diff --git a/ductor_bot/cli/process_registry.py b/ductor_bot/cli/process_registry.py
index e089854e..b5a51f57 100644
--- a/ductor_bot/cli/process_registry.py
+++ b/ductor_bot/cli/process_registry.py
@@ -36,6 +36,7 @@ class ProcessRegistry:
     def __init__(self) -> None:
         self._processes: dict[int, list[TrackedProcess]] = {}
         self._aborted: set[int] = set()
+        self._aborted_topics: set[tuple[int, int | None]] = set()
         self._aborted_labels: set[tuple[int, str]] = set()
         self._interrupted: set[int] = set()
         # MED #9: serialize bulk kill operations (kill_for_task / kill_stale /
@@ -102,6 +103,30 @@ async def kill_all(self, chat_id: int) -> int:
             return 0
         return await _kill_processes(entries)
 
+    async def kill_by_chat_topic(self, chat_id: int, topic_id: int | None) -> int:
+        """Kill processes belonging to *chat_id* + *topic_id*. Returns count.
+
+        Used by ``/stop`` so a stop in one topic does not affect another
+        topic in the same chat. ``topic_id=None`` matches processes
+        registered without a topic (e.g. private chats).
+        """
+        async with self._kill_lock:
+            entries = self._processes.get(chat_id, [])
+            targets = [
+                t for t in entries if t.topic_id == topic_id and t.process.returncode is None
+            ]
+            if not targets:
+                return 0
+            self._aborted_topics.add((chat_id, topic_id))
+            remaining = [
+                t for t in entries if t.topic_id != topic_id or t.process.returncode is not None
+            ]
+            if remaining:
+                self._processes[chat_id] = remaining
+            else:
+                self._processes.pop(chat_id, None)
+        return await _kill_processes(targets)
+
     async def kill_all_active(self) -> int:
         """Kill active processes across all chats. Returns total count killed."""
         total = 0
@@ -117,6 +142,14 @@ def clear_abort(self, chat_id: int) -> None:
         """Clear the abort flag for *chat_id*."""
         self._aborted.discard(chat_id)
 
+    def was_aborted_topic(self, chat_id: int, topic_id: int | None) -> bool:
+        """Check whether *(chat_id, topic_id)* has been aborted since last clear."""
+        return (chat_id, topic_id) in self._aborted_topics
+
+    def clear_topic_abort(self, chat_id: int, topic_id: int | None) -> None:
+        """Clear the topic-scoped abort flag (called after handling the abort)."""
+        self._aborted_topics.discard((chat_id, topic_id))
+
     def was_interrupted(self, chat_id: int) -> bool:
         """Check whether *chat_id* was soft-interrupted since last clear."""
         return chat_id in self._interrupted
diff --git a/ductor_bot/cli/service.py b/ductor_bot/cli/service.py
index ad53ca86..0ab7020f 100644
--- a/ductor_bot/cli/service.py
+++ b/ductor_bot/cli/service.py
@@ -221,7 +221,9 @@ async def execute_streaming(  # noqa: PLR0913
                 timeout_seconds=request.timeout_seconds,
                 timeout_controller=request.timeout_controller,
             ):
-                if self._process_registry.was_aborted(request.chat_id):
+                if self._process_registry.was_aborted(
+                    request.chat_id
+                ) or self._process_registry.was_aborted_topic(request.chat_id, request.topic_id):
                     logger.info("Streaming aborted mid-stream chat=%d", request.chat_id)
                     break
                 text, result = await callbacks.dispatch(event)
@@ -283,7 +285,9 @@ async def _handle_stream_fallback(
         init_session_id: str | None = None,
     ) -> AgentResponse:
         """Handle failed or incomplete streaming: use accumulated text or retry."""
-        was_aborted = self._process_registry.was_aborted(request.chat_id)
+        was_aborted = self._process_registry.was_aborted(
+            request.chat_id
+        ) or self._process_registry.was_aborted_topic(request.chat_id, request.topic_id)
         logger.info(
             "Stream fallback: aborted=%s accumulated=%d init_sid=%s",
             was_aborted,
diff --git a/ductor_bot/messenger/telegram/handlers.py b/ductor_bot/messenger/telegram/handlers.py
index f87798db..bd3118e8 100644
--- a/ductor_bot/messenger/telegram/handlers.py
+++ b/ductor_bot/messenger/telegram/handlers.py
@@ -60,15 +60,16 @@ async def handle_abort(
     chat_id: int,
     message: Message,
 ) -> bool:
-    """Kill active CLI processes and send feedback.
+    """Kill active CLI processes in the current topic and send feedback.
 
