Cap import_netlist inline response size for large netlists

Netlists exceeding INLINE_RESULT_THRESHOLD (20 nets) now return a
compact summary with the top nets by connection count as a preview.
Full data is always written to the sidecar JSON file. Small netlists
still return everything inline.

src/mckicad/tools/netlist.py

@@ -15,6 +15,7 @@ import re
 from typing import Any
 import xml.etree.ElementTree as ET
 
+from mckicad.config import INLINE_RESULT_THRESHOLD
 from mckicad.server import mcp
 from mckicad.utils.file_utils import write_detail_file
 
@@ -405,14 +406,7 @@ def import_netlist(
         stats["net_count"], stats["component_count"], stats["connection_count"],
     )
 
-    result: dict[str, Any] = {
+    # Write full parsed data to output JSON (always — this is the complete data)
-        "success": True,
-        "format_detected": fmt,
-        "source_path": source_path,
-        **parsed,
-    }
-
-    # Write output JSON
     if output_path:
         out = os.path.abspath(os.path.expanduser(output_path))
         os.makedirs(os.path.dirname(out) or ".", exist_ok=True)
@@ -423,6 +417,31 @@ def import_netlist(
             source_path, "imported_netlist.json", parsed,
         )
 
-    result["output_path"] = out
+    result: dict[str, Any] = {
+        "success": True,
+        "format_detected": fmt,
+        "source_path": source_path,
+        "output_path": out,
+        "statistics": stats,
+    }
+
+    nets = parsed["nets"]
+    if stats["net_count"] <= INLINE_RESULT_THRESHOLD:
+        # Small netlist — return everything inline
+        result["nets"] = nets
+        result["components"] = parsed["components"]
+        if "pin_metadata" in parsed:
+            result["pin_metadata"] = parsed["pin_metadata"]
+    else:
+        # Large netlist — compact summary inline, full data in output file
+        # Sort nets by connection count (most connected first) for useful preview
+        sorted_nets = sorted(nets.items(), key=lambda kv: len(kv[1]), reverse=True)
+        result["nets_preview"] = dict(sorted_nets[:INLINE_RESULT_THRESHOLD])
+        result["nets_preview_note"] = (
+            f"Showing top {INLINE_RESULT_THRESHOLD} of {stats['net_count']} nets "
+            f"by connection count. Full data in output_path."
+        )
+        # Include component count but not full component dict
+        result["component_refs"] = sorted(parsed["components"].keys())
 
     return result

tests/test_netlist.py

@@ -430,3 +430,83 @@ class TestOutputFile:
         assert result["success"] is True
         assert "output_path" in result
         assert os.path.isfile(result["output_path"])
+
+    def test_large_netlist_returns_preview(self, tmp_output_dir):
+        """Netlists exceeding INLINE_RESULT_THRESHOLD return a preview, not full data."""
+        from mckicad.config import INLINE_RESULT_THRESHOLD
+        from mckicad.tools.netlist import import_netlist
+
+        # Generate a netlist with more nets than the threshold
+        net_count = INLINE_RESULT_THRESHOLD + 5
+        net_lines = []
+        comp_lines = []
+        refs_seen: set[str] = set()
+        for i in range(1, net_count + 1):
+            ref_a = f"R{i}"
+            ref_b = f"C{i}"
+            comp_lines.append(f'<comp ref="{ref_a}"><value>{i}k</value></comp>')
+            comp_lines.append(f'<comp ref="{ref_b}"><value>{i}00nF</value></comp>')
+            refs_seen.update([ref_a, ref_b])
+            net_lines.append(
+                f'<net code="{i}" name="NET{i}">'
+                f'<node ref="{ref_a}" pin="1"/>'
+                f'<node ref="{ref_b}" pin="2"/>'
+                f'</net>'
+            )
+
+        xml = (
+            '<export version="D"><components>'
+            + "".join(comp_lines)
+            + "</components><nets>"
+            + "".join(net_lines)
+            + "</nets></export>"
+        )
+        src = os.path.join(tmp_output_dir, "large.xml")
+        with open(src, "w") as f:
+            f.write(xml)
+
+        result = import_netlist(source_path=src)
+        assert result["success"] is True
+        assert result["statistics"]["net_count"] == net_count
+
+        # Should NOT have full nets inline
+        assert "nets" not in result
+        # Should have preview
+        assert "nets_preview" in result
+        assert len(result["nets_preview"]) == INLINE_RESULT_THRESHOLD
+        assert "nets_preview_note" in result
+
+        # Should have component refs list instead of full component dict
+        assert "component_refs" in result
+        assert "components" not in result
+
+        # Full data should be in the output file
+        assert os.path.isfile(result["output_path"])
+        with open(result["output_path"]) as f:
+            full_data = json.load(f)
+        assert len(full_data["nets"]) == net_count
+
+    def test_small_netlist_returns_inline(self, tmp_output_dir):
+        """Netlists within INLINE_RESULT_THRESHOLD return full data inline."""
+        from mckicad.tools.netlist import import_netlist
+
+        xml = textwrap.dedent("""\
+            <export version="D">
+              <components><comp ref="R1"><value>1k</value></comp></components>
+              <nets>
+                <net code="1" name="GND"><node ref="R1" pin="2"/></net>
+              </nets>
+            </export>
+        """)
+        src = os.path.join(tmp_output_dir, "small.xml")
+        with open(src, "w") as f:
+            f.write(xml)
+
+        result = import_netlist(source_path=src)
+        assert result["success"] is True
+        # Should have full data inline
+        assert "nets" in result
+        assert "components" in result
+        # Should NOT have preview keys
+        assert "nets_preview" not in result
+        assert "component_refs" not in result