/src/utils/deque.test.ts
new file mode 100644
index 00000000..62be647f
--- /dev/null
+++ b/packages/core/src/utils/deque.test.ts
@@ -0,0 +1,173 @@
+import { describe, expect, it } from 'vitest'
+
+import { Deque } from './deque.js'
+
+describe('Deque', () => {
+    function setupWrapping() {
+        const d = new Deque<number>(Infinity, /* capacity: */ 8)
+
+        for (let i = 1; i <= 7; i++) {
+            d.pushBack(i)
+        }
+
+        // [1, 2, 3, 4, 5, 6, 7, _]
+
+        d.popFront()
+        d.popFront()
+        d.popFront()
+
+        // [_, _, _, 4, 5, 6, 7, _]
+
+        d.pushBack(8)
+        d.pushBack(9)
+        d.pushBack(10)
+
+        // [9, 10, _, 4, 5, 6, 7, 8]
+        return d
+    }
+
+    it('should push items to the end correctly', () => {
+        const d = new Deque<number>()
+
+        d.pushBack(1)
+        d.pushBack(2)
+        d.pushBack(3)
+
+        expect(d.toArray()).eql([1, 2, 3])
+        expect([...d.iter()]).eql([1, 2, 3])
+    })
+
+    it('should push items to the start correctly', () => {
+        const d = new Deque<number>()
+
+        d.pushFront(1)
+        d.pushFront(2)
+        d.pushFront(3)
+
+        expect(d.toArray()).eql([3, 2, 1])
+    })
+
+    it('should pop items from the end correctly', () => {
+        const d = new Deque<number>()
+
+        d.pushBack(1)
+        d.pushBack(2)
+        d.pushBack(3)
+
+        expect(d.popBack()).eql(3)
+        expect(d.popBack()).eql(2)
+        expect(d.popBack()).eql(1)
+    })
+
+    it('should pop items from the start correctly', () => {
+        const d = new Deque<number>()
+
+        d.pushFront(1)
+        d.pushFront(2)
+        d.pushFront(3)
+
+        expect(d.popFront()).eql(3)
+        expect(d.popFront()).eql(2)
+        expect(d.popFront()).eql(1)
+    })
+
+    it('should return the correct length', () => {
+        const d = new Deque<number>()
+
+        d.pushBack(1)
+        d.pushBack(2)
+        d.pushBack(3)
+
+        expect(d.length).eql(3)
+    })
+
+    it('accessors should correctly wrap around', () => {
+        const d = setupWrapping()
+
+        expect(d.toArray()).eql([4, 5, 6, 7, 8, 9, 10])
+        expect([...d.iter()]).eql([4, 5, 6, 7, 8, 9, 10])
+        expect(d.at(6)).eql(10)
+    })
+
+    it('should handle maxLength by removing items from the other end', () => {
+        const d = new Deque<number>(4)
+
+        d.pushBack(1)
+        d.pushBack(2)
+        d.pushBack(3)
+        d.pushBack(4)
+
+        d.pushBack(5)
+        expect(d.toArray()).eql([2, 3, 4, 5])
+
+        d.pushFront(6)
+        expect(d.toArray()).eql([6, 2, 3, 4])
+    })
+
+    it('should correctly resize', () => {
+        const d = new Deque<number>(Infinity, /* capacity: */ 8)
+
+        for (let i = 0; i <= 16; i++) {
+            d.pushBack(i)
+        }
+
+        const expected = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]
+
+        expect(d.length).eql(17)
+        expect(d.toArray()).eql(expected)
+        expect([...d.iter()]).eql(expected)
+        expect(d.at(16)).eql(16)
+    })
+
+    it('should correctly remove items', () => {
+        const d = new Deque<number>(Infinity, /* capacity: */ 16)
+
+        d.pushBack(1)
+        d.pushBack(2)
+        d.pushBack(3)
+        d.pushBack(4)
+        d.pushBack(5)
+
+        d.remove(1)
+        d.remove(4)
+
+        expect(d.toArray()).eql([2, 3, 5])
+    })
+
+    it('should correctly remove items by predicate (the first matched)', () => {
+        const d = new Deque<number>(Infinity, /* capacity: */ 4)
+
+        d.pushBack(1)
+        d.pushBack(2)
+        d.pushBack(3)
+        d.pushBack(4)
+        d.pushBack(5)
+
+        d.removeBy((it) => it >= 2)
+
+        expect(d.toArray()).eql([1, 3, 4, 5])
+    })
+
+    it('should correctly peek at edges', () => {
+        const d = new Deque<number>()
+
+        d.pushBack(1)
+        d.pushBack(2)
+
+        expect(d.peekFront()).eql(1)
+        expect(d.peekBack()).eql(2)
+    })
+
+    it('should correctly clear', () => {
+        const d = new Deque<number>()
+
+        d.pushBack(1)
+        d.pushBack(2)
+
+        d.clear()
+
+        expect(d.length).eql(0)
+        expect(d.toArray()).eql([])
+        expect([...d.iter()]).eql([])
+    })
+})
diff --git a/packages/core/src/utils/deque.ts b/packages/core/src/utils/deque.ts
index 99e2262f..10c8205f 100644
--- a/packages/core/src/utils/deque.ts
+++ b/packages/core/src/utils/deque.ts
@@ -24,14 +24,16 @@ export class Deque<T> {
     protected _capacity: number
 
     constructor(
-        minCapacity = MIN_INITIAL_CAPACITY,
         readonly maxLength = Infinity,
+        minCapacity = maxLength === Infinity ? MIN_INITIAL_CAPACITY : maxLength,
     ) {
         let capacity = minCapacity
 
-        if (capacity >= MIN_INITIAL_CAPACITY) {
+        if (capacity < MIN_INITIAL_CAPACITY) {
+            capacity = MIN_INITIAL_CAPACITY
+        }
+        if (capacity !== MIN_INITIAL_CAPACITY) {
             // Find the best power of two to hold elements.
-            // >= because array can't be full
             capacity |= capacity >>> 1
             capacity |= capacity >>> 2
             capacity |= capacity >>> 4
@@ -135,6 +137,8 @@ export class Deque<T> {
 
     toArray(): T[] {
         const sz = this.length
+        if (sz === 0) return []
+
         const arr = new Array(sz)
 
         if (this._head < this._tail) {
@@ -220,6 +224,7 @@ export class Deque<T> {
 
     *iter(): IterableIterator<T> {
         const sz = this.length
+        if (sz === 0) return
 
