✨ feat: Per-client sessions, app blacklist, robustness rework

pnpm-workspace.yaml

@@ -7,6 +7,7 @@ onlyBuiltDependencies:
 minimumReleaseAge: 4320
 
 allowBuilds:
+  electron: true
   electron-winstaller: true
   esbuild: true
   koffi: true

src/main/index.ts

@@ -3,7 +3,7 @@ import { join } from 'path'
 import * as fs from 'fs'
 import { electronApp, optimizer, is } from '@electron-toolkit/utils'
 import icon from '../../resources/icon.png?asset'
-import { relay, RelayStatus } from './relay'
+import { relay, BlacklistedApp, RelayStatus } from './relay'
 
 declare const __COMMIT_HASH__: string
 
@@ -13,24 +13,38 @@ function settingsPath(): string {
 
 interface Settings {
   disabledMirrors: number[]
+  blacklistedApps: BlacklistedApp[]
   startMinimized: boolean
 }
 
+function parseBlacklistedApps(raw: unknown): BlacklistedApp[] {
+  if (!Array.isArray(raw)) return []
+  return raw.flatMap((entry): BlacklistedApp[] =>
+    entry && typeof entry.id === 'string'
+      ? [{ id: entry.id, name: typeof entry.name === 'string' ? entry.name : null }]
+      : []
+  )
+}
+
 function loadSettings(): Settings {
   try {
     const raw = fs.readFileSync(settingsPath(), 'utf8')
     const data = JSON.parse(raw)
     return {
       disabledMirrors: Array.isArray(data?.disabledMirrors) ? data.disabledMirrors : [],
+      blacklistedApps: parseBlacklistedApps(data?.blacklistedApps),
       startMinimized: data?.startMinimized === true
     }
   } catch {
-    return { disabledMirrors: [], startMinimized: false }
+    return { disabledMirrors: [], blacklistedApps: [], startMinimized: false }
   }
 }
 
 function saveSettings(settings: Settings): void {
-  fs.writeFileSync(settingsPath(), JSON.stringify(settings), 'utf8')
+  const target = settingsPath()
+  const tmp = `${target}.tmp`
+  fs.writeFileSync(tmp, JSON.stringify(settings), 'utf8')
+  fs.renameSync(tmp, target)
 }
 
 const LINUX_AUTOSTART_DESKTOP_FILE = join(
@@ -202,6 +216,7 @@ app.whenReady().then(() => {
 
   const settings = loadSettings()
   relay.setDisabledMirrors(settings.disabledMirrors)
+  relay.setBlacklistedApps(settings.blacklistedApps)
 
   ipcMain.handle('relay:get-version', () => ({
     version: app.getVersion(),
@@ -244,6 +259,12 @@ app.whenReady().then(() => {
     saveSettings({ ...current, disabledMirrors: relay.getDisabledMirrors() })
     return status
   })
+  ipcMain.handle('relay:set-app-blacklisted', (_e, appId: string, blacklisted: boolean) => {
+    const status = relay.setAppBlacklisted(appId, blacklisted)
+    const current = loadSettings()
+    saveSettings({ ...current, blacklistedApps: relay.getBlacklistedApps() })
+    return status
+  })
 
   relay.on('status', (status: RelayStatus) => {
     updateTrayMenu(status)
@@ -260,16 +281,40 @@ app.whenReady().then(() => {
   })
 })
 
-app.on('window-all-closed', () => {
+app.on('window-all-closed', () => {})
-  // Keep running in the tray
-})
 
 let stopping = false
 
+const QUIT_TIMEOUT_MS = 5000
+
 app.on('before-quit', (e) => {
   quitting = true
   if (stopping) return
   stopping = true
   e.preventDefault()
-  relay.stop().finally(() => app.exit(0))
+  const timeout = new Promise<void>((resolve) => setTimeout(resolve, QUIT_TIMEOUT_MS))
+  Promise.race([relay.stop(), timeout])
+    .catch(() => {})
+    .finally(() => {
+      relay.emergencyRestoreSync()
+      app.exit(0)
+    })
+})
+
+// Electron doesn't reliably turn SIGTERM/SIGHUP into a quit on Linux.
+for (const signal of ['SIGINT', 'SIGTERM', 'SIGHUP'] as const) {
+  process.on(signal, () => {
+    quitting = true
+    app.quit()
+  })
+}
+
+process.on('uncaughtException', (err) => {
+  console.error('Uncaught exception:', err)
+  relay.emergencyRestoreSync()
+  app.exit(1)
+})
+
+process.on('unhandledRejection', (reason) => {
+  console.error('Unhandled rejection:', reason)
 })

src/main/ipc-protocol.ts

@@ -10,7 +10,6 @@ export interface Frame {
   payload: Buffer
 }
 
-/** Buffers stream chunks and yields complete IPC frames as they arrive. */
 export class FrameReader {
   private buf = Buffer.alloc(0)
 
@@ -39,7 +38,6 @@ export function encodeFrame(op: number, payload: Buffer): Buffer {
   return Buffer.concat([header, payload])
 }
 
-/** Parses a non-handshake frame's JSON payload, returning null if it isn't JSON. */
 export function parseFramePayload(frame: Frame): Record<string, unknown> | null {
   try {
     return JSON.parse(frame.payload.toString('utf8'))

src/main/mirror-connection.ts

@@ -1,10 +1,7 @@
 import * as net from 'net'
 import { encodeFrame, FrameReader, OP_FRAME, OP_HANDSHAKE } from './ipc-protocol'
 
-/**
+const READY_TIMEOUT_MS = 10_000
- * A lazily-established connection to a secondary Discord instance that
- * mirrors the primary connection's handshake and SET_ACTIVITY frames.
- */
 
 export class MirrorConnection {
   private readonly sock: net.Socket
@@ -16,23 +13,28 @@ export class MirrorConnection {
   constructor(socketPath: string, handshakePayload: Buffer, onClose: () => void) {
     this.sock = net.createConnection(socketPath)
 
+    const readyTimeout = setTimeout(() => this.sock.destroy(), READY_TIMEOUT_MS)
+    readyTimeout.unref()
+
     this.sock.on('connect', () => {
       this.sock.write(encodeFrame(OP_HANDSHAKE, handshakePayload))
     })
 
