diff --git a/Herebyfile.mjs b/Herebyfile.mjs
index 5260a813a6bcf..08f790ae624a9 100644
--- a/Herebyfile.mjs
+++ b/Herebyfile.mjs
@@ -6,7 +6,7 @@ import { task } from "hereby";
 import _glob from "glob";
 import util from "util";
 import chalk from "chalk";
-import { exec, readJson, needsUpdate, getDiffTool, getDirSize, memoize } from "./scripts/build/utils.mjs";
+import { exec, readJson, getDiffTool, getDirSize, memoize, needsUpdate } from "./scripts/build/utils.mjs";
 import { runConsoleTests, refBaseline, localBaseline, refRwcBaseline, localRwcBaseline } from "./scripts/build/tests.mjs";
 import { buildProject as realBuildProject, cleanProject, watchProject } from "./scripts/build/projects.mjs";
 import { localizationDirectories } from "./scripts/build/localization.mjs";
@@ -81,22 +81,18 @@ export const generateLibs = task({
     description: "Builds the library targets",
     run: async () => {
         await fs.promises.mkdir("./built/local", { recursive: true });
-        const allSources = libs().flatMap((lib) => lib.sources);
-        const allTargets = libs().flatMap((lib) => lib.target);
-        if (needsUpdate([copyrightFilename, ...allSources], allTargets)) {
-            for (const lib of libs()) {
-                let output = await copyright();
-
-                for (const source of lib.sources) {
-                    const contents = await fs.promises.readFile(source, "utf-8");
-                    // TODO(jakebailey): "\n\n" is for compatibility with our current tests; our test baselines
-                    // are sensitive to the positions of things in the lib files. Eventually remove this,
-                    // or remove lib.d.ts line numbers from our baselines.
-                    output += "\n\n" + contents.replace(/\r\n/g, "\n");
-                }
-
-                await fs.promises.writeFile(lib.target, output);
+        for (const lib of libs()) {
+            let output = await copyright();
+
+            for (const source of lib.sources) {
+                const contents = await fs.promises.readFile(source, "utf-8");
+                // TODO(jakebailey): "\n\n" is for compatibility with our current tests; our test baselines
+                // are sensitive to the positions of things in the lib files. Eventually remove this,
+                // or remove lib.d.ts line numbers from our baselines.
+                output += "\n\n" + contents.replace(/\r\n/g, "\n");
             }
+
+            await fs.promises.writeFile(lib.target, output);
         }
     },
 });
@@ -110,9 +106,7 @@ export const generateDiagnostics = task({
     name: "generate-diagnostics",
     description: "Generates a diagnostic file in TypeScript based on an input JSON file",
     run: async () => {
-        if (needsUpdate(diagnosticMessagesJson, [diagnosticMessagesGeneratedJson, diagnosticInformationMapTs])) {
-            await exec(process.execPath, ["scripts/processDiagnosticMessages.mjs", diagnosticMessagesJson]);
-        }
+        await exec(process.execPath, ["scripts/processDiagnosticMessages.mjs", diagnosticMessagesJson]);
     }
 });
 
@@ -410,7 +404,11 @@ export const dtsServices = task({
     name: "dts-services",
     description: "Bundles typescript.d.ts",
     dependencies: [buildServices],
-    run: () => runDtsBundler("./built/local/typescript/typescript.d.ts", "./built/local/typescript.d.ts"),
+    run: async () => {
+        if (needsUpdate("./built/local/typescript/tsconfig.tsbuildinfo", ["./built/local/typescript.d.ts", "./built/local/typescript.internal.d.ts"])) {
+            runDtsBundler("./built/local/typescript/typescript.d.ts", "./built/local/typescript.d.ts");
+        }
+    },
 });
 
