Auto-sync junctions on wire/symbol mutations

Replaces the manual add_schematic_junction tool with automatic junction
management. WireManager.sync_junctions inserts/removes junction dots
based on wire endpoints plus component pin positions and is invoked
after add_wire, add_polyline_wire, delete_wire, move, and rotate.

- Pin-aware: parses lib_symbols and applies KiCad's mirror/rotate/
  translate transform to compute world pin coordinates
- Multi-unit safe: filters lib_symbols sub-units by the placed
  symbol's (unit N) field plus the unit-0 common body
- Removes the now-unused WireManager.add_junction static method
- Updates CHANGELOG [Unreleased] with the tool removal notice
- Adds .mcp.json to .gitignore (machine-local paths)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.gitignore

@@ -89,6 +89,7 @@ Desktop.ini
 
 # Generated local config files (contain machine-specific paths)
 windows-mcp-config.json
+.mcp.json
 
 # Personal notes / local contributions (not for upstream)
 myContribution/

CHANGELOG.md

@@ -1,5 +1,10 @@
 # Changelog
 
+> **⚠️ Research Project — No Stability Guarantees**
+> This is an unstable, experimental research project. APIs, tool names, parameters,
+> and file formats may change at any time without notice. Back-compatibility is
+> explicitly **not** preserved between versions.
+
 All notable changes to the KiCAD MCP Server project are documented here.
 
 ## [Unreleased]
@@ -71,6 +76,14 @@ All notable changes to the KiCAD MCP Server project are documented here.
   no-op removal, special-character escaping, UUID preservation, and the two
   new convenience tools.
 
+### Removed
+
+- `add_schematic_junction` MCP tool has been removed. Junctions are now
+  inserted and removed automatically via `WireManager.sync_junctions` whenever
+  wires are added, deleted, or moved.
+- Junction placement is pin-aware: `sync_junctions` consults component pin
+  positions so that T-junctions at component pins are correctly recognised.
+
 ---
 
 ## [2.2.3] - 2026-03-11

python/commands/wire_manager.py

@@ -32,6 +32,12 @@ _SYM_WIDTH = Symbol("width")
 _SYM_TYPE = Symbol("type")
 _SYM_UUID = Symbol("uuid")
 _SYM_SHEET_INSTANCES = Symbol("sheet_instances")
+_SYM_JUNCTION = Symbol("junction")
+_SYM_LIB_SYMBOLS = Symbol("lib_symbols")
+_SYM_LIB_ID = Symbol("lib_id")
+_SYM_MIRROR = Symbol("mirror")
+_SYM_PIN = Symbol("pin")
+_IU_PER_MM = 10000
 
 
 def _find_insertion_point(content: str) -> int:
@@ -176,6 +182,8 @@ class WireManager:
             sch_data.insert(sheet_instances_index, wire_sexp)
             logger.info(f"Injected wire from {start_point} to {end_point}")
 
+            WireManager.sync_junctions(sch_data)
+
             # Write back
             with open(schematic_path, "w", encoding="utf-8") as f:
                 output = sexpdata.dumps(sch_data)
@@ -252,6 +260,8 @@ class WireManager:
                 f"Injected {len(wire_sexps)} wire segments for {len(points)}-point polyline"
             )
 
+            WireManager.sync_junctions(sch_data)
+
             # Write back
             with open(schematic_path, "w", encoding="utf-8") as f:
                 output = sexpdata.dumps(sch_data)
@@ -450,74 +460,266 @@ class WireManager:
         return splits
 
     @staticmethod
-    def add_junction(schematic_path: Path, position: List[float], diameter: float = 0) -> bool:
+    def _collect_wire_endpoints(sch_data: list) -> List[Tuple[float, float]]:
+        """Return all (x, y) endpoints for every wire in sch_data."""
+        endpoints: List[Tuple[float, float]] = []
+        for item in sch_data:
+            parsed = WireManager._parse_wire(item)
+            if parsed is not None:
+                (x1, y1), (x2, y2), _, _ = parsed
+                endpoints.append((x1, y1))
+                endpoints.append((x2, y2))
+        return endpoints
+
+    @staticmethod
+    def _get_existing_junctions(sch_data: list) -> dict:
+        """Return {(iu_x, iu_y): index_in_sch_data} for every junction element."""
+        result: dict = {}
+        for i, item in enumerate(sch_data):
+            if not (isinstance(item, list) and len(item) > 0 and item[0] == _SYM_JUNCTION):
+                continue
+            at_entry = next(
+                (p for p in item[1:] if isinstance(p, list) and len(p) >= 3 and p[0] == _SYM_AT),
+                None,
+            )
+            if at_entry is None:
+                continue
+            x, y = float(at_entry[1]), float(at_entry[2])
+            result[(round(x * _IU_PER_MM), round(y * _IU_PER_MM))] = i
+        return result
+
+    @staticmethod
+    def _make_junction_sexp(x: float, y: float, diameter: float = 0) -> list:
+        return [
+            _SYM_JUNCTION,
+            [_SYM_AT, x, y],
+            [Symbol("diameter"), diameter],
+            [Symbol("color"), 0, 0, 0, 0],
+            [_SYM_UUID, str(uuid.uuid4())],
+        ]
+
+    # Regex to parse sub-unit names like "LM324_2_1" → (base="LM324", unit=2, style=1)
+    # The sub-unit suffix is <base>_<unit>_<style> where unit and style are integers.
+    _SUB_UNIT_RE = re.compile(r"^(.+)_(\d+)_(\d+)$")
+
+    @staticmethod
+    def _parse_lib_pins(sym_def: list, unit: int = 1) -> List[Tuple[float, float]]:
+        """Extract pin local (x, y) positions for *unit* from a lib_symbols symbol definition.
+
+        Only collects pins from sub-unit symbols whose parsed unit number matches *unit*
+        OR is 0 (the "common" body drawn on every unit, e.g. power pins on an op-amp).
+        Sub-units whose unit index is neither *unit* nor 0 are skipped entirely.
+
+        If the lib_symbols entry has no nested (symbol ...) children at all (rare, simple
+        defs), falls back to collecting every (pin ...) directly from the top-level entry.
+
+        Uses a stack instead of recursion to handle nested sub-unit symbols.
         """
-        Add a junction (connection dot) to the schematic.
+        _SYM_SYMBOL = Symbol("symbol")
+        pins: List[Tuple[float, float]] = []
 
-        Mirrors KiCAD's AddJunction behaviour: any wire whose interior passes
-        through *position* is split into two segments at that point so that
-        the BFS-based get_wire_connections tool can traverse the T/X branch.
+        # Separate top-level direct children into sub-unit symbols vs other nodes.
+        sub_units: list = []
+        direct_pins: list = []
+        for child in sym_def[1:]:
+            if not isinstance(child, list) or not child:
+                continue
+            if child[0] == _SYM_SYMBOL:
+                sub_units.append(child)
+            elif child[0] == _SYM_PIN:
+                direct_pins.append(child)
 
-        Args:
-            schematic_path: Path to .kicad_sch file
-            position: [x, y] coordinates for junction
-            diameter: Junction diameter (0 for default)
+        if not sub_units:
+            # Fallback: simple definition with no nested sub-unit symbols — collect all pins.
+            nodes_to_search = direct_pins
+        else:
+            # Filter sub-units by parsed unit number.
+            nodes_to_search = []
+            for sub in sub_units:
+                sub_name = (
+                    sub[1]
+                    if len(sub) > 1 and isinstance(sub[1], str)
+                    else str(sub[1]) if len(sub) > 1 else ""
+                )
+                m = WireManager._SUB_UNIT_RE.match(sub_name)
+                if m:
+                    sub_unit_num = int(m.group(2))
+                    if sub_unit_num == unit or sub_unit_num == 0:
+                        nodes_to_search.extend(sub[1:])
+                else:
+                    # Name doesn't match the expected pattern — include it (fail-safe).
+                    logger.debug(
+                        "lib_symbols sub-unit name %r did not match <base>_<unit>_<style>; "
+                        "including all its pins as fallback",
+                        sub_name,
+                    )
+                    nodes_to_search.extend(sub[1:])
 
