feat(web): session detach/undock + beta instance isolation (port 5000)

Detach a session tab into its own browser window and back.

Detach/undock:
- GET /session/:id serves the SPA in "solo mode", reusing the existing
  client (terminal, local-echo overlay, reconnect) so no terminal code is
  duplicated. One PTY already fans out to N SSE/WS clients, so a detached
  window is just another live client — no server fan-out work was needed.
- A pop-out icon per tab; detached tabs show a badge and focus the popup on
  click; closing the popup re-docks. Cross-window state via BroadcastChannel
  plus a WindowProxy poll, and survives a dashboard reload (roll-call).
  app.detachSession(id) is a single idempotent entry point (future gesture
  hook). <base href="/"> so relative assets resolve under /session/:id.

Beta-branch isolation (so it can run alongside a prod Codeman):
- Default port 3000 -> 5000.
- New src/config/instance.ts derives the data dir and tmux socket from
  CODEMAN_INSTANCE (default "beta"): ~/.codeman-beta + tmux -L codeman-beta.
  Every ~/.codeman path now goes through dataPath()/getDataDir() (state,
  mux-sessions, settings, push keys, lifecycle log, screenshots, certs,
  linked-cases, subagent window state). Overridable via CODEMAN_INSTANCE /
  CODEMAN_DATA_DIR / CODEMAN_TMUX_SOCKET. Prevents a second instance from
  discovering and attaching PTYs to the first instance's live tmux sessions.

Verified: tsc / eslint / prettier / lockfile clean; Playwright E2E (27 checks)
for detach/solo/redock; default isolation confirmed to see zero real sessions.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -72,7 +72,7 @@ Codeman is a Claude Code session manager with web interface and autonomous Ralph
 
 ## Additional Commands
 
-`npm run dev` = dev server. Default port: `3000`. Commands not in Quick Reference:
+`npm run dev` = dev server. Default port: `5000` on this `beta/session-detach` branch (`3000` on master). Commands not in Quick Reference:
 
 | Task | Command |
 |------|---------|
@@ -98,6 +98,7 @@ Codeman is a Claude Code session manager with web interface and autonomous Ralph
 - **Dual-CLI prefix discipline** — Codeman supports both Claude Code and OpenCode (`claude-cli-resolver.ts` / `opencode-cli-resolver.ts`); env-var prefix is CLI-specific (`CLAUDE_CODE_*` vs `OPENCODE_*`) and the allowlist in `schemas.ts` enforces this. When adding settings, decide which CLI(s) it applies to and gate the env export accordingly — don't blindly forward both prefixes. See `docs/opencode-integration.md` for the OpenCode resolver design
 - **Zod `.optional()` rejects `null`** — accepts `undefined` only. When the frontend builds a request body with `JSON.stringify`, an explicit `null` field is preserved on the wire and fails validation with `INVALID_INPUT`. Convert `null` → `undefined` before stringifying (e.g. `field: value ?? undefined`), or declare the schema `.nullish()`. Real bugs caused: 0.6.4 (`durationMinutes` for ∞ respawn), and the same shape pattern hit `opusContext1mEnabled` in 0.6.3
 - **`xterm-zerolag-input` is duplicated** — the local-echo overlay lives in BOTH `packages/xterm-zerolag-input/src/` (published to npm as a standalone library for external consumers — see README "Published Packages") AND inline inside `src/web/public/app.js` (runtime copy the web UI actually loads, since the page ships as plain JS without a bundler). Any change to overlay behavior MUST be applied to both, or dev and prod diverge — and a public API break in the package warrants a separate version bump for `xterm-zerolag-input` in the changeset. Always test on mobile after touching it. See `docs/local-echo-overlay-plan.md`.
+- **Instance isolation / multi-instance attach danger** — data dir (`~/.codeman`) and tmux socket (`tmux -L codeman`) are PROCESS-WIDE and shared by every Codeman on the machine, derived from `CODEMAN_INSTANCE` via `src/config/instance.ts` (`getDataDir()`/`dataPath()`/`DEFAULT_TMUX_SOCKET`). ⚠️ A 2nd instance on the SAME socket **discovers and attaches PTYs to the first instance's live sessions** (`tmux -L codeman attach-session …`), resizing/mutating them — `$HOME` isolation is NOT enough (tmux is system-global). To run two instances, give each a distinct `CODEMAN_INSTANCE` (scopes BOTH dir+socket: `~/.codeman-<name>` + `-L codeman-<name>`), or set `CODEMAN_TMUX_SOCKET` + `CODEMAN_DATA_DIR` individually. **This `beta/session-detach` branch defaults to `CODEMAN_INSTANCE=beta` and port 5000** so it coexists with a prod Codeman out of the box. Any new `~/.codeman/...` path MUST go through `dataPath()`, never `join(homedir(), '.codeman', …)`.
 
