diff --git a/apps/desktop/src/components/assistant-ui/tool-fallback-model.test.ts b/apps/desktop/src/components/assistant-ui/tool-fallback-model.test.ts
index 142b912e4dad..6c864608c727 100644
--- a/apps/desktop/src/components/assistant-ui/tool-fallback-model.test.ts
+++ b/apps/desktop/src/components/assistant-ui/tool-fallback-model.test.ts
@@ -77,6 +77,36 @@ describe('buildToolView terminal exit-code status', () => {
   })
 })
 
+describe('buildToolView browser_navigate title', () => {
+  it('shows failed title when navigate returns success=false', () => {
+    const view = buildToolView(
+      part({
+        toolName: 'browser_navigate',
+        args: { url: 'https://hermes-agent.nousresearch.com/docs' },
+        result: { success: false, error: 'Command timed out after 60 seconds' }
+      }),
+      ''
+    )
+
+    expect(view.status).toBe('error')
+    expect(view.title).toBe('Failed to open hermes-agent.nousresearch.com')
+  })
+
+  it('shows opened title on success', () => {
+    const view = buildToolView(
+      part({
+        toolName: 'browser_navigate',
+        args: { url: 'https://hermes-agent.nousresearch.com/docs' },
+        result: { success: true, url: 'https://hermes-agent.nousresearch.com/docs', title: 'Docs' }
+      }),
+      ''
+    )
+
+    expect(view.status).toBe('success')
+    expect(view.title).toBe('Opened hermes-agent.nousresearch.com')
+  })
+})
+
 describe('buildToolView file edit diffs', () => {
   const patchDiff = '--- a/src/demo.ts\n+++ b/src/demo.ts\n@@ -1 +1 @@\n-old\n+new'
 
diff --git a/apps/desktop/src/components/assistant-ui/tool-fallback-model.ts b/apps/desktop/src/components/assistant-ui/tool-fallback-model.ts
index 0cc22b62e48a..b99527f05c40 100644
--- a/apps/desktop/src/components/assistant-ui/tool-fallback-model.ts
+++ b/apps/desktop/src/components/assistant-ui/tool-fallback-model.ts
@@ -1534,11 +1534,32 @@ function dynamicTitle(
 
   if (part.toolName === 'browser_navigate') {
     const url = findFirstUrl(args, result)
+
+    if (!url) {
+      return fallback
+    }
+
+    const failed =
+      part.isError ||
+      result.success === false ||
+      result.ok === false ||
+      Boolean(firstStringField(result, ['error']))
+
+    if (failed) {
+      const failAction = translateNow('assistant.tool.actions.failedToOpen')
+
+      return titledAction(
+        failAction,
+        translateNow('assistant.tool.titleTemplates.actionTarget', failAction, hostnameOf(url))
+      )
+    }
+
     const action = verb(translateNow('assistant.tool.actions.opening'), translateNow('assistant.tool.actions.opened'))
 
-    return url
-      ? titledAction(action, translateNow('assistant.tool.titleTemplates.actionTarget', action, hostnameOf(url)))
-      : fallback
+    return titledAction(
+      action,
+      translateNow('assistant.tool.titleTemplates.actionTarget', action, hostnameOf(url))
+    )
   }
 