         if (this._head < this._tail) {
             // head to tail
diff --git a/packages/core/src/utils/flood-control.ts b/packages/core/src/utils/flood-control.ts
deleted file mode 100644
index 1a66ab85..00000000
--- a/packages/core/src/utils/flood-control.ts
+++ /dev/null
@@ -1,74 +0,0 @@
-// based on https://github.dev/tdlib/td/blob/master/tdutils/td/utils/FloodControlStrict.h
-
-interface FloodControlLimit {
-    duration: number
-    count: number
-    pos: number
-}
-
-/**
- * Flood limiter, based on TDlib
- */
-export class FloodControl {
-    private _wakeupAt = 1
-    private _withoutUpdate = 0
-    private _events: number[] = []
-    // pair: duration, count
-    private _limits: FloodControlLimit[] = []
-
-    // no more than count in each duration
-    addLimit(duration: number, count: number): void {
-        this._limits.push({ duration, count, pos: 0 })
-        this._withoutUpdate = 0
-    }
-
-    addEvent(now: number): void {
-        this._events.push(now)
-
-        if (this._withoutUpdate > 0) {
-            this._withoutUpdate -= 1
-        } else {
-            this._update(now)
-        }
-    }
-
-    clear(): void {
-        this._events.length = 0
-        this._withoutUpdate = 0
-        this._wakeupAt = 1
-        this._limits.forEach((limit) => (limit.pos = 0))
-    }
-
-    get wakeupAt(): number {
-        return this._wakeupAt
-    }
-
-    private _update(now: number): void {
-        let minPos = this._events.length
-        this._withoutUpdate = Infinity
-
-        this._limits.forEach((limit) => {
-            if (limit.count < this._events.length - limit.pos) {
-                limit.pos = this._events.length - limit.count
-            }
-
-            while (limit.pos < this._events.length && this._events[limit.pos] + limit.duration < now) {
-                limit.pos += 1
-            }
-
-            if (limit.count + limit.pos < this._events.length) {
-                this._wakeupAt = Math.max(this._wakeupAt, this._events[limit.pos] + limit.duration)
-                this._withoutUpdate = 0
-            } else {
-                this._withoutUpdate = Math.min(this._withoutUpdate, limit.count + limit.pos - this._events.length - 1)
-            }
-
-            minPos = Math.min(minPos, limit.pos)
-        })
-
-        if (minPos * 2 > this._events.length) {
-            this._limits.forEach((limit) => (limit.pos -= minPos))
-            this._events.splice(0, minPos)
-        }
-    }
-}
diff --git a/packages/core/src/utils/function-utils.test.ts b/packages/core/src/utils/function-utils.test.ts
new file mode 100644
index 00000000..0492d8fd
--- /dev/null
+++ b/packages/core/src/utils/function-utils.test.ts
@@ -0,0 +1,27 @@
+import { describe, expect, it } from 'vitest'
+
+import { ConditionVariable } from './condition-variable.js'
+import { throttle } from './function-utils.js'
+
+describe('throttle', () => {
+    it('should throttle', async () => {
+        const cv = new ConditionVariable()
+        let count = 0
+
+        const func = () => {
+            count++
+            cv.notify()
+        }
+
+        const throttled = throttle(func, 10)
+
+        throttled()
+        throttled()
+        throttled()
+        throttled()
+
+        await cv.wait()
+
+        expect(count).eq(1)
+    })
+})
diff --git a/packages/core/src/utils/index.ts b/packages/core/src/utils/index.ts
index 77254166..3cffd965 100644
--- a/packages/core/src/utils/index.ts
+++ b/packages/core/src/utils/index.ts
@@ -7,7 +7,6 @@ export * from './crypto/index.js'
 export * from './default-dcs.js'
 export * from './deque.js'
 export * from './early-timer.js'
-export * from './flood-control.js'
 export * from './function-utils.js'
 export * from './linked-list.js'
 export * from './links/index.js'
diff --git a/packages/core/src/utils/linked-list.test.ts b/packages/core/src/utils/linked-list.test.ts
new file mode 100644
index 00000000..378ed14f
--- /dev/null
+++ b/packages/core/src/utils/linked-list.test.ts
@@ -0,0 +1,47 @@
+import { describe, expect, it } from 'vitest'
+
+import { SortedLinkedList } from './linked-list.js'
+
+describe('SortedLinkedList', () => {
+    const ascendingComparator = (a: number, b: number) => a - b
+
+    it('should add items in the correct order', () => {
+        const list = new SortedLinkedList(ascendingComparator)
+
+        list.add(3)
+        list.add(1)
+        list.add(2)
+
+        expect(list.popFront()).eq(1)
+        expect(list.popFront()).eq(2)
+        expect(list.popFront()).eq(3)
+    })
+
+    it('should allow deleting nodes using _remove', () => {
+        const list = new SortedLinkedList(ascendingComparator)
+
+        list.add(3)
+        list.add(1)
+        list.add(2)
+
+        const node = list._first!.n!
+
+        list._remove(node)
+
+        expect(list.popFront()).eq(1)
+        expect(list.popFront()).eq(3)
+    })
+
+    it('should clear', () => {
+        const list = new SortedLinkedList(ascendingComparator)
+
+        list.add(3)
+        list.add(1)
+        list.add(2)
+
+        list.clear()
+
+        expect(list.length).eq(0)
+        expect(list.popFront()).eq(undefined)
+    })
+})
diff --git a/packages/core/src/utils/logger.test.ts b/packages/core/src/utils/logger.test.ts
new file mode 100644
index 00000000..c1a4813e
--- /dev/null
+++ b/packages/core/src/utils/logger.test.ts
@@ -0,0 +1,173 @@
+import Long from 'long'
+import { describe, expect, it, vi } from 'vitest'
+
+import { LogManager } from './logger.js'
+
+describe('logger', () => {
+    const createManager = () => {
+        const mgr = new LogManager()
+
+        const spy = vi.fn<Parameters<typeof mgr.handler>>()
+        mgr.handler = spy
