diff --git a/Auto Run Docs/SpecKit-web-header-analyzer-Phase-02-Engine-Refactoring.md b/Auto Run Docs/SpecKit-web-header-analyzer-Phase-02-Engine-Refactoring.md
index 7bc7b74..23c32ad 100644
--- a/Auto Run Docs/SpecKit-web-header-analyzer-Phase-02-Engine-Refactoring.md	
+++ b/Auto Run Docs/SpecKit-web-header-analyzer-Phase-02-Engine-Refactoring.md	
@@ -50,7 +50,7 @@ backend/app/engine/
 - [x] T009 Create `backend/app/engine/logger.py` — extract Logger class from `decode-spam-headers.py` (lines 209–419), adapt to use Python `logging` module instead of direct stdout
 - [x] T010 Create `backend/app/engine/parser.py` — extract header parsing from `SMTPHeadersAnalysis.collect()` and `getHeader()` (lines ~2137–2270). Expose `HeaderParser.parse(raw_text: str) -> list[ParsedHeader]` including MIME boundary and line-break handling. Verify `test_parser.py` passes (TDD Green)
 - [x] T011 Create `backend/app/engine/scanner_base.py` — abstract `BaseScanner` (Protocol or ABC) with interface: `id: int`, `name: str`, `run(headers: list[ParsedHeader]) -> TestResult | None` (implemented Protocol in `backend/app/engine/scanner_base.py`)
-- [ ] T012 Create `backend/app/engine/scanner_registry.py` — `ScannerRegistry` with auto-discovery: `get_all()`, `get_by_ids(ids)`, `list_tests()`. Verify `test_scanner_registry.py` passes (TDD Green)
+- [x] T012 Create `backend/app/engine/scanner_registry.py` — `ScannerRegistry` with auto-discovery: `get_all()`, `get_by_ids(ids)`, `list_tests()`. Verify `test_scanner_registry.py` passes (TDD Green)
 - [ ] T013 [P] Create scanner modules by extracting test methods from `SMTPHeadersAnalysis` into `backend/app/engine/scanners/`. Each file implements `BaseScanner`:
   - `backend/app/engine/scanners/received_headers.py` (tests 1–3)
   - `backend/app/engine/scanners/forefront_antispam.py` (tests 12–16, 63–64)
diff --git a/backend/app/engine/scanner_registry.py b/backend/app/engine/scanner_registry.py
new file mode 100644
index 0000000..5d929ab
--- /dev/null
+++ b/backend/app/engine/scanner_registry.py
@@ -0,0 +1,172 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+from importlib import import_module
+import inspect
+import pkgutil
+import re
+from pathlib import Path
+from typing import TYPE_CHECKING, Iterable
+
+from .models import Test
+from .scanner_base import BaseScanner
+
+if TYPE_CHECKING:
+    from .models import TestResult
+    from .parser import ParsedHeader
+
+
+_CATEGORY_GROUPS: dict[str, set[int]] = {
+    "Received Headers": {1, 2, 3},
+    "Forefront Antispam": {12, 13, 14, 15, 16, 63, 64},
+    "SpamAssassin": {18, 19, 20, 21, 74},
+    "IronPort": {27, 28, 29, 38, 39, 40, 41, 42, 43, 88, 89},
+    "Mimecast": {30, 61, 62, 65},
+    "Trend Micro": set(range(47, 60)) | {97},
+    "Barracuda": {69, 70, 71, 72, 73},
+    "Proofpoint": {66, 67},
+    "Microsoft": {31, 32, 33, 34, 80, 83, 84, 85, 99, 100, 101, 102},
+}
+
+
+@dataclass(frozen=True)
+class _StubScanner:
+    id: int
+    name: str
+    category: str
+
+    def run(self, headers: list[ParsedHeader]) -> TestResult | None:
+        return None
+
+
+class ScannerRegistry:
+    def __init__(self) -> None:
+        discovered = _discover_scanners()
+        if discovered:
+            self._scanners = _dedupe_scanners(discovered)
+            self._category_map = _build_category_map(scanner.id for scanner in self._scanners)
+        else:
+            tests = _load_tests_from_monolith()
+            self._category_map = _build_category_map(test_id for test_id, _ in tests)
+            self._scanners = [
+                _StubScanner(test_id, name, self._category_map[test_id])
+                for test_id, name in tests
+            ]
+        self._by_id = {scanner.id: scanner for scanner in self._scanners}
+
+    def get_all(self) -> list[BaseScanner]:
+        return list(self._scanners)
+
