diff --git a/public/history.ts b/public/history.ts
new file mode 100644
index 0000000..0955220
--- /dev/null
+++ b/public/history.ts
@@ -0,0 +1,109 @@
+/**
+ * public/history.ts — resume a past Claude Code session (O2).
+ *
+ * A 🕘 toolbar button opens a list of past sessions (GET /sessions); clicking
+ * "Resume" opens a new tab in that project's directory and runs
+ * `claude --resume <id>`.
+ */
+
+export interface HistoryHooks {
+  resume: (cwd: string, id: string) => void
+}
+
+interface HistorySession {
+  id: string
+  cwd: string
+  project: string
+  mtimeMs: number
+  preview: string
+}
+
+function relTime(ms: number): string {
+  const s = Math.max(0, (Date.now() - ms) / 1000)
+  if (s < 60) return 'just now'
+  if (s < 3600) return `${Math.floor(s / 60)}m ago`
+  if (s < 86400) return `${Math.floor(s / 3600)}h ago`
+  return `${Math.floor(s / 86400)}d ago`
+}
+
+export function mountHistory(toolbar: HTMLElement, hooks: HistoryHooks): void {
+  const overlay = document.createElement('div')
+  overlay.id = 'historymodal'
+  overlay.style.display = 'none'
+  const card = document.createElement('div')
+  card.className = 'hist-card'
+  overlay.appendChild(card)
+  document.body.appendChild(overlay)
+
+  const hide = (): void => {
+    overlay.style.display = 'none'
+  }
+  overlay.addEventListener('click', (e) => {
+    if (e.target === overlay) hide()
+  })
+
+  const open = async (): Promise<void> => {
+    card.replaceChildren()
+    const title = document.createElement('div')
+    title.className = 'hist-title'
+    title.textContent = 'Resume a Claude session'
+    card.appendChild(title)
+    const status = document.createElement('div')
+    status.className = 'hist-empty'
+    status.textContent = 'Loading…'
+    card.appendChild(status)
+    overlay.style.display = 'flex'
+
+    let sessions: HistorySession[]
+    try {
+      const res = await fetch('/sessions')
+      sessions = (await res.json()) as HistorySession[]
+    } catch {
+      status.textContent = 'Failed to load sessions.'
+      return
+    }
+    if (sessions.length === 0) {
+      status.textContent = 'No past Claude sessions found.'
+      return
+    }
+    status.remove()
+
+    for (const s of sessions) {
+      const row = document.createElement('div')
+      row.className = 'hist-row'
+
+      const main = document.createElement('div')
+      main.className = 'hist-main'
+      const proj = document.createElement('div')
+      proj.className = 'hist-proj'
+      proj.textContent = `${s.project}  ·  ${relTime(s.mtimeMs)}`
+      const prev = document.createElement('div')
+      prev.className = 'hist-prev'
+      prev.textContent = s.preview || '(no preview)'
+      prev.title = s.cwd
+      main.append(proj, prev)
+
+      const btn = document.createElement('button')
+      btn.className = 'hist-resume'
+      btn.textContent = 'Resume'
+      btn.addEventListener('click', () => {
+        hooks.resume(s.cwd, s.id)
+        hide()
+      })
+
+      row.append(main, btn)
+      card.appendChild(row)
+    }
+  }
+
+  const toggle = document.createElement('button')
+  toggle.className = 'toolbtn'
+  toggle.textContent = '🕘'
+  toggle.title = 'Resume a past Claude session'
+  toggle.setAttribute('aria-label', 'Session history')
+  toggle.addEventListener('click', () => {
+    if (overlay.style.display === 'none') void open()
+    else hide()
+  })
+  toolbar.appendChild(toggle)
+}
diff --git a/public/main.ts b/public/main.ts
index 0361269..b1970c2 100644
--- a/public/main.ts
+++ b/public/main.ts
@@ -17,6 +17,7 @@ import { mountSearch } from './search.js'
 import { mountQrConnect } from './qr.js'
 import { mountSettings, loadSettings, type Settings } from './settings.js'
 import { mountDashboard } from './dashboard.js'
+import { mountHistory } from './history.js'
 
 const paneHost = document.getElementById('term')
 const tabs = document.getElementById('tabs')
@@ -51,6 +52,9 @@ mountDashboard(toolbar, {
   snapshot: () => app.snapshot(),
   focus: (idx) => app.focusTab(idx),
 })
+mountHistory(toolbar, {
+  resume: (cwd, id) => app.newTabForResume(cwd, id),
+})
 mountQrConnect(toolbar)
 