+
+        return [mgr, spy] as const
+    }
+
+    it('should only log messages below the set level', () => {
+        const [mgr, spy] = createManager()
+
+        mgr.level = LogManager.INFO
+        mgr.error('test error')
+        mgr.warn('test warn')
+        mgr.info('test info')
+        mgr.debug('test debug')
+        mgr.verbose('test verbose')
+
+        expect(spy).toHaveBeenCalledTimes(3)
+        expect(spy).toHaveBeenCalledWith(3, 1, 'base', 'test error', [])
+        expect(spy).toHaveBeenCalledWith(3, 2, 'base', 'test warn', [])
+        expect(spy).toHaveBeenCalledWith(3, 3, 'base', 'test info', [])
+    })
+
+    it('should create child loggers', () => {
+        const [mgr, spy] = createManager()
+
+        mgr.create('child').info('test info')
+
+        expect(spy).toHaveBeenCalledWith(0, 3, 'child', 'test info', [])
+    })
+
+    it('should apply filtering by tags', () => {
+        const [mgr, spy] = createManager()
+
+        const test1 = mgr.create('test1')
+        const test2 = mgr.create('test2')
+
+        mgr.filter((tag) => tag === 'test1')
+
+        test1.info('test1 info')
+        test2.info('test2 info')
+
+        expect(spy).toHaveBeenCalledTimes(1)
+        expect(spy).toHaveBeenCalledWith(5, 3, 'test1', 'test1 info', [])
+    })
+
+    it('should recursively add prefixes', () => {
+        const [mgr, spy] = createManager()
+
+        const test = mgr.create('test1')
+        const test2 = test.create('test2')
+
+        test.prefix = '[TEST] '
+        test2.prefix = '[TEST2] '
+
+        test2.create('test3').info('test info')
+
+        expect(spy).toHaveBeenCalledWith(1, 3, 'test3', '[TEST] [TEST2] test info', [])
+    })
+
+    describe('formatting', () => {
+        it('should pass generic format strings through', () => {
+            const [mgr, spy] = createManager()
+
+            mgr.info('test %s', 'info')
+
+            expect(spy).toHaveBeenCalledWith(3, 3, 'base', 'test %s', ['info'])
+        })
+
+        describe('%h', () => {
+            it('should format buffers as hex strings', () => {
+                const [mgr, spy] = createManager()
+
+                mgr.info('test %h', new Uint8Array([0x01, 0x02, 0x03]))
+
+                expect(spy).toHaveBeenCalledWith(3, 3, 'base', 'test 010203', [])
+            })
+
+            it('should format numbers as hex', () => {
+                const [mgr, spy] = createManager()
+
+                mgr.info('test %h', 0x010203)
+                mgr.info('test bigint %h', 0x010203n)
+
+                expect(spy).toHaveBeenCalledWith(3, 3, 'base', 'test 10203', [])
+                expect(spy).toHaveBeenCalledWith(3, 3, 'base', 'test bigint 10203', [])
+            })
+
+            it('should format everything else as normal strings', () => {
+                const [mgr, spy] = createManager()
+
+                mgr.info('test %h', {})
+
+                expect(spy).toHaveBeenCalledWith(3, 3, 'base', 'test [object Object]', [])
+            })
+        })
+
+        describe('%b', () => {
+            it('should format booleans as strings', () => {
+                const [mgr, spy] = createManager()
+
+                mgr.info('test %b', true)
+
+                expect(spy).toHaveBeenCalledWith(3, 3, 'base', 'test true', [])
+            })
+
+            it('should coerce everything to boolean', () => {
+                const [mgr, spy] = createManager()
+
+                mgr.info('test %b', 123)
+
+                expect(spy).toHaveBeenCalledWith(3, 3, 'base', 'test true', [])
+            })
+        })
+
+        describe('%j', () => {
+            it('should format objects as JSON', () => {
+                const [mgr, spy] = createManager()
+
+                mgr.info('test %j', { a: 1 })
+
+                expect(spy).toHaveBeenCalledWith(3, 3, 'base', 'test {"a":1}', [])
+            })
+
+            it('should format buffers inside as hex strings', () => {
+                const [mgr, spy] = createManager()
+
+                // eslint-disable-next-line no-restricted-globals
+                mgr.info('test %j', { a: Buffer.from([1, 2, 3]) })
+                mgr.info('test Uint8Array %j', { a: new Uint8Array([1, 2, 3]) })
+
+                expect(spy).toHaveBeenCalledWith(3, 3, 'base', 'test {"a":"010203"}', [])
+                expect(spy).toHaveBeenCalledWith(3, 3, 'base', 'test Uint8Array {"a":"010203"}', [])
+            })
+
+            it('should trim long buffers', () => {
+                const [mgr, spy] = createManager()
+
+                const _150hexZeros = Array(150).fill('00').join('')
+
+                mgr.info('test %j', { a: new Uint8Array(300) })
+
+                expect(spy).toHaveBeenCalledWith(3, 3, 'base', `test {"a":"${_150hexZeros}..."}`, [])
+            })
+
+            it('should have %J variation accepting iterators', () => {
+                const [mgr, spy] = createManager()
+
+                mgr.info('test %J', new Set([1, 2, 3]))
+
+                expect(spy).toHaveBeenCalledWith(3, 3, 'base', 'test [1,2,3]', [])
+            })
+        })
+
+        describe('%l', () => {
+            it('should format Longs as strings', () => {
+                const [mgr, spy] = createManager()
+
+                mgr.info('test %l', Long.fromInt(123))
+
+                expect(spy).toHaveBeenCalledWith(3, 3, 'base', 'test 123', [])
+            })
+        })
+    })
+})
diff --git a/packages/core/src/utils/logger.ts b/packages/core/src/utils/logger.ts
index 431855d9..b42fb78a 100644
--- a/packages/core/src/utils/logger.ts
+++ b/packages/core/src/utils/logger.ts
@@ -4,6 +4,7 @@ import { _defaultLoggingHandler } from './platform/logging.js'
 
