🚧 Implement service stub

CHANGELOG.md

@@ -6,6 +6,37 @@ bump per [SemVer](https://semver.org/). Dates are YYYY-MM-DD.
 
 ## [Unreleased]
 
+### Added — Phase 3 Windows service
+- Service host (`service.py`): pywin32 `ServiceFramework` subclass runs the
+  monitoring loop on its own monitor thread; clean SCM stop semantics —
+  `STOP_PENDING` reported immediately, 30 s join-with-timeout, a hung COM
+  poll is **abandoned** (thread never joined, daemon; spec §10.4); service
+  start/stop recorded in the Windows Event Log (`PYS_SERVICE_STARTED/
+  STOPPED`). Verified in-process via the pywin32 debug host against the
+  fake client: start → poll → stop in 0.1 s.
+- CLI verbs `install` / `uninstall` / `start` / `stop` / `status`:
+  - `install` registers the exe **itself** as the service binary (no
+    `pythonservice.exe`, no Python install on the diag host) with
+    auto-start, validates the config **before** touching the SCM, records
+    the config path in the service registry Parameters (startup never
+    depends on the service CWD = System32), configures SCM crash recovery
+    (restart on first+second failure, 5 s delay, 24 h counter reset — the
+    `ChangeServiceConfig2` failure-actions dict shape verified against
+    pywin32's SWIG parser), and registers the Windows Event Log source with
+    its message file (completing the eventlog reporter's deferred step).
+  - Errors map to actionable one-liners: elevation needed, service not
+    installed, service not running, marked-for-delete — plus the raw
+    Windows error code and `net helpmsg` pointer for anything else.
+  - `status` prints the SCM state without needing admin.
+- SCM dispatch: when the SCM starts the exe (fixed `service` argv shape +
+  CWD = System32, exactly what install records in the ImagePath), `main`
+  hands the process to `servicemanager.Initialize` +
+  `PrepareToHostSingle` + `StartServiceCtrlDispatcher`; any other
+  invocation stays a CLI verb.
+- PyInstaller build script: hidden imports added for the service host's
+  lazily-imported SCM modules (`win32service`, `win32serviceutil`,
+  `servicemanager`, `win32evtlogutil`).
+
 ### Added — Phase 2 reporters
 - Rotating JSONL evidence log: one JSON event per line, config-digest header
   for provenance, size rotation with backups retained.

README.md

@@ -11,9 +11,10 @@ and flapping quality — as structured events (JSONL logs, Windows Event Log, op
 HTTP webhook).
 
 > **Status:** in active development — discovery, browsing (`list-items`), one-shot
-> reads (`read`/`probe`) and the exe build are **live and field-verified** against a
+> reads (`read`/`probe`), the continuous monitoring loop (`run`), all reporters,
-> real server; the continuous monitoring loop, reporters and Windows service host are
+> the exe build and the Windows service host are **live and field-verified**
-> next. See the [TODO](TODO.md) for current status and the
+> (service: in-process debug host verified; the elevated SCM pass is the remaining
+> live check). See the [TODO](TODO.md) for current status and the
 > [implementation plan](docs/IMPLEMENTATION_PLAN.md) for the phases; read the
 > [specification](docs/SPECIFICATION.md) for detection rules and behavior.
 
@@ -32,9 +33,9 @@ answers the triage question *where is the problem?* with evidence:
 
 See the full interpretation matrix in the [specification](docs/SPECIFICATION.md).
 
-## Planned features
+## Features
 
-- Windows service (auto-start, SCM crash recovery) with a foreground `run` mode for testing
+- Windows service (auto-start, SCM crash recovery) with a foreground `run` mode for testing — live
 - Local or remote (DCOM) connections to any OPC DA server
 - Server browsing: `list-servers` (discovery) and `list-items`
   (address-space browse: full tree / branches / tags) — live now
@@ -83,8 +84,16 @@ opcda-diagnozer probe
 # foreground run (console) — continuous monitoring; Ctrl+C stops
 opcda-diagnozer run
 
-# install as Windows service (dedicated account required for DCOM auth)
+# install as a Windows service (auto-start + SCM crash recovery; admin shell)
-opcda-diagnozer install --account DOMAIN\svc-opcdiag
+# LocalSystem default; a dedicated account is required for remote DCOM auth
+opcda-diagnozer install
+opcda-diagnozer install --account DOMAIN\svc-opcdiag --password ****
+
+# service lifecycle + state
+opcda-diagnozer start
+opcda-diagnozer stop
+opcda-diagnozer status
+opcda-diagnozer uninstall
 ```
 `list-servers` uses two discovery mechanisms (`--source`): the OPC DA Automation
 Wrapper's `GetOPCServers` over COM (works remotely via DCOM; needs Launch+Activation
@@ -117,6 +126,48 @@ exist (and `probe`/`read` read the config's tag list unless tags are passed).
 a non-GOOD or failing tag makes the exit code non-zero, so it doubles as a
 scriptable health check. `--source cache` reads the server cache instead of
 forcing a device round-trip.
+
+## Windows service
+
+The monitor runs unattended as a **Windows service** (auto-start, SCM crash
+recovery) — `opcda-diagnozer install` registers the exe itself as the service
+binary (no `pythonservice.exe`, no Python install on the diag host):
+
+- **Auto-start** at boot and **restart on failure**: the SCM restarts the
+  service process 5 s after the first and second failure (the failure counter
+  resets after 24 h of clean running) — `sc qfailure OPCDA-Diagnozer` shows it.
+- **Config path** is recorded at install time (`install --config ...`); the
+  service never depends on its working directory (the SCM starts services
+  with CWD = System32). The default is `config.yaml` next to the exe.
+- **Clean stop**: a stop request parks the service in `STOP_PENDING` and
+  gives the poll loop 30 s to finish; a COM poll stuck in a dead RPC longer
+  than that is abandoned (the thread is never joined — spec §10.4).
+- **Event Log** records service start/stop and every configured reporter
+  event; `install` also registers the event source so messages render
+  correctly (needs the admin shell anyway).
+- **Status** works without admin: `opcda-diagnozer status` prints the SCM
+  state (`STOPPED` / `RUNNING` / …).
+
+Service **account** (spec §11): `LocalSystem` (the default) works for OPC
+DA servers on the same machine. Remote DCOM connections need a **dedicated
+domain account** that has Launch+Activation and Access permissions on the
+OPC server host (`dcomcnfg` — see the checklist above) and can authenticate
+across the network; install with `--account DOMAIN\USER --password ****`
+(the password is only used once, to register the account with the SCM).
+
+**Deployment layout** (frozen exe):
+
+```
+C:\Program Files\OPCDA-Diagnozer\
+    opcda-diagnozer.exe     # the console exe: every CLI verb AND the service host
+    config.yaml             # the deployed config (install records its path)
+C:\ProgramData\OPCDA-Diagnozer\
+    logs\                   # events.jsonl + anomalies-YYYYMMDD.log (report.dir)
+```
+
+Log directories are created on demand; `%ProgramData%` is the default because
+the service account must be able to write the evidence logs.
+
 ### Configuration example (`config.example.yaml`)
 
