diff --git a/docs/plain2code_cli.md b/docs/plain2code_cli.md
index dd10bed5..157c6af9 100644
--- a/docs/plain2code_cli.md
+++ b/docs/plain2code_cli.md
@@ -19,7 +19,8 @@ usage: generate_cli.py [-h] [--verbose] [--base-folder BASE_FOLDER]
                        [--conformance-tests-dest CONFORMANCE_TESTS_DEST]
                        [--render-machine-graph]
                        [--logging-config-path LOGGING_CONFIG_PATH]
-                       [--headless] [--status] [--version]
+                       [--headless] [--exit-when-done | --no-exit-when-done]
+                       [--status] [--version]
                        [filename]
 
 Render plain code to target code. Path arguments resolve based on where they
@@ -131,6 +132,14 @@ options:
                         specification text itself stays in the log file only.
                         Used automatically when stdin, stdout or stderr is not
                         a terminal.
+  --exit-when-done, --no-exit-when-done
+                        Close the terminal interface as soon as rendering
+                        stops, instead of keeping it open until you press
+                        Enter. The render summary is printed to the terminal
+                        as usual. Use --no-exit-when-done to keep the
+                        interface open when config.yaml turns this on.
+                        Headless rendering always ends by itself, so the
+                        option changes nothing there.
   --status              Display account status including user information, API
                         key label, and rendering credits. Does not render any
                         code.
diff --git a/plain2code.py b/plain2code.py
index 93842b8d..126b354a 100644
--- a/plain2code.py
+++ b/plain2code.py
@@ -453,6 +453,7 @@ def run_render():
             enter_pause_event=enter_pause_event,
             on_cancel=run_state.set_render_cancelled,
             default_log_level=default_log_level,
+            exit_when_done=args.exit_when_done,
             css_path="styles.css",
         )
         app.run()
@@ -591,7 +592,7 @@ def main():  # noqa: C901
         print_exit_summary(
             run_state,
             args.filename,
-            error_message=error_message,
+            error_message=error_message or run_state.render_error_message,
         )
         # Remove any scratch extractions created for archive-only ("<module>.module") modules.
         for module in plain_module.all_required_modules + [plain_module]:
diff --git a/plain2code_arguments.py b/plain2code_arguments.py
index ff7b9355..e9e783f2 100644
--- a/plain2code_arguments.py
+++ b/plain2code_arguments.py
@@ -511,6 +511,17 @@ def create_parser():
         "Used automatically when stdin, stdout or stderr is not a terminal.",
     )
 
+    _add_arg(
+        parser,
+        "--exit-when-done",
+        action=argparse.BooleanOptionalAction,
+        default=False,
+        help="Close the terminal interface as soon as rendering stops, instead of keeping it open "
+        "until you press Enter. The render summary is printed to the terminal as usual. "
+        "Use --no-exit-when-done to keep the interface open when config.yaml turns this on. "
+        "Headless rendering always ends by itself, so the option changes nothing there.",
+    )
+
     parser.add_argument(
         "--status",
         action="store_true",
diff --git a/plain2code_state.py b/plain2code_state.py
index a295cb97..8a49634b 100644
--- a/plain2code_state.py
+++ b/plain2code_state.py
@@ -12,6 +12,8 @@ def __init__(self, spec_filename: str, replay_with: Optional[str] = None, job_ta
         self.replay: bool = replay_with is not None
         self.render_succeeded: bool = False
         self.render_cancelled: bool = False
+        # Why the render failed, as the TUI showed it; printed in the summary after the TUI closes.
+        self.render_error_message: Optional[str] = None
         self.render_generated_code_path: Optional[str] = None
         self.rendered_functionalities: int = 0
         if replay_with:
@@ -39,6 +41,9 @@ def increment_unittest_batch_id(self):
     def set_render_succeeded(self, succeeded: bool):
         self.render_succeeded = succeeded
 