-    // Discord sends a READY dispatch after the handshake; only once that
-    // arrives will it accept further commands like SET_ACTIVITY.
     this.sock.on('data', (chunk: Buffer) => {
       const hadFrames = this.reader.push(chunk).length > 0
       if (hadFrames && !this.ready) {
         this.ready = true
+        clearTimeout(readyTimeout)
         for (const frame of this.pending.splice(0)) this.sock.write(frame)
         if (this.closeAfterPending) this.sock.end()
       }
     })
 
-    this.sock.on('error', onClose)
+    this.sock.on('error', () => {})
-    this.sock.on('close', onClose)
+    this.sock.on('close', () => {
+      clearTimeout(readyTimeout)
+      onClose()
+    })
   }
 
   sendActivity(payload: Buffer): void {
@@ -44,7 +46,6 @@ export class MirrorConnection {
     }
   }
 
-  /** Sends a final frame (after the handshake) and closes the connection once it has been flushed. */
   sendActivityAndClose(payload: Buffer): void {
     const frame = encodeFrame(OP_FRAME, payload)
     if (this.ready) {

src/main/platform/index.ts

@@ -2,6 +2,7 @@ import { PosixPlatform } from './posix'
 import { UnsupportedPlatform } from './unsupported'
 import type { RelayPlatform } from './types'
 
+export { MAX_SOCKETS } from './types'
 export type { ClaimedSocket, ProcessInfo, RelayPlatform } from './types'
 
 export const platform: RelayPlatform =

src/main/platform/posix.ts

@@ -2,11 +2,12 @@ import * as fs from 'fs'
 import * as net from 'net'
 import * as path from 'path'
 import { execFileSync } from 'child_process'
-import type { ClaimedSocket, ProcessInfo, RelayPlatform } from './types'
+import { MAX_SOCKETS, type ClaimedSocket, type ProcessInfo, type RelayPlatform } from './types'
 
 const REAL_PREFIX = 'discord-ipc-real-'
 const FAKE_INDEX = 0
-const MAX_SOCKETS = 10
+const ALIVE_CHECK_TIMEOUT_MS = 1000
+const STALE_SOCKET_MIN_AGE_MS = 10_000
 
 function runtimeDir(): string {
   if (process.env.XDG_RUNTIME_DIR) return process.env.XDG_RUNTIME_DIR
@@ -43,6 +44,7 @@ export class PosixPlatform implements RelayPlatform {
 
   async recoverLeftoverSockets(): Promise<void> {
     for (let i = 0; i < MAX_SOCKETS; i++) {
+      try {
         const leftover = claimedPath(i)
         const original = ipcPath(i)
         if (!fs.existsSync(leftover)) continue
@@ -56,32 +58,64 @@ export class PosixPlatform implements RelayPlatform {
           fs.unlinkSync(original)
           fs.renameSync(leftover, original)
         }
+      } catch {
+        // Another process may be touching the same files; keep recovering the rest.
+      }
     }
   }
 
-  discoverAndClaim(): ClaimedSocket[] {
+  async discoverAndClaim(): Promise<ClaimedSocket[]> {
     const found: ClaimedSocket[] = []
     for (let i = 0; i < MAX_SOCKETS; i++) {
-      const claimed = this.discoverNewSocket(i)
+      const claimed = await this.discoverNewSocket(i)
       if (claimed) found.push(claimed)
     }
     return found
   }
 
-  discoverNewSocket(index: number): ClaimedSocket | null {
+  async discoverNewSocket(index: number): Promise<ClaimedSocket | null> {
     const src = ipcPath(index)
     if (!fs.existsSync(src)) return null
 
+    if (!(await isSocketAlive(src))) {
+      try {
+        if (Date.now() - fs.statSync(src).mtimeMs > STALE_SOCKET_MIN_AGE_MS) fs.unlinkSync(src)
+      } catch {
+        // Already gone.
+      }
+      return null
+    }
+
     const dst = claimedPath(index)
+    try {
       fs.renameSync(src, dst)
+    } catch {
+      return null // socket replaced between the check and the rename
+    }
     return { index, path: dst }
   }
 
   restoreSocket(claimed: ClaimedSocket): void {
+    try {
       const original = ipcPath(claimed.index)
       if (fs.existsSync(claimed.path) && !fs.existsSync(original)) {
         fs.renameSync(claimed.path, original)
       }
+    } catch {
+      // Best effort.
+    }
+  }
+
+  discardClaimedSocket(claimed: ClaimedSocket): void {
+    try {
+      fs.unlinkSync(claimed.path)
+    } catch {
+      // Already gone.
+    }
+  }
+
+  isSocketAlive(socketPath: string): Promise<boolean> {
+    return isSocketAlive(socketPath)
   }
 
   getInstanceProcess(index: number): ProcessInfo | null {
@@ -97,11 +131,16 @@ export class PosixPlatform implements RelayPlatform {
 function isSocketAlive(socketPath: string): Promise<boolean> {
   return new Promise((resolve) => {
     const sock = net.createConnection(socketPath)
-    sock.once('connect', () => {
+    let settled = false
+    const done = (alive: boolean): void => {
+      if (settled) return
+      settled = true
       sock.destroy()
-      resolve(true)
+      resolve(alive)
-    })
+    }
-    sock.once('error', () => resolve(false))
+    sock.setTimeout(ALIVE_CHECK_TIMEOUT_MS, () => done(false))
+    sock.once('connect', () => done(true))
+    sock.once('error', () => done(false))
   })
 }
 

src/main/platform/types.ts

@@ -1,3 +1,5 @@
+export const MAX_SOCKETS = 10
+
 export interface ProcessInfo {
   pid: number
   name: string
@@ -8,13 +10,6 @@ export interface ClaimedSocket {
   path: string
 }
 
-/**
- * Platform-specific primitives the relay needs to take over Discord's IPC
- * sockets and identify the processes on either end of a connection.
- *
- * Implement this interface to add support for a new OS; `RpcRelay` itself
- * contains no platform-specific code.
- */
 export interface RelayPlatform {
   readonly isSupported: boolean
 
