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) {

packages/opencode/test/cli/import.test.ts

@@ -1,10 +1,46 @@
 import { test, expect } from "bun:test"
 import {
+  formatImportFileError,
   parseShareUrl,
   shouldAttachShareAuthHeaders,
   transformShareData,
   type ShareData,
 } from "../../src/cli/cmd/import"
+import { FSUtil } from "@opencode-ai/core/fs-util"
+import { PlatformError } from "effect"
+
+test("formats import file errors", () => {
+  expect(
+    formatImportFileError(
+      "test.json",
+      new PlatformError.PlatformError(
+        new PlatformError.SystemError({
+          _tag: "NotFound",
+          module: "FileSystem",
+          method: "readFileString",
+        }),
+      ),
+    ),
+  ).toBe("File not found: test.json")
+  expect(
+    formatImportFileError(
+      "test.json",
+      new PlatformError.PlatformError(
+        new PlatformError.SystemError({
+          _tag: "PermissionDenied",
+          module: "FileSystem",
+          method: "readFileString",
+        }),
+      ),
+    ),
+  ).toBe("Failed to read file: Permission denied")
+  expect(
+    formatImportFileError(
+      "test.json",
+      new FSUtil.FileSystemError({ method: "readJson", cause: new SyntaxError("Unexpected token") }),
+    ),
+  ).toBe("Invalid JSON in test.json: Unexpected token")
+})
 
 // parseShareUrl tests
 test("parses valid share URLs", () => {