diff --git a/packages/app/e2e/browser/composer-email-mentions.spec.ts b/packages/app/e2e/browser/composer-email-mentions.spec.ts
new file mode 100644
index 0000000000..29b0686c20
--- /dev/null
+++ b/packages/app/e2e/browser/composer-email-mentions.spec.ts
@@ -0,0 +1,55 @@
+import { expect, test, type Page } from "../support/fixtures";
+import {
+  composerLocator,
+  expectComposerDraft,
+  expectComposerVisible,
+  fillComposerDraft,
+} from "../support/helpers/composer";
+import { openAgentRoute, seedMockAgentWorkspace } from "../support/helpers/mock-agent";
+
+// The popover has no semantic role; its rows are React Native Pressables.
+function fileSuggestions(page: Page) {
+  return page.getByTestId("composer-autocomplete-popover");
+}
+
+async function selectReadmeMention(page: Page): Promise<void> {
+  await fillComposerDraft(page, "@README");
+  await expect(fileSuggestions(page).getByText("README.md", { exact: true })).toBeVisible();
+  await expect(fileSuggestions(page).getByText("example.com", { exact: true })).toHaveCount(0);
+  await composerLocator(page).press("Enter");
+  await expectComposerDraft(page, '"README.md"');
+}
+
+async function sendEmailIntact(page: Page, email: string): Promise<void> {
+  await fillComposerDraft(page, email);
+  await expect(fileSuggestions(page)).not.toBeVisible();
+  await composerLocator(page).press("Enter");
+  await expectComposerDraft(page, "");
+  await expect(page.getByText(email, { exact: true })).toBeVisible();
+}
+
+for (const email of [
+  "user <12345+user@noreply.example.com>",
+  "alice@example.com",
+  "noreply+@example.com",
+]) {
+  test(`Enter sends ${email} intact and still completes file mentions`, async ({ page }) => {
+    const agent = await seedMockAgentWorkspace({
+      repoPrefix: "composer-email-",
+      title: "Email mention regression",
+      repo: { files: [{ path: "example.com", content: "A file matching the email domain.\n" }] },
+    });
+    try {
+      await openAgentRoute(page, agent);
+      await expectComposerVisible(page);
+      await test.step("complete a workspace file mention with Enter", async () => {
+        await selectReadmeMention(page);
+      });
+      await test.step("send an email without offering or inserting workspace files", async () => {
+        await sendEmailIntact(page, email);
+      });
+    } finally {
+      await agent.cleanup();
+    }
+  });
+}
diff --git a/packages/app/src/utils/file-mention-autocomplete.test.ts b/packages/app/src/utils/file-mention-autocomplete.test.ts
index 4f818e25e2..c74c821522 100644
--- a/packages/app/src/utils/file-mention-autocomplete.test.ts
+++ b/packages/app/src/utils/file-mention-autocomplete.test.ts
@@ -48,6 +48,74 @@ describe("findActiveFileMention", () => {
     });
     expect(mention).toBeNull();
   });
+
+  it("returns null for the issue #1364 angle-bracket email example", () => {
+    const text = "user <12345+user@noreply.example.com>";
+    const mention = findActiveFileMention({
+      text,
+      cursorIndex: text.length,
+    });
+    expect(mention).toBeNull();
+  });
+
+  it("returns null for email addresses (word char before @)", () => {
+    const text = "alice@example.com";
+    const mention = findActiveFileMention({
+      text,
+      cursorIndex: text.length,
+    });
+    expect(mention).toBeNull();
+  });
+
+  it("returns null for email addresses (+ immediately before @)", () => {
+    // Local part ends with + so the character at index-1 is '+', not a word char.
+    const text = "noreply+@example.com";
+    const mention = findActiveFileMention({
+      text,
+      cursorIndex: text.length,
+    });
+    expect(mention).toBeNull();
+  });
+
+  it("returns null for plus-tagged email local parts", () => {
+    const text = "noreply+tag@example.com";
+    const mention = findActiveFileMention({
+      text,
+      cursorIndex: text.length,
+    });
+    expect(mention).toBeNull();
+  });
+
+  it("returns null when query contains angle brackets", () => {
+    const text = "check @foo<bar> end";
+    const mention = findActiveFileMention({
+      text,
+      cursorIndex: text.indexOf(" end"),
+    });
+    expect(mention).toBeNull();
+  });
+
+  it("returns null when query ends with a closing angle bracket", () => {
+    const text = "check @foo>";
+    const mention = findActiveFileMention({
+      text,
+      cursorIndex: text.length,
+    });
+    expect(mention).toBeNull();
+  });
+
+  it("still detects a file mention after an email in the same input", () => {
+    const text = "user <12345+user@noreply.example.com> and also @file";
+    const mention = findActiveFileMention({
+      text,
+      cursorIndex: text.length,
+    });
+    expect(mention).toEqual({
+      start: text.lastIndexOf("@"),
+      end: text.length,
+      query: "file",
+    });
+  });
 });
 
 describe("formatQuotedFileMentionPath", () => {
diff --git a/packages/app/src/utils/file-mention-autocomplete.ts b/packages/app/src/utils/file-mention-autocomplete.ts
index d19424cfe4..fe09b52f03 100644
--- a/packages/app/src/utils/file-mention-autocomplete.ts
+++ b/packages/app/src/utils/file-mention-autocomplete.ts
@@ -15,7 +15,7 @@ interface ApplyFileMentionReplacementInput {
   relativePath: string;
 }
 
-const INVALID_MENTION_QUERY_CHARS = /[\s\n\r\t"']/;
+const INVALID_MENTION_QUERY_CHARS = /[\s\n\r\t"'<>]/;
 
 export function findActiveFileMention(input: FindActiveFileMentionInput): FileMentionRange | null {
   const clampedCursor = Math.max(0, Math.min(input.cursorIndex, input.text.length));
@@ -26,6 +26,11 @@ export function findActiveFileMention(input: FindActiveFileMentionInput): FileMe
     atIndex >= 0;
     atIndex = atIndex === 0 ? -1 : beforeCursor.lastIndexOf("@", atIndex - 1)
   ) {
+    // Skip @ that looks like part of an email address (local-part char immediately before @).
+    if (atIndex > 0 && /[\w+]/.test(beforeCursor[atIndex - 1]!)) {
+      continue;
+    }
+
     const query = beforeCursor.slice(atIndex + 1);
     if (INVALID_MENTION_QUERY_CHARS.test(query)) {
       continue;