 let defaultLogLevel = 3
 
+/* c8 ignore start */
 if (typeof process !== 'undefined') {
     const envLogLevel = parseInt(process.env.MTCUTE_LOG_LEVEL ?? '')
 
@@ -17,6 +18,7 @@ if (typeof process !== 'undefined') {
         defaultLogLevel = localLogLevel
     }
 }
+/* c8 ignore end */
 
 const FORMATTER_RE = /%[a-zA-Z]/g
 
@@ -79,7 +81,7 @@ export class Logger {
 
                     if (m === '%h') {
                         if (ArrayBuffer.isView(val)) return hexEncode(val as Uint8Array)
-                        if (typeof val === 'number') return val.toString(16)
+                        if (typeof val === 'number' || typeof val === 'bigint') return val.toString(16)
 
                         return String(val)
                     }
@@ -165,10 +167,6 @@ export class LogManager extends Logger {
     level = defaultLogLevel
     handler = _defaultLoggingHandler
 
-    disable(): void {
-        this.level = 0
-    }
-
     /**
      * Create a {@link Logger} with the given tag
      *
diff --git a/packages/core/src/utils/long-utils.test.ts b/packages/core/src/utils/long-utils.test.ts
new file mode 100644
index 00000000..f5d0784d
--- /dev/null
+++ b/packages/core/src/utils/long-utils.test.ts
@@ -0,0 +1,221 @@
+import Long from 'long'
+import { describe, expect, it } from 'vitest'
+
+import {
+    longFromBuffer,
+    longFromFastString,
+    LongMap,
+    LongSet,
+    longToFastString,
+    randomLong,
+    removeFromLongArray,
+} from './long-utils.js'
+
+describe('randomLong', () => {
+    it('should return a random Long', () => {
+        const long = randomLong()
+        const long2 = randomLong()
+
+        expect(long).toBeInstanceOf(Long)
+        expect(long.eq(long2)).toBeFalsy()
+    })
+})
+
+describe('longFromBuffer', () => {
+    it('should correctly read LE longs', () => {
+        expect(longFromBuffer(new Uint8Array([0, 0, 0, 0, 0, 0, 0, 0]))).toEqual(Long.fromInt(0))
+        expect(longFromBuffer(new Uint8Array([1, 2, 3, 4, 5, 6, 7, 8]))).toEqual(Long.fromBits(0x04030201, 0x08070605))
+    })
+
+    it('should correctly read BE longs', () => {
+        expect(longFromBuffer(new Uint8Array([0, 0, 0, 0, 0, 0, 0, 0]), false, false)).toEqual(Long.fromInt(0))
+        expect(longFromBuffer(new Uint8Array([8, 7, 6, 5, 4, 3, 2, 1]), false, false)).toEqual(
+            Long.fromBits(0x04030201, 0x08070605),
+        )
+    })
+})
+
+describe('removeFromLongArray', () => {
+    it('should remove a Long from an array', () => {
+        const arr = [Long.fromInt(1), Long.fromInt(2), Long.fromInt(3)]
+
+        expect(removeFromLongArray(arr, Long.fromInt(2))).toBeTruthy()
+        expect(arr).toEqual([Long.fromInt(1), Long.fromInt(3)])
+    })
+
+    it('should return false if the Long was not found', () => {
+        const arr = [Long.fromInt(1), Long.fromInt(2), Long.fromInt(3)]
+
+        expect(removeFromLongArray(arr, Long.fromInt(4))).toBeFalsy()
+        expect(arr).toEqual([Long.fromInt(1), Long.fromInt(2), Long.fromInt(3)])
+    })
+
+    it('should only remove one matching element', () => {
+        const arr = [Long.fromInt(1), Long.fromInt(2), Long.fromInt(2), Long.fromInt(3)]
+
+        expect(removeFromLongArray(arr, Long.fromInt(2))).toBeTruthy()
+        expect(arr).toEqual([Long.fromInt(1), Long.fromInt(2), Long.fromInt(3)])
+    })
+})
+
+describe('longToFastString', () => {
+    it('should correctly serialize a Long', () => {
+        expect(longToFastString(Long.fromInt(0))).toEqual('0|0')
+        expect(longToFastString(Long.fromBits(123, 456))).toEqual('123|456')
+    })
+
+    it('should work with negative numbers', () => {
+        expect(longToFastString(Long.fromInt(-1))).toEqual('-1|-1')
+        expect(longToFastString(Long.fromBits(-123, -456))).toEqual('-123|-456')
+    })
+})
+
+describe('longFromFastString', () => {
+    it('should correctly deserialize a Long', () => {
+        expect(longFromFastString('0|0')).toEqual(Long.fromInt(0))
+        expect(longFromFastString('123|456')).toEqual(Long.fromBits(123, 456))
+    })
+
+    it('should work with negative numbers', () => {
+        expect(longFromFastString('-1|-1')).toEqual(Long.fromInt(-1))
+        expect(longFromFastString('-123|-456')).toEqual(Long.fromBits(-123, -456))
+    })
+
+    it('should throw on invalid strings', () => {
+        expect(() => longFromFastString('0')).toThrow()
+        expect(() => longFromFastString('0|0|0')).toThrow()
+        expect(() => longFromFastString('abc|def')).toThrow()
+    })
+})
+
+describe('LongMap', () => {
+    it('should set and get values', () => {
+        const map = new LongMap<string>()
+
+        map.set(Long.fromInt(123), 'test')
+
+        expect(map.get(Long.fromInt(123))).toEqual('test')
+    })
+
+    it('should return undefined for non-existing keys', () => {
+        const map = new LongMap<string>()
+
+        expect(map.get(Long.fromInt(123))).toEqual(undefined)
+    })
+
+    it('should check for existing keys', () => {
+        const map = new LongMap<string>()
+
+        map.set(Long.fromInt(123), 'test')
+
+        expect(map.has(Long.fromInt(123))).toBeTruthy()
+        expect(map.has(Long.fromInt(456))).toBeFalsy()
+    })
+
+    it('should delete keys', () => {
+        const map = new LongMap<string>()
+
+        map.set(Long.fromInt(123), 'test')
+        map.delete(Long.fromInt(123))
+
+        expect(map.has(Long.fromInt(123))).toBeFalsy()
+    })
+
+    it('should iterate over keys', () => {
+        const map = new LongMap<string>()
+
+        map.set(Long.fromInt(123), 'test')
+        map.set(Long.fromInt(456), 'test2')
+
+        expect([...map.keys()]).toEqual([Long.fromInt(123), Long.fromInt(456)])
+    })
+
+    it('should iterate over values', () => {
+        const map = new LongMap<string>()
+
+        map.set(Long.fromInt(123), 'test')
+        map.set(Long.fromInt(456), 'test2')
+
+        expect([...map.values()]).toEqual(['test', 'test2'])
+    })
+
+    it('should clear', () => {
+        const map = new LongMap<string>()
+
+        map.set(Long.fromInt(123), 'test')
+        map.set(Long.fromInt(456), 'test2')
+
+        map.clear()
+
+        expect(map.has(Long.fromInt(123))).toBeFalsy()
+        expect(map.has(Long.fromInt(456))).toBeFalsy()
+    })
+
+    it('should return the size', () => {
+        const map = new LongMap<string>()
+
+        map.set(Long.fromInt(123), 'test')
+        map.set(Long.fromInt(456), 'test2')
+
+        expect(map.size()).toEqual(2)
+    })
+})
+
+describe('LongSet', () => {
+    it('should add and check for values', () => {
+        const set = new LongSet()
+
+        set.add(Long.fromInt(123))
+
+        expect(set.has(Long.fromInt(123))).toBeTruthy()
+    })
+
+    it('should remove values', () => {
+        const set = new LongSet()
+
+        set.add(Long.fromInt(123))
+        set.add(Long.fromInt(456))
+        set.delete(Long.fromInt(123))
+
+        expect(set.has(Long.fromInt(123))).toBeFalsy()
+    })
+
+    it('should return the size', () => {
+        const set = new LongSet()
+
+        set.add(Long.fromInt(123))
+        set.add(Long.fromInt(456))
+
+        expect(set.size).toEqual(2)
+    })
+
+    it('should clear', () => {
+        const set = new LongSet()
+
+        set.add(Long.fromInt(123))
+        set.add(Long.fromInt(456))
+
+        set.clear()
+
+        expect(set.has(Long.fromInt(123))).toBeFalsy()
+        expect(set.has(Long.fromInt(456))).toBeFalsy()
+    })
+
+    it('should return the size', () => {
+        const set = new LongSet()
+
+        set.add(Long.fromInt(123))
+        set.add(Long.fromInt(456))
+
+        expect(set.size).toEqual(2)
+    })
+
+    it('should convert to array', () => {
+        const set = new LongSet()
+
+        set.add(Long.fromInt(123))
+        set.add(Long.fromInt(456))
+
+        expect(set.toArray()).toEqual([Long.fromInt(123), Long.fromInt(456)])
+    })
+})
diff --git a/packages/core/src/utils/lru-map.test.ts b/packages/core/src/utils/lru-map.test.ts
index 778cfddd..8a8859b7 100644
--- a/packages/core/src/utils/lru-map.test.ts
+++ b/packages/core/src/utils/lru-map.test.ts
@@ -3,42 +3,111 @@ import { describe, expect, it } from 'vitest'
 import { LruMap } from './lru-map.js'
 
 describe('LruMap', () => {
-    it('Map backend', () => {
+    it('should maintain maximum size by removing oldest added', () => {
         const lru = new LruMap<string, number>(2)
 
         lru.set('first', 1)
-        expect(lru.has('first')).true
-        expect(lru.has('second')).false
-        expect(lru.get('first')).eq(1)
-
-        lru.set('first', 42)
-        expect(lru.has('first')).true
-        expect(lru.has('second')).false
-        expect(lru.get('first')).eq(42)
-
         lru.set('second', 2)
-        expect(lru.has('first')).true
-        expect(lru.has('second')).true
-        expect(lru.get('first')).eq(42)
-        expect(lru.get('second')).eq(2)
-
         lru.set('third', 3)
-        expect(lru.has('first')).false
-        expect(lru.has('second')).true
-        expect(lru.has('third')).true
-        expect(lru.get('first')).eq(undefined)
-        expect(lru.get('second')).eq(2)
-        expect(lru.get('third')).eq(3)
 