@@ -24,21 +19,21 @@ export interface RelayPlatform {
 
   finalizeFakeSocket(fakePath: string): void
 
-  /** Checks whether the fake socket file still exists on disk (a restarted Discord client can unlink and rebind it out from under us). */
+  /** Checks whether Discord has unlinked our fake socket. */
   fakeSocketExists(fakePath: string): boolean
 
-  /**
-   * Restores sockets left claimed from a previous run that crashed before
-   * it could call restoreSocket(), so a fresh start() can discover them.
-   */
   recoverLeftoverSockets(): Promise<void>
 
-  discoverAndClaim(): ClaimedSocket[]
+  discoverAndClaim(): Promise<ClaimedSocket[]>
 
-  discoverNewSocket(index: number): ClaimedSocket | null
+  discoverNewSocket(index: number): Promise<ClaimedSocket | null>
 
   restoreSocket(claimed: ClaimedSocket): void
 
+  discardClaimedSocket(claimed: ClaimedSocket): void
+
+  isSocketAlive(socketPath: string): Promise<boolean>
+
   getInstanceProcess(index: number): ProcessInfo | null
 
   getPeerProcess(fd: number): ProcessInfo | null

src/main/platform/unsupported.ts

@@ -2,9 +2,6 @@ import type { ClaimedSocket, ProcessInfo, RelayPlatform } from './types'
 
 const NOT_SUPPORTED = new Error('Platform not supported')
 
-/**
- * Placeholder for platforms without a real implementation yet.
- */
 export class UnsupportedPlatform implements RelayPlatform {
   readonly isSupported = false
 
@@ -28,11 +25,11 @@ export class UnsupportedPlatform implements RelayPlatform {
     throw NOT_SUPPORTED
   }
 
-  discoverAndClaim(): ClaimedSocket[] {
+  async discoverAndClaim(): Promise<ClaimedSocket[]> {
     throw NOT_SUPPORTED
   }
 
-  discoverNewSocket(): ClaimedSocket | null {
+  async discoverNewSocket(): Promise<ClaimedSocket | null> {
     throw NOT_SUPPORTED
   }
 
@@ -40,6 +37,14 @@ export class UnsupportedPlatform implements RelayPlatform {
     throw NOT_SUPPORTED
   }
 
+  discardClaimedSocket(): void {
+    throw NOT_SUPPORTED
+  }
+
+  async isSocketAlive(): Promise<boolean> {
+    return false
+  }
+
   getInstanceProcess(): ProcessInfo | null {
     return null
   }

src/main/relay.ts

@@ -3,11 +3,13 @@ import { EventEmitter } from 'events'
 import * as net from 'net'
 import { encodeFrame, Frame, FrameReader, OP_HANDSHAKE, parseFramePayload } from './ipc-protocol'
 import { MirrorConnection } from './mirror-connection'
-import { platform, type ClaimedSocket, type ProcessInfo } from './platform'
+import { platform, MAX_SOCKETS, type ClaimedSocket, type ProcessInfo } from './platform'
 
-const MAX_SOCKETS = 10
 const DISCOVERY_INTERVAL_MS = 3000
 const WAITING_RETRY_INTERVAL_MS = 3000
+const MIRROR_RECONNECT_DELAY_MS = 2000
+const SERVER_CLOSE_TIMEOUT_MS = 2000
+const ASSET_FETCH_RETRY_MS = 60_000
 
 interface AppAsset {
   id: string
@@ -15,27 +17,42 @@ interface AppAsset {
   name: string
 }
 
-const appAssetCache = new Map<string, Map<string, string>>()
+interface AssetCacheEntry {
+  map: Map<string, string>
+  expires: number
+}
+
+const appAssetCache = new Map<string, AssetCacheEntry>()
 
 async function getAppAssetMap(appId: string): Promise<Map<string, string>> {
   const cached = appAssetCache.get(appId)
-  if (cached) return cached
+  if (cached && Date.now() < cached.expires) return cached.map
 
   const map = new Map<string, string>()
+  let expires = Number.POSITIVE_INFINITY
   try {
     const res = await fetch(`https://discord.com/api/v9/oauth2/applications/${appId}/assets`)
     if (res.ok) {
       const assets = (await res.json()) as AppAsset[]
       for (const asset of assets) map.set(asset.name, asset.id)
+    } else {
+      expires = Date.now() + ASSET_FETCH_RETRY_MS
     }
   } catch {
-    // Network error: cache an empty map so we don't retry every frame.
+    expires = Date.now() + ASSET_FETCH_RETRY_MS
   }
 
-  appAssetCache.set(appId, map)
+  appAssetCache.set(appId, { map, expires })
   return map
 }
 
+function clearActivityPayload(pid: number): Buffer {
+  return Buffer.from(
+    JSON.stringify({ cmd: 'SET_ACTIVITY', args: { pid, activity: null }, nonce: randomUUID() }),
+    'utf8'
+  )
+}
+
 async function resolveAssetImage(
   key: string | undefined,
   appId: string | null
@@ -68,9 +85,17 @@ export interface RelayInstance {
   process: ProcessInfo | null
 }
 
+export interface BlacklistedApp {
+  id: string
+  name: string | null
+}
+
 export interface ConnectedClient {
   id: number
   process: ProcessInfo | null
+  appId: string | null
+  blacklisted: boolean
+  activity: LastActivity | null
 }
 
 export interface ActivityAssets {
@@ -106,30 +131,41 @@ export interface RelayStatus {
   unsupported: boolean
   instances: RelayInstance[]
   connectedClients: ConnectedClient[]
-  lastActivity: LastActivity | null
+  blacklistedApps: BlacklistedApp[]
   error: string | null
 }
 