 **Import conventions**: Utils from `./utils`, types from `./types` (barrel), config from specific `./config/*` files.
 

src/cli.ts

@@ -483,7 +483,7 @@ program
 program
   .command('web')
   .description('Start the web interface')
-  .option('-p, --port <port>', 'Port to listen on', '3000')
+  .option('-p, --port <port>', 'Port to listen on', '5000')
   .option('--https', 'Enable HTTPS with self-signed certificate (only needed for remote access, not localhost)')
   .option('--title-hostname <hostname>', 'Override the hostname shown in the browser title')
   .action(async (options) => {

src/config/instance.ts

@@ -0,0 +1,60 @@
+/**
+ * @fileoverview Per-instance isolation: data directory + tmux socket.
+ *
+ * Codeman keeps all runtime state under `~/.codeman` and runs its tmux sessions
+ * on a dedicated socket (`tmux -L codeman`). Both are PROCESS-WIDE and SHARED by
+ * every Codeman instance on the machine — so a second instance pointed at the
+ * same socket will discover and attach to the first instance's live sessions,
+ * and two instances sharing `~/.codeman/state.json` will clobber each other.
+ *
+ * To let a beta build coexist with a production one, this module derives both
+ * the data dir and the tmux socket from a single "instance" name:
+ *   - default (this branch): `beta` → `~/.codeman-beta` + `tmux -L codeman-beta`
+ *   - `CODEMAN_INSTANCE=`     (empty) → `~/.codeman`     + `tmux -L codeman`   (prod layout)
+ *   - `CODEMAN_INSTANCE=foo`          → `~/.codeman-foo`  + `tmux -L codeman-foo`
+ *
+ * Individual overrides still win: `CODEMAN_DATA_DIR` (absolute data dir) and
+ * `CODEMAN_TMUX_SOCKET` (socket name, validated in tmux-manager).
+ */
+
+import { homedir } from 'node:os';
+import { join } from 'node:path';
+import { mkdirSync } from 'node:fs';
+
+/**
+ * Instance name. Empty string = production layout (`~/.codeman`, `-L codeman`).
+ * Defaults to `beta` on the beta/session-detach branch so it never collides
+ * with a production Codeman. Set `CODEMAN_INSTANCE=` (empty) to opt back into
+ * the production layout.
+ */
+export const CODEMAN_INSTANCE = process.env.CODEMAN_INSTANCE ?? 'beta';
+
+const INSTANCE_SUFFIX = CODEMAN_INSTANCE ? `-${CODEMAN_INSTANCE}` : '';
+
+/** Default tmux socket for this instance. `CODEMAN_TMUX_SOCKET` still overrides. */
+export const DEFAULT_TMUX_SOCKET = `codeman${INSTANCE_SUFFIX}`;
+
+let _ensured = false;
+
+/**
+ * Absolute path to this instance's data directory (created on first use). All
+ * persisted state (`state.json`, `mux-sessions.json`, settings, push keys,
+ * lifecycle log, screenshots, certs, …) lives here.
+ */
+export function getDataDir(): string {
+  const dir = process.env.CODEMAN_DATA_DIR || join(homedir(), `.codeman${INSTANCE_SUFFIX}`);
+  if (!_ensured) {
+    try {
+      mkdirSync(dir, { recursive: true });
+      _ensured = true;
+    } catch {
+      /* best-effort; individual writers also mkdir as needed */
+    }
+  }
+  return dir;
+}
+
+/** Join one or more segments onto this instance's data directory. */
+export function dataPath(...segments: string[]): string {
+  return join(getDataDir(), ...segments);
+}

src/push-store.ts

@@ -8,12 +8,12 @@
 
 import { existsSync, readFileSync, writeFileSync, mkdirSync } from 'node:fs';
 import { join } from 'node:path';
-import { homedir } from 'node:os';
 import webpush from 'web-push';
 import type { VapidKeys, PushSubscriptionRecord } from './types.js';
 import { Debouncer } from './utils/index.js';
+import { getDataDir } from './config/instance.js';
 
-const DATA_DIR = join(homedir(), '.codeman');
+const DATA_DIR = getDataDir();
 const KEYS_FILE = join(DATA_DIR, 'push-keys.json');
 const SUBS_FILE = join(DATA_DIR, 'push-subscriptions.json');
 const SAVE_DEBOUNCE_MS = 500;

src/session-lifecycle-log.ts

@@ -10,9 +10,9 @@
 
 import { appendFile, readFile, writeFile } from 'node:fs/promises';
 import { existsSync, mkdirSync } from 'node:fs';
-import { dirname, join } from 'node:path';
+import { dirname } from 'node:path';
-import { homedir } from 'node:os';
 import type { LifecycleEventType, LifecycleEntry } from './types.js';
+import { dataPath } from './config/instance.js';
 
 const MAX_LINES = 10_000;
 const TRIM_TO = 8_000;
@@ -22,7 +22,7 @@ export class SessionLifecycleLog {
   private writeQueue: Promise<void> = Promise.resolve();
 
   constructor(filePath?: string) {
-    this.filePath = filePath || join(homedir(), '.codeman', 'session-lifecycle.jsonl');
+    this.filePath = filePath || dataPath('session-lifecycle.jsonl');
     const dir = dirname(this.filePath);
     if (!existsSync(dir)) {
       mkdirSync(dir, { recursive: true, mode: 0o700 });

src/state-store.ts

@@ -39,6 +39,7 @@ import {
   TokenUsageEntry,
 } from './types.js';
 import { Debouncer, MAX_SESSION_TOKENS } from './utils/index.js';
+import { dataPath } from './config/instance.js';
 
 /** Debounce delay for batching state writes (ms) */
 const SAVE_DEBOUNCE_MS = 500;
@@ -105,7 +106,7 @@ export class StateStore {
       }
     }
 