-        lru.get('second') // update lru so that last = third
-        lru.set('fourth', 4)
-        expect(lru.has('first')).false
-        expect(lru.has('second')).true
-        expect(lru.has('third')).false
-        expect(lru.has('fourth')).true
-        expect(lru.get('first')).eq(undefined)
-        expect(lru.get('second')).eq(2)
-        expect(lru.get('third')).eq(undefined)
-        expect(lru.get('fourth')).eq(4)
+        expect(lru.has('first')).toBeFalsy()
     })
+
+    it('should update the last added item', () => {
+        const lru = new LruMap<string, number>(2)
+
+        lru.set('first', 1)
+        lru.set('second', 2)
+        lru.set('first', 42)
+        lru.set('third', 3)
+
+        expect(lru.get('first')).toEqual(42)
+        expect(lru.has('second')).toBeFalsy()
+    })
+
+    it('should update the last used item', () => {
+        const lru = new LruMap<string, number>(2)
+
+        lru.set('first', 1)
+        lru.set('second', 2)
+        lru.get('first')
+        lru.set('third', 3)
+        lru.get('third')
+
+        expect(lru.get('first')).toEqual(1)
+        expect(lru.has('second')).toBeFalsy()
+    })
+
+    it('should allow deleting items', () => {
+        const lru = new LruMap<string, number>(2)
+
+        lru.set('first', 1)
+        lru.set('second', 2)
+        lru.set('third', 3) // first is now deleted
+        lru.delete('second')
+
+        expect(lru.has('first')).toBeFalsy()
+        expect(lru.has('second')).toBeFalsy()
+        expect(lru.has('third')).toBeTruthy()
+    })
+
+    it('should handle deleting all items', () => {
+        const lru = new LruMap<string, number>(2)
+
+        lru.set('first', 1)
+        lru.set('second', 2)
+        lru.delete('second')
+        lru.delete('first')
+
+        expect(lru.has('first')).toBeFalsy()
+        expect(lru.has('second')).toBeFalsy()
+    })
+
+    it('should return undefined for non-existing items', () => {
+        const lru = new LruMap<string, number>(2)
+
+        lru.set('first', 1)
+        lru.set('second', 2)
+
+        expect(lru.get('third')).toEqual(undefined)
+    })
+
+    // it('Map backend', () => {
+    //     const lru = new LruMap<string, number>(2)
+    //
+    //     lru.set('first', 1)
+    //     expect(lru.has('first')).true
+    //     expect(lru.has('second')).false
+    //     expect(lru.get('first')).eq(1)
+    //
+    //     lru.set('first', 42)
+    //     expect(lru.has('first')).true
+    //     expect(lru.has('second')).false
+    //     expect(lru.get('first')).eq(42)
+    //
+    //     lru.set('second', 2)
+    //     expect(lru.has('first')).true
+    //     expect(lru.has('second')).true
+    //     expect(lru.get('first')).eq(42)
+    //     expect(lru.get('second')).eq(2)
+    //
+    //     lru.set('third', 3)
+    //     expect(lru.has('first')).false
+    //     expect(lru.has('second')).true
+    //     expect(lru.has('third')).true
+    //     expect(lru.get('first')).eq(undefined)
+    //     expect(lru.get('second')).eq(2)
+    //     expect(lru.get('third')).eq(3)
+    //
+    //     lru.get('second') // update lru so that last = third
+    //     lru.set('fourth', 4)
+    //     expect(lru.has('first')).false
+    //     expect(lru.has('second')).true
+    //     expect(lru.has('third')).false
+    //     expect(lru.has('fourth')).true
+    //     expect(lru.get('first')).eq(undefined)
+    //     expect(lru.get('second')).eq(2)
+    //     expect(lru.get('third')).eq(undefined)
+    //     expect(lru.get('fourth')).eq(4)
+    // })
 })
diff --git a/packages/core/src/utils/peer-utils.test.ts b/packages/core/src/utils/peer-utils.test.ts
new file mode 100644
index 00000000..5816ad22
--- /dev/null
+++ b/packages/core/src/utils/peer-utils.test.ts
@@ -0,0 +1,153 @@
+import Long from 'long'
+import { describe, expect, it } from 'vitest'
+
+import { createStub } from '@mtcute/test'
+
+import {
+    getAllPeersFrom,
+    getBarePeerId,
+    getBasicPeerType,
+    getMarkedPeerId,
+    markedPeerIdToBare,
+    toggleChannelIdMark,
+} from './peer-utils.js'
+
+const SOME_CHANNEL_ID = 1183945448
+const SOME_CHANNEL_ID_MARKED = -1001183945448
+
+describe('toggleChannelIdMark', () => {
+    it('should turn marked channel id into bare', () => {
+        expect(toggleChannelIdMark(SOME_CHANNEL_ID_MARKED)).toEqual(SOME_CHANNEL_ID)
+    })
+
+    it('should turn bare channel id into marked', () => {
+        expect(toggleChannelIdMark(SOME_CHANNEL_ID)).toEqual(SOME_CHANNEL_ID_MARKED)
+    })
+})
+
+describe('getBarePeerId', () => {
+    it('should return bare peer id from Peer', () => {
+        expect(getBarePeerId({ _: 'peerUser', userId: 123 })).toEqual(123)
+        expect(getBarePeerId({ _: 'peerChat', chatId: 456 })).toEqual(456)
+        expect(getBarePeerId({ _: 'peerChannel', channelId: 789 })).toEqual(789)
+    })
+})
+
+describe('getMarkedPeerId', () => {
+    it('should return marked peer id from bare and type', () => {
+        expect(getMarkedPeerId(123, 'user')).toEqual(123)
+        expect(getMarkedPeerId(456, 'chat')).toEqual(-456)
+        expect(getMarkedPeerId(SOME_CHANNEL_ID, 'channel')).toEqual(SOME_CHANNEL_ID_MARKED)
+    })
+
+    it('should throw on invalid type', () => {
+        // eslint-disable-next-line
+        expect(() => getMarkedPeerId(123, 'invalid' as any)).toThrow()
+    })
+
+    it('should return marked peer id from Peer', () => {