 // PWA: register the service worker (installable + offline shell, M4).
diff --git a/public/style.css b/public/style.css
index 46b45ff..7ac30df 100644
--- a/public/style.css
+++ b/public/style.css
@@ -253,6 +253,73 @@ html, body {
   font-weight: 600;
 }
 
+/* History / resume modal (O2) */
+#historymodal {
+  position: fixed;
+  inset: 0;
+  z-index: 1200;
+  display: flex;
+  align-items: flex-start;
+  justify-content: center;
+  padding-top: 56px;
+  background: rgba(0, 0, 0, 0.6);
+}
+.hist-card {
+  background: #222;
+  border: 1px solid #3a3a3a;
+  border-radius: 10px;
+  min-width: 360px;
+  max-width: 92vw;
+  max-height: 72vh;
+  overflow-y: auto;
+  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.5);
+}
+.hist-title {
+  padding: 12px 16px;
+  font-weight: 600;
+  color: #fff;
+  border-bottom: 1px solid #3a3a3a;
+}
+.hist-empty {
+  padding: 16px;
+  color: #aaa;
+}
+.hist-row {
+  display: flex;
+  align-items: center;
+  gap: 10px;
+  padding: 10px 16px;
+  border-bottom: 1px solid #2a2a2a;
+}
+.hist-main {
+  flex: 1 1 auto;
+  min-width: 0;
+}
+.hist-proj {
+  color: #fff;
+  font-size: 13px;
+}
+.hist-prev {
+  color: #aaa;
+  font-size: 12px;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+.hist-resume {
+  flex: none;
+  background: #2ea043;
+  color: #fff;
+  border: none;
+  border-radius: 5px;
+  padding: 6px 14px;
+  cursor: pointer;
+  font: inherit;
+}
+.hist-resume:hover {
+  background: #3fb950;
+}
+
 .tab {
   display: flex;
   align-items: center;
diff --git a/public/tabs.ts b/public/tabs.ts
index 1b4e423..c886428 100644
--- a/public/tabs.ts
+++ b/public/tabs.ts
@@ -151,7 +151,12 @@ export class TabApp {
 
   /* ── tab lifecycle ───────────────────────────────────────────── */
 
-  private addEntry(sessionId: string | null, customTitle: string | null, cwd?: string): TabEntry {
+  private addEntry(
+    sessionId: string | null,
+    customTitle: string | null,
+    cwd?: string,
+    initialInput?: string,
+  ): TabEntry {
     const entry: TabEntry = {
       session: null as unknown as TerminalSession,
       customTitle,
@@ -162,6 +167,7 @@ export class TabApp {
     entry.session = new TerminalSession({
       sessionId,
       ...(cwd !== undefined ? { cwd } : {}),
+      ...(initialInput !== undefined ? { initialInput } : {}),
       onSessionId: () => this.persist(),
       // onActivity only fires for hidden (inactive) panes (see TerminalSession).
       onActivity: () => {
@@ -198,6 +204,14 @@ export class TabApp {
     this.activate(this.tabs.length - 1)
   }
 
+  /** O2: open a new tab in `cwd` and run `claude --resume <id>`. */
+  newTabForResume(cwd: string, sessionId: string): void {
+    this.addEntry(null, null, cwd || undefined, `claude --resume ${sessionId}`)
+    this.persist()
+    this.rebuild()
+    this.activate(this.tabs.length - 1)
+  }
+
   activate(i: number): void {
     if (i < 0 || i >= this.tabs.length) return
     this.maybeAskNotify() // first switch is a user gesture — request notif permission
diff --git a/public/terminal-session.ts b/public/terminal-session.ts
index e58709d..591a57c 100644
--- a/public/terminal-session.ts
+++ b/public/terminal-session.ts
@@ -54,6 +54,8 @@ export interface TerminalSessionOpts {
   onClaudeStatus?: (status: ClaudeStatus, detail?: string) => void
   /** Optional: spawn a NEW session in this directory ("new tab here", M6). */
   cwd?: string
+  /** Optional: type this once the new session's shell is ready (O2 resume). */
+  initialInput?: string
 }
 