   if (part.toolName === 'web_search') {
diff --git a/apps/desktop/src/i18n/en.ts b/apps/desktop/src/i18n/en.ts
index f7841f760a35..52501ee97395 100644
--- a/apps/desktop/src/i18n/en.ts
+++ b/apps/desktop/src/i18n/en.ts
@@ -2066,6 +2066,7 @@ export const en: Translations = {
         reading: 'Reading',
         opened: 'Opened',
         opening: 'Opening',
+        failedToOpen: 'Failed to open',
         searched: 'Searched',
         searching: 'Searching',
         ran: 'Ran',
diff --git a/apps/desktop/src/i18n/ja.ts b/apps/desktop/src/i18n/ja.ts
index 741712a6d3c5..bdf4e8829299 100644
--- a/apps/desktop/src/i18n/ja.ts
+++ b/apps/desktop/src/i18n/ja.ts
@@ -2189,6 +2189,7 @@ export const ja = defineLocale({
         reading: '読み取り中',
         opened: 'オープン済み',
         opening: 'オープン中',
+        failedToOpen: 'オープン失敗',
         searched: '検索完了',
         searching: '検索中',
         ran: '実行完了',
diff --git a/apps/desktop/src/i18n/types.ts b/apps/desktop/src/i18n/types.ts
index 54534f915e75..c11357d91f6e 100644
--- a/apps/desktop/src/i18n/types.ts
+++ b/apps/desktop/src/i18n/types.ts
@@ -1715,6 +1715,7 @@ export interface Translations {
         reading: string
         opened: string
         opening: string
+        failedToOpen: string
         searched: string
         searching: string
         ran: string
diff --git a/apps/desktop/src/i18n/zh-hant.ts b/apps/desktop/src/i18n/zh-hant.ts
index fbf2ed0822b2..24e0ff12dac3 100644
--- a/apps/desktop/src/i18n/zh-hant.ts
+++ b/apps/desktop/src/i18n/zh-hant.ts
@@ -2122,6 +2122,7 @@ export const zhHant = defineLocale({
         reading: '正在讀取',
         opened: '已開啟',
         opening: '正在開啟',
+        failedToOpen: '開啟失敗',
         searched: '已搜尋',
         searching: '正在搜尋',
         ran: '已執行',
diff --git a/apps/desktop/src/i18n/zh.ts b/apps/desktop/src/i18n/zh.ts
index 6d029367eae7..a528099cc529 100644
--- a/apps/desktop/src/i18n/zh.ts
+++ b/apps/desktop/src/i18n/zh.ts
@@ -2235,6 +2235,7 @@ export const zh: Translations = {
         reading: '正在读取',
         opened: '已打开',
         opening: '正在打开',
+        failedToOpen: '打开失败',
         searched: '已搜索',
         searching: '正在搜索',
         ran: '已运行',
diff --git a/tests/tools/test_browser_open_timeout.py b/tests/tools/test_browser_open_timeout.py
new file mode 100644
index 000000000000..e6fd45491202
--- /dev/null
+++ b/tests/tools/test_browser_open_timeout.py
@@ -0,0 +1,112 @@
+"""Tests for browser first-open timeout and timeout diagnostics."""
+
+from unittest.mock import patch
+
+import pytest
+
+import tools.browser_tool as bt
+
+
+@pytest.fixture(autouse=True)
+def _reset_browser_caches():
+    bt._cached_command_timeout = None
+    bt._command_timeout_resolved = False
+    yield
+    bt._cached_command_timeout = None
+    bt._command_timeout_resolved = False
+
+
+class TestOpenCommandTimeout:
+    def test_first_open_uses_longer_floor(self, monkeypatch):
+        monkeypatch.setattr(bt, "_get_command_timeout", lambda: 30)
+        assert bt._get_open_command_timeout(first_open=True) == bt.MIN_FIRST_OPEN_TIMEOUT
+        assert bt._get_open_command_timeout(first_open=False) == bt.MIN_OPEN_TIMEOUT
+
+    def test_respects_config_above_floor(self, monkeypatch):
+        monkeypatch.setattr(bt, "_get_command_timeout", lambda: 180)
+        assert bt._get_open_command_timeout(first_open=True) == 180
+        assert bt._get_open_command_timeout(first_open=False) == 180
+
+
+class TestSandboxBypass:
+    def test_docker_triggers_bypass(self, monkeypatch):
+        monkeypatch.setattr(bt, "_running_in_docker", lambda: True)