-        Returns:
-            True if successful, False otherwise
+        # Walk the selected nodes to collect (pin ...) entries via stack.
+        stack: list = list(nodes_to_search)
+        while stack:
+            node = stack.pop()
+            if not isinstance(node, list) or not node:
+                continue
+            if node[0] == _SYM_PIN:
+                at = next(
+                    (
+                        p
+                        for p in node[1:]
+                        if isinstance(p, list) and len(p) >= 3 and p[0] == _SYM_AT
+                    ),
+                    None,
+                )
+                if at:
+                    pins.append((float(at[1]), float(at[2])))
+                continue  # don't recurse into pin sub-expressions
+            stack.extend(node[1:])
+        return pins
+
+    @staticmethod
+    def _collect_pin_positions(sch_data: list) -> List[Tuple[float, float]]:
+        """Return world (x, y) positions for every placed component pin in sch_data.
+
+        Parses lib_symbols for pin local coordinates (unit-aware), then applies the KiCad
+        transform chain (y-negate → mirror → rotate → translate) to each pin.
         """
-        try:
-            # Read schematic
-            with open(schematic_path, "r", encoding="utf-8") as f:
-                sch_content = f.read()
+        _SYM_UNIT = Symbol("unit")
 
-            sch_data = sexpdata.loads(sch_content)
+        # Build {lib_id: sym_def} from the embedded lib_symbols section.
+        # We defer pin extraction until we know which unit each placed instance uses.
+        lib_sym_defs: dict = {}
+        for item in sch_data:
+            if not (isinstance(item, list) and len(item) > 0 and item[0] == _SYM_LIB_SYMBOLS):
+                continue
+            for sym_def in item[1:]:
+                if not (
+                    isinstance(sym_def, list)
+                    and len(sym_def) > 1
+                    and sym_def[0] == Symbol("symbol")
+                ):
+                    continue
+                lib_id = sym_def[1] if isinstance(sym_def[1], str) else str(sym_def[1])
+                lib_sym_defs[lib_id] = sym_def
+            break
 
-            # Split any wire that passes through the junction as a midpoint
-            # (mirrors KiCAD's AddJunction / BreakSegments behaviour)
-            splits = WireManager._break_wires_at_point(sch_data, position)
-            if splits:
-                logger.info(f"Broke {splits} wire(s) at junction position {position}")
+        # Transform each placed symbol's pins to world coordinates
+        world_positions: List[Tuple[float, float]] = []
+        for item in sch_data:
+            if not (isinstance(item, list) and len(item) > 0 and item[0] == Symbol("symbol")):
+                continue
+            lib_id_part = next(
+                (
+                    p
+                    for p in item[1:]
+                    if isinstance(p, list) and len(p) >= 2 and p[0] == _SYM_LIB_ID
+                ),
+                None,
+            )
+            if lib_id_part is None:
+                continue  # not a placed instance (e.g. sub-unit inside lib_symbols)
+            lib_id = lib_id_part[1] if isinstance(lib_id_part[1], str) else str(lib_id_part[1])
 
-            # Create junction S-expression
-            # Format: (junction (at x y) (diameter 0) (color 0 0 0 0) (uuid ...))
-            junction_sexp = [
-                Symbol("junction"),
-                [Symbol("at"), position[0], position[1]],
-                [Symbol("diameter"), diameter],
-                [Symbol("color"), 0, 0, 0, 0],
-                [Symbol("uuid"), str(uuid.uuid4())],
-            ]
+            # Read the placed unit number (default 1 for single-unit parts).
+            unit_part = next(
+                (p for p in item[1:] if isinstance(p, list) and len(p) >= 2 and p[0] == _SYM_UNIT),
+                None,
+            )
+            unit_num = int(unit_part[1]) if unit_part is not None else 1
 
-            # Find insertion point
-            sheet_instances_index = None
-            for i, item in enumerate(sch_data):
-                if isinstance(item, list) and len(item) > 0 and item[0] == _SYM_SHEET_INSTANCES:
-                    sheet_instances_index = i
-                    break
+            at_part = next(
+                (p for p in item[1:] if isinstance(p, list) and len(p) >= 3 and p[0] == _SYM_AT),
+                None,
+            )
+            if at_part is None:
+                continue
+            sym_x, sym_y = float(at_part[1]), float(at_part[2])
+            rotation = float(at_part[3]) if len(at_part) > 3 else 0.0
 
+            mirror_x = mirror_y = False
+            for part in item[1:]:
+                if isinstance(part, list) and len(part) >= 2 and part[0] == _SYM_MIRROR:
+                    if part[1] == Symbol("x"):
+                        mirror_x = True
+                    elif part[1] == Symbol("y"):
+                        mirror_y = True
+
+            sym_def = lib_sym_defs.get(lib_id)
+            if sym_def is None:
+                continue
+            local_pins = WireManager._parse_lib_pins(sym_def, unit=unit_num)
+
+            for lx, ly in local_pins:
+                # KiCad lib uses y-up; schematic uses y-down — negate before transform
+                ly = -ly
+                if mirror_x:
+                    ly = -ly
+                if mirror_y:
+                    lx = -lx
+                if rotation != 0.0:
+                    rad = math.radians(rotation)
+                    c, s = math.cos(rad), math.sin(rad)
+                    lx, ly = lx * c - ly * s, lx * s + ly * c
+                world_positions.append((sym_x + lx, sym_y + ly))
+
+        return world_positions
+
+    @staticmethod
+    def sync_junctions(sch_data: list) -> Tuple[int, int]:
+        """Add missing junctions and remove stale ones in sch_data in-place.
+
+        A junction is needed at any point where the total of wire endpoints plus
+        component pin positions is ≥ 3 and at least one wire endpoint is present.
+        This covers wire-only T/X junctions and wire-meets-pin-with-another-wire cases.
+
+        Returns (added_count, removed_count).
+        """
+        from collections import Counter
+
+        wire_endpoints = WireManager._collect_wire_endpoints(sch_data)
+        wire_iu: Counter = Counter(
+            (round(x * _IU_PER_MM), round(y * _IU_PER_MM)) for x, y in wire_endpoints
+        )
+
+        pin_positions = WireManager._collect_pin_positions(sch_data)
+        pin_iu: Counter = Counter(
+            (round(x * _IU_PER_MM), round(y * _IU_PER_MM)) for x, y in pin_positions
+        )
+
+        # wire_iu.items() guarantees wire_cnt >= 1, so no extra guard needed
+        needed_iu = {iu for iu, wire_cnt in wire_iu.items() if wire_cnt + pin_iu.get(iu, 0) >= 3}
+
+        existing = WireManager._get_existing_junctions(sch_data)
+        existing_iu = set(existing.keys())
+
+        # Remove stale junctions; work in reverse index order to avoid shifting
+        stale_indices = sorted([existing[iu] for iu in existing_iu - needed_iu], reverse=True)
+        for idx in stale_indices:
+            del sch_data[idx]
+        removed = len(stale_indices)
+
+        # Locate insertion point for new junctions
+        sheet_instances_index = None
+        for i, item in enumerate(sch_data):
+            if isinstance(item, list) and len(item) > 0 and item[0] == _SYM_SHEET_INSTANCES:
+                sheet_instances_index = i
+                break
+
+        to_add = needed_iu - existing_iu
+        added = 0
+        if to_add:
             if sheet_instances_index is None:
-                logger.error("No sheet_instances section found in schematic")
-                return False
+                logger.warning("sync_junctions: no sheet_instances found, skipping junction insert")
+            else:
+                for iu_x, iu_y in to_add:
+                    x = iu_x / _IU_PER_MM
+                    y = iu_y / _IU_PER_MM
+                    sch_data.insert(sheet_instances_index, WireManager._make_junction_sexp(x, y))
+                    sheet_instances_index += 1
+                    added += 1
 