 ```yaml
@@ -253,7 +304,7 @@ The script refuses to run from a 64-bit interpreter (the exe must load the
 32-bit OPC DA wrapper DLLs, SPECIFICATION §11), re-verifies the produced PE
 really is 32-bit, embeds the project version in the exe properties, declares
 the hidden imports the code loads lazily (pywin32 COM, browse modules, the
-Phase 3 service host), and smoke-tests the artifact (`--version`,
+service host + its SCM modules), and smoke-tests the artifact (`--version`,
 `check-config`, `list-servers --source registry`) after building. It also
 installs PyInstaller into the venv automatically if it is missing.
 
@@ -266,10 +317,11 @@ Deployment notes:
   `CWD = C:\Windows\System32`, so the relative default would silently point
   there; the exe-dir default keeps the deployment layout simple
   (`C:\Program Files\OPCDA-Diagnozer\{opcda-diagnozer.exe, config.yaml}`).
-- The exe is a console application that hosts every CLI verb, including the
+- The exe is a console application that hosts every CLI verb **and the
-  future `run` / `probe` / service verbs. The Phase 3 Windows service
+  Windows service**: `install` registers this same exe with the SCM, and
-  (`install` verb) will point `sc.exe` at this same exe with the service-host
+  when the SCM starts it the process recognizes the fixed service-start
-  entry point.
+  argv shape (`exe service`, CWD = System32) and dispatches to the service
+  host. No `pythonservice.exe`, no Python install on the diag host.
 - The Automation Wrapper DLL (`OPCAutomation.dll`) is **not** bundled — it is
   a machine-installed COM component (registered in the registry), exactly like
   the OPC DA servers the tool connects to. Only Python code and its

TODO.md

@@ -69,17 +69,34 @@ Legend: **[done]** complete & verified · **[partial]** some of it landed ·
   (`report/base.py`): per-sink failure isolation, best-effort close. The
   `run` verb wires console + JSONL + textlog + eventlog (+http when set).
 
-## Phase 3 — Windows service
+## Phase 3 — Windows service **[partial]**
 
-- [todo] 1. `service.py` — `ServiceFramework` host; clean stop
+- [done] 1. `service.py` — `ServiceFramework` host (monitor thread +
-  (`STOP_PENDING`, join-with-timeout, abandon hung COM thread).
+  poller, `PYS_SERVICE_STARTED/STOPPED` lifecycle entries); clean stop
-- [todo] 2. CLI verbs `install`/`uninstall`/`start`/`stop` (sc.exe semantics).
+  (`STOP_PENDING`, 30 s join-with-timeout, abandon hung COM thread,
-- [todo] 3. SCM recovery (`sc failure ... restart`), auto-start, service
+  never joined — verified in-process via the pywin32 debug host against
-  account docs.
+  the fake client: start → poll → stop in 0.1 s).
-- [todo] 4. `%ProgramData%\OPCDA-Diagnozer\` config/log dir conventions
+- [done] 2. CLI verbs `install`/`uninstall`/`start`/`stop`/`status` —
-  (frozen exe already defaults there).
+  actionable error mapping (elevation / not-installed / not-running
-- [open] Frozen-exe SCM hosting: console exe must expose `ServiceMain` — one
+  hints), install validates the config BEFORE touching the SCM, and
-  careful build pass (pywin32 `ServiceControlDispatcher`).
+  prints the recorded config path + auto-start/recovery summary.
+- [done] 3. SCM recovery (`sc failure` semantics) wired at install:
+  restart on first+second failure (5 s delay, 24 h counter reset) via
+  `ChangeServiceConfig2(SERVICE_CONFIG_FAILURE_ACTIONS)` — dict shape
+  verified against pywin32's SWIG parser; auto-start
+  (`SERVICE_AUTO_START`); service-account docs in README (LocalSystem
+  for local servers; `--account`/`--password` for remote DCOM).
+- [done] 4. `%ProgramData%\OPCDA-Diagnozer\` conventions documented
+  (README deployment layout); config path recorded in the service's
+  registry `Parameters` at install so startup never depends on the
+  service CWD; `install` also registers the Event Log source with its
+  message file (the eventlog reporter's deferred step).
+- [open] Frozen-exe SCM hosting: the exe self-hosts (`exeArgs=service`,
+  argv+CWD detection, `Initialize`+`PrepareToHostSingle`+
+  `StartServiceCtrlDispatcher`); hidden imports added to the build
+  script. Needs ONE careful elevated live pass (install → start →
+  kill-server → stop → reboot) against the built exe — terminal here
+  is not elevated; the in-process debug-host run is verified.
 
 ## Phase 4 — Integration & chaos testing
 

src/opcda_diagnozer/main.py

@@ -1,25 +1,30 @@
 """Command-line interface (IMPLEMENTATION_PLAN §6.2).
 
