diff --git a/src/server/board/chrome.ts b/src/server/board/chrome.ts
index af264ba..74ae374 100644
--- a/src/server/board/chrome.ts
+++ b/src/server/board/chrome.ts
@@ -1,30 +1,13 @@
-import { escapeHtml } from '../ui-shared.js';
-
-const LOGO = '<img src="/logo.svg" alt="" width="24" height="24" class="b2-logo-img">';
+import { appHeader } from '../ui-shared.js';
 
 /**
- * Fixed app header for board v2. The project cell is visual only — the real
- * project switcher dropdown arrives with the multi-project v3 spec.
- * The SSE status span keeps the v1 ids (`sseStatus`, `sseLabel`) so the ported
- * connection-status JS keeps working unchanged.
+ * Fixed app header for board v2 — the shared v2 header (ui-shared.appHeader)
+ * with the board marked active. The project cell is visual only (dropdown = v3);
+ * SSE ids (`sseStatus`, `sseLabel`) match the ported connection-status JS.
+ * Styling comes from ui-shared's appHeaderOnlyCss(), which boardV2Css() includes.
  */
 export function headerHtml(projectName: string): string {
-  const name = escapeHtml(projectName);
-  return `
-<header class="b2-hdr">
-  <span class="b2-brand">${LOGO}<b>agenthub</b></span>
-  <span class="b2-proj" title="Projektwechsel kommt mit v3">/ <span id="projectName">${name}</span>&nbsp;<span class="b2-chev">▾</span></span>
-  <nav class="b2-nav" aria-label="Primary">
-    <b aria-current="page">Board</b><a href="/team">Team</a><a href="/activity">Activity</a><a href="/decisions">Decisions</a>
-  </nav>
-  <span class="b2-hdr-right">
-    <button type="button" class="b2-btn" id="newTaskBtn" aria-haspopup="dialog" aria-expanded="false">+ New task</button>
-    <span class="sse-status stale" id="sseStatus">
-      <span class="b2-live-dot" aria-hidden="true"></span>
-      <span id="sseLabel">connecting</span>
-    </span>
-  </span>
-</header>`;
+  return appHeader(projectName, 'board');
 }
 
 /** Fullscreen splash overlay, shown until first data render (hard cap 1.5s). */
diff --git a/src/server/board/styles.ts b/src/server/board/styles.ts
index 3ee834c..40c5f55 100644
--- a/src/server/board/styles.ts
+++ b/src/server/board/styles.ts
@@ -1,15 +1,19 @@
 /**
  * Board v2 design system: glass dashboard on a deep gradient.
  * Everything is emitted by boardV2Css() and inlined into the page <style>.
+ * The header CSS is shared with all pages and comes from ui-shared
+ * (appHeaderOnlyCss) — this file only adds the board-specific components.
  *
- * Naming: `b2-` prefix for new v2 components (header, kpis, sidebar tabs,
+ * Naming: `b2-` prefix for new v2 components (kpis, sidebar tabs,
  * feed, splash, progress ring). Interaction-critical components ported from
  * v1 (cards, columns, console, modals, toasts, budget internals) keep their
  * v1 class names so the ported client JS keeps working unchanged — they read
  * the same CSS variables, which are redefined here with the v2 glass values.
