diff --git a/mcp-servers/navi-3d/app/mcp_server.py b/mcp-servers/navi-3d/app/mcp_server.py
index 508e3ab..d5793b1 100644
--- a/mcp-servers/navi-3d/app/mcp_server.py
+++ b/mcp-servers/navi-3d/app/mcp_server.py
@@ -46,35 +46,35 @@
 
 
 @mcp.tool(name="compile_scad")
-def compile_scad_tool(
+async def compile_scad_tool(
     session_id: Annotated[str, Field(description="Navi session ID — files are resolved inside session_files/<session_id>/.")],
     source_path: Annotated[str, Field(description="Relative or absolute path to the .scad file.")],
     output_path: Annotated[str, Field(description="Relative or absolute path for the output STL.")],
 ) -> str:
     """Compile an OpenSCAD script into a binary STL."""
-    result = compile_scad(_settings(), session_id, source_path, output_path)
+    result = await compile_scad(_settings(), session_id, source_path, output_path)
     return _json(result)
 
 
 @mcp.tool(name="render_stl")
-def render_stl_tool(
+async def render_stl_tool(
     session_id: Annotated[str, Field(description="Navi session ID — files are resolved inside session_files/<session_id>/.")],
     source_path: Annotated[str, Field(description="Path to the STL file to render.")],
     views: Annotated[list[str] | None, Field(description="Camera views: front, back, top, bottom, left, right, iso. Max 3.")] = None,
 ) -> str:
     """Render preview PNG images from an STL file."""
-    result = render_stl(_settings(), session_id, source_path, views or ["iso"])
+    result = await render_stl(_settings(), session_id, source_path, views or ["iso"])
     return _json(result)
 
 
 @mcp.tool(name="lint_scad")
-def lint_scad_tool(
+async def lint_scad_tool(
     session_id: Annotated[str, Field(description="Navi session ID — files are resolved inside session_files/<session_id>/.")],
     source_path: Annotated[str, Field(description="Path to the .scad file.")],
     strict: Annotated[bool, Field(description="Treat warnings as errors.")] = False,
 ) -> str:
     """Lint an OpenSCAD source file before compiling."""
-    result = lint_scad(_settings(), session_id, source_path, strict)
+    result = await lint_scad(_settings(), session_id, source_path, strict)
     return _json(result)