Merge pull request 'fix(release): tag only, and stop pushing to main' (#28) from fix/release-tag-only into main

Reviewed-on: #28
Reviewed-by: Colby Whitlock <whitlocktech@gmail.com>

.gitea/workflows/release.yml

@@ -279,33 +279,43 @@ jobs:
           ls -l dist && echo "----" && cat dist/SHA256SUMS
 
       # ── RELEASE ENGINE: commit the bump, tag, push ───────────────────────
-      - name: Commit version bump and push tag
+      # Tag only — `main` is never pushed to.
+      #
+      # This step used to commit the version bump back to main first. Two things
+      # were wrong with that. It has never once executed: an EMPTY template
+      # expression written literally in a comment (the `$`+`{{ }}` token, which
+      # is why it is spelled out here) made the runner fail to build the script
+      # and skip the whole step silently, which is why sidecar/Cargo.toml still
+      # says 0.1.0 after six releases (the tags exist because the release API
+      # creates one when it publishes). And had it executed, it would have been
+      # declined — main is protected, and a release must not depend on a write
+      # to a protected branch.
+      #
+      # So the tag is the version, as it already is in servuo-plugins. The
+      # workflow still writes the real version into Cargo.toml before building,
+      # so a released binary self-reports correctly; what it no longer does is
+      # commit that edit back. The next version is computed from the newest tag,
+      # never from Cargo.toml, so nothing downstream depends on the file.
+      - name: Push the release tag
         if: ${{ steps.plan.outputs.release == 'true' }}
         env:
           REGISTRY_USER: ${{ secrets.REGISTRY_USER }}
           REGISTRY_TOKEN: ${{ secrets.REGISTRY_TOKEN }}
         run: |
           set -euo pipefail
-          VERSION="${{ steps.plan.outputs.version }}"
           TAG="${{ steps.plan.outputs.tag }}"
           # Secrets can arrive with a trailing newline (depending on how they were
           # pasted); a stray CR/LF corrupts the remote URL ("credential url cannot
-          # be parsed"). Strip line breaks before building the URL. Passing them via
+          # be parsed"). Strip line breaks before building the URL. They are passed
-          # env (not inline ${{ }}) also keeps a newline from breaking this script.
+          # via env rather than interpolated into this script, so a newline cannot
+          # break it — do NOT write a template token literally in a comment here,
+          # or the runner will skip this step without failing the job.
           CI_USER="$(printf '%s' "${REGISTRY_USER}" | tr -d '\r\n')"
           CI_TOKEN="$(printf '%s' "${REGISTRY_TOKEN}" | tr -d '\r\n')"
           git config user.name  "uo-link-ci"
           git config user.email "ci@whitlocktech.com"
           git remote set-url origin \
             "https://${CI_USER}:${CI_TOKEN}@${GITEA_HOST}/${REPO}.git"
-
-          git add "${WORKDIR}/Cargo.toml" "${WORKDIR}/Cargo.lock"
-          if ! git diff --cached --quiet; then
-            git commit -m "chore(release): bump version to ${TAG} [skip ci]"
-            git push origin "HEAD:main"
-          else
-            echo "Version unchanged (first release) — no bump commit needed."
-          fi
           # The tag may already exist when finishing a run that died after tagging
           # (see the plan step). `git tag` on an existing name fails under
           # `set -e`; pushing an identical existing tag is a harmless no-op. A

README.md

@@ -48,6 +48,29 @@ to read the token back; it is not meant to be scraped from the log.
 uo-link-sidecar --print-config --config /etc/runicgateway/sidecar.toml
 ```
 
+### Running as a service
+
+The same binary runs in the foreground and as a system service — there is no `--service` flag to
+remember, because the process can tell how it was started.
+
+- **Linux/systemd** supervises any foreground process, so the unit just runs the binary. `SIGTERM`
+  (what `systemctl stop` sends) and `SIGINT` both unwind it cleanly; logs go to the journal.
+- **Windows** cannot. The service control manager only supervises a process that connects back to
+  it within ~30 seconds via `StartServiceCtrlDispatcher`; a plain console program registered with
+  `sc.exe create` is killed with **error 1053** despite running perfectly. So on Windows the sidecar
+  speaks that handshake: started by the SCM it runs as a service, started from a shell the connect
+  fails with `ERROR_FAILED_SERVICE_CONTROLLER_CONNECT` and it falls through to an ordinary
+  foreground run. It reports `Running` only once the shard port is bound and the store is open, and
+  — having no console — logs to `uo-link-sidecar.<date>.log` beside its config, rolled daily.
+
+Only the starting and stopping is platform-specific: `src/app.rs` is the entire sidecar and is
+shared, while `src/windows.rs` and `src/unix.rs` do nothing but start it and tell it when to stop.
