diff --git a/periscope/src/backend/periscopex/parsers.py b/periscope/src/backend/periscopex/parsers.py
new file mode 100644
index 0000000..0f25ca0
--- /dev/null
+++ b/periscope/src/backend/periscopex/parsers.py
@@ -0,0 +1,213 @@
+"""Periscope schematic ingest: PADS ASCII, BOM CSV, and format dispatch.
+
+KiCad schematic/netlist parsing stays in ``parsers_kicad`` (already native).
+KiCad PCB via≠pad stays in ``parsers_kicad_pcb``. EDIF lives in ``parsers_edif``.
+"""
+
+from __future__ import annotations
+
+import csv
+import re
+from pathlib import Path
+from typing import Literal
+
+NetlistFormat = Literal["pads", "edif", "kicad_xml", "kicad_sexp", "kicad_sch"]
+
+_GND_EXACT = {"GND", "AGND", "DGND", "PGND", "VSS", "0V"}
+_DNP_TRUE = {"1", "y", "yes", "true", "dnp", "dni", "x"}
+_FITTED_FALSE = {"0", "n", "no", "false"}
+
+
+def detect_netlist_format(content: bytes | str) -> NetlistFormat:
+    if isinstance(content, bytes):
+        text = content[:2048].decode("utf-8", errors="replace")
+    else:
+        text = content[:2048]
+    head = text.lstrip("\ufeff").lstrip()
+    low = head[:40].lower()
+    if low.startswith("(edif"):
+        return "edif"
+    if low.startswith("(kicad_sch"):
+        return "kicad_sch"
+    if low.startswith("(export"):
+        return "kicad_sexp"
+    if low.startswith("<?xml") or low.startswith("<export"):
+        return "kicad_xml"
+    return "pads"
+
+
+def _match_known_ref(tokens: list[str], known_refs: set[str] | None) -> tuple[str | None, str]:
+    if not tokens:
+        return None, ""
+    if known_refs:
+        for n in range(min(len(tokens), 8), 0, -1):
+            candidate = " ".join(tokens[:n])
+            if candidate in known_refs:
+                return candidate, " ".join(tokens[n:])
+    if len(tokens) >= 2:
+        return tokens[0], " ".join(tokens[1:])
+    return tokens[0], ""
+
+
+def _pins_from_signal_line(tokens: list[str], known_refs: set[str] | None) -> list[tuple[str, str]]:
+    pins: list[tuple[str, str]] = []
+    consumed = -1
+    for j, token in enumerate(tokens):
+        if j <= consumed or "." not in token:
+            continue
+        last_word, pin = token.rsplit(".", 1)
+        if known_refs:
+            matched_start: int | None = None
+            for start in range(consumed + 1, j + 1):
+                parts = tokens[start:j] + ([last_word] if last_word else [])
+                candidate = " ".join(parts)
+                if candidate and candidate in known_refs:
+                    matched_start = start
+                    break
+            if matched_start is not None:
+                ref = " ".join(tokens[matched_start:j] + ([last_word] if last_word else []))
+                pins.append((ref, pin))
+                consumed = j
+                continue
+        pins.append((last_word, pin))
+        consumed = j
+    return pins
+
+
+def parse_netlist(
+    path: str | Path,
+    known_refs: set[str] | None = None,
+) -> tuple[dict[str, str], dict[str, list[tuple[str, str]]]]:
+    """Parse PADS-PCB ASCII (``.asc``). Multi-word refs need ``known_refs`` from the BOM."""