  */
+import { appHeaderOnlyCss } from '../ui-shared.js';
+
 export function boardV2Css(): string {
-  return `
+  return appHeaderOnlyCss() + `
     :root {
       /* v2 tokens */
       --b2-bg: #090c18;
@@ -65,60 +69,9 @@ export function boardV2Css(): string {
     /* ── Keyframes (v2) ───────────────────────────────────────────────── */
     @keyframes b2-rise { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: none; } }
     @keyframes b2-fill { from { width: 0; } }
-    @keyframes b2-ping { 0% { box-shadow: 0 0 0 0 rgba(52,211,179,.55); } 70% { box-shadow: 0 0 0 7px rgba(52,211,179,0); } 100% { box-shadow: 0 0 0 0 rgba(52,211,179,0); } }
     @keyframes b2-blink { 50% { opacity: .3; } }
     @keyframes b2-draw { to { stroke-dashoffset: 0; } }
 
-    /* ── Header ───────────────────────────────────────────────────────── */
-    .b2-hdr {
-      position: fixed; top: 0; left: 0; right: 0; z-index: 40;
-      display: flex; align-items: center; gap: 14px;
-      min-height: 66px; padding: 10px 22px;
-      border-bottom: 1px solid rgba(255,255,255,.06);
-      background: rgba(9, 12, 24, .82);
-      backdrop-filter: blur(12px);
-    }
-    .b2-brand { display: flex; align-items: center; gap: 10px; font-size: 16px; }
-    .b2-brand b { font-weight: 700; letter-spacing: .01em; }
-    .b2-logo-img { display: block; }
-    .b2-proj {
-      display: flex; align-items: center; gap: 5px;
-      color: var(--b2-muted); font-size: 13px; font-family: var(--mono);
-      padding: 4px 10px; border-radius: 8px; border: 1px solid transparent;
-      max-width: 34vw; white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
-    }
-    .b2-proj:hover { background: rgba(255,255,255,.05); border-color: var(--b2-border); color: #c6d0e8; }
-    .b2-chev { font-size: 9px; opacity: .7; }
-    .b2-nav { display: flex; align-items: center; gap: 2px; margin-left: 8px;
-      border: 1px solid var(--b2-border); background: var(--b2-surface);
-      padding: 3px; border-radius: 9px; }
-    .b2-nav b, .b2-nav a {
-      min-height: 32px; display: inline-flex; align-items: center;
-      padding: 0 13px; border-radius: 7px; font-size: 13px; font-weight: 500;
-      color: var(--b2-muted); transition: color 160ms ease, background 160ms ease;
-    }
-    .b2-nav b { color: var(--b2-text); background: rgba(255,255,255,.08); font-weight: 600; }
-    .b2-nav a:hover { color: var(--b2-text); background: rgba(255,255,255,.05); }
-    .b2-hdr-right { margin-left: auto; display: flex; align-items: center; gap: 14px; }
-    .b2-btn {
-      display: inline-flex; align-items: center; gap: 7px;
-      min-height: 36px; padding: 0 16px; border: 0; border-radius: 9px;
-      background: linear-gradient(135deg, #6366f1, #8b5cf6);
-      color: #fff; font: 600 13px/1 var(--sans);
-      box-shadow: 0 4px 18px rgba(99,102,241,.28);
-      transition: transform 120ms ease, box-shadow 160ms ease, filter 160ms ease;
-    }
-    .b2-btn:hover { filter: brightness(1.1); box-shadow: 0 6px 22px rgba(99,102,241,.38); }
-    .b2-btn:active { transform: translateY(1px); }
-    .b2-live-dot {
-      width: 9px; height: 9px; border-radius: 50%;
-      background: var(--b2-green); animation: b2-ping 2s infinite;
-    }
-    /* v1 JS toggles stale/down states on the wrapper — keep hooks compatible */
-    .sse-status { display: inline-flex; align-items: center; gap: 7px; color: var(--b2-muted); font: 12px/1 var(--mono); }
-    .sse-status.stale .b2-live-dot { background: var(--b2-amber); animation: none; }
