diff --git a/src/apps/officer-web/Screens/Dashboard/Email/EmailList.tsx b/src/apps/officer-web/Screens/Dashboard/Email/EmailList.tsx
index f0f0618a..44482c64 100644
--- a/src/apps/officer-web/Screens/Dashboard/Email/EmailList.tsx
+++ b/src/apps/officer-web/Screens/Dashboard/Email/EmailList.tsx
@@ -300,7 +300,7 @@ export const EmailList = () => {
       ) : (
       <div className="flex flex-1 flex-col divide-y divide-white/10 overflow-y-auto">
         {messages.map((msg: EmailSummary) => {
-          const unread = !msg.read;
+          const unread = msg.threadUnread !== undefined ? msg.threadUnread > 0 : !msg.read;
           return (
           <button
             key={msg.id}
@@ -311,7 +311,14 @@ export const EmailList = () => {
             }`}
           >
             <div className="flex items-center justify-between gap-2">
-              <span className={`truncate text-sm ${unread ? 'font-semibold' : 'font-medium opacity-70'}`}>{msg.from}</span>
+              <div className="flex min-w-0 items-center gap-1.5">
+                <span className={`truncate text-sm ${unread ? 'font-semibold' : 'font-medium opacity-70'}`}>{msg.from}</span>
+                {!!msg.threadCount && (
+                  <span className="shrink-0 rounded-full bg-muted px-1.5 text-xs tabular-nums opacity-60" title={`${msg.threadCount} messages`}>
+                    {msg.threadCount}
+                  </span>
+                )}
+              </div>
               <span className="shrink-0 text-xs opacity-50">{formatDate(msg.date)}</span>
             </div>
             <span className={`truncate text-sm ${unread ? 'font-medium' : 'opacity-70'}`}>{msg.subject}</span>
diff --git a/src/apps/officer-web/Screens/Dashboard/Email/EmailReader.tsx b/src/apps/officer-web/Screens/Dashboard/Email/EmailReader.tsx
index e1bb78b2..d8708c01 100644
--- a/src/apps/officer-web/Screens/Dashboard/Email/EmailReader.tsx
+++ b/src/apps/officer-web/Screens/Dashboard/Email/EmailReader.tsx
@@ -1,11 +1,11 @@
 import { useEffect, useRef, useState } from 'react';
 import { useQuery, useQueryClient } from '@tanstack/react-query';
-import { Mail, Reply } from 'lucide-react';
+import { Mail, Reply, Paperclip } from 'lucide-react';
 import { FileViewerProvider, FileViewerHeader, FileViewerBody } from 'officerdev';
 import { Dialog, DialogContent, DialogTitle } from '@/components/ui/dialog';
 import { useClient } from 'hooks/useClient';
 import { useGlobal } from 'hooks/useGlobal';
-import type { EmailMessage } from 'types';
+import type { EmailMessage, EmailThread } from 'types';
 import { useComposer, replyDraft } from './Compose';
 
 type OpenAttachment = {
@@ -14,6 +14,8 @@ type OpenAttachment = {
   root: string;
 };
 
+const senderName = (from: string) => from.replace(/\s*<[^>]+>$/, '').trim() || from;
+
 const HtmlBody = ({ html }: { html: string }) => {
   const iframeRef = useRef<HTMLIFrameElement>(null);
 
@@ -37,9 +39,84 @@ const HtmlBody = ({ html }: { html: string }) => {
       </html>
     `);
     doc.close();
+    // Auto-size to content so each message sits at its natural height inside the stacked thread.
+    const resize = () => {
+      if (doc.body) iframe.style.height = `${doc.body.scrollHeight + 8}px`;
+    };
+    resize();
+    doc.querySelectorAll('img').forEach((img) => img.addEventListener('load', resize));
+    const t = setTimeout(resize, 300);
+    return () => clearTimeout(t);
   }, [html]);
 