-/**
+interface ClientSession {
- * Takes over Discord's primary IPC socket (discord-ipc-0), passing every
+  id: number
- * frame through to the real primary instance unchanged, while mirroring the
+  client: net.Socket
- * handshake and SET_ACTIVITY frames to any other running Discord instances.
+  primary: net.Socket
- */
+  process: ProcessInfo | null
+  handshakePayload: Buffer | null
+  appId: string | null
+  lastActivityPayload: Buffer | null
+  lastActivityPid: number | null
+  activity: LastActivity | null
+  mirrors: Map<number, MirrorConnection>
+  reconnectTimers: Map<number, NodeJS.Timeout>
+  closed: boolean
+}
+
+/** Hijacks discord-ipc-0, passthrough to primary, mirroring frames to other instances. */
 export class RpcRelay extends EventEmitter {
   private server: net.Server | null = null
   private claimed: ClaimedSocket[] = []
   private disabledMirrors = new Set<number>()
-  private connectedClients = new Map<number, ConnectedClient>()
+  private blacklistedApps = new Map<string, string | null>()
+  private sessions = new Map<number, ClientSession>()
   private nextClientId = 1
   private discoveryTimer: NodeJS.Timeout | null = null
+  private discovering = false
   private waitingTimer: NodeJS.Timeout | null = null
-  private lastActivity: LastActivity | null = null
   private running = false
   private waiting = false
+  private fakeOwned = false
   private lastError: string | null = null
   private restarting = false
-  private mirrors = new Map<number, MirrorConnection>()
-  private lastActivityPid = new Map<number, number>()
 
   getStatus(): RelayStatus {
     const instances: RelayInstance[] = this.claimed.map(({ index, path: socketPath }, i) => ({
@@ -145,8 +181,14 @@ export class RpcRelay extends EventEmitter {
       waiting: this.waiting,
       unsupported: !platform.isSupported,
       instances,
-      connectedClients: [...this.connectedClients.values()],
+      connectedClients: [...this.sessions.values()].map((s) => ({
-      lastActivity: this.lastActivity,
+        id: s.id,
+        process: s.process,
+        appId: s.appId,
+        blacklisted: this.isBlacklisted(s),
+        activity: s.activity
+      })),
+      blacklistedApps: this.getBlacklistedApps(),
       error: this.lastError
     }
   }
@@ -172,6 +214,60 @@ export class RpcRelay extends EventEmitter {
     this.disabledMirrors = new Set(indices)
   }
 
+  getBlacklistedApps(): BlacklistedApp[] {
+    return [...this.blacklistedApps].map(([id, name]) => ({ id, name }))
+  }
+
+  setBlacklistedApps(apps: BlacklistedApp[]): void {
+    this.blacklistedApps = new Map(apps.map((a) => [a.id, a.name]))
+  }
+
+  setAppBlacklisted(appId: string, blacklisted: boolean): RelayStatus {
+    if (blacklisted) {
+      const session = [...this.sessions.values()].find((s) => s.appId === appId)
+      const name = session?.activity?.app ?? session?.process?.name ?? null
+      this.blacklistedApps.set(appId, name ?? this.blacklistedApps.get(appId) ?? null)
+    } else {
+      this.blacklistedApps.delete(appId)
+    }
+
+    for (const session of this.sessions.values()) {
+      if (session.appId !== appId) continue
+      if (blacklisted) {
+        this.clearSessionMirrors(session)
+      } else if (session.lastActivityPayload) {
+        for (let i = 1; i < this.claimed.length; i++) {
+          const target = this.claimed[i]
+          if (this.disabledMirrors.has(target.index)) continue
+          if (this.ensureMirror(session, target)) {
+            session.mirrors.get(target.index)?.sendActivity(session.lastActivityPayload)
+          }
+        }
+      }
+    }
+
+    this.emitStatus()
+    return this.getStatus()
+  }
+
+  private isBlacklisted(session: ClientSession): boolean {
+    return session.appId !== null && this.blacklistedApps.has(session.appId)
+  }
+
+  private clearSessionMirrors(session: ClientSession): void {
+    for (const timer of session.reconnectTimers.values()) clearTimeout(timer)
+    session.reconnectTimers.clear()
+
+    for (const mirror of session.mirrors.values()) {
+      if (session.lastActivityPid !== null) {
+        mirror.sendActivityAndClose(clearActivityPayload(session.lastActivityPid))
+      } else {
+        mirror.destroy()
+      }
+    }
+    session.mirrors.clear()
+  }
+
   async start(): Promise<void> {
     if (this.running) return
     this.lastError = null
@@ -183,16 +279,18 @@ export class RpcRelay extends EventEmitter {
     }
 
     await platform.recoverLeftoverSockets()
-    this.claimed = platform.discoverAndClaim()
+    const claimed = await platform.discoverAndClaim()
 
-    if (this.claimed.length === 0) {
+    if (claimed.length === 0) {
       this.waitForDiscord()
       return
     }
 
+    this.claimed = claimed
     this.waiting = false
     this.stopWaitingTimer()
 
+    try {
       const fake = platform.fakeSocketPath()
       platform.removeFakeSocket(fake)
 
@@ -211,6 +309,16 @@ export class RpcRelay extends EventEmitter {
       })
 
       platform.finalizeFakeSocket(fake)
+      this.fakeOwned = true
+    } catch (err) {
+      this.server?.close()
+      this.server = null
+      for (const c of this.claimed) platform.restoreSocket(c)
+      this.claimed = []
+      this.lastError = err instanceof Error ? err.message : String(err)
+      this.emitStatus()
+      throw err
+    }
 
     this.running = true
     this.startDiscoveryTimer()
@@ -228,23 +336,41 @@ export class RpcRelay extends EventEmitter {
     this.running = false
     this.stopDiscoveryTimer()
 
+    for (const session of [...this.sessions.values()]) this.destroySession(session)
+
     if (this.server) {
-      await new Promise<void>((resolve) => this.server!.close(() => resolve()))
+      const server = this.server
       this.server = null
+      await new Promise<void>((resolve) => {
+        const timeout = setTimeout(resolve, SERVER_CLOSE_TIMEOUT_MS)
+        server.close(() => {
+          clearTimeout(timeout)
+          resolve()
+        })
+      })
     }
 
     platform.removeFakeSocket(platform.fakeSocketPath())
+    this.fakeOwned = false
     for (const claimed of this.claimed) platform.restoreSocket(claimed)
 
-    for (const mirror of this.mirrors.values()) mirror.destroy()
-    this.mirrors.clear()
-    this.lastActivityPid.clear()
-
     this.claimed = []
-    this.connectedClients.clear()
     this.emitStatus()
   }
 