-    this.filePath = filePath || join(homedir(), '.codeman', 'state.json');
+    this.filePath = filePath || dataPath('state.json');
     this.ralphStatePath = this.filePath.replace('.json', '-inner.json');
     this.state = this.load();
     this.state.config.stateFilePath = this.filePath;

src/tmux-manager.ts

@@ -28,8 +28,8 @@ import { promisify } from 'node:util';
 const execAsync = promisify(exec);
 import { existsSync, readFileSync, mkdirSync } from 'node:fs';
 import { writeFile, rename } from 'node:fs/promises';
-import { dirname, join } from 'node:path';
+import { dirname } from 'node:path';
-import { homedir } from 'node:os';
+import { dataPath, DEFAULT_TMUX_SOCKET } from './config/instance.js';
 import {
   ProcessStats,
   PersistedRespawnConfig,
@@ -90,7 +90,7 @@ export const CLAUDE_CODE_NOFILE_LIMIT = 2147483646;
 const IS_TEST_MODE = !!process.env.VITEST;
 
 /** Path to persisted mux session metadata */
-const MUX_SESSIONS_FILE = join(homedir(), '.codeman', 'mux-sessions.json');
+const MUX_SESSIONS_FILE = dataPath('mux-sessions.json');
 
 /** Regex to validate tmux session names (only allow safe characters) */
 const SAFE_MUX_NAME_PATTERN = /^codeman-[a-f0-9-]+$/;
@@ -101,8 +101,9 @@ const LEGACY_MUX_NAME_PATTERN = /^claudeman-[a-f0-9-]+$/;
 /** Regex to validate tmux pane targets (e.g., "%0", "%1", "0", "1") */
 const SAFE_PANE_TARGET_PATTERN = /^(%\d+|\d+)$/;
 
-/** Dedicated tmux socket for new Codeman-owned sessions. */
+/** Dedicated tmux socket for new Codeman-owned sessions (instance-scoped:
-const DEFAULT_CODEMAN_TMUX_SOCKET = 'codeman';
+ *  `codeman` for prod, `codeman-beta` on the beta branch). */
+const DEFAULT_CODEMAN_TMUX_SOCKET = DEFAULT_TMUX_SOCKET;
 
 /** Regex to validate tmux socket names passed to `tmux -L`. */
 const SAFE_TMUX_SOCKET_PATTERN = /^[a-zA-Z0-9_.-]+$/;

src/web/public/app.js

@@ -295,6 +295,18 @@ class CodemanApp {
     this.terminal = null;
     this.fitAddon = null;
     this.activeSessionId = null;
+
+    // ── Session detach / undock (beta) ───────────────────────────────────
+    // A "solo window" is a popped-out browser window showing exactly one
+    // session. Detected from the /session/:id URL path (robust even if a cached
+    // service-worker shell loads), with the server-injected global as a fallback.
+    this.soloSessionId = this._detectSoloSessionId();
+    this.isSoloWindow = !!this.soloSessionId;
+    this.detachedSessions = new Set();   // dashboard-side: ids currently popped out
+    this.detachedWindows = new Map();    // dashboard-side: id -> WindowProxy
+    this._detachWatchTimers = new Map(); // dashboard-side: id -> setInterval handle
+    this.windowChannel = null;           // BroadcastChannel for cross-window sync
+
     this._initGeneration = 0;     // dedup concurrent handleInit calls
     this._initFallbackTimer = null; // fallback timer if SSE init doesn't arrive
     this._selectGeneration = 0;   // cancel stale selectSession loads
@@ -544,6 +556,11 @@ class CodemanApp {
   init() {
     // Initialize mobile detection first (adds device classes to body)
     MobileDetection.init();
+    // Detach/undock: open the cross-window sync channel; if this is a solo
+    // (popped-out) window, apply its minimal chrome immediately so the tab
+    // strip never flashes before handleInit selects the target session.
+    this._initWindowChannel();
+    if (this.isSoloWindow) document.body.classList.add('solo-mode');
     // Initialize mobile handlers
     KeyboardHandler.init();
     SwipeHandler.init();
@@ -776,6 +793,180 @@ class CodemanApp {
     } catch { /* non-fatal */ }
   }
 