-    .sse-status.down .b2-live-dot { background: var(--danger); animation: none; }
-
     /* ── Layout ───────────────────────────────────────────────────────── */
     .b2-body {
       display: grid; grid-template-columns: minmax(0, 1fr) minmax(290px, 330px);
@@ -458,17 +411,14 @@ export function boardV2Css(): string {
     }
     @media (max-width: 860px) {
       body { padding-left: 14px; padding-right: 14px; }
-      .b2-hdr { padding-left: 14px; padding-right: 14px; }
+      .app-header { padding-left: 14px; padding-right: 14px; }
       .b2-kpis { grid-template-columns: repeat(2, minmax(0, 1fr)); }
       .board { grid-template-columns: repeat(2, 1fr); }
-      .b2-proj { max-width: 46vw; }
+      .app-header .b2-proj { max-width: 46vw; }
     }
     @media (max-width: 560px) {
-      .b2-hdr { align-items: flex-start; flex-wrap: wrap; }
       .b2-kpis { grid-template-columns: 1fr; }
       .board { grid-template-columns: 1fr; }
-      .b2-nav { flex: 1; }
-      .b2-nav b, .b2-nav a { flex: 1; justify-content: center; }
       .detail-activity-row { grid-template-columns: 1fr; gap: 3px; }
       .agent-bar-row { grid-template-columns: 1fr; gap: 6px; }
     }
diff --git a/src/server/ui-shared.ts b/src/server/ui-shared.ts
index 563c0c7..bcbaf2f 100644
--- a/src/server/ui-shared.ts
+++ b/src/server/ui-shared.ts
@@ -293,41 +293,72 @@ export function pageHeader(projectName: string, current: 'board' | 'team' | 'act
 
 export type HeaderPage = 'board' | 'team' | 'activity' | 'messages' | 'decisions' | 'archive' | 'task';
 
-/** CSS for the shared header + new-task modal + toasts. Include once per page. */
-export function appHeaderCss(): string {
+/** CSS for ONLY the shared header (board v2 reuses this inside boardV2Css). */
+export function appHeaderOnlyCss(): string {
   return `
+    /* v2 header tokens (self-contained — host pages define different palettes) */
+    :root {
+      --b2-border: rgba(255,255,255,.09);
+      --b2-surface: rgba(255,255,255,.045);
+      --b2-text: #eef1f8;
+      --b2-muted: #8fa0c6;
+      --b2-green: #34d399;
+      --b2-amber: #fbbf24;
+    }
+    @keyframes b2-ping { 0% { box-shadow: 0 0 0 0 rgba(52,211,179,.55); } 70% { box-shadow: 0 0 0 7px rgba(52,211,179,0); } 100% { box-shadow: 0 0 0 0 rgba(52,211,179,0); } }
     .app-header {
       position: fixed; top: 0; left: 0; right: 0; z-index: 40;
-      display: flex; align-items: center; gap: 16px; min-height: 64px;
-      margin: 0; padding: 10px 20px;
-      border-bottom: 1px solid var(--border);
-      background: rgba(15, 23, 42, .96); backdrop-filter: blur(10px);
+      display: flex; align-items: center; gap: 14px; min-height: 66px;
+      margin: 0; padding: 10px 22px;
+      border-bottom: 1px solid rgba(255,255,255,.06);
+      background: rgba(9, 12, 24, .82); backdrop-filter: blur(12px);
     }
-    .app-header .brand { display: flex; align-items: center; gap: 10px; min-width: 0; }
-    .app-header .mark { width: 34px; height: 34px; flex: 0 0 auto; border: 1px solid rgba(88,166,255,.38); border-radius: 8px; display: grid; place-items: center; background: var(--raised); }
-    .app-header .mark svg { width: 22px; height: 22px; }
-    .brand-copy { min-width: 0; display: flex; align-items: baseline; gap: 10px; flex-wrap: wrap; }
-    .brand-title { font-weight: 700; font-size: 17px; }
-    .project-name { color: var(--muted); font-size: 12px; font-family: var(--font-mono); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; max-width: 42vw; }