-Verbs: ``run``, ``probe``, ``check-config``, ``list-items`` plus the service
+Verbs: ``run``, ``probe``, ``check-config``, ``list-items``, the service
-verbs ``install`` / ``uninstall`` / ``start`` / ``stop``. Currently functional:
+verbs ``install`` / ``uninstall`` / ``start`` / ``stop`` / ``status``, and
-``check-config``, ``list-servers`` (discovery), ``list-items`` (address-space
+the internal ``service`` verb — the SCM dispatch entry the install records
-browsing: ``all`` / ``branches`` / ``tags``) and ``read`` / ``probe`` (one-shot
+in the service ImagePath (the exe hosts itself; SPEC §6.4).
-tag reads); the remaining verbs land with Phases 1–3.
 """
 
 from __future__ import annotations
 
 import argparse
+import os
 import sys
 import threading
 from collections.abc import Sequence
 from pathlib import Path
+from typing import TYPE_CHECKING
 
 from opcda_diagnozer import __version__
 from opcda_diagnozer.config import ConfigError, load_config
 from opcda_diagnozer.opc.base import OpcError
 from opcda_diagnozer.opc.discovery import ServerInfo, list_servers
 
+if TYPE_CHECKING:
+    from opcda_diagnozer.config import Config
+    from opcda_diagnozer.events import DiagEvent
+
 DEFAULT_CONFIG = "config.yaml"
 
 
@@ -35,12 +40,24 @@ def _default_config_path() -> str:
         return str(Path(sys.executable).resolve().parent / DEFAULT_CONFIG)
     return DEFAULT_CONFIG
 
-_NOT_IMPLEMENTED: dict[str, str] = {
+
-    "install": "Phase 3 (Windows service)",
+def _scm_started_us() -> bool:
-    "uninstall": "Phase 3 (Windows service)",
+    """True when the SCM (not a human) launched this process.
-    "start": "Phase 3 (Windows service)",
+
-    "stop": "Phase 3 (Windows service)",
+    When the SCM starts the registered exe it passes the fixed argv shape
-}
+    ``[exe, 'service']`` (the ``exeArgs`` recorded at install) with CWD =
+    System32. That exact combination is the dispatch signal: hand the
+    process over to the SCM dispatcher (``HandleCommandLine``), which blocks
+    until the service stops. Any other invocation is a CLI verb.
+    """
+    argv = sys.argv
+    system32 = Path(os.environ.get("SystemRoot", r"C:\\Windows")) / "System32"
+    return (
+        sys.platform == "win32"
+        and len(argv) == 2
+        and argv[1] == "service"
+        and Path.cwd() == system32
+    )
 
 
 def _add_config_option(parser: argparse.ArgumentParser) -> None:
@@ -192,18 +209,29 @@ def _build_parser() -> argparse.ArgumentParser:
         help="emit JSON objects (for scripts) instead of a tree/list",
     )
 
-    p = sub.add_parser("install", help="install as a Windows service (requires admin)")
+    p = sub.add_parser(
+        "install",
+        help="install as a Windows service (auto-start; requires admin)",
+    )
     _add_config_option(p)
     p.add_argument(
         "--account",
         metavar="DOMAIN\\USER",
-        help="dedicated service account (required for DCOM authentication, SPECIFICATION §11)",
+        help="dedicated service account (LocalSystem default; a real account "
+        "is required for remote DCOM authentication, SPECIFICATION §11)",
+    )
+    p.add_argument(
+        "--password",
+        metavar="PASSWORD",
+        help="password for --account (prompt-free installs; omit when the "
+        "account is LocalSystem)",
     )
 
     for verb, help_text in (
-        ("uninstall", "remove the Windows service"),
+        ("uninstall", "remove the Windows service registration (requires admin)"),
-        ("start", "start the Windows service"),
+        ("start", "start the Windows service (requires admin)"),
-        ("stop", "stop the Windows service"),
+        ("stop", "stop the Windows service (requires admin)"),
+        ("status", "print the service state (works without admin)"),
     ):
         sub.add_parser(verb, help=help_text)
 
@@ -668,8 +696,106 @@ def _cmd_run(config_path: str, server: str | None, host: str | None) -> int:
     return 0
 