+  emergencyRestoreSync(): void {
+    try {
+      if (this.fakeOwned) {
+        platform.removeFakeSocket(platform.fakeSocketPath())
+        this.fakeOwned = false
+      }
+    } catch {
+      // Best effort.
+    }
+    for (const claimed of this.claimed) platform.restoreSocket(claimed)
+    this.claimed = []
+  }
+
   private primaryIndex(): number | undefined {
     return this.claimed[0]?.index
   }
@@ -273,7 +399,7 @@ export class RpcRelay extends EventEmitter {
 
   private startDiscoveryTimer(): void {
     this.stopDiscoveryTimer()
-    this.discoveryTimer = setInterval(() => this.discoverNewInstances(), DISCOVERY_INTERVAL_MS)
+    this.discoveryTimer = setInterval(() => void this.discoverInstances(), DISCOVERY_INTERVAL_MS)
   }
 
   private stopDiscoveryTimer(): void {
@@ -283,66 +409,104 @@ export class RpcRelay extends EventEmitter {
     }
   }
 
-  /** Picks up Discord instances launched after the relay started, and recovers from a stolen primary socket. */
+  /** Periodic: recover stolen primary, prune dead instances, discover new ones. */
-  private discoverNewInstances(): void {
+  private async discoverInstances(): Promise<void> {
-    if (!this.running) return
+    if (!this.running || this.discovering) return
-
+    this.discovering = true
+    try {
       if (!platform.fakeSocketExists(platform.fakeSocketPath())) {
         void this.restart()
         return
       }
 
-    const claimedIndices = new Set(this.claimed.map((c) => c.index))
       let changed = false
 
+      for (const claimed of [...this.claimed]) {
+        if (await platform.isSocketAlive(claimed.path)) continue
+        if (!this.running) return
+
+        if (claimed === this.claimed[0]) {
+          void this.restart()
+          return
+        }
+
+        this.claimed = this.claimed.filter((c) => c !== claimed)
+        platform.discardClaimedSocket(claimed)
+        for (const session of this.sessions.values()) {
+          this.dropSessionMirror(session, claimed.index)
+        }
+        changed = true
+      }
+
+      const claimedIndices = new Set(this.claimed.map((c) => c.index))
       for (let i = 1; i < MAX_SOCKETS; i++) {
         if (claimedIndices.has(i)) continue
-      const found = platform.discoverNewSocket(i)
+        const found = await platform.discoverNewSocket(i)
-      if (found) {
+        if (!found) continue
+        if (!this.running) {
+          platform.restoreSocket(found)
+          return
+        }
+
         this.claimed.push(found)
         changed = true
+
+        if (!this.disabledMirrors.has(found.index)) {
+          for (const session of this.sessions.values()) {
+            if (this.isBlacklisted(session)) continue
+            if (this.ensureMirror(session, found) && session.lastActivityPayload) {
+              session.mirrors.get(found.index)?.sendActivity(session.lastActivityPayload)
+            }
+          }
         }
       }
 
       if (changed) this.emitStatus()
+    } catch (err) {
+      this.lastError = err instanceof Error ? err.message : String(err)
+      this.emitStatus()
+    } finally {
+      this.discovering = false
+    }
   }
 
   private handleClient(client: net.Socket): void {
-    const clientId = this.nextClientId++
+    const primaryClaimed = this.claimed[0]
+    if (!primaryClaimed) {
+      client.destroy()
+      return
+    }
+
     const fd = (client as unknown as { _handle?: { fd?: number } })._handle?.fd
-    this.connectedClients.set(clientId, {
+    const session: ClientSession = {
-      id: clientId,
+      id: this.nextClientId++,
-      process: fd !== undefined ? platform.getPeerProcess(fd) : null
+      client,
-    })
+      primary: net.createConnection(primaryClaimed.path),
+      process: fd !== undefined ? platform.getPeerProcess(fd) : null,
+      handshakePayload: null,
+      appId: null,
+      lastActivityPayload: null,
+      lastActivityPid: null,
+      activity: null,
+      mirrors: new Map(),
+      reconnectTimers: new Map(),
+      closed: false
+    }
+    this.sessions.set(session.id, session)
     this.emitStatus()
 
-    const primaryPath = this.claimed[0].path
+    const { primary } = session
-    const primary = net.createConnection(primaryPath)
-
     const clientReader = new FrameReader()
     const primaryReader = new FrameReader()
 
-    let handshakePayload: Buffer | null = null
-
-    const cleanup = (): void => {
-      client.destroy()
-      primary.destroy()
-      for (const mirror of this.mirrors.values()) mirror.destroy()
-      this.mirrors.clear()
-      this.lastActivityPid.clear()
-      this.connectedClients.delete(clientId)
-      this.emitStatus()
-    }
-
-    let clientAppId: string | null = null
     let primaryConnected = false
     const pendingToPrimary: Buffer[] = []
 
     client.on('data', (chunk: Buffer) => {
       for (const frame of clientReader.push(chunk)) {
         if (frame.op === OP_HANDSHAKE) {
-          handshakePayload = frame.payload
+          session.handshakePayload = frame.payload
-          clientAppId = (parseFramePayload(frame)?.client_id as string) ?? null
+          session.appId = (parseFramePayload(frame)?.client_id as string) ?? null
         }
 
         const encoded = encodeFrame(frame.op, frame.payload)
@@ -352,8 +516,8 @@ export class RpcRelay extends EventEmitter {
           pendingToPrimary.push(encoded)
         }
 
-        if (handshakePayload) this.mirrorFrame(frame, handshakePayload)
+        if (session.handshakePayload) this.mirrorFrame(session, frame)
-        void this.recordActivity(frame, clientAppId)
+        void this.recordActivity(session, frame)
       }
     })
 
@@ -368,21 +532,48 @@ export class RpcRelay extends EventEmitter {
       })
     })
 
+    const cleanup = (): void => this.destroySession(session)
+
     client.on('error', cleanup)
+    client.on('close', cleanup)
+    primary.on('close', cleanup)
     primary.on('error', (err) => {
       cleanup()
-      if ((err as NodeJS.ErrnoException).code === 'ECONNREFUSED') {
+      const code = (err as NodeJS.ErrnoException).code
+      if (code === 'ECONNREFUSED' || code === 'ENOENT') {
         void this.restart()
       } else {
         this.lastError = `Primary connection error: ${err.message}`
         this.emitStatus()
       }
     })
-    client.on('close', cleanup)
-    primary.on('close', cleanup)
   }
 
