feat: pre-warm environment manager caches during activation and background refresh

Author: eleanorjboyd

src/extension.ts

@@ -10,7 +10,7 @@ import {
     window,
 } from 'vscode';
 import { PythonEnvironment, PythonEnvironmentApi, PythonProjectCreator } from './api';
-import { ENVS_EXTENSION_ID } from './common/constants';
+import { ENVS_EXTENSION_ID, SYSTEM_MANAGER_ID, VENV_MANAGER_ID } from './common/constants';
 import { ensureCorrectVersion } from './common/extVersion';
 import { registerLogger, traceError, traceInfo, traceWarn } from './common/logging';
 import { clearPersistentState, setPersistentState } from './common/persistentState';
@@ -547,6 +547,18 @@ export async function activate(context: ExtensionContext): Promise<PythonEnviron
                 safeRegister('shellStartupVars', shellStartupVarsMgr.initialize()),
             ]);
 
+            // Pre-warm system and venv manager caches before initial environment selection.
+            await Promise.all([
+                envManagers
+                    .getEnvironmentManager(SYSTEM_MANAGER_ID)
+                    ?.getEnvironments('all')
+                    .catch(() => {}),
+                envManagers
+                    .getEnvironmentManager(VENV_MANAGER_ID)
+                    ?.getEnvironments('all')
+                    .catch(() => {}),
+            ]);
+
             await applyInitialEnvironmentSelection(envManagers, projectManager, nativeFinder, api);
 
             // Register manager-agnostic terminal watcher for package-modifying commands

src/managers/common/nativePythonFinder.ts

@@ -238,6 +238,11 @@ class NativePythonFinderImpl implements NativePythonFinder {
             1,
             'NativeRefresh-task',
         );
+
+        // Start discovery immediately so the cache is warm before managers call initialize().
+        void this.refresh(false).catch((err) => {
+            traceWarn('[pet] Background pre-warm refresh failed:', err);
+        });
     }
 
     public async resolve(executable: string): Promise<NativeEnvInfo> {