+        assert bt._needs_chromium_sandbox_bypass() is True
+
+    def test_apparmor_userns_triggers_bypass(self, monkeypatch, tmp_path):
+        monkeypatch.setattr(bt, "_running_in_docker", lambda: False)
+        sysctl = tmp_path / "apparmor_restrict_unprivileged_userns"
+        sysctl.write_text("1\n", encoding="utf-8")
+
+        import builtins
+
+        real_open = builtins.open
+
+        def _open(path, *args, **kwargs):
+            if "apparmor_restrict_unprivileged_userns" in str(path):
+                return real_open(sysctl, *args, **kwargs)
+            return real_open(path, *args, **kwargs)
+
+        monkeypatch.setattr(builtins, "open", _open)
+        assert bt._needs_chromium_sandbox_bypass() is True
+
+
+class TestTimeoutErrorFormatting:
+    def test_includes_stderr_detail(self):
+        err = bt._format_browser_timeout_error(
+            "open",
+            120,
+            "",
+            "Daemon process exited during startup",
+        )
+        assert "120 seconds" in err
+        assert "Daemon process exited" in err
+
+    def test_sandbox_hint(self):
+        err = bt._format_browser_timeout_error(
+            "open",
+            60,
+            "",
+            "No usable sandbox!",
+        )
+        assert "AGENT_BROWSER_ARGS" in err
+
+    def test_local_install_hint(self, monkeypatch):
+        monkeypatch.setattr(bt, "_is_local_mode", lambda: True)
+        monkeypatch.setattr(bt, "_running_in_docker", lambda: False)
+        err = bt._format_browser_timeout_error("open", 60, "", "")
+        assert "agent-browser install --with-deps" in err
+
+
+class TestReadCommandOutputFiles:
+    def test_reads_stdout_and_stderr(self, tmp_path):
+        stdout_path = tmp_path / "out"
+        stderr_path = tmp_path / "err"
+        stdout_path.write_text("ok", encoding="utf-8")
+        stderr_path.write_text("warn", encoding="utf-8")
+        stdout, stderr = bt._read_command_output_files(str(stdout_path), str(stderr_path))
+        assert stdout == "ok"
+        assert stderr == "warn"
+
+
+class TestBrowserNavigateOpenTimeout:
+    def test_first_navigation_uses_first_open_timeout(self, monkeypatch):
+        captured: dict = {}
+
+        def fake_run(task_id, command, args, timeout=None):
+            if command == "open":
+                captured["timeout"] = timeout
+            return {"success": True, "data": {"title": "t", "url": args[0] if args else ""}}
+
+        monkeypatch.setattr(bt, "_get_open_command_timeout", lambda first_open=False: 120 if first_open else 60)
+        monkeypatch.setattr(bt, "_run_browser_command", fake_run)
+        monkeypatch.setattr(bt, "_get_session_info", lambda key: {"_first_nav": True, "features": {}})
+        monkeypatch.setattr(bt, "_is_camofox_mode", lambda: False)
+        monkeypatch.setattr(bt, "_is_local_backend", lambda: True)
+        monkeypatch.setattr(bt, "_is_local_sidecar_key", lambda key: False)
+        monkeypatch.setattr(bt, "_navigation_session_key", lambda task_id, url: task_id)
+        monkeypatch.setattr(bt, "_maybe_start_recording", lambda *a, **kw: None)
+        monkeypatch.setattr(bt, "check_website_access", lambda url: None)
+
+        bt.browser_navigate("https://example.com", task_id="task-1")
+        assert captured["timeout"] == 120
diff --git a/tools/browser_tool.py b/tools/browser_tool.py
index 018fc008c8d8..3afc63346dad 100644
--- a/tools/browser_tool.py
+++ b/tools/browser_tool.py
@@ -221,6 +221,11 @@ _last_screenshot_cleanup_by_dir: dict[str, float] = {}
 # Default timeout for browser commands (seconds)
 DEFAULT_COMMAND_TIMEOUT = 30
 
