diff --git a/.changeset/strict-translation-discovery.md b/.changeset/strict-translation-discovery.md
new file mode 100644
index 00000000..2f426c80
--- /dev/null
+++ b/.changeset/strict-translation-discovery.md
@@ -0,0 +1,5 @@
+---
+"openwiki": patch
+---
+
+fix: surface translation filesystem discovery failures
diff --git a/src/agent/translation-middleware.ts b/src/agent/translation-middleware.ts
index 574c2801..5d1a3499 100644
--- a/src/agent/translation-middleware.ts
+++ b/src/agent/translation-middleware.ts
@@ -405,9 +405,22 @@ function extractText(content: MessageContent): string {
 async function collectMarkdownFiles(
   backend: BackendProtocolV2,
   directoryPath: string,
+  optionalRoot = directoryPath,
 ): Promise<string[]> {
   const result = await backend.ls(directoryPath);
-  if (result.error) return [];
+  if (result.error) {
+    // A repository-mode wiki root may not exist yet, which is a valid no-op.
+    // Every other listing failure means the file tree is incomplete and must
+    // abort the pass rather than silently claiming a language switch succeeded.
+    if (
+      directoryPath === optionalRoot &&
+      isMissingDirectoryError(result.error)
+    ) {
+      return [];
+    }
+
+    throw new Error(`Unable to list ${directoryPath}: ${result.error}`);
+  }
 
   const files: string[] = [];
   for (const entry of result.files ?? []) {
@@ -416,7 +429,9 @@ async function collectMarkdownFiles(
 
     const entryPath = path.posix.join(directoryPath, name);
     if (entry.is_dir) {
-      files.push(...(await collectMarkdownFiles(backend, entryPath)));
+      files.push(
+        ...(await collectMarkdownFiles(backend, entryPath, optionalRoot)),
+      );
       continue;
     }
     if (
@@ -429,6 +444,10 @@ async function collectMarkdownFiles(
   return files;
 }
 
+function isMissingDirectoryError(error: string): boolean {
+  return /(?:ENOENT|not found)/iu.test(error);
+}
+
 /**
  * Reads a text file from the backend or throws an actionable error.
  */
diff --git a/test/translation-middleware.test.ts b/test/translation-middleware.test.ts
index 533c9da0..8219007a 100644
--- a/test/translation-middleware.test.ts
+++ b/test/translation-middleware.test.ts
@@ -444,4 +444,52 @@ describe("createWikiTranslationMiddleware beforeAgent", () => {
     ).resolves.toBeUndefined();
     expect(calls).toHaveLength(0);
   });
+
+  test("fails a language switch when the wiki root cannot be listed", async () => {
+    const { backend } = await setup("repository");
+    const realLs = backend.ls.bind(backend);
+    vi.spyOn(backend, "ls").mockImplementation((directoryPath) =>
+      directoryPath === "/openwiki"
+        ? Promise.resolve({ error: "EACCES: permission denied" })
+        : realLs(directoryPath),
+    );
+    const { model, calls } = fakeModel((content) => `T\n${content}`);
+
+    await expect(
+      runBeforeAgent(
+        createWikiTranslationMiddleware(
+          backend,
+          "repository",
+          model,
+          switchTo("zh-CN"),
+        ),
+      ),
+    ).rejects.toThrow("Unable to list /openwiki: EACCES");
+    expect(calls).toHaveLength(0);
+  });
+
+  test("fails a language switch when a nested directory cannot be listed", async () => {
+    const { backend } = await setup("repository");
+    await backend.write("/openwiki/accessible.md", "# Accessible\n");
+    await backend.write("/openwiki/unreadable/page.md", "# Unreadable\n");
+    const realLs = backend.ls.bind(backend);
+    vi.spyOn(backend, "ls").mockImplementation((directoryPath) =>
+      directoryPath === "/openwiki/unreadable"
+        ? Promise.resolve({ error: "EIO: input/output error" })
+        : realLs(directoryPath),
+    );
+    const { model, calls } = fakeModel((content) => `T\n${content}`);
+
+    await expect(
+      runBeforeAgent(
+        createWikiTranslationMiddleware(
+          backend,
+          "repository",
+          model,
+          switchTo("zh-CN"),
+        ),
+      ),
+    ).rejects.toThrow("Unable to list /openwiki/unreadable: EIO");
+    expect(calls).toHaveLength(0);
+  });
 });