diff --git a/features/steps/tdd_tui_block_cursor_navigation_steps.py b/features/steps/tdd_tui_block_cursor_navigation_steps.py
new file mode 100644
index 000000000..706b73b61
--- /dev/null
+++ b/features/steps/tdd_tui_block_cursor_navigation_steps.py
@@ -0,0 +1,54 @@
+"""Step definitions for tdd_tui_block_cursor_navigation.feature.
+
+This test captures bug #10371: the TUI application is missing ``alt+up``
+and ``alt+down`` key bindings for block cursor navigation.
+
+The scenario is tagged ``@tdd_expected_fail`` so the underlying assertion
+failure (confirming the bug exists) is inverted to a CI pass.  Once the
+fix for #10371 is merged, remove the ``@tdd_expected_fail`` tag from the
+feature file and this test will run normally as a regression guard.
+
+The ``Given the TUI app module is imported with mocked Textual`` step is
+shared from ``tui_app_coverage_steps.py`` and is not redefined here.
+"""
+
+from __future__ import annotations
+
+from typing import Any
+
+from behave import then, when
+
+
+@when("I inspect the TUI app BINDINGS for block cursor navigation")
+def step_inspect_bindings(context: Any) -> None:
+    """Collect the BINDINGS class variable from the reloaded TUI app module.
+
+    The ``_tui_app_mod`` attribute is set by the shared
+    ``Given the TUI app module is imported with mocked Textual`` step
+    (defined in ``tui_app_coverage_steps.py``).
+    """
+    app_mod = context._tui_app_mod
+    # _TextualCleverAgentsTuiApp is only defined when Textual is available.
+    # The Background step mocks Textual, so the class must exist here.
+    assert hasattr(app_mod, "_TextualCleverAgentsTuiApp"), (
+        "Expected _TextualCleverAgentsTuiApp to be defined after mocking Textual"
+    )
+    tui_class = app_mod._TextualCleverAgentsTuiApp
+    context.tdd_tui_bindings = list(tui_class.BINDINGS)
+
+
+@then('the BINDINGS should include "{key}" key binding')
+def step_bindings_include_key(context: Any, key: str) -> None:
+    """Assert that the given key is registered in the TUI app BINDINGS.
+
+    Bug #10371: ``alt+up`` and ``alt+down`` are absent from BINDINGS, so
+    this assertion raises ``AssertionError`` while the bug is unfixed.
+    The ``@tdd_expected_fail`` tag inverts the failure to a CI pass.
+    """
+    bindings: list[tuple[str, str, str]] = context.tdd_tui_bindings
+    bound_keys = [binding[0] for binding in bindings]
+    assert key in bound_keys, (
+        f"Bug #10371: Key binding '{key}' is not registered in "
+        f"CleverAgentsTuiApp.BINDINGS. "
+        f"Current bindings: {bound_keys}"
+    )
diff --git a/features/tdd_tui_block_cursor_navigation.feature b/features/tdd_tui_block_cursor_navigation.feature
new file mode 100644
index 000000000..1cc0fe827
--- /dev/null
+++ b/features/tdd_tui_block_cursor_navigation.feature
@@ -0,0 +1,19 @@
+@tdd_issue @tdd_issue_10371
+Feature: TDD Issue #10371 — Block cursor navigation (alt+up/alt+down) not implemented in TUI
+
+  This test captures bug #10371: the TUI application is missing ``alt+up``
+  and ``alt+down`` key bindings for block cursor navigation.
+
+  The scenario is tagged ``@tdd_expected_fail`` so the underlying assertion
+  failure (confirming the bug exists) is inverted to a CI pass.  Once the
+  fix for #10371 is merged, remove the ``@tdd_expected_fail`` tag from the
+  scenario and this test will run normally as a regression guard.
+
+  See CONTRIBUTING.md > Bug Fix Workflow > TDD Issue Test Tags.
+
+  @tdd_expected_fail
+  Scenario: TUI app BINDINGS includes alt+up and alt+down for block cursor navigation
+    Given the TUI app module is imported with mocked Textual
+    When I inspect the TUI app BINDINGS for block cursor navigation
+    Then the BINDINGS should include "alt+up" key binding
+    And the BINDINGS should include "alt+down" key binding