     Returns True if handled, False if orchestrator not ready.
     """
     if orchestrator is None:
         return False
 
-    killed = await orchestrator.abort(chat_id)
-    logger.info("Abort requested killed=%d", killed)
+    thread_id = get_thread_id(message)
+    killed = await orchestrator.abort(chat_id, topic_id=thread_id)
+    logger.info("Abort requested chat=%d topic=%s killed=%d", chat_id, thread_id, killed)
     text = stop_text(bool(killed), orchestrator.active_provider_name)
     await send_rich(
         bot,
diff --git a/ductor_bot/orchestrator/core.py b/ductor_bot/orchestrator/core.py
index 7bab3ae3..832e74d3 100644
--- a/ductor_bot/orchestrator/core.py
+++ b/ductor_bot/orchestrator/core.py
@@ -326,6 +326,7 @@ async def handle_message_streaming(  # noqa: PLR0913
 
     async def _handle_message_impl(self, dispatch: _MessageDispatch) -> OrchestratorResult:
         self._process_registry.clear_abort(dispatch.key.chat_id)
+        self._process_registry.clear_topic_abort(dispatch.key.chat_id, dispatch.key.topic_id)
         logger.info("Message received text=%s", dispatch.cmd[:80])
 
         patterns = detect_suspicious_patterns(dispatch.text)
@@ -464,8 +465,22 @@ async def reset_active_provider_session(self, key: SessionKey) -> str:
         logger.info("Active provider session reset provider=%s model=%s", provider, model)
         return provider
 
-    async def abort(self, chat_id: int) -> int:
-        """Kill all active CLI processes and background tasks for chat_id."""
+    async def abort(self, chat_id: int, topic_id: int | None = None) -> int:
+        """Kill active CLI processes for *chat_id* (optionally scoped to *topic_id*).
+
+        When ``topic_id`` is provided (``/stop`` from a specific topic),
+        only the foreground CLI processes registered under that
+        ``(chat_id, topic_id)`` pair are killed. Background tasks and
+        named sessions are left alone — they are not topic-tagged in
+        the current model and have their own management surfaces
+        (``/tasks``, ``/sessions``) so /stop should not double up.
+
+        When ``topic_id`` is ``None`` (legacy callers / ``/stop_all``)
+        the chat-wide sweep runs as before: every process for the chat
+        plus every background task and named session.
+        """
+        if topic_id is not None:
+            return await self._process_registry.kill_by_chat_topic(chat_id, topic_id)
         killed = await self._process_registry.kill_all(chat_id)
         if self._observers.background:
             killed += await self._observers.background.cancel_all(chat_id)
diff --git a/ductor_bot/orchestrator/flows.py b/ductor_bot/orchestrator/flows.py
index d1f041e9..a8859e9a 100644
--- a/ductor_bot/orchestrator/flows.py
+++ b/ductor_bot/orchestrator/flows.py
@@ -333,6 +333,7 @@ async def _maybe_recover_session(  # noqa: PLR0913
     _reg = orch._process_registry
     if (
         _reg.was_aborted(key.chat_id)
+        or _reg.was_aborted_topic(key.chat_id, key.topic_id)
         or _reg.was_interrupted(key.chat_id)
         or not _needs_session_recovery(response)
     ):
@@ -487,7 +488,11 @@ async def normal(  # noqa: PLR0911
         request, session, response = outcome.request, outcome.session, outcome.response
         session_recovered = outcome.session_recovered
         _reg = orch._process_registry
-        if _reg.was_aborted(key.chat_id) or _reg.was_interrupted(key.chat_id):
+        if (
+            _reg.was_aborted(key.chat_id)
+            or _reg.was_aborted_topic(key.chat_id, key.topic_id)
+            or _reg.was_interrupted(key.chat_id)
+        ):
             _reg.clear_interrupt(key.chat_id)
             await _preserve_session_from_response(orch, session, response, reason="abort")
             logger.info("Normal flow aborted/interrupted by user")
@@ -567,7 +572,11 @@ async def _on_compact() -> None:
             return outcome.failed_result
         request, session, response = outcome.request, outcome.session, outcome.response
         _reg = orch._process_registry
-        if _reg.was_aborted(key.chat_id) or _reg.was_interrupted(key.chat_id):
+        if (
+            _reg.was_aborted(key.chat_id)
+            or _reg.was_aborted_topic(key.chat_id, key.topic_id)
+            or _reg.was_interrupted(key.chat_id)
+        ):
             _reg.clear_interrupt(key.chat_id)
             await _preserve_session_from_response(orch, session, response, reason="abort")
             logger.info("Streaming flow aborted/interrupted by user")
@@ -735,7 +744,11 @@ async def named_session_flow(
     response = await orch._cli_service.execute(request)
 