 
@@ -464,7 +462,11 @@ export const dtsLssl = task({
     name: "dts-lssl",
     description: "Bundles tsserverlibrary.d.ts",
     dependencies: [buildLssl],
-    run: () => runDtsBundler("./built/local/tsserverlibrary/tsserverlibrary.d.ts", "./built/local/tsserverlibrary.d.ts")
+    run: async () => {
+        if (needsUpdate("./built/local/tsserverlibrary/tsconfig.tsbuildinfo", ["./built/local/tsserverlibrary.d.ts", "./built/local/tsserverlibrary.internal.d.ts"])) {
+            await runDtsBundler("./built/local/tsserverlibrary/tsserverlibrary.d.ts", "./built/local/tsserverlibrary.d.ts");
+        }
+    }
 });
 
 export const dts = task({
@@ -560,11 +562,9 @@ export const generateTypesMap = task({
     run: async () => {
         const source = "src/server/typesMap.json";
         const target = "built/local/typesMap.json";
-        if (needsUpdate(source, target)) {
-            const contents = await fs.promises.readFile(source, "utf-8");
-            JSON.parse(contents);
-            await fs.promises.writeFile(target, contents);
-        }
+        const contents = await fs.promises.readFile(source, "utf-8");
+        JSON.parse(contents); // Validates that the JSON parses.
+        await fs.promises.writeFile(target, contents);
     }
 });
 
@@ -577,11 +577,9 @@ const copyBuiltLocalDiagnosticMessages = task({
     name: "copy-built-local-diagnostic-messages",
     dependencies: [generateDiagnostics],
     run: async () => {
-        if (needsUpdate(diagnosticMessagesGeneratedJson, builtLocalDiagnosticMessagesGeneratedJson)) {
-            const contents = await fs.promises.readFile(diagnosticMessagesGeneratedJson, "utf-8");
-            JSON.parse(contents);
-            await fs.promises.writeFile(builtLocalDiagnosticMessagesGeneratedJson, contents);
-        }
+        const contents = await fs.promises.readFile(diagnosticMessagesGeneratedJson, "utf-8");
+        JSON.parse(contents); // Validates that the JSON parses.
+        await fs.promises.writeFile(builtLocalDiagnosticMessagesGeneratedJson, contents);
     }
 });
 
diff --git a/scripts/processDiagnosticMessages.mjs b/scripts/processDiagnosticMessages.mjs
index 33069ce66aa6a..2b36942cc461a 100644
--- a/scripts/processDiagnosticMessages.mjs
+++ b/scripts/processDiagnosticMessages.mjs
@@ -13,7 +13,7 @@ void 0;
 
 /** @typedef {Map<string, DiagnosticDetails>} InputDiagnosticMessageTable */
 
-function main() {
+async function main() {
     if (process.argv.length < 3) {
         console.log("Usage:");
         console.log("\tnode processDiagnosticMessages.mjs <diagnostic-json-input-file>");
@@ -24,15 +24,24 @@ function main() {
      * @param {string} fileName
      * @param {string} contents
      */
-    function writeFile(fileName, contents) {
-        fs.writeFile(path.join(path.dirname(inputFilePath), fileName), contents, { encoding: "utf-8" }, err => {
-            if (err) throw err;
-        });
+     async function writeFile(fileName, contents) {
+        const filePath = path.join(path.dirname(inputFilePath), fileName);
+        try {
+            const existingContents = await fs.promises.readFile(filePath, "utf-8");
+            if (existingContents === contents) {
+                return;
+            }
+        }
+        catch {
+            // Just write the file.
+        }
+
+        await fs.promises.writeFile(filePath, contents, { encoding: "utf-8" });
     }
 
     const inputFilePath = process.argv[2].replace(/\\/g, "/");
     console.log(`Reading diagnostics from ${inputFilePath}`);
-    const inputStr = fs.readFileSync(inputFilePath, { encoding: "utf-8" });
+    const inputStr = await fs.promises.readFile(inputFilePath, { encoding: "utf-8" });
 
     /** @type {{ [key: string]: DiagnosticDetails }} */
     const diagnosticMessagesJson = JSON.parse(inputStr);
@@ -47,10 +56,10 @@ function main() {
 
     const infoFileOutput = buildInfoFileOutput(diagnosticMessages, inputFilePath);
     checkForUniqueCodes(diagnosticMessages);
-    writeFile("diagnosticInformationMap.generated.ts", infoFileOutput);
+    await writeFile("diagnosticInformationMap.generated.ts", infoFileOutput);
 
     const messageOutput = buildDiagnosticMessageOutput(diagnosticMessages);
-    writeFile("diagnosticMessages.generated.json", messageOutput);
+    await writeFile("diagnosticMessages.generated.json", messageOutput);
 }
 
 /**