+    def set_render_error_message(self, error_message: str):
+        self.render_error_message = error_message
+
     def set_render_cancelled(self):
         self.render_cancelled = True
 
diff --git a/tests/test_exit_when_done.py b/tests/test_exit_when_done.py
new file mode 100644
index 00000000..f331fcb5
--- /dev/null
+++ b/tests/test_exit_when_done.py
@@ -0,0 +1,151 @@
+"""Tests for --exit-when-done: the TUI closes by itself once rendering has stopped."""
+
+import asyncio
+import threading
+
+import pytest
+
+from event_bus import EventBus
+from plain2code_arguments import create_parser, parse_arguments
+from plain2code_events import LogMessageEmitted, RenderCompleted, RenderFailed
+from plain2code_state import RunState
+from tui.plain2code_tui import Plain2CodeTUI
+
+
+def _make_app(run_state: RunState, event_bus: EventBus, exit_when_done: bool, on_ready=lambda: None) -> Plain2CodeTUI:
+    return Plain2CodeTUI(
+        event_bus=event_bus,
+        run_state=run_state,
+        on_ready=on_ready,
+        render_id="test-render-id",
+        unittests_script=None,
+        conformance_tests_script=None,
+        prepare_environment_script=None,
+        state_machine_version="0.0.0",
+        exit_when_done=exit_when_done,
+        css_path="styles.css",
+    )
+
+
+def _run(exit_when_done: bool, event) -> bool:
+    """Publish ``event`` to a mounted TUI and report whether the TUI closed itself."""
+
+    async def scenario() -> bool:
+        event_bus = EventBus()
+        run_state = RunState(spec_filename="x.plain")
+        app = _make_app(run_state, event_bus, exit_when_done)
+        async with app.run_test() as pilot:
+            event_bus.publish(event)
+            await pilot.pause()
+            return app._exit
+
+    return asyncio.run(scenario())
+
+
+def test_tui_closes_itself_when_rendering_completes():
+    assert _run(True, RenderCompleted(rendered_code_path="plain_modules/x/")) is True
+
+
+def test_tui_closes_itself_when_rendering_fails():
+    assert _run(True, RenderFailed(error_message="Conformance tests failed")) is True
+
+
+def test_tui_keeps_the_failure_reason_for_the_summary():
+    """The TUI closes right away, so the reason it showed must survive on the run state."""
+
+    async def scenario() -> RunState:
+        event_bus = EventBus()
+        run_state = RunState(spec_filename="x.plain")
+        app = _make_app(run_state, event_bus, True)
+        async with app.run_test() as pilot:
+            event_bus.publish(RenderFailed(error_message="Conformance tests failed"))
+            await pilot.pause()
+        return run_state
+
+    assert asyncio.run(scenario()).render_error_message == "Conformance tests failed"
+
+
+def test_tui_waits_for_the_user_without_the_option():
+    assert _run(False, RenderCompleted(rendered_code_path="plain_modules/x/")) is False
+    assert _run(False, RenderFailed(error_message="Conformance tests failed")) is False
+
+
+def test_tui_closes_itself_when_the_render_thread_reports_completion():
+    """The render runs in its own thread, so the completion event reaches the TUI from there."""
+
+    async def scenario() -> bool:
+        event_bus = EventBus()