+    parts: dict[str, str] = {}
+    nets: dict[str, list[tuple[str, str]]] = {}
+    section: str | None = None
+    current_net: str | None = None
+
+    for raw_line in Path(path).read_text().splitlines():
+        line = raw_line.strip()
+        if not line:
+            continue
+        if line.startswith("*"):
+            if line.startswith("*SIGNAL*"):
+                pass
+            elif line.startswith("*PART*"):
+                section, current_net = "part", None
+                continue
+            elif line.startswith("*NET*"):
+                section, current_net = "net", None
+                continue
+            elif line.startswith("*END*"):
+                break
+            else:
+                section, current_net = None, None
+                continue
+        if section == "part":
+            ref, footprint = _match_known_ref(line.split(), known_refs)
+            if ref:
+                parts[ref] = footprint
+        elif section == "net":
+            if line.startswith("*SIGNAL*"):
+                current_net = line.split("*SIGNAL*", 1)[1].strip()
+                nets.setdefault(current_net, [])
+            elif current_net is not None:
+                nets[current_net].extend(_pins_from_signal_line(line.split(), known_refs))
+
+    if not parts and nets:
+        for pins in nets.values():
+            for ref, _pin in pins:
+                parts.setdefault(ref, "")
+    return parts, nets
+
+
+def parse_netlist_any(
+    path: str | Path,
+    known_refs: set[str] | None = None,
+    *,
+    include_subdesigns: set[str] | None = None,
+) -> tuple[dict[str, str], dict[str, list[tuple[str, str]]], NetlistFormat]:
+    p = Path(path)
+    fmt = detect_netlist_format(p.read_bytes()[:2048])
+    if fmt == "edif":
+        from backend.periscopex.parsers_edif import parse_edif_netlist
+        parts, nets = parse_edif_netlist(p, include_subdesigns=include_subdesigns)
+    elif fmt.startswith("kicad"):
+        from backend.periscopex.parsers_kicad import parse_kicad
+        parts, nets, _ = parse_kicad(p)
+    else:
+        parts, nets = parse_netlist(p, known_refs=known_refs)
+    return parts, nets, fmt
+
+
+def validate_netlist(parts: dict, nets: dict) -> list[str]:
+    errors: list[str] = []
+    if not parts:
+        errors.append(
+            "No components found — is this a PADS-PCB (.asc), EDIF (.edn), "
+            "or KiCad netlist / .kicad_sch?"
+        )
+        return errors
+    if not nets:
+        errors.append("No nets found — the connectivity section (*NET*) is missing or empty")
+        return errors
+    refs_in_nets = {ref for pins in nets.values() for ref, _ in pins}
+    if not (set(parts) & refs_in_nets):
+        errors.append(
+            "No components are wired to any net — the connectivity section may be missing or malformed"
+        )
+    has_gnd = any(
+        n.upper() in _GND_EXACT or n.upper().endswith("GND") or n.upper().startswith("GND")
+        for n in nets
+    )
+    if not has_gnd:
+        errors.append(
+            "No ground net found (expected GND, AGND, DGND, VSS, etc.) — "
+            "this may not be a complete schematic netlist"
+        )
+    return errors
+
+
+def parse_bom(
+    path: str | Path,
+    *,
+    reference_col: str = "Reference",
+    mpn_col: str = "Manufacturer Part Number",
+) -> dict[str, dict]:
+    result: dict[str, dict] = {}
+    reader = csv.DictReader(Path(path).read_text().splitlines())
+    colnames = {n.lower() for n in (reader.fieldnames or []) if n}
+    has_dnp_col = bool(colnames & {"dnp", "dni", "fitted", "populate"})
+    has_variant_col = bool(colnames & {"variant"})
+
+    for row in reader:
+        refs_raw = row.get(reference_col, "")
+        value = row.get("Value", "") or row.get("Comment", "")
+        footprint = row.get("Footprint", "")
+        mpn = (row.get(mpn_col, "") or "").strip() or None
+        lcsc = row.get("LCSC", "") or None
+        datasheet_url = (row.get("Datasheet", "") or "").strip() or None
+        refs = [r.strip() for r in refs_raw.split(",") if r.strip()]
+        if not mpn:
+            mpn = (row.get("PNM", "") or "").strip() or None
+        if not mpn and any(re.match(r"^U\d", r, re.I) for r in refs):
+            mpn = (value or "").strip() or None
+        dnp_raw = (row.get("DNP") or row.get("DNI") or "").strip().lower()
+        fitted_raw = (row.get("Fitted") or row.get("Populate") or "").strip().lower()
+        variant = (row.get("Variant") or row.get("variant") or "").strip() or None
+        is_dnp = dnp_raw in _DNP_TRUE
+        if not is_dnp and fitted_raw in _FITTED_FALSE:
+            is_dnp = True
+        for ref in refs:
+            entry = {
+                "value": value,
+                "footprint": footprint,
+                "mpn": mpn,
+                "lcsc": lcsc,
+                "datasheet_url": datasheet_url,
+            }
+            if has_dnp_col:
+                entry["dnp"] = is_dnp
+            if has_variant_col:
+                entry["variant"] = variant
+            result[ref] = entry
+    return result
diff --git a/periscope/src/backend/periscopex/parsers_edif.py b/periscope/src/backend/periscopex/parsers_edif.py
new file mode 100644
index 0000000..4becac4
--- /dev/null
+++ b/periscope/src/backend/periscopex/parsers_edif.py
@@ -0,0 +1,465 @@
+"""Periscope EDIF 2.0.0 schematic netlist ingest (Siemens xDX Designer).