-  return <iframe ref={iframeRef} className="h-full w-full border-0" sandbox="allow-same-origin" title="Email body" />;
+  return <iframe ref={iframeRef} className="w-full border-0" sandbox="allow-same-origin" title="Email body" />;
+};
+
+type MessagePanelProps = {
+  message: EmailMessage;
+  open: boolean;
+  onToggle: () => void;
+  onReply: () => void;
+  onOpenAttachment: (index: number) => void;
+};
+
+const MessagePanel = ({ message, open, onToggle, onReply, onOpenAttachment }: MessagePanelProps) => {
+  if (!open) {
+    return (
+      <button onClick={onToggle} className="flex w-full items-center gap-2 px-4 py-2.5 text-left hover:bg-accent/40 cursor-pointer">
+        <span className={`shrink-0 text-sm ${message.read ? 'opacity-70' : 'font-semibold'}`}>{senderName(message.from)}</span>
+        <span className="min-w-0 flex-1 truncate text-xs opacity-50">{message.snippet}</span>
+        {!!message.attachmentCount && <Paperclip className="h-3 w-3 shrink-0 opacity-40" />}
+        <span className="shrink-0 text-xs opacity-50">{new Date(message.date).toLocaleDateString()}</span>
+      </button>
+    );
+  }
+
+  return (
+    <div className="flex flex-col">
+      <div className="flex items-start justify-between gap-3 px-4 py-2.5">
+        <button onClick={onToggle} className="min-w-0 flex-1 text-left cursor-pointer">
+          <div className="flex flex-col gap-0.5 text-sm opacity-80">
+            <div>
+              <span className="font-medium">{message.from}</span>
+            </div>
+            <div className="text-xs opacity-70">
+              <span className="font-medium">To:</span> {message.to}
+            </div>
+            {message.cc && (
+              <div className="text-xs opacity-70">
+                <span className="font-medium">Cc:</span> {message.cc}
+              </div>
+            )}
+            <div className="text-xs opacity-60">{new Date(message.date).toLocaleString()}</div>
+          </div>
+        </button>
+        <button
+          onClick={onReply}
+          className="shrink-0 flex items-center gap-1 rounded-md border px-2.5 py-1 text-xs hover:bg-accent cursor-pointer"
+          title="Reply"
+        >
+          <Reply className="h-3.5 w-3.5" /> Reply
+        </button>
+      </div>
+
+      {message.attachments.length > 0 && (
+        <div className="flex flex-wrap gap-1.5 px-4 pb-2">
+          {message.attachments.map((att, i) => (
+            <button
+              key={i}
+              className="cursor-pointer rounded bg-accent px-2 py-0.5 text-xs hover:bg-accent/80"
+              onClick={() => onOpenAttachment(i)}
+            >
+              {att.filename} ({Math.round(att.size / 1024)}KB)
+            </button>
+          ))}
+        </div>
+      )}
+
+      {message.html ? <HtmlBody html={message.html} /> : <pre className="whitespace-pre-wrap px-4 pb-4 text-sm">{message.text}</pre>}
+    </div>
+  );
 };
 
 export const EmailReader = () => {
@@ -48,27 +125,42 @@ export const EmailReader = () => {
   const [, openCompose] = useComposer();
   const [selectedId] = useGlobal<string | null>('EMAIL_SELECTED', null);
   const [openAttachment, setOpenAttachment] = useState<OpenAttachment | null>(null);
+  const [expanded, setExpanded] = useState<Set<string>>(new Set());
 
-  const { data: message, isLoading } = useQuery({
-    queryKey: ['email-message', selectedId],
-    queryFn: () => client.get<EmailMessage>(`/email/messages/${selectedId}`),
+  const { data: thread, isLoading } = useQuery({
+    queryKey: ['email-thread', selectedId],
+    queryFn: () => client.get<EmailThread>(`/email/thread/${selectedId}`),
     enabled: !!selectedId,
   });
 
-  // Mark as read when message loads
+  // Whenever the thread changes, expand just the latest message (Gmail-style).
   useEffect(() => {
-    if (!message || message.read) return;
-    client.patch(`/email/messages/${message.id}/read`).then(() => {
-      queryClient.invalidateQueries({ queryKey: ['email-messages'] });
-    }).catch(() => {});
-  }, [message?.id]);
+    const messages = thread?.messages;
+    if (messages?.length) setExpanded(new Set([messages[messages.length - 1]!.id]));
+  }, [thread?.id, thread?.messages.length]);
 
-  const extractAttachment = async (index: number) => {
-    if (!selectedId) return;
-    const result = await client.post<OpenAttachment>(`/email/messages/${selectedId}/attachments/${index}/extract`);
+  // Mark the whole conversation as read when opened.
+  useEffect(() => {
+    if (!thread || !selectedId || !thread.messages.some((m: EmailMessage) => !m.read)) return;
+    client
+      .patch(`/email/thread/${selectedId}/read`)
+      .then(() => queryClient.invalidateQueries({ queryKey: ['email-messages'] }))
+      .catch(() => {});
+  }, [thread?.id]);
+
+  const extractAttachment = async (messageId: string, index: number) => {
+    const result = await client.post<OpenAttachment>(`/email/messages/${messageId}/attachments/${index}/extract`);
     setOpenAttachment(result);
   };
 