+# Floor for ``open`` (navigate) — cold daemon + first Chromium launch can exceed
+# the generic command_timeout on slow or library-starved Linux hosts.
+MIN_OPEN_TIMEOUT = 60
+MIN_FIRST_OPEN_TIMEOUT = 120
+
 # Max tokens for snapshot content before summarization
 SNAPSHOT_SUMMARIZE_THRESHOLD = 8000
 
@@ -256,6 +261,92 @@ def _get_command_timeout() -> int:
     return result
 
 
+def _get_open_command_timeout(*, first_open: bool = False) -> int:
+    """Timeout for agent-browser ``open`` (navigation / daemon cold start)."""
+    base = _get_command_timeout()
+    floor = MIN_FIRST_OPEN_TIMEOUT if first_open else MIN_OPEN_TIMEOUT
+    return max(base, floor)
+
+
+def _needs_chromium_sandbox_bypass() -> bool:
+    """Return True when Chromium needs --no-sandbox to start reliably."""
+    if hasattr(os, "geteuid") and os.geteuid() == 0:
+        return True
+    if _running_in_docker():
+        return True
+    userns_restrict = "/proc/sys/kernel/apparmor_restrict_unprivileged_userns"
+    try:
+        with open(userns_restrict, encoding="utf-8") as f:
+            if f.read().strip() == "1":
+                return True
+    except OSError:
+        pass
+    return False
+
+
+def _read_command_output_files(stdout_path: str, stderr_path: str) -> tuple[str, str]:
+    """Best-effort read of agent-browser stdout/stderr temp files."""
+    stdout = stderr = ""
+    for path, slot in ((stdout_path, "stdout"), (stderr_path, "stderr")):
+        try:
+            with open(path, "r", encoding="utf-8") as f:
+                text = f.read().strip()
+        except OSError:
+            continue
+        if slot == "stdout":
+            stdout = text
+        else:
+            stderr = text
+    return stdout, stderr
+
+
+def _unlink_command_output_files(*paths: str) -> None:
+    for path in paths:
+        try:
+            os.unlink(path)
+        except OSError:
+            pass
+
+
+def _format_browser_timeout_error(
+    command: str,
+    timeout: int,
+    stdout: str,
+    stderr: str,
+) -> str:
+    """Build an actionable timeout message from captured daemon output."""
+    parts = [f"Command timed out after {timeout} seconds"]
+    detail = (stderr or stdout or "").strip()
+    if detail:
+        parts.append(detail[:1500])
+
+    combined = f"{stderr}\n{stdout}".lower()
+    hints: list[str] = []
+    if "sandbox" in combined:
+        hints.append(
+            "Chromium sandbox launch failed. Set AGENT_BROWSER_ARGS="
+            "'--no-sandbox,--disable-dev-shm-usage' in your environment, "
+            "or run: npx agent-browser install --with-deps"
+        )
+    elif command == "open" and _is_local_mode():
+        if _running_in_docker():
+            hints.append(
+                "The browser daemon may still be starting or Chromium may be "
+                "missing. Pull the latest image: "
+                "docker pull ghcr.io/nousresearch/hermes-agent:latest"
+            )
+        else:
+            hints.append(
+                "The browser daemon may still be starting, or Chromium may be "
+                "missing system libraries. Install/repair with: "
+                "npx agent-browser install --with-deps "
+                "(or: npx playwright install --with-deps chromium)"
+            )
+    if hints:
+        parts.extend(hints)
+    return "\n".join(parts)
+
+
 def _get_vision_model() -> Optional[str]:
     """Model for browser_vision (screenshot analysis — multimodal)."""
     return os.getenv("AUXILIARY_VISION_MODEL", "").strip() or None
@@ -2187,24 +2278,11 @@ def _run_browser_command(
             "AGENT_BROWSER_ARGS" not in browser_env
             and "AGENT_BROWSER_CHROME_FLAGS" not in browser_env
         ):
-            _needs_sandbox_bypass = False
-            if hasattr(os, "geteuid") and os.geteuid() == 0:
-                _needs_sandbox_bypass = True
-                logger.debug("browser: running as root — injecting --no-sandbox")
-            else:
-                # Detect AppArmor user namespace restrictions (Ubuntu 23.10+)
-                _userns_restrict = "/proc/sys/kernel/apparmor_restrict_unprivileged_userns"
-                try:
-                    with open(_userns_restrict, encoding="utf-8") as _f:
-                        if _f.read().strip() == "1":
-                            _needs_sandbox_bypass = True
-                            logger.debug(
-                                "browser: AppArmor userns restrictions detected — "
-                                "injecting --no-sandbox"
-                            )
-                except OSError:
-                    pass
-            if _needs_sandbox_bypass:
+            if _needs_chromium_sandbox_bypass():
+                logger.debug(
+                    "browser: sandbox bypass needed (root/docker/AppArmor userns) — "
+                    "injecting --no-sandbox"
+                )
                 browser_env["AGENT_BROWSER_ARGS"] = (
                     "--no-sandbox,--disable-dev-shm-usage"
                 )
@@ -2252,9 +2330,20 @@ def _run_browser_command(
         except subprocess.TimeoutExpired:
             proc.kill()
             proc.wait()
+            stdout, stderr = _read_command_output_files(stdout_path, stderr_path)
+            _unlink_command_output_files(stdout_path, stderr_path)
+            if stderr and stderr.strip():
+                logger.warning(
+                    "browser '%s' stderr after timeout: %s",
+                    command,
+                    stderr.strip()[:500],
+                )
             logger.warning("browser '%s' timed out after %ds (task=%s, socket_dir=%s)",
                            command, timeout, task_id, task_socket_dir)
-            result = {"success": False, "error": f"Command timed out after {timeout} seconds"}
+            result = {
+                "success": False,
+                "error": _format_browser_timeout_error(command, timeout, stdout, stderr),
+            }
             # Fall through to fallback check below
         else:
             with open(stdout_path, "r", encoding="utf-8") as f:
@@ -2554,7 +2643,12 @@ def browser_navigate(url: str, task_id: Optional[str] = None) -> str:
         session_info["_first_nav"] = False
         _maybe_start_recording(nav_session_key)
 
-    result = _run_browser_command(nav_session_key, "open", [url], timeout=max(_get_command_timeout(), 60))
+    result = _run_browser_command(
+        nav_session_key,
+        "open",
+        [url],
+        timeout=_get_open_command_timeout(first_open=is_first_nav),
+    )
 
     # Remember which session served this nav so snapshot/click/fill/...
     # on the same task_id hit it (critical when hybrid routing has both a