diffs: validate hydration language inputs

CHANGELOG.md

@@ -29,6 +29,7 @@ Docs: https://docs.openclaw.ai
 
 ### Fixes
 
+- Diffs: fall back to plain text when `lang` hints are invalid during diff render and viewer hydration, so bad or stale language values no longer break the diff viewer. (#57902) Thanks @gumadeiras.
 - Image generation/build: write stable runtime alias files into `dist/` and route provider-auth runtime lookups through those aliases so image-generation providers keep resolving auth/runtime modules after rebuilds instead of crashing on missing hashed chunk files.
 - Config/runtime: pin the first successful config load in memory for the running process and refresh that snapshot on successful writes/reloads, so hot paths stop reparsing `openclaw.json` between watcher-driven swaps.
 - Config/legacy cleanup: stop probing obsolete alternate legacy config names and service labels during local config/service detection, while keeping the active `~/.openclaw/openclaw.json` path canonical.

extensions/diffs/src/viewer-client.test.ts

@@ -10,14 +10,14 @@ describe("filterSupportedHydrationLanguages", () => {
   });
 
   it("drops invalid languages and falls back to text", async () => {
-    await expect(
-      filterSupportedHydrationLanguages(["not-a-real-language" as unknown as "text"]),
-    ).resolves.toEqual(["text"]);
+    await expect(filterSupportedHydrationLanguages(["not-a-real-language"])).resolves.toEqual([
+      "text",
+    ]);
   });
 
   it("keeps valid languages when invalid hints are mixed in", async () => {
     await expect(
-      filterSupportedHydrationLanguages(["typescript", "not-a-real-language" as unknown as "text"]),
+      filterSupportedHydrationLanguages(["typescript", "not-a-real-language"]),
     ).resolves.toEqual(["typescript"]);
   });
 });

extensions/diffs/src/viewer-client.ts

@@ -30,7 +30,7 @@ const viewerState: ViewerState = {
 };
 
 export async function filterSupportedHydrationLanguages(
-  languages: Iterable<SupportedLanguages>,
+  languages: Iterable<string>,
 ): Promise<SupportedLanguages[]> {
   const supported = new Set<SupportedLanguages>();
   for (const language of languages) {