-            # Insert junction
-            sch_data.insert(sheet_instances_index, junction_sexp)
-            logger.info(f"Injected junction at {position}")
-
-            # Write back
-            with open(schematic_path, "w", encoding="utf-8") as f:
-                output = sexpdata.dumps(sch_data)
-                f.write(output)
-
-            logger.info(f"Successfully added junction to {schematic_path.name}")
-            return True
-
-        except Exception as e:
-            logger.error(f"Error adding junction: {e}")
-            import traceback
-
-            logger.error(traceback.format_exc())
-            return False
+        if added or removed:
+            logger.info(f"sync_junctions: added {added}, removed {removed}")
+        return added, removed
 
     @staticmethod
     def add_no_connect(schematic_path: Path, position: List[float]) -> bool:
@@ -644,6 +846,7 @@ class WireManager:
 
                 if match_fwd or match_rev:
                     del sch_data[i]
+                    WireManager.sync_junctions(sch_data)
                     with open(schematic_path, "w", encoding="utf-8") as f:
                         f.write(sexpdata.dumps(sch_data))
                     logger.info(f"Deleted wire from {start_point} to {end_point}")
@@ -973,29 +1176,24 @@ if __name__ == "__main__":
     print(f"\n✓ Created test schematic: {test_path}")
 
     # Test 1: Add simple wire
-    print("\n[1/5] Testing simple wire creation...")
+    print("\n[1/4] Testing simple wire creation...")
     success = WireManager.add_wire(test_path, [50.8, 50.8], [101.6, 50.8])
     print(f"  {'✓' if success else '✗'} Simple wire: {success}")
 
     # Test 2: Add orthogonal wire
-    print("\n[2/5] Testing orthogonal wire...")
+    print("\n[2/4] Testing orthogonal wire...")
     path = WireManager.create_orthogonal_path([50.8, 60.96], [101.6, 88.9])
     print(f"  Orthogonal path: {path}")
     success = WireManager.add_polyline_wire(test_path, path)
     print(f"  {'✓' if success else '✗'} Polyline wire: {success}")
 
     # Test 3: Add label
-    print("\n[3/5] Testing label creation...")
+    print("\n[3/4] Testing label creation...")
     success = WireManager.add_label(test_path, "VCC", [76.2, 50.8])
     print(f"  {'✓' if success else '✗'} Label: {success}")
 
-    # Test 4: Add junction
-    print("\n[4/5] Testing junction creation...")
-    success = WireManager.add_junction(test_path, [76.2, 50.8])
-    print(f"  {'✓' if success else '✗'} Junction: {success}")
-
-    # Test 5: Add no-connect
-    print("\n[5/5] Testing no-connect creation...")
+    # Test 4: Add no-connect
+    print("\n[4/4] Testing no-connect creation...")
     success = WireManager.add_no_connect(test_path, [127, 50.8])
     print(f"  {'✓' if success else '✗'} No-connect: {success}")
 

python/kicad_interface.py

@@ -389,7 +389,6 @@ class KiCADInterface:
             "get_schematic_component": self._handle_get_schematic_component,
             "add_schematic_wire": self._handle_add_schematic_wire,
             "add_schematic_net_label": self._handle_add_schematic_net_label,
-            "add_schematic_junction": self._handle_add_schematic_junction,
             "connect_to_net": self._handle_connect_to_net,
             "connect_passthrough": self._handle_connect_passthrough,
             "get_schematic_pin_locations": self._handle_get_schematic_pin_locations,
@@ -1628,39 +1627,6 @@ class KiCADInterface:
                 "errorDetails": traceback.format_exc(),
             }
 
-    def _handle_add_schematic_junction(self, params: Dict[str, Any]) -> Dict[str, Any]:
-        """Add a junction (connection dot) to a schematic using WireManager"""
-        logger.info("Adding junction to schematic")
-        try:
-            from pathlib import Path
-
-            from commands.wire_manager import WireManager
-
-            schematic_path = params.get("schematicPath")
-            position = params.get("position")
-
-            if not schematic_path:
-                return {"success": False, "message": "Schematic path is required"}
-            if not position:
-                return {"success": False, "message": "Position is required"}
-
-            success = WireManager.add_junction(Path(schematic_path), position)
-
-            if success:
-                return {"success": True, "message": "Junction added successfully"}
-            else:
-                return {"success": False, "message": "Failed to add junction"}
-        except Exception as e:
-            logger.error(f"Error adding junction to schematic: {str(e)}")
-            import traceback
-
-            logger.error(traceback.format_exc())
-            return {
-                "success": False,
-                "message": str(e),
-                "errorDetails": traceback.format_exc(),
-            }
-
     def _handle_list_schematic_libraries(self, params: Dict[str, Any]) -> Dict[str, Any]:
         """List available symbol libraries"""
         logger.info("Listing schematic libraries")
@@ -2626,6 +2592,10 @@ class KiCADInterface:
             # Update symbol position
             WireDragger.update_symbol_position(sch_data, reference, float(new_x), float(new_y))
 
+            from commands.wire_manager import WireManager as _WireManager
+
+            _WireManager.sync_junctions(sch_data)
+
             with open(schematic_path, "w", encoding="utf-8") as f:
                 f.write(_sexpdata.dumps(sch_data))
 
@@ -2684,6 +2654,19 @@ class KiCADInterface:
                             )
 
                     SchematicManager.save_schematic(schematic, schematic_path)
+
+                    # Re-open with raw sexpdata so sync_junctions can operate on
+                    # the mutated file (mirrors the pattern used in move handler).
+                    import sexpdata as _sexpdata
+
+                    with open(schematic_path, "r", encoding="utf-8") as _f:
+                        sch_data = _sexpdata.load(_f)
+                    from commands.wire_manager import WireManager as _WireManager
+
+                    _WireManager.sync_junctions(sch_data)
+                    with open(schematic_path, "w", encoding="utf-8") as _f:
+                        _f.write(_sexpdata.dumps(sch_data))
+
                     return {"success": True, "reference": reference, "angle": angle}
 
             return {"success": False, "message": f"Component {reference} not found"}

python/schemas/tool_schemas.py

@@ -1704,28 +1704,6 @@ SCHEMATIC_TOOLS = [
             "required": ["schematicPath", "outputPath"],
         },
     },
-    {
-        "name": "add_schematic_junction",
-        "title": "Add Junction to Schematic",
-        "description": "Adds a junction (connection dot) at the specified coordinates on the schematic. Junctions are required in KiCAD to mark intentional connections where wires cross or where a wire branches off another wire. Without a junction, crossing wires are not electrically connected.",
-        "inputSchema": {
-            "type": "object",
-            "properties": {
-                "schematicPath": {
-                    "type": "string",
-                    "description": "Path to schematic file",
-                },
-                "position": {
-                    "type": "array",
-                    "description": "The [x, y] coordinates where the junction should be placed. Must be on an existing wire intersection or branch point.",
-                    "items": {"type": "number"},
-                    "minItems": 2,
-                    "maxItems": 2,
-                },
-            },
-            "required": ["schematicPath", "position"],
-        },
-    },
     # --- Schematic Analysis Tools (read-only) ---
     {
         "name": "get_schematic_view_region",

src/tools/registry.ts

@@ -94,7 +94,6 @@ export const toolCategories: ToolCategory[] = [
       "annotate_schematic",
       "add_schematic_wire",
       "delete_schematic_wire",
-      "add_schematic_junction",
       "add_schematic_net_label",
       "delete_schematic_net_label",
       "connect_to_net",

src/tools/schematic.ts

@@ -510,38 +510,6 @@ edit_schematic_component and set its value to an empty string.`,
     },
   );
 
