From 97e6256c0e6db8a347757bb97fd745247cc7d5ce Mon Sep 17 00:00:00 2001
From: Linus Rath <139418639+rathlinus@users.noreply.github.com>
Date: Tue, 3 Nov 2026 04:51:20 +0100
Subject: [PATCH] fix: show the inbox in the demo when a category tab filters
 on a header

---
 lib/__tests__/demo-client-filter.test.ts | 45 ++++++++++++++++++++++++
 lib/demo/demo-client.ts                  | 15 ++++++--
 2 files changed, 58 insertions(+), 2 deletions(-)
 create mode 100644 lib/__tests__/demo-client-filter.test.ts

diff --git a/lib/__tests__/demo-client-filter.test.ts b/lib/__tests__/demo-client-filter.test.ts
new file mode 100644
index 000000000..33003e4a2
--- /dev/null
+++ b/lib/__tests__/demo-client-filter.test.ts
@@ -0,0 +1,45 @@
+import { describe, expect, it } from 'vitest';
+import { DemoJMAPClient } from '@/lib/demo/demo-client';
+
+// A `header` condition used to be ignored, so it matched every message. The
+// category tabs' Promotions rule has one, which left the default tab (NOT all
+// the other tabs) empty on an Inbox full of mail.
+describe('DemoJMAPClient header filter', () => {
+  async function inboxOf(client: DemoJMAPClient) {
+    return (await client.getMailboxes()).find((m) => m.role === 'inbox')!;
+  }
+
+  it('matches only messages that carry the header', async () => {
+    const client = new DemoJMAPClient();
+    const inbox = await inboxOf(client);
+    const all = await client.getEmails(inbox.id, undefined, 500);
+    const listed = await client.getEmails(inbox.id, undefined, 500, 0, undefined, false, { header: ['List-Id'] });
+
+    expect(listed.total).toBeGreaterThan(0);
+    expect(listed.total).toBeLessThan(all.total);
+    for (const e of listed.emails) {
+      expect(Object.keys(e.headers ?? {}).map((h) => h.toLowerCase())).toContain('list-id');
+    }
+  });
+
+  it('compares the value when the condition has one', async () => {
+    const client = new DemoJMAPClient();
+    const inbox = await inboxOf(client);
+    const hit = await client.getEmails(inbox.id, undefined, 500, 0, undefined, false, { header: ['list-id', 'BEACON.meridianlabs'] });
+    const miss = await client.getEmails(inbox.id, undefined, 500, 0, undefined, false, { header: ['List-Id', 'no-such-list'] });
+
+    expect(hit.total).toBeGreaterThan(0);
+    expect(miss.total).toBe(0);
+  });
+
+  it('leaves mail in a default tab that excludes a header rule', async () => {
+    const client = new DemoJMAPClient();
+    const inbox = await inboxOf(client);
+    const primary = await client.getEmails(inbox.id, undefined, 500, 0, undefined, false, {
+      operator: 'NOT',
+      conditions: [{ operator: 'OR', conditions: [{ from: 'mailchimp' }, { header: ['List-Unsubscribe'] }] }],
+    });
+
+    expect(primary.total).toBeGreaterThan(0);
+  });
+});
diff --git a/lib/demo/demo-client.ts b/lib/demo/demo-client.ts
index 8a9377ec4..b1eae913d 100644
--- a/lib/demo/demo-client.ts
+++ b/lib/demo/demo-client.ts
@@ -523,8 +523,9 @@ export class DemoJMAPClient implements IJMAPClient {
   /**
    * Minimal JMAP filter evaluator for demo mode: supports the conditions the
    * message-list category tabs and the folder-less search scopes use
-   * (hasKeyword / notKeyword / from / text / inMailbox / inMailboxOtherThan
-   * and AND / OR / NOT operators). Unknown conditions are ignored.
+   * (hasKeyword / notKeyword / from / text / header / inMailbox /
+   * inMailboxOtherThan and AND / OR / NOT operators). Unknown conditions are
+   * ignored.
    */
   private matchesFilter(e: Email, filter: Record<string, unknown>): boolean {
     if (typeof filter.operator === 'string') {
@@ -564,6 +565,16 @@ export class DemoJMAPClient implements IJMAPClient {
       const bodyText = Object.values(e.bodyValues || {}).map(v => v.value).join(' ').toLowerCase();
       if (!bodyText.includes(q)) return false;
     }
+    // RFC 8621 4.4.1: [name] tests that the header exists, [name, value] that
+    // its value contains the text. Ignoring it would match every message.
+    if (Array.isArray(filter.header) && typeof filter.header[0] === 'string') {
+      const wanted = filter.header[0].toLowerCase();
+      const text = typeof filter.header[1] === 'string' ? filter.header[1].toLowerCase() : null;
+      const match = Object.entries(e.headers ?? {}).some(([name, value]) =>
+        name.toLowerCase() === wanted
+        && (text === null || (Array.isArray(value) ? value : [value]).some(v => String(v).toLowerCase().includes(text))));
+      if (!match) return false;
+    }
     if (typeof filter.inMailbox === 'string' && !e.mailboxIds[filter.inMailbox]) return false;
     if (Array.isArray(filter.inMailboxOtherThan)) {
       const excluded = new Set(filter.inMailboxOtherThan as string[]);