+        expect(getMarkedPeerId({ _: 'peerUser', userId: 123 })).toEqual(123)
+        expect(getMarkedPeerId({ _: 'peerChat', chatId: 456 })).toEqual(-456)
+        expect(getMarkedPeerId({ _: 'peerChannel', channelId: SOME_CHANNEL_ID })).toEqual(SOME_CHANNEL_ID_MARKED)
+    })
+
+    it('should return marked peer id from Input*', () => {
+        expect(getMarkedPeerId({ _: 'inputPeerUser', userId: 123, accessHash: Long.ZERO })).toEqual(123)
+        expect(getMarkedPeerId({ _: 'inputUser', userId: 123, accessHash: Long.ZERO })).toEqual(123)
+        expect(getMarkedPeerId({ _: 'inputPeerChat', chatId: 456 })).toEqual(-456)
+        expect(getMarkedPeerId({ _: 'inputPeerChannel', channelId: SOME_CHANNEL_ID, accessHash: Long.ZERO })).toEqual(
+            SOME_CHANNEL_ID_MARKED,
+        )
+        expect(getMarkedPeerId({ _: 'inputChannel', channelId: SOME_CHANNEL_ID, accessHash: Long.ZERO })).toEqual(
+            SOME_CHANNEL_ID_MARKED,
+        )
+    })
+
+    it('should throw if peer does not have id', () => {
+        expect(() => getMarkedPeerId({ _: 'inputPeerSelf' })).toThrow()
+    })
+})
+
+describe('getBasicPeerType', () => {
+    it('should return basic peer type from Peer', () => {
+        expect(getBasicPeerType({ _: 'peerUser', userId: 123 })).toEqual('user')
+        expect(getBasicPeerType({ _: 'peerChat', chatId: 456 })).toEqual('chat')
+        expect(getBasicPeerType({ _: 'peerChannel', channelId: SOME_CHANNEL_ID })).toEqual('channel')
+    })
+
+    it('should return basic peer type from marked id', () => {
+        expect(getBasicPeerType(123)).toEqual('user')
+        expect(getBasicPeerType(-456)).toEqual('chat')
+        expect(getBasicPeerType(SOME_CHANNEL_ID_MARKED)).toEqual('channel')
+    })
+
+    it('should throw for invalid marked ids', () => {
+        expect(() => getBasicPeerType(0)).toThrow('Invalid marked peer id')
+
+        // secret chats are not supported yet
+        expect(() => getBasicPeerType(-1997852516400)).toThrow('Secret chats are not supported')
+    })
+})
+
+describe('markedPeerIdToBare', () => {
+    it('should return bare peer id from marked id', () => {
+        expect(markedPeerIdToBare(123)).toEqual(123)
+        expect(markedPeerIdToBare(-456)).toEqual(456)
+        expect(markedPeerIdToBare(SOME_CHANNEL_ID_MARKED)).toEqual(SOME_CHANNEL_ID)
+    })
+})
+
+describe('getAllPeersFrom', () => {
+    const stubUser1 = createStub('user', { id: 123 })
+    const stubUser2 = createStub('user', { id: 456 })
+    const stubChat = createStub('chat', { id: 789 })
+    const stubChannel = createStub('channel', { id: 101112 })
+
+    /* eslint-disable @typescript-eslint/no-explicit-any, @typescript-eslint/no-unsafe-argument */
+    it('should find all peers from objects containing users/chats fields', () => {
+        expect([...getAllPeersFrom({ users: [], chats: [] } as any)]).toEqual([])
+        expect([
+            ...getAllPeersFrom({
+                users: [stubUser1, stubUser2],
+                chats: [stubChat, stubChannel],
+            } as any),
+        ]).toEqual([stubUser1, stubUser2, stubChat, stubChannel])
+    })
+
+    it('should extract peers from objects containing user/chat fields', () => {
+        expect([
+            ...getAllPeersFrom({
+                user: stubUser2,
+                chat: stubChat,
+                channel: stubChannel,
+            } as any),
+        ]).toEqual([stubUser2, stubChat, stubChannel])
+    })
+
+    it('should work for arrays', () => {
+        expect([...getAllPeersFrom([{ user: stubUser1 }, { user: stubUser2 }] as any)]).toEqual([stubUser1, stubUser2])
+    })
+
+    it('should work for peer objects directly', () => {
+        expect([...getAllPeersFrom(stubUser1)]).toEqual([stubUser1])
+    })
+
+    it('should ignore *Empty', () => {
+        expect([
+            ...getAllPeersFrom({
+                users: [createStub('userEmpty')],
+                chats: [createStub('chatEmpty')],
+            } as any),
+        ]).toEqual([])
+        expect([...getAllPeersFrom({ user: createStub('userEmpty'), chat: createStub('chatEmpty') } as any)]).toEqual(
+            [],
+        )
+        expect([...getAllPeersFrom([createStub('userEmpty'), createStub('chatEmpty')])]).toEqual([])
+    })
+
+    it('should correctly handle users/chats fields of type number[]', () => {
+        expect([...getAllPeersFrom({ users: [123, 456], chats: [123, 456] } as any)]).toEqual([])
+    })
+
+    /* eslint-enable @typescript-eslint/no-explicit-any, @typescript-eslint/no-unsafe-argument */
+})
diff --git a/packages/core/src/utils/peer-utils.ts b/packages/core/src/utils/peer-utils.ts
index e0fbc111..7b0d46f0 100644
--- a/packages/core/src/utils/peer-utils.ts
+++ b/packages/core/src/utils/peer-utils.ts
@@ -72,14 +72,18 @@ export function getMarkedPeerId(
     switch (peer._) {
         case 'peerUser':
         case 'inputPeerUser':
+        case 'inputPeerUserFromMessage':
         case 'inputUser':
+        case 'inputUserFromMessage':
             return peer.userId
         case 'peerChat':
         case 'inputPeerChat':
             return -peer.chatId
         case 'peerChannel':
         case 'inputPeerChannel':
+        case 'inputPeerChannelFromMessage':
         case 'inputChannel':
+        case 'inputChannelFromMessage':
             return ZERO_CHANNEL_ID - peer.channelId
     }
 