+The Windows crates are declared under `[target.'cfg(windows)'.dependencies]`, so Cargo neither
+resolves nor builds them for a Linux target.
+
+Registering the service is the installer's job; to do it by hand see
+[INSTALL.md Appendix A4](https://gitea.whitlocktech.com/RunicGateway/docs/src/branch/main/installer/INSTALL.md).
+
 `.gitea/workflows/release.yml` cross-compiles Linux + Windows binaries and cuts a Gitea release on
 every merge to `main` (conventional-commit versioning). See [`sidecar/README.md`](sidecar/README.md)
 for configuration and the wire protocol.

sidecar/Cargo.lock

@@ -242,6 +242,15 @@ version = "2.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "217698eaf96b4a3f0bc4f3662aaa55bdf913cd54d7204591faa790070c6d0853"
 
+[[package]]
+name = "crossbeam-channel"
+version = "0.5.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d85363c37faeca707aef026efa9f3b34d077bce547e48f770770625c6013679e"
+dependencies = [
+ "crossbeam-utils",
+]
+
 [[package]]
 name = "crossbeam-queue"
 version = "0.3.13"
@@ -284,6 +293,12 @@ dependencies = [
  "zeroize",
 ]
 
+[[package]]
+name = "deranged"
+version = "0.5.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7cd812cc2bc1d69d4764bd80df88b4317eaef9e773c75226407d9bc0876b211c"
+
 [[package]]
 name = "digest"
 version = "0.10.7"
@@ -921,6 +936,12 @@ dependencies = [
  "zeroize",
 ]
 
+[[package]]
+name = "num-conv"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "521739c6d2bac4aa25192232afe6841231376b2b26d4d9fae5ecf8ca5772e441"
+
 [[package]]
 name = "num-integer"
 version = "0.1.46"
@@ -1048,6 +1069,12 @@ dependencies = [
  "zerovec",
 ]
 
+[[package]]
+name = "powerfmt"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "439ee305def115ba05938db6eb1644ff94165c5ab5e9420d1c1bcedbba909391"
+
 [[package]]
 name = "ppv-lite86"
 version = "0.2.21"
@@ -1565,6 +1592,12 @@ version = "2.6.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "13c2bddecc57b384dee18652358fb23172facb8a2c51ccc10d74c157bdea3292"
 
+[[package]]
+name = "symlink"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a7973cce6668464ea31f176d85b13c7ab3bba2cb3b77a2ed26abd7801688010a"
+
 [[package]]
 name = "syn"
 version = "2.0.118"
@@ -1642,6 +1675,36 @@ dependencies = [
  "cfg-if",
 ]
 
+[[package]]
+name = "time"
+version = "0.3.55"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cdb87b95ec50ddfa440816d227a17b2ccbdda963a316a727fda0fc4334f7d134"
+dependencies = [
+ "deranged",
+ "num-conv",
+ "powerfmt",
+ "serde_core",
+ "time-core",
+ "time-macros",
+]
+
+[[package]]
+name = "time-core"
+version = "0.1.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9e1c906769ad99c88eaa54e728060edef082f8e358ff32030cb7c7d315e81109"
+
+[[package]]
+name = "time-macros"
+version = "0.2.32"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7e689342a48d2ea927c87ea50cabf8594854bf940e9310208848d680d668ed85"
+dependencies = [
+ "num-conv",
+ "time-core",
+]
+
 [[package]]
 name = "tinystr"
 version = "0.8.3"
@@ -1798,6 +1861,19 @@ dependencies = [
  "tracing-core",
 ]
 
+[[package]]
+name = "tracing-appender"
+version = "0.2.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "050686193eb999b4bb3bc2acfa891a13da00f79734704c4b8b4ef1a10b368a3c"
+dependencies = [
+ "crossbeam-channel",
+ "symlink",
+ "thiserror 2.0.18",
+ "time",
+ "tracing-subscriber",
+]
+
 [[package]]
 name = "tracing-attributes"
 version = "0.1.31"
@@ -1913,7 +1989,9 @@ dependencies = [
  "tokio",
  "toml",
  "tracing",
+ "tracing-appender",
  "tracing-subscriber",
+ "windows-service",
 ]
 
 [[package]]
@@ -2025,6 +2103,12 @@ dependencies = [
  "wasite",
 ]
 
+[[package]]
+name = "widestring"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72069c3113ab32ab29e5584db3c6ec55d416895e60715417b5b883a357c3e471"
+
 [[package]]
 name = "windows-core"
 version = "0.62.2"
@@ -2075,6 +2159,17 @@ dependencies = [
  "windows-link",
 ]
 
+[[package]]
+name = "windows-service"
+version = "0.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "857224b3b211c6f3616921f081ee54721ee3ad2ace2fac6a6337e032f7b4dcf2"
+dependencies = [
+ "bitflags",
+ "widestring",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "windows-strings"
 version = "0.5.1"

sidecar/Cargo.toml

@@ -17,5 +17,12 @@ toml = "0.8"
 getrandom = "0.2"
 chrono = { version = "0.4", default-features = false, features = ["std", "clock"] }
 
+# Speaking the Windows Service Control Manager's startup handshake, and logging somewhere other
+# than the stdout a service does not have. Declared per target so Cargo neither resolves nor builds
+# either crate for Linux — the Linux binary is byte-for-byte unaffected by Windows service support.
