diff --git a/tests/tools/test_tour_tool.py b/tests/tools/test_tour_tool.py
new file mode 100644
index 0000000000..f6147f6274
--- /dev/null
+++ b/tests/tools/test_tour_tool.py
@@ -0,0 +1,80 @@
+"""Tests for the GUI-surface ``tour`` tool."""
+
+import json
+
+from tools import tour_tool as tt
+from tools.registry import registry
+
+
+def _run(**kwargs):
+    kwargs.setdefault("callback", lambda _payload: json.dumps({"success": True}))
+    return json.loads(tt.tour_tool(**kwargs))
+
+
+def test_lives_in_the_gui_surface_toolset(monkeypatch):
+    """Scoped by toolset, not by the backend's env — see AGENTS.md."""
+    monkeypatch.delenv("HERMES_DESKTOP", raising=False)
+    entry = registry.get_entry("tour")
+
+    assert entry is not None
+    assert entry.toolset == "desktop_ui"
+    assert entry.check_fn is None
+
+
+def test_requires_callback():
+    """Outside the desktop GUI there is no bridge — a clear error, no crash."""
+    assert "desktop" in json.loads(tt.tour_tool(action="targets", callback=None))["error"]
+
+
+def test_rejects_unknown_action_and_surface():
+    assert "action must be one of" in _run(action="dance")["error"]
+    assert "surface must be one of" in _run(action="targets", surface="hologram")["error"]
+    assert "side must be one of" in _run(action="show", selector="#a", side="diagonal")["error"]
+
+
+def test_show_needs_something_to_point_at_or_say():
+    assert "show needs" in _run(action="show")["error"]
+    assert "error" not in _run(action="show", text="just narration")
+
+
+def test_start_validates_its_steps():
+    assert "non-empty steps" in _run(action="start")["error"]
+    assert "non-empty steps" in _run(action="start", steps=[])["error"]
+    assert "steps[1] must be an object" in _run(action="start", steps=[{"selector": "#a"}, "nope"])["error"]
+    assert "steps[1] needs" in _run(action="start", steps=[{"selector": "#a"}, {}])["error"]
+
+
+def test_payload_omits_unset_fields_and_defaults_the_surface():
+    seen = {}
+
+    def cb(payload):
+        seen.update(payload)
+        return json.dumps({"success": True})
+
+    tt.tour_tool(action="show", selector="#composer", title="Composer", callback=cb)
+    assert seen == {
+        "action": "show",
+        "surface": "app",
+        "selector": "#composer",
+        "title": "Composer",
+    }
+
+
+def test_unanswered_bridge_is_reported_rather_than_faked_as_success():
+    assert "error" in _run(action="targets", callback=lambda _p: "")
+
+
+def test_passes_renderer_json_through():
+    payload = {"success": True, "matched": True, "step": 2}
+    assert _run(action="next", callback=lambda _p: json.dumps(payload)) == payload
+
+
+def test_wraps_non_json_text():
+    assert _run(action="stop", callback=lambda _p: "stopped") == {"text": "stopped"}
+
+
+def test_callback_failure_is_reported():
+    def _boom(_payload):
+        raise RuntimeError("renderer went away")
+
+    assert "renderer went away" in _run(action="stop", callback=_boom)["error"]
diff --git a/tests/tui_gateway/test_tour_bridge_fail_fast.py b/tests/tui_gateway/test_tour_bridge_fail_fast.py
new file mode 100644
index 0000000000..0699895d55
--- /dev/null
+++ b/tests/tui_gateway/test_tour_bridge_fail_fast.py
@@ -0,0 +1,101 @@
+"""A desktop client that cannot answer ``tour.request`` must not cost a full
+bridge timeout per call.
+
+The renderer's handler ships in the desktop bundle; the tool is offered by the
+backend. An app build older than the tour tool has no branch for the event, so
+nothing ever calls ``tour.respond`` and the agent blocks for the whole deadline
+— once per action the model tries. See tui_gateway.server._tour_request.