@@ -110,7 +114,7 @@ export function getBasicPeerType(peer: tl.TypePeer | number): BasicPeerType {
             return 'channel'
         }
 
-        if (MAX_SECRET_CHAT_ID <= peer && peer !== ZERO_SECRET_CHAT_ID) {
+        if (MAX_SECRET_CHAT_ID >= peer && peer !== ZERO_SECRET_CHAT_ID) {
             // return 'secret'
             throw new MtUnsupportedError('Secret chats are not supported')
         }
diff --git a/packages/core/src/utils/sorted-array.test.ts b/packages/core/src/utils/sorted-array.test.ts
new file mode 100644
index 00000000..586377e7
--- /dev/null
+++ b/packages/core/src/utils/sorted-array.test.ts
@@ -0,0 +1,86 @@
+import { describe, expect, it } from 'vitest'
+
+import { SortedArray } from './sorted-array.js'
+
+describe('SortedArray', () => {
+    const ascendingComparator = (a: number, b: number) => a - b
+
+    it('should insert items in accordance with comparator', () => {
+        const arr = new SortedArray<number>([], ascendingComparator)
+
+        arr.insert(1)
+        arr.insert(2)
+        arr.insert(5)
+        arr.insert(3)
+        arr.insert(4)
+
+        expect(arr.raw).toEqual([1, 2, 3, 4, 5])
+    })
+
+    it('should insert arrays', () => {
+        const arr = new SortedArray<number>([], ascendingComparator)
+
+        arr.insert([1, 2, 5, 3, 4])
+
+        expect(arr.raw).toEqual([1, 2, 3, 4, 5])
+    })
+
+    it('should return length', () => {
+        const arr = new SortedArray<number>([], ascendingComparator)
+
+        arr.insert(1)
+        arr.insert(2)
+        arr.insert(5)
+
+        expect(arr.length).toEqual(3)
+    })
+
+    it('should return index of the item', () => {
+        const arr = new SortedArray<number>([], ascendingComparator)
+
+        arr.insert(1)
+        arr.insert(2)
+        arr.insert(5)
+
+        expect(arr.index(1)).toEqual(0)
+        expect(arr.index(2)).toEqual(1)
+        expect(arr.index(5)).toEqual(2)
+        expect(arr.index(10)).toEqual(-1)
+    })
+
+    it('should return closest index for an item not in the array', () => {
+        const arr = new SortedArray<number>([], ascendingComparator)
+
+        arr.insert(1)
+        arr.insert(2)
+        arr.insert(5)
+
+        expect(arr.index(3, true)).toEqual(2)
+        expect(arr.index(4, true)).toEqual(2) // still 2, becuse left-hand side
+        expect(arr.index(6, true)).toEqual(3)
+    })
+
+    it('should remove items by value', () => {
+        const arr = new SortedArray<number>([], ascendingComparator)
+
+        arr.insert(1)
+        arr.insert(2)
+        arr.insert(5)
+        arr.remove(2)
+
+        expect(arr.raw).toEqual([1, 5])
+    })
+
+    it('should check if item is in array', () => {
+        const arr = new SortedArray<number>([], ascendingComparator)
+
+        arr.insert(1)
+        arr.insert(2)
+        arr.insert(5)
+
+        expect(arr.includes(1)).toBeTruthy()
+        expect(arr.includes(2)).toBeTruthy()
+        expect(arr.includes(5)).toBeTruthy()
+        expect(arr.includes(10)).toBeFalsy()
+    })
+})
diff --git a/packages/core/src/utils/string-session.test.ts b/packages/core/src/utils/string-session.test.ts
new file mode 100644
index 00000000..4036822d
--- /dev/null
+++ b/packages/core/src/utils/string-session.test.ts
@@ -0,0 +1,155 @@
+import { describe, expect, it } from 'vitest'
+
+import { createStub } from '@mtcute/test'
+import { __tlReaderMap } from '@mtcute/tl/binary/reader.js'
+import { __tlWriterMap } from '@mtcute/tl/binary/writer.js'
+
+import { defaultProductionDc } from './default-dcs.js'
+import { readStringSession, writeStringSession } from './string-session.js'
+
+const stubAuthKey = new Uint8Array(32)
+const stubDcs = {
+    main: createStub('dcOption', defaultProductionDc.main),
+    media: createStub('dcOption', defaultProductionDc.media),
+}
+const stubDcsSameMedia = {
+    main: stubDcs.main,
+    media: stubDcs.main,
+}
+
+describe('writeStringSession', () => {
+    it('should write production string session without user', () => {
+        expect(
+            writeStringSession(__tlWriterMap, {
+                version: 2,
+                testMode: false,
+                primaryDcs: stubDcs,
+                authKey: stubAuthKey,
+            }),
+        ).toMatchInlineSnapshot(
+            '"AgQAAAANobcYAAAAAAIAAAAOMTQ5LjE1NC4xNjcuNTAAuwEAAA2htxgCAAAAAgAAAA8xNDkuMTU0LjE2Ny4yMjK7AQAAIAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"',
+        )
+    })
+    it('should write production string session without user with same dc for media', () => {
+        expect(
+            writeStringSession(__tlWriterMap, {
+                version: 2,
+                testMode: false,
+                primaryDcs: stubDcsSameMedia,
+                authKey: stubAuthKey,
+            }),
+        ).toMatchInlineSnapshot(
+            '"AgAAAAANobcYAAAAAAIAAAAOMTQ5LjE1NC4xNjcuNTAAuwEAACAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"',
+        )
+    })
+
+    it('should write production string session with user', () => {
+        expect(
+            writeStringSession(__tlWriterMap, {
+                version: 2,
+                testMode: false,
+                primaryDcs: stubDcs,
+                authKey: stubAuthKey,
+                self: { userId: 12345, isBot: false },
+            }),
+        ).toMatchInlineSnapshot(
+            '"AgUAAAANobcYAAAAAAIAAAAOMTQ5LjE1NC4xNjcuNTAAuwEAAA2htxgCAAAAAgAAAA8xNDkuMTU0LjE2Ny4yMjK7AQAAOTAAAAAAAAA3l3m8IAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"',
+        )
+    })
+
+    it('should write test dc string session with user', () => {
+        expect(
+            writeStringSession(__tlWriterMap, {
+                version: 2,
+                testMode: true,
+                primaryDcs: stubDcs,
+                authKey: stubAuthKey,
+                self: { userId: 12345, isBot: false },
+            }),
+        ).toMatchInlineSnapshot(
+            '"AgcAAAANobcYAAAAAAIAAAAOMTQ5LjE1NC4xNjcuNTAAuwEAAA2htxgCAAAAAgAAAA8xNDkuMTU0LjE2Ny4yMjK7AQAAOTAAAAAAAAA3l3m8IAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"',
+        )
+    })
+})
+
+describe('readStringSession', () => {
+    describe('v2', () => {
+        it('should read production string session without user', () => {
+            expect(
+                readStringSession(
+                    __tlReaderMap,
+                    'AgQAAAANobcYAAAAAAIAAAAOMTQ5LjE1NC4xNjcuNTAAuwEAAA2htxgCAAAAAgAAAA8xNDkuMTU0LjE2Ny4yMjK7AQAAIAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA',
+                ),
+            ).toEqual({
+                version: 2,
+                testMode: false,
+                primaryDcs: stubDcs,
+                authKey: stubAuthKey,
+                self: null,
+            })
+        })
+
+        it('should read production string session without user with same dc for media', () => {
+            expect(
+                readStringSession(
+                    __tlReaderMap,
+                    'AgAAAAANobcYAAAAAAIAAAAOMTQ5LjE1NC4xNjcuNTAAuwEAACAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA',
+                ),
+            ).toEqual({
+                version: 2,
+                testMode: false,
+                primaryDcs: stubDcsSameMedia,
+                authKey: stubAuthKey,
+                self: null,
+            })
+        })
+
+        it('should read production string session with user', () => {
+            expect(
+                readStringSession(
+                    __tlReaderMap,
+                    'AgUAAAANobcYAAAAAAIAAAAOMTQ5LjE1NC4xNjcuNTAAuwEAAA2htxgCAAAAAgAAAA8xNDkuMTU0LjE2Ny4yMjK7AQAAOTAAAAAAAAA3l3m8IAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA',
+                ),
+            ).toEqual({
+                version: 2,
+                testMode: false,
+                primaryDcs: stubDcs,
+                authKey: stubAuthKey,
+                self: { userId: 12345, isBot: false },
+            })
+        })
+
+        it('should read test dc string session with user', () => {
+            expect(
+                readStringSession(
+                    __tlReaderMap,
+                    'AgcAAAANobcYAAAAAAIAAAAOMTQ5LjE1NC4xNjcuNTAAuwEAAA2htxgCAAAAAgAAAA8xNDkuMTU0LjE2Ny4yMjK7AQAAOTAAAAAAAAA3l3m8IAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA',
+                ),
+            ).toEqual({
+                version: 2,
+                testMode: true,
+                primaryDcs: stubDcs,
+                authKey: stubAuthKey,
+                self: { userId: 12345, isBot: false },
+            })
+        })
+    })
+
+    describe('v1', () => {
+        it('should read string session with user', () => {
+            expect(
+                readStringSession(
+                    __tlReaderMap,
+                    'AQEAAAANobcYAAAAAAIAAAAOMTQ5LjE1NC4xNjcuNTAAuwEAADkwAAAAAAAAN5d5vCAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA',
+                ),
+            ).toEqual({
+                version: 1,
+                testMode: false,
+                // v1 didn't have separate media dc
+                primaryDcs: stubDcsSameMedia,
+                authKey: stubAuthKey,
+                self: { userId: 12345, isBot: false },
+            })
+        })
+    })
+})
diff --git a/packages/core/src/utils/string-session.ts b/packages/core/src/utils/string-session.ts
index cf15a21f..e4d7d89b 100644
--- a/packages/core/src/utils/string-session.ts
+++ b/packages/core/src/utils/string-session.ts
@@ -41,11 +41,14 @@ export function writeStringSession(writerMap: TlWriterMap, data: StringSessionDa
     writer.uint8View[0] = version
     writer.pos += 1
 