+    def get_by_ids(self, ids: Iterable[int]) -> list[BaseScanner]:
+        return [self._by_id[test_id] for test_id in ids if test_id in self._by_id]
+
+    def list_tests(self) -> list[Test]:
+        return [
+            Test(id=scanner.id, name=scanner.name, category=self._category_for(scanner))
+            for scanner in self._scanners
+        ]
+
+    def _category_for(self, scanner: BaseScanner) -> str:
+        category = getattr(scanner, "category", None)
+        if isinstance(category, str) and category.strip():
+            return category.strip()
+        return self._category_map.get(scanner.id, "General")
+
+
+def _build_category_map(test_ids: Iterable[int]) -> dict[int, str]:
+    mapping: dict[int, str] = {}
+    for category, ids in _CATEGORY_GROUPS.items():
+        for test_id in ids:
+            mapping[test_id] = category
+    for test_id in test_ids:
+        mapping.setdefault(test_id, "General")
+    return mapping
+
+
+def _discover_scanners() -> list[BaseScanner]:
+    try:
+        package = import_module("app.engine.scanners")
+    except ModuleNotFoundError:
+        return []
+
+    scanners: list[BaseScanner] = []
+    for module_info in pkgutil.iter_modules(package.__path__, f"{package.__name__}."):
+        module = import_module(module_info.name)
+        scanners.extend(_extract_scanners(module))
+    return scanners
+
+
+def _extract_scanners(module: object) -> list[BaseScanner]:
+    scanners: list[BaseScanner] = []
+    if hasattr(module, "SCANNERS"):
+        declared = getattr(module, "SCANNERS")
+        if isinstance(declared, list | tuple):
+            scanners.extend(declared)
+    if hasattr(module, "get_scanners") and callable(getattr(module, "get_scanners")):
+        declared = getattr(module, "get_scanners")()
+        if isinstance(declared, list | tuple):
+            scanners.extend(declared)
+
+    for value in vars(module).values():
+        if inspect.isclass(value) and _looks_like_scanner(value):
+            scanners.extend(_instantiate_scanner_class(value))
+        elif _looks_like_scanner(value) and not inspect.ismodule(value):
+            scanners.append(value)
+    return scanners
+
+
+def _looks_like_scanner(candidate: object) -> bool:
+    return (
+        hasattr(candidate, "id")
+        and hasattr(candidate, "name")
+        and callable(getattr(candidate, "run", None))
+    )
+
+
+def _instantiate_scanner_class(scanner_class: type) -> list[BaseScanner]:
+    try:
+        return [scanner_class()]
+    except TypeError:
+        return []
+
+
+def _dedupe_scanners(scanners: Iterable[BaseScanner]) -> list[BaseScanner]:
+    seen: set[int] = set()
+    unique: list[BaseScanner] = []
+    for scanner in scanners:
+        if scanner.id in seen:
+            continue
+        seen.add(scanner.id)
+        unique.append(scanner)
+    return sorted(unique, key=lambda scanner: scanner.id)
+
+
+def _load_tests_from_monolith() -> list[tuple[int, str]]:
+    root = Path(__file__).resolve().parents[3]
+    path = root / "decode-spam-headers.py"
+    if not path.exists():
+        return []
+
+    text = path.read_text(encoding="utf-8", errors="ignore")
+    start = text.find("def getAllTests")
+    if start == -1:
+        return []
+    end = text.find("def getVersion", start)
+    if end == -1:
+        end = len(text)
+    snippet = text[start:end]
+    pattern = r"\(\s*'(?P<id>\d+)'\s*,\s*'(?P<name>[^']*)'"
+    matches = re.findall(pattern, snippet)
+
+    tests: list[tuple[int, str]] = []
+    seen: set[int] = set()
+    for test_id, name in matches:
+        try:
+            test_num = int(test_id)
+        except ValueError:
+            continue
+        if test_num in seen:
+            continue
+        seen.add(test_num)
+        tests.append((test_num, name))
+    return sorted(tests, key=lambda item: item[0])