✨ feat: primary promote and locking

src/main/index.ts

@@ -15,6 +15,7 @@ interface Settings {
   disabledMirrors: number[]
   blacklistedApps: BlacklistedApp[]
   startMinimized: boolean
+  lockedPrimary: string | null
 }
 
 function parseBlacklistedApps(raw: unknown): BlacklistedApp[] {
@@ -33,10 +34,11 @@ function loadSettings(): Settings {
     return {
       disabledMirrors: Array.isArray(data?.disabledMirrors) ? data.disabledMirrors : [],
       blacklistedApps: parseBlacklistedApps(data?.blacklistedApps),
-      startMinimized: data?.startMinimized === true
+      startMinimized: data?.startMinimized === true,
+      lockedPrimary: typeof data?.lockedPrimary === 'string' ? data.lockedPrimary : null
     }
   } catch {
-    return { disabledMirrors: [], blacklistedApps: [], startMinimized: false }
+    return { disabledMirrors: [], blacklistedApps: [], startMinimized: false, lockedPrimary: null }
   }
 }
 
@@ -217,6 +219,7 @@ app.whenReady().then(() => {
   const settings = loadSettings()
   relay.setDisabledMirrors(settings.disabledMirrors)
   relay.setBlacklistedApps(settings.blacklistedApps)
+  relay.setLockedPrimary(settings.lockedPrimary)
 
   ipcMain.handle('relay:get-version', () => ({
     version: app.getVersion(),
@@ -265,6 +268,18 @@ app.whenReady().then(() => {
     saveSettings({ ...current, blacklistedApps: relay.getBlacklistedApps() })
     return status
   })
+  ipcMain.handle('relay:unlock-primary', () => {
+    const status = relay.unlockPrimary()
+    const current = loadSettings()
+    saveSettings({ ...current, lockedPrimary: relay.getLockedPrimary() })
+    return status
+  })
+  ipcMain.handle('relay:promote-to-primary', async (_e, index: number) => {
+    const status = await relay.promoteToPrimary(index)
+    const current = loadSettings()
+    saveSettings({ ...current, lockedPrimary: relay.getLockedPrimary() })
+    return status
+  })
 
   relay.on('status', (status: RelayStatus) => {
     updateTrayMenu(status)

src/main/platform/posix.ts

@@ -1,7 +1,7 @@
 import * as fs from 'fs'
 import * as net from 'net'
 import * as path from 'path'
-import { execFileSync } from 'child_process'
+import { execFileSync, spawn } from 'child_process'
 import { MAX_SOCKETS, type ClaimedSocket, type ProcessInfo, type RelayPlatform } from './types'
 
 const REAL_PREFIX = 'discord-ipc-real-'
@@ -9,9 +9,27 @@ const FAKE_INDEX = 0
 const ALIVE_CHECK_TIMEOUT_MS = 1000
 const STALE_SOCKET_MIN_AGE_MS = 10_000
 
+let darwinTempDir: string | null | undefined
+
+// $TMPDIR can be overridden by a shell, so ask the OS where Discord really binds.
+function resolveDarwinTempDir(): string | null {
+  if (darwinTempDir !== undefined) return darwinTempDir
+  try {
+    darwinTempDir = execFileSync('getconf', ['DARWIN_USER_TEMP_DIR'], {
+      encoding: 'utf8',
+      timeout: 1000
+    }).trim()
+  } catch {
+    darwinTempDir = null
+  }
+  return darwinTempDir
+}
+
 function runtimeDir(): string {
   if (process.env.XDG_RUNTIME_DIR) return process.env.XDG_RUNTIME_DIR
-  if (process.platform === 'darwin') return process.env.TMPDIR ?? '/tmp'
+  if (process.platform === 'darwin') {
+    return resolveDarwinTempDir() ?? process.env.TMPDIR ?? '/tmp'
+  }
   return `/run/user/${process.getuid?.() ?? 0}`
 }
 
@@ -30,6 +48,10 @@ export class PosixPlatform implements RelayPlatform {
     return ipcPath(FAKE_INDEX)
   }
 
+  ipcSocketPath(index: number): string {
+    return ipcPath(index)
+  }
+
   removeFakeSocket(fakePath: string): void {
     if (fs.existsSync(fakePath)) fs.unlinkSync(fakePath)
   }
@@ -118,14 +140,129 @@ export class PosixPlatform implements RelayPlatform {
     return isSocketAlive(socketPath)
   }
 
