refactor(blocks): align subagent output methods with peer guards, add cap test

Author: elkaix

src/pythinker_code/ui/shell/visualize/_blocks.py

@@ -518,6 +518,8 @@ def set_subagent_metadata(self, agent_id: str, subagent_type: str) -> None:
     def mark_sub_execution_started(self, tool_call_id: str) -> None:
         if tool_call_id not in self._ongoing_subagent_tool_calls:
             return
+        if tool_call_id in self._subagent_execution_started:
+            return
         self._subagent_execution_started.add(tool_call_id)
         self._renderable = self._compose()
 
@@ -526,6 +528,8 @@ def append_sub_output_part(
     ) -> None:
         if tool_call_id not in self._ongoing_subagent_tool_calls:
             return
+        if not text:
+            return
         parts = self._subagent_output_parts.setdefault(tool_call_id, [])
         parts.append(text)
         if stream == "stderr":

tests/ui_and_conv/test_tool_call_block.py

@@ -199,6 +199,16 @@ def test_append_sub_output_part_caps_buffer_at_200_chars():
     assert len(combined) <= 200
 
 
+def test_append_sub_output_part_caps_buffer_across_multiple_appends():
+    block = _ToolCallBlock(_tool_call("Agent", '{"description":"scan"}'))
+    call = _tool_call_with_id("sub-1", "Bash", '{"command":"ls"}')
+    block.append_sub_tool_call(call)
+    for _ in range(30):
+        block.append_sub_output_part("sub-1", "x" * 10)  # 300 chars total, 10 at a time
+    combined = "".join(block._subagent_output_parts["sub-1"])
+    assert len(combined) <= 200
+
+
 def test_append_sub_output_part_tracks_stderr():
     block = _ToolCallBlock(_tool_call("Agent", '{"description":"scan"}'))
     call = _tool_call_with_id("sub-1", "Bash", '{"command":"cat missing"}')
@@ -222,9 +232,6 @@ def test_mark_sub_execution_started_discards_unknown_id():
 
 
 def test_finish_sub_tool_call_cleans_up_output_state():
-    from pythinker_code.wire.types import ToolResult
-    from pythinker_core.tooling import ToolOk
-
     block = _ToolCallBlock(_tool_call("Agent", '{"description":"scan"}'))
     call = _tool_call_with_id("sub-1", "Bash", '{"command":"ls"}')
     block.append_sub_tool_call(call)