diff --git a/web_src/css/modules/codeeditor.css b/web_src/css/modules/codeeditor.css
index 11b772c05c..558ba7a44f 100644
--- a/web_src/css/modules/codeeditor.css
+++ b/web_src/css/modules/codeeditor.css
@@ -24,6 +24,8 @@
   font-family: var(--fonts-monospace);
   font-size: 12px;
   max-height: 90vh;
+  flex: 1;
+  min-height: 0;
 }
 
 .code-editor-container .cm-editor,
@@ -31,24 +33,22 @@
   border-radius: 0 0 var(--border-radius) var(--border-radius);
 }
 
-.code-editor-container .cm-content,
-.code-editor-container .cm-gutter {
-  min-height: 200px;
-}
-
 .code-editor-container .cm-scroller {
   overflow: auto;
   line-height: var(--line-height-code);
+  flex: 1;
+  min-height: 0;
+}
+
+.code-editor-container .cm-content {
+  align-self: stretch;
+  padding: 0;
 }
 
 .code-editor-container .cm-content * {
   caret-color: inherit;
 }
 
-.code-editor-container .cm-content {
-  padding: 0;
-}
-
 .code-editor-container .cm-cursor,
 .code-editor-container .cm-dropCursor {
   border-left-color: var(--color-caret);
@@ -341,6 +341,8 @@
 .code-editor-container {
   position: relative;
   min-height: 90vh;
+  display: flex;
+  flex-direction: column;
 }
 
 .cm-command-palette {
diff --git a/web_src/js/modules/codeeditor/main.ts b/web_src/js/modules/codeeditor/main.ts
index 320d73dd9f..e847f357cb 100644
--- a/web_src/js/modules/codeeditor/main.ts
+++ b/web_src/js/modules/codeeditor/main.ts
@@ -7,7 +7,7 @@ import type {PaletteCommand} from './command-palette.ts';
 import {contextMenu, collectSymbols, selectAllOccurrences} from './context-menu.ts';
 import {createJsonLinter, createSyntaxErrorLinter} from './linter.ts';
 import {clickableUrls, goToDefinitionAt, trimTrailingWhitespaceFromView} from './utils.ts';
-import type {LanguageDescription} from '@codemirror/language';
+import type {LanguageDescription, LanguageSupport} from '@codemirror/language';
 import type {Compartment, Extension} from '@codemirror/state';
 import type {EditorView, ViewUpdate} from '@codemirror/view';
 
@@ -295,16 +295,19 @@ export async function createCodeEditor(textarea: HTMLTextAreaElement, filenameIn
   return editor;
 }
 
-// files that are JSONC despite having a .json extension
-const jsoncFilesRegex = /^([jt]sconfig.*|devcontainer)\.json$/;
+// files that the JSON parser is too strict for (comments, trailing commas)
+const jsoncFilesRegex = /^([jt]sconfig.*|devcontainer)\.json$|\.(jsonc|json5)$/i;
 
-async function getLinterExtension(cm: CodemirrorModules, filename: string, loadedLang: {language: unknown} | null): Promise<Extension> {
-  const ext = extname(filename).toLowerCase();
-  if (ext === '.json' || ext === '.map') {
+async function getLinterExtension(cm: CodemirrorModules, filename: string, loadedLang: LanguageSupport | null): Promise<Extension> {
+  if (!loadedLang) return [];
+  const lang = loadedLang.language;
+  // StreamLanguage (legacy modes) don't produce Lezer error nodes
+  if (lang instanceof cm.language.StreamLanguage) return [];
+  if (lang.name === 'json') {
     return jsoncFilesRegex.test(filename) ? [] : [cm.lint.lintGutter(), await createJsonLinter(cm)];
   }
-  // StreamLanguage (legacy modes) don't produce Lezer error nodes
-  if (!loadedLang || loadedLang.language instanceof cm.language.StreamLanguage) return [];
+  // markdown's parser emits no error nodes, and nested code-fence overlays aren't traversed
+  if (lang.name === 'markdown') return [];
   return [cm.lint.lintGutter(), createSyntaxErrorLinter(cm)];
 }