diff --git a/CHANGELOG.md b/CHANGELOG.md
index da01774..a1103b3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,10 @@ All notable changes to the "python-ply-preview" extension will be documented in
 Check [Keep a Changelog](http://keepachangelog.com/) for recommendations on how to structure this file.
 
 
+### Unreleased
+
+  * Preview files left behind when VS Code was closed during a debug session are now removed after a day.
+
 ### 0.1.0
 
   * The PLY file is now written only when you click **View PLY**, not every time the cursor moves. This makes the debugger much more responsive with large point clouds.
diff --git a/src/ViewPLYService.ts b/src/ViewPLYService.ts
index ef64361..db5233a 100644
--- a/src/ViewPLYService.ts
+++ b/src/ViewPLYService.ts
@@ -17,6 +17,40 @@ and o.ndim in (2, 3) and (o.ndim == 2 or o.shape[0] == 1) and o.shape[-1] * o.sh
 and (o.shape[-1] in (3, 4, 6) or o.shape[-2] in (3, 4, 6))))\
 (type(o).__module__ or '', type(o).__name__))((${expression}))`;
 
+// --- Stale session cleanup ---
+
+/** Session folders untouched for this long are considered abandoned. */
+const STALE_SESSION_AGE_MS = 24 * 60 * 60 * 1000;
+
+/**
+ * Removes session folders in `baseDir` that were last modified more than `maxAgeMs` ago.
+ * Folders are normally removed when their debug session terminates, but they are left behind when
+ * VS Code exits while a session is still running. Returns the removed folders.
+ */
+export async function removeStaleSessionDirs(baseDir: string, maxAgeMs: number, now = Date.now()): Promise<string[]> {
+    let entries;
+    try {
+        entries = await fs.readdir(baseDir, { withFileTypes: true });
+    } catch {
+        // Nothing has been previewed in this workspace yet
+        return [];
+    }
+
+    const removed: string[] = [];
+    for (const entry of entries) {
+        if (!entry.isDirectory()) {
+            continue;
+        }
+        const dir = join(baseDir, entry.name);
+        const { mtimeMs } = await fs.stat(dir);
+        if (now - mtimeMs > maxAgeMs) {
+            await fs.rm(dir, { recursive: true, force: true });
+            removed.push(dir);
+        }
+    }
+    return removed;
+}
+
 // --- Service Class ---
 
 export default class ViewPLYService {
@@ -38,6 +72,10 @@ export default class ViewPLYService {
 
         this.logInfo(`Service initialized. Storage directory: ${this.baseStorageDir}`);
         vscode.debug.onDidTerminateDebugSession(this.cleanupSessionFiles.bind(this));
+
+        removeStaleSessionDirs(this.baseStorageDir, STALE_SESSION_AGE_MS)
+            .then(removed => removed.forEach(dir => this.logInfo(`Removed stale session directory: ${dir}`)))
+            .catch(error => this.logError('Error while removing stale session directories.', error));
     }
 
     /**
diff --git a/src/test/cleanup.test.ts b/src/test/cleanup.test.ts
new file mode 100644
index 0000000..10113b0
--- /dev/null
+++ b/src/test/cleanup.test.ts
@@ -0,0 +1,38 @@
+import * as assert from 'assert';
+import { existsSync, mkdirSync, mkdtempSync, utimesSync, writeFileSync } from 'fs';
+import { tmpdir } from 'os';
+import { join } from 'path';
+import { removeStaleSessionDirs } from '../ViewPLYService';
+
+const DAY_MS = 24 * 60 * 60 * 1000;
+
+function makeSessionDir(baseDir: string, name: string, ageMs: number): string {
+    const dir = join(baseDir, name);
+    mkdirSync(dir, { recursive: true });
+    writeFileSync(join(dir, 'cloud.ply'), 'ply\n');
+    const time = new Date(Date.now() - ageMs);
+    utimesSync(dir, time, time);
+    return dir;
+}
+
+suite('Stale session cleanup', () => {
+    test('removes only session folders older than the max age', async () => {
+        const baseDir = mkdtempSync(join(tmpdir(), 'viewply-'));
+        const stale = makeSessionDir(baseDir, 'stale-session', 2 * DAY_MS);
+        const fresh = makeSessionDir(baseDir, 'fresh-session', 60 * 1000);
+        writeFileSync(join(baseDir, 'not-a-session.txt'), '');
+
+        const removed = await removeStaleSessionDirs(baseDir, DAY_MS);
+
+        assert.deepStrictEqual(removed, [stale]);
+        assert.ok(!existsSync(stale));
+        assert.ok(existsSync(join(fresh, 'cloud.ply')));
+        assert.ok(existsSync(join(baseDir, 'not-a-session.txt')));
+    });
+
+    test('does nothing when the preview folder does not exist', async () => {
+        const removed = await removeStaleSessionDirs(join(tmpdir(), 'viewply-does-not-exist'), DAY_MS);
+
+        assert.deepStrictEqual(removed, []);
+    });
+});