     _reg = orch._process_registry
-    if _reg.was_aborted(key.chat_id) or _reg.was_interrupted(key.chat_id):
+    if (
+        _reg.was_aborted(key.chat_id)
+        or _reg.was_aborted_topic(key.chat_id, key.topic_id)
+        or _reg.was_interrupted(key.chat_id)
+    ):
         _reg.clear_interrupt(key.chat_id)
         ns.status = "idle"
         return OrchestratorResult(text="")
@@ -799,7 +812,11 @@ async def _tagged_text_delta(chunk: str) -> None:
     )
 
     _reg2 = orch._process_registry
-    if _reg2.was_aborted(key.chat_id) or _reg2.was_interrupted(key.chat_id):
+    if (
+        _reg2.was_aborted(key.chat_id)
+        or _reg2.was_aborted_topic(key.chat_id, key.topic_id)
+        or _reg2.was_interrupted(key.chat_id)
+    ):
         _reg2.clear_interrupt(key.chat_id)
         ns.status = "idle"
         return OrchestratorResult(text="")
diff --git a/tests/cli/test_process_registry.py b/tests/cli/test_process_registry.py
index ff5725c8..20c3117a 100644
--- a/tests/cli/test_process_registry.py
+++ b/tests/cli/test_process_registry.py
@@ -179,6 +179,64 @@ def test_has_active_topic_id_ignores_exited() -> None:
     assert reg.has_active(1, topic_id=20) is True
 
 
+class TestKillByChatTopicAbortMarker:
+    """Topic-scoped /stop marker behavior."""
+
+    async def test_sets_topic_abort_marker(self) -> None:
+        reg = ProcessRegistry()
+        proc = _mock_process(pid=80)
+        reg.register(chat_id=1, process=proc, label="main", topic_id=10)
+
+        with patch(
+            "ductor_bot.cli.process_registry._kill_processes",
+            new_callable=AsyncMock,
+            return_value=1,
+        ):
+            killed = await reg.kill_by_chat_topic(1, 10)
+
+        assert killed == 1
+        assert reg.was_aborted_topic(1, 10) is True
+        assert reg.was_aborted(1) is False
+
+    async def test_no_kill_no_marker(self) -> None:
+        reg = ProcessRegistry()
+        proc = _mock_process(pid=81)
+        reg.register(chat_id=1, process=proc, label="main", topic_id=10)
+
+        killed = await reg.kill_by_chat_topic(1, 20)
+
+        assert killed == 0
+        assert reg.was_aborted_topic(1, 20) is False
+        assert reg.was_aborted_topic(1, 10) is False
+
+    def test_clear_topic_abort_removes_marker(self) -> None:
+        reg = ProcessRegistry()
+        reg._aborted_topics.add((1, 10))
+
+        assert reg.was_aborted_topic(1, 10) is True
+        reg.clear_topic_abort(1, 10)
+        assert reg.was_aborted_topic(1, 10) is False
+
+    async def test_topic_a_kill_does_not_kill_topic_b(self) -> None:
+        reg = ProcessRegistry()
+        proc_a = _mock_process(pid=82)
+        proc_b = _mock_process(pid=83)
+        reg.register(chat_id=1, process=proc_a, label="main", topic_id=10)
+        reg.register(chat_id=1, process=proc_b, label="main", topic_id=20)
+
+        with patch(
+            "ductor_bot.cli.process_registry._kill_processes",
+            new_callable=AsyncMock,
+            return_value=1,
+        ):
+            killed = await reg.kill_by_chat_topic(1, 10)
+
+        assert killed == 1
+        assert reg.has_active(1, topic_id=10) is False
+        assert reg.has_active(1, topic_id=20) is True
+        assert proc_b.returncode is None
+
+
 async def test_kill_stale_handles_already_exited() -> None:
     reg = ProcessRegistry()
     proc = _mock_process(pid=40, returncode=0)
diff --git a/tests/messenger/telegram/test_handlers.py b/tests/messenger/telegram/test_handlers.py
index cde12329..52e4016b 100644
--- a/tests/messenger/telegram/test_handlers.py
+++ b/tests/messenger/telegram/test_handlers.py
@@ -50,7 +50,7 @@ async def test_abort_kills_processes_and_replies(self) -> None:
         msg = _make_message(chat_id=42)
         result = await handle_abort(orchestrator, bot, chat_id=42, message=msg)
         assert result is True
-        orchestrator.abort.assert_called_once_with(42)
+        orchestrator.abort.assert_called_once_with(42, topic_id=None)
 