+  async removeStaleIpcSocket(index: number): Promise<void> {
+    const p = ipcPath(index)
+    if (!fs.existsSync(p)) return
+    if (await isSocketAlive(p)) return
+    try {
+      fs.unlinkSync(p)
+    } catch {
+      // Already gone or replaced.
+    }
+  }
+
   getInstanceProcess(index: number): ProcessInfo | null {
-    // /proc/net/unix reports the original bind path even after the file is renamed on disk
+    // lsof/procfs still report the original bind path even after we rename to -real-N.
     return findSocketOwner(ipcPath(index))
   }
 
   getPeerProcess(fd: number): ProcessInfo | null {
     return findPeerProcess(fd)
   }
+
+  killProcess(pid: number): boolean {
+    try {
+      process.kill(pid, 'SIGTERM')
+      return true
+    } catch {
+      return false
+    }
+  }
+
+  isProcessAlive(pid: number): boolean {
+    try {
+      process.kill(pid, 0)
+      return true
+    } catch (err) {
+      // EPERM means it's alive, we just aren't allowed to touch it.
+      return (err as NodeJS.ErrnoException).code === 'EPERM'
+    }
+  }
+
+  launchExecutable(executable: string): boolean {
+    try {
+      // Point Discord at the temp dir we watch, whatever TMPDIR we inherited.
+      const env = { ...process.env }
+
+      if (process.platform === 'darwin') {
+        // Spawning the .app binary directly just dies, so let `open` launch it.
+        const canonical = resolveDarwinTempDir()
+        if (canonical) env.TMPDIR = canonical
+
+        const appPath = executable.includes('.app/')
+          ? executable.slice(0, executable.indexOf('.app/') + '.app'.length)
+          : executable
+        const child = spawn('open', ['-a', appPath], { detached: true, stdio: 'ignore', env })
+        child.unref()
+        return true
+      }
+
+      const child = spawn(executable, [], { detached: true, stdio: 'ignore', env })
+      child.unref()
+      return true
+    } catch {
+      return false
+    }
+  }
+}
+
+// The pid holding the socket is usually a helper; walk up to the real app process.
+function resolveMainAppProcess(pid: number): ProcessInfo | null {
+  if (process.platform !== 'darwin') return null
+
+  const exe = executablePath(pid)
+  const bundle = bundleRoot(exe)
+  if (!bundle) return null
+
+  let mainPid = pid
+  let mainExe = exe
+  for (let depth = 0; depth < 20; depth++) {
+    const ppid = parentPid(mainPid)
+    if (ppid === null || ppid <= 1) break
+    const parentExe = executablePath(ppid)
+    if (bundleRoot(parentExe) !== bundle) break
+    mainPid = ppid
+    mainExe = parentExe
+  }
+
+  return { pid: mainPid, name: path.basename(mainExe ?? String(mainPid)), executable: mainExe }
+}
+
+function bundleRoot(exe: string | null): string | null {
+  if (!exe) return null
+  const idx = exe.indexOf('.app/Contents/')
+  return idx >= 0 ? exe.slice(0, idx + '.app'.length) : null
+}
+
+function parentPid(pid: number): number | null {
+  try {
+    const out = execFileSync('ps', ['-p', String(pid), '-o', 'ppid='], {
+      encoding: 'utf8',
+      timeout: 1000
+    }).trim()
+    const ppid = parseInt(out, 10)
+    return Number.isNaN(ppid) ? null : ppid
+  } catch {
+    return null
+  }
+}
+
+function executablePath(pid: number): string | null {
+  try {
+    if (process.platform === 'linux') {
+      return fs.readlinkSync(`/proc/${pid}/exe`)
+    }
+    if (process.platform === 'darwin') {
+      const out = execFileSync('ps', ['-p', String(pid), '-o', 'comm='], {
+        encoding: 'utf8',
+        timeout: 1000
+      }).trim()
+      return out || null
+    }
+  } catch {
+    return null
+  }
+  return null
 }
 