+  const toggle = (id: string) =>
+    setExpanded((prev) => {
+      const next = new Set(prev);
+      if (next.has(id)) next.delete(id);
+      else next.add(id);
+      return next;
+    });
+
   if (!selectedId) {
     return (
       <div className="flex h-full flex-col items-center justify-center gap-2 text-sm opacity-50">
@@ -79,73 +171,44 @@ export const EmailReader = () => {
   }
 
   if (isLoading) {
-    return (
-      <div className="flex h-full items-center justify-center text-sm opacity-50">
-        Loading...
-      </div>
-    );
+    return <div className="flex h-full items-center justify-center text-sm opacity-50">Loading...</div>;
   }
 
-  if (!message) return null;
+  if (!thread || thread.messages.length === 0) return null;
+
+  const latest = thread.messages[thread.messages.length - 1]!;
 
   return (
     <div className="flex h-full flex-col overflow-hidden">
-      <div className="flex flex-col gap-1 border-b px-4 py-3">
-        <div className="flex items-start justify-between gap-3">
-          <h2 className="text-lg font-semibold">{message.subject}</h2>
-          <button
-            onClick={() => openCompose(replyDraft(message))}
-            className="shrink-0 flex items-center gap-1 rounded-md border px-2.5 py-1 text-xs hover:bg-accent cursor-pointer"
-            title="Reply"
-          >
-            <Reply className="h-3.5 w-3.5" /> Reply
-          </button>
-        </div>
-        <div className="flex flex-col gap-0.5 text-sm opacity-70">
-          <div>
-            <span className="font-medium">From:</span> {message.from}
-          </div>
-          <div>
-            <span className="font-medium">To:</span> {message.to}
-          </div>
-          {message.cc && (
-            <div>
-              <span className="font-medium">Cc:</span> {message.cc}
-            </div>
-          )}
-          <div className="text-xs opacity-60">{new Date(message.date).toLocaleString()}</div>
-        </div>
-        {message.attachments.length > 0 && (
-          <div className="flex flex-wrap gap-1.5 pt-1">
-            {message.attachments.map((att: { filename: string; size: number; contentType: string }, i: number) => (
-              <button
-                key={i}
-                className="cursor-pointer rounded bg-accent px-2 py-0.5 text-xs hover:bg-accent/80"
-                onClick={() => extractAttachment(i)}
-              >
-                {att.filename} ({Math.round(att.size / 1024)}KB)
-              </button>
-            ))}
-          </div>
-        )}
+      <div className="flex items-start justify-between gap-3 border-b px-4 py-3">
+        <h2 className="text-lg font-semibold">{thread.subject}</h2>
+        <button
+          onClick={() => openCompose(replyDraft(latest))}
+          className="shrink-0 flex items-center gap-1 rounded-md border px-2.5 py-1 text-xs hover:bg-accent cursor-pointer"
+          title="Reply"
+        >
+          <Reply className="h-3.5 w-3.5" /> Reply
+        </button>
       </div>
-      <div className="flex-1 overflow-auto">
-        {message.html ? (
-          <HtmlBody html={message.html} />
-        ) : (
-          <pre className="whitespace-pre-wrap p-4 text-sm">{message.text}</pre>
-        )}
+
+      <div className="flex-1 divide-y divide-white/10 overflow-auto">
+        {thread.messages.map((m: EmailMessage) => (
+          <MessagePanel
+            key={m.id}
+            message={m}
+            open={expanded.has(m.id)}
+            onToggle={() => toggle(m.id)}
+            onReply={() => openCompose(replyDraft(m))}
+            onOpenAttachment={(index) => extractAttachment(m.id, index)}
+          />
+        ))}
       </div>
 