+  // ══════════════════════════════════════════════════════════════════════
+  // Session detach / undock (beta/session-detach)
+  //
+  // Each detached window is just another normal client of the same session:
+  // the server already fans one PTY's output out to N SSE/WS clients and merges
+  // input from all of them, so a popped-out window is live with no extra server
+  // plumbing. The dashboard tracks which sessions are out, marks their tabs, and
+  // re-docks when the window closes. A BroadcastChannel keeps state in sync
+  // across windows (and survives a dashboard reload via roll-call).
+  // ══════════════════════════════════════════════════════════════════════
+
+  /** Resolve the solo session id from the URL path (preferred) or the
+   *  server-injected global (fallback). Returns null for the normal dashboard. */
+  _detectSoloSessionId() {
+    try {
+      if (typeof window !== 'undefined' && typeof window.__CODEMAN_SOLO__ === 'string' && window.__CODEMAN_SOLO__) {
+        return window.__CODEMAN_SOLO__;
+      }
+      const m = location.pathname.match(/^\/session\/([^/]+)\/?$/);
+      return m ? decodeURIComponent(m[1]) : null;
+    } catch { return null; }
+  }
+
+  /**
+   * Pop a session out into its own browser window. SINGLE, idempotent entry
+   * point: the tab's pop-out icon calls this, and a future gesture layer
+   * ("pinch to drop") calls the exact same method — so keep it cheap and
+   * side-effect-light. Calling it again for an already-open window just raises
+   * that window.
+   * @param {string} id session id
+   */
+  detachSession(id) {
+    if (this.isSoloWindow) return;            // a solo window can't spawn more
+    if (!this.sessions.has(id)) return;
+    // Already out and still open → just raise it (fast path).
+    const existing = this.detachedWindows.get(id);
+    if (existing && !existing.closed) { try { existing.focus(); } catch {} return; }
+    const features = 'width=960,height=680,menubar=no,toolbar=no,location=no,status=no';
+    let win = null;
+    try { win = window.open('/session/' + encodeURIComponent(id), 'codeman-session-' + id, features); } catch {}
+    if (!win) {
+      this.showToast?.('Pop-out blocked — allow popups for this site to detach a session', 'error');
+      return;
+    }
+    this.detachedWindows.set(id, win);
+    this._markDetached(id, true);
+    this._watchDetachedWindow(id, win);
+    this._postWindowMessage({ type: 'detached', id });
+    try { win.focus(); } catch {}
+  }
+
+  /** Re-dock a session: close its window (which re-docks via its unload
+   *  announcement) and clear dashboard state now. */
+  redockSession(id) {
+    const win = this.detachedWindows.get(id);
+    if (win && !win.closed) { try { win.close(); } catch {} }
+    this._postWindowMessage({ type: 'close-request', id });
+    this._redock(id);
+  }
+
+  /** Clear all dashboard-side detached state/timers for a session. */
+  _redock(id) {
+    const t = this._detachWatchTimers.get(id);
+    if (t) { clearInterval(t); this._detachWatchTimers.delete(id); }
+    this.detachedWindows.delete(id);
+    this._markDetached(id, false);
+  }
+
+  /** Toggle the "detached" marker on a tab (immediate DOM update + state set).
+   *  Full re-renders re-apply the class from this.detachedSessions. */
+  _markDetached(id, on) {
+    if (on) this.detachedSessions.add(id); else this.detachedSessions.delete(id);
+    const container = this.$('sessionTabs');
+    const tab = container && container.querySelector(`.session-tab[data-id="${id}"]`);
+    if (tab) tab.classList.toggle('detached', on);
+  }
+
+  /** Poll a window we opened; when it closes, re-dock its tab. This is the
+   *  primary (reliable) close-detection path for windows this tab opened. */
+  _watchDetachedWindow(id, win) {
+    const prev = this._detachWatchTimers.get(id);
+    if (prev) clearInterval(prev);
+    const timer = setInterval(() => {
+      if (!win || win.closed) {
+        clearInterval(timer);
+        this._detachWatchTimers.delete(id);
+        this._redock(id);
+      }
+    }, 800);
+    this._detachWatchTimers.set(id, timer);
+  }
+
+  /** Open the cross-window BroadcastChannel and wire role-specific handlers. */
+  _initWindowChannel() {
+    if (typeof BroadcastChannel === 'undefined') return;
+    try { this.windowChannel = new BroadcastChannel('codeman-windows'); }
+    catch { this.windowChannel = null; return; }
+    this.windowChannel.onmessage = (e) => this._onWindowMessage(e.data);
+    if (this.isSoloWindow) {
+      // Announce presence so the dashboard marks this session's tab detached —
+      // even if this window was opened directly by URL rather than window.open.
+      this._postWindowMessage({ type: 'detached', id: this.soloSessionId });
+      // On close, tell the dashboard to re-dock. pagehide is the reliable signal
+      // on modern browsers; beforeunload is a belt-and-suspenders fallback.
+      const announceClose = () => this._postWindowMessage({ type: 'redocked', id: this.soloSessionId });
+      window.addEventListener('pagehide', announceClose);
+      window.addEventListener('beforeunload', announceClose);
+    } else {
+      // Dashboard: ask any already-open solo windows to re-announce themselves
+      // (covers a dashboard reload while popups remain open).
+      this._postWindowMessage({ type: 'roll-call' });
+    }
+  }
+
+  _postWindowMessage(msg) {
+    try { if (this.windowChannel) this.windowChannel.postMessage(msg); } catch {}
+  }
+
+  _onWindowMessage(msg) {
+    if (!msg || typeof msg !== 'object') return;
+    if (this.isSoloWindow) {
+      // Roll-call has no id (broadcast to all) — answer before the id filter.
+      if (msg.type === 'roll-call') { this._postWindowMessage({ type: 'detached', id: this.soloSessionId }); return; }
+      if (msg.id !== this.soloSessionId) return;
+      if (msg.type === 'close-request') { try { window.close(); } catch {} }
+      else if (msg.type === 'focus-request') { try { window.focus(); } catch {} }
+      return;
+    }
+    // Dashboard side.
+    if (msg.type === 'detached' && msg.id) {
+      this._markDetached(msg.id, true);
+    } else if (msg.type === 'redocked' && msg.id) {
+      this._redock(msg.id);
+    } else if (msg.type === 'detach-request' && msg.id) {
+      // Future gesture hook: another window asks the dashboard to detach a tab.
+      this.detachSession(msg.id);
+    }
+  }
+
+  /** Solo window: select the target session and apply minimal single-session
+   *  chrome. Called from handleInit once the session list has loaded. */
+  _applySoloMode() {
+    document.body.classList.add('solo-mode');
+    const session = this.sessions.get(this.soloSessionId);
+    if (!session) { this._showSoloSessionGone(); return; }
+    // Force re-select (handleInit cleared terminal state above).
+    this.activeSessionId = null;
+    this.selectSession(this.soloSessionId);
+    const name = this.getSessionName(session) || 'Session';
+    const titleEl = document.getElementById('soloSessionTitle');
+    if (titleEl) { titleEl.textContent = name; titleEl.style.display = ''; }
+    const redock = document.getElementById('soloRedockBtn');
+    if (redock) redock.style.display = '';
+    document.title = name + ' — Codeman';
+    if (this.notificationManager) this.notificationManager.originalTitle = document.title;
+    // Neutralize the dashboard-only brand click in a solo window.
+    const logo = document.querySelector('.header-brand .logo');
+    if (logo) logo.onclick = (e) => { e.preventDefault(); };
+  }
+
+  /** Solo window: the target session is gone (never existed, or ended while
+   *  this window was open). Show a friendly terminal state. */
+  _showSoloSessionGone() {
+    document.body.classList.add('solo-mode');
+    if (document.querySelector('.solo-gone-overlay')) return;
+    const el = document.createElement('div');
+    el.className = 'solo-gone-overlay';
+    el.innerHTML = '<h2>Session unavailable</h2>'
+      + '<p>This session has ended or is no longer available.</p>'
+      + '<button class="btn-primary" onclick="window.close()">Close window</button>';
+    document.body.appendChild(el);
+    document.title = 'Session ended — Codeman';
+  }
+
   connectSSE() {
     // Check if browser is offline
     if (!navigator.onLine) {
@@ -929,6 +1120,12 @@ class CodemanApp {
 
