fix: preserve generated asset mtimes

extensions/browser/scripts/build-copilot-runtime.d.mts

@@ -0,0 +1,20 @@
+type CopilotRuntimeBuild = (options: {
+  bundle: boolean;
+  entryPoints: string[];
+  format: string;
+  legalComments: string;
+  minify: boolean;
+  outfile: string;
+  platform: string;
+  target: string;
+  tsconfig: string;
+  write: false;
+}) => Promise<{
+  outputFiles?: Array<{ text: string }>;
+}>;
+
+/** Builds the Browser copilot runtime and returns whether the generated asset changed. */
+export function buildCopilotRuntime(params?: {
+  build?: CopilotRuntimeBuild;
+  outputPath?: string;
+}): Promise<boolean>;

extensions/browser/scripts/build-copilot-runtime.mjs

@@ -2,19 +2,38 @@
 import path from "node:path";
 import { fileURLToPath } from "node:url";
 import { build } from "esbuild";
+import { writeGeneratedTextAsset } from "../../../scripts/lib/generated-text-asset.mjs";
 
-const pluginDir = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "..");
+const modulePath = fileURLToPath(import.meta.url);
+const pluginDir = path.resolve(path.dirname(modulePath), "..");
 const repoRoot = path.resolve(pluginDir, "../..");
 const outfile = path.join(pluginDir, "chrome-extension", "modules", "copilot-runtime.js");
 
-await build({
-  entryPoints: [path.join(pluginDir, "scripts", "copilot-runtime-entry.ts")],
-  outfile,
-  bundle: true,
-  format: "esm",
-  legalComments: "inline",
-  minify: true,
-  platform: "browser",
-  target: "chrome125",
-  tsconfig: path.join(repoRoot, "tsconfig.json"),
-});
+/** Builds the copilot runtime without rewriting an identical generated asset. */
+export async function buildCopilotRuntime(params = {}) {
+  const buildImpl = params.build ?? build;
+  const outputPath = params.outputPath ?? outfile;
+  const result = await buildImpl({
+    entryPoints: [path.join(pluginDir, "scripts", "copilot-runtime-entry.ts")],
+    outfile: outputPath,
+    bundle: true,
+    format: "esm",
+    legalComments: "inline",
+    minify: true,
+    platform: "browser",
+    target: "chrome125",
+    tsconfig: path.join(repoRoot, "tsconfig.json"),
+    write: false,
+  });
+
+  const outputFile = result.outputFiles?.[0];
+  if (!outputFile) {
+    throw new Error("esbuild did not produce the Browser copilot runtime bundle");
+  }
+
+  return writeGeneratedTextAsset(outputPath, outputFile.text);
+}
+
+if (process.argv[1] === modulePath) {
+  await buildCopilotRuntime();
+}

extensions/browser/scripts/build-copilot-runtime.test.ts

@@ -0,0 +1,32 @@
+import fs from "node:fs";
+import path from "node:path";
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { useAutoCleanupTempDirTracker } from "../test-support.js";
+import { buildCopilotRuntime } from "./build-copilot-runtime.mjs";
+
+const tempDirs = useAutoCleanupTempDirTracker(afterEach);
+
+describe("scripts/build-copilot-runtime.mjs", () => {
+  it("creates a missing bundle without rewriting it when unchanged", async () => {
+    const rootDir = tempDirs.make("openclaw-browser-copilot-runtime-");
+    const outputPath = path.join(rootDir, "copilot-runtime.js");
+    const build = vi.fn(async () => ({
+      outputFiles: [{ text: "export const copilotRuntime = true;\n" }],
+    }));
+
+    await expect(buildCopilotRuntime({ build, outputPath })).resolves.toBe(true);
+    expect(fs.readFileSync(outputPath, "utf8")).toBe("export const copilotRuntime = true;\n");
+
+    const initialTime = new Date("2026-07-18T04:00:00.000Z");
+    fs.utimesSync(outputPath, initialTime, initialTime);
+
+    await expect(buildCopilotRuntime({ build, outputPath })).resolves.toBe(false);
+    expect(fs.statSync(outputPath).mtimeMs).toBe(initialTime.getTime());
+    expect(build).toHaveBeenCalledWith(
+      expect.objectContaining({
+        outfile: outputPath,
+        write: false,
+      }),
+    );
+  });
+});

scripts/build-diffs-viewer-runtime.mjs

@@ -1,10 +1,10 @@
 #!/usr/bin/env node
 
 // Builds browser runtime bundles for the diffs viewer assets.
-import fs from "node:fs/promises";
 import path from "node:path";
 import { fileURLToPath } from "node:url";
 import { build } from "esbuild";
+import { writeGeneratedTextAsset } from "./lib/generated-text-asset.mjs";
 
 const modulePath = fileURLToPath(import.meta.url);
 const repoRoot = path.resolve(path.dirname(modulePath), "..");
@@ -73,8 +73,6 @@ async function buildDiffsViewerRuntime(targetName) {
   }
 
   const outputPath = path.join(repoRoot, target.output);
-  await fs.mkdir(path.dirname(outputPath), { recursive: true });
-
   const result = await build({
     entryPoints: [path.join(repoRoot, target.entry)],
     bundle: true,
@@ -112,18 +110,7 @@ async function buildDiffsViewerRuntime(targetName) {
   }
 