 function isSocketAlive(socketPath: string): Promise<boolean> {
@@ -176,7 +313,13 @@ function locateSocketOwnerMacOS(socketPath: string): ProcessInfo | null {
         currentName = line.slice(1)
       } else if (line.startsWith('n') && line.slice(1) === socketPath) {
         if (currentPid > 0 && currentPid !== process.pid) {
-          return { pid: currentPid, name: currentName }
+          return (
+            resolveMainAppProcess(currentPid) ?? {
+              pid: currentPid,
+              name: currentName,
+              executable: executablePath(currentPid)
+            }
+          )
         }
       }
     }
@@ -236,7 +379,8 @@ function findProcessForInodes(inodes: Set<string>): ProcessInfo | null {
         }
         const match = /^socket:\[(\d+)\]$/.exec(link)
         if (match && inodes.has(match[1])) {
-          return { pid: parseInt(pidStr, 10), name: processName(pidStr) }
+          const pid = parseInt(pidStr, 10)
+          return { pid, name: processName(pidStr), executable: executablePath(pid) }
         }
       }
     }
@@ -299,7 +443,7 @@ function findPeerProcess(localFd: number): ProcessInfo | null {
     if (fn(localFd, SOL_LOCAL, LOCAL_PEERPID, optval, optlen) !== 0) return null
     const pid = optval.readInt32LE(0)
     if (pid <= 0) return null
-    return { pid, name: macProcessName(pid) }
+    return { pid, name: macProcessName(pid), executable: executablePath(pid) }
   }
 
   const optval = Buffer.alloc(UCRED_SIZE)
@@ -311,7 +455,7 @@ function findPeerProcess(localFd: number): ProcessInfo | null {
   const pid = optval.readInt32LE(0)
   if (pid <= 0) return null
 
-  return { pid, name: processName(String(pid)) }
+  return { pid, name: processName(String(pid)), executable: executablePath(pid) }
 }
 
 function macProcessName(pid: number): string {

src/main/platform/types.ts

@@ -3,6 +3,7 @@ export const MAX_SOCKETS = 10
 export interface ProcessInfo {
   pid: number
   name: string
+  executable: string | null
 }
 
 export interface ClaimedSocket {
@@ -15,6 +16,8 @@ export interface RelayPlatform {
 
   fakeSocketPath(): string
 
+  ipcSocketPath(index: number): string
+
   removeFakeSocket(fakePath: string): void
 
   finalizeFakeSocket(fakePath: string): void
@@ -34,7 +37,15 @@ export interface RelayPlatform {
 
   isSocketAlive(socketPath: string): Promise<boolean>
 
+  removeStaleIpcSocket(index: number): Promise<void>
+
   getInstanceProcess(index: number): ProcessInfo | null
 
   getPeerProcess(fd: number): ProcessInfo | null
+
+  killProcess(pid: number): boolean
+
+  isProcessAlive(pid: number): boolean
+
+  launchExecutable(executable: string): boolean
 }

src/main/platform/unsupported.ts

@@ -9,6 +9,10 @@ export class UnsupportedPlatform implements RelayPlatform {
     throw NOT_SUPPORTED
   }
 
+  ipcSocketPath(): string {
+    throw NOT_SUPPORTED
+  }
+
   removeFakeSocket(): void {
     throw NOT_SUPPORTED
   }
@@ -45,6 +49,10 @@ export class UnsupportedPlatform implements RelayPlatform {
     return false
   }
 
+  async removeStaleIpcSocket(): Promise<void> {
+    throw NOT_SUPPORTED
+  }
+
   getInstanceProcess(): ProcessInfo | null {
     return null
   }
@@ -52,4 +60,16 @@ export class UnsupportedPlatform implements RelayPlatform {
   getPeerProcess(): ProcessInfo | null {
     return null
   }
+
+  killProcess(): boolean {
+    return false
+  }
+
+  isProcessAlive(): boolean {
+    return false
+  }
+
+  launchExecutable(): boolean {
+    return false
+  }
 }

src/main/relay.ts

@@ -11,6 +11,11 @@ const MIRROR_RECONNECT_DELAY_MS = 2000
 const SERVER_CLOSE_TIMEOUT_MS = 2000
 const ASSET_FETCH_RETRY_MS = 60_000
 
+const PROCESS_EXIT_TIMEOUT_MS = 8000
+const PROCESS_EXIT_POLL_MS = 200
+const SLOT_BIND_TIMEOUT_MS = 20_000
+const SLOT_BIND_POLL_MS = 300
+
 interface AppAsset {
   id: string
   type: number
@@ -46,6 +51,10 @@ async function getAppAssetMap(appId: string): Promise<Map<string, string>> {
   return map
 }
 