+
+Returns the same ``(parts, nets)`` maps as PADS ingest. This module never
+emits layout vias, pads, tracks, or zones — those come from ``parsers_kicad_pcb``.
+"""
+
+from __future__ import annotations
+
+import re
+from pathlib import Path
+from typing import Iterator
+
+
+# ---------------------------------------------------------------------------
+# Tokenizer + s-expression parser
+# ---------------------------------------------------------------------------
+
+
+class _Str(str):
+    """Marker subclass so quoted-string tokens are distinguishable from atoms.
+
+    Both atoms (e.g. ``viewRef``, ``&0441I3151``) and string values
+    (e.g. ``"U3"``, ``"GROUND"``) end up as Python ``str`` in the parsed
+    tree. EDIF rarely needs that distinction — string equality compares the
+    same way — but the marker is here in case future logic does.
+    """
+
+
+def _tokenize(text: str) -> Iterator[object]:
+    """Yield tokens: ``'('``, ``')'``, atom :class:`str`, or quoted :class:`_Str`."""
+    i, n = 0, len(text)
+    while i < n:
+        c = text[i]
+        if c.isspace():
+            i += 1
+            continue
+        if c == ";":
+            # EDIF doesn't really use comments, but tolerate them just in case
+            while i < n and text[i] != "\n":
+                i += 1
+            continue
+        if c in "()":
+            yield c
+            i += 1
+            continue
+        if c == '"':
+            j = i + 1
+            buf: list[str] = []
+            while j < n and text[j] != '"':
+                if text[j] == "\\" and j + 1 < n:
+                    buf.append(text[j + 1])
+                    j += 2
+                else:
+                    buf.append(text[j])
+                    j += 1
+            yield _Str("".join(buf))
+            i = j + 1
+            continue
+        j = i
+        while j < n and not text[j].isspace() and text[j] not in '()"':
+            j += 1
+        yield text[i:j]
+        i = j
+
+
+def _parse_sexp(tokens: list[object]) -> list:
+    """Build a nested list tree. Atoms / strings remain as ``str`` / ``_Str``."""
+    it = iter(tokens)
+
+    def parse_form() -> list:
+        result: list = []
+        for tok in it:
+            if tok == "(":
+                result.append(parse_form())
+            elif tok == ")":
+                return result
+            else:
+                result.append(tok)
+        return result  # unterminated at EOF — return what we have
+
+    top: list = []
+    for tok in it:
+        if tok == "(":
+            top.append(parse_form())
+        elif tok == ")":
+            raise ValueError("EDIF: unexpected ')' at top level")
+        else:
+            top.append(tok)
+    return top
+
+
+# ---------------------------------------------------------------------------
+# Tree walkers
+# ---------------------------------------------------------------------------
+
+
+def _walk(node: object, head: str) -> Iterator[list]:
+    """Yield every nested list whose first element equals ``head``."""
+    if not isinstance(node, list):
+        return
+    if node and isinstance(node[0], str) and node[0] == head:
+        yield node
+    for child in node:
+        if isinstance(child, list):
+            yield from _walk(child, head)
+
+
+def _node_id(node: list) -> str | None:
+    """Return the identifying atom of ``(<head> <id> ...)``.
