diff --git a/scripts/postinstall.js b/scripts/postinstall.js
index e5adce74e7..1fb82ca99f 100644
--- a/scripts/postinstall.js
+++ b/scripts/postinstall.js
@@ -293,13 +293,13 @@ function trySetupCompletion(repoRoot) {
   try {
     // Run with OPENCLAW_SKIP_POSTINSTALL to avoid any weird recursion,
     // though distinct from this script.
-    spawnSync(process.execPath, [binPath, "completion", "--install", "--yes"], {
+    spawnSync(process.execPath, [binPath, "completion", "--install", "--yes", "--write-state"], {
       cwd: repoRoot,
       stdio: "inherit",
       env: { ...process.env, OPENCLAW_SKIP_POSTINSTALL: "1" },
     });
   } catch {
-    // Ignore errors to not break install
+    // Ignore errors
   }
 }
 
diff --git a/src/cli/update-cli.ts b/src/cli/update-cli.ts
index d7cd94375e..bf7c9bc4d2 100644
--- a/src/cli/update-cli.ts
+++ b/src/cli/update-cli.ts
@@ -1,5 +1,6 @@
 import type { Command } from "commander";
 import { confirm, isCancel, select, spinner } from "@clack/prompts";
+import { spawnSync } from "node:child_process";
 import fs from "node:fs/promises";
 import os from "node:os";
 import path from "node:path";
@@ -200,6 +201,29 @@ async function pathExists(targetPath: string): Promise<boolean> {
   }
 }
 
+async function tryWriteCompletionCache(root: string, jsonMode: boolean): Promise<void> {
+  const binPath = path.join(root, "openclaw.mjs");
+  if (!(await pathExists(binPath))) {
+    return;
+  }
+  const result = spawnSync(resolveNodeRunner(), [binPath, "completion", "--write-state"], {
+    cwd: root,
+    env: { ...process.env, OPENCLAW_SKIP_POSTINSTALL: "1" },
+    encoding: "utf-8",
+  });
+  if (result.error) {
+    if (!jsonMode) {
+      defaultRuntime.log(theme.warn(`Completion cache update failed: ${String(result.error)}`));
+    }
+    return;
+  }
+  if (result.status !== 0 && !jsonMode) {
+    const stderr = (result.stderr ?? "").toString().trim();
+    const detail = stderr ? ` (${stderr})` : "";
+    defaultRuntime.log(theme.warn(`Completion cache update failed${detail}.`));
+  }
+}
+
 async function isEmptyDir(targetPath: string): Promise<boolean> {
   try {
     const entries = await fs.readdir(targetPath);
@@ -959,6 +983,8 @@ export async function updateCommand(opts: UpdateCommandOptions): Promise<void> {
     defaultRuntime.log(theme.warn("Skipping plugin updates: config is invalid."));
   }
 
+  await tryWriteCompletionCache(root, Boolean(opts.json));
+
   // Restart service if requested
   if (shouldRestart) {
     if (!opts.json) {