   _onSessionDeleted(data) {
     if (this._wsSessionId === data.id) this._disconnectWs();
+    // Solo window whose session just ended → show the "unavailable" state.
+    if (this.isSoloWindow && data.id === this.soloSessionId) {
+      this._showSoloSessionGone();
+    }
+    // Dashboard: a detached session ended → clear its detached state/timers.
+    if (this.detachedSessions.has(data.id)) this._redock(data.id);
     this._cleanupSessionData(data.id);
     if (this.activeSessionId === data.id) {
       this.activeSessionId = null;
@@ -1949,6 +2146,14 @@ class CodemanApp {
     // Reset activeSessionId so selectSession doesn't early-return.
     // Guard: skip if a newer handleInit has already started (race between loadState + SSE init).
     if (gen !== this._initGeneration) return;
+
+    // Solo (detached) window: always show exactly the target session, ignoring
+    // the dashboard's "restore last active" logic.
+    if (this.isSoloWindow) {
+      this._applySoloMode();
+      return;
+    }
+
     const previousActiveId = this.activeSessionId;
     this.activeSessionId = null;
     if (this.sessionOrder.length > 0) {
@@ -2182,19 +2387,21 @@ class CodemanApp {
       const tallTabsEnabled = this._tallTabsEnabled ?? false;
       const showFolder = tallTabsEnabled && session.name && folderName && folderName !== name;
 
-      parts.push(`<div class="session-tab ${isActive ? 'active' : ''}${alertClass}" data-id="${id}" data-color="${color}" onclick="app.selectSession('${escapeHtml(id)}')" oncontextmenu="event.preventDefault(); app.startInlineRename('${escapeHtml(id)}')" tabindex="0" role="tab" aria-selected="${isActive ? 'true' : 'false'}" aria-label="${escapeHtml(name)} session" ${session.workingDir ? `title="${escapeHtml(session.workingDir)}"` : ''}>
+      parts.push(`<div class="session-tab ${isActive ? 'active' : ''}${alertClass}${this.detachedSessions.has(id) ? ' detached' : ''}" data-id="${id}" data-color="${color}" onclick="app.selectSession('${escapeHtml(id)}')" oncontextmenu="event.preventDefault(); app.startInlineRename('${escapeHtml(id)}')" tabindex="0" role="tab" aria-selected="${isActive ? 'true' : 'false'}" aria-label="${escapeHtml(name)} session" ${session.workingDir ? `title="${escapeHtml(session.workingDir)}"` : ''}>
           ${_tabIdx < 9 ? '<span class="tab-number">' + (_tabIdx + 1) + '</span>' : ''}
           <span class="tab-status ${status}" aria-hidden="true"></span>
           <span class="tab-info">
             <span class="tab-name-row">
               ${mode === 'shell' ? '<span class="tab-mode shell" aria-hidden="true">sh</span>' : mode === 'opencode' ? '<span class="tab-mode opencode" aria-hidden="true">oc</span>' : ''}
               <span class="tab-name" data-session-id="${id}">${(() => { const p = parseSessionPrefix(name); return p && p.suffix ? '<span class="tab-prefix">' + escapeHtml(p.prefix) + '</span><span class="tab-suffix">: ' + escapeHtml(p.suffix) + '</span>' : escapeHtml(name); })()}</span>
+              <span class="tab-detached-badge" aria-hidden="true">detached</span>
             </span>
             ${showFolder ? `<span class="tab-folder">\u{1F4C1} ${escapeHtml(folderName)}</span>` : ''}
           </span>
           ${hasRunningTasks ? `<span class="tab-badge" onclick="event.stopPropagation(); app.toggleTaskPanel()" aria-label="${taskStats.running} running tasks">${taskStats.running}</span>` : ''}
           ${subagentBadge}
           <span class="tab-gear" onclick="event.stopPropagation(); app.openSessionOptions('${escapeHtml(id)}')" title="Session options" aria-label="Session options" tabindex="0">&#x2699;</span>
+          <span class="tab-detach" onclick="event.stopPropagation(); app.detachSession('${escapeHtml(id)}')" title="Open in a new window" aria-label="Open session in a new window" tabindex="0">&#x29C9;</span>
           <span class="tab-close" onclick="event.stopPropagation(); app.requestCloseSession('${escapeHtml(id)}')" title="Close session" aria-label="Close session" tabindex="0">&times;</span>
         </div>`);
       _tabIdx++;
@@ -2525,6 +2732,20 @@ class CodemanApp {
   }
 