   const runtime = outputFile.text.replace(/[ \t]+$/gm, "");
-  let previousRuntime = null;
-  try {
-    previousRuntime = await fs.readFile(outputPath, "utf8");
-  } catch (error) {
-    if (error?.code !== "ENOENT") {
-      throw error;
-    }
-  }
-
-  if (previousRuntime !== runtime) {
-    await fs.writeFile(outputPath, runtime);
-  }
+  await writeGeneratedTextAsset(outputPath, runtime);
 }
 
 if (process.argv[1] === modulePath) {

scripts/build-discord-activity-sdk.mjs

@@ -1,9 +1,9 @@
 #!/usr/bin/env node
 
-import fs from "node:fs/promises";
 import path from "node:path";
 import { fileURLToPath } from "node:url";
 import { build } from "esbuild";
+import { writeGeneratedTextAsset } from "./lib/generated-text-asset.mjs";
 
 const modulePath = fileURLToPath(import.meta.url);
 const repoRoot = path.resolve(path.dirname(modulePath), "..");
@@ -14,7 +14,6 @@ const outputPath = path.join(repoRoot, "extensions/discord/assets/embedded-app-s
 export async function buildDiscordActivitySdk(params = {}) {
   const buildImpl = params.build ?? build;
   const targetPath = params.outputPath ?? outputPath;
-  await fs.mkdir(path.dirname(targetPath), { recursive: true });
   const result = await buildImpl({
     entryPoints: ["@discord/embedded-app-sdk"],
     absWorkingDir: discordDir,
@@ -33,21 +32,7 @@ export async function buildDiscordActivitySdk(params = {}) {
     throw new Error("esbuild did not produce the Discord Embedded App SDK bundle");
   }
 
-  const nextBundle = outputFile.text;
-  let currentBundle = null;
-  try {
-    currentBundle = await fs.readFile(targetPath, "utf8");
-  } catch (error) {
-    if (error?.code !== "ENOENT") {
-      throw error;
-    }
-  }
-
-  if (currentBundle === nextBundle) {
-    return false;
-  }
-  await fs.writeFile(targetPath, nextBundle);
-  return true;
+  return writeGeneratedTextAsset(targetPath, outputFile.text);
 }
 
 if (process.argv[1] === modulePath) {

scripts/lib/generated-text-asset.d.mts

@@ -0,0 +1,12 @@
+interface GeneratedTextAssetFs {
+  readFile(path: string, encoding: "utf8"): Promise<string>;
+  mkdir(path: string, options: { recursive: true }): Promise<unknown>;
+  writeFile(path: string, contents: string, encoding: "utf8"): Promise<unknown>;
+}
+
+/** Writes a generated text asset and returns whether its contents changed. */
+export function writeGeneratedTextAsset(
+  filePath: string,
+  contents: string,
+  params?: { fs?: GeneratedTextAssetFs },
+): Promise<boolean>;

scripts/lib/generated-text-asset.mjs

@@ -0,0 +1,25 @@
+import fs from "node:fs/promises";
+import path from "node:path";
+
+/**
+ * Writes a generated text asset only when its contents changed.
+ */
+export async function writeGeneratedTextAsset(filePath, contents, params = {}) {
+  const fsImpl = params.fs ?? fs;
+  let currentContents = null;
+  try {
+    currentContents = await fsImpl.readFile(filePath, "utf8");
+  } catch (error) {
+    if (error?.code !== "ENOENT") {
+      throw error;
+    }
+  }
+
+  if (currentContents === contents) {
+    return false;
+  }
+
+  await fsImpl.mkdir(path.dirname(filePath), { recursive: true });
+  await fsImpl.writeFile(filePath, contents, "utf8");
+  return true;
+}

scripts/test-projects.test-support.mjs

@@ -1443,6 +1443,14 @@ const TOOLING_SOURCE_TEST_TARGETS = new Map([
     "scripts/lib/plugin-npm-runtime-assets.mjs",
     ["test/scripts/plugin-npm-runtime-build-args.test.ts"],
   ],
+  [
+    "scripts/lib/generated-text-asset.mjs",
+    [
+      "extensions/browser/scripts/build-copilot-runtime.test.ts",
+      "test/scripts/build-diffs-viewer-runtime.test.ts",
+      "test/scripts/bundled-plugin-assets.test.ts",
+    ],
+  ],
   [
     "scripts/lib/static-extension-assets.mjs",
     [
@@ -2134,6 +2142,10 @@ const TOOLING_SOURCE_TEST_TARGETS = new Map([
   ["scripts/build-discord-activity-sdk.mjs", ["test/scripts/bundled-plugin-assets.test.ts"]],
   ["scripts/build-diffs-viewer-runtime.mjs", ["test/scripts/build-diffs-viewer-runtime.test.ts"]],
   ["scripts/run-node-watch-paths.mjs", ["test/scripts/bundled-plugin-assets.test.ts"]],
+  [
+    "extensions/browser/scripts/build-copilot-runtime.mjs",
+    ["extensions/browser/scripts/build-copilot-runtime.test.ts"],
+  ],
   ["extensions/canvas/scripts/bundle-a2ui.mjs", ["extensions/canvas/scripts/bundle-a2ui.test.ts"]],
   ["extensions/canvas/scripts/copy-a2ui.mjs", ["extensions/canvas/scripts/copy-a2ui.test.ts"]],
 ]);