+function delay(ms: number): Promise<void> {
+  return new Promise((resolve) => setTimeout(resolve, ms))
+}
+
 function clearActivityPayload(pid: number): Buffer {
   return Buffer.from(
     JSON.stringify({ cmd: 'SET_ACTIVITY', args: { pid, activity: null }, nonce: randomUUID() }),
@@ -82,6 +91,7 @@ export interface RelayInstance {
   path: string
   isPrimary: boolean
   enabled: boolean
+  locked: boolean
   process: ProcessInfo | null
 }
 
@@ -132,6 +142,9 @@ export interface RelayStatus {
   instances: RelayInstance[]
   connectedClients: ConnectedClient[]
   blacklistedApps: BlacklistedApp[]
+  lockedPrimary: string | null
+  reordering: boolean
+  primaryOutOfOrder: boolean
   error: string | null
 }
 
@@ -166,15 +179,21 @@ export class RpcRelay extends EventEmitter {
   private fakeOwned = false
   private lastError: string | null = null
   private restarting = false
+  private lockedPrimary: string | null = null
+  private reordering = false
 
   getStatus(): RelayStatus {
-    const instances: RelayInstance[] = this.claimed.map(({ index, path: socketPath }, i) => ({
-      index,
-      path: socketPath,
-      isPrimary: i === 0,
-      enabled: i === 0 || !this.disabledMirrors.has(index),
-      process: platform.getInstanceProcess(index)
-    }))
+    const instances: RelayInstance[] = this.claimed.map(({ index, path: socketPath }, i) => {
+      const process = platform.getInstanceProcess(index)
+      return {
+        index,
+        path: socketPath,
+        isPrimary: i === 0,
+        enabled: i === 0 || !this.disabledMirrors.has(index),
+        locked: this.isLockedInstance(process),
+        process
+      }
+    })
 
     return {
       running: this.running,
@@ -189,10 +208,27 @@ export class RpcRelay extends EventEmitter {
         activity: s.activity
       })),
       blacklistedApps: this.getBlacklistedApps(),
+      lockedPrimary: this.lockedPrimary,
+      reordering: this.reordering,
+      primaryOutOfOrder: this.primaryOutOfOrder(instances),
       error: this.lastError
     }
   }
 
+  private isLockedInstance(process: ProcessInfo | null): boolean {
+    return (
+      this.lockedPrimary !== null &&
+      process?.executable != null &&
+      process.executable === this.lockedPrimary
+    )
+  }
+
+  private primaryOutOfOrder(instances: RelayInstance[]): boolean {
+    if (this.lockedPrimary === null) return false
+    const locked = instances.find((inst) => inst.locked)
+    return locked !== undefined && !locked.isPrimary
+  }
+
   setMirrorEnabled(index: number, enabled: boolean): RelayStatus {
     if (index === this.primaryIndex()) return this.getStatus()
 
@@ -214,6 +250,33 @@ export class RpcRelay extends EventEmitter {
     this.disabledMirrors = new Set(indices)
   }
 
+  getLockedPrimary(): string | null {
+    return this.lockedPrimary
+  }
+
+  setLockedPrimary(executable: string | null): void {
+    this.lockedPrimary = executable
+    this.emitStatus()
+  }
+
+  unlockPrimary(): RelayStatus {
+    this.lockedPrimary = null
+    this.emitStatus()
+    return this.getStatus()
+  }
+
+  async promoteToPrimary(index: number): Promise<RelayStatus> {
+    const process = platform.getInstanceProcess(index)
+    if (!process?.executable) {
+      this.lastError = 'Cannot resolve this Discord’s executable path'
+      this.emitStatus()
+      return this.getStatus()
+    }
+    this.lockedPrimary = process.executable
+    this.emitStatus()
+    return this.reorderForPrimary()
+  }
+
   getBlacklistedApps(): BlacklistedApp[] {
     return [...this.blacklistedApps].map(([id, name]) => ({ id, name }))
   }
@@ -588,6 +651,85 @@ export class RpcRelay extends EventEmitter {
     }
   }
 
