fix(agent): suppress subdirectory hint truncation warning

agent/prompt_builder.py

@@ -1422,10 +1422,11 @@ def _build_skills_system_prompt_inner(
 
 def _truncate_content(
     content: str, filename: str, max_chars: Optional[int] = None, context_length: Optional[int] = None,
-    read_path: Optional[str] = None,
+    read_path: Optional[str] = None, queue_warning: bool = True,
 ) -> str:
     """Head/tail truncation with a marker in the middle; ``read_path`` (default ``filename``) is what the
-    agent is told to ``read_file`` to recover the full content."""
+    agent is told to ``read_file`` to recover the full content. ``queue_warning`` controls whether startup
+    context-file callers surface the truncation through the chat warning queue."""
     if max_chars is None:
         max_chars = _get_context_file_max_chars(context_length)
     if len(content) <= max_chars:
@@ -1435,9 +1436,10 @@ def _truncate_content(
         f"trim the file, pin a larger context_file_max_chars, or use a larger-context model!"
     )
     logger.warning(msg)
-    if (warnings := _truncation_warnings.get()) is None:
-        _truncation_warnings.set(warnings := [])
-    warnings.append(msg)
+    if queue_warning:
+        if (warnings := _truncation_warnings.get()) is None:
+            _truncation_warnings.set(warnings := [])
+        warnings.append(msg)
     head_chars = int(max_chars * CONTEXT_TRUNCATE_HEAD_RATIO)
     tail_chars = int(max_chars * CONTEXT_TRUNCATE_TAIL_RATIO)
     marker = (

agent/subdirectory_hints.py

@@ -214,7 +214,9 @@ class SubdirectoryHintTracker:
                 # Same security scan as startup context loading.
                 content = _scan_context_content(content, filename)
                 rel_path = self._display_path(hint_path)
-                content = _truncate_content(content, filename, max_chars=_MAX_HINT_CHARS, read_path=rel_path)
+                content = _truncate_content(
+                    content, filename, max_chars=_MAX_HINT_CHARS, read_path=rel_path, queue_warning=False,
+                )
                 logger.debug("Loaded subdirectory hints from %s: %s", directory, [rel_path])
                 return f"[Subdirectory context discovered: {rel_path}]\n{content}"  # first match wins per directory
             except Exception as exc:

tests/agent/test_subdirectory_hints.py

@@ -7,6 +7,7 @@ from pathlib import Path
 from unittest.mock import patch
 
 from agent.search_policy import SEARCH_PRUNE_DIR_NAMES
+from agent.prompt_builder import drain_truncation_warnings
 from agent.subdirectory_hints import SubdirectoryHintTracker
 
 
@@ -135,6 +136,22 @@ class TestSubdirectoryHintTracker:
         assert len(result) < len(body)
         assert any("TRUNCATED" in r.message and "AGENTS.md" in r.message for r in caplog.records)
 
+    def test_truncation_of_large_hints_does_not_queue_context_file_warning(self, tmp_path):
+        """Hint previews retain their marker without surfacing a startup-context warning in chat (#111772)."""
+        from agent import subdirectory_hints as sh
+
+        drain_truncation_warnings()
+        sub = tmp_path / "bigdir"
+        sub.mkdir()
+        (sub / "AGENTS.md").write_text("x" * (sh._MAX_HINT_CHARS + 1), encoding="utf-8")
+
+        tracker = SubdirectoryHintTracker(working_dir=str(tmp_path))
+        result = tracker.check_tool_call("read_file", {"path": str(sub / "file.py")})
+
+        assert result is not None
+        assert "truncated AGENTS.md" in result
+        assert drain_truncation_warnings() == []
+
     def test_area_file_under_ceiling_is_delivered_whole(self, tmp_path):
         """An area AGENTS.md sized like ours (well under the ceiling) arrives intact — no marker."""
         sub = tmp_path / "gateway"