+        run_state = RunState(spec_filename="x.plain")
+        app = _make_app(run_state, event_bus, True)
+        async with app.run_test() as pilot:
+            thread = threading.Thread(
+                target=lambda: event_bus.publish(RenderCompleted(rendered_code_path="plain_modules/x/"))
+            )
+            thread.start()
+            thread.join()
+            await pilot.pause()
+            return app._exit
+
+    assert asyncio.run(scenario()) is True
+
+
+def _log(message: str) -> LogMessageEmitted:
+    return LogMessageEmitted(logger_name="codeplain", level="INFO", message=message, timestamp="00:00:01")
+
+
+@pytest.mark.parametrize(
+    "event", [RenderCompleted(rendered_code_path="plain_modules/x/"), RenderFailed(error_message="x")]
+)
+def test_tui_closes_cleanly_while_log_lines_are_still_arriving(event):
+    """Log lines reach the TUI from the render thread right up to (and past) the final event.
+
+    Entries still waiting to be drawn when the TUI closes must not crash it: before the fix,
+    mounting them into the torn-down log view raised MountError, which run_test re-raises.
+    """
+
+    async def scenario() -> bool:
+        event_bus = EventBus()
+        run_state = RunState(spec_filename="x.plain")
+
+        def render():
+            for i in range(20):
+                event_bus.publish(_log(f"step {i}"))
+            event_bus.publish(event)
+            for i in range(20):
+                event_bus.publish(_log(f"after {i}"))
+
+        # Started from on_ready, exactly as plain2code.render() starts the render thread.
+        render_thread = threading.Thread(target=render, daemon=True)
+        app = _make_app(run_state, event_bus, True, on_ready=render_thread.start)
+        async with app.run_test() as pilot:
+            for _ in range(100):
+                if app._exit and not render_thread.is_alive():
+                    break
+                await pilot.pause(0.01)
+            return app._exit
+
+    assert asyncio.run(scenario()) is True
+
+
+def test_option_is_off_by_default():
+    args = create_parser().parse_args(["x.plain"])
+    assert args.exit_when_done is False
+
+
+def test_option_turns_on_from_the_command_line():
+    args = create_parser().parse_args(["x.plain", "--exit-when-done"])
+    assert args.exit_when_done is True
+
+
+def test_option_turns_off_from_the_command_line():
+    args = create_parser().parse_args(["x.plain", "--no-exit-when-done"])
+    assert args.exit_when_done is False
+
+
+def test_command_line_turns_off_an_exit_configured_in_config_yaml(tmp_path, monkeypatch):
+    (tmp_path / "x.plain").write_text("")
+    (tmp_path / "config.yaml").write_text("exit-when-done: true\n")
+    monkeypatch.chdir(tmp_path)
+
+    assert parse_arguments([str(tmp_path / "x.plain")]).exit_when_done is True
+    assert parse_arguments([str(tmp_path / "x.plain"), "--no-exit-when-done"]).exit_when_done is False
diff --git a/tests/test_render_finished_report.py b/tests/test_render_finished_report.py
index 98baf38d..63c27a2b 100644
--- a/tests/test_render_finished_report.py
+++ b/tests/test_render_finished_report.py
@@ -108,7 +108,7 @@ def make_args(api_key="test-key", headless=False):
     )
 