+  private async reorderForPrimary(): Promise<RelayStatus> {
+    if (this.reordering) return this.getStatus()
+    if (this.lockedPrimary === null) return this.getStatus()
+
+    const lockedSlot = this.claimed.findIndex(
+      (c) => platform.getInstanceProcess(c.index)?.executable === this.lockedPrimary
+    )
+    if (lockedSlot < 0) {
+      this.lastError = 'Locked Discord is not currently running'
+      this.emitStatus()
+      return this.getStatus()
+    }
+    if (lockedSlot === 0) return this.getStatus()
+
+    this.reordering = true
+    this.lastError = null
+    this.emitStatus()
+
+    try {
+      // Grab what we need now before stop() wipes claimed below.
+      const others: string[] = []
+      const toKill: number[] = []
+      const freeIndices: number[] = []
+      for (let i = 0; i <= lockedSlot; i++) {
+        freeIndices.push(this.claimed[i].index)
+        const proc = platform.getInstanceProcess(this.claimed[i].index)
+        if (!proc) continue
+        toKill.push(proc.pid)
+        if (proc.executable && proc.executable !== this.lockedPrimary) {
+          others.push(proc.executable)
+        }
+      }
+      const lockedExecutable = this.lockedPrimary
+
+      await this.stop()
+
+      for (const pid of toKill) platform.killProcess(pid)
+      await this.waitForProcessesExit(toKill)
+
+      for (const index of freeIndices) {
+        await platform.removeStaleIpcSocket(index)
+      }
+
+      if (!platform.launchExecutable(lockedExecutable)) {
+        throw new Error('Failed to relaunch the locked Discord')
+      }
+      await this.waitForSlotBound(0)
+
+      for (const executable of others) platform.launchExecutable(executable)
+    } catch (err) {
+      this.lastError = err instanceof Error ? err.message : String(err)
+    } finally {
+      this.reordering = false
+      await this.start().catch((err) => {
+        this.lastError = err instanceof Error ? err.message : String(err)
+      })
+      this.emitStatus()
+    }
+
+    return this.getStatus()
+  }
+
+  private async waitForProcessesExit(pids: number[]): Promise<void> {
+    const deadline = Date.now() + PROCESS_EXIT_TIMEOUT_MS
+    while (Date.now() < deadline) {
+      if (pids.every((pid) => !platform.isProcessAlive(pid))) return
+      await delay(PROCESS_EXIT_POLL_MS)
+    }
+  }
+
+  private async waitForSlotBound(index: number): Promise<void> {
+    const deadline = Date.now() + SLOT_BIND_TIMEOUT_MS
+    while (Date.now() < deadline) {
+      if (await platform.isSocketAlive(platform.ipcSocketPath(index))) return
+      await delay(SLOT_BIND_POLL_MS)
+    }
+    throw new Error('Timed out waiting for the locked Discord to start')
+  }
+
   private mirrorFrame(session: ClientSession, frame: Frame): void {
     const payload = frame.op !== OP_HANDSHAKE ? parseFramePayload(frame) : null
     const isSetActivity = payload?.cmd === 'SET_ACTIVITY'

src/preload/index.ts

@@ -18,6 +18,9 @@ const api = {
     ipcRenderer.invoke('relay:set-mirror-enabled', index, enabled),
   setAppBlacklisted: (appId: string, blacklisted: boolean): Promise<RelayStatus> =>
     ipcRenderer.invoke('relay:set-app-blacklisted', appId, blacklisted),
+  unlockPrimary: (): Promise<RelayStatus> => ipcRenderer.invoke('relay:unlock-primary'),
+  promoteToPrimary: (index: number): Promise<RelayStatus> =>
+    ipcRenderer.invoke('relay:promote-to-primary', index),
   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

@@ -12,6 +12,9 @@ const EMPTY_STATUS: RelayStatus = {
   instances: [],
   connectedClients: [],
   blacklistedApps: [],
+  lockedPrimary: null,
+  reordering: false,
+  primaryOutOfOrder: false,
   error: null
 }
 
@@ -266,6 +269,14 @@ export function App(): React.JSX.Element {
     setStatus(await window.api.setAppBlacklisted(appId, blacklisted))
   }
 
+  const onUnlockPrimary = async (): Promise<void> => {
+    setStatus(await window.api.unlockPrimary())
+  }
+
+  const onPromote = async (index: number): Promise<void> => {
+    setStatus(await window.api.promoteToPrimary(index))
+  }
+
   const onToggleAutostart = async (enabled: boolean): Promise<void> => {
     setAutostart(await window.api.setAutostart(enabled))
   }
@@ -411,13 +422,22 @@ export function App(): React.JSX.Element {
               <InstanceRow
                 key={instance.index}
                 instance={instance}
+                reordering={status.reordering}
                 onToggleMirror={onToggleMirror}
+                onUnlock={onUnlockPrimary}
+                onPromote={onPromote}
               />
             ))
           ) : (
             <div className="text-zinc-500">No Discord instances detected</div>
           )}
         </div>
+
+        {status.reordering && (
+          <div className="mt-1 text-xs text-amber-300/90">
+            Restarting Discord clients to promote the new primary…
+          </div>
+        )}
       </section>
 