+
+    Handles ``(<head> (rename &INTERNAL "display") ...)`` by returning
+    ``&INTERNAL`` — the form used elsewhere by ``cellRef`` / ``instanceRef``.
+    """
+    if len(node) < 2:
+        return None
+    second = node[1]
+    if isinstance(second, list) and len(second) >= 2 and second[0] == "rename":
+        return str(second[1])
+    if isinstance(second, str):
+        return str(second)
+    return None
+
+
+def _direct_property(node: list, prop_name: str) -> str | None:
+    """Return the string value of a ``(property NAME (string "X") ...)`` child.
+
+    Only looks at direct children of ``node`` — does not recurse into nested
+    forms — so it can be called on an ``instance`` without picking up
+    properties tucked inside ``portInstance`` blocks.
+    """
+    for child in node:
+        if not (isinstance(child, list) and len(child) >= 2 and child[0] == "property"):
+            continue
+        name_node = child[1]
+        if isinstance(name_node, list) and name_node and name_node[0] == "rename":
+            actual = str(name_node[1]) if len(name_node) >= 2 else ""
+        elif isinstance(name_node, str):
+            actual = str(name_node)
+        else:
+            continue
+        if actual != prop_name:
+            continue
+        for elem in child[2:]:
+            if isinstance(elem, list) and len(elem) >= 2 and elem[0] == "string":
+                return str(elem[1])
+    return None
+
+
+# ---------------------------------------------------------------------------
+# Stage extractors
+# ---------------------------------------------------------------------------
+
+
+def _build_cell_library(tree: list) -> dict[tuple[str, str], dict[str, str | None]]:
+    """Build ``(library_name, cell_id) -> {port_name: pin_type}``.
+
+    ``pin_type`` is ``"GROUND"`` (or any other ``Pin_Type`` property value) when
+    the cell tagged the port; ``None`` when no Pin_Type property is present.
+    Used to detect which nets are ground.
+    """
+    cells: dict[tuple[str, str], dict[str, str | None]] = {}
+    for lib in _walk(tree, "library"):
+        if len(lib) < 2:
+            continue
+        lib_name = str(lib[1])
+        for cell in _walk(lib, "cell"):
+            cell_id = _node_id(cell)
+            if not cell_id:
+                continue
+            port_map: dict[str, str | None] = {}
+            for port in _walk(cell, "port"):
+                if len(port) < 2:
+                    continue
+                port_name = str(port[1])
+                port_map[port_name] = _direct_property(port, "Pin_Type")
+            cells[(lib_name, cell_id)] = port_map
+    return cells
+
+
+def _find_cell_ref(node: list) -> tuple[str, str] | None:
+    """From an ``(instance ...)`` form, return ``(library_name, cell_id)`` from
+    its ``(viewRef VIEW (cellRef CELL (libraryRef LIB)))`` triple."""
+    for child in node:
+        if not (isinstance(child, list) and child and child[0] == "viewRef"):
+            continue
+        for sub in child[1:]:
+            if isinstance(sub, list) and len(sub) >= 2 and sub[0] == "cellRef":
+                cell_id = str(sub[1])
+                lib_name = ""
+                for sub2 in sub[2:]:
+                    if isinstance(sub2, list) and len(sub2) >= 2 and sub2[0] == "libraryRef":
+                        lib_name = str(sub2[1])
+                        break
+                return (lib_name, cell_id)
+    return None
+
+
+_SUBDESIGN_PREFIX = re.compile(r"^(&\d+)[IN]\d+")
+
+
+def _subdesign_id(internal_id: str | None) -> str | None:
+    """Extract the sub-design prefix from an EDIF instance or net ID.
+
+    Siemens xDX Designer emits internal IDs like ``&0441I2234`` (instance) or
+    ``&0441N2250`` (net), where ``&0441`` identifies the sub-design /
+    schematic view the symbol belongs to. Different sub-designs in one file
+    get different numeric prefixes; back-annotation, contents, and viewMap
+    all reuse the same prefix per design.
