diff --git a/scripts/lib/error-format.mjs b/scripts/lib/error-format.mjs
index 29b9b51b6012..663b22828e91 100644
--- a/scripts/lib/error-format.mjs
+++ b/scripts/lib/error-format.mjs
@@ -1,3 +1,5 @@
+// Small error formatting helper for scripts that accept unknown thrown values.
+/** Return a readable message for Error and non-Error thrown values. */
 export function formatErrorMessage(error) {
   if (error instanceof Error) {
     return error.message || error.name || "Error";
diff --git a/scripts/lib/extension-import-boundary-checker.mjs b/scripts/lib/extension-import-boundary-checker.mjs
index edbe10d116cd..e12c22981e5f 100644
--- a/scripts/lib/extension-import-boundary-checker.mjs
+++ b/scripts/lib/extension-import-boundary-checker.mjs
@@ -1,3 +1,4 @@
+// Creates reusable import-boundary guards for bundled extension source trees.
 import { promises as fs } from "node:fs";
 import { BUNDLED_PLUGIN_PATH_PREFIX } from "./bundled-plugin-paths.mjs";
 import {
@@ -8,12 +9,12 @@ import {
   resolveRepoSpecifier,
   writeLine,
 } from "./guard-inventory-utils.mjs";
+import { mapWithConcurrency } from "./source-file-scan-cache.mjs";
 import {
   collectTypeScriptFilesFromRoots,
   resolveRepoRoot,
   resolveSourceRoots,
 } from "./ts-guard-utils.mjs";
-import { mapWithConcurrency } from "./source-file-scan-cache.mjs";
 
 const repoRoot = resolveRepoRoot(import.meta.url);
 
@@ -64,6 +65,7 @@ function scanImportBoundaryViolations(source, filePath, boundaryLabel, allowReso
   return entries;
 }
 
+/** Create a boundary checker with cached inventory collection and a CLI-style main function. */
 export function createExtensionImportBoundaryChecker(params) {
   const scanRoots = resolveSourceRoots(repoRoot, params.roots);
 
@@ -73,25 +75,21 @@ export function createExtensionImportBoundaryChecker(params) {
       .toSorted((left, right) =>
         normalizeRepoPath(repoRoot, left).localeCompare(normalizeRepoPath(repoRoot, right)),
       );
-    const entriesByFile = await mapWithConcurrency(
-      files,
-      undefined,
-      async (filePath) => {
-        const source = await fs.readFile(filePath, "utf8");
-        if (
-          params.skipSourcesWithoutBundledPluginPrefix &&
-          !source.includes(BUNDLED_PLUGIN_PATH_PREFIX)
-        ) {
-          return [];
-        }
-        return scanImportBoundaryViolations(
-          source,
-          filePath,
-          params.boundaryLabel,
-          params.allowResolvedPath,
-        );
-      },
-    );
+    const entriesByFile = await mapWithConcurrency(files, undefined, async (filePath) => {
+      const source = await fs.readFile(filePath, "utf8");
+      if (
+        params.skipSourcesWithoutBundledPluginPrefix &&
+        !source.includes(BUNDLED_PLUGIN_PATH_PREFIX)
+      ) {
+        return [];
+      }
+      return scanImportBoundaryViolations(
+        source,
+        filePath,
+        params.boundaryLabel,
+        params.allowResolvedPath,
+      );
+    });
     const inventory = entriesByFile.flat();
     return inventory.toSorted(compareEntries);
   });
diff --git a/scripts/lib/extension-source-classifier.mjs b/scripts/lib/extension-source-classifier.mjs
index bcd27c3ef928..cdc66cada894 100644
--- a/scripts/lib/extension-source-classifier.mjs
+++ b/scripts/lib/extension-source-classifier.mjs
@@ -1,3 +1,4 @@
+// Classifies bundled extension files as production, barrel, test-like, or infra artifacts.
 const CODE_FILE_RE = /\.(?:[cm]?ts|[cm]?js|tsx|jsx)$/u;
 const DECLARATION_FILE_RE = /\.d\.ts$/u;
 const RUNTIME_API_BARREL_RE = /(^|\/)runtime-api\.(?:[cm]?ts|[cm]?js|tsx|jsx)$/u;
@@ -17,6 +18,7 @@ function normalizeExtensionSourcePath(filePath) {
   return filePath.replaceAll("\\", "/");
 }
 