+[target.'cfg(windows)'.dependencies]
+windows-service = "0.8"
+tracing-appender = "0.2"
+
 [profile.release]
 opt-level = 2

sidecar/src/app.rs

@@ -0,0 +1,329 @@
+//! The sidecar itself: everything that happens between "we have a config path" and "we were told
+//! to stop". Identical on every platform.
+//!
+//! This module exists so that *how the process is started and stopped* — a bare `main` under
+//! systemd, or a `ServiceMain` under the Windows SCM — is the only thing that differs between
+//! hosts. The shard listener, the config, the store, the web server and the event loop are shared
+//! code with no `#[cfg]` in sight.
+//!
+//! [`run`] is parameterised on the two things a supervisor cares about:
+//!
+//! - `ready` is called once the sidecar is actually up (listener bound, store open). The Windows
+//!   service reports `Running` to the SCM there, so a config or bind failure surfaces as a *start*
+//!   failure rather than a service that reports Running and then dies.
+//! - `shutdown` is whatever "stop" means on this host: Ctrl-C and `SIGTERM` on Unix, the SCM's
+//!   `Stop` control on Windows.
+
+use std::future::Future;
+use std::sync::atomic::AtomicI64;
+use std::sync::Arc;
+use std::time::Instant;
+
+use tokio::sync::{broadcast, mpsc};
+use tracing::info;
+
+use crate::{config, rpc, shard, store, web};
+
+/// Runs the sidecar until `shutdown` resolves.
+///
+/// `config_path` is the `--config` argument, or `None` to resolve `$UOLINK_CONFIG` and the default
+/// as usual.
+pub async fn run<R, S>(config_path: Option<&str>, ready: R, shutdown: S) -> anyhow::Result<()>
+where
+    R: FnOnce(),
+    S: Future<Output = ()>,
+{
+    info!("uo-link sidecar starting");
+
+    let loaded = config::Config::load(config_path)?;
+    let cfg = loaded.cfg;
+    info!(
+        config = %loaded.path.display(),
+        shard = %cfg.shard.bind,
+        web = %cfg.web.bind,
+        db = %cfg.store.path,
+        auth = cfg.auth_required(),
+        "configuration loaded"
+    );
+
+    // Shard link: events in, commands out.
+    let (event_tx, mut event_rx) = mpsc::unbounded_channel::<shard::ShardEvent>();
+    let handle = shard::serve(&cfg.shard.bind, event_tx).await?;
+
+    // Live feed: every shard event fans out to all connected website WebSocket clients.
+    let (bcast_tx, _) = broadcast::channel::<String>(1024);
+
+    // Request/reply correlation for REST queries.
+    let rpc = rpc::Rpc::new();
+
+    // Durable store: event history, economy series, cached profiles, link map.
+    let store = store::Store::open(&cfg.store.path).await?;
+
+    // Health/observability state.
+    let started = Instant::now();
+    let last_event = Arc::new(AtomicI64::new(0));
+
+    // Website-facing HTTP server.
+    let web_state = web::AppState {
+        events: bcast_tx.clone(),
+        shard: handle.clone(),
+        rpc: rpc.clone(),
+        store: store.clone(),
+        token: Arc::new(cfg.web.auth_token.clone()),
+        started,
+        last_event: last_event.clone(),
+    };
+    let web_bind = cfg.web.bind.clone();
+    tokio::spawn(async move {
+        if let Err(e) = web::serve(&web_bind, web_state).await {
+            tracing::error!(error = %e, "web server exited");
+        }
+    });
+
+    // Event loop: a line that correlates to a pending REST call is a reply — route it to the
+    // waiting caller and stop. Everything else is a live event: log it, persist it, broadcast it.
+    let feed_tx = bcast_tx.clone();
+    let route_rpc = rpc.clone();
+    let event_store = store.clone();
+    let last_event_ts = last_event.clone();
+    let replay_handle = handle.clone(); // re-push external news to the shard on (re)connect
+    let mut total: u64 = 0;
+    tokio::spawn(async move {
+        while let Some(ev) = event_rx.recv().await {
+            // Any line from the shard — including pong heartbeats — is a sign of life.
