fix(gmail): honor unnamed attachment dispositions

packages/integrations/src/google.ts

@@ -298,7 +298,11 @@ const wellFormed = (value: string): string =>
   );
 
 function isAttachedPart(part: GmailPart): boolean {
-  return Boolean(part.filename) || part.mimeType === "message/rfc822";
+  return (
+    Boolean(part.filename) ||
+    part.mimeType === "message/rfc822" ||
+    headers(part).get("content-disposition")?.split(";")[0].trim().toLowerCase() === "attachment"
+  );
 }
 
 function mapMessage(message: z.infer<typeof messageSchema>): Mail {
@@ -309,13 +313,17 @@ function mapMessage(message: z.infer<typeof messageSchema>): Mail {
   const visit = (part: GmailPart, depth: number) => {
     if (depth > 30) throw new Error("Gmail message MIME nesting exceeds the limit");
     // Attachments carry their own content (or an attached message); never merge
-    // their parts into the parent text. A remote body has no filename: it is
-    // hydrated above and still counts as message text.
+    // their parts into the parent text. Unattached remote text is hydrated above
+    // and still counts as message text.
     const attached = isAttachedPart(part);
-    if (attached && part.body?.attachmentId)
+    if (attached && part.body?.attachmentId) {
+      const name =
+        part.filename ||
+        (part.mimeType === "message/rfc822" ? "forwarded-message.eml" : "attachment");
       attachments.push(
-        `${message.id}:${part.body.attachmentId}:${encodeURIComponent(wellFormed(part.filename || "forwarded-message.eml"))}`,
+        `${message.id}:${part.body.attachmentId}:${encodeURIComponent(wellFormed(name))}`,
       );
+    }
     if (
       !attached &&
       (part.mimeType === "text/plain" || part.mimeType === "text/html") &&

tests/google-disposition.test.ts

@@ -0,0 +1,78 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+import { GoogleClient } from "../packages/integrations/src/google.ts";
+
+const encoded = (text: string) => Buffer.from(text).toString("base64url");
+
+test("unnamed explicit attachments stay lazy and separate from the parent body", async () => {
+  for (const [mimeType, embedded] of [
+    ["text/plain", false],
+    ["text/plain", true],
+    ["text/html", false],
+    ["multipart/mixed", false],
+  ] as const) {
+    const message = {
+      id: "outer",
+      threadId: "thread1",
+      payload: {
+        mimeType: "multipart/mixed",
+        parts: [
+          { mimeType: "text/plain", body: { data: encoded("Outer body.") } },
+          {
+            mimeType,
+            headers: [
+              { name: "Content-Disposition", value: " Attachment ; creation-date=ignored" },
+            ],
+            body: {
+              attachmentId: "attached",
+              size: 42,
+              ...(embedded ? { data: encoded("Attached text.") } : {}),
+            },
+            parts: [{ mimeType: "text/plain", body: { data: encoded("Attached text.") } }],
+          },
+        ],
+      },
+    };
+    const client = new GoogleClient({
+      getAccessToken: async () => "synthetic-access-token",
+      fetch: async (input) => {
+        const path = new URL(String(input)).pathname;
+        assert.ok(!path.includes("/attachments/"), "opening mail must not fetch an attachment");
+        if (path.endsWith("/messages")) return Response.json({ messages: [{ id: "outer" }] });
+        if (path.includes("/threads/"))
+          return Response.json({ id: "thread1", messages: [message] });
+        return Response.json(message);
+      },
+    });
+    for (const mails of [await client.listMail(), await client.getThread("thread1")]) {
+      assert.equal(mails[0].body, "Outer body.");
+      assert.deepEqual(mails[0].attachments, ["outer:attached:attachment"]);
+    }
+  }
+});
+
+test("inline remote text remains body content instead of an attachment", async () => {
+  for (const disposition of [undefined, "inline", "attachment-preview"]) {
+    const message = {
+      id: "outer",
+      threadId: "thread1",
+      payload: {
+        mimeType: "text/plain",
+        headers: disposition ? [{ name: "Content-Disposition", value: disposition }] : [],
+        body: { attachmentId: "body1", size: 11 },
+      },
+    };
+    const client = new GoogleClient({
+      getAccessToken: async () => "synthetic-access-token",
+      fetch: async (input) => {
+        const path = new URL(String(input)).pathname;
+        if (path.endsWith("/attachments/body1"))
+          return Response.json({ data: encoded("Inline body"), size: 11 });
+        return Response.json({ id: "thread1", messages: [message] });
+      },
+    });
+    const [mail] = await client.getThread("thread1");
+    assert.equal(mail.body, "Inline body");
+    assert.deepEqual(mail.attachments, []);
+  }
+});