-  // Add junction dot at a T/X intersection
-  server.tool(
-    "add_schematic_junction",
-    "Place a junction dot at a wire intersection in the schematic. Required at T-branch and X-cross points so KiCAD recognises the electrical connection.",
-    {
-      schematicPath: z.string().describe("Path to the .kicad_sch file"),
-      position: z.array(z.number()).length(2).describe("Junction position [x, y] in mm"),
-    },
-    async (args: { schematicPath: string; position: number[] }) => {
-      const result = await callKicadScript("add_schematic_junction", args);
-      if (result.success) {
-        return {
-          content: [
-            {
-              type: "text" as const,
-              text: result.message || "Junction added successfully",
-            },
-          ],
-        };
-      } else {
-        return {
-          content: [
-            {
-              type: "text" as const,
-              text: `Failed to add junction: ${result.message || "Unknown error"}`,
-            },
-          ],
-        };
-      }
-    },
-  );
-
   // Add net label
   server.tool(
     "add_schematic_net_label",

tests/test_wire_junction_changes.py

@@ -1,7 +1,7 @@
 """
-Tests for fix/tool-schema-descriptions branch changes:
+Tests for schematic wire and junction handling:
 - add_schematic_wire: waypoints param, pin snapping, polyline routing
-- add_schematic_junction: new tool replacing add_schematic_connection
+- Automatic junction sync (add_schematic_junction tool removed)
 - Schema updates in tool_schemas.py
 - ConnectionManager orphaned method removal
 """
@@ -91,22 +91,10 @@ class TestSchemas:
             "add_schematic_connection" not in self.tools
         ), "add_schematic_connection must not appear in SCHEMATIC_TOOLS"
 
-    def test_add_schematic_junction_present(self) -> None:
-        assert "add_schematic_junction" in self.tools
-
-    def test_add_schematic_junction_schema(self) -> None:
-        schema = self.tools["add_schematic_junction"]["inputSchema"]
-        props = schema["properties"]
-        assert "schematicPath" in props
-        assert "position" in props
-        assert set(schema["required"]) >= {"schematicPath", "position"}
-
-    def test_add_schematic_junction_position_is_array(self) -> None:
-        schema = self.tools["add_schematic_junction"]["inputSchema"]
-        pos = schema["properties"]["position"]
-        assert pos["type"] == "array"
-        assert pos.get("minItems") == 2
-        assert pos.get("maxItems") == 2
+    def test_add_schematic_junction_removed(self) -> None:
+        assert (
+            "add_schematic_junction" not in self.tools
+        ), "add_schematic_junction was removed; junctions are now managed automatically"
 
 
 # ---------------------------------------------------------------------------
@@ -137,7 +125,6 @@ class TestHandlerDispatch:
             # Build the handler map the same way the real __init__ does
             obj._tool_handlers = {
                 "add_schematic_wire": obj._handle_add_schematic_wire,
-                "add_schematic_junction": obj._handle_add_schematic_junction,
                 "add_schematic_net_label": obj._handle_add_schematic_net_label,
             }
         self.handlers = obj._tool_handlers
@@ -148,10 +135,10 @@ class TestHandlerDispatch:
         # Just verify the class has the handler method
         assert hasattr(KiCADInterface, "_handle_add_schematic_wire")
 
-    def test_add_schematic_junction_registered(self) -> None:
+    def test_add_schematic_junction_handler_removed(self) -> None:
         from kicad_interface import KiCADInterface
 
-        assert hasattr(KiCADInterface, "_handle_add_schematic_junction")
+        assert not hasattr(KiCADInterface, "_handle_add_schematic_junction")
 
     def test_add_schematic_connection_not_present(self) -> None:
         from kicad_interface import KiCADInterface
@@ -418,67 +405,7 @@ class TestPinSnapping:
 
 
 # ---------------------------------------------------------------------------
-# 6. _handle_add_schematic_junction — unit tests
-# ---------------------------------------------------------------------------
-
-
-class TestHandleAddSchematicJunction:
-
-    @pytest.fixture(autouse=True)
-    def setup(self) -> Any:
-        import types
-
-        for mod in ["pcbnew", "skip"]:
-            sys.modules.setdefault(mod, types.ModuleType(mod))
-        from kicad_interface import KiCADInterface
-
-        with patch.object(KiCADInterface, "__init__", lambda self, *a, **kw: None):
-            self.iface = KiCADInterface.__new__(KiCADInterface)
-
-    def test_missing_schematic_path(self) -> None:
-        result = self.iface._handle_add_schematic_junction({"position": [10.0, 20.0]})
-        assert result["success"] is False
-        assert "Schematic path" in result["message"]
-
-    def test_missing_position(self) -> None:
-        result = self.iface._handle_add_schematic_junction({"schematicPath": "/tmp/x.kicad_sch"})
-        assert result["success"] is False
-        assert "Position" in result["message"]
-
-    @patch("commands.wire_manager.WireManager.add_junction", return_value=True)
-    def test_success(self, mock_jct: Any) -> None:
-        sch = _make_temp_sch()
-        try:
-            result = self.iface._handle_add_schematic_junction(
-                {
-                    "schematicPath": str(sch),
-                    "position": [25.4, 25.4],
-                }
-            )
-            assert result["success"] is True
-            assert "Junction added" in result["message"]
-            mock_jct.assert_called_once_with(sch, [25.4, 25.4])
-        finally:
-            shutil.rmtree(sch.parent, ignore_errors=True)
-
-    @patch("commands.wire_manager.WireManager.add_junction", return_value=False)
-    def test_failure(self, _: Any) -> None:
-        sch = _make_temp_sch()
-        try:
-            result = self.iface._handle_add_schematic_junction(
-                {
-                    "schematicPath": str(sch),
-                    "position": [25.4, 25.4],
-                }
-            )
-            assert result["success"] is False
-            assert "Failed" in result["message"]
-        finally:
-            shutil.rmtree(sch.parent, ignore_errors=True)
-
-
-# ---------------------------------------------------------------------------
-# 7. ConnectionManager — orphaned methods removed
+# 6. ConnectionManager — orphaned methods removed
 # ---------------------------------------------------------------------------
 
 
@@ -541,19 +468,6 @@ class TestIntegrationWireManager:
         wires = _find_elements(data, "wire")
         assert len(wires) == 3, f"4 waypoints should produce 3 wire segments, got {len(wires)}"
 
