@@ -7,7 +7,6 @@
 from typing import List, Tuple
 import logging
 import tiktoken
-import traceback
 
 
 logger = logging.getLogger(__name__)
@@ -29,10 +28,12 @@ def set_main_loop(loop: asyncio.AbstractEventLoop) -> None:
     _main_loop = loop
     _main_loop_thread_ident = threading.get_ident()
 
+
 # ------------------------------------------------------------
 # ---------------------- Complexity Check --------------------
 # ------------------------------------------------------------
 
+
 def is_complex_module(components: dict[str, any], core_component_ids: list[str]) -> bool:
     files = set()
     for component_id in core_component_ids:
@@ -50,6 +51,7 @@ def is_complex_module(components: dict[str, any], core_component_ids: list[str])
 
 enc = tiktoken.encoding_for_model("gpt-4")
 
+
 def count_tokens(text: str) -> int:
     """
     Count the number of tokens in a text.
@@ -63,10 +65,11 @@ def count_tokens(text: str) -> int:
 # ---------------------- Mermaid Validation -----------------
 # ------------------------------------------------------------
 
+
 async def validate_mermaid_diagrams(md_file_path: str, relative_path: str) -> str:
     """
     Validate all Mermaid diagrams in a markdown file.
-    
+
     Args:
         md_file_path: Path to the markdown file to check
         relative_path: Relative path to the markdown file
@@ -80,68 +83,70 @@ async def validate_mermaid_diagrams(md_file_path: str, relative_path: str) -> st
         file_path = Path(md_file_path)
         if not file_path.exists():
             return f"Error: File '{md_file_path}' does not exist"
-        
-        content = file_path.read_text(encoding='utf-8')
-        
+
+        content = file_path.read_text(encoding="utf-8")
+
         # Extract all mermaid code blocks
         mermaid_blocks = extract_mermaid_blocks(content)
-        
+
         if not mermaid_blocks:
             return "No mermaid diagrams found in the file"
-        
+
         # Validate each mermaid diagram sequentially to avoid segfaults
         errors = []
         for i, (line_start, diagram_content) in enumerate(mermaid_blocks, 1):
             error_msg = await validate_single_diagram(diagram_content, i, line_start)
             if error_msg:
                 errors.append("\n")
                 errors.append(error_msg)
-        
+
         # if errors:
         #     logger.debug(f"Mermaid syntax errors found in file: {md_file_path}: {errors}")
-        
+
         if errors:
-            return "Mermaid syntax errors found in file: " + relative_path + "\n" + "\n".join(errors)
+            return (
+                "Mermaid syntax errors found in file: " + relative_path + "\n" + "\n".join(errors)
+            )
         else:
             return "All mermaid diagrams in file: " + relative_path + " are syntax correct"
-            
+
     except Exception as e:
         return f"Error processing file: {str(e)}"
 
 
 def extract_mermaid_blocks(content: str) -> List[Tuple[int, str]]:
     """
     Extract all mermaid code blocks from markdown content.
-    
+
     Returns:
         List of tuples containing (line_number, diagram_content)
     """
     mermaid_blocks = []
-    lines = content.split('\n')
+    lines = content.split("\n")
     i = 0
-    
+
     while i < len(lines):
         line = lines[i].strip()
-        
+
         # Look for mermaid code block start
-        if line == '```mermaid' or line.startswith('```mermaid'):
+        if line == "```mermaid" or line.startswith("```mermaid"):
             start_line = i + 1
             diagram_lines = []
             i += 1
-            
+
             # Collect lines until we find the closing ```
             while i < len(lines):
-                if lines[i].strip() == '```':
+                if lines[i].strip() == "```":
                     break
                 diagram_lines.append(lines[i])
                 i += 1
-            
+
             if diagram_lines:  # Only add non-empty diagrams
-                diagram_content = '\n'.join(diagram_lines)
+                diagram_content = "\n".join(diagram_lines)
                 mermaid_blocks.append((start_line, diagram_content))
-        
+
         i += 1
-    
+
     return mermaid_blocks
 
 
@@ -154,9 +159,10 @@ def extract_mermaid_blocks(content: str) -> List[Tuple[int, str]]:
 # mermaid-py validates diagrams by sending them to a remote rendering service
 # (https://mermaid.ink by default, overridable via the MERMAID_INK_SERVER env
 # var understood by mermaid-py itself) rather than spawning a local Node.js
-# subprocess. It can still hang or fail when that service is unreachable
-# (no network egress, DNS/firewall issues, or an outage). Enabled by default;
-# set MERMAID_VALIDATE=0 to disable.
+# subprocess. Note that this sends diagram content to that third-party service.
+# It can still hang or fail when the service is unreachable (no network egress,
+# DNS/firewall issues, or an outage). Enabled by default; set MERMAID_VALIDATE=0
+# to disable.
 _MERMAID_PY_BROKEN = os.environ.get("MERMAID_VALIDATE", "1") == "0"
 _MERMAID_PY_PROBED = True  # Skip probing — rely on env var
 