       <Dialog open={!!openAttachment} onOpenChange={(open) => !open && setOpenAttachment(null)}>
         <DialogContent className="flex h-[80vh] max-w-4xl flex-col gap-0 p-0">
           <DialogTitle className="sr-only">{openAttachment?.fileName}</DialogTitle>
           {openAttachment && (
-            <FileViewerProvider
-              filePath={openAttachment.filePath}
-              fileName={openAttachment.fileName}
-              root={openAttachment.root}
-            >
+            <FileViewerProvider filePath={openAttachment.filePath} fileName={openAttachment.fileName} root={openAttachment.root}>
               <div className="flex shrink-0 items-center gap-2 border-b px-4 pr-12 py-1.5">
                 <FileViewerHeader />
               </div>
diff --git a/src/servers/api/email/email-db.ts b/src/servers/api/email/email-db.ts
index 0170aa5d..40c94bb6 100644
--- a/src/servers/api/email/email-db.ts
+++ b/src/servers/api/email/email-db.ts
@@ -1,4 +1,5 @@
 import { Database } from 'bun:sqlite';
+import { createHash } from 'node:crypto';
 import { join } from 'node:path';
 import { chmodSync } from 'node:fs';
 import { DATA_PATH } from '@@/data-path';
@@ -22,7 +23,8 @@ CREATE TABLE IF NOT EXISTS emails (
   attachment_count INTEGER DEFAULT 0,
   read INTEGER DEFAULT 0,
   deleted INTEGER DEFAULT 0,
-  labels TEXT
+  labels TEXT,
+  thread_id TEXT
 );
 
 CREATE TABLE IF NOT EXISTS attachments (
@@ -48,6 +50,7 @@ CREATE INDEX IF NOT EXISTS idx_emails_from_address ON emails(from_address);
 CREATE INDEX IF NOT EXISTS idx_emails_integration ON emails(integration);
 CREATE INDEX IF NOT EXISTS idx_emails_email_account ON emails(email_account);
 CREATE INDEX IF NOT EXISTS idx_emails_labels ON emails(labels);
+CREATE INDEX IF NOT EXISTS idx_emails_thread ON emails(thread_id);
 `;
 
 /** Convert label IDs to lowercase comma-separated string for storage */
@@ -74,6 +77,59 @@ function extractDomain(address: string): string {
   return at >= 0 ? address.slice(at + 1) : '';
 }
 
+// ── Conversation threading ──
+// `id` is sha1(Message-Id) (see resync.messageIdToStableId), so hashing a referenced Message-Id the
+// same way yields the *id of that referenced email*. That makes header-based threading trivial:
+// a reply's thread_id is the hash of its root Message-Id, which equals the root email's own id.
+
+const hashMsgId = (msgId: string): string => createHash('sha1').update(msgId).digest('hex').slice(0, 16);
+
+/** Ordered Message-Ids this email references (References first, root→leaf; else In-Reply-To). */
+function extractReferenceIds(raw: string): string[] {
+  const refs = extractFullHeader(raw, 'References') || extractFullHeader(raw, 'In-Reply-To');
+  return Array.from(refs.matchAll(/<([^>]+)>/g), (m) => m[1]!.trim()).filter(Boolean);
+}
+
+/** Compute a header-based thread_id for a freshly ingested email (falls back to its own id = new thread). */
+function computeThreadId(db: Database, id: string, raw: string): string {
+  const refIds = extractReferenceIds(raw);
+  if (refIds.length === 0) return id; // no ancestors → this email is a thread root
+  const hashed = refIds.map(hashMsgId);
+  // Adopt an ancestor's thread if we already have one stored (robust to In-Reply-To-only clients).
+  const placeholders = hashed.map(() => '?').join(',');
+  const found = db
+    .query(`SELECT thread_id FROM emails WHERE id IN (${placeholders}) AND thread_id IS NOT NULL LIMIT 1`)
+    .get(...hashed) as { thread_id: string } | null;
+  return found?.thread_id ?? hashMsgId(refIds[0]!);
+}
+
+const RE_PREFIX = /^\s*((re|fwd?|aw|wg|sv|vs|res|antw)\s*(\[\d+\])?\s*:\s*)+/i;
+
+/** Normalize a subject for fallback grouping: strip reply/forward prefixes, fold whitespace, lowercase. */
+function normalizeSubject(subject: string): string {
+  return subject.replace(RE_PREFIX, '').replace(/\s+/g, ' ').trim().toLowerCase();
+}
+
+const firstAddress = (value: unknown): string => {
+  if (typeof value !== 'string') return '';
+  const first = value.split(',')[0] ?? '';
+  return (first.match(/<([^>]+)>/)?.[1] ?? first).trim().toLowerCase();
+};
+
+/**
+ * Subject-based thread key for mail synced before header capture (no References available).
+ * Groups by normalized subject + the counterpart address, so recurring 1:1 conversations collapse
+ * while unrelated same-subject mail from different people stays apart. Trivial subjects stay ungrouped.
+ */
+function fallbackThreadId(row: { id: string; subject: unknown; from_address: unknown; to_address: unknown; email_account: unknown }): string {
+  const norm = normalizeSubject(typeof row.subject === 'string' ? row.subject : '');
+  if (!norm) return row.id;
+  const me = typeof row.email_account === 'string' ? row.email_account.toLowerCase() : '';
+  const from = typeof row.from_address === 'string' ? row.from_address.toLowerCase() : '';
+  const counterpart = from && from !== me ? from : firstAddress(row.to_address) || from;
+  return `s:${norm}|${counterpart}`;
+}
+
 export function openEmailDb(email: string): Database {
   const dbPath = join(DATA_PATH, email, 'emails.db');
   const db = new Database(dbPath, { create: true });
@@ -108,6 +164,13 @@ function migrate(db: Database): void {
   if (!colNames.has('labels')) {
     db.exec('ALTER TABLE emails ADD COLUMN labels TEXT');
   }
+  if (!colNames.has('thread_id')) {
+    db.exec('ALTER TABLE emails ADD COLUMN thread_id TEXT');
+  }
+
+  // Backfill thread_id for any rows missing it. Header data isn't kept for already-synced mail, so
+  // these use the subject-based fallback. New mail gets an exact header-based thread_id at insert.
+  backfillThreadIds(db);
 