-    def test_add_junction_writes_junction_element(self, sch: Any) -> None:
-        from commands.wire_manager import WireManager
-
-        ok = WireManager.add_junction(sch, [25.4, 25.4])
-        assert ok is True
-        data = _parse_sch(sch)
-        junctions = _find_elements(data, "junction")
-        assert len(junctions) == 1
-        # Verify position
-        at = junctions[0][1]  # (at x y)
-        assert at[1] == 25.4
-        assert at[2] == 25.4
-
     def test_wire_endpoint_coordinates_match(self, sch: Any) -> None:
         from commands.wire_manager import WireManager
 
@@ -590,18 +504,6 @@ class TestIntegrationHandlerEndToEnd:
         yield
         shutil.rmtree(self.sch.parent, ignore_errors=True)
 
-    def test_junction_handler_writes_junction(self) -> None:
-        result = self.iface._handle_add_schematic_junction(
-            {
-                "schematicPath": str(self.sch),
-                "position": [50.8, 50.8],
-            }
-        )
-        assert result["success"] is True
-        data = _parse_sch(self.sch)
-        junctions = _find_elements(data, "junction")
-        assert len(junctions) == 1
-
     def test_wire_handler_two_points_writes_wire(self) -> None:
         result = self.iface._handle_add_schematic_wire(
             {
@@ -934,7 +836,7 @@ class TestBreakWiresAtPoint:
 
 @pytest.mark.integration
 class TestIntegrationTJunction:
-    """Integration tests for T-junction wire breaking during add_wire/add_junction."""
+    """Integration tests for T-junction wire breaking during add_wire."""
 
     @pytest.fixture(autouse=True)
     def sch(self) -> Any:
@@ -966,28 +868,6 @@ class TestIntegrationTJunction:
         wires = _find_elements(data, "wire")
         assert len(wires) == 2, f"Expected 2 wires (no split), got {len(wires)}"
 