-    .header-spacer { flex: 1; }
-    .app-header .nav { display: flex; align-items: center; gap: 4px; border: 1px solid var(--border); background: var(--surface); padding: 3px; border-radius: 8px; }
-    .app-header .nav-link { min-height: 34px; display: inline-flex; align-items: center; padding: 0 12px; border-radius: 6px; color: var(--muted); font-size: 13px; text-decoration: none; transition: color 180ms ease, background 180ms ease; }
-    .app-header .nav-link:hover, .app-header .nav-link.active { color: var(--text); background: var(--raised); }
-    .new-task-btn { display: inline-flex; align-items: center; gap: 7px; min-height: 34px; padding: 0 14px; border-radius: 8px; border: 1px solid rgba(88,166,255,.45); background: linear-gradient(180deg, rgba(88,166,255,.20), rgba(88,166,255,.10)); color: var(--text); font: 600 13px/1 var(--font-sans); cursor: pointer; transition: background 160ms ease, transform 120ms ease, box-shadow 160ms ease; }
-    .new-task-btn:hover { background: rgba(88,166,255,.28); box-shadow: 0 4px 16px rgba(88,166,255,.18); }
-    .new-task-btn:active { transform: translateY(1px); }
-    .new-task-btn .plus { font-size: 16px; line-height: 1; margin-top: -1px; }
-    .sse-status { display: inline-flex; align-items: center; gap: 7px; min-width: 116px; min-height: 34px; color: var(--muted); font: 12px/1 var(--font-mono); white-space: nowrap; }
-    .conn-dot { width: 9px; height: 9px; border-radius: 50%; background: var(--green); box-shadow: 0 0 0 3px rgba(34,197,94,.16); }
-    .sse-status.stale .conn-dot { background: var(--status-review); box-shadow: 0 0 0 3px rgba(210,153,34,.14); }
-    .sse-status.down .conn-dot { background: #F85149; box-shadow: 0 0 0 3px rgba(248,81,73,.14); }
+    .app-header .b2-brand { display: flex; align-items: center; gap: 10px; font-size: 16px; }
+    .app-header .b2-brand b { font-weight: 700; letter-spacing: .01em; }
+    .b2-logo-img { display: block; }
+    .app-header .b2-proj {
+      display: flex; align-items: center; gap: 5px;
+      color: var(--b2-muted); font-size: 13px; font-family: var(--font-mono, ui-monospace, monospace);
+      padding: 4px 10px; border-radius: 8px; border: 1px solid transparent;
+      max-width: 34vw; white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
+    }
+    .app-header .b2-proj:hover { background: rgba(255,255,255,.05); border-color: var(--b2-border); color: #c6d0e8; }
+    .b2-chev { font-size: 9px; opacity: .7; }
+    .app-header .b2-nav { display: flex; align-items: center; gap: 2px; margin-left: 8px;
+      border: 1px solid var(--b2-border); background: var(--b2-surface); padding: 3px; border-radius: 9px; }
+    .app-header .b2-nav a {
+      min-height: 32px; display: inline-flex; align-items: center;
+      padding: 0 13px; border-radius: 7px; font-size: 13px; font-weight: 500;
+      color: var(--b2-muted); text-decoration: none; transition: color 160ms ease, background 160ms ease;
+    }
+    .app-header .b2-nav a:hover { color: var(--b2-text); background: rgba(255,255,255,.05); }
+    .app-header .b2-nav a.active { color: var(--b2-text); background: rgba(255,255,255,.08); font-weight: 600; }
+    .b2-hdr-right { margin-left: auto; display: flex; align-items: center; gap: 14px; }
+    .b2-btn {
+      display: inline-flex; align-items: center; gap: 7px;
+      min-height: 36px; padding: 0 16px; border: 0; border-radius: 9px;
+      background: linear-gradient(135deg, #6366f1, #8b5cf6);
