fix: preserve internal env vars during /init EnvVars replacement

The EnvVars replace logic in SetData was deleting all keys from
a.defaults.EnvVars that weren't present in the incoming customer
config, including internal system vars like E2B_SANDBOX (set at
startup), E2B_SANDBOX_ID, E2B_TEMPLATE_ID (set by MMDS polling),
and E2B_EVENTS_ADDRESS (set by SetupHyperloop).

Added isInternalEnvVar() helper to exclude these system-managed
keys from deletion during the replace operation, ensuring they
persist across /init calls.

Author: cursoragent

packages/envd/internal/api/init.go

@@ -188,8 +188,9 @@ func (a *API) SetData(ctx context.Context, logger zerolog.Logger, data PostInitJ
 
 		// Replace, not merge: drop keys that are no longer present so a customer
 		// who removes a variable from their config sees it actually removed.
+		// Exclude internal env vars that are managed by the system.
 		a.defaults.EnvVars.Range(func(key, _ string) bool {
-			if _, keep := newVars[key]; !keep {
+			if _, keep := newVars[key]; !keep && !isInternalEnvVar(key) {
 				a.defaults.EnvVars.Delete(key)
 			}
 
@@ -397,6 +398,17 @@ func asString(v any) string {
 	return s
 }
 
+// isInternalEnvVar returns true for env vars that are managed by the system
+// and should not be deleted when customer env vars are replaced.
+func isInternalEnvVar(key string) bool {
+	switch key {
+	case "E2B_SANDBOX", "E2B_SANDBOX_ID", "E2B_TEMPLATE_ID", "E2B_EVENTS_ADDRESS":
+		return true
+	default:
+		return false
+	}
+}
+
 func (a *API) SetupHyperloop(address string) {
 	a.hyperloopLock.Lock()
 	defer a.hyperloopLock.Unlock()