@@ -181,16 +187,14 @@ async def _try_pythonmonkey_parse(diagram_content: str) -> str | None:
         return None
 
     old_stderr = sys.stderr
-    sys.stderr = open(os.devnull, 'w')
+    sys.stderr = open(os.devnull, "w")
     try:
         if (
             _main_loop is not None
             and _main_loop.is_running()
             and threading.get_ident() != _main_loop_thread_ident
         ):
-            fut = asyncio.run_coroutine_threadsafe(
-                parse_mermaid_py(diagram_content), _main_loop
-            )
+            fut = asyncio.run_coroutine_threadsafe(parse_mermaid_py(diagram_content), _main_loop)
             await asyncio.wrap_future(fut)
         else:
             await parse_mermaid_py(diagram_content)
@@ -221,6 +225,7 @@ def _parse_via_mermaid_py(diagram_content: str) -> str:
     text, otherwise a successful SVG gets reported as a parse error.
     """
     import mermaid as md
+
     try:
         md.Mermaid(diagram_content)
         return ""
@@ -247,7 +252,9 @@ async def validate_single_diagram(diagram_content: str, diagram_num: int, line_s
             # Validation disabled/unavailable is not a syntax error — a
             # non-empty return here would make callers report valid diagrams
             # as broken and send agents into fix loops.
-            logger.debug("Diagram %d: validation skipped (mermaid-py disabled or unavailable)", diagram_num)
+            logger.debug(
+                "Diagram %d: validation skipped (mermaid-py disabled or unavailable)", diagram_num
+            )
             return ""
         try:
             core_error = await asyncio.wait_for(
@@ -257,28 +264,32 @@ async def validate_single_diagram(diagram_content: str, diagram_num: int, line_s
         except asyncio.TimeoutError:
             # Inconclusive, not a parse failure. Latch so the remaining
             # diagrams (and later calls) don't each block 15s on the same
-            # broken Node.js setup.
+            # unreachable rendering service.
             _MERMAID_PY_BROKEN = True
-            logger.warning("Diagram %d: mermaid validation timed out (15s); skipping further validation", diagram_num)
+            logger.warning(
+                "Diagram %d: mermaid validation timed out (15s); skipping further validation",
+                diagram_num,
+            )
             return ""
         except Exception as e:
             return f"  Diagram {diagram_num}: Exception during validation - {str(e)}"
 
     if not core_error:
         return ""
 
-    line_match = re.search(r'line (\d+)', core_error)
+    line_match = re.search(r"line (\d+)", core_error)
     if line_match:
         error_line_in_diagram = int(line_match.group(1))
         actual_line_in_file = line_start + error_line_in_diagram
-        newline = '\n'
+        newline = "\n"
         return f"Diagram {diagram_num}: Parse error on line {actual_line_in_file}:{newline}{newline.join(core_error.split(newline)[1:])}"
     return f"Diagram {diagram_num}: {core_error}"
 
 
 if __name__ == "__main__":
     # Test with the provided file
     import asyncio
+
     test_file = "output/docs/SWE_agent-docs/agent_hooks.md"
     result = asyncio.run(validate_mermaid_diagrams(test_file, "agent_hooks.md"))
-    print(result)
+    print(result)
@@ -64,11 +64,10 @@ dependencies = [
 ]
 
 [external]
-# NOTE: mermaid-py (>=0.8.0, the version pinned below) validates diagrams via
-# an HTTP call to a remote rendering service (mermaid.ink by default), not a
-# local Node.js process -- this nodejs requirement may no longer be needed for
-# that purpose specifically; kept as-is pending confirmation it isn't used
-# elsewhere.
+# Node.js/npm are required at *install* time by PythonMonkey (pulled in via
+# mermaid-parser-py), whose pminit helper shells out to npm to populate its JS
+# dependencies. mermaid-py itself does not need Node.js: it validates diagrams
+# with an HTTP call to a remote rendering service (mermaid.ink by default).
 build-requires = [
     { name = "nodejs", version = ">=14.0.0" }
 ]
@@ -131,6 +130,11 @@ disallow_incomplete_defs = false
 line-length = 100
 target-version = "py312"
 
+[tool.ruff.lint]
+# ruff 0.16 widened its default rule set considerably; pin the previous
+# defaults so an unpinned `pip install ruff` in CI stays stable.
+select = ["E4", "E7", "E9", "F"]
+
 [tool.pytest.ini_options]
 testpaths = ["tests"]
 norecursedirs = [".venv", "atlascloud", "titan-sight"]