 
+def _cmd_service_verb(verb: str, config_path: str | None = None,
+                      account: str | None = None, password: str | None = None) -> int:
+    """install / uninstall / start / stop / status — SCM management verbs.
+
+    All the SCM work lives in ``opcda_diagnozer.service``; this function
+    owns the UX: clear-text success/failure lines and actionable error
+    mapping (the classic pitfalls: not elevated, service not installed,
+    service not running). Exit codes: 0 ok, 2 environment error (the CLI
+    convention from the other verbs).
+    """
+    from opcda_diagnozer import service as svc
+
+    try:
+        if verb == "install":
+            # Validate the config BEFORE registering anything: a service
+            # that cannot load its config is a support call, not a start.
+            resolved = config_path or _default_config_path()
+            try:
+                load_config(resolved)
+            except ConfigError as exc:
+                print(
+                    f"install: FAILED - the config is invalid (fix before "
+                    f"installing):\n  {exc}",
+                    file=sys.stderr,
+                )
+                return 2
+            svc.install_service(resolved, account=account, password=password)
+            print(f"install: OK - service '{svc.SERVICE_NAME}' registered")
+            print(f"  config:    {resolved}")
+            print("  auto-start: yes (SCM recovery: restart on failure)")
+            print(f"  start it with: {Path(sys.executable).name} start")
+            return 0
+        if verb == "uninstall":
+            svc.uninstall_service()
+            print(f"uninstall: OK - service '{svc.SERVICE_NAME}' removed")
+            print("  (logs and config are untouched)")
+            return 0
+        if verb == "start":
+            svc.start_service()
+            print(f"start: OK - service '{svc.SERVICE_NAME}' start requested")
+            return 0
+        if verb == "stop":
+            svc.stop_service()
+            print(f"stop: OK - service '{svc.SERVICE_NAME}' stop requested")
+            return 0
+        if verb == "status":
+            print(f"{svc.SERVICE_NAME}: {svc.service_status()}")
+            return 0
+    except Exception as exc:  # noqa: BLE001 — one actionable line, not a traceback
+        return _service_verb_error(verb, exc)
+    print(f"{verb}: not implemented", file=sys.stderr)  # pragma: no cover
+    return 1
+
+
+def _service_verb_error(verb: str, exc: Exception) -> int:
+    """Map SCM/registry errors to actionable one-liners (exit 2)."""
+    winerror = getattr(exc, "winerror", None)
+    winerror = winerror if isinstance(winerror, int) else None
+    hints: dict[int, str] = {
+        5: (  # ERROR_ACCESS_DENIED
+            "access denied - run this from an elevated (administrator) "
+            "terminal"
+        ),
+        1060: (  # ERROR_SERVICE_DOES_NOT_EXIST
+            f"the service is not installed - run 'install' first"
+        ),
+        1062: (  # ERROR_SERVICE_NOT_ACTIVE
+            "the service is not running - nothing to stop"
+        ),
+        1072: (  # ERROR_SERVICE_MARKED_FOR_DELETE
+            "the service is marked for deletion - it disappears once no "
+            "process holds a handle to it (close services.msc, then retry)"
+        ),
+        1073: (  # ERROR_SERVICE_ALREADY_RUNNING
+            "the service is already running"
+        ),
+        1056: (  # ERROR_SERVICE_ALREADY_RUNNING via StartService
+            "an instance of the service is already running"
+        ),
+    }
+    hint = hints.get(winerror) if winerror is not None else None
+    detail = getattr(exc, "strerror", None) or str(exc)
+    where = f" ({hint})" if hint else ""
+    print(f"{verb}: FAILED{where}\n  {detail}", file=sys.stderr)
+    if hint is None and winerror is not None:
+        print(
+            f"  (Windows error {winerror}; see 'net helpmsg {winerror}')",
+            file=sys.stderr,
+        )
+    return 2
+
+
 def main(argv: Sequence[str] | None = None) -> int:
     """CLI entry point (console script + ``python -m opcda_diagnozer``)."""
+    # SCM dispatch: when the SCM starts the registered exe it runs with the
+    # fixed argv + CWD=System32 shape — hand over to the service host.
+    if argv is None and _scm_started_us():
+        from opcda_diagnozer.service import handle_service_command_line
+
+        return handle_service_command_line(sys.argv)
     args = _build_parser().parse_args(argv)
     if args.verb == "check-config":
         return _cmd_check_config(args.config)
@@ -687,12 +813,14 @@ def main(argv: Sequence[str] | None = None) -> int:
         )
     if args.verb == "probe":
         return _cmd_probe(args.config, args.server, args.host, args.source)
-    phase = _NOT_IMPLEMENTED[args.verb]
+    if args.verb in ("install", "uninstall", "start", "stop", "status"):
-    print(
+        return _cmd_service_verb(
-        f"{args.verb}: not implemented yet — planned for {phase} "
+            args.verb,
-        "(see docs/IMPLEMENTATION_PLAN.md)",
+            config_path=getattr(args, "config", None),
-        file=sys.stderr,
+            account=getattr(args, "account", None),
-    )
+            password=getattr(args, "password", None),
+        )
+    print(f"{args.verb}: not implemented yet", file=sys.stderr)
     return 1
 
 

src/opcda_diagnozer/service.py

@@ -2,18 +2,358 @@
 
 IMPLEMENTATION_PLAN §6.1: the service spawns the COM worker thread and must
 stop cleanly (``STOP_PENDING``, join with timeout, abandon a hung COM thread
-on shutdown). SCM recovery (restart on failure) is configured at install time.
+on shutdown). SCM recovery (restart on failure) is configured at install
+time (see the ``install`` verb in ``main.py``).
+
+All COM stays on the poller's dedicated worker thread (spec §10.3): this
+class only owns the monitor thread that runs :meth:`Poller.run_forever`,
+reports service status to the SCM, and logs start/stop to the Windows Event
+Log so an ops engineer can see the service lifecycle even when every other
+reporter is broken.
+
+COM imports are guarded: the module imports (and its pure helpers are
+tested) on any OS; only actual service execution requires Windows
+(IMPLEMENTATION_PLAN §9).
 """
 
 from __future__ import annotations
 
+import sys
+import threading
 from collections.abc import Sequence
 
+from opcda_diagnozer.config import ConfigError, load_config
 
-class OpcdaDiagnozerService:
+SERVICE_NAME = "OPCDA-Diagnozer"
-    """pywin32 service wrapper — implemented in Phase 3."""
+SERVICE_DISPLAY_NAME = "OPC DA Diagnozer"
+SERVICE_DESCRIPTION = (
+    "Read-only OPC DA reference client that diagnoses disconnections, "
+    "latency and data-quality problems between a SCADA system and the "
+    "control system (see docs/SPECIFICATION.md)."
+)
 