+
+    Returns ``None`` when the ID doesn't match the prefix scheme (bare-named
+    cells, named nets like ``+5V``, or exports from non-xDX tools). The
+    parser treats ``None`` as "shared / no sub-design" and includes those
+    forms in every selection.
+    """
+    if not internal_id:
+        return None
+    m = _SUBDESIGN_PREFIX.match(internal_id)
+    return m.group(1) if m else None
+
+
+def _build_instance_map(tree: list) -> dict[str, dict]:
+    """Walk every ``(instance ...)`` form. Skip back-annotation refs in viewMap.
+
+    Each entry: ``{cell_ref, port_pins, inline_designator, footprint, subdesign_id}``.
+    """
+    instances: dict[str, dict] = {}
+    for inst in _walk(tree, "instance"):
+        inst_id = _node_id(inst)
+        if not inst_id:
+            continue
+
+        cell_ref = _find_cell_ref(inst)
+
+        port_pins: dict[str, str] = {}
+        inline_des: str | None = None
+        for child in inst:
+            if not isinstance(child, list) or not child:
+                continue
+            if child[0] == "portInstance" and len(child) >= 2:
+                port_name = str(child[1])
+                for sub in child[2:]:
+                    if isinstance(sub, list) and len(sub) >= 2 and sub[0] == "designator":
+                        port_pins[port_name] = str(sub[1])
+                        break
+            elif child[0] == "designator" and len(child) >= 2 and inline_des is None:
+                inline_des = str(child[1])
+
+        instances[inst_id] = {
+            "cell_ref": cell_ref,
+            "port_pins": port_pins,
+            "inline_designator": inline_des,
+            "footprint": _direct_property(inst, "Cell_Name") or "",
+            "subdesign_id": _subdesign_id(inst_id),
+        }
+    return instances
+
+
+def _build_back_annotation(tree: list) -> dict[str, str]:
+    """``instance_id -> real_designator`` from ``viewMap.instanceBackAnnotate``."""
+    annotations: dict[str, str] = {}
+    for ann in _walk(tree, "instanceBackAnnotate"):
+        inst_id: str | None = None
+        des: str | None = None
+        for child in ann[1:]:
+            if not isinstance(child, list) or len(child) < 2:
+                continue
+            if child[0] == "instanceRef":
+                inst_id = str(child[1])
+            elif child[0] == "designator":
+                des = str(child[1])
+        if inst_id and des:
+            annotations[inst_id] = des
+    return annotations
+
+
+def _is_template_designator(des: str) -> bool:
+    """xDX exports unconfigured instances with templates like ``R?`` / ``U?``."""
+    return des.endswith("?")
+
+
+def _resolve_designators(
+    instances: dict[str, dict], back_anno: dict[str, str]
+) -> dict[str, str]:
+    """For each instance, pick the real designator. Drop template-only ones."""
+    resolved: dict[str, str] = {}
+    for inst_id, inst in instances.items():
+        inline = inst["inline_designator"]
+        annotated = back_anno.get(inst_id)
+        if inline and not _is_template_designator(inline):
+            resolved[inst_id] = inline
+        elif annotated and not _is_template_designator(annotated):
+            resolved[inst_id] = annotated
+        # else: unconfigured library symbol — skip
+    return resolved
+
+
+def _extract_nets(
+    tree: list,
+    instances: dict[str, dict],
+    designators: dict[str, str],
+    cell_lib: dict[tuple[str, str], dict[str, str | None]],
+    include_subdesigns: set[str] | None = None,
+) -> dict[str, list[tuple[str, str]]]:
+    """Walk every ``(net ...)`` form. Rename ground-touching nets to ``GND``.
+
+    When ``include_subdesigns`` is supplied, endpoints belonging to
+    excluded sub-designs are dropped. A net is kept iff it has at least one
+    surviving endpoint — bare-named nets (no sub-design prefix) survive as
+    long as any of their referenced instances does.