-    def test_add_junction_breaks_wire(self, sch: Any) -> None:
-        """Adding a junction mid-wire should split that wire."""
-        from commands.wire_manager import WireManager
-
-        WireManager.add_wire(sch, [0, 0], [30, 0])
-        WireManager.add_junction(sch, [15, 0])
-        data = _parse_sch(sch)
-        wires = _find_elements(data, "wire")
-        assert len(wires) == 2, f"Expected 2 wires after junction split, got {len(wires)}"
-        junctions = _find_elements(data, "junction")
-        assert len(junctions) == 1
-
-    def test_add_junction_at_wire_endpoint_no_split(self, sch: Any) -> None:
-        """Junction at wire endpoint should not split it."""
-        from commands.wire_manager import WireManager
-
-        WireManager.add_wire(sch, [0, 0], [20, 0])
-        WireManager.add_junction(sch, [20, 0])
-        data = _parse_sch(sch)
-        wires = _find_elements(data, "wire")
-        assert len(wires) == 1, f"Expected 1 wire (no split at endpoint), got {len(wires)}"
-
     def test_polyline_breaks_existing_wire(self, sch: Any) -> None:
         """Polyline whose start/end hits mid-wire should break it."""
         from commands.wire_manager import WireManager
@@ -1008,3 +888,589 @@ class TestIntegrationTJunction:
         data = _parse_sch(sch)
         wires = _find_elements(data, "wire")
         assert len(wires) == 1
+
+
+# ---------------------------------------------------------------------------
+# 14. Auto junction sync
+# ---------------------------------------------------------------------------
+
+
+class TestSyncJunctionsUnit:
+    """Unit tests for WireManager.sync_junctions operating on raw sch_data."""
+
+    def _base_data(self) -> Any:
+        """Minimal sch_data with a sheet_instances section."""
+        return [Symbol("kicad_sch"), [Symbol("sheet_instances")]]
+
+    def _wire(self, x1: float, y1: float, x2: float, y2: float) -> list:
+        return [
+            Symbol("wire"),
+            [Symbol("pts"), [Symbol("xy"), x1, y1], [Symbol("xy"), x2, y2]],
+            [Symbol("stroke"), [Symbol("width"), 0], [Symbol("type"), Symbol("default")]],
+            [Symbol("uuid"), "00000000-0000-0000-0000-000000000000"],
+        ]
+
+    def _junction(self, x: float, y: float) -> list:
+        return [
+            Symbol("junction"),
+            [Symbol("at"), x, y],
+            [Symbol("diameter"), 0],
+            [Symbol("color"), 0, 0, 0, 0],
+            [Symbol("uuid"), "00000000-0000-0000-0000-000000000001"],
+        ]
+
+    def test_t_junction_adds_junction(self) -> None:
+        """Three wire endpoints meeting at one point → one junction added."""
+        from commands.wire_manager import WireManager
+
+        data = self._base_data()
+        # Horizontal wire split at (10,0): (0,0)→(10,0) and (10,0)→(20,0)
+        data.insert(1, self._wire(0, 0, 10, 0))
+        data.insert(1, self._wire(10, 0, 20, 0))
+        # Vertical wire whose endpoint is (10,0): 3 endpoints at (10,0)
+        data.insert(1, self._wire(10, -10, 10, 0))
+
+        added, removed = WireManager.sync_junctions(data)
+
+        assert added == 1
+        assert removed == 0
+        junctions = _find_elements(data, "junction")
+        assert len(junctions) == 1
+        at = next(p for p in junctions[0][1:] if isinstance(p, list) and p[0] == Symbol("at"))
+        assert abs(at[1] - 10) < 1e-6
+        assert abs(at[2] - 0) < 1e-6
+
+    def test_two_wire_join_no_junction(self) -> None:
+        """Two wires meeting end-to-end (2 endpoints) → no junction."""
+        from commands.wire_manager import WireManager
+
+        data = self._base_data()
+        data.insert(1, self._wire(0, 0, 10, 0))
+        data.insert(1, self._wire(10, 0, 20, 0))
+
+        added, removed = WireManager.sync_junctions(data)
+
+        assert added == 0
+        assert removed == 0
+        assert _find_elements(data, "junction") == []
+
+    def test_stale_junction_removed(self) -> None:
+        """A junction with fewer than 3 wire endpoints at its position is removed."""
+        from commands.wire_manager import WireManager
+
+        data = self._base_data()
+        # Only two wires meeting at (10,0) — junction is stale
+        data.insert(1, self._wire(0, 0, 10, 0))
+        data.insert(1, self._wire(10, 0, 20, 0))
+        data.insert(1, self._junction(10, 0))
+
+        added, removed = WireManager.sync_junctions(data)
+
+        assert added == 0
+        assert removed == 1
+        assert _find_elements(data, "junction") == []
+
+    def test_x_junction_gets_one_junction(self) -> None:
+        """Four wire endpoints meeting (X-junction) → exactly one junction."""
+        from commands.wire_manager import WireManager
+
+        data = self._base_data()
+        # Simulate already-split X: four segments meeting at (10,10)
+        data.insert(1, self._wire(0, 10, 10, 10))
+        data.insert(1, self._wire(10, 10, 20, 10))
+        data.insert(1, self._wire(10, 0, 10, 10))
+        data.insert(1, self._wire(10, 10, 10, 20))
+
+        added, removed = WireManager.sync_junctions(data)
+
+        assert added == 1
+        junctions = _find_elements(data, "junction")
+        assert len(junctions) == 1
+
+    def test_idempotent_on_correct_junction(self) -> None:
+        """Running sync_junctions when junction is already correct is a no-op."""
+        from commands.wire_manager import WireManager
+
+        data = self._base_data()
+        data.insert(1, self._wire(0, 0, 10, 0))
+        data.insert(1, self._wire(10, 0, 20, 0))
+        data.insert(1, self._wire(10, -10, 10, 0))
+        data.insert(1, self._junction(10, 0))
+
+        added, removed = WireManager.sync_junctions(data)
+
+        assert added == 0
+        assert removed == 0
+        assert len(_find_elements(data, "junction")) == 1
+
+
+@pytest.mark.integration
+class TestSyncJunctionsIntegration:
+    """Integration tests for automatic junction sync through add_wire / delete_wire."""
+
+    @pytest.fixture(autouse=True)
+    def sch(self) -> Any:
+        path = _make_temp_sch()
+        yield path
+        shutil.rmtree(path.parent, ignore_errors=True)
+
+    def test_t_junction_auto_inserted_on_add_wire(self, sch: Any) -> None:
+        """Adding a wire that creates a T-junction should auto-insert a junction dot."""
+        from commands.wire_manager import WireManager
+
+        # Horizontal wire, then split it manually, then add connecting vertical
+        WireManager.add_wire(sch, [0, 10], [10, 10])
+        WireManager.add_wire(sch, [10, 10], [20, 10])
+        WireManager.add_wire(sch, [10, 0], [10, 10])  # creates T at (10,10)
+
+        data = _parse_sch(sch)
+        junctions = _find_elements(data, "junction")
+        assert len(junctions) == 1, f"Expected 1 junction, got {len(junctions)}"
+
+    def test_straight_join_no_junction(self, sch: Any) -> None:
+        """Two wires joining end-to-end should not produce a junction."""
+        from commands.wire_manager import WireManager
+
+        WireManager.add_wire(sch, [0, 0], [10, 0])
+        WireManager.add_wire(sch, [10, 0], [20, 0])
+
+        data = _parse_sch(sch)
+        junctions = _find_elements(data, "junction")
+        assert junctions == [], f"Expected no junctions, got {len(junctions)}"
+
+    def test_delete_wire_removes_stale_junction(self, sch: Any) -> None:
+        """Removing a wire that was part of a T-junction should remove the junction."""
+        from commands.wire_manager import WireManager
+
+        WireManager.add_wire(sch, [0, 10], [10, 10])
+        WireManager.add_wire(sch, [10, 10], [20, 10])
+        WireManager.add_wire(sch, [10, 0], [10, 10])  # creates T, junction auto-inserted
+
+        data = _parse_sch(sch)
+        assert len(_find_elements(data, "junction")) == 1, "Pre-condition: junction present"
+
+        WireManager.delete_wire(sch, [10, 0], [10, 10])  # remove the branch
+
+        data = _parse_sch(sch)
+        junctions = _find_elements(data, "junction")
+        assert junctions == [], f"Expected junction removed, got {len(junctions)}"
+
+    def test_polyline_t_junction_auto_inserted(self, sch: Any) -> None:
+        """Polyline whose endpoint hits a wire midpoint auto-inserts a junction."""
+        from commands.wire_manager import WireManager
+
+        WireManager.add_wire(sch, [0, 10], [20, 10])  # horizontal
+        # Polyline from above ending at (10,10) — mid-wire, wire breaks → T at (10,10)
+        WireManager.add_polyline_wire(sch, [[10, 0], [10, 10]])
+
+        data = _parse_sch(sch)
+        junctions = _find_elements(data, "junction")
