diff --git a/src/editor/core/cm/languages.test.ts b/src/editor/core/cm/languages.test.ts
index c6e71b62..5ca460d6 100644
--- a/src/editor/core/cm/languages.test.ts
+++ b/src/editor/core/cm/languages.test.ts
@@ -24,6 +24,30 @@ describe("language modes", () => {
     ]);
   });
 
+  it("parses YAML into large tree buffers and highlights mappings after comment lines", async () => {
+    for (const path of ["/p/application.yml", "/p/compose.yaml"]) {
+      const support = await loadSupport(findLanguageDescription("YAML", path)!);
+      // @lezer/yaml can invert a node's range on a tree buffer boundary; one buffer avoids it.
+      expect((support!.language.parser as unknown as { bufferLength: number }).bufferLength).toBe(1 << 16);
+    }
+    const support = await loadSupport(findLanguageDescription("YAML", "/p/application.yml")!);
+    const source = "spring:\n  datasource:\n  # driver: a\n  # url: b\n    driver: c # d\n    url: e\n";
+    const found: Array<[string, string]> = [];
+    highlightTree(
+      support!.language.parser.parse(source),
+      tagHighlighter([
+        { tag: t.lineComment, class: "comment" },
+        { tag: t.definition(t.propertyName), class: "key" },
+      ]),
+      (from, to, style) => found.push([source.slice(from, to), style]),
+    );
+    expect(found.filter(([, style]) => style === "comment").map(([text]) => text)).toEqual([
+      "# driver: a",
+      "# url: b",
+      "# d",
+    ]);
+  });
+
   it("recognizes AsciiDoc files and loads their lightweight syntax mode", async () => {
     for (const path of ["/docs/guide.adoc", "/docs/guide.asciidoc"]) {
       const description = findLanguageDescription("AsciiDoc", path);
diff --git a/src/editor/core/cm/languages.ts b/src/editor/core/cm/languages.ts
index 2c61f901..5bf64848 100644
--- a/src/editor/core/cm/languages.ts
+++ b/src/editor/core/cm/languages.ts
@@ -115,6 +115,21 @@ const OWN_MODES = [
     load: () => import("./erb").then((m) => m.erb()),
   }),
   LanguageDescription.of({ name: "JSP", load: () => import("./jsp").then((m) => m.jsp()) }),
+  LanguageDescription.of({
+    name: "YAML",
+    alias: ["yml"],
+    extensions: ["yaml", "yml"],
+    load: async () => {
+      const support = await languageData.find((l) => l.name === "YAML")!.load();
+      // @lezer/yaml can give a mapping that follows comment lines an inverted range when it
+      // lands on a tree buffer boundary (1024 entries by default); highlighting then skips
+      // the whole mapping. Larger buffers keep ordinary YAML files in one.
+      return new LanguageSupport(
+        (support.language as LRLanguage).configure({ bufferLength: 1 << 16 }),
+        support.support,
+      );
+    },
+  }),
 ];
 
 const BATCH_KEYWORDS = new Set([