   // Ensure sync_meta table exists (for DBs created before it was added to SCHEMA_TABLES)
   db.exec('CREATE TABLE IF NOT EXISTS sync_meta (key TEXT PRIMARY KEY, value TEXT)');
@@ -120,6 +183,23 @@ function migrate(db: Database): void {
   }
 }
 
+function backfillThreadIds(db: Database): void {
+  const rows = db
+    .query('SELECT id, subject, from_address, to_address, email_account FROM emails WHERE thread_id IS NULL')
+    .all() as Array<{ id: string; subject: unknown; from_address: unknown; to_address: unknown; email_account: unknown }>;
+  if (rows.length === 0) return;
+
+  const update = db.prepare('UPDATE emails SET thread_id = ? WHERE id = ?');
+  db.exec('BEGIN');
+  try {
+    for (const row of rows) update.run(fallbackThreadId(row), row.id);
+    db.exec('COMMIT');
+  } catch (err) {
+    db.exec('ROLLBACK');
+    throw err;
+  }
+}
+
 // ── Full-text search (FTS5) ──
 // A standalone FTS5 index kept in sync with `emails` on every upsert. unicode61 + diacritic folding
 // gives accent-insensitive matching; per-term prefix queries make it feel incremental.
@@ -267,11 +347,12 @@ type ParsedEmail = {
   text?: string;
   attachments: Array<{ filename: string; size: number; contentType: string; content: string }>;
   labels?: string[];
+  threadId?: string;
 };
 
 const upsertEmailStmt = `
-  INSERT OR REPLACE INTO emails (id, integration, email_account, from_name, from_address, from_domain, to_address, cc, subject, date, snippet, html, text_body, attachment_count, labels)
-  VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+  INSERT OR REPLACE INTO emails (id, integration, email_account, from_name, from_address, from_domain, to_address, cc, subject, date, snippet, html, text_body, attachment_count, labels, thread_id)
+  VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
 `;
 
 const deleteAttachmentsStmt = 'DELETE FROM attachments WHERE email_id = ?';
@@ -298,6 +379,7 @@ export function upsertEmail(db: Database, email: ParsedEmail): void {
       email.text ?? null,
       email.attachments.length,
       labelsToString(email.labels),
+      email.threadId ?? email.id,
     ]);
 
     db.run(deleteAttachmentsStmt, [email.id]);
@@ -338,9 +420,10 @@ export function upsertFromRawEml({ db, id, raw, integration, emailAccount, label
   const domain = extractDomain(address);
 
   const { html, text } = extractBody(raw);
+  const threadId = computeThreadId(db, id, raw);
 
