diff --git a/src/test/integration/packageManagerRoundtrip.integration.test.ts b/src/test/integration/packageManagerRoundtrip.integration.test.ts
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+++ b/src/test/integration/packageManagerRoundtrip.integration.test.ts
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+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+/**
+ * Integration Test: Package Manager Roundtrip
+ *
+ * PURPOSE:
+ * Verify that every discovered package manager performs a full package lifecycle
+ * correctly, using only the public extension API. The test is parametrized over
+ * the package managers backing the discovered environments, so new managers are
+ * covered automatically without adding manager-specific code.
+ *
+ * ROUNDTRIP (per manager, all via the public API):
+ *   1. list packages           -> getPackages (baseline; test package absent)
+ *   2. install test package    -> managePackages({ install })
+ *   3. list again              -> getPackages (test package now present)
+ *   4. list direct packages    -> getPackages filtered by !isTransitive
+ *   5. uninstall test package  -> managePackages({ uninstall })
+ *   6. list again              -> getPackages (test package absent again)
+ *
+ * NOTES:
+ *   - "Available versions" is intentionally NOT exercised here: the exported
+ *     PythonEnvironmentApi does not surface getPackageAvailableVersions (it lives
+ *     only on the internal PackageManager interface), so it is unreachable from a
+ *     public-API-only test.
+ *   - Direct (non-transitive) packages are derived from Package.isTransitive,
+ *     which IS part of the public API.
+ *   - The test package (cowsay) is small and dependency-free so a successful
+ *     install shows up as a direct package with no transitive fan-out.
+ */
+
+import * as assert from 'assert';
+import * as vscode from 'vscode';
+import { Package, PythonEnvironment, PythonEnvironmentApi } from '../../api';
+import { normalizePackageName } from '../../managers/builtin/utils';
+import { ENVS_EXTENSION_ID } from '../constants';
+import { waitForCondition } from '../testUtils';
+
+/** Small, dependency-free package used for the install/uninstall roundtrip. */
+const TEST_PACKAGE = 'cowsay';
+
+/** True when a package with the given (normalized) name is in the list. */
+function hasPackage(packages: Package[] | undefined, name: string): boolean {
+    const target = normalizePackageName(name);
+    return (packages ?? []).some((p) => normalizePackageName(p.name) === target);
+}
+
+/**
+ * Runs the full lifecycle roundtrip for a single environment/manager.
+ * Returns undefined on success, or a human-readable skip reason.
+ */
+async function runRoundtrip(api: PythonEnvironmentApi, env: PythonEnvironment, managerId: string): Promise<void> {
+    const baseline = await api.getPackages(env, { skipCache: true });
+    if (baseline === undefined) {
+        // No usable package manager for this environment.
+        return;
+    }
+
+    // Avoid clobbering a pre-existing install of the test package.
+    assert.ok(
+        !hasPackage(baseline, TEST_PACKAGE),
+        `[${managerId}] ${TEST_PACKAGE} unexpectedly already installed; cannot run a clean roundtrip`,
+    );
+
+    let installed = false;
+    try {
+        // 2. Install.
+        await api.managePackages(env, { install: [TEST_PACKAGE] });
+        installed = true;
+
+        // 3. List again -> present.
+        await api.refreshPackages(env);
+        const afterInstall = await api.getPackages(env, { skipCache: true });
+        assert.ok(hasPackage(afterInstall, TEST_PACKAGE), `[${managerId}] ${TEST_PACKAGE} should be installed`);
+
+        // 4. Direct (non-transitive) packages should include the directly-installed package.
+        const direct = (afterInstall ?? []).filter((p) => p.isTransitive !== true);
+        assert.ok(
+            hasPackage(direct, TEST_PACKAGE),
+            `[${managerId}] ${TEST_PACKAGE} should be reported as a direct (non-transitive) package`,
+        );
+
+        // 5. Uninstall.
+        await api.managePackages(env, { uninstall: [TEST_PACKAGE] });
+        installed = false;
+
+        // 6. List again -> absent.
