diff --git a/tailwind.config.ts b/tailwind.config.ts
index 624ae47a5c..8693208e13 100644
--- a/tailwind.config.ts
+++ b/tailwind.config.ts
@@ -37,7 +37,7 @@ export default {
     './{build,models,modules,routers,services}/**/*.go',
     './templates/**/*.tmpl',
     './web_src/js/**/*.{ts,js,vue}',
-  ].filter(Boolean),
+  ].filter(Boolean as unknown as <T>(x: T | boolean) => x is T),
   blocklist: [
     // classes that don't work without CSS variables from "@tailwind base" which we don't use
     'transform', 'shadow', 'ring', 'blur', 'grayscale', 'invert', '!invert', 'filter', '!filter',
diff --git a/tests/e2e/utils_e2e.ts b/tests/e2e/utils_e2e.ts
index 3e92e0d3c2..0973f0838c 100644
--- a/tests/e2e/utils_e2e.ts
+++ b/tests/e2e/utils_e2e.ts
@@ -33,15 +33,15 @@ export async function login_user(browser: Browser, workerInfo: WorkerInfo, user:
 }
 
 export async function load_logged_in_context(browser: Browser, workerInfo: WorkerInfo, user: string) {
-  let context;
   try {
-    context = await browser.newContext({storageState: `${ARTIFACTS_PATH}/state-${user}-${workerInfo.workerIndex}.json`});
+    return await browser.newContext({storageState: `${ARTIFACTS_PATH}/state-${user}-${workerInfo.workerIndex}.json`});
   } catch (err) {
     if (err.code === 'ENOENT') {
       throw new Error(`Could not find state for '${user}'. Did you call login_user(browser, workerInfo, '${user}') in test.beforeAll()?`);
+    } else {
+      throw err;
     }
   }
-  return context;
 }
 
 export async function save_visual(page: Page) {
diff --git a/tools/generate-svg.ts b/tools/generate-svg.ts
index b1dc46d451..c18eacc86f 100755
--- a/tools/generate-svg.ts
+++ b/tools/generate-svg.ts
@@ -47,6 +47,10 @@ function processAssetsSvgFiles(pattern: string, opts: Opts = {}) {
   return glob(pattern).map((path) => processAssetsSvgFile(path, opts));
 }
 
+function lowercaseKeys(obj: Record<string, any>) {
+  return Object.fromEntries(Object.entries(obj).map(([key, value]) => [key.toLowerCase(), value]));
+}
+
 async function processMaterialFileIcons() {
   const paths = glob('node_modules/material-icon-theme/icons/*.svg');
   const svgSymbols: Record<string, string> = {};
@@ -76,18 +80,30 @@ async function processMaterialFileIcons() {
   //    * https://code.visualstudio.com/docs/languages/identifiers#_known-language-identifiers
   //    * https://github.com/microsoft/vscode/tree/1.98.0/extensions
   delete iconRules.iconDefinitions;
-  for (const [k, v] of Object.entries(iconRules.fileNames)) iconRules.fileNames[k.toLowerCase()] = v;
-  for (const [k, v] of Object.entries(iconRules.folderNames)) iconRules.folderNames[k.toLowerCase()] = v;
-  for (const [k, v] of Object.entries(iconRules.fileExtensions)) iconRules.fileExtensions[k.toLowerCase()] = v;
+
+  if (iconRules.fileNames) {
+    iconRules.fileNames = lowercaseKeys(iconRules.fileNames);
+  }
+  if (iconRules.folderNames) {
+    iconRules.folderNames = lowercaseKeys(iconRules.folderNames);
+  }
+  if (iconRules.fileExtensions) {
+    iconRules.fileExtensions = lowercaseKeys(iconRules.fileExtensions);
+  }
+
   // Use VSCode's "Language ID" mapping from its extensions
   for (const [_, langIdExtMap] of Object.entries(vscodeExtensions)) {
     for (const [langId, names] of Object.entries(langIdExtMap)) {
       for (const name of names) {
         const nameLower = name.toLowerCase();
         if (nameLower[0] === '.') {
-          iconRules.fileExtensions[nameLower.substring(1)] ??= langId;
+          if (iconRules.fileExtensions) {
+            iconRules.fileExtensions[nameLower.substring(1)] ??= langId;
+          }
         } else {
-          iconRules.fileNames[nameLower] ??= langId;
+          if (iconRules.fileNames) {
+            iconRules.fileNames[nameLower] ??= langId;
+          }
         }
       }
     }
diff --git a/tsconfig.json b/tsconfig.json
index 3bc6065647..1daf4b7233 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -40,6 +40,7 @@
     "strictBindCallApply": true,
     "strictBuiltinIteratorReturn": true,
     "strictFunctionTypes": true,
+    "strictNullChecks": false,
     "stripInternal": true,
     "verbatimModuleSyntax": true,
     "types": [
diff --git a/web_src/js/features/repo-issue.ts b/web_src/js/features/repo-issue.ts
index 58274b95c0..bacdae5350 100644
--- a/web_src/js/features/repo-issue.ts
+++ b/web_src/js/features/repo-issue.ts
@@ -261,7 +261,7 @@ export function initRepoPullRequestReview() {
     if (commentDiv) {
       // get the name of the parent id
       const groupID = commentDiv.closest('div[id^="code-comments-"]')?.getAttribute('id');
-      if (groupID && groupID.startsWith('code-comments-')) {
+      if (groupID?.startsWith('code-comments-')) {
         const id = groupID.slice(14);
         const ancestorDiffBox = commentDiv.closest<HTMLElement>('.diff-file-box');
 