+      color: #fff; font: 600 13px/1 var(--font-sans, system-ui, sans-serif); cursor: pointer;
+      box-shadow: 0 4px 18px rgba(99,102,241,.28);
+      transition: transform 120ms ease, box-shadow 160ms ease, filter 160ms ease;
+    }
+    .b2-btn:hover { filter: brightness(1.1); box-shadow: 0 6px 22px rgba(99,102,241,.38); }
+    .b2-btn:active { transform: translateY(1px); }
+    .sse-status { display: inline-flex; align-items: center; gap: 7px; min-width: 116px; min-height: 34px; color: var(--b2-muted); font: 12px/1 var(--font-mono, ui-monospace, monospace); white-space: nowrap; }
+    .b2-live-dot { width: 9px; height: 9px; border-radius: 50%; background: var(--b2-green); animation: b2-ping 2s infinite; }
+    .sse-status.stale .b2-live-dot { background: var(--b2-amber); animation: none; }
+    .sse-status.down .b2-live-dot { background: #F85149; animation: none; }
     @media (max-width: 680px) {
       .app-header { flex-wrap: wrap; gap: 10px 12px; }
-      .header-spacer { display: none; }
-      .app-header .nav { order: 3; width: 100%; }
-      .app-header .nav-link { flex: 1; justify-content: center; }
-    }
+      .b2-hdr-right { margin-left: auto; }
+      .app-header .b2-nav { order: 3; width: 100%; }
+      .app-header .b2-nav a { flex: 1; justify-content: center; }
+    }`;
+}
 
+/** CSS for the shared header + new-task modal + toasts. Include once per page. */
+export function appHeaderCss(): string {
+  return appHeaderOnlyCss() + `
     /* ── New-task modal ─────────────────────────────────────────────────── */
     .modal-backdrop { position: fixed; inset: 0; z-index: 60; display: flex; align-items: flex-start; justify-content: center; padding: 12vh 16px 16px; background: rgba(2,6,18,.62); backdrop-filter: blur(3px); animation: modalFade 140ms ease; }
     .modal-backdrop[hidden] { display: none; }
@@ -366,34 +397,27 @@ export function appHeaderCss(): string {
     @keyframes toastOut { to { opacity: 0; transform: translateY(6px); } }`;
 }
 
-/** The shared header markup: brand, nav, New-task button, live status. */
+/** The shared header markup (v2): logo, project cell, nav, New-task, live status. */
 export function appHeader(projectName: string, current: HeaderPage): string {
-  const mark = `<span class="mark" aria-hidden="true"><svg viewBox="0 0 24 24" fill="none"><path d="M5 7.5h8.5a5.5 5.5 0 0 1 0 11H5v-11Z" stroke="#58A6FF" stroke-width="1.8"/><path d="M8.5 5.5h7a4 4 0 0 1 0 8h-7v-8Z" stroke="#22C55E" stroke-width="1.8"/></svg></span>`;
   const link = (label: string, path: string, key: HeaderPage) =>
-    `<a class="nav-link${current === key ? ' active' : ''}" href="${path}">${label}</a>`;
+    `<a class="${current === key ? 'active' : ''}" href="${path}"${current === key ? ' aria-current="page"' : ''}>${label}</a>`;
   return `
   <header class="app-header">
-    <div class="brand">
-      ${mark}
-      <div class="brand-copy">
-        <span class="brand-title">AgentHub</span>
-        <span class="project-name" id="projectName">${escapeHtml(projectName)}</span>
-      </div>
-    </div>
-    <span class="header-spacer"></span>
-    <nav class="nav" aria-label="Primary">
+    <span class="b2-brand"><img src="/logo.svg" alt="" width="24" height="24" class="b2-logo-img"><b>agenthub</b></span>
+    <span class="b2-proj" title="Projektwechsel kommt mit v3">/ <span id="projectName">${escapeHtml(projectName)}</span>&nbsp;<span class="b2-chev">▾</span></span>
+    <nav class="b2-nav" aria-label="Primary">