   async selectSession(sessionId) {
+    // If this session is popped out into its own window, raise that window
+    // instead of showing it inline (focus-on-click for detached tabs).
+    if (!this.isSoloWindow && this.detachedSessions.has(sessionId)) {
+      const win = this.detachedWindows.get(sessionId);
+      if (win && !win.closed) { try { win.focus(); } catch {} return; }
+      if (win && win.closed) {
+        this._redock(sessionId);   // ref we own is dead → re-dock, fall through to inline
+      } else {
+        // No local ref (dashboard was reloaded). Assume the popup is alive and
+        // raise it via the channel; its unload announcement will heal the badge.
+        this._postWindowMessage({ type: 'focus-request', id: sessionId });
+        return;
+      }
+    }
     if (this.activeSessionId === sessionId) return;
     // Focus terminal SYNCHRONOUSLY before any await — iOS Safari only honors
     // programmatic focus() within the user-gesture call stack (e.g. tab click).

src/web/public/index.html

@@ -2,6 +2,10 @@
 <html lang="en">
 <head>
   <meta charset="UTF-8">
+  <!-- Resolve all relative assets against the site root so the same shell can be
+       served at /session/:id (detached single-session window) without 404ing
+       on relative <script>/<link> URLs. Must precede the first resource tag. -->
+  <base href="/">
   <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no, viewport-fit=cover">
   <meta name="description" content="Claude Code session manager with web interface">
   <meta name="theme-color" content="#0a0a0a">
@@ -67,7 +71,11 @@
       <div class="session-tabs" id="sessionTabs" role="tablist" aria-label="Session tabs">
       </div>
 
+      <!-- Detached single-session window title (shown only in solo mode) -->
+      <div class="solo-session-title" id="soloSessionTitle" style="display: none;" aria-live="polite"></div>
+
       <div class="header-right">
+        <button class="btn-icon-header btn-solo-redock" id="soloRedockBtn" style="display: none;" onclick="window.close()" title="Re-dock to dashboard (close window)" aria-label="Re-dock session to dashboard">&#x229E;</button>
         <button class="tunnel-indicator" id="tunnelIndicator" style="display: none;" onclick="app.toggleTunnelPanel()" title="Cloudflare Tunnel" aria-label="Tunnel status">
           <span class="tunnel-dot"></span>
         </button>

src/web/public/styles.css

@@ -905,6 +905,96 @@ body {
   transform: rotate(45deg);
 }
 
+/* ===== Session detach / undock (beta/session-detach) ===================== */
+
+/* Pop-out (detach) icon on each tab — mirrors .tab-gear reveal-on-hover. */
+.session-tab .tab-detach {
+  opacity: 0;
+  width: 0;
+  padding: 0;
+  font-size: 0.95rem;
+  line-height: 1;
+  color: var(--text-muted);
+  cursor: pointer;
+  overflow: hidden;
+  transition: opacity 0.15s, width 0.15s, padding 0.15s;
+}
+.session-tab:hover .tab-detach {
+  opacity: 1;
+  width: auto;
+  padding: 0 0.3rem;
+}
+.session-tab .tab-detach:hover {
+  color: var(--accent-hover);
+  background: rgba(255, 255, 255, 0.1);
+  border-radius: 3px;
+}
+
+/* A tab whose session is popped out into its own window. */
+.session-tab.detached {
+  opacity: 0.72;
+}
+.session-tab.detached .tab-detach {
+  /* Keep the pop-out icon visible while detached as a re-focus affordance. */
+  opacity: 1;
+  width: auto;
+  padding: 0 0.3rem;
+  color: var(--accent-hover);
+}
+.session-tab .tab-detached-badge {
+  display: none;
+  align-items: center;
+  font-size: 0.55rem;
+  font-weight: 700;
+  letter-spacing: 0.04em;
+  text-transform: uppercase;
+  padding: 1px 4px;
+  margin-left: 4px;
+  border-radius: 3px;
+  background: rgba(96, 165, 250, 0.18);
+  color: var(--accent-hover);
+}
+.session-tab.detached .tab-detached-badge {
+  display: inline-flex;
+}
+
+/* ===== Solo (detached single-session) window chrome ===================== */
+body.solo-mode .session-tabs,
+body.solo-mode .header-system-stats,
+body.solo-mode .header-tokens,
+body.solo-mode .btn-notifications,
+body.solo-mode .btn-lifecycle-log {
+  display: none !important;
+}
+.solo-session-title {
+  flex: 1;
+  min-width: 0;
+  font-weight: 600;
+  font-size: 13px;
+  color: var(--text);
+  padding: 0 12px;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+/* "Session unavailable" overlay for a solo window whose session has ended. */
+.solo-gone-overlay {
+  position: fixed;
+  inset: 0;
+  z-index: 5000;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  gap: 14px;
+  background: rgba(9, 9, 11, 0.92);
+  color: var(--text);
+  text-align: center;
+  padding: 24px;
+}
+.solo-gone-overlay h2 { margin: 0; font-size: 18px; }
+.solo-gone-overlay p { margin: 0; color: var(--text-muted); font-size: 13px; }
+
 /* Mode indicator on session tab */
 .session-tab .tab-mode {
   font-size: 0.6rem;

src/web/route-helpers.ts

@@ -16,10 +16,12 @@ import { parseRalphLoopConfig, extractCompletionPhrase } from '../ralph-config.j
 import { SseEvent } from './sse-events.js';
 import type { SessionPort } from './ports/session-port.js';
 import type { EventPort } from './ports/event-port.js';
+import { dataPath } from '../config/instance.js';
 