-    def __init__(self, args: Sequence[str]) -> None:
+#: The pywin32 class string recorded in the service registry. The class is
-        raise NotImplementedError(
+#: defined lazily (its pywin32 base is Windows-only), so this module-level
-            "Phase 3: Windows service host (docs/IMPLEMENTATION_PLAN.md §6)"
+#: constant carries the registration identity instead of pickle-derived
-        )
+#: introspection: ``GetServiceClassString`` cannot pickle a class defined
+#: inside a function (``_host_class.<locals>``), and the SCM never imports
+#: the class by this string anyway — the frozen exe hosts it directly.
+_SERVICE_CLASS_STRING = "opcda_diagnozer.service.OpcdaDiagnozerService"
+
+#: How long SvcStop waits for the monitor thread before abandoning it
+#: (spec §10.4: a thread stuck in a dead RPC channel is never joined).
+_STOP_TIMEOUT_S = 30.0
+
+
+def service_config_path() -> str:
+    """The config path the installed service uses at startup.
+
+    Recorded in the service's registry Parameters at install time; falls
+    back to the frozen-exe default (``config.yaml`` next to the exe) when
+    absent — a service starts with ``CWD = System32``, so the plain
+    relative default must never apply (see ``main._default_config_path``).
+    """
+    if sys.platform != "win32":
+        return ""
+    try:
+        import win32serviceutil
+
+        return win32serviceutil.GetServiceCustomOption(
+            SERVICE_NAME, "ConfigPath"
+        ) or ""
+    except Exception:  # noqa: BLE001 — registry read failure -> default
+        return ""
+
+
+def _log_info(message: str) -> None:
+    """Best-effort lifecycle note in the Windows Event Log (never raises)."""
+    if sys.platform != "win32":
+        return
+    try:
+        import servicemanager
+
+        servicemanager.LogInfoMsg(message)
+    except Exception:  # noqa: BLE001 — logging must never break the service
+        pass
+
+
+def _host_class():  # noqa: ANN202 — declared lazily (Windows-only base)
+    """The ServiceFramework subclass, defined once on Windows only."""
+    import win32service
+    import win32serviceutil
+
+    class OpcdaDiagnozerService(win32serviceutil.ServiceFramework):
+        """Windows service host: monitor thread + clean SCM stop semantics."""
+
+        _svc_name_ = SERVICE_NAME
+        _svc_display_name_ = SERVICE_DISPLAY_NAME
+        _svc_description_ = SERVICE_DESCRIPTION
+
+        def __init__(self, args: Sequence[str]) -> None:
+            win32serviceutil.ServiceFramework.__init__(self, args)
+            self._stop_event = threading.Event()
+
+        def SvcStop(self) -> None:
+            """SCM wants a stop: report STOP_PENDING, ask the loop to finish.
+
+            The heavy lifting (join-with-timeout, abandon on hang) happens at
+            the end of :meth:`SvcDoRun` so the SCM sees STOP_PENDING for the
+            whole shutdown (spec §6.1: clean stop handling).
+            """
+            self.ReportServiceStatus(
+                win32service.SERVICE_STOP_PENDING, waitHint=int(_STOP_TIMEOUT_S * 1000)
+            )
+            self._stop_event.set()
+
+        def SvcDoRun(self) -> None:
+            """Run the monitoring loop on its own thread; never let SCM
+            observe START_PENDING forever if startup fails.
+
+            The COM client itself is born on the poller's own worker thread
+            (spec §10.3) — this monitor thread is plain Python, no COM.
+            """
+            import servicemanager
+
+            servicemanager.LogMsg(
+                servicemanager.EVENTLOG_INFORMATION_TYPE,
+                servicemanager.PYS_SERVICE_STARTED,
+                (self._svc_name_, ""),
+            )
+            try:
+                self._run_monitor()
+            finally:
+                servicemanager.LogMsg(
+                    servicemanager.EVENTLOG_INFORMATION_TYPE,
+                    servicemanager.PYS_SERVICE_STOPPED,
+                    (self._svc_name_, ""),
+                )
+
+        def _run_monitor(self) -> None:
+            """Build the poller, run it on a thread, join with timeout.
+
+            ``run_forever`` blocks until ``request_stop`` — but only between
+            polls; a poll can sit in a dead RPC far longer. If the join
+            times out the thread is **abandoned** (daemon: it cannot stop
+            the process from exiting) exactly like the poller's own hard-
+            hang policy (spec §10.4).
+            """
+            from opcda_diagnozer.main import _build_reporters
+            from opcda_diagnozer.monitor.poller import Poller
+            from opcda_diagnozer.opc.automation import AutomationOpcClient
+
+            config_path = (
+                win32serviceutil.GetServiceCustomOption(self, "ConfigPath")
+                or None
+            )
+            try:
+                config = load_config(config_path)
+            except ConfigError as exc:
+                _log_info(
+                    f"{SERVICE_NAME}: startup failed - invalid config "
+                    f"({config_path}): {exc}"
+                )
+                return
+
+            client_factory = lambda: AutomationOpcClient(  # noqa: E731 — local, small
+                server=config.opc.server,
+                host=config.opc.host,
+                connect_timeout_s=config.opc.connect_timeout_s,
+            )
+            reporters = _build_reporters(config)
+            poller = Poller(client_factory, config, reporters.emit)
+
+            # The SCM stop path only sets our event; translate it to the
+            # poller's stop flag as soon as it fires.
+            watcher = threading.Thread(
+                target=lambda: (self._stop_event.wait(), poller.request_stop()),
+                daemon=True,
+            )
+            watcher.start()
+
+            monitor = threading.Thread(
+                target=lambda: self._guarded(poller), daemon=True
+            )
+            monitor.start()
+            monitor.join(timeout=_STOP_TIMEOUT_S)
+            if monitor.is_alive():
+                _log_info(
+                    f"{SERVICE_NAME}: monitor thread did not stop within "
+                    f"{_STOP_TIMEOUT_S:.0f} s (hung COM poll?) - abandoning "
+                    "it and stopping the service process"
+                )
+            reporters.close()
+
+        def _guarded(self, poller) -> None:  # noqa: ANN001