       ${link('Board', '/board', 'board')}
       ${link('Team', '/team', 'team')}
       ${link('Activity', '/activity', 'activity')}
       ${link('Messages', '/messages', 'messages')}
       ${link('Decisions', '/decisions', 'decisions')}
     </nav>
-    <button class="new-task-btn" id="newTaskBtn" type="button" aria-haspopup="dialog" aria-expanded="false">
-      <span class="plus" aria-hidden="true">+</span> New task
-    </button>
-    <span class="sse-status stale" id="sseStatus">
-      <span class="conn-dot" aria-hidden="true"></span>
-      <span id="sseLabel">connecting</span>
+    <span class="b2-hdr-right">
+      <button class="b2-btn" id="newTaskBtn" type="button" aria-haspopup="dialog" aria-expanded="false">+ New task</button>
+      <span class="sse-status stale" id="sseStatus">
+        <span class="b2-live-dot" aria-hidden="true"></span>
+        <span id="sseLabel">connecting</span>
+      </span>
     </span>
   </header>`;
 }
diff --git a/tests/boardV2.test.ts b/tests/boardV2.test.ts
index 04b90d6..ad521d7 100644
--- a/tests/boardV2.test.ts
+++ b/tests/boardV2.test.ts
@@ -10,7 +10,7 @@ describe('renderBoardHtml (v2)', () => {
     expect(html).toContain('id="b2-splash"');
   });
   it('contains header, kpis, columns and sidebar mount points', () => {
-    for (const s of ['b2-hdr', 'demo-project', 'id="kpiOpen"', 'id="b2Budget"', 'id="b2Feed"']) {
+    for (const s of ['app-header', 'demo-project', 'id="kpiOpen"', 'id="b2Budget"', 'id="b2Feed"']) {
       expect(html).toContain(s);
     }
   });
diff --git a/tests/ui-shared.test.ts b/tests/ui-shared.test.ts
index 5a284cf..22b63ca 100644
--- a/tests/ui-shared.test.ts
+++ b/tests/ui-shared.test.ts
@@ -1,5 +1,5 @@
 import { describe, it, expect } from 'vitest';
-import { agentAvatar, designTokensCss, escapeHtml, liveTimerJs, statusPill } from '../src/server/ui-shared.js';
+import { agentAvatar, designTokensCss, escapeHtml, liveTimerJs, statusPill, appHeader, appHeaderCss, appHeaderOnlyCss } from '../src/server/ui-shared.js';
 
 describe('ui-shared helpers', () => {
   it('designTokensCss returns the dark palette variables', () => {
@@ -48,3 +48,32 @@ describe('ui-shared helpers', () => {
     expect(js).toContain('claimed');
   });
 });
+
+describe('appHeader (v2 shared header)', () => {
+  it('renders logo, project cell, nav links and status mounts', () => {
+    const h = appHeader('demo', 'team');
+    expect(h).toContain('/logo.svg');
+    expect(h).toContain('id="projectName"');
+    expect(h).toContain('b2-proj');
+    expect(h).toContain('id="newTaskBtn"');
+    expect(h).toContain('id="sseStatus"');
+    for (const path of ['/board', '/team', '/activity', '/messages', '/decisions']) {
+      expect(h).toContain(`href="${path}"`);
+    }
+  });
+  it('marks the current page active with aria-current', () => {
+    const team = appHeader('demo', 'team');
+    expect(team).toContain('active" href="/team" aria-current="page"');
+    const board = appHeader('demo', 'board');
+    expect(board).toContain('active" href="/board" aria-current="page"');
+    expect(board).not.toContain('active" href="/team"');
+  });
+  it('escapes the project name', () => {
+    expect(appHeader('<b>x</b>', 'board')).not.toContain('<b>x</b>');
+  });
+  it('appHeaderOnlyCss is a prefix of appHeaderCss', () => {
+    expect(appHeaderCss().startsWith(appHeaderOnlyCss())).toBe(true);
+    expect(appHeaderOnlyCss()).toContain('.app-header');
+    expect(appHeaderCss()).toContain('.modal-backdrop');
+  });
+});