-// Shared path constants used across route modules
+// Shared path constants used across route modules. CASES_DIR (project folders)
+// stays shared across instances; SETTINGS_PATH is per-instance runtime state.
 export const CASES_DIR = join(homedir(), 'codeman-cases');
-export const SETTINGS_PATH = join(homedir(), '.codeman', 'settings.json');
+export const SETTINGS_PATH = dataPath('settings.json');
 
 /**
  * Validates that a path component doesn't escape the base directory.

src/web/routes/case-routes.ts

@@ -17,8 +17,9 @@ import { writeHooksConfig } from '../../hooks-config.js';
 import { CASES_DIR, SETTINGS_PATH, validatePathWithinBase, parseBody, readJsonConfig } from '../route-helpers.js';
 import { SseEvent } from '../sse-events.js';
 import type { EventPort, ConfigPort } from '../ports/index.js';
+import { dataPath, getDataDir } from '../../config/instance.js';
 
-const LINKED_CASES_FILE = join(homedir(), '.codeman', 'linked-cases.json');
+const LINKED_CASES_FILE = dataPath('linked-cases.json');
 const SAFE_CASE_NAME = /^[a-zA-Z0-9_-]+$/;
 
 /** Read and parse linked-cases.json, returning empty object on missing/invalid file. */
@@ -151,7 +152,7 @@ export function registerCaseRoutes(app: FastifyInstance, ctx: EventPort & Config
     // Save the linked case
     linkedCases[name] = expandedPath;
     try {
-      const codemanDir = join(homedir(), '.codeman');
+      const codemanDir = getDataDir();
       if (!existsSync(codemanDir)) {
         mkdirSync(codemanDir, { recursive: true });
       }
@@ -206,7 +207,7 @@ export function registerCaseRoutes(app: FastifyInstance, ctx: EventPort & Config
     const { order } = parseBody(CaseOrderSchema, req.body, 'Invalid order data');
 
     try {
-      const dir = join(homedir(), '.codeman');
+      const dir = getDataDir();
       if (!existsSync(dir)) {
         mkdirSync(dir, { recursive: true });
       }

src/web/routes/session-routes.ts

@@ -54,9 +54,10 @@ import { MAX_CONCURRENT_SESSIONS } from '../../config/map-limits.js';
 import { RunSummaryTracker } from '../../run-summary.js';
 
 import { MAX_INPUT_LENGTH, MAX_SESSION_NAME_LENGTH } from '../../config/terminal-limits.js';
+import { dataPath } from '../../config/instance.js';
 
 // Path to linked-cases registry (same file used by case-routes resolveCasePath)
-const LINKED_CASES_FILE = join(homedir(), '.codeman', 'linked-cases.json');
+const LINKED_CASES_FILE = dataPath('linked-cases.json');
 
 // Pre-compiled regex for terminal buffer cleaning (avoids per-request compilation)
 // eslint-disable-next-line no-control-regex

src/web/routes/system-routes.ts

@@ -8,9 +8,10 @@ import { FastifyInstance } from 'fastify';
 import { join, dirname } from 'node:path';
 import { existsSync, mkdirSync, readdirSync } from 'node:fs';
 import fs from 'node:fs/promises';
-import { homedir, totalmem, freemem, loadavg, cpus } from 'node:os';
+import { totalmem, freemem, loadavg, cpus } from 'node:os';
 import { execSync } from 'node:child_process';
 import { randomBytes } from 'node:crypto';
+import { dataPath } from '../../config/instance.js';
 import { ApiErrorCode, createErrorResponse, getErrorMessage, type NiceConfig } from '../../types.js';
 import {
   ConfigUpdateSchema,
@@ -41,7 +42,7 @@ import { AUTH_SESSION_TTL_MS } from '../../config/auth-config.js';
 // Maximum screenshot upload size (10MB)
 const MAX_SCREENSHOT_SIZE = 10 * 1024 * 1024;
 // Screenshots directory
-const SCREENSHOTS_DIR = join(homedir(), '.codeman', 'screenshots');
+const SCREENSHOTS_DIR = dataPath('screenshots');
 
 /** Cached CPU count — doesn't change at runtime */
 const CPU_COUNT = cpus().length;
@@ -96,8 +97,8 @@ export function registerSystemRoutes(
   app: FastifyInstance,
   ctx: SessionPort & EventPort & ConfigPort & InfraPort & AuthPort
 ): void {
-  const windowStatesPath = join(homedir(), '.codeman', 'subagent-window-states.json');
+  const windowStatesPath = dataPath('subagent-window-states.json');
-  const parentMapPath = join(homedir(), '.codeman', 'subagent-parents.json');
+  const parentMapPath = dataPath('subagent-parents.json');
 
   // ═══════════════════════════════════════════════════════════════
   // System Status & Health

src/web/server.ts

@@ -39,7 +39,8 @@ import { fileURLToPath } from 'node:url';
 import { existsSync, mkdirSync, readFileSync, chmodSync, rmSync } from 'node:fs';
 import fs from 'node:fs/promises';
 import { execSync } from 'node:child_process';
-import { homedir, hostname as getHostname } from 'node:os';
+import { hostname as getHostname } from 'node:os';
+import { dataPath } from '../config/instance.js';
 import { EventEmitter } from 'node:events';
 import { Session, type BackgroundTask } from '../session.js';
 import type { ClaudeMode, SessionState } from '../types.js';
@@ -146,7 +147,7 @@ import {
  * Certs are stored in ~/.codeman/certs/ and reused across restarts.
  */
 function getOrCreateSelfSignedCert(): { key: string; cert: string } {
-  const certsDir = join(homedir(), '.codeman', 'certs');
+  const certsDir = dataPath('certs');
   const keyPath = join(certsDir, 'server.key');
   const certPath = join(certsDir, 'server.crt');
 
