diff --git a/src/client/lang.ts b/src/client/lang.ts
index e9460ca..8e7dc40 100644
--- a/src/client/lang.ts
+++ b/src/client/lang.ts
@@ -23,6 +23,8 @@ import { toml } from '@codemirror/legacy-modes/mode/toml'
 import { nginx } from '@codemirror/legacy-modes/mode/nginx'
 import { dockerFile } from '@codemirror/legacy-modes/mode/dockerfile'
 import { properties } from '@codemirror/legacy-modes/mode/properties'
+import { csharp, kotlin } from '@codemirror/legacy-modes/mode/clike'
+import { swift } from '@codemirror/legacy-modes/mode/swift'
 
 /** The lowercased file extension of a path ('' when none). */
 export function extOf(path: string): string {
@@ -48,6 +50,9 @@ export function languageKeyForExt(ext: string): string | null {
     case 'yaml': case 'yml': return 'yaml'
     case 'sql': return 'sql'
     case 'java': return 'java'
+    case 'cs': return 'csharp'
+    case 'kt': case 'kts': return 'kotlin'
+    case 'swift': return 'swift'
     case 'c': case 'h': return 'c'
     case 'cc': case 'cpp': case 'cxx': case 'hpp': case 'hh': case 'hxx': return 'cpp'
     case 'rs': return 'rust'
@@ -76,6 +81,9 @@ const FACTORIES: Record<string, () => Language | LanguageSupport> = {
   yaml: () => yaml(),
   sql: () => sql(),
   java: () => java(),
+  csharp: () => StreamLanguage.define(csharp),
+  kotlin: () => StreamLanguage.define(kotlin),
+  swift: () => StreamLanguage.define(swift),
   c: () => cpp(),
   cpp: () => cpp(),
   rust: () => rust(),
diff --git a/tests/smoke.spec.ts b/tests/smoke.spec.ts
index d92cb77..d5a1cf2 100644
--- a/tests/smoke.spec.ts
+++ b/tests/smoke.spec.ts
@@ -12,7 +12,7 @@ import { SettingsConflictError, settingsNamespace } from '@deepseek-ai/dsh-setti
 import { apply, mediaTypeForPath } from '../src/index.ts'
 import * as git from '../src/git.ts'
 import { listDirectory } from '../src/fs-tree.ts'
-import { defaultShell, PtyManager } from '../src/pty-manager.ts'
+import { defaultShell, PtyManager, type SidebarPty } from '../src/pty-manager.ts'
 import type { SidebarWebRoute, SidebarWebUpgradeRoute } from '../src/context-types.ts'
 
 interface FakeContext {
@@ -31,6 +31,32 @@ interface FakeContext {
   get: (key: string) => undefined
 }
 
+/**
+ * The login-shell test spawns a real pty whose bash may still be writing to
+ * the temp HOME (history files, etc.) when `disposeAll()` returns — `close()`
+ * only requests the kill and the process exit lands asynchronously in
+ * `onExit`. Deleting the directory immediately then races the shell and
+ * fails with ENOTEMPTY on CI. Wait for the spawned handle to report `exited`
+ * (bounded), then remove with a short retry loop as a belt-and-braces
+ * fallback for any straggler fd.
+ */
+async function rmTempDirAfterPtyExit(handle: { exited: boolean }, dir: string): Promise<void> {
+  const deadline = Date.now() + 2000
+  while (Date.now() < deadline && !handle.exited) {
+    await new Promise((resolve) => setTimeout(resolve, 50))
+  }
+  for (let attempt = 0; ; attempt++) {
+    try {
+      rmSync(dir, { recursive: true, force: true })
+      return
+    } catch (error) {
+      const busy = (error as NodeJS.ErrnoException).code === 'ENOTEMPTY' || (error as NodeJS.ErrnoException).code === 'EBUSY'
+      if (!busy || attempt >= 4) throw error
+      await new Promise((resolve) => setTimeout(resolve, 100 * (attempt + 1)))
+    }
+  }
+}
+
 describe('host plugin smoke', () => {
   it('serves PDF with the browser-native content type', () => {
     expect(mediaTypeForPath('/work/report.PDF')).toBe('application/pdf')
@@ -191,6 +217,7 @@ describe('host plugin smoke', () => {
   it.skipIf(process.platform === 'win32')('spawns the shell as a login shell (loads ~/.profile)', async () => {
     const home = mkdtempSync(join(tmpdir(), 'dsh-sidebar-login-'))
     const previousHome = process.env.HOME
+    let handle: SidebarPty | undefined
     try {
       // A login bash reads ~/.profile (a non-login interactive bash reads
       // ~/.bashrc instead), so this marker proves the spawn used a login
@@ -199,7 +226,7 @@ describe('host plugin smoke', () => {
       process.env.HOME = home
       const manager = new PtyManager('/bin/bash', 3)
       try {
-        const handle = manager.open('s5', 't1', process.cwd(), 80, 24)
+        handle = manager.open('s5', 't1', process.cwd(), 80, 24)
         handle.pty.write('echo $DSH_LOGIN_MARKER\r')
         const deadline = Date.now() + 5000
         while (!handle.transcript.includes('loaded-from-profile') && Date.now() < deadline) {
@@ -212,7 +239,7 @@ describe('host plugin smoke', () => {
     } finally {
       if (previousHome === undefined) delete process.env.HOME
       else process.env.HOME = previousHome
-      rmSync(home, { recursive: true, force: true })
+      await rmTempDirAfterPtyExit(handle ?? { exited: true }, home)
     }
   })
 
diff --git a/tests/unit.spec.ts b/tests/unit.spec.ts
index 1cccf71..7c3c0c6 100644
--- a/tests/unit.spec.ts
+++ b/tests/unit.spec.ts
@@ -1102,6 +1102,9 @@ describe('editor language mapping', () => {
     expect(languageKeyForExt('yaml')).toBe('yaml')
     expect(languageKeyForExt('sh')).toBe('shell')
     expect(languageKeyForExt('md')).toBe('md')
+    expect(languageKeyForExt('cs')).toBe('csharp')
+    expect(languageKeyForExt('kt')).toBe('kotlin')
+    expect(languageKeyForExt('swift')).toBe('swift')
     expect(languageKeyForExt('txt')).toBeNull()
     expect(languageKeyForExt('log')).toBeNull()
     expect(languageKeyForExt('')).toBeNull()