       <section className="rounded-xl bg-zinc-800/60 border border-zinc-700 p-4 flex flex-col gap-2">

src/renderer/src/components/InstanceRow.tsx

@@ -1,6 +1,7 @@
-import { Info } from 'lucide-react'
+import { ArrowUpToLine, Info, Lock } from 'lucide-react'
 import type { RelayInstance } from '../../../main/relay'
 import { Toggle } from './Toggle'
+import { Button } from './Button'
 
 function shortPath(p: string): string {
   return p.split('/').pop() ?? p
@@ -8,14 +9,54 @@ function shortPath(p: string): string {
 
 interface Props {
   instance: RelayInstance
+  reordering: boolean
   onToggleMirror: (index: number, enabled: boolean) => Promise<void>
+  onUnlock: () => Promise<void>
+  onPromote: (index: number) => Promise<void>
 }
 
-export function InstanceRow({ instance, onToggleMirror }: Props): React.JSX.Element {
+export function InstanceRow({
+  instance,
+  reordering,
+  onToggleMirror,
+  onUnlock,
+  onPromote
+}: Props): React.JSX.Element {
   const procLabel = instance.process
     ? `${instance.process.name} (pid ${instance.process.pid})`
     : 'unknown process'
 
+  const canPromote = instance.process?.executable != null
+
+  const promoteButton = (
+    <Button
+      variant="ghost"
+      className="p-1 shrink-0"
+      disabled={!canPromote || reordering}
+      onClick={() => onPromote(instance.index)}
+      aria-label="Promote to primary"
+      title={
+        !canPromote
+          ? 'Cannot resolve this Discord’s executable path'
+          : 'Make this Discord primary: restarts Discord clients so it starts first.'
+      }
+    >
+      <ArrowUpToLine className="w-4 h-4 text-emerald-400" />
+    </Button>
+  )
+
+  const unlockButton = (
+    <Button
+      variant="ghost"
+      className="p-1 shrink-0"
+      onClick={() => onUnlock()}
+      aria-label="Unlock primary"
+      title="Locked as primary. Click to unlock."
+    >
+      <Lock className="w-4 h-4 text-amber-400" />
+    </Button>
+  )
+
   const info = (
     <div className="flex flex-col">
       <div className="flex items-center gap-2">
@@ -29,6 +70,7 @@ export function InstanceRow({ instance, onToggleMirror }: Props): React.JSX.Elem
             mirror #{instance.index}
           </span>
         )}
+        {instance.locked && <span className="text-xs text-amber-400">locked</span>}
       </div>
       <span className="text-xs text-zinc-500">{procLabel}</span>
     </div>
@@ -38,14 +80,19 @@ export function InstanceRow({ instance, onToggleMirror }: Props): React.JSX.Elem
     return (
       <div className="flex items-center justify-between gap-2">
         {info}
-        <Info className="w-4 h-4 text-zinc-400 hover:text-zinc-100 cursor-help transition-colors">
-          <title>
-            The primary instance gets full passthrough and can&apos;t be turned off. It&apos;s
-            always the Discord instance that started first (discord-ipc-0). To make a different
-            instance primary, close this one first so the other claims that slot, then restart the
-            relay.
-          </title>
-        </Info>
+        <div className="flex items-center gap-1 shrink-0">
+          {instance.locked ? (
+            unlockButton
+          ) : (
+            <Info className="w-4 h-4 text-zinc-400 hover:text-zinc-100 cursor-help transition-colors">
+              <title>
+                The primary instance gets full passthrough and can&apos;t be turned off. It&apos;s
+                the Discord that started first (discord-ipc-0). Use Promote on another instance to
+                make it primary instead.
+              </title>
+            </Info>
+          )}
+        </div>
       </div>
     )
   }
@@ -53,10 +100,14 @@ export function InstanceRow({ instance, onToggleMirror }: Props): React.JSX.Elem
   return (
     <div className="flex items-center justify-between gap-2">
       {info}
-      <Toggle
-        checked={instance.enabled}
-        onChange={(checked) => onToggleMirror(instance.index, checked)}
-      />
+      <div className="flex items-center gap-1 shrink-0">
+        {instance.locked && unlockButton}
+        {promoteButton}
+        <Toggle
+          checked={instance.enabled}
+          onChange={(checked) => onToggleMirror(instance.index, checked)}
+        />
+      </div>
     </div>
   )
 }