diff --git a/src/cm/supportedModes.ts b/src/cm/supportedModes.ts
index 12febc9f9..f16746a74 100644
--- a/src/cm/supportedModes.ts
+++ b/src/cm/supportedModes.ts
@@ -152,6 +152,27 @@ addMode(
 	() => [],
 );
 
+// Languages that @codemirror/language-data only covers with legacy stream
+// tokenizers and that the official Additional Language Modes plugin
+// (acode.additional.langmodes) provides as Lezer grammars. They are left out
+// so the plugin registers them under their canonical names; without it, these
+// files fall back to plain text and Acode recommends the plugin.
+const PLUGIN_PROVIDED_LANGUAGES = new Set([
+	"clojure",
+	"clojurescript",
+	"edn",
+	"gas",
+	"kotlin",
+	"latex",
+	"stex",
+	"lua",
+	"swift",
+]);
+
+// Extensions other modes claim in @codemirror/language-data but that the
+// plugin has dedicated modes for: HTML lists Handlebars templates.
+const PLUGIN_PROVIDED_EXTENSIONS = new Set(["hbs", "handlebars"]);
+
 // 2) Register all languages provided by @codemirror/language-data
 //    We convert extensions like [".js", ".mjs"] into a modelist pattern: "js|mjs"
 //    and preserve aliases and filename regexes for languages like C++ and Dockerfile.
@@ -159,6 +180,7 @@ for (const lang of languages as readonly LanguageDescription[]) {
 	try {
 		const name = String(lang?.name || "").trim();
 		if (!name) continue;
+		if (PLUGIN_PROVIDED_LANGUAGES.has(normalizeModeKey(name))) continue;
 
 		const aliases = collectAliases(name, lang.alias);
 		const modeId = getModeId(name, aliases);
@@ -248,7 +270,9 @@ for (const lang of languages as readonly LanguageDescription[]) {
 		for (const e of langExtensions) {
 			if (typeof e !== "string") continue;
 			const cleaned = e.replace(/^\./, "").trim();
-			if (cleaned) parts.push(cleaned);
+			if (cleaned && !PLUGIN_PROVIDED_EXTENSIONS.has(cleaned.toLowerCase())) {
+				parts.push(cleaned);
+			}
 		}
 
 		const filenameMatchers: RegExp[] = [];
diff --git a/tests/unit/pluginProvidedModes.test.js b/tests/unit/pluginProvidedModes.test.js
new file mode 100644
index 000000000..959bf4897
--- /dev/null
+++ b/tests/unit/pluginProvidedModes.test.js
@@ -0,0 +1,104 @@
+import { afterEach, describe, expect, it } from "vitest";
+import "cm/supportedModes";
+import { addMode, getMode, getModeForPath, removeMode } from "cm/modelist";
+
+// Modes the Additional Language Modes plugin (acode.additional.langmodes)
+// replaces with Lezer grammars, with the extensions it registers.
+const pluginModes = [
+	{ name: "assembly", extensions: ["asm", "s", "S", "nasm"] },
+	{ name: "c", extensions: ["c", "h", "ino"] },
+	{ name: "clojure", extensions: ["clj", "cljs", "cljc", "cljx", "edn"] },
+	{ name: "kotlin", extensions: ["kt", "kts"] },
+	{ name: "latex", extensions: ["tex", "ltx", "sty", "cls", "latex"] },
+	{ name: "lua", extensions: ["lua"] },
+	{ name: "swift", extensions: ["swift"] },
+	{ name: "handlebars", extensions: ["hbs", "handlebars"] },
+	{ name: "mustache", extensions: ["mustache"] },
+];
+
+/** The plugin's registration rule: keep Acode's mode, add "<name>-enhanced". */
+function registerLikePlugin({ name, extensions }) {
+	const registered = getMode(name) ? `${name}-enhanced` : name;
+	addMode(registered, extensions, registered, () => []);
+	return registered;
+}
+
+describe("legacy modes replaced by the Additional Language Modes plugin", () => {
+	const registered = [];
+
+	afterEach(() => {
+		for (const name of registered.splice(0)) removeMode(name);
+	});
+
+	it.each([
+		"clojure",
+		"clojurescript",
+		"edn",
+		"gas",
+		"kotlin",
+		"latex",
+		"tex",
+		"stex",
+		"lua",
+		"swift",
+	])("does not ship a built-in %s mode", (name) => {
+		expect(getMode(name)).toBeNull();
+	});
+
+	it.each([
+		"a.kt",
+		"a.kts",
+		"a.lua",
+		"a.swift",
+		"a.clj",
+		"a.cljs",
+		"a.edn",
+		"a.s",
+		"a.tex",
+		"a.hbs",
+		"a.handlebars",
+	])("falls back to plain text for %s without the plugin", (path) => {
+		expect(getModeForPath(path).name).toBe("text");
+	});
+
+	it("keeps C, C++, HTML and Luau built in", () => {
+		expect(getModeForPath("a.html").name).toBe("html");
+		expect(getModeForPath("a.c").name).toBe("c");
+		expect(getModeForPath("a.cpp").name).toBe("cpp");
+		expect(getModeForPath("a.luau").name).toBe("luau");
+	});
+
+	it("opens .text files as plain text instead of LaTeX", () => {
+		expect(getModeForPath("notes.text").name).toBe("text");
+	});
+
+	it("lets the plugin register the replaced modes under canonical names", () => {
+		for (const mode of pluginModes) registered.push(registerLikePlugin(mode));
+
+		expect(registered).toEqual([
+			"assembly",
+			"c-enhanced",
+			"clojure",
+			"kotlin",
+			"latex",
+			"lua",
+			"swift",
+			"handlebars",
+			"mustache",
+		]);
+		expect(getModeForPath("a.kt").name).toBe("kotlin");
+		expect(getModeForPath("a.lua").name).toBe("lua");
+		expect(getModeForPath("a.swift").name).toBe("swift");
+		expect(getModeForPath("a.cljs").name).toBe("clojure");
+		expect(getModeForPath("a.edn").name).toBe("clojure");
+		expect(getModeForPath("a.s").name).toBe("assembly");
+		expect(getModeForPath("a.tex").name).toBe("latex");
+		expect(getModeForPath("a.c").name).toBe("c-enhanced");
+		expect(getModeForPath("a.hbs").name).toBe("handlebars");
+		expect(getModeForPath("a.handlebars").name).toBe("handlebars");
+		expect(getModeForPath("a.mustache").name).toBe("mustache");
+		expect(getModeForPath("a.html").name).toBe("html");
+		// Luau keeps its own mode even though "lua" now comes from the plugin.
+		expect(getModeForPath("a.luau").name).toBe("luau");
+	});
+});