 
-def run_main(render_side_effect=None, api_key="test-key"):
+def run_main(render_side_effect=None, api_key="test-key", print_exit_summary=None):
     """Drive main() with everything but the reporting path stubbed out.
 
     render() is replaced, so the stub is what decides how the render "ended" -
@@ -134,7 +134,7 @@ def fake_render(plain_module, codeplainAPI, args, run_state, event_bus, default_
         patch("plain2code.setup_logging", return_value="INFO"),
         patch("plain2code.initialize_telemetry"),
         patch("plain2code.stop_narrating"),
-        patch("plain2code.print_exit_summary"),
+        patch("plain2code.print_exit_summary", print_exit_summary or MagicMock()),
         patch("plain2code.dump_crash_logs"),
         patch("plain2code.capture_crash"),
         patch("plain2code.codeplain_api.CodeplainAPI", return_value=api),
@@ -204,3 +204,38 @@ def test_a_missing_api_key_reports_nothing(self):
         api = run_main(api_key=None)
 
         api.render_finished.assert_not_called()
+
+
+class TestSummaryShowsWhyTheRenderFailed:
+    """A failure inside the render machine reaches main() only through the run state.
+
+    The state machine publishes RenderFailed without raising, so render() returns normally
+    and main() has no error of its own. The TUI keeps the reason on the run state; with
+    --exit-when-done the summary is the only place the user still sees it.
+    """
+
+    def test_the_reason_the_tui_kept_is_printed(self):
+        def fail_inside_the_render_machine(run_state):
+            run_state.set_render_succeeded(False)
+            run_state.set_render_error_message("Conformance tests still fail after 20 attempts.")
+
+        summary = MagicMock()
+        run_main(fail_inside_the_render_machine, print_exit_summary=summary)
+
+        assert summary.call_args.kwargs["error_message"] == "Conformance tests still fail after 20 attempts."
+
+    def test_a_raised_error_still_wins(self):
+        def fail(run_state):
+            run_state.set_render_error_message("reason the TUI kept")
+            raise Exception("rendering blew up")
+
+        summary = MagicMock()
+        run_main(fail, print_exit_summary=summary)
+
+        assert summary.call_args.kwargs["error_message"] == "rendering blew up"
+
+    def test_a_successful_render_has_no_error_message(self):
+        summary = MagicMock()
+        run_main(lambda run_state: run_state.set_render_succeeded(True), print_exit_summary=summary)
+
+        assert summary.call_args.kwargs["error_message"] is None
diff --git a/tests/test_terminal_attachment.py b/tests/test_terminal_attachment.py
index 641f6bd0..f1bca60a 100644
--- a/tests/test_terminal_attachment.py
+++ b/tests/test_terminal_attachment.py
@@ -84,6 +84,7 @@ def make_args():
         render_from=None,
         force_render=False,
         headless=False,
+        exit_when_done=False,
         replay_with=None,
         job_tag=None,
         log_to_file=False,
diff --git a/tui/components.py b/tui/components.py
index 58c4ebaa..841d2241 100644
--- a/tui/components.py
+++ b/tui/components.py
@@ -624,12 +624,20 @@ def _should_show_log(self, level: str) -> bool:
     async def add_log(
         self, logger_name: str, level: str, message: str, timestamp: str = "", log_color: Optional[str] = None
     ):
-        """Add a new log entry."""
+        """Add a new log entry.
+
+        Log entries are scheduled from the render thread, so one can still be pending when the
+        TUI closes (e.g. with --exit-when-done). Once the view is detached from the DOM the entry
+        is dropped instead of mounted, since mounting into a detached widget raises MountError.
+        The check runs right before each mount because the view can detach while awaiting.
+        """
         # Check if this is a success message that should have spacing before it
         is_success_message = any(keyword in message.lower() for keyword in LogEntry.SUCCESS_KEYWORDS)
 
         # Add empty line before success messages
         if is_success_message:
+            if not self.is_attached:
+                return
             spacer = Static("", classes="log-spacer")
             await self.mount(spacer)
 
@@ -639,6 +647,8 @@ async def add_log(
         if not self._should_show_log(level):
             entry.display = False
 
+        if not self.is_attached:
+            return
         await self.mount(entry)
         # Auto-scroll to bottom to show latest logs
         self.scroll_end(animate=False)
diff --git a/tui/plain2code_tui.py b/tui/plain2code_tui.py
index cb492d46..dcd992a7 100644
--- a/tui/plain2code_tui.py
+++ b/tui/plain2code_tui.py
@@ -84,6 +84,7 @@ def __init__(
         enter_pause_event: threading.Event | None = None,
         on_cancel: Callable[[], None] | None = None,
         default_log_level: str = "INFO",
+        exit_when_done: bool = False,
         **kwargs,
     ):
         super().__init__(**kwargs)
@@ -104,6 +105,7 @@ def __init__(
         self.enter_pause_event = enter_pause_event
         self._on_cancel = on_cancel
         self.default_log_level = default_log_level
+        self.exit_when_done = exit_when_done
         self._render_finished = False
 
         # Initialize state handlers
@@ -336,10 +338,14 @@ def on_render_completed(self, event: RenderCompleted):
             footer.update_footer_state("finished")
         except NoMatches:
             pass
+        self._exit_when_done()
 
     def on_render_failed(self, event: RenderFailed):
         """Handle render failure."""
         self._render_error_handler.handle(event.error_message)
+        # A failure inside the render machine is not raised, so main() has no error message of
+        # its own; keep the reason so the summary printed after the TUI closes can show it.
+        self.run_state.set_render_error_message(event.error_message)
         self._render_finished = True
         self._finalize_usage_summary()
         try:
@@ -347,6 +353,18 @@ def on_render_failed(self, event: RenderFailed):
             footer.update_footer_state("finished")
         except NoMatches:
             pass
+        self._exit_when_done()
+
+    def _exit_when_done(self) -> None:
+        """Close the TUI once rendering has stopped, when --exit-when-done asked for it.
+
+        Both render outcomes are reported on the terminal after the TUI closes, so nothing
+        the user needs is lost. The events arrive on the render thread. The exit is queued
+        behind the log entries the render thread has already scheduled, so those are drawn
+        before the TUI starts shutting down; entries scheduled later are dropped by the log view.
+        """
+        if self.exit_when_done:
+            self.call_later(self.exit)
 
     async def action_copy_selection(self) -> None:
         """Handle ctrl+c: copy selected text if any.