+            last_event_ts.store(now_ms(), std::sync::atomic::Ordering::Relaxed);
+
+            if route_rpc.try_route(&ev.value).await {
+                continue; // consumed as a reply
+            }
+
+            total += 1;
+            match ev.kind.as_str() {
+                "server.hello" | "mob.login" | "mob.logout" | "player.death" | "vendor.sale"
+                | "house.decay" | "link.request" => {
+                    info!(kind = %ev.kind, n = total, "{}", ev.value);
+                }
+                _ => tracing::debug!(kind = %ev.kind, n = total, "{}", ev.value),
+            }
+
+            // Persist, then broadcast. `pong` and `ws.hello` are ephemeral chatter, not history.
+            if ev.kind != "pong" {
+                let t = ev
+                    .value
+                    .get("t")
+                    .and_then(|v| v.as_i64())
+                    .unwrap_or_else(now_ms);
+                let text = ev.value.to_string();
+                if let Err(e) = event_store.insert_event(t, &ev.kind, &text).await {
+                    tracing::warn!(error = %e, "failed to persist event");
+                }
+
+                // The champ board is a live projection: champ.update folds in the latest state (one
+                // row per spawn), champ.remove drops a spawn that despawned or was slain.
+                match ev.kind.as_str() {
+                    "champ.update" => {
+                        if let Some(serial) = ev.value.get("serial").and_then(|s| s.as_str()) {
+                            if let Err(e) = event_store
+                                .upsert_champ(
+                                    serial,
+                                    ev.value.get("status").and_then(|s| s.as_str()),
+                                    ev.value.get("name").and_then(|n| n.as_str()),
+                                    &text,
+                                    t,
+                                )
+                                .await
+                            {
+                                tracing::warn!(error = %e, "failed to upsert champ board");
+                            }
+                        }
+                    }
+                    "champ.remove" => {
+                        if let Some(serial) = ev.value.get("serial").and_then(|s| s.as_str()) {
+                            if let Err(e) = event_store.delete_champ(serial).await {
+                                tracing::warn!(error = %e, "failed to remove champ board row");
+                            }
+                        }
+                    }
+                    // Guild board (Protocol 2.0): guild.update folds in the latest roster (one row
+                    // per guild id); guild.remove drops a disbanded guild.
+                    "guild.update" => {
+                        if let Some(id) = ev.value.get("id").and_then(|v| v.as_i64()) {
+                            if let Err(e) = event_store
+                                .upsert_guild(
+                                    id,
+                                    ev.value.get("name").and_then(|n| n.as_str()),
+                                    &text,
+                                    t,
+                                )
+                                .await
+                            {
+                                tracing::warn!(error = %e, "failed to upsert guild board");
+                            }
+                        }
+                    }
+                    "guild.remove" => {
+                        if let Some(id) = ev.value.get("id").and_then(|v| v.as_i64()) {
+                            if let Err(e) = event_store.delete_guild(id).await {
+                                tracing::warn!(error = %e, "failed to remove guild board row");
+                            }
+                        }
+                    }
+                    // Governor board (Protocol 2.0): city.update folds in each city's latest
+                    // governance state (one row per city).
+                    "city.update" => {
+                        if let Some(city) = ev.value.get("city").and_then(|c| c.as_str()) {
+                            if let Err(e) = event_store.upsert_governor(city, &text, t).await {
+                                tracing::warn!(error = %e, "failed to upsert governor board");
+                            }
+                        }
+                    }
+                    // House registry (Protocol 2.0): house.update folds in each house's latest state
+                    // (one row per serial); house.remove drops a demolished/traded house.
+                    "house.update" => {
+                        if let Some(serial) = ev.value.get("serial").and_then(|s| s.as_str()) {
+                            if let Err(e) = event_store
+                                .upsert_house(
+                                    serial,
+                                    ev.value.get("name").and_then(|n| n.as_str()),
+                                    &text,
+                                    t,
+                                )
+                                .await
+                            {
+                                tracing::warn!(error = %e, "failed to upsert house registry");
+                            }
+                        }
+                    }
+                    "house.remove" => {
+                        if let Some(serial) = ev.value.get("serial").and_then(|s| s.as_str()) {
+                            if let Err(e) = event_store.delete_house(serial).await {
+                                tracing::warn!(error = %e, "failed to remove house registry row");
+                            }
+                        }
+                    }
+                    // Points/loyalty boards (Protocol 3.0): one row per point system, keyed by
+                    // the shard's own PointsType name. The plugin only emits a system whose top N
+                    // actually moved, so this is a sparse stream of overwrites — and there is no
+                    // `points.remove` to handle, because the shard's set of systems is fixed at
+                    // startup and cannot shrink.