 export class TerminalSession {
@@ -69,6 +71,8 @@ export class TerminalSession {
   private readonly onStatus: ((status: SessionStatus) => void) | undefined
   private readonly onClaudeStatus: ((status: ClaudeStatus, detail?: string) => void) | undefined
   private readonly spawnCwd: string | undefined
+  private readonly initialInput: string | undefined
+  private initialSent = false
   private statusValue: SessionStatus = 'connecting'
   private claudeStatusValue: ClaudeStatus = 'unknown'
   private cwdValue: string | null = null
@@ -94,6 +98,7 @@ export class TerminalSession {
     this.onStatus = opts.onStatus
     this.onClaudeStatus = opts.onClaudeStatus
     this.spawnCwd = opts.cwd
+    this.initialInput = opts.initialInput
 
     this.el = document.createElement('div')
     this.el.className = 'term-pane'
@@ -238,6 +243,12 @@ export class TerminalSession {
         this.onSessionId(msg.sessionId)
         const dims = this.safefit()
         if (dims !== null) this.sendResize(dims.cols, dims.rows)
+        // O2: once the shell is up, type the resume command (only on first attach).
+        if (this.initialInput !== undefined && !this.initialSent) {
+          this.initialSent = true
+          const cmd = this.initialInput
+          setTimeout(() => this.send(cmd), 700)
+        }
         break
       }
       case 'output': {
diff --git a/src/http/history.ts b/src/http/history.ts
new file mode 100644
index 0000000..48b3fea
--- /dev/null
+++ b/src/http/history.ts
@@ -0,0 +1,121 @@
+/**
+ * src/http/history.ts (O2) — list past Claude Code sessions for the resume browser.
+ *
+ * Reads ~/.claude/projects/<encoded>/<session-uuid>.jsonl. Each session's first
+ * user message is the preview and its `cwd` is the project directory (so resume
+ * can `claude --resume <id>` in the right place). Read-only; best-effort.
+ */
+
+import fs from 'node:fs';
+import os from 'node:os';
+import path from 'node:path';
+
+export interface HistorySession {
+  id: string;
+  cwd: string;
+  project: string; // last path segment, for display
+  mtimeMs: number;
+  preview: string;
+}
+
+/** Extract cwd + the first real user prompt from a session jsonl (pure, testable). */
+export function parseSessionMeta(jsonlText: string): { cwd: string | null; preview: string } {
+  let cwd: string | null = null;
+  let preview = '';
+
+  for (const line of jsonlText.split('\n')) {
+    const trimmed = line.trim();
+    if (trimmed === '') continue;
+    let obj: Record<string, unknown>;
+    try {
+      obj = JSON.parse(trimmed) as Record<string, unknown>;
+    } catch {
+      continue;
+    }
+
+    if (cwd === null && typeof obj['cwd'] === 'string') cwd = obj['cwd'];
+
+    if (preview === '' && obj['type'] === 'user') {
+      const msg = obj['message'];
+      if (msg !== null && typeof msg === 'object') {
+        const content = (msg as Record<string, unknown>)['content'];
+        if (typeof content === 'string') {
+          preview = content;
+        } else if (Array.isArray(content)) {
+          for (const part of content) {
+            if (part !== null && typeof part === 'object') {
+              const p = part as Record<string, unknown>;
+              if (p['type'] === 'text' && typeof p['text'] === 'string') {
+                preview = p['text'];
+                break;
+              }
+            }
+          }
+        }
+      }
+    }
+
+    if (cwd !== null && preview !== '') break;
+  }
+
+  return { cwd, preview: preview.replace(/\s+/g, ' ').trim().slice(0, 120) };
+}
+
+function readHead(file: string, max: number): string {
+  try {
+    const fd = fs.openSync(file, 'r');
+    try {
+      const buf = Buffer.alloc(max);
+      const n = fs.readSync(fd, buf, 0, max, 0);
+      return buf.subarray(0, n).toString('utf8');
+    } finally {
+      fs.closeSync(fd);
+    }
+  } catch {
+    return '';
+  }
+}
+
+/** Most-recently-modified Claude Code sessions across all projects. */
+export function listSessions(limit = 50): HistorySession[] {
+  const root = path.join(os.homedir(), '.claude', 'projects');
+  let dirs: string[];
+  try {
+    dirs = fs.readdirSync(root);
+  } catch {
+    return [];
+  }
+
+  const files: Array<{ id: string; file: string; mtimeMs: number }> = [];
+  for (const dir of dirs) {
+    const dirPath = path.join(root, dir);
+    let names: string[];
+    try {
+      names = fs.readdirSync(dirPath);
+    } catch {
+      continue;
+    }
+    for (const name of names) {
+      if (!name.endsWith('.jsonl')) continue;
+      try {
+        const st = fs.statSync(path.join(dirPath, name));
+        files.push({
+          id: name.slice(0, -'.jsonl'.length),
+          file: path.join(dirPath, name),
+          mtimeMs: st.mtimeMs,
+        });
+      } catch {
+        // skip unreadable
+      }
+    }
+  }
+
+  files.sort((a, b) => b.mtimeMs - a.mtimeMs);
+
+  return files.slice(0, limit).map((f) => {
+    const meta = parseSessionMeta(readHead(f.file, 256 * 1024));
+    const cwd = meta.cwd ?? '';
+    const project = cwd !== '' ? (cwd.split('/').filter(Boolean).pop() ?? cwd) : 'unknown';
+    return { id: f.id, cwd, project, mtimeMs: f.mtimeMs, preview: meta.preview };
+  });
+}
diff --git a/src/server.ts b/src/server.ts
index 9d32ea4..ba8fad0 100644
--- a/src/server.ts
+++ b/src/server.ts
@@ -37,6 +37,7 @@ import { loadConfig } from './config.js'
 import { parseClientMessage, serialize } from './protocol.js'
 import { isOriginAllowed } from './http/origin.js'
 import { parseHookEvent } from './http/hook.js'
+import { listSessions } from './http/history.js'
 import { createSessionManager } from './session/manager.js'
 import { detachWs, writeInput, resize } from './session/session.js'
 import type { Config } from './types.js'
@@ -105,6 +106,11 @@ export function startServer(cfg: Config): { close(): Promise<void> } {
   const publicDir = path.join(__dirname, '..', 'public')
   app.use(express.static(publicDir))
 