+    """
+    nets: dict[str, list[tuple[str, str]]] = {}
+    for net in _walk(tree, "net"):
+        if len(net) < 2:
+            continue
+        name_node = net[1]
+        if isinstance(name_node, list) and len(name_node) >= 3 and name_node[0] == "rename":
+            net_name = str(name_node[2])
+        elif isinstance(name_node, str):
+            net_name = str(name_node)
+        else:
+            continue
+
+        connections: list[tuple[str, str]] = []
+        touches_ground = False
+        for child in net[1:]:
+            if not (isinstance(child, list) and child and child[0] == "joined"):
+                continue
+            for ref in child[1:]:
+                if not (isinstance(ref, list) and len(ref) >= 2 and ref[0] == "portRef"):
+                    continue
+                port_name = str(ref[1])
+                inst_id: str | None = None
+                for sub in ref[2:]:
+                    if isinstance(sub, list) and len(sub) >= 2 and sub[0] == "instanceRef":
+                        inst_id = str(sub[1])
+                        break
+                if not inst_id or inst_id not in instances:
+                    continue
+                inst = instances[inst_id]
+                if include_subdesigns is not None:
+                    if inst["subdesign_id"] not in include_subdesigns:
+                        continue
+                pin = inst["port_pins"].get(port_name)
+                des = designators.get(inst_id)
+                if not pin or not des:
+                    continue
+                if inst["cell_ref"]:
+                    port_map = cell_lib.get(inst["cell_ref"], {})
+                    if port_map.get(port_name) == "GROUND":
+                        touches_ground = True
+                connections.append((des, pin))
+
+        if not connections:
+            continue
+        final_name = "GND" if touches_ground else net_name
+        nets.setdefault(final_name, []).extend(connections)
+    return nets
+
+
+# ---------------------------------------------------------------------------
+# Public entry point
+# ---------------------------------------------------------------------------
+
+
+def _parse_tree(path: str | Path) -> list:
+    text = Path(path).read_text(encoding="utf-8", errors="replace")
+    return _parse_sexp(list(_tokenize(text)))
+
+
+def parse_edif_netlist(
+    path: str | Path,
+    *,
+    include_subdesigns: set[str] | None = None,
+) -> tuple[dict[str, str], dict[str, list[tuple[str, str]]]]:
+    """Parse a Siemens xDX Designer EDIF 2.0.0 netlist (``.edn``).
+
+    Args:
+        path: file to parse.
+        include_subdesigns: when supplied, restrict the output to instances
+            whose ``&NNNN`` sub-design prefix is in this set. Instances with
+            no prefix (bare-named cells) are always kept. ``None`` (default)
+            includes every sub-design — same behavior as before this flag
+            existed.
+
+    Returns:
+        parts: ``{reference: footprint}`` (footprint from the instance's
+            ``Cell_Name`` property — typically a package size like ``"0402"``)
+        nets:  ``{net_name: [(component_ref, pin_number), ...]}``
+
+    Ground nets are renamed to ``"GND"`` based on ``Pin_Type=GROUND`` port
+    tags in the cell library; if no port tags ground (rare), net names stay
+    as the EDIF-generated ``$NN…`` strings and downstream validation will
+    surface the missing ground.
+    """
+    tree = _parse_tree(path)
+
+    cell_lib = _build_cell_library(tree)
+    instances = _build_instance_map(tree)
+    back_anno = _build_back_annotation(tree)
+    designators = _resolve_designators(instances, back_anno)
+
+    if include_subdesigns is not None:
+        # Drop excluded instances before nets are walked. Instances with
+        # subdesign_id=None (bare-named, no prefix) are always kept — they're
+        # shared between sub-designs in the xDX export and dropping them
+        # would orphan otherwise-included nets.
+        designators = {
+            iid: des
+            for iid, des in designators.items()
+            if instances[iid]["subdesign_id"] is None
+            or instances[iid]["subdesign_id"] in include_subdesigns
+        }
+
+    nets = _extract_nets(
+        tree, instances, designators, cell_lib,
+        include_subdesigns=include_subdesigns,
+    )
+
+    parts: dict[str, str] = {}
+    for inst_id, des in designators.items():
+        parts[des] = instances[inst_id]["footprint"]
+
+    return parts, nets
+
+
+def list_edif_subdesigns(path: str | Path) -> list[dict]:
+    """Return one entry per sub-design found in the file.