   db.run(upsertEmailStmt, [
-    id, integration, emailAccount, name, address, domain, to, cc, subject, date, snippet, html, text, attachments.length, labelsToString(labels),
+    id, integration, emailAccount, name, address, domain, to, cc, subject, date, snippet, html, text, attachments.length, labelsToString(labels), threadId,
   ]);
 
   if (attachments.length > 0) {
@@ -372,6 +455,8 @@ export function rowToSummary(row: Record<string, unknown>): EmailSummary {
     ...(row.attachment_count ? { attachmentCount: row.attachment_count as number } : {}),
     ...(row.read ? { read: true } : {}),
     ...(labels ? { labels } : {}),
+    ...(row.thread_count && (row.thread_count as number) > 1 ? { threadCount: row.thread_count as number } : {}),
+    ...(row.thread_unread ? { threadUnread: row.thread_unread as number } : {}),
   };
 }
 
diff --git a/src/servers/api/email/email.ts b/src/servers/api/email/email.ts
index 29759df7..1eba832b 100644
--- a/src/servers/api/email/email.ts
+++ b/src/servers/api/email/email.ts
@@ -173,10 +173,24 @@ emailRouter.get('/messages', async (ctx) => {
 
   const db = openEmailDb(email);
   try {
+    // One row per conversation: the latest message in each thread within this folder, plus the
+    // thread's message count and how many are unread. COALESCE guards any un-backfilled rows.
     const rows = db
-      .query(`SELECT * FROM emails WHERE ${folderWhere} ORDER BY date DESC LIMIT ? OFFSET ?`)
+      .query(
+        `SELECT * FROM (
+           SELECT e.*,
+             COUNT(*) OVER (PARTITION BY COALESCE(thread_id, id)) AS thread_count,
+             SUM(CASE WHEN read = 0 THEN 1 ELSE 0 END) OVER (PARTITION BY COALESCE(thread_id, id)) AS thread_unread,
+             ROW_NUMBER() OVER (PARTITION BY COALESCE(thread_id, id) ORDER BY date DESC, id DESC) AS rn
+           FROM emails e
+           WHERE ${folderWhere}
+         ) WHERE rn = 1
+         ORDER BY date DESC LIMIT ? OFFSET ?`,
+      )
       .all(limit, offset) as Record<string, unknown>[];
-    const countRow = db.query(`SELECT COUNT(*) as total FROM emails WHERE ${folderWhere}`).get() as { total: number };
+    const countRow = db
+      .query(`SELECT COUNT(DISTINCT COALESCE(thread_id, id)) as total FROM emails WHERE ${folderWhere}`)
+      .get() as { total: number };
     const messages = rows.map(rowToSummary);
     return ctx.json({ messages, total: countRow.total });
   } finally {
@@ -184,6 +198,32 @@ emailRouter.get('/messages', async (ctx) => {
   }
 });
 
+function buildMessage(db: ReturnType<typeof openEmailDb>, row: Record<string, unknown>): EmailMessage {
+  const attachmentRows = db.query('SELECT * FROM attachments WHERE email_id = ? ORDER BY idx').all(row.id as string) as Array<
+    Record<string, unknown>
+  >;
+  const from = row.from_name ? `${row.from_name} <${row.from_address}>` : (row.from_address as string);
+  return {
+    id: row.id as string,
+    from,
+    to: row.to_address as string,
+    cc: (row.cc as string) ?? undefined,
+    subject: row.subject as string,
+    date: row.date as string,
+    snippet: row.snippet as string,
+    html: (row.html as string) ?? undefined,
+    text: (row.text_body as string) ?? undefined,
+    attachments: attachmentRows.map((a) => ({
+      filename: a.filename as string,
+      size: a.size as number,
+      contentType: a.content_type as string,
+    })),
+    ...(row.attachment_count ? { attachmentCount: row.attachment_count as number } : {}),
+    ...(row.read ? { read: true } : {}),
+    ...(row.labels ? { labels: (row.labels as string).split(',') } : {}),
+  };
+}
+
 emailRouter.get('/messages/:id', async (ctx) => {
   const email = ctx.get('user').email;
   const id = ctx.req.param('id');
@@ -192,34 +232,47 @@ emailRouter.get('/messages/:id', async (ctx) => {
   try {
     const row = db.query('SELECT * FROM emails WHERE id = ? AND deleted = 0').get(id) as Record<string, unknown> | null;
     if (!row) return ctx.text('Not found', 404);
+    return ctx.json(buildMessage(db, row));
+  } finally {
+    db.close();
+  }
+});
 
