From 9c346033765fc10e6e9afb815a66c793c2f53195 Mon Sep 17 00:00:00 2001
From: kevin9327 <5299031+kevin9327@users.noreply.github.com>
Date: Mon, 5 Oct 2026 14:33:52 +0900
Subject: [PATCH] fix: decode mail bodies with an unknown charset as UTF-8
 instead of failing the list

---
 packages/integrations/src/google.ts | 10 +++++++++-
 tests/google.test.ts                | 29 +++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/packages/integrations/src/google.ts b/packages/integrations/src/google.ts
index cb21f2c54..3bacea7f7 100644
--- a/packages/integrations/src/google.ts
+++ b/packages/integrations/src/google.ts
@@ -270,6 +270,14 @@ function htmlToPlainText(html: string): string {
     .replace(/\n{3,}/g, "\n\n")
     .trim();
 }
+/** UTF-8 when the declared charset is not one TextDecoder knows (`unknown-8bit`, `utf-7`). */
+function decoderFor(charset: string): TextDecoder {
+  try {
+    return new TextDecoder(charset);
+  } catch {
+    return new TextDecoder();
+  }
+}
 function mapMessage(message: z.infer<typeof messageSchema>): Mail {
   const metadata = headers(message.payload);
   const plain: string[] = [];
@@ -290,7 +298,7 @@ function mapMessage(message: z.infer<typeof messageSchema>): Mail {
         headers(part)
           .get("content-type")
           ?.match(/charset=["']?([^;"'\s]+)/i)?.[1] ?? "utf-8";
-      const text = new TextDecoder(charset).decode(decodeBase64url(part.body.data, 1024 * 1024));
+      const text = decoderFor(charset).decode(decodeBase64url(part.body.data, 1024 * 1024));
       if (part.mimeType === "text/plain") plain.push(text);
       else html.push(htmlToPlainText(text));
     }
diff --git a/tests/google.test.ts b/tests/google.test.ts
index 9b2e64569..233eb563f 100644
--- a/tests/google.test.ts
+++ b/tests/google.test.ts
@@ -88,6 +88,35 @@ test("mail reads nested plain text and attachment references over authenticated
   assert.deepEqual(mail.attachments, ["msg1:attach1:Permission%3A%20form.pdf"]);
 });
 
+test("a body charset TextDecoder does not know falls back to UTF-8 instead of failing the list", async () => {
+  const charsets: Record<string, string> = { known: "utf-8", unknown: "unknown-8bit" };
+  const bodies: Record<string, string> = { known: "Opening hours", unknown: "Café tickets" };
+  const client = clientWith((request) => {
+    const url = new URL(request.url);
+    if (url.pathname.endsWith("/messages"))
+      return json({ messages: [{ id: "known" }, { id: "unknown" }] });
+    const id = url.pathname.split("/").at(-1) ?? "";
+    return json({
+      id,
+      threadId: `thread-${id}`,
+      labelIds: ["INBOX"],
+      payload: {
+        headers: [
+          { name: "From", value: "Museum <museum@example.com>" },
+          { name: "Content-Type", value: `text/plain; charset=${charsets[id]}` },
+        ],
+        mimeType: "text/plain",
+        body: { data: base64url(bodies[id]) },
+      },
+    });
+  });
+  const mail = await client.listMail();
+  assert.deepEqual(
+    mail.map((item) => item.body),
+    ["Opening hours", "Café tickets"],
+  );
+});
+
 test("HTML-only messages expose complete plain text while removing active and non-content elements", async () => {
   let reads = 0;
   const fullText = "Complete museum itinerary. ".repeat(4500);