+
+    Each entry: ``{"id": "&0441", "instance_count": 21,
+    "designators": ["C1", "C2", ...]}``. Sub-designs are identified by the
+    ``&NNNN`` prefix on EDIF instance IDs; instances with no prefix (bare
+    cells, rare in xDX exports) are bundled under ``"id": None`` and are
+    always included regardless of the user's selection.
+
+    Designators are sorted naturally (R1 before R10) within each sub-design;
+    sub-designs themselves are sorted by their first BOM-style designator so
+    output is deterministic across runs.
+    """
+    tree = _parse_tree(path)
+    instances = _build_instance_map(tree)
+    back_anno = _build_back_annotation(tree)
+    designators = _resolve_designators(instances, back_anno)
+
+    by_sub: dict[str | None, list[str]] = {}
+    for iid, des in designators.items():
+        sub = instances[iid]["subdesign_id"]
+        by_sub.setdefault(sub, []).append(des)
+
+    def _key(des: str) -> tuple:
+        # Sort R1 before R10 — split on the first digit run.
+        head = des.rstrip("0123456789")
+        tail = des[len(head):]
+        return (head, int(tail) if tail.isdigit() else 0)
+
+    out: list[dict] = []
+    for sub, dlist in by_sub.items():
+        dlist.sort(key=_key)
+        out.append({
+            "id": sub,
+            "instance_count": len(dlist),
+            "designators": dlist,
+        })
+
+    out.sort(key=lambda e: (e["designators"][0] if e["designators"] else "", e["id"] or ""))
+    return out
diff --git a/tests/test_periscope_parsers_rewrite.py b/tests/test_periscope_parsers_rewrite.py
new file mode 100644
index 0000000..99deb74
--- /dev/null
+++ b/tests/test_periscope_parsers_rewrite.py
@@ -0,0 +1,43 @@
+"""Schematic parsers load from src; they do not classify PCB vias as pads."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+import backend.periscopex.parsers as parsers
+import backend.periscopex.parsers_edif as parsers_edif
+import backend.periscopex.parsers_kicad_pcb as pcb
+from backend.periscopex.parsers import detect_netlist_format, parse_netlist_any
+
+
+def test_schematic_parsers_are_src():
+    for mod, name in ((parsers, "parsers.py"), (parsers_edif, "parsers_edif.py")):
+        path = Path(mod.__file__).resolve()
+        assert path.name == name
+        assert "src" in path.parts
+        assert "Native Periscope overlay" not in path.read_text(encoding="utf-8")[:400]
+
+
+def test_pcb_parser_stays_native_kicad_pcb():
+    path = Path(pcb.__file__).resolve()
+    assert path.parts[-1] == "parsers_kicad_pcb.py"
+    assert "src" in path.parts
+    assert "_is_footprint_via" in path.read_text(encoding="utf-8")
+
+
+def test_detect_format_negative_pcb_is_not_edif_or_kicad_sch():
+    # A board file starts with (kicad_pcb …), not schematic markers.
+    sample = "(kicad_pcb (version 20240108)\n"
+    assert detect_netlist_format(sample) == "pads"  # unknown schematic → PADS sniff default
+
+
+def test_parse_netlist_any_pads_roundtrip(tmp_path: Path):
+    asc = tmp_path / "n.asc"
+    asc.write_text(
+        "*PADS-PCB*\n*PART*\nR1 0603\nU1 QFP48\n*NET*\n*SIGNAL* GND\nR1.1 U1.8\n*SIGNAL* 3V3\nU1.7\n*END*\n"
+    )
+    parts, nets, fmt = parse_netlist_any(asc)
+    assert fmt == "pads"
+    assert parts["R1"] == "0603"
+    assert ("R1", "1") in nets["GND"]
+    assert "GND" in nets