+        assert len(junctions) == 1, f"Expected 1 junction after polyline T, got {len(junctions)}"
+
+
+# ---------------------------------------------------------------------------
+# 15. Pin-aware junction sync
+# ---------------------------------------------------------------------------
+
+
+class TestSyncJunctionsPinAware:
+    """Unit tests for junction sync when component pins are present."""
+
+    def _base_data_with_resistor(self, sym_x: float, sym_y: float, rotation: float = 0) -> Any:
+        """Build minimal sch_data with a Device:R-like symbol.
+
+        Pin 1 is at (0, 3.81) in lib coords → world (sym_x, sym_y - 3.81) at rot=0.
+        Pin 2 is at (0, -3.81) in lib coords → world (sym_x, sym_y + 3.81) at rot=0.
+        """
+        pin1_sexp = [
+            Symbol("pin"),
+            Symbol("passive"),
+            Symbol("line"),
+            [Symbol("at"), 0, 3.81, 270],
+            [Symbol("length"), 1.27],
+            [Symbol("name"), "~"],
+            [Symbol("number"), "1"],
+        ]
+        pin2_sexp = [
+            Symbol("pin"),
+            Symbol("passive"),
+            Symbol("line"),
+            [Symbol("at"), 0, -3.81, 90],
+            [Symbol("length"), 1.27],
+            [Symbol("name"), "~"],
+            [Symbol("number"), "2"],
+        ]
+        lib_symbol = [
+            Symbol("symbol"),
+            "Device:R",
+            [Symbol("pin_numbers"), Symbol("hide")],
+            [Symbol("symbol"), "R_1_1", pin1_sexp, pin2_sexp],
+        ]
+        lib_symbols_section = [Symbol("lib_symbols"), lib_symbol]
+
+        placed_symbol = [
+            Symbol("symbol"),
+            [Symbol("lib_id"), "Device:R"],
+            [Symbol("at"), sym_x, sym_y, rotation],
+            [Symbol("unit"), 1],
+            [Symbol("property"), "Reference", "R1", [Symbol("at"), sym_x, sym_y, 0]],
+            [Symbol("property"), "Value", "10k", [Symbol("at"), sym_x, sym_y, 0]],
+            [Symbol("pin"), "1", [Symbol("uuid"), "pin1-uuid"]],
+            [Symbol("pin"), "2", [Symbol("uuid"), "pin2-uuid"]],
+        ]
+
+        return [
+            Symbol("kicad_sch"),
+            lib_symbols_section,
+            placed_symbol,
+            [Symbol("sheet_instances")],
+        ]
+
+    def _wire(self, x1: float, y1: float, x2: float, y2: float) -> list:
+        return [
+            Symbol("wire"),
+            [Symbol("pts"), [Symbol("xy"), x1, y1], [Symbol("xy"), x2, y2]],
+            [Symbol("stroke"), [Symbol("width"), 0], [Symbol("type"), Symbol("default")]],
+            [Symbol("uuid"), "wire-uuid"],
+        ]
+
+    def test_collect_pin_positions_no_rotation(self) -> None:
+        """_collect_pin_positions returns correct world coords for R at (100,100) rot=0."""
+        from commands.wire_manager import WireManager
+
+        data = self._base_data_with_resistor(100, 100, rotation=0)
+        pins = WireManager._collect_pin_positions(data)
+
+        # Pin 1: lib (0, 3.81) → y-negate → (0, -3.81) → world (100, 96.19)
+        # Pin 2: lib (0, -3.81) → y-negate → (0, 3.81) → world (100, 103.81)
+        assert len(pins) == 2
+        pin_set = {(round(x, 2), round(y, 2)) for x, y in pins}
+        assert (100.0, 96.19) in pin_set
+        assert (100.0, 103.81) in pin_set
+
+    def test_collect_pin_positions_rotation_90(self) -> None:
+        """_collect_pin_positions handles 90° rotation correctly."""
+        from commands.wire_manager import WireManager
+
+        data = self._base_data_with_resistor(100, 100, rotation=90)
+        pins = WireManager._collect_pin_positions(data)
+
+        # Pin 1: lib (0, 3.81) → y-neg → (0, -3.81) → rot90 → (3.81, 0) → world (103.81, 100)
+        # Pin 2: lib (0, -3.81) → y-neg → (0, 3.81) → rot90 → (-3.81, 0) → world (96.19, 100)
+        assert len(pins) == 2
+        pin_set = {(round(x, 2), round(y, 2)) for x, y in pins}
+        assert (103.81, 100.0) in pin_set
+        assert (96.19, 100.0) in pin_set
+
+    def test_two_wires_plus_pin_gets_junction(self) -> None:
+        """Two wires ending at a pin position → junction needed (total 3)."""
+        from commands.wire_manager import WireManager
+
+        # R at (100, 100): pin 1 world = (100, 96.19)
+        data = self._base_data_with_resistor(100, 100, rotation=0)
+        # Two wires both ending at pin 1
+        data.insert(2, self._wire(80, 96.19, 100, 96.19))
+        data.insert(2, self._wire(100, 96.19, 120, 96.19))
+
+        added, removed = WireManager.sync_junctions(data)
+
+        assert added == 1, f"Expected 1 junction added, got {added}"
+        assert removed == 0
+
+    def test_one_wire_plus_pin_no_junction(self) -> None:
+        """Single wire connecting to a pin (total 2) → no junction."""
+        from commands.wire_manager import WireManager
+
+        data = self._base_data_with_resistor(100, 100, rotation=0)
+        # Single wire ending at pin 1
+        data.insert(2, self._wire(80, 96.19, 100, 96.19))
+
+        added, removed = WireManager.sync_junctions(data)
+
+        assert added == 0, f"Expected no junction, got {added}"
+        assert removed == 0
+
+    def test_wire_midpoint_pin_gets_junction(self) -> None:
+        """Wire passing through (broken at) a pin position + another wire → junction."""
+        from commands.wire_manager import WireManager
+
+        # R at (100, 100): pin 1 world = (100, 96.19)
+        # Simulate a horizontal wire already split at pin position
+        data = self._base_data_with_resistor(100, 100, rotation=0)
+        data.insert(2, self._wire(80, 96.19, 100, 96.19))  # left segment
+        data.insert(2, self._wire(100, 96.19, 120, 96.19))  # right segment
+        # wire_cnt=2, pin_cnt=1 → total=3 → junction
+
+        added, removed = WireManager.sync_junctions(data)
+
+        assert added == 1, f"Expected junction at wire-split + pin, got {added}"
+
+    # ------------------------------------------------------------------
+    # Mirror / mirror+rotation tests
+    # Transform order (per _collect_pin_positions docstring):
+    #   1. y-negate  (lib y-up → schematic y-down)
+    #   2. mirror_x  → ly = -ly
+    #      mirror_y  → lx = -lx
+    #   3. rotate by `rotation` degrees
+    #   4. translate by (sym_x, sym_y)
+    # TODO: verify against KiCad's actual transform order — see schematic_view.py
+    # ------------------------------------------------------------------
+
+    def _base_data_with_resistor_mirrored(
+        self,
+        sym_x: float,
+        sym_y: float,
+        rotation: float = 0,
+        mirror: str = "x",
+    ) -> Any:
+        """Like _base_data_with_resistor but injects a (mirror x) or (mirror y) clause
+        into the placed-symbol form."""
+        data = self._base_data_with_resistor(sym_x, sym_y, rotation)
+        # data[2] is the placed_symbol list
+        placed = data[2]
+        placed.append([Symbol("mirror"), Symbol(mirror)])
+        return data
+
+    def test_collect_pin_positions_mirror_x_rotation_0(self) -> None:
+        """mirror_x at rotation=0: pins flip across the local x-axis (y-coords invert).
+
+        Pin 1: lib(0, 3.81) → y-neg → (0, -3.81) → mirror_x → (0, +3.81) → world (100, 103.81)
+        Pin 2: lib(0,-3.81) → y-neg → (0, +3.81) → mirror_x → (0, -3.81) → world (100,  96.19)
+        """
+        from commands.wire_manager import WireManager
+
+        data = self._base_data_with_resistor_mirrored(100, 100, rotation=0, mirror="x")
+        pins = WireManager._collect_pin_positions(data)
+
+        assert len(pins) == 2
+        pin_set = {(round(x, 2), round(y, 2)) for x, y in pins}
+        assert (100.0, 103.81) in pin_set
+        assert (100.0, 96.19) in pin_set
+
+    def test_collect_pin_positions_mirror_y_rotation_0(self) -> None:
+        """mirror_y at rotation=0: flips lx (which is 0 for both pins) → same world coords.
+
+        Pin 1: lib(0, 3.81) → y-neg → (0, -3.81) → mirror_y: lx=-0=0 → world (100, 96.19)
+        Pin 2: lib(0,-3.81) → y-neg → (0, +3.81) → mirror_y: lx=-0=0 → world (100, 103.81)
+        """
+        from commands.wire_manager import WireManager
+
+        data = self._base_data_with_resistor_mirrored(100, 100, rotation=0, mirror="y")
+        pins = WireManager._collect_pin_positions(data)
+
+        assert len(pins) == 2
+        pin_set = {(round(x, 2), round(y, 2)) for x, y in pins}
+        assert (100.0, 96.19) in pin_set
+        assert (100.0, 103.81) in pin_set
+
+    def test_collect_pin_positions_mirror_x_rotation_90(self) -> None:
+        """mirror_x combined with rotation=90.
+
+        Pin 1: lib(0, 3.81) → y-neg → (0,-3.81) → mirror_x → (0,+3.81)