-    const attachmentRows = db.query('SELECT * FROM attachments WHERE email_id = ? ORDER BY idx').all(id) as Array<
-      Record<string, unknown>
-    >;
+// GET /thread/:id — the full conversation containing message :id, oldest message first.
+emailRouter.get('/thread/:id', (ctx) => {
+  const email = ctx.get('user').email;
+  const id = ctx.req.param('id');
 
-    const from = row.from_name ? `${row.from_name} <${row.from_address}>` : (row.from_address as string);
+  const db = openEmailDb(email);
+  try {
+    const head = db.query('SELECT thread_id, subject FROM emails WHERE id = ? AND deleted = 0').get(id) as
+      | { thread_id: string | null; subject: string }
+      | null;
+    if (!head) return ctx.text('Not found', 404);
 
-    const message: EmailMessage = {
-      id: row.id as string,
-      from,
-      to: row.to_address as string,
-      cc: (row.cc as string) ?? undefined,
-      subject: row.subject as string,
-      date: row.date as string,
-      snippet: row.snippet as string,
-      html: (row.html as string) ?? undefined,
-      text: (row.text_body as string) ?? undefined,
-      attachments: attachmentRows.map((a) => ({
-        filename: a.filename as string,
-        size: a.size as number,
-        contentType: a.content_type as string,
-      })),
-      ...(row.attachment_count ? { attachmentCount: row.attachment_count as number } : {}),
-      ...(row.read ? { read: true } : {}),
-      ...(row.labels ? { labels: (row.labels as string).split(',') } : {}),
-    };
+    const threadKey = head.thread_id ?? id;
+    const rows = db
+      .query('SELECT * FROM emails WHERE COALESCE(thread_id, id) = ? AND deleted = 0 ORDER BY date ASC')
+      .all(threadKey) as Record<string, unknown>[];
+    const messages = rows.map((row) => buildMessage(db, row));
+    return ctx.json({ id, subject: head.subject, messages });
+  } finally {
+    db.close();
+  }
+});
 
-    return ctx.json(message);
+// PATCH /thread/:id/read — mark every message in the conversation as read.
+emailRouter.patch('/thread/:id/read', (ctx) => {
+  const email = ctx.get('user').email;
+  const id = ctx.req.param('id');
+
+  const db = openEmailDb(email);
+  try {
+    const head = db.query('SELECT thread_id FROM emails WHERE id = ?').get(id) as { thread_id: string | null } | null;
+    if (!head) return ctx.text('Not found', 404);
+    const threadKey = head.thread_id ?? id;
+    db.run('UPDATE emails SET read = 1 WHERE COALESCE(thread_id, id) = ? AND read = 0', [threadKey]);
+    return ctx.json({ ok: true });
   } finally {
     db.close();
   }
diff --git a/src/workspaces/types/email.ts b/src/workspaces/types/email.ts
index e42d70e8..b910c1b5 100644
--- a/src/workspaces/types/email.ts
+++ b/src/workspaces/types/email.ts
@@ -9,6 +9,9 @@ export type EmailSummary = {
   read?: boolean;
   fromDomain?: string;
   labels?: string[];
+  // Conversation grouping: total messages in the thread, and how many are unread (folder view only).
+  threadCount?: number;
+  threadUnread?: number;
 };
 
 export type EmailMessage = EmailSummary & {
@@ -17,3 +20,10 @@ export type EmailMessage = EmailSummary & {
   text?: string;
   attachments: Array<{ filename: string; size: number; contentType: string }>;
 };
+
+// A full conversation: every non-deleted message in the thread, oldest first.
+export type EmailThread = {
+  id: string; // the representative message id used to open the thread
+  subject: string;
+  messages: EmailMessage[];
+};
diff --git a/src/workspaces/types/index.ts b/src/workspaces/types/index.ts
index 0189154a..7e164ea2 100644
--- a/src/workspaces/types/index.ts
+++ b/src/workspaces/types/index.ts
@@ -2,7 +2,7 @@ export type {} from './globals';
 export * from 'officerdb/types';
 
 export type { Job, JobStep, JobStatus, JobStepStatus, JobProgress } from './queue';
-export type { EmailSummary, EmailMessage } from './email';
+export type { EmailSummary, EmailMessage, EmailThread } from './email';
 
 export type SelectOption = { value: number | string; label?: string; href?: string };