-  /** Restarts the relay, picking up any Discord instance that has replaced its IPC socket. */
+  private destroySession(session: ClientSession): void {
+    if (session.closed) return
+    session.closed = true
+
+    session.client.destroy()
+    session.primary.destroy()
+    for (const timer of session.reconnectTimers.values()) clearTimeout(timer)
+    session.reconnectTimers.clear()
+    for (const mirror of session.mirrors.values()) mirror.destroy()
+    session.mirrors.clear()
+
+    this.sessions.delete(session.id)
+    this.emitStatus()
+  }
+
+  private dropSessionMirror(session: ClientSession, index: number): void {
+    const timer = session.reconnectTimers.get(index)
+    if (timer) {
+      clearTimeout(timer)
+      session.reconnectTimers.delete(index)
+    }
+    session.mirrors.get(index)?.destroy()
+    session.mirrors.delete(index)
+  }
+
   private async restart(): Promise<void> {
     if (this.restarting) return
     this.restarting = true
@@ -397,79 +588,106 @@ export class RpcRelay extends EventEmitter {
     }
   }
 
-  /** Forwards the handshake and SET_ACTIVITY frames to every enabled mirror instance. */
+  private mirrorFrame(session: ClientSession, frame: Frame): void {
-  private mirrorFrame(frame: Frame, handshakePayload: Buffer): void {
     const payload = frame.op !== OP_HANDSHAKE ? parseFramePayload(frame) : null
     const isSetActivity = payload?.cmd === 'SET_ACTIVITY'
     if (frame.op !== OP_HANDSHAKE && !isSetActivity) return
 
     if (isSetActivity) {
+      session.lastActivityPayload = frame.payload
       const pid = (payload!.args as { pid?: number } | undefined)?.pid
-      if (typeof pid === 'number') {
+      if (typeof pid === 'number') session.lastActivityPid = pid
-        for (let i = 1; i < this.claimed.length; i++) {
-          this.lastActivityPid.set(this.claimed[i].index, pid)
-        }
-      }
     }
 
+    if (this.isBlacklisted(session)) return
+
     for (let i = 1; i < this.claimed.length; i++) {
-      const { index, path: mirrorPath } = this.claimed[i]
+      const { index } = this.claimed[i]
 
       if (this.disabledMirrors.has(index)) {
-        this.mirrors.get(index)?.destroy()
+        this.dropSessionMirror(session, index)
-        this.mirrors.delete(index)
         continue
       }
 
-      let mirror = this.mirrors.get(index)
+      this.ensureMirror(session, this.claimed[i])
-      if (!mirror) {
+      if (frame.op !== OP_HANDSHAKE) session.mirrors.get(index)?.sendActivity(frame.payload)
-        const newMirror: MirrorConnection = new MirrorConnection(
+    }
-          mirrorPath,
+  }
-          handshakePayload,
+
+  private ensureMirror(session: ClientSession, target: ClaimedSocket): boolean {
+    if (session.closed || !session.handshakePayload) return false
+    if (session.mirrors.has(target.index)) return false
+
+    const mirror: MirrorConnection = new MirrorConnection(
+      target.path,
+      session.handshakePayload,
       () => {
-            if (this.mirrors.get(index) === newMirror) this.mirrors.delete(index)
+        if (session.mirrors.get(target.index) === mirror) {
+          session.mirrors.delete(target.index)
+          this.scheduleMirrorReconnect(session, target.index)
+        }
       }
     )
-        mirror = newMirror
+    session.mirrors.set(target.index, mirror)
-        this.mirrors.set(index, mirror)
+    return true
-        if (frame.op === OP_HANDSHAKE) continue // handshake already sent on connect
   }
 
-      if (frame.op !== OP_HANDSHAKE) mirror.sendActivity(frame.payload)
+  private scheduleMirrorReconnect(session: ClientSession, index: number): void {
+    if (session.closed || !this.running) return
+    if (session.reconnectTimers.has(index)) return
+
+    const timer = setTimeout(() => {
+      session.reconnectTimers.delete(index)
+      if (session.closed || !this.running) return
+      if (this.disabledMirrors.has(index) || this.isBlacklisted(session)) return
+      if (!session.lastActivityPayload) return
+
+      const target = this.claimed.find((c, i) => i > 0 && c.index === index)
+      if (!target) return
+
+      if (this.ensureMirror(session, target)) {
+        session.mirrors.get(index)?.sendActivity(session.lastActivityPayload)
       }
+    }, MIRROR_RECONNECT_DELAY_MS)
+    session.reconnectTimers.set(index, timer)
   }
 
-  /** Sends a SET_ACTIVITY frame clearing the presence on a mirror, then disconnects it. */
   private clearMirrorActivity(index: number): void {
-    const mirror = this.mirrors.get(index)
+    for (const session of this.sessions.values()) {
-    if (!mirror) return
+      const timer = session.reconnectTimers.get(index)
+      if (timer) {
+        clearTimeout(timer)
+        session.reconnectTimers.delete(index)
+      }
 
-    const pid = this.lastActivityPid.get(index)
+      const mirror = session.mirrors.get(index)
-    if (pid !== undefined) {
+      if (!mirror) continue
-      const clearPayload = Buffer.from(
+
-        JSON.stringify({
+      if (session.lastActivityPid !== null) {
-          cmd: 'SET_ACTIVITY',
+        mirror.sendActivityAndClose(clearActivityPayload(session.lastActivityPid))
-          args: { pid, activity: null },
-          nonce: randomUUID()
-        }),
-        'utf8'
-      )
-      mirror.sendActivityAndClose(clearPayload)
       } else {
         mirror.destroy()
       }
 
-    this.mirrors.delete(index)
+      session.mirrors.delete(index)
-    this.lastActivityPid.delete(index)
+    }
   }
 