+                    "points.board" => {
+                        if let Some(system) = ev.value.get("system").and_then(|s| s.as_str()) {
+                            if let Err(e) = event_store
+                                .upsert_points_board(
+                                    system,
+                                    ev.value.get("nameString").and_then(|n| n.as_str()),
+                                    &text,
+                                    t,
+                                )
+                                .await
+                            {
+                                tracing::warn!(error = %e, "failed to upsert points board");
+                            }
+                        }
+                    }
+                    // Player-vendor market index (Protocol 3.0). Each frame is authoritative for
+                    // one vendor — the shard's round-robin sweep only emits a shop whose contents,
+                    // prices or location actually moved — so this is a whole-row overwrite.
+                    //
+                    // Unlike the boards above there IS a remove: a vendor is dismissed, expires, or
+                    // its owner switches off the in-game Vendor Search flag, and any of those must
+                    // take the shop off the site. The last of the three is a privacy control, so
+                    // dropping the row promptly is the point rather than housekeeping.
+                    "vendor.listing" => {
+                        if let Some(serial) = ev.value.get("serial").and_then(|s| s.as_str()) {
+                            let loc = ev.value.get("location");
+                            let field = |k: &str| loc.and_then(|l| l.get(k));
+                            if let Err(e) = event_store
+                                .upsert_vendor(
+                                    serial,
+                                    ev.value.get("shopName").and_then(|v| v.as_str()),
+                                    ev.value.get("ownerName").and_then(|v| v.as_str()),
+                                    field("map").and_then(|v| v.as_str()),
+                                    field("x").and_then(|v| v.as_i64()),
+                                    field("y").and_then(|v| v.as_i64()),
+                                    field("region").and_then(|v| v.as_str()),
+                                    ev.value.get("count").and_then(|v| v.as_i64()),
+                                    &text,
+                                    t,
+                                )
+                                .await
+                            {
+                                tracing::warn!(error = %e, "failed to upsert vendor listing");
+                            }
+                        }
+                    }
+                    "vendor.listing.remove" => {
+                        if let Some(serial) = ev.value.get("serial").and_then(|s| s.as_str()) {
+                            if let Err(e) = event_store.delete_vendor(serial).await {
+                                tracing::warn!(error = %e, "failed to remove vendor listing");
+                            }
+                        }
+                    }
+                    // Shard ruleset (Protocol 3.0): a singleton projection. The shard re-emits
+                    // world.ruleset on every connect, so this row is simply overwritten; `rev`
+                    // lets a reader tell a re-send from an actual config change.
+                    "world.ruleset" => {
+                        if let Err(e) = event_store
+                            .upsert_ruleset(ev.value.get("rev").and_then(|r| r.as_str()), &text, t)
+                            .await
+                        {
+                            tracing::warn!(error = %e, "failed to upsert ruleset");
+                        }
+                    }
+                    _ => {}
+                }
+            }
+
+            // On a shard (re)connect, re-push the stored external news: the shard rebuilds
+            // TownCryerSystem.NewsEntries from scratch each boot and does not persist ours. Replay
+            // with announce=false so a restart does not re-proclaim every article at once. news.add
+            // is idempotent by id, so replaying to a still-populated shard is harmless.
+            if ev.kind == "server.hello" {
+                match event_store.news_all().await {
+                    Ok(items) => {
+                        for mut item in items {
+                            if let Some(obj) = item.as_object_mut() {
+                                obj.insert("announce".to_string(), serde_json::json!(false));
+                            }
+                            if !replay_handle.send(item.to_string()).await {
+                                break; // shard went away mid-replay
+                            }
+                        }
+                    }
+                    Err(e) => tracing::warn!(error = %e, "news replay: could not read stored news"),
+                }
+            }
+
+            let _ = feed_tx.send(ev.value.to_string());
+        }
+    });
+
+    // Heartbeat to the shard, exercising the command path.
+    let ping_handle = handle.clone();
+    tokio::spawn(async move {
+        loop {
+            tokio::time::sleep(std::time::Duration::from_secs(15)).await;
+            if ping_handle.is_connected().await {
+                let _ = ping_handle
+                    .send(r#"{"kind":"ping","id":"sidecar-heartbeat"}"#.to_string())
+                    .await;
+            }
+        }
+    });
+
+    // Everything that can fail at startup has now either failed or succeeded: the shard port is
+    // bound and the store is open. A supervisor may call this "started".
