fix(opencode): display proper session import errors (#36258)

packages/opencode/src/cli/cmd/import.ts

@@ -38,6 +38,17 @@ export function shouldAttachShareAuthHeaders(shareUrl: string, accountBaseUrl: s
   }
 }
 
+export function formatImportFileError(file: string, error: FSUtil.Error) {
+  if (error._tag === "PlatformError") {
+    if (error.reason._tag === "NotFound") return `File not found: ${file}`
+    if (error.reason._tag === "PermissionDenied") return `Failed to read file: Permission denied`
+    return `Failed to read file: ${error.message}`
+  }
+
+  const detail = error.cause instanceof Error ? error.cause.message : error.message
+  return `Invalid JSON in ${file}: ${detail}`
+}
+
 /**
  * Transform ShareNext API response (flat array) into the nested structure for local file storage.
  *
@@ -154,14 +165,9 @@ const runImport = Effect.fn("Cli.import.body")(function* (file: string, ctx: Ins
 
     exportData = transformed
   } else {
-    exportData = (yield* fs.readJson(file).pipe(Effect.orElseSucceed(() => undefined))) as
-      | NonNullable<typeof exportData>
-      | undefined
-    if (!exportData) {
-      process.stdout.write(`File not found: ${file}`)
-      process.stdout.write(EOL)
-      return
-    }
+    exportData = (yield* fs
+      .readJson(file)
+      .pipe(Effect.mapError((error) => new CliError({ message: formatImportFileError(file, error) })))) as ExportData
   }
 
   if (!exportData) {