+/** Classify one bundled extension source path for boundary and packaging guards. */
 export function classifyBundledExtensionSourcePath(filePath) {
   const normalizedPath = normalizeExtensionSourcePath(filePath);
   const isCodeFile = CODE_FILE_RE.test(normalizedPath) && !DECLARATION_FILE_RE.test(normalizedPath);
diff --git a/scripts/lib/extension-test-plan.mjs b/scripts/lib/extension-test-plan.mjs
index 12151d37e224..fc0e099bec32 100644
--- a/scripts/lib/extension-test-plan.mjs
+++ b/scripts/lib/extension-test-plan.mjs
@@ -1,3 +1,4 @@
+// Resolves extension Vitest configs, costs, and batch shards for plugin test runs.
 import { spawnSync } from "node:child_process";
 import fs from "node:fs";
 import path from "node:path";
@@ -29,6 +30,7 @@ import { listAvailableExtensionIds } from "./changed-extensions.mjs";
 import { parsePositiveInt } from "./numeric-options.mjs";
 
 const repoRoot = path.resolve(import.meta.dirname, "..", "..");
+/** Default number of shards for broad bundled extension test batches. */
 export const DEFAULT_EXTENSION_TEST_SHARD_COUNT = 8;
 const EXTENSION_TEST_COST_MULTIPLIERS = {
   // CI shard planning uses measured wall time rather than raw file count.
@@ -129,6 +131,7 @@ function listFilesystemTestFiles(rootPath) {
   return files.toSorted((left, right) => left.localeCompare(right));
 }
 
+/** List tracked or filesystem-discovered test files for extension roots. */
 export function listTrackedTestFilesForRoots(roots) {
   const files = [];
   for (const root of roots) {
@@ -190,6 +193,7 @@ function resolveExtensionDirectory(targetArg, cwd = process.cwd()) {
   );
 }
 
+/** Resolve the Vitest configs, files, and estimated cost for one extension target. */
 export function resolveExtensionTestPlan(params = {}) {
   const cwd = params.cwd ?? process.cwd();
   const targetArg = params.targetArg;
@@ -327,6 +331,7 @@ function mergeTestPlans(plans) {
   };
 }
 
+/** Resolve a combined extension test plan for explicit or all available extension ids. */
 export function resolveExtensionBatchPlan(params = {}) {
   const cwd = params.cwd ?? process.cwd();
   const hasExplicitExtensionIds = params.extensionIds !== undefined;
@@ -357,6 +362,7 @@ function pickLeastLoadedShard(shards) {
   }, -1);
 }
 
+/** Create balanced extension test shards from per-extension plans. */
 export function createExtensionTestShards(params = {}) {
   const cwd = params.cwd ?? process.cwd();
   const extensionIds = params.extensionIds ?? listAvailableExtensionIds();
diff --git a/scripts/lib/format-generated-module.mjs b/scripts/lib/format-generated-module.mjs
index 1bbd5cf9d051..8bda74e15d59 100644
--- a/scripts/lib/format-generated-module.mjs
+++ b/scripts/lib/format-generated-module.mjs
@@ -1,9 +1,11 @@
+// Formats generated TypeScript/JavaScript modules through the repo formatter.
 import { spawnSync } from "node:child_process";
 import fs from "node:fs";
 import os from "node:os";
 import path from "node:path";
 import { resolvePnpmRunner } from "../pnpm-runner.mjs";
 
+/** Resolve the fastest available oxfmt command for a generated module path. */
 export function resolveGeneratedModuleFormatter(params) {
   const platform = params.platform ?? process.platform;
   const existsSync = params.existsSync ?? fs.existsSync;
@@ -26,6 +28,7 @@ export function resolveGeneratedModuleFormatter(params) {
   });
 }
 
+/** Format generated source in a temporary file and return the formatter output. */
 export function formatGeneratedModule(source, { repoRoot, outputPath, errorLabel }) {
   const resolvedRepoRoot = path.resolve(repoRoot);
   const resolvedOutputPath = path.resolve(