+"""
+
+import json
+
+import pytest
+
+import tui_gateway.server as server
+
+
+@pytest.fixture
+def session(monkeypatch):
+    record = {}
+    monkeypatch.setitem(server._sessions, "s1", record)
+    return record
+
+
+@pytest.fixture
+def bridge(monkeypatch):
+    """Record every _block call and serve canned answers."""
+    calls = []
+
+    def fake_block(event, sid, payload, timeout=None, **_kw):
+        answer = fake_block.answers.pop(0) if fake_block.answers else ""
+        calls.append({"event": event, "sid": sid, "payload": payload, "timeout": timeout})
+        return answer
+
+    fake_block.answers = []
+    fake_block.calls = calls
+    monkeypatch.setattr(server, "_block", fake_block)
+    return fake_block
+
+
+def test_first_action_is_probed_on_a_short_deadline(session, bridge):
+    bridge.answers = [json.dumps({"success": True})]
+    server._tour_request("s1", {"action": "targets"})
+
+    assert bridge.calls[0]["event"] == "tour.request"
+    assert bridge.calls[0]["timeout"] == server._TOUR_PROBE_TIMEOUT_S
+    assert server._TOUR_PROBE_TIMEOUT_S < server._TOUR_TIMEOUT_S
+
+
+def test_a_client_that_answers_gets_the_full_deadline_back(session, bridge):
+    """The generous deadline exists for a preview tour injecting into a live
+    page; only an unproven client is held to the probe."""
+    bridge.answers = [json.dumps({"success": True}), json.dumps({"success": True})]
+    server._tour_request("s1", {"action": "targets"})
+    server._tour_request("s1", {"action": "show", "selector": "#composer"})
+
+    assert bridge.calls[1]["timeout"] == server._TOUR_TIMEOUT_S
+
+
+def test_unanswered_probe_explains_the_real_problem(session, bridge):
+    result = json.loads(server._tour_request("s1", {"action": "targets"}))
+
+    assert result["success"] is False
+    assert "desktop" in result["error"].lower()
+    assert "update" in result["error"].lower()
+
+
+def test_later_actions_short_circuit_instead_of_stalling_again(session, bridge):
+    """The regression: a "give me a tour" turn stacks one timeout per action."""
+    server._tour_request("s1", {"action": "targets"})
+    for action in ("show", "start", "next", "stop"):
+        assert json.loads(server._tour_request("s1", {"action": action}))["success"] is False
+
+    assert len(bridge.calls) == 1
+
+
+def test_a_proven_client_is_not_condemned_by_one_slow_action(session, bridge):
+    """A transient miss on a live renderer must not disable the tour."""
+    bridge.answers = [json.dumps({"success": True})]
+    server._tour_request("s1", {"action": "targets"})
+    server._tour_request("s1", {"action": "show", "selector": "#composer"})
+
+    bridge.answers = [json.dumps({"success": True})]
+    assert json.loads(server._tour_request("s1", {"action": "next"}))["success"] is True
+    assert len(bridge.calls) == 3
+
+
+def test_a_new_session_reprobes(bridge, monkeypatch):
+    """The verdict lives on the session record, so it dies with the session."""
+    monkeypatch.setitem(server._sessions, "dead", {})
+    monkeypatch.setitem(server._sessions, "fresh", {})
+
+    server._tour_request("dead", {"action": "targets"})
+    bridge.answers = [json.dumps({"success": True})]
+
+    assert json.loads(server._tour_request("fresh", {"action": "targets"}))["success"] is True
+
+
+def test_a_session_with_no_record_still_bridges(bridge):
+    """Detached callers have no session dict; they keep the plain bridge."""