     async def test_abort_no_orchestrator(self) -> None:
         from ductor_bot.messenger.telegram.handlers import handle_abort
@@ -187,6 +187,19 @@ def test_none_username(self) -> None:
 class TestForumTopicPropagation:
     """Test that handlers extract and propagate thread_id."""
 
+    @patch("ductor_bot.messenger.telegram.handlers.send_rich", new_callable=AsyncMock)
+    async def test_abort_entrypoint_passes_topic_id(self, _mock_send: AsyncMock) -> None:
+        from ductor_bot.messenger.telegram.handlers import handle_abort
+
+        orchestrator = MagicMock()
+        orchestrator.abort = AsyncMock(return_value=1)
+        orchestrator.active_provider_name = "claude"
+        bot = MagicMock()
+        msg = _make_message(chat_id=42, topic_thread_id=99)
+
+        await handle_abort(orchestrator, bot, chat_id=42, message=msg)
+        orchestrator.abort.assert_called_once_with(42, topic_id=99)
+
     @patch("ductor_bot.messenger.telegram.handlers.send_rich", new_callable=AsyncMock)
     async def test_handle_abort_passes_thread_id(self, mock_send: AsyncMock) -> None:
         from ductor_bot.messenger.telegram.handlers import handle_abort
diff --git a/tests/orchestrator/test_flows.py b/tests/orchestrator/test_flows.py
index 9072ef64..bdac98b9 100644
--- a/tests/orchestrator/test_flows.py
+++ b/tests/orchestrator/test_flows.py
@@ -14,6 +14,7 @@
     _finish_normal,
     _strip_ack_token,
     _update_session,
+    named_session_flow,
     normal,
     normal_streaming,
 )
@@ -697,6 +698,20 @@ async def test_normal_abort_skips_retry(orch: Orchestrator) -> None:
     assert mock_execute.call_count == 1  # No retry
 
 
+async def test_topic_abort_skips_recovery(orch: Orchestrator) -> None:
+    """Topic-scoped /stop returns empty instead of session recovery."""
+    key = SessionKey(chat_id=1, topic_id=42)
+    mock_execute = AsyncMock(
+        return_value=_mock_response(is_error=True, result="killed", returncode=-9),
+    )
+    object.__setattr__(orch._cli_service, "execute", mock_execute)
+    orch._process_registry._aborted_topics.add((1, 42))
+
+    result = await normal(orch, key, "Hello")
+    assert result.text == ""
+    assert mock_execute.call_count == 1
+
+
 async def test_streaming_abort_skips_retry(orch: Orchestrator) -> None:
     """When process is aborted (via /stop), normal_streaming() returns empty instead of retrying."""
     mock_exec = AsyncMock(return_value=_mock_response())
@@ -726,6 +741,19 @@ async def test_normal_abort_discards_successful_response(orch: Orchestrator) ->
     assert result.text == ""
 
 
+async def test_named_session_topic_abort(orch: Orchestrator) -> None:
+    """Named-session follow-up honors topic-scoped abort markers."""
+    ns = orch._named_sessions.create(1, "claude", "opus", "Setup")
+    orch._named_sessions.update_after_response(1, ns.name, "sess-named")
+    mock_execute = AsyncMock(return_value=_mock_response(result="Agent replied"))
+    object.__setattr__(orch._cli_service, "execute", mock_execute)
+    orch._process_registry._aborted_topics.add((1, 42))
+
+    result = await named_session_flow(orch, SessionKey(chat_id=1, topic_id=42), ns.name, "Hello")
+    assert result.text == ""
+    assert ns.status == "idle"
+
+
 async def test_streaming_abort_discards_successful_response(orch: Orchestrator) -> None:
     """Even when streaming CLI responds successfully, abort flag causes empty result."""
     mock_streaming = AsyncMock(