+    ready();
+
+    shutdown.await;
+    info!("shutting down");
+    Ok(())
+}
+
+pub fn now_ms() -> i64 {
+    use std::time::{SystemTime, UNIX_EPOCH};
+    SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .map(|d| d.as_millis() as i64)
+        .unwrap_or(0)
+}

sidecar/src/main.rs

@@ -1,21 +1,37 @@
 //! uo-link sidecar.
 //!
-//! Terminates the loopback link to the ServUO shard and exposes a website-facing HTTP surface. So
+//! Terminates the loopback link to the ServUO shard and exposes a website-facing HTTP surface: the
-//! far: the shard link (bidirectional) and a WebSocket live feed. REST queries and SQLite come next.
+//! shard link (bidirectional), a WebSocket live feed, and REST queries backed by SQLite.
+//!
+//! # Layout
+//!
+//! `main` does argument handling and nothing else; the sidecar proper lives in [`app`] and is the
+//! same code on every platform. Only *how the process is started and stopped* is
+//! platform-specific:
+//!
+//! ```text
+//!   systemd ──▶ main ──▶ unix::run ─────────────────────────┐
+//!                                                           ├──▶ app::run
+//!   SCM ─────▶ main ──▶ windows::run ──▶ ServiceMain ───────┘
+//!                                    └─▶ console fallback ──┘
+//! ```
+//!
+//! The Windows half is not optional politeness: the SCM refuses to supervise a program that does
+//! not speak its startup handshake (see [`windows`]). The platform modules are gated with `#[cfg]`
+//! and their dependencies are declared per target, so none of it reaches a Linux build.
 
+mod app;
 mod cli;
 mod config;
 mod rpc;
 mod shard;
 mod store;
+#[cfg(unix)]
+mod unix;
 mod web;
+#[cfg(windows)]
+mod windows;
 
-use std::sync::atomic::AtomicI64;
-use std::sync::Arc;
-use std::time::Instant;
-
-use tokio::sync::{broadcast, mpsc};
-use tracing::info;
 use tracing_subscriber::EnvFilter;
 
 /// Wire-protocol version between the website and the sidecar. Bump this whenever an event or
@@ -32,8 +48,10 @@ use tracing_subscriber::EnvFilter;
 /// there is deliberately no feature-negotiation array: v3 implies all three kinds.
 pub const PROTOCOL_VERSION: u32 = 3;
 
-#[tokio::main]
+// Not `#[tokio::main]`: on Windows the SCM dispatcher takes over this thread and starts the runtime
-async fn main() -> anyhow::Result<()> {
+// itself, on its own thread, once the service actually begins. The runtime is built by whichever
+// platform module ends up running.
+fn main() -> anyhow::Result<()> {
     let args = match cli::parse(std::env::args().skip(1)) {
         Ok(args) => args,
         Err(msg) => {
@@ -66,299 +84,15 @@ async fn main() -> anyhow::Result<()> {
         cli::Mode::Run => {}
     }
 
-    init_tracing();
+    #[cfg(windows)]
-    info!("uo-link sidecar starting");
+    return windows::run(args.config.as_deref());
 
-    let loaded = config::Config::load(args.config.as_deref())?;
+    #[cfg(unix)]
-    let cfg = loaded.cfg;
+    return unix::run(args.config.as_deref());
-    info!(
-        config = %loaded.path.display(),
-        shard = %cfg.shard.bind,
-        web = %cfg.web.bind,
-        db = %cfg.store.path,
-        auth = cfg.auth_required(),
-        "configuration loaded"
-    );
-
-    // Shard link: events in, commands out.
-    let (event_tx, mut event_rx) = mpsc::unbounded_channel::<shard::ShardEvent>();
-    let handle = shard::serve(&cfg.shard.bind, event_tx).await?;
-
-    // Live feed: every shard event fans out to all connected website WebSocket clients.
-    let (bcast_tx, _) = broadcast::channel::<String>(1024);
-
-    // Request/reply correlation for REST queries.
-    let rpc = rpc::Rpc::new();
-
-    // Durable store: event history, economy series, cached profiles, link map.
-    let store = store::Store::open(&cfg.store.path).await?;
-
-    // Health/observability state.
-    let started = Instant::now();
-    let last_event = Arc::new(AtomicI64::new(0));
-
-    // Website-facing HTTP server.
-    let web_state = web::AppState {
-        events: bcast_tx.clone(),
-        shard: handle.clone(),
-        rpc: rpc.clone(),
-        store: store.clone(),
-        token: Arc::new(cfg.web.auth_token.clone()),
-        started,
-        last_event: last_event.clone(),
-    };
-    let web_bind = cfg.web.bind.clone();
-    tokio::spawn(async move {
-        if let Err(e) = web::serve(&web_bind, web_state).await {
-            tracing::error!(error = %e, "web server exited");
-        }
-    });
-
-    // Event loop: a line that correlates to a pending REST call is a reply — route it to the
-    // waiting caller and stop. Everything else is a live event: log it, persist it, broadcast it.