diff --git a/web_src/js/features/repo-settings.ts b/web_src/js/features/repo-settings.ts
index 43a236b0c6..7a8df8af0f 100644
--- a/web_src/js/features/repo-settings.ts
+++ b/web_src/js/features/repo-settings.ts
@@ -101,7 +101,7 @@ function initRepoSettingsBranches() {
   // show the `Matched` mark for the status checks that match the pattern
   const markMatchedStatusChecks = () => {
     const patterns = (document.querySelector<HTMLTextAreaElement>('#status_check_contexts').value || '').split(/[\r\n]+/);
-    const validPatterns = patterns.map((item) => item.trim()).filter(Boolean);
+    const validPatterns = patterns.map((item) => item.trim()).filter(Boolean as unknown as <T>(x: T | boolean) => x is T);
     const marks = document.querySelectorAll('.status-check-matched-mark');
 
     for (const el of marks) {
diff --git a/web_src/js/svg.ts b/web_src/js/svg.ts
index 2ad9bffd51..3d3e653072 100644
--- a/web_src/js/svg.ts
+++ b/web_src/js/svg.ts
@@ -181,7 +181,7 @@ export function svg(name: SvgName, size = 16, classNames?: string | string[]): s
     svgNode.setAttribute('width', String(size));
     svgNode.setAttribute('height', String(size));
   }
-  if (className) svgNode.classList.add(...className.split(/\s+/).filter(Boolean));
+  if (className) svgNode.classList.add(...className.split(/\s+/).filter(Boolean as unknown as <T>(x: T | boolean) => x is T));
   return serializeXml(svgNode);
 }
 
diff --git a/webpack.config.ts b/webpack.config.ts
index 9f31c01e88..f0528a7331 100644
--- a/webpack.config.ts
+++ b/webpack.config.ts
@@ -30,7 +30,7 @@ const isProduction = env.NODE_ENV !== 'development';
 // false - all disabled
 let sourceMaps;
 if ('ENABLE_SOURCEMAP' in env) {
-  sourceMaps = ['true', 'false'].includes(env.ENABLE_SOURCEMAP) ? env.ENABLE_SOURCEMAP : 'reduced';
+  sourceMaps = ['true', 'false'].includes(env.ENABLE_SOURCEMAP || '') ? env.ENABLE_SOURCEMAP : 'reduced';
 } else {
   sourceMaps = isProduction ? 'reduced' : 'true';
 }
@@ -95,7 +95,7 @@ export default {
     path: fileURLToPath(new URL('public/assets', import.meta.url)),
     filename: () => 'js/[name].js',
     chunkFilename: ({chunk}) => {
-      const language = (/monaco.*languages?_.+?_(.+?)_/.exec(String(chunk.id)) || [])[1];
+      const language = (/monaco.*languages?_.+?_(.+?)_/.exec(String(chunk?.id)) || [])[1];
       return `js/${language ? `monaco-language-${language.toLowerCase()}` : `[name]`}.[contenthash:8].js`;
     },
   },
@@ -270,7 +270,7 @@ export default {
     excludeAssets: [
       /^js\/monaco-language-.+\.js$/,
       !isProduction && /^licenses.txt$/,
-    ].filter(Boolean),
+    ].filter(Boolean as unknown as <T>(x: T | boolean) => x is T),
     groupAssetsByChunk: false,
     groupAssetsByEmitStatus: false,
     groupAssetsByInfo: false,