-  private async recordActivity(frame: Frame, appId: string | null): Promise<void> {
+  private async recordActivity(session: ClientSession, frame: Frame): Promise<void> {
     if (frame.op === OP_HANDSHAKE) return
 
     const data = parseFramePayload(frame)
     if (data?.cmd !== 'SET_ACTIVITY') return
 
-    const activity = (data.args as { activity?: Record<string, unknown> })?.activity ?? {}
+    const at = Date.now()
+    const appId = session.appId
+    const activity = (data.args as { activity?: Record<string, unknown> | null })?.activity
+
+    if (!activity) {
+      session.activity = null
+      this.emitStatus()
+      return
+    }
 
     const rawAssets = activity.assets as Record<string, string> | undefined
     const assets: ActivityAssets | null = rawAssets
@@ -494,14 +712,18 @@ export class RpcRelay extends EventEmitter {
       ? rawButtons.map((b) => ({ label: b.label, url: b.url }))
       : []
 
-    this.lastActivity = {
+    // Prevent stale network-delayed frames from overwriting newer ones.
+    if (session.closed) return
+    if (session.activity && session.activity.at > at) return
+
+    session.activity = {
       app: (activity.name as string) ?? null,
       details: (activity.details as string) ?? null,
       state: (activity.state as string) ?? null,
       assets,
       timestamps,
       buttons,
-      at: Date.now()
+      at
     }
     this.emitStatus()
   }

src/preload/index.ts

@@ -16,6 +16,8 @@ const api = {
     ipcRenderer.invoke('relay:set-start-minimized', enabled),
   setMirrorEnabled: (index: number, enabled: boolean): Promise<RelayStatus> =>
     ipcRenderer.invoke('relay:set-mirror-enabled', index, enabled),
+  setAppBlacklisted: (appId: string, blacklisted: boolean): Promise<RelayStatus> =>
+    ipcRenderer.invoke('relay:set-app-blacklisted', appId, blacklisted),
   onStatus: (callback: (status: RelayStatus) => void): (() => void) => {
     const listener = (_e: unknown, status: RelayStatus): void => callback(status)
     ipcRenderer.on('relay:status', listener)

src/renderer/src/App.tsx

@@ -1,6 +1,6 @@
-import { useEffect, useState } from 'react'
+import { useEffect, useRef, useState } from 'react'
-import { ChevronLeft, Info, Settings } from 'lucide-react'
+import { ChevronLeft, ChevronRight, Eye, EyeOff, Info, Settings } from 'lucide-react'
-import type { RelayStatus } from '../../main/relay'
+import type { ConnectedClient, LastActivity, RelayStatus } from '../../main/relay'
 import { InstanceRow } from './components/InstanceRow'
 import { Toggle } from './components/Toggle'
 import { Button, LinkButton } from './components/Button'
@@ -11,7 +11,7 @@ const EMPTY_STATUS: RelayStatus = {
   unsupported: false,
   instances: [],
   connectedClients: [],
-  lastActivity: null,
+  blacklistedApps: [],
   error: null
 }
 
@@ -38,13 +38,7 @@ function formatDuration(ms: number): string {
   return `${minutes}:${String(seconds).padStart(2, '0')}`
 }
 
-function ActivityPreview({
+function ActivityPreview({ activity }: { activity: LastActivity }): React.JSX.Element | null {
-  activity
-}: {
-  activity: RelayStatus['lastActivity']
-}): React.JSX.Element | null {
-  if (!activity) return null
-
   const { app, details, state, assets, timestamps, buttons, at } = activity
   const elapsed = timestamps ? formatElapsed(timestamps.start, timestamps.end) : null
 
@@ -61,7 +55,7 @@ function ActivityPreview({
             />
           ) : (
             <div className="w-16 h-16 rounded-lg bg-zinc-700 flex items-center justify-center text-zinc-500 text-xs">
-              {app ? app.slice(0, 2).toUpperCase() : '—'}
+              {app ? app.slice(0, 2).toUpperCase() : '-'}
             </div>
           )}
           {assets?.smallImage && (
@@ -99,6 +93,137 @@ function ActivityPreview({
   )
 }
 
