fix: separate Laguna bridge turns after clean stops

renderers/laguna_xs2.py

@@ -421,6 +421,7 @@ def bridge_to_next_turn(
         # ``</assistant>\n`` — the same scaffold the template emits.
         previous_ids = list(previous_prompt_ids) + list(previous_completion_ids)
         stop_ids = {self._assistant_end, self._eos}
+        needs_separator = previous_ids[-1] in stop_ids
         if (
             not previous_ids[len(previous_prompt_ids) :]
             or previous_ids[-1] not in stop_ids
@@ -478,6 +479,9 @@ def emit_text_segments(
                 ext_sampled.append(is_sampled)
                 ext_content.append(is_content)
 
+        if needs_separator:
+            emit_text("\n", -1)
+
         for i, msg in enumerate(new_messages):
             role = msg.get("role")
             content = self._visible_text(msg.get("content"))

tests/test_bridge.py

@@ -140,6 +140,32 @@ def test_bridge_extends_prev_verbatim_on_clean_stop(br_renderer_all, br_model):
     )
 
 
+@pytest.mark.model
+@pytest.mark.parametrize("model", ["poolside/Laguna-XS.2", "poolside/Laguna-M.1"])
+@pytest.mark.parametrize("stop", ["</assistant>", "〈|EOS|〉", ""])
+@pytest.mark.parametrize(
+    "role,opening", [("user", "<user>"), ("tool", "<tool_response>")]
+)
+def test_laguna_bridge_separates_turns(model, stop, role, opening):
+    from renderers import create_renderer
+
+    tok, _ = _load(model, "auto")
+    native = create_renderer(tok, chat_template_kwargs={"enable_thinking": False})
+    prompt = native.render_ids(
+        [{"role": "user", "content": "Hi."}], add_generation_prompt=True
+    )
+    completion = tok.encode("\nFour." + stop, add_special_tokens=False)
+    bridge = native.bridge_to_next_turn(
+        prompt, completion, [{"role": role, "content": "Next."}]
+    )
+    assert bridge is not None
+    previous = prompt + completion
+    assert bridge.token_ids[: len(previous)] == previous
+    extension = tok.decode(bridge.token_ids[len(previous) :], skip_special_tokens=False)
+    close = "" if stop else "</assistant>"
+    assert extension.startswith(close + "\n" + opening + "\n")
+
+
 def test_bridge_rejects_assistant_in_extension(br_renderer):
     prev_prompt, prev_completion = _simulate_prior_turn(br_renderer)
     assert (