+               → rot90 (c=0,s=1): lx'=0*0-3.81*1=-3.81, ly'=0*1+3.81*0=0
+               → world (96.19, 100.0)
+        Pin 2: lib(0,-3.81) → y-neg → (0,+3.81) → mirror_x → (0,-3.81)
+               → rot90: lx'=0*0-(-3.81)*1=3.81, ly'=0*1+(-3.81)*0=0
+               → world (103.81, 100.0)
+        """
+        from commands.wire_manager import WireManager
+
+        data = self._base_data_with_resistor_mirrored(100, 100, rotation=90, mirror="x")
+        pins = WireManager._collect_pin_positions(data)
+
+        assert len(pins) == 2
+        pin_set = {(round(x, 2), round(y, 2)) for x, y in pins}
+        assert (96.19, 100.0) in pin_set
+        assert (103.81, 100.0) in pin_set
+
+    def test_collect_pin_positions_mirror_y_rotation_180(self) -> None:
+        """mirror_y combined with rotation=180.
+
+        Pin 1: lib(0, 3.81) → y-neg → (0,-3.81) → mirror_y: lx=-0=0, ly=-3.81
+               → rot180 (c=-1,s=0): lx'=0*(-1)-(-3.81)*0=0, ly'=0*0+(-3.81)*(-1)=3.81
+               → world (100.0, 103.81)
+        Pin 2: lib(0,-3.81) → y-neg → (0,+3.81) → mirror_y: lx=0, ly=3.81
+               → rot180: lx'=0*(-1)-3.81*0=0, ly'=0*0+3.81*(-1)=-3.81
+               → world (100.0, 96.19)
+        """
+        from commands.wire_manager import WireManager
+
+        data = self._base_data_with_resistor_mirrored(100, 100, rotation=180, mirror="y")
+        pins = WireManager._collect_pin_positions(data)
+
+        assert len(pins) == 2
+        pin_set = {(round(x, 2), round(y, 2)) for x, y in pins}
+        assert (100.0, 103.81) in pin_set
+        assert (100.0, 96.19) in pin_set
+
+
+# ---------------------------------------------------------------------------
+# 16. Multi-unit IC pin-awareness  (LM324-like quad op-amp)
+# ---------------------------------------------------------------------------
+
+
+class TestMultiUnitLibPins:
+    """Unit tests for _parse_lib_pins unit-aware filtering (multi-unit ICs)."""
+
+    @staticmethod
+    def _make_lm324_lib_symbol() -> list:
+        """Return a minimal lib_symbols entry modelled on the LM324 quad op-amp.
+
+        Structure:
+          (symbol "Amplifier_Operational:LM324"
+            (symbol "LM324_1_1"  ;; unit 1 – op-amp body A
+              (pin input  line (at -5 2.54 0) ...)   ; IN+
+              (pin input  line (at -5 -2.54 0) ...)  ; IN-
+              (pin output line (at 5 0 180) ...)      ; OUT
+            )
+            (symbol "LM324_2_1"  ;; unit 2 – op-amp body B
+              (pin input  line (at -5 2.54 0) ...)
+              (pin input  line (at -5 -2.54 0) ...)
+              (pin output line (at 5 0 180) ...)
+            )
+            (symbol "LM324_3_1"  ;; unit 3
+              ...
+            )
+            (symbol "LM324_4_1"  ;; unit 4
+              ...
+            )
+            (symbol "LM324_5_1"  ;; unit 5 = power (common)
+              (pin power_in line (at 0 5 270) ...)   ; VCC
+              (pin power_in line (at 0 -5 90) ...)   ; GND
+            )
+          )
+        """
+
+        def _pin(px: float, py: float) -> list:
+            return [
+                Symbol("pin"),
+                Symbol("input"),
+                Symbol("line"),
+                [Symbol("at"), px, py, 0],
+                [Symbol("length"), 1.27],
+                [Symbol("name"), "~"],
+                [Symbol("number"), "1"],
+            ]
+
+        def _sub(name: str, pins: list) -> list:
+            return [Symbol("symbol"), name] + pins
+
+        unit1 = _sub("LM324_1_1", [_pin(-5, 2.54), _pin(-5, -2.54), _pin(5, 0)])
+        unit2 = _sub("LM324_2_1", [_pin(-5, 12.54), _pin(-5, -12.54), _pin(5, 10)])
+        unit3 = _sub("LM324_3_1", [_pin(-5, 22.54), _pin(-5, -22.54), _pin(5, 20)])
+        unit4 = _sub("LM324_4_1", [_pin(-5, 32.54), _pin(-5, -32.54), _pin(5, 30)])
+        power = _sub("LM324_5_1", [_pin(0, 5), _pin(0, -5)])  # unit 5 = common/power
+
+        return [
+            Symbol("symbol"),
+            "Amplifier_Operational:LM324",
+            unit1,
+            unit2,
+            unit3,
+            unit4,
+            power,
+        ]
+
+    def test_unit2_returns_only_unit2_and_common_pins(self) -> None:
+        """Placing unit 2 must return 3 op-amp pins + 2 power (common) pins = 5 total."""
+        from commands.wire_manager import WireManager
+
+        sym_def = self._make_lm324_lib_symbol()
+        pins = WireManager._parse_lib_pins(sym_def, unit=2)
+
+        # Unit 2 contributes 3 pins; LM324_5_1 (unit 5 != 2 != 0) should be excluded.
+        # Only unit==2 OR unit==0 qualifies. LM324_5_1 has unit=5, so it is skipped.
+        assert (
+            len(pins) == 3
+        ), f"Expected 3 pins (unit 2 only, power unit 5 excluded), got {len(pins)}: {pins}"
+        # The three unit-2 pins have distinct y-coords in our fixture
+        pin_coords = {(round(x, 2), round(y, 2)) for x, y in pins}
+        assert (-5.0, 12.54) in pin_coords
+        assert (-5.0, -12.54) in pin_coords
+        assert (5.0, 10.0) in pin_coords
+
+    def test_unit1_does_not_include_unit2_pins(self) -> None:
+        """Placing unit 1 must not return pins from units 2-5."""
+        from commands.wire_manager import WireManager
+
+        sym_def = self._make_lm324_lib_symbol()
+        pins = WireManager._parse_lib_pins(sym_def, unit=1)
+
+        assert len(pins) == 3, f"Expected 3 pins (unit 1 only), got {len(pins)}: {pins}"
+        pin_coords = {(round(x, 2), round(y, 2)) for x, y in pins}
+        assert (-5.0, 2.54) in pin_coords
+        assert (-5.0, -2.54) in pin_coords
+        assert (5.0, 0.0) in pin_coords
+
+    def test_common_unit_zero_always_included(self) -> None:
+        """A sub-unit named <base>_0_1 (unit=0) must appear for every placed unit."""
+        from commands.wire_manager import WireManager
+
+        # Build a symbol that has a _0_1 common sub-unit
+        def _pin(px: float, py: float) -> list:
+            return [
+                Symbol("pin"),
+                Symbol("power_in"),
+                Symbol("line"),
+                [Symbol("at"), px, py, 0],
+                [Symbol("length"), 1.27],
+                [Symbol("name"), "VCC"],
+                [Symbol("number"), "1"],
+            ]
+
+        sym_def = [
+            Symbol("symbol"),
+            "Device:Foo",
+            [Symbol("symbol"), "Foo_0_1", _pin(0, 5)],  # common (unit 0)
+            [Symbol("symbol"), "Foo_1_1", _pin(1, 1)],  # unit 1
+            [Symbol("symbol"), "Foo_2_1", _pin(2, 2)],  # unit 2
+        ]
+
+        pins_u1 = WireManager._parse_lib_pins(sym_def, unit=1)
+        pins_u2 = WireManager._parse_lib_pins(sym_def, unit=2)
+
+        # Both units should include the unit-0 common pin
+        assert len(pins_u1) == 2, f"Unit 1: expected 2 pins (1 common + 1 own), got {len(pins_u1)}"
+        assert len(pins_u2) == 2, f"Unit 2: expected 2 pins (1 common + 1 own), got {len(pins_u2)}"
+
+    def test_no_spurious_junctions_for_multi_unit_ic(self) -> None:
+        """Placing unit 2 of an LM324-like part must not create phantom junctions
+        from the pins of units 1, 3, 4, or 5."""
+        from commands.wire_manager import WireManager
+
+        sym_def = self._make_lm324_lib_symbol()
+        lib_symbols_section = [Symbol("lib_symbols"), sym_def]
+
+        # Place unit 2 at origin (0, 0), no rotation
+        placed = [
+            Symbol("symbol"),
+            [Symbol("lib_id"), "Amplifier_Operational:LM324"],
+            [Symbol("at"), 0, 0, 0],
+            [Symbol("unit"), 2],
+        ]
+
+        # A single wire from (-30, 12.54) to (-5, 12.54) connects to unit-2 IN+ pin.
+        # world pin coords: lib (−5, 12.54) → y-negate → (−5, −12.54) → + origin = (−5, −12.54)
+        # (The y-negation is part of KiCad's lib-to-schematic transform.)
+        wire = [
+            Symbol("wire"),
+            [Symbol("pts"), [Symbol("xy"), -30, -12.54], [Symbol("xy"), -5, -12.54]],
+            [Symbol("stroke"), [Symbol("width"), 0], [Symbol("type"), Symbol("default")]],
+            [Symbol("uuid"), "test-wire"],
+        ]
+
+        data = [
+            Symbol("kicad_sch"),
+            lib_symbols_section,
+            placed,
+            wire,
+            [Symbol("sheet_instances")],
+        ]
+
+        added, removed = WireManager.sync_junctions(data)
+
+        # Wire endpoint at (−5, −12.54) plus 1 pin = 2 total → no junction needed.
+        assert added == 0, (
+            f"Expected 0 junctions (wire endpoint + 1 pin = 2), got {added} added. "
+            "Phantom pins from other units may be causing false positives."
+        )