+type ToggleBlacklist = (appId: string, blacklisted: boolean) => void
+
+function ClientRow({
+  client,
+  onToggleBlacklist
+}: {
+  client: ConnectedClient
+  onToggleBlacklist: ToggleBlacklist
+}): React.JSX.Element {
+  return (
+    <div className="flex flex-col gap-2">
+      <div className="flex items-center justify-between gap-2">
+        <span className="text-zinc-300 truncate">
+          {client.process
+            ? `${client.process.name} (pid ${client.process.pid})`
+            : 'unknown process'}
+        </span>
+        <Button
+          variant="ghost"
+          className="p-1 shrink-0"
+          disabled={!client.appId}
+          onClick={() => client.appId && onToggleBlacklist(client.appId, !client.blacklisted)}
+          aria-label={client.blacklisted ? 'Enable mirroring' : 'Disable mirroring'}
+          title={
+            !client.appId
+              ? 'Waiting for handshake'
+              : client.blacklisted
+                ? 'Blacklisted - not mirrored. Click to mirror again.'
+                : 'Mirrored. Click to blacklist this app.'
+          }
+        >
+          {client.blacklisted ? (
+            <EyeOff className="w-4 h-4 text-red-400" />
+          ) : (
+            <Eye className="w-4 h-4" />
+          )}
+        </Button>
+      </div>
+      {client.blacklisted && <div className="text-xs text-red-400/90">Blacklisted</div>}
+      {client.activity && (
+        <div
+          className={`rounded-lg bg-zinc-900/60 border p-3 ${
+            client.blacklisted ? 'border-red-900/60 opacity-50' : 'border-zinc-700/60'
+          }`}
+        >
+          <ActivityPreview activity={client.activity} />
+        </div>
+      )}
+    </div>
+  )
+}
+
+function ClientCarousel({
+  clients,
+  onToggleBlacklist
+}: {
+  clients: ConnectedClient[]
+  onToggleBlacklist: ToggleBlacklist
+}): React.JSX.Element {
+  const scrollRef = useRef<HTMLDivElement>(null)
+  const [index, setIndex] = useState(0)
+
+  const current = Math.min(index, clients.length - 1)
+
+  const scrollTo = (i: number): void => {
+    scrollRef.current?.scrollTo({ left: i * scrollRef.current.clientWidth, behavior: 'smooth' })
+  }
+
+  const onScroll = (): void => {
+    const el = scrollRef.current
+    if (el) setIndex(Math.round(el.scrollLeft / el.clientWidth))
+  }
+
+  return (
+    <div className="flex flex-col gap-2">
+      <div
+        ref={scrollRef}
+        onScroll={onScroll}
+        className="flex overflow-x-auto snap-x snap-mandatory [scrollbar-width:none] [&::-webkit-scrollbar]:hidden"
+      >
+        {clients.map((client) => (
+          <div key={client.id} className="w-full shrink-0 snap-center">
+            <ClientRow client={client} onToggleBlacklist={onToggleBlacklist} />
+          </div>
+        ))}
+      </div>
+
+      {clients.length > 1 && (
+        <div className="flex items-center justify-between">
+          <Button
+            variant="ghost"
+            className="p-1"
+            onClick={() => scrollTo(current - 1)}
+            disabled={current === 0}
+            aria-label="Previous client"
+          >
+            <ChevronLeft className="w-4 h-4" />
+          </Button>
+          <div className="flex gap-1.5">
+            {clients.map((client, i) => (
+              <button
+                key={client.id}
+                onClick={() => scrollTo(i)}
+                aria-label={`Show client ${i + 1}`}
+                className={`w-1.5 h-1.5 rounded-full transition-colors ${
+                  client.blacklisted
+                    ? i === current
+                      ? 'bg-red-400'
+                      : 'bg-red-900 hover:bg-red-700'
+                    : i === current
+                      ? 'bg-zinc-300'
+                      : 'bg-zinc-600 hover:bg-zinc-500'
+                }`}
+              />
+            ))}
+          </div>
+          <Button
+            variant="ghost"
+            className="p-1"
+            onClick={() => scrollTo(current + 1)}
+            disabled={current === clients.length - 1}
+            aria-label="Next client"
+          >
+            <ChevronRight className="w-4 h-4" />
+          </Button>
+        </div>
+      )}
+    </div>
+  )
+}
+
 export function App(): React.JSX.Element {
   const [status, setStatus] = useState<RelayStatus>(EMPTY_STATUS)
   const [loading, setLoading] = useState(false)
@@ -137,6 +262,10 @@ export function App(): React.JSX.Element {
     setStatus(await window.api.setMirrorEnabled(index, enabled))
   }
 
+  const onToggleBlacklist = async (appId: string, blacklisted: boolean): Promise<void> => {
+    setStatus(await window.api.setAppBlacklisted(appId, blacklisted))
+  }
+
   const onToggleAutostart = async (enabled: boolean): Promise<void> => {
     setAutostart(await window.api.setAutostart(enabled))
   }
@@ -196,6 +325,33 @@ export function App(): React.JSX.Element {
           </div>
         </section>
 
+        <section className="rounded-xl bg-zinc-800/60 border border-zinc-700 p-4 flex flex-col gap-2">
+          <h2 className="text-sm text-zinc-400 mb-1">Blacklisted apps</h2>
+          <div className="flex flex-col gap-1.5 text-sm">
+            {status.blacklistedApps.length > 0 ? (
+              status.blacklistedApps.map((app) => (
+                <div key={app.id} className="flex items-center justify-between gap-2">
+                  <div className="flex flex-col min-w-0">
+                    <span className="text-zinc-300 truncate">{app.name ?? 'Unknown app'}</span>
+                    <span className="text-xs text-zinc-500 truncate">{app.id}</span>
+                  </div>
+                  <Button
+                    variant="ghost"
+                    className="p-1 shrink-0"
+                    onClick={() => onToggleBlacklist(app.id, false)}
+                    aria-label={`Remove ${app.name ?? app.id} from blacklist`}
+                    title="Remove from blacklist and mirror again"
+                  >
+                    <EyeOff className="w-4 h-4 text-red-400" />
+                  </Button>
+                </div>
+              ))
+            ) : (
+              <div className="text-zinc-500">No blacklisted apps</div>
+            )}
+          </div>
+        </section>
+
         {appVersion && (
           <p className="text-xs text-zinc-500 mt-auto">
             Version {appVersion.version} ({appVersion.commit})
@@ -265,33 +421,26 @@ export function App(): React.JSX.Element {
       </section>
 
       <section className="rounded-xl bg-zinc-800/60 border border-zinc-700 p-4 flex flex-col gap-2">
-        <h2 className="text-sm text-zinc-400 mb-1">Connected RPC Clients</h2>
+        <div className="flex items-center justify-between mb-1">
-        <div className="flex flex-col gap-1.5 text-sm">
+          <h2 className="text-sm text-zinc-400">Connected RPC Clients</h2>
-          {status.connectedClients.length > 0 ? (
+          {status.connectedClients.length > 0 && (
-            status.connectedClients.map((client) => (
+            <span className="text-xs text-zinc-500 bg-zinc-700/60 rounded-full px-2 py-0.5">
-              <div key={client.id} className="flex items-center justify-between gap-2">
+              {status.connectedClients.length}
-                <span className="text-zinc-300">
-                  {client.process
-                    ? `${client.process.name} (pid ${client.process.pid})`
-                    : 'unknown process'}
             </span>
+          )}
         </div>
-            ))
+        <div className="text-sm">
+          {status.connectedClients.length > 0 ? (
+            <ClientCarousel
+              clients={status.connectedClients}
+              onToggleBlacklist={onToggleBlacklist}
+            />
           ) : (
             <div className="text-zinc-500">No clients connected</div>
           )}
         </div>
       </section>
 
-      <section className="rounded-xl bg-zinc-800/60 border border-zinc-700 p-4 flex flex-col gap-2">
-        <h2 className="text-sm text-zinc-400 mb-1">Last Mirrored Activity</h2>
-        {status.lastActivity ? (
-          <ActivityPreview activity={status.lastActivity} />
-        ) : (
-          <div className="text-sm text-zinc-300">No activity yet</div>
-        )}
-      </section>
-
       <p className="text-xs text-zinc-500 mt-auto">
         Apps using Discord Rich Presence need to be restarted after toggling the relay to pick up
         the change.