-    let feed_tx = bcast_tx.clone();
-    let route_rpc = rpc.clone();
-    let event_store = store.clone();
-    let last_event_ts = last_event.clone();
-    let replay_handle = handle.clone(); // re-push external news to the shard on (re)connect
-    let mut total: u64 = 0;
-    tokio::spawn(async move {
-        while let Some(ev) = event_rx.recv().await {
-            // Any line from the shard — including pong heartbeats — is a sign of life.
-            last_event_ts.store(now_ms(), std::sync::atomic::Ordering::Relaxed);
-
-            if route_rpc.try_route(&ev.value).await {
-                continue; // consumed as a reply
-            }
-
-            total += 1;
-            match ev.kind.as_str() {
-                "server.hello" | "mob.login" | "mob.logout" | "player.death" | "vendor.sale"
-                | "house.decay" | "link.request" => {
-                    info!(kind = %ev.kind, n = total, "{}", ev.value);
-                }
-                _ => tracing::debug!(kind = %ev.kind, n = total, "{}", ev.value),
-            }
-
-            // Persist, then broadcast. `pong` and `ws.hello` are ephemeral chatter, not history.
-            if ev.kind != "pong" {
-                let t = ev
-                    .value
-                    .get("t")
-                    .and_then(|v| v.as_i64())
-                    .unwrap_or_else(now_ms);
-                let text = ev.value.to_string();
-                if let Err(e) = event_store.insert_event(t, &ev.kind, &text).await {
-                    tracing::warn!(error = %e, "failed to persist event");
-                }
-
-                // The champ board is a live projection: champ.update folds in the latest state (one
-                // row per spawn), champ.remove drops a spawn that despawned or was slain.
-                match ev.kind.as_str() {
-                    "champ.update" => {
-                        if let Some(serial) = ev.value.get("serial").and_then(|s| s.as_str()) {
-                            if let Err(e) = event_store
-                                .upsert_champ(
-                                    serial,
-                                    ev.value.get("status").and_then(|s| s.as_str()),
-                                    ev.value.get("name").and_then(|n| n.as_str()),
-                                    &text,
-                                    t,
-                                )
-                                .await
-                            {
-                                tracing::warn!(error = %e, "failed to upsert champ board");
-                            }
-                        }
-                    }
-                    "champ.remove" => {
-                        if let Some(serial) = ev.value.get("serial").and_then(|s| s.as_str()) {
-                            if let Err(e) = event_store.delete_champ(serial).await {
-                                tracing::warn!(error = %e, "failed to remove champ board row");
-                            }
-                        }
-                    }
-                    // Guild board (Protocol 2.0): guild.update folds in the latest roster (one row
-                    // per guild id); guild.remove drops a disbanded guild.
-                    "guild.update" => {
-                        if let Some(id) = ev.value.get("id").and_then(|v| v.as_i64()) {
-                            if let Err(e) = event_store
-                                .upsert_guild(
-                                    id,
-                                    ev.value.get("name").and_then(|n| n.as_str()),
-                                    &text,
-                                    t,
-                                )
-                                .await
-                            {
-                                tracing::warn!(error = %e, "failed to upsert guild board");
-                            }
-                        }
-                    }
-                    "guild.remove" => {
-                        if let Some(id) = ev.value.get("id").and_then(|v| v.as_i64()) {
-                            if let Err(e) = event_store.delete_guild(id).await {
-                                tracing::warn!(error = %e, "failed to remove guild board row");
-                            }
-                        }
-                    }
-                    // Governor board (Protocol 2.0): city.update folds in each city's latest
-                    // governance state (one row per city).
-                    "city.update" => {
-                        if let Some(city) = ev.value.get("city").and_then(|c| c.as_str()) {
-                            if let Err(e) = event_store.upsert_governor(city, &text, t).await {
-                                tracing::warn!(error = %e, "failed to upsert governor board");
-                            }
-                        }
-                    }
-                    // House registry (Protocol 2.0): house.update folds in each house's latest state
-                    // (one row per serial); house.remove drops a demolished/traded house.