@@ -562,6 +563,17 @@ export class WebServer extends EventEmitter {
     this.app.get('/index.html', async (_req, reply) => {
       return reply.header('Cache-Control', 'no-cache').type('text/html; charset=utf-8').send(this.renderIndexHtml());
     });
+    // Detached single-session window (undock). Serves the same SPA shell but
+    // flags the client into "solo mode" for one session. Auth applies normally
+    // (the popup carries the dashboard's cookie on navigation). We serve 200
+    // even for an unknown id — the client renders a friendly "session
+    // unavailable" state, which also covers a session that ends while its
+    // detached window is still open. Registered before the static plugin so the
+    // explicit route wins over the '/' static prefix.
+    this.app.get('/session/:id', async (req, reply) => {
+      const { id } = req.params as { id: string };
+      return reply.header('Cache-Control', 'no-cache').type('text/html; charset=utf-8').send(this.renderIndexHtml(id));
+    });
     // Service worker must never be cached — browsers check for SW updates on navigation
     this.app.get('/sw.js', async (_req, reply) => {
       return reply
@@ -980,11 +992,22 @@ export class WebServer extends EventEmitter {
     this.broadcast(SseEvent.SessionDeleted, { id: sessionId });
   }
 
-  private renderIndexHtml(): string {
+  private renderIndexHtml(soloSessionId?: string): string {
-    return this.indexHtmlTemplate.replace(
+    let html = this.indexHtmlTemplate.replace(
       '<title>Codeman</title>',
       `<title>${escapeHtmlText(this.windowTitle)}</title>`
     );
+    // Detached single-session ("solo") window: inject the target session id so
+    // the client can enter solo mode even if a (network-first) service worker
+    // later serves a cached shell. The client primarily detects solo mode from
+    // the /session/:id URL path; this global is a belt-and-suspenders fallback.
+    // The id is gated to JSON + <-escaped so it can't break out of the inline
+    // <script> (ids are UUIDs in practice, but defense-in-depth is cheap).
+    if (soloSessionId) {
+      const safeId = JSON.stringify(soloSessionId).replace(/</g, '\\u003c');
+      html = html.replace('</head>', `<script>window.__CODEMAN_SOLO__=${safeId};</script>\n</head>`);
+    }
+    return html;
   }
 
   private async setupSessionListeners(session: Session): Promise<void> {
@@ -1088,7 +1111,7 @@ export class WebServer extends EventEmitter {
 
   // Helper to get custom CLAUDE.md template path from settings
   private async getDefaultClaudeMdPath(): Promise<string | undefined> {
-    const settingsPath = join(homedir(), '.codeman', 'settings.json');
+    const settingsPath = dataPath('settings.json');
 
     try {
       const content = await fs.readFile(settingsPath, 'utf-8');
@@ -1112,7 +1135,7 @@ export class WebServer extends EventEmitter {
     if (this._settingsCache && now - this._settingsCache.ts < 2000) {
       return this._settingsCache.data;
     }
-    const settingsPath = join(homedir(), '.codeman', 'settings.json');
+    const settingsPath = dataPath('settings.json');
     try {
       const content = await fs.readFile(settingsPath, 'utf-8');
       const data = JSON.parse(content) as Record<string, unknown>;
@@ -1619,7 +1642,7 @@ export class WebServer extends EventEmitter {
     // Tunnel only starts when user clicks the toggle in the UI — never on boot.
     // Reset persisted tunnelEnabled so the UI toggle reflects actual state.
     if (await this.isTunnelEnabled()) {
-      const settingsPath = join(homedir(), '.codeman', 'settings.json');
+      const settingsPath = dataPath('settings.json');
       try {
         const content = await fs.readFile(settingsPath, 'utf-8');
         const settings = JSON.parse(content);
@@ -1640,7 +1663,7 @@ export class WebServer extends EventEmitter {
    * Check if subagent tracking is enabled in settings (default: true)
    */
   private async isSubagentTrackingEnabled(): Promise<boolean> {
-    const settingsPath = join(homedir(), '.codeman', 'settings.json');
+    const settingsPath = dataPath('settings.json');
     try {
       const content = await fs.readFile(settingsPath, 'utf-8');
       const settings = JSON.parse(content);
@@ -1658,7 +1681,7 @@ export class WebServer extends EventEmitter {
    * Check if image watcher is enabled in settings (default: false)
    */
   private async isImageWatcherEnabled(): Promise<boolean> {
-    const settingsPath = join(homedir(), '.codeman', 'settings.json');
+    const settingsPath = dataPath('settings.json');
     try {
       const content = await fs.readFile(settingsPath, 'utf-8');
       const settings = JSON.parse(content);
@@ -1676,7 +1699,7 @@ export class WebServer extends EventEmitter {
    * Check if Cloudflare tunnel is enabled in settings (default: false)
    */
   private async isTunnelEnabled(): Promise<boolean> {
-    const settingsPath = join(homedir(), '.codeman', 'settings.json');
+    const settingsPath = dataPath('settings.json');
     try {
       const content = await fs.readFile(settingsPath, 'utf-8');
       const settings = JSON.parse(content);