+    bridge.answers = [json.dumps({"success": True})]
+    assert json.loads(server._tour_request("gone", {"action": "targets"}))["success"] is True
diff --git a/tui_gateway/server.py b/tui_gateway/server.py
index 9493814bd0..11d2cb1791 100644
--- a/tui_gateway/server.py
+++ b/tui_gateway/server.py
@@ -3618,6 +3618,74 @@ def _clarify_block(sid: str, q, c, multi_select=False, questions=None) -> str:
     )
 
 
+# A tour action is a DOM operation the renderer performs and answers straight
+# back, so a client that implements the bridge replies in milliseconds. The
+# generous deadline exists for one case only: a preview tour's first action
+# injects the engine into a live page.
+_TOUR_TIMEOUT_S = 45
+# Until a session's client has proven it answers at all, hold it to a deadline
+# a working renderer cannot miss. See _tour_request.
+_TOUR_PROBE_TIMEOUT_S = 10
+
+_TOUR_BRIDGE_UNAVAILABLE = json.dumps(
+    {
+        "success": False,
+        "error": (
+            "No Hermes Desktop window answered the tour request. The tour is "
+            "driven by the desktop app's renderer, which updates separately "
+            "from this backend, so an app build older than the tour tool has "
+            "nothing listening. Update the Hermes Desktop app and start a new "
+            "session. Do not retry tour in this session."
+        ),
+    }
+)
+
+
+def _tour_request(sid: str, payload: dict) -> str:
+    """Bridge the tour tool callback onto _block, without paying for a client
+    that cannot answer it.
+
+    The renderer's ``tour.request`` handler ships in the desktop bundle, but
+    the tool is offered by this backend — and the two update on different
+    clocks. Against an app older than the tool the event lands in a renderer
+    with no branch for it, nobody ever calls ``tour.respond``, and the agent
+    blocks for the full deadline. The model then does what the schema tells it
+    to and tries the next action, so a single "give me a tour" turn stacks
+    those waits (the timeouts reported against #89620).
+
+    A session's first action therefore gets the probe deadline, and an
+    unanswered probe marks the bridge unavailable for that session: every later
+    call returns immediately, telling the user what to actually fix instead of
+    stalling again. Once a client has answered, real actions get the full
+    deadline back and a single slow one no longer condemns it. The verdict
+    lives on the session record, so it dies with the session and a new one
+    re-probes.
+    """
+    # A detached caller has no session record; the throwaway keeps it on the
+    # plain bridge, unprobed.
+    session = _sessions.get(sid)
+    if session is None:
+        session = {}
+    state = session.get("tour_bridge")
+
+    if state == "unanswered":
+        return _TOUR_BRIDGE_UNAVAILABLE
+
+    answer = _block(
+        "tour.request",
+        sid,
+        dict(payload),
+        timeout=_TOUR_TIMEOUT_S if state == "answered" else _TOUR_PROBE_TIMEOUT_S,
+    )
+
+    if answer:
+        session["tour_bridge"] = "answered"
+    elif state != "answered":
+        session["tour_bridge"] = "unanswered"
+
+    return answer or _TOUR_BRIDGE_UNAVAILABLE
+
+
 def _clear_pending(sid: str | None = None) -> None:
     """Release pending prompts with an empty answer.
 
@@ -6325,14 +6393,8 @@ def _agent_cbs(sid: str) -> dict:
         # tour tool (desktop GUI): the renderer drives driver.js — highlighting
         # elements in the app's own DOM or injecting the engine into the
         # preview pane's webview — and answers tour.respond with the outcome
-        # (did the selector match, which step is active). Generous timeout: a
-        # preview tour's first action loads the engine into a live page.
-        "tour_callback": lambda payload: _block(
-            "tour.request",
-            sid,
-            dict(payload),
-            timeout=45,
-        ),
+        # (did the selector match, which step is active).
+        "tour_callback": lambda payload: _tour_request(sid, payload),
     }
 
     # Interim assistant commentary (text alongside tool calls, or the attempted