+    if (version >= 2 && data.primaryDcs.media !== data.primaryDcs.main) {
+        flags |= 4
+    }
+
     writer.int(flags)
     writer.object(data.primaryDcs.main)
 
     if (version >= 2 && data.primaryDcs.media !== data.primaryDcs.main) {
-        flags |= 4
         writer.object(data.primaryDcs.media)
     }
 
@@ -97,7 +100,7 @@ export function readStringSession(readerMap: TlReaderMap, data: string): StringS
     const key = reader.bytes()
 
     return {
-        version: 1,
+        version,
         testMode,
         primaryDcs: {
             main: primaryDc,
diff --git a/packages/core/src/utils/tl-json.test.ts b/packages/core/src/utils/tl-json.test.ts
new file mode 100644
index 00000000..b2c90a5b
--- /dev/null
+++ b/packages/core/src/utils/tl-json.test.ts
@@ -0,0 +1,98 @@
+import { describe, expect, it } from 'vitest'
+
+import { jsonToTlJson, tlJsonToJson } from './tl-json.js'
+
+describe('jsonToTlJson', () => {
+    it('should correctly handle null/undefined', () => {
+        expect(jsonToTlJson(null)).toEqual({ _: 'jsonNull' })
+        expect(jsonToTlJson(undefined)).toEqual({ _: 'jsonNull' })
+    })
+
+    it('should correctly handle booleans', () => {
+        expect(jsonToTlJson(true)).toEqual({ _: 'jsonBool', value: true })
+        expect(jsonToTlJson(false)).toEqual({ _: 'jsonBool', value: false })
+    })
+
+    it('should correctly handle numbers', () => {
+        expect(jsonToTlJson(123)).toEqual({ _: 'jsonNumber', value: 123 })
+        expect(jsonToTlJson(0)).toEqual({ _: 'jsonNumber', value: 0 })
+        expect(jsonToTlJson(-123)).toEqual({ _: 'jsonNumber', value: -123 })
+    })
+
+    it('should correctly handle strings', () => {
+        expect(jsonToTlJson('hello')).toEqual({ _: 'jsonString', value: 'hello' })
+        expect(jsonToTlJson('')).toEqual({ _: 'jsonString', value: '' })
+    })
+
+    it('should correcly handle arrays', () => {
+        expect(jsonToTlJson([1, 2, 3])).toEqual({
+            _: 'jsonArray',
+            value: [
+                { _: 'jsonNumber', value: 1 },
+                { _: 'jsonNumber', value: 2 },
+                { _: 'jsonNumber', value: 3 },
+            ],
+        })
+    })
+
+    it('should correctly handle objects', () => {
+        expect(jsonToTlJson({ a: 1, b: 2 })).toEqual({
+            _: 'jsonObject',
+            value: [
+                { _: 'jsonObjectValue', key: 'a', value: { _: 'jsonNumber', value: 1 } },
+                { _: 'jsonObjectValue', key: 'b', value: { _: 'jsonNumber', value: 2 } },
+            ],
+        })
+    })
+
+    it('should error on unsupported types', () => {
+        expect(() => jsonToTlJson(Symbol('test'))).toThrow()
+    })
+})
+
+describe('tlJsonToJson', () => {
+    it('should correctly handle null/undefined', () => {
+        expect(tlJsonToJson({ _: 'jsonNull' })).toEqual(null)
+    })
+
+    it('should correctly handle booleans', () => {
+        expect(tlJsonToJson({ _: 'jsonBool', value: true })).toEqual(true)
+        expect(tlJsonToJson({ _: 'jsonBool', value: false })).toEqual(false)
+    })
+
+    it('should correctly handle numbers', () => {
+        expect(tlJsonToJson({ _: 'jsonNumber', value: 123 })).toEqual(123)
+        expect(tlJsonToJson({ _: 'jsonNumber', value: 0 })).toEqual(0)
+        expect(tlJsonToJson({ _: 'jsonNumber', value: -123 })).toEqual(-123)
+    })
+
+    it('should correctly handle strings', () => {
+        expect(tlJsonToJson({ _: 'jsonString', value: 'hello' })).toEqual('hello')
+        expect(tlJsonToJson({ _: 'jsonString', value: '' })).toEqual('')
+    })
+
+    it('should correcly handle arrays', () => {
+        expect(
+            tlJsonToJson({
+                _: 'jsonArray',
+                value: [
+                    { _: 'jsonNumber', value: 1 },
+                    { _: 'jsonNumber', value: 2 },
+                    { _: 'jsonNumber', value: 3 },
+                ],
+            }),
+        ).toEqual([1, 2, 3])
+    })
+
+    it('should correctly handle objects', () => {
+        expect(
+            tlJsonToJson({
+                _: 'jsonObject',
+                value: [
+                    { _: 'jsonObjectValue', key: 'a', value: { _: 'jsonNumber', value: 1 } },
+                    { _: 'jsonObjectValue', key: 'b', value: { _: 'jsonNumber', value: 2 } },
+                ],
+            }),
+        ).toEqual({ a: 1, b: 2 })
+    })
+})
diff --git a/packages/core/src/utils/type-assertions.test.ts b/packages/core/src/utils/type-assertions.test.ts
new file mode 100644
index 00000000..e1fd6166
--- /dev/null
+++ b/packages/core/src/utils/type-assertions.test.ts
@@ -0,0 +1,84 @@
+import { describe, expect, it } from 'vitest'
+
+import {
+    assertTypeIs,
+    assertTypeIsNot,
+    hasPresentKey,
+    hasValueAtKey,
+    isPresent,
+    mtpAssertTypeIs,
+} from './type-assertions.js'
+
+describe('isPresent', () => {
+    it('should return true for non-null values', () => {
+        expect(isPresent(1)).toBe(true)
+        expect(isPresent('')).toBe(true)
+        expect(isPresent({})).toBe(true)
+        expect(isPresent([])).toBe(true)
+    })
+
+    it('should return false for null/undefined', () => {
+        expect(isPresent(null)).toBe(false)
+        expect(isPresent(undefined)).toBe(false)
+    })
+})
+
+describe('hasPresentKey', () => {
+    it('should return true for objects with present keys', () => {
+        expect(hasPresentKey('a')({ a: 1 })).toBe(true)
+        expect(hasPresentKey('a')({ a: 1, b: 2 })).toBe(true)
+    })
+
+    it('should return false for objects with undefined/null keys', () => {
+        expect(hasPresentKey('a')({ a: undefined })).toBe(false)
+        expect(hasPresentKey('a')({ a: null })).toBe(false)
+        expect(hasPresentKey('a')({ a: undefined, b: 2 })).toBe(false)
+        expect(hasPresentKey('a')({ a: null, b: 2 })).toBe(false)
+    })
+
+    it('should return false for objects without the key', () => {
+        expect(hasPresentKey('a')({ b: 2 })).toBe(false)
+    })
+})
+
+describe('hasValueAtKey', () => {
+    it('should return true for objects with the correct value', () => {
+        expect(hasValueAtKey('a', 1)({ a: 1 })).toBe(true)
+        expect(hasValueAtKey('a', 1)({ a: 1, b: 2 })).toBe(true)
+    })
+
+    it('should return false for objects with the wrong value', () => {
+        expect(hasValueAtKey('a', 1)({ a: 2 })).toBe(false)
+        expect(hasValueAtKey('a', 1)({ a: 2, b: 2 })).toBe(false)
+    })
+
+    it('should return false for objects without the key', () => {
+        // @ts-expect-error - we want to make sure the key is not present at runtime
+        expect(hasValueAtKey('a', 1)({ b: 2 })).toBe(false)
+    })
+})
+
+describe('assertTypeIs', () => {
+    it('should not throw for correct types', () => {
+        assertTypeIs('peerUser', { _: 'peerUser', userId: 1 }, 'peerUser')
+        mtpAssertTypeIs('peerUser', { _: 'mt_rpc_answer_unknown' }, 'mt_rpc_answer_unknown')
+    })
+
+    it('should throw for incorrect types', () => {
+        // eslint-disable-next-line
+        expect(() => assertTypeIs('peerUser', { _: 'peerChannel', channelId: 1 } as any, 'peerUser')).toThrow()
+        // eslint-disable-next-line
+        expect(() => mtpAssertTypeIs('peerUser', { _: 'mt_rpc_answer_unknown' } as any, 'peerUser')).toThrow()
+    })
+})
+
+describe('assertTypeIsNot', () => {
+    it('should not throw for correct types', () => {
+        // eslint-disable-next-line
+        assertTypeIsNot('peerUser', { _: 'peerChannel', channelId: 1 } as any, 'peerUser')
+    })
+
+    it('should throw for incorrect types', () => {
+        expect(() => assertTypeIsNot('peerUser', { _: 'peerUser', userId: 1 }, 'peerUser')).toThrow()
+    })
+})
diff --git a/packages/core/tsconfig.json b/packages/core/tsconfig.json
index d5f18899..63770709 100644
--- a/packages/core/tsconfig.json
+++ b/packages/core/tsconfig.json
@@ -3,9 +3,6 @@
     "compilerOptions": {
         "outDir": "./dist/esm",
         "rootDir": "./src",
-        "paths": {
-            "@mtcute/dispatcher": ["../dispatcher/src/state/storage.ts"],
-        }
     },
     "include": [
         "./src",
diff --git a/packages/test/src/stub.test.ts b/packages/test/src/stub.test.ts
index 6d3f311a..fcc55134 100644
--- a/packages/test/src/stub.test.ts
+++ b/packages/test/src/stub.test.ts
@@ -34,6 +34,14 @@ describe('stub', () => {
         })
     })
 
+    it('should correctly generate stubs for optional vectors', () => {
+        expect(createStub('updateChannelPinnedTopics')).toEqual({
+            _: 'updateChannelPinnedTopics',
+            channelId: 0,
+            order: [],
+        })
+    })
+
     it('should correctly generate stubs for nested types', () => {
         expect(createStub('messageActionGroupCallScheduled', { scheduleDate: 123 })).toEqual({
             _: 'messageActionGroupCallScheduled',
diff --git a/packages/test/src/utils.test.ts b/packages/test/src/utils.test.ts
new file mode 100644
index 00000000..985e365c
--- /dev/null
+++ b/packages/test/src/utils.test.ts
@@ -0,0 +1,17 @@
+import { describe, expect, it } from 'vitest'
+
+import { markedIdToPeer } from './utils.js'
+
+describe('markedIdToPeer', () => {
+    it('should correctly convert user ids', () => {
+        expect(markedIdToPeer(12345)).toEqual({ _: 'peerUser', userId: 12345 })
+    })
+
+    it('should correctly convert chat ids', () => {
+        expect(markedIdToPeer(-12345)).toEqual({ _: 'peerChat', chatId: 12345 })
+    })
+
+    it('should correctly convert channel ids', () => {
+        expect(markedIdToPeer(-1000000012345)).toEqual({ _: 'peerChannel', channelId: 12345 })
+    })
+})
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index dcb53be5..c4402755 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -127,6 +127,12 @@ importers:
         specifier: 5.2.3
         version: 5.2.3
     devDependencies:
+      '@mtcute/dispatcher':
+        specifier: workspace:^
+        version: link:../dispatcher
+      '@mtcute/test':
+        specifier: workspace:^
+        version: link:../test
       '@types/ws':
         specifier: 8.5.4
         version: 8.5.4