fix: harden operations and configuration recovery

internal/shell/shell.go

@@ -323,8 +323,19 @@ func (a *Adapter) disable() error {
 	if metadata.OriginalScript != nil {
 		restored = []byte(*metadata.OriginalScript)
 	}
-	if err := a.writeOwned(a.configuration.EnvironmentFile, restored); err != nil {
-		return fmt.Errorf("restore Shell environment: %w", err)
+	current, err := a.files.ReadFile(a.configuration.EnvironmentFile)
+	if err != nil {
+		return fmt.Errorf("read managed Shell environment before restore: %w", err)
+	}
+	switch currentFingerprint := fingerprint(current); currentFingerprint {
+	case fingerprint(restored):
+		// A previous recovery completed the file write but not metadata cleanup.
+	case metadata.Fingerprint:
+		if err := a.writeOwned(a.configuration.EnvironmentFile, restored); err != nil {
+			return fmt.Errorf("restore Shell environment: %w", err)
+		}
+	default:
+		return errors.New("Shell environment changed after proxyctl applied it; refusing to overwrite current configuration or discard recovery metadata")
 	}
 	if err := a.files.Remove(a.configuration.RecoveryFile); err != nil && !errors.Is(err, fs.ErrNotExist) {
 		return fmt.Errorf("remove Shell recovery metadata after environment changed: %w", err)

internal/shell/shell_test.go

@@ -296,6 +296,27 @@ func TestShellTargetContract(t *testing.T) {
 				assertState(t, a, activeProfile(), target.Drifted)
 			})
 
+			t.Run("drifted-environment-refuses-destructive-restore", func(t *testing.T) {
+				a := newAdapter(t, shellName, nil)
+				if result := a.SetDesired(context.Background(), true, activeProfile()); result.Err != nil {
+					t.Fatal(result.Err)
+				}
+				changed := "export HTTP_PROXY='http://user-change.example:8080'\n"
+				if err := os.WriteFile(a.EnvironmentPath(), []byte(changed), 0o600); err != nil {
+					t.Fatal(err)
+				}
+				result := a.SetDesired(context.Background(), false, nil)
+				if result.Err == nil || result.Inspection.State != target.Drifted {
+					t.Fatalf("unsafe restore = %#v", result)
+				}
+				if got := readFile(t, a.EnvironmentPath()); got != changed {
+					t.Fatalf("drifted environment overwritten:\n%s", got)
+				}
+				if _, err := os.Stat(a.RecoveryPath()); err != nil {
+					t.Fatalf("recovery metadata removed after refused restore: %v", err)
+				}
+			})
+
 			t.Run("validation-and-redaction", func(t *testing.T) {
 				fs := &failingFS{FileSystem: shell.OSFileSystem{}, failWrite: true}
 				a := newAdapterWithFS(t, shellName, nil, fs)