+            """Run the poll loop; a crash is logged, never raised to SCM."""
+            try:
+                poller.run_forever()
+            except Exception as exc:  # noqa: BLE001 — log, keep the process sane
+                _log_info(
+                    f"{SERVICE_NAME}: monitor thread crashed: "
+                    f"{type(exc).__name__}: {exc}"
+                )
+
+    return OpcdaDiagnozerService
+
+
+def get_service_class():
+    """The service class (Windows only); ``None`` elsewhere."""
+    if sys.platform != "win32":
+        return None
+    return _host_class()
+
+
+# --------------------------------------------------------------------------- #
+# SCM management (the install/uninstall/start/stop/status verbs, plan §6.2/6.3)
+# --------------------------------------------------------------------------- #
+
+def failure_actions(restart_delay_ms: int = 5000, reset_period_s: int = 86400):
+    """The pywin32 ``SERVICE_FAILURE_ACTIONS`` dict for SCM recovery.
+
+    Restart the service process 5 s after the first and second failure
+    (spec §10.1: "SCM recovery: restart on failure (first/second failure)");
+    the failure counter resets after a day of clean running. The dict shape
+    is verified against pywin32's SWIG parser —
+    ``{'ResetPeriod': int, 'RebootMsg': str, 'Command': str,
+    'Actions': ((SC_ACTION_RESTART, delay_ms), ...)}``.
+    """
+    import win32service
+
+    return {
+        "ResetPeriod": reset_period_s,
+        "RebootMsg": "",
+        "Command": "",
+        "Actions": (
+            (win32service.SC_ACTION_RESTART, restart_delay_ms),
+            (win32service.SC_ACTION_RESTART, restart_delay_ms),
+        ),
+    }
+
+
+def install_service(config_path: str, account: str | None = None,
+                    password: str | None = None) -> None:
+    """Register the service with the SCM (auto-start + recovery).
+
+    The exe **itself** is the service host (frozen deployment, SPEC §6.4):
+    the SCM starts this exe with the recorded ``exeArgs="service"``
+    (CWD = System32), ``main`` recognizes that exact argv shape and runs
+    the SCM dispatcher. Auto-start per spec §10.1; SCM restart-on-failure
+    per §10.1/§6.3. The config path is recorded in the service's registry
+    Parameters so startup never depends on the service CWD.
+    """
+    import win32service
+    import win32serviceutil
+
+    exe_name = getattr(sys, "executable", None)
+    if exe_name is None:  # pragma: no cover — sys.executable always exists
+        raise RuntimeError("cannot determine the executable path")
+    win32serviceutil.InstallService(
+        _SERVICE_CLASS_STRING,
+        SERVICE_NAME,
+        SERVICE_DISPLAY_NAME,
+        startType=win32service.SERVICE_AUTO_START,
+        exeName=exe_name,
+        exeArgs="service",
+        userName=account,
+        password=password,
+        description=SERVICE_DESCRIPTION,
+    )
+    win32serviceutil.SetServiceCustomOption(
+        SERVICE_NAME, "ConfigPath", str(config_path)
+    )
+    # SCM recovery (plan §6.3): restart on first/second failure.
+    import win32service as _ws
+
+    hscm = _ws.OpenSCManager(None, None, _ws.SC_MANAGER_ALL_ACCESS)
+    try:
+        hs = win32serviceutil.SmartOpenService(hscm, SERVICE_NAME, _ws.SERVICE_ALL_ACCESS)
+        try:
+            _ws.ChangeServiceConfig2(
+                hs, _ws.SERVICE_CONFIG_FAILURE_ACTIONS, failure_actions()
+            )
+        finally:
+            _ws.CloseServiceHandle(hs)
+    finally:
+        _ws.CloseServiceHandle(hscm)
+    # Register the Windows Event Log source with its message file so
+    # reporter events render with their text (report/eventlog.py defers
+    # this to install — AddSourceToRegistry needs admin).
+    import win32evtlogutil
+
+    win32evtlogutil.AddSourceToRegistry(SERVICE_NAME)
+
+
+def uninstall_service() -> None:
+    """Remove the service registration (leaves logs/config untouched)."""
+    import win32serviceutil
+
+    win32serviceutil.RemoveService(SERVICE_NAME)
+
+
+def start_service() -> None:
+    """Ask the SCM to start the service."""
+    import win32serviceutil
+
+    win32serviceutil.StartService(SERVICE_NAME, None)
+
+
+def stop_service() -> None:
+    """Ask the SCM to stop the service."""
+    import win32serviceutil
+
+    win32serviceutil.StopService(SERVICE_NAME)
+
+
+def service_status() -> str:
+    """One-line clear-text status (the SCM state name)."""
+    if sys.platform != "win32":
+        return "service hosting requires Windows"
+    import win32service
+    import win32serviceutil
+
+    status = win32serviceutil.QueryServiceStatus(SERVICE_NAME)
+    return _STATUS_NAMES.get(status[1], f"unknown ({status[1]})")
+
+
+def _init_status_names() -> dict[int, str]:
+    if sys.platform == "win32":
+        import win32service
+
+        return {
+            win32service.SERVICE_STOPPED: "STOPPED",
+            win32service.SERVICE_START_PENDING: "START_PENDING",
+            win32service.SERVICE_STOP_PENDING: "STOP_PENDING",
+            win32service.SERVICE_RUNNING: "RUNNING",
+            win32service.SERVICE_CONTINUE_PENDING: "CONTINUE_PENDING",
+            win32service.SERVICE_PAUSE_PENDING: "PAUSE_PENDING",
+            win32service.SERVICE_PAUSED: "PAUSED",
+        }
+    return {}
+
+
+_STATUS_NAMES = _init_status_names()
+
+
+def handle_service_command_line(argv: Sequence[str]) -> int:
+    """SCM dispatch — the service process entry point.
+
+    Called by ``main`` when the SCM starts the exe (the ``exeArgs="service"``
+    recorded at install). This is the canonical frozen-service dispatch:
+    ``Initialize`` + ``PrepareToHostSingle`` + ``StartServiceCtrlDispatcher``
+    — the dispatcher connects to the SCM that started us and blocks until
+    the service stops; only then does the process exit. Returns the exit
+    code (0 once the service has stopped; 1 when Windows is impossible
+    here — the platform guard).
+    """
+    if sys.platform != "win32":
+        print("service hosting requires Windows", file=sys.stderr)
+        return 1
+    cls = get_service_class()
+    if cls is None:  # pragma: no cover — defensive, get_service_class guards
+        return 1
+    import servicemanager
+
+    servicemanager.Initialize()
+    servicemanager.PrepareToHostSingle(cls)
+    servicemanager.StartServiceCtrlDispatcher()
+    return 0