+  // ── Claude Code history (O2) — list past sessions for the resume browser ──
+  app.get('/sessions', (_req, res) => {
+    res.json(listSessions(50))
+  })
+
   // ── Claude Code hook side-channel (H2) ────────────────────────────────────
   // Hooks running inside a spawned shell POST status here (loopback only — the
   // shell runs on the host). sessionId arrives in the X-Webterm-Session header.
diff --git a/test/history.test.ts b/test/history.test.ts
new file mode 100644
index 0000000..7136f07
--- /dev/null
+++ b/test/history.test.ts
@@ -0,0 +1,33 @@
+import { describe, it, expect } from 'vitest'
+import { parseSessionMeta } from '../src/http/history.js'
+
+describe('parseSessionMeta', () => {
+  it('extracts cwd and the first user prompt (string content)', () => {
+    const jsonl = [
+      JSON.stringify({ type: 'last-prompt', sessionId: 'x' }),
+      JSON.stringify({ type: 'attachment', cwd: '/Users/me/proj', sessionId: 'x' }),
+      JSON.stringify({ type: 'user', message: { role: 'user', content: 'Add monitoring please' } }),
+    ].join('\n')
+    expect(parseSessionMeta(jsonl)).toEqual({ cwd: '/Users/me/proj', preview: 'Add monitoring please' })
+  })
+
+  it('reads the first text block when content is an array', () => {
+    const jsonl = [
+      JSON.stringify({ type: 'user', cwd: '/p', message: { role: 'user', content: [{ type: 'text', text: 'hello there' }] } }),
+    ].join('\n')
+    expect(parseSessionMeta(jsonl)).toEqual({ cwd: '/p', preview: 'hello there' })
+  })
+
+  it('collapses whitespace and truncates long previews to 120 chars', () => {
+    const long = 'a'.repeat(200)
+    const jsonl = JSON.stringify({ type: 'user', cwd: '/p', message: { role: 'user', content: `line1\n   line2   ${long}` } })
+    const { preview } = parseSessionMeta(jsonl)
+    expect(preview.length).toBe(120)
+    expect(preview.startsWith('line1 line2 ')).toBe(true)
+  })
+
+  it('returns nulls/empty when there is no cwd or user message', () => {
+    expect(parseSessionMeta('')).toEqual({ cwd: null, preview: '' })
+    expect(parseSessionMeta('not json\n{"type":"summary"}')).toEqual({ cwd: null, preview: '' })
+  })
+})