fix(oc-path): report UTF-8 byte counts in set command output (#104496)

* fix(oc-path): report UTF-8 byte counts in set command output

Use Buffer.byteLength(newBytes, 'utf8') instead of string.length
for bytesWritten and dry-run byte reports. JavaScript's string.length
counts UTF-16 code units which undercounts multi-byte characters
when writing UTF-8 files.

Co-Authored-By: Claude <noreply@anthropic.com>

* test(oc-path): cover human UTF-8 dry-run count

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Peter Steinberger <steipete@gmail.com>

extensions/oc-path/src/cli.test.ts

@@ -169,6 +169,26 @@ describe("openclaw path CLI", () => {
       expect(readFileSync(filePath, "utf-8")).toBe(before);
     });
 
+    it("CLI-S02b --dry-run human output reports the rendered UTF-8 byte count", async () => {
+      const filePath = join(workspaceDir, "gateway.jsonc");
+      const before = '{ "version": "1.0" }';
+      writeFileSync(filePath, before, "utf-8");
+      const rt = createTestRuntime();
+      await pathSetCommand(
+        "oc://gateway.jsonc/version",
+        "中文",
+        { cwd: workspaceDir, human: true, dryRun: true },
+        rt,
+      );
+
+      const [header, ...bodyLines] = stdoutText(rt).split("\n");
+      const body = bodyLines.join("\n");
+      expect(header).toBe(
+        `--dry-run: would write ${Buffer.byteLength(body, "utf8")} bytes to ${filePath}`,
+      );
+      expect(readFileSync(filePath, "utf-8")).toBe(before);
+    });
+
     it("CLI-S05 --dry-run --diff prints a unified diff", async () => {
       const filePath = join(workspaceDir, "gateway.jsonc");
       const before = '{\n  "version": "1.0",\n  "enabled": true\n}\n';
@@ -414,6 +434,29 @@ describe("openclaw path CLI", () => {
       expect(out.bytes).toBe(before);
     });
 
+    it("CLI-S07b reports accurate UTF-8 byte counts for multibyte set output", async () => {
+      const filePath = join(workspaceDir, "gateway.jsonc");
+      const before = '{\n  "version": "1.0"\n}\n';
+      writeFileSync(filePath, before, "utf-8");
+      // Replace the whole file with CJK content via the version key.
+      // CJK chars are 1 UTF-16 unit but 3 UTF-8 bytes.
+      const cjkValue = "中".repeat(30);
+      const rt = createTestRuntime();
+      await pathSetCommand(
+        "oc://gateway.jsonc/version",
+        cjkValue,
+        { cwd: workspaceDir, json: true },
+        rt,
+      );
+      expect(rt.exitCode).toBe(0);
+      const out = JSON.parse(stdoutText(rt));
+      // bytesWritten must match the file's actual UTF-8 byte size on disk
+      const onDisk = readFileSync(filePath, "utf-8");
+      expect(out.bytesWritten).toBe(Buffer.byteLength(onDisk, "utf8"));
+      // bytesWritten exceeds JS string length (50 UTF-16 units < ~110 UTF-8 bytes)
+      expect(out.bytesWritten).toBeGreaterThan(onDisk.length);
+    });
+
     it("CLI-E03 emit --cwd resolves <file> against the supplied directory", async () => {
       // Closes round-10 finding F2: emit advertises --cwd / --file in
       // the docs but the handler resolved <file> against process.cwd()

extensions/oc-path/src/cli.ts

@@ -358,6 +358,8 @@ export async function pathSetCommand(
     return;
   }
 
+  const byteLength = Buffer.byteLength(newBytes, "utf8");
+
   if (options.dryRun === true) {
     const diff = options.diff === true ? formatUnifiedDiff(oldBytes, newBytes, fsPath) : undefined;
     emit(
@@ -367,7 +369,7 @@ export async function pathSetCommand(
       () =>
         diff !== undefined
           ? diff || `--dry-run: no byte changes for ${fsPath}`
-          : `--dry-run: would write ${newBytes.length} bytes to ${fsPath}\n${newBytes}`,
+          : `--dry-run: would write ${byteLength} bytes to ${fsPath}\n${newBytes}`,
     );
     return;
   }
@@ -375,8 +377,8 @@ export async function pathSetCommand(
   emit(
     runtime,
     mode,
-    { ok: true, dryRun: false, bytesWritten: newBytes.length, fsPath },
-    () => `wrote ${newBytes.length} bytes to ${fsPath}`,
+    { ok: true, dryRun: false, bytesWritten: byteLength, fsPath },
+    () => `wrote ${byteLength} bytes to ${fsPath}`,
   );
 }