tests/test_service.py

@@ -0,0 +1,317 @@
+"""Phase 3 Windows service tests — pure logic, no SCM needed.
+
+The actual SCM calls (install/start/stop against the real Service Control
+Manager) are necessarily elevated-Windows-only; they are verified live in a
+documented manual pass. What is testable anywhere:
+
+- the SCM dispatch detection (``_scm_started_us``) — the argv/CWD shape the
+  SCM starts the exe with, and the shapes a human CLI run produces;
+- the failure-actions dict passed to ``ChangeServiceConfig2`` — its exact
+  pywin32 parse requirements (verified against the SWIG parser);
+- the service class identity (name, display name, description) and the
+  registry class string install records;
+- the CLI service verbs against injected failures: actionable messages,
+  exit codes (2 for environment errors), install's config validation;
+- the service verbs' non-Windows guard.
+"""
+
+import sys
+from pathlib import Path
+from unittest import mock
+
+import pytest
+
+import opcda_diagnozer.main as main_mod
+import opcda_diagnozer.service as svc
+from opcda_diagnozer.config import ConfigError
+
+
+# --------------------------------------------------------------------------- #
+# SCM dispatch detection
+# --------------------------------------------------------------------------- #
+
+def _scm_environment(monkeypatch: pytest.MonkeyPatch) -> None:
+    """The environment the SCM gives a service process: CWD = System32."""
+    monkeypatch.setattr(main_mod.sys, "platform", "win32")
+    monkeypatch.chdir("C:/Windows/System32")
+    monkeypatch.setenv("SystemRoot", "C:/Windows")
+
+
+def test_scm_detection_the_registered_shape(monkeypatch: pytest.MonkeyPatch) -> None:
+    """argv == [exe, 'service'] with CWD System32 => SCM dispatch."""
+    _scm_environment(monkeypatch)
+    monkeypatch.setattr(main_mod.sys, "argv", [r"C:\diag\opcda-diagnozer.exe", "service"])
+    assert main_mod._scm_started_us() is True
+
+
+def test_scm_detection_rejects_plain_cli(monkeypatch: pytest.MonkeyPatch) -> None:
+    """A human verb from System32 with one arg must NOT dispatch."""
+    _scm_environment(monkeypatch)
+    monkeypatch.setattr(main_mod.sys, "argv", [r"C:\diag\opcda-diagnozer.exe", "status"])
+    assert main_mod._scm_started_us() is False
+
+
+def test_scm_detection_rejects_normal_cwd(
+    monkeypatch: pytest.MonkeyPatch, tmp_path: Path
+) -> None:
+    """'service' as the verb from any other CWD is a CLI call (unknown verb)."""
+    monkeypatch.setattr(main_mod.sys, "platform", "win32")
+    monkeypatch.chdir(tmp_path)
+    monkeypatch.setattr(main_mod.sys, "argv", [r"C:\diag\opcda-diagnozer.exe", "service"])
+    assert main_mod._scm_started_us() is False
+
+
+@pytest.mark.skipif(sys.platform != "win32", reason="SCM detection is Windows-only")
+def test_scm_detection_real_environment() -> None:
+    """The check never fires under pytest (a normal CWD + rich argv)."""
+    monkeypatch = pytest.MonkeyPatch()
+    monkeypatch.setattr(sys, "argv", [sys.executable, "pytest"])
+    assert main_mod._scm_started_us() is False
+
+
+def test_main_dispatches_to_service_host(monkeypatch: pytest.MonkeyPatch) -> None:
+    """When the SCM started us, main hands over without parsing the CLI."""
+    _scm_environment(monkeypatch)
+    monkeypatch.setattr(main_mod.sys, "argv", [r"C:\diag\opcda-diagnozer.exe", "service"])
+    dispatched: list[list[str]] = []
+
+    def _fake_host(argv):
+        dispatched.append(list(argv))
+        return 0
+
+    monkeypatch.setattr(
+        "opcda_diagnozer.service.handle_service_command_line", _fake_host
+    )
+    assert main_mod.main() == 0
+    assert dispatched == [[r"C:\diag\opcda-diagnozer.exe", "service"]]
+
+
+def test_main_with_explicit_argv_is_always_cli(
+    monkeypatch: pytest.MonkeyPatch, tmp_path: Path
+) -> None:
+    """main(argv=[...]) (tests, console_script plumbing) never SCM-dispatches."""
+    _scm_environment(monkeypatch)
+    good = tmp_path / "config.yaml"
+    good.write_text(
+        "opc: {server: Fake.Server.1}\ntags: [{name: T.Counter}]\n",
+        encoding="utf-8",
+    )
+    called = []
+    monkeypatch.setattr(
+        "opcda_diagnozer.service.handle_service_command_line",
+        lambda argv: called.append(argv) or 1,
+    )
+    # an explicit argv bypasses the SCM check entirely
+    assert main_mod.main(["check-config", "--config", str(good)]) == 0
+    assert called == []  # never dispatched
+
+
+# --------------------------------------------------------------------------- #
+# failure actions (SCM recovery, plan §6.3)
+# --------------------------------------------------------------------------- #
+
+@pytest.mark.skipif(sys.platform != "win32", reason="pywin32 SC_ACTION constants")
+class TestFailureActions:
+    def test_shape_matches_pywin32_parser(self) -> None:
+        """The dict must carry every key the SWIG parser requires.
+
+        Verified live: the parser rejects partial dicts with
+        "must be a dictionary containing {'ResetPeriod':int,'RebootMsg':
+        unicode,'Command':unicode,'Actions':sequence of 2 tuples(int,int)".
+        """
+        import win32service
+
+        fa = svc.failure_actions()
+        assert set(fa) == {"ResetPeriod", "RebootMsg", "Command", "Actions"}
+        assert isinstance(fa["ResetPeriod"], int)
+        assert isinstance(fa["RebootMsg"], str)
+        assert isinstance(fa["Command"], str)
+        actions = fa["Actions"]
+        for action in actions:
+            assert isinstance(action, tuple)
+            assert len(action) == 2
+            assert all(isinstance(v, int) for v in action)
+        # first AND second failure restart the service (spec §10.1)
+        assert [a[0] for a in actions] == [
+            win32service.SC_ACTION_RESTART,
+            win32service.SC_ACTION_RESTART,
+        ]
+
+    def test_restart_delay_is_configurable(self) -> None:
+        fa = svc.failure_actions(restart_delay_ms=30_000)
+        assert all(delay == 30_000 for _, delay in fa["Actions"])
+
+    def test_parses_through_change_service_config2(self, tmp_path: Path) -> None:
+        """End-to-end: the exact dict install passes must survive the parser.
+
+        Parse success is proven by the handle error (invalid handle — a
+        parse failure would raise TypeError naming the expected dict).
+        """
+        import pywintypes
+        import win32service
+
+        try:
+            win32service.ChangeServiceConfig2(
+                None,
+                win32service.SERVICE_CONFIG_FAILURE_ACTIONS,
+                svc.failure_actions(),
+            )
+        except TypeError as exc:
