diff --git a/src/server/apps.ts b/src/server/apps.ts
index b19fee1..d388574 100644
--- a/src/server/apps.ts
+++ b/src/server/apps.ts
@@ -2,7 +2,7 @@ import type { App as SharedApp, AppState } from '@types'
 import type { ToesEvent, ToesEventInput, ToesEventType } from '../shared/events'
 import type { Subprocess } from 'bun'
 import { DEFAULT_EMOJI } from '@types'
-import { buildAppUrl } from '@urls'
+import { buildAppUrl, toSubdomain } from '@urls'
 import { appendFileSync, existsSync, mkdirSync, readdirSync, readFileSync, realpathSync, renameSync, symlinkSync, unlinkSync, writeFileSync } from 'fs'
 import { hostname } from 'os'
 import { join, resolve } from 'path'
@@ -60,6 +60,9 @@ export const allApps = (): App[] =>
 export const getApp = (dir: string): App | undefined =>
   _apps.get(dir)
 
+export const getAppBySubdomain = (subdomain: string): App | undefined =>
+  _apps.get(subdomain) ?? allApps().find(a => toSubdomain(a.name) === subdomain)
+
 export const runApps = () =>
   allAppDirs().filter(isApp).forEach(startApp)
 
diff --git a/src/server/mdns.ts b/src/server/mdns.ts
index ebdb186..e8a74a4 100644
--- a/src/server/mdns.ts
+++ b/src/server/mdns.ts
@@ -1,4 +1,5 @@
 import type { Subprocess } from 'bun'
+import { toSubdomain } from '@urls'
 import { networkInterfaces } from 'os'
 import { hostLog } from './tui'
 
@@ -40,7 +41,7 @@ export function publishApp(name: string) {
     return
   }
 
-  const hostname = `${name}.toes.local`
+  const hostname = `${toSubdomain(name)}.toes.local`
 
   try {
     const proc = Bun.spawn(['avahi-publish', '-a', hostname, '-R', ip], {
@@ -67,7 +68,7 @@ export function unpublishApp(name: string) {
 
   proc.kill()
   _publishers.delete(name)
-  hostLog(`mDNS: unpublished ${name}.toes.local`)
+  hostLog(`mDNS: unpublished ${toSubdomain(name)}.toes.local`)
 }
 
 export function unpublishAll() {
@@ -75,7 +76,7 @@ export function unpublishAll() {
 
   for (const [name, proc] of _publishers) {
     proc.kill()
-    hostLog(`mDNS: unpublished ${name}.toes.local`)
+    hostLog(`mDNS: unpublished ${toSubdomain(name)}.toes.local`)
   }
   _publishers.clear()
 }
diff --git a/src/server/proxy.ts b/src/server/proxy.ts
index fbe522b..881ac47 100644
--- a/src/server/proxy.ts
+++ b/src/server/proxy.ts
@@ -1,5 +1,5 @@
 import type { Server, ServerWebSocket } from 'bun'
-import { getApp } from '$apps'
+import { getAppBySubdomain } from '$apps'
 
 export type { WsData }
 
@@ -34,7 +34,7 @@ export function extractSubdomain(host: string): string | null {
 }
 
 export async function proxySubdomain(subdomain: string, req: Request): Promise<Response> {
-  const app = getApp(subdomain)
+  const app = getAppBySubdomain(subdomain)
 
   if (!app || app.state !== 'running' || !app.port) {
     return new Response(`App "${subdomain}" not found or not running`, { status: 502 })
@@ -66,7 +66,7 @@ export async function proxySubdomain(subdomain: string, req: Request): Promise<R
 }
 
 export function proxyWebSocket(subdomain: string, req: Request, server: Server<WsData>): Response | undefined {
-  const app = getApp(subdomain)
+  const app = getAppBySubdomain(subdomain)
 
   if (!app || app.state !== 'running' || !app.port) {
     return new Response(`App "${subdomain}" not found or not running`, { status: 502 })
diff --git a/src/shared/urls.test.ts b/src/shared/urls.test.ts
new file mode 100644
index 0000000..3b85702
--- /dev/null
+++ b/src/shared/urls.test.ts
@@ -0,0 +1,44 @@
+import { describe, expect, test } from 'bun:test'
+import { buildAppUrl, toSubdomain } from './urls'
+
+describe('toSubdomain', () => {
+  test('passes through clean names', () => {
+    expect(toSubdomain('clock')).toBe('clock')
+    expect(toSubdomain('my-app')).toBe('my-app')
+  })
+
+  test('replaces dots with hyphens', () => {
+    expect(toSubdomain('mcp.txt')).toBe('mcp-txt')
+    expect(toSubdomain('my.cool.app')).toBe('my-cool-app')
+  })
+
+  test('replaces underscores with hyphens', () => {
+    expect(toSubdomain('my_app')).toBe('my-app')
+  })
+
+  test('collapses multiple hyphens', () => {
+    expect(toSubdomain('my--app')).toBe('my-app')
+    expect(toSubdomain('a..b')).toBe('a-b')
+  })
+
+  test('strips leading and trailing hyphens', () => {
+    expect(toSubdomain('.hidden')).toBe('hidden')
+    expect(toSubdomain('trailing.')).toBe('trailing')
+    expect(toSubdomain('-dashed-')).toBe('dashed')
+  })
+
+  test('lowercases', () => {
+    expect(toSubdomain('MyApp')).toBe('myapp')
+  })
+})
+
+describe('buildAppUrl', () => {
+  test('prepends sanitized name as subdomain', () => {
+    expect(buildAppUrl('clock', 'http://toes.local')).toBe('http://clock.toes.local')
+    expect(buildAppUrl('mcp.txt', 'http://toes.local')).toBe('http://mcp-txt.toes.local')
+  })
+
+  test('works with localhost and port', () => {
+    expect(buildAppUrl('my-app', 'http://localhost:3000')).toBe('http://my-app.localhost:3000')
+  })
+})
diff --git a/src/shared/urls.ts b/src/shared/urls.ts
index 11de449..fdc20ce 100644
--- a/src/shared/urls.ts
+++ b/src/shared/urls.ts
@@ -1,5 +1,8 @@
+export const toSubdomain = (name: string): string =>
+  name.toLowerCase().replace(/[^a-z0-9-]/g, '-').replace(/-+/g, '-').replace(/^-|-$/g, '')
+
 export function buildAppUrl(appName: string, baseUrl: string): string {
   const url = new URL(baseUrl)
-  url.hostname = `${appName}.${url.hostname}`
+  url.hostname = `${toSubdomain(appName)}.${url.hostname}`
   return url.origin
 }