diff --git a/src/cli/update-cli.test.ts b/src/cli/update-cli.test.ts
index 3a3434417e6..06a4e66e34a 100644
--- a/src/cli/update-cli.test.ts
+++ b/src/cli/update-cli.test.ts
@@ -824,6 +824,7 @@ describe("update-cli", () => {
     expect(call?.[2]?.env?.NODE_DISABLE_COMPILE_CACHE).toBe("1");
     expect(call?.[2]?.env?.OPENCLAW_UPDATE_POST_CORE).toBe("1");
     expect(call?.[2]?.env?.OPENCLAW_UPDATE_POST_CORE_CHANNEL).toBe("dev");
+    expect(call?.[2]?.env?.OPENCLAW_COMPATIBILITY_HOST_VERSION).toBe("1.0.0");
     expect(updateNpmInstalledPlugins).not.toHaveBeenCalled();
     expect(runDaemonInstall).not.toHaveBeenCalled();
     expect(runDaemonRestart).not.toHaveBeenCalled();
diff --git a/src/cli/update-cli/update-command.ts b/src/cli/update-cli/update-command.ts
index 7df3b7ecacb..3cff597d5e5 100644
--- a/src/cli/update-cli/update-command.ts
+++ b/src/cli/update-cli/update-command.ts
@@ -2678,6 +2678,7 @@ async function continuePostCoreUpdateInFreshProcess(params: {
   const resultPath = path.join(resultDir, "plugins.json");
   const installRecordsPath = path.join(resultDir, "plugin-install-records.json");
   const sourceConfigPath = path.join(resultDir, "source-config.json");
+  const postCoreHostVersion = await readPackageVersion(params.root);
 
   try {
     await writePostCorePluginInstallRecordsFile(installRecordsPath, params.pluginInstallRecords);
@@ -2695,6 +2696,9 @@ async function continuePostCoreUpdateInFreshProcess(params: {
         [POST_CORE_UPDATE_RESULT_PATH_ENV]: resultPath,
         [POST_CORE_UPDATE_INSTALL_RECORDS_PATH_ENV]: installRecordsPath,
         [POST_CORE_UPDATE_STARTED_AT_ENV]: String(params.updateStartedAtMs),
+        ...(postCoreHostVersion === null
+          ? {}
+          : { OPENCLAW_COMPATIBILITY_HOST_VERSION: postCoreHostVersion }),
         ...(params.preUpdateConfig
           ? { [POST_CORE_UPDATE_SOURCE_CONFIG_PATH_ENV]: sourceConfigPath }
           : {}),