+            pytest.fail(f"failure-actions dict does not parse: {exc}")
+        except pywintypes.error as exc:
+            assert exc.winerror == 6  # ERROR_INVALID_HANDLE: parse OK
+
+
+# --------------------------------------------------------------------------- #
+# service class identity + install payload
+# --------------------------------------------------------------------------- #
+
+@pytest.mark.skipif(sys.platform != "win32", reason="ServiceFramework is Windows-only")
+class TestServiceClass:
+    def test_identity(self) -> None:
+        cls = svc.get_service_class()
+        assert cls is not None
+        assert cls._svc_name_ == svc.SERVICE_NAME == "OPCDA-Diagnozer"
+        assert cls._svc_display_name_ == "OPC DA Diagnozer"
+        assert "read-only" in cls._svc_description_.lower()
+
+    def test_class_string_is_importable_shape(self) -> None:
+        """The registry class string must be module.Class of THIS module."""
+        assert svc._SERVICE_CLASS_STRING == (
+            "opcda_diagnozer.service.OpcdaDiagnozerService"
+        )
+
+    def test_stop_timeout_exceeds_poll_slice(self) -> None:
+        """The SCM stop wait must be generous vs. the poller's stop latency."""
+        from opcda_diagnozer.monitor.poller import _WATCH_SLICE_S
+
+        assert svc._STOP_TIMEOUT_S > _WATCH_SLICE_S * 10
+
+
+# --------------------------------------------------------------------------- #
+# CLI service verbs (injected SCM functions)
+# --------------------------------------------------------------------------- #
+
+class _ScmError(Exception):
+    """win32service.error stand-in with the attributes the CLI reads."""
+
+    def __init__(self, winerror: int, strerror: str) -> None:
+        super().__init__(strerror)
+        self.winerror = winerror
+        self.strerror = strerror
+
+
+class TestServiceVerbs:
+    def test_status_prints_state(self, capsys) -> None:
+        monkeypatch = pytest.MonkeyPatch()
+        monkeypatch.setattr(svc, "service_status", lambda: "STOPPED")
+        try:
+            code = main_mod._cmd_service_verb("status")
+        finally:
+            monkeypatch.undo()
+        out = capsys.readouterr().out
+        assert code == 0
+        assert "OPCDA-Diagnozer" in out and "STOPPED" in out
+
+    def test_install_validates_config_first(self, tmp_path: Path, capsys) -> None:
+        """A broken config must abort install BEFORE touching the SCM."""
+        bad = tmp_path / "bad.yaml"
+        bad.write_text("opc: {server: S}\ntags: []\ndevices: []\n", encoding="utf-8")
+        installed = []
+
+        def _fail(*args, **kwargs):  # pragma: no cover — must not be reached
+            installed.append(args)
+
+        monkeypatch = pytest.MonkeyPatch()
+        monkeypatch.setattr(svc, "install_service", _fail)
+        try:
+            code = main_mod._cmd_service_verb("install", config_path=str(bad))
+        finally:
+            monkeypatch.undo()
+        assert code == 2
+        assert installed == []  # SCM never touched
+        assert "invalid" in capsys.readouterr().err
+
+    def test_install_happy_path(self, tmp_path: Path, capsys) -> None:
+        good = tmp_path / "config.yaml"
+        good.write_text(
+            "opc: {server: Fake.Server.1}\ntags: [{name: T.Counter}]\n",
+            encoding="utf-8",
+        )
+        calls = {}
+
+        def _install(config_path, account=None, password=None):
+            calls["config"] = config_path
+            calls["account"] = account
+
+        monkeypatch = pytest.MonkeyPatch()
+        monkeypatch.setattr(svc, "install_service", _install)
+        try:
+            code = main_mod._cmd_service_verb("install", config_path=str(good))
+        finally:
+            monkeypatch.undo()
+        out = capsys.readouterr().out
+        assert code == 0
+        assert calls["config"] == str(good)
+        assert "auto-start" in out
+
+    def test_access_denied_gets_the_elevation_hint(self, capsys) -> None:
+        exc = _ScmError(5, "Access is denied.")
+        out = main_mod._service_verb_error("install", exc)
+        err = capsys.readouterr().err
+        assert out == 2
+        assert "elevated" in err
+        assert "Access is denied." in err
+
+    def test_not_installed_gets_the_install_hint(self, capsys) -> None:
+        exc = _ScmError(1060, "The specified service does not exist as an installed service.")
+        out = main_mod._service_verb_error("start", exc)
+        err = capsys.readouterr().err
+        assert out == 2
+        assert "not installed" in err
+
+    def test_not_active_stop_hint(self, capsys) -> None:
+        exc = _ScmError(1062, "The service has not been started.")
+        out = main_mod._service_verb_error("stop", exc)
+        err = capsys.readouterr().err
+        assert out == 2
+        assert "not running" in err
+
+    def test_unknown_winerror_still_names_the_code(self, capsys) -> None:
+        exc = _ScmError(1053, "The service did not respond to the start request.")
+        out = main_mod._service_verb_error("start", exc)
+        err = capsys.readouterr().err
+        assert out == 2
+        assert "1053" in err
+        assert "net helpmsg" in err
+
+    def test_plain_exception_without_winerror(self, capsys) -> None:
+        out = main_mod._service_verb_error("uninstall", ConfigError("registry offline"))
+        err = capsys.readouterr().err
+        assert out == 2
+        assert "registry offline" in err
+
+    def test_verb_dispatch_via_main(self, monkeypatch: pytest.MonkeyPatch, capsys) -> None:
+        """The verbs must be reachable through the real parser."""
+        monkeypatch.setattr(svc, "service_status", lambda: "RUNNING")
+        monkeypatch.setattr(svc, "install_service", lambda *a, **k: None)
+        monkeypatch.setattr(svc, "uninstall_service", lambda: None)
+        monkeypatch.setattr(svc, "start_service", lambda: None)
+        monkeypatch.setattr(svc, "stop_service", lambda: None)
+        assert main_mod.main(["status"]) == 0
+        assert "RUNNING" in capsys.readouterr().out
+
+
+# --------------------------------------------------------------------------- #
+# non-Windows guard
+# --------------------------------------------------------------------------- #
+
+def test_service_module_imports_everywhere() -> None:
+    """The module is importable without pywin32 (guarded imports, plan §9)."""
+    assert svc.SERVICE_NAME == "OPCDA-Diagnozer"
+    assert callable(svc.handle_service_command_line)
+
+
+@pytest.mark.skipif(sys.platform == "win32", reason="guard test for other platforms")
+def test_get_service_class_none_off_windows() -> None:
+    assert svc.get_service_class() is None