+        await api.refreshPackages(env);
+        const afterUninstall = await api.getPackages(env, { skipCache: true });
+        assert.ok(!hasPackage(afterUninstall, TEST_PACKAGE), `[${managerId}] ${TEST_PACKAGE} should be uninstalled`);
+    } finally {
+        // Best-effort cleanup so a mid-roundtrip failure never leaves the env dirty.
+        if (installed) {
+            try {
+                await api.managePackages(env, { uninstall: [TEST_PACKAGE] });
+            } catch {
+                console.log(`[${managerId}] cleanup: failed to uninstall ${TEST_PACKAGE}`);
+            }
+        }
+    }
+}
+
+suite('Integration: Package Manager Roundtrip', function () {
+    this.timeout(180_000); // Install/uninstall across multiple managers can be slow.
+
+    let api: PythonEnvironmentApi;
+
+    suiteSetup(async function () {
+        this.timeout(30_000);
+
+        const extension = vscode.extensions.getExtension(ENVS_EXTENSION_ID);
+        assert.ok(extension, `Extension ${ENVS_EXTENSION_ID} not found`);
+
+        if (!extension.isActive) {
+            await extension.activate();
+            await waitForCondition(() => extension.isActive, 20_000, 'Extension did not activate');
+        }
+
+        api = extension.exports as PythonEnvironmentApi;
+        assert.ok(api, 'API not available');
+    });
+
+    /**
+     * Picks one representative environment per package manager, grouped by managerId.
+     * Prefers virtual-environment-like envs, which are safe to install into.
+     */
+    async function getEnvironmentsByManager(): Promise<Map<string, PythonEnvironment>> {
+        const environments = await api.getEnvironments('all');
+        const byManager = new Map<string, PythonEnvironment>();
+
+        const looksModifiable = (env: PythonEnvironment): boolean =>
+            env.displayName.includes('venv') ||
+            env.displayName.includes('.venv') ||
+            env.envId.managerId.includes('venv');
+
+        for (const env of environments) {
+            const managerId = env.envId.managerId;
+            const current = byManager.get(managerId);
+            if (!current || (looksModifiable(env) && !looksModifiable(current))) {
+                byManager.set(managerId, env);
+            }
+        }
+        return byManager;
+    }
+
+    /**
+     * Parametrized roundtrip: one assertion pass per discovered package manager.
+     *
+     * This is a single test that iterates managers (rather than a static list) so
+     * that any future manager is exercised automatically once its environments are
+     * discovered. Failures are aggregated and reported per manager.
+     */
+    test('install/list/direct/uninstall roundtrip for each package manager', async function () {
+        const byManager = await getEnvironmentsByManager();
+
+        if (byManager.size === 0) {
+            console.log('No environments discovered; skipping package manager roundtrip');
+            this.skip();
+            return;
+        }
+
+        const failures: string[] = [];
+        let exercised = 0;
+
+        for (const [managerId, env] of byManager) {
+            try {
+                const before = await api.getPackages(env, { skipCache: true });
+                if (before === undefined) {
+                    console.log(`[${managerId}] no package manager available; skipping`);
+                    continue;
+                }
+                if (hasPackage(before, TEST_PACKAGE)) {
+                    console.log(`[${managerId}] ${TEST_PACKAGE} already present; skipping to avoid clobbering`);
+                    continue;
+                }
+
+                await runRoundtrip(api, env, managerId);
+                exercised++;
+                console.log(`[${managerId}] roundtrip passed (${env.displayName})`);
+            } catch (e) {
+                failures.push(`[${managerId}] ${e instanceof Error ? e.message : String(e)}`);
+            }
+        }
+
+        assert.strictEqual(failures.length, 0, `Package manager roundtrip failures:\n${failures.join('\n')}`);
+
+        if (exercised === 0) {
+            console.log('No modifiable package managers were exercised; skipping');
+            this.skip();
+        }
+    });
+});