-                    "house.update" => {
-                        if let Some(serial) = ev.value.get("serial").and_then(|s| s.as_str()) {
-                            if let Err(e) = event_store
-                                .upsert_house(
-                                    serial,
-                                    ev.value.get("name").and_then(|n| n.as_str()),
-                                    &text,
-                                    t,
-                                )
-                                .await
-                            {
-                                tracing::warn!(error = %e, "failed to upsert house registry");
-                            }
-                        }
-                    }
-                    "house.remove" => {
-                        if let Some(serial) = ev.value.get("serial").and_then(|s| s.as_str()) {
-                            if let Err(e) = event_store.delete_house(serial).await {
-                                tracing::warn!(error = %e, "failed to remove house registry row");
-                            }
-                        }
-                    }
-                    // Points/loyalty boards (Protocol 3.0): one row per point system, keyed by
-                    // the shard's own PointsType name. The plugin only emits a system whose top N
-                    // actually moved, so this is a sparse stream of overwrites — and there is no
-                    // `points.remove` to handle, because the shard's set of systems is fixed at
-                    // startup and cannot shrink.
-                    "points.board" => {
-                        if let Some(system) = ev.value.get("system").and_then(|s| s.as_str()) {
-                            if let Err(e) = event_store
-                                .upsert_points_board(
-                                    system,
-                                    ev.value.get("nameString").and_then(|n| n.as_str()),
-                                    &text,
-                                    t,
-                                )
-                                .await
-                            {
-                                tracing::warn!(error = %e, "failed to upsert points board");
-                            }
-                        }
-                    }
-                    // Player-vendor market index (Protocol 3.0). Each frame is authoritative for
-                    // one vendor — the shard's round-robin sweep only emits a shop whose contents,
-                    // prices or location actually moved — so this is a whole-row overwrite.
-                    //
-                    // Unlike the boards above there IS a remove: a vendor is dismissed, expires, or
-                    // its owner switches off the in-game Vendor Search flag, and any of those must
-                    // take the shop off the site. The last of the three is a privacy control, so
-                    // dropping the row promptly is the point rather than housekeeping.
-                    "vendor.listing" => {
-                        if let Some(serial) = ev.value.get("serial").and_then(|s| s.as_str()) {
-                            let loc = ev.value.get("location");
-                            let field = |k: &str| loc.and_then(|l| l.get(k));
-                            if let Err(e) = event_store
-                                .upsert_vendor(
-                                    serial,
-                                    ev.value.get("shopName").and_then(|v| v.as_str()),
-                                    ev.value.get("ownerName").and_then(|v| v.as_str()),
-                                    field("map").and_then(|v| v.as_str()),
-                                    field("x").and_then(|v| v.as_i64()),
-                                    field("y").and_then(|v| v.as_i64()),
-                                    field("region").and_then(|v| v.as_str()),
-                                    ev.value.get("count").and_then(|v| v.as_i64()),
-                                    &text,
-                                    t,
-                                )
-                                .await
-                            {
-                                tracing::warn!(error = %e, "failed to upsert vendor listing");
-                            }
-                        }
-                    }
-                    "vendor.listing.remove" => {
-                        if let Some(serial) = ev.value.get("serial").and_then(|s| s.as_str()) {
-                            if let Err(e) = event_store.delete_vendor(serial).await {
-                                tracing::warn!(error = %e, "failed to remove vendor listing");
-                            }
-                        }
-                    }
-                    // Shard ruleset (Protocol 3.0): a singleton projection. The shard re-emits
-                    // world.ruleset on every connect, so this row is simply overwritten; `rev`
-                    // lets a reader tell a re-send from an actual config change.
-                    "world.ruleset" => {
-                        if let Err(e) = event_store
-                            .upsert_ruleset(ev.value.get("rev").and_then(|r| r.as_str()), &text, t)
-                            .await
-                        {
-                            tracing::warn!(error = %e, "failed to upsert ruleset");
-                        }
-                    }
-                    _ => {}
-                }
-            }
-
-            // On a shard (re)connect, re-push the stored external news: the shard rebuilds
-            // TownCryerSystem.NewsEntries from scratch each boot and does not persist ours. Replay
-            // with announce=false so a restart does not re-proclaim every article at once. news.add
-            // is idempotent by id, so replaying to a still-populated shard is harmless.
-            if ev.kind == "server.hello" {
-                match event_store.news_all().await {
-                    Ok(items) => {
-                        for mut item in items {
-                            if let Some(obj) = item.as_object_mut() {
-                                obj.insert("announce".to_string(), serde_json::json!(false));
-                            }
-                            if !replay_handle.send(item.to_string()).await {
-                                break; // shard went away mid-replay
-                            }
-                        }
-                    }
-                    Err(e) => tracing::warn!(error = %e, "news replay: could not read stored news"),
-                }
-            }
-
-            let _ = feed_tx.send(ev.value.to_string());
-        }
-    });
-
-    // Heartbeat to the shard, exercising the command path.
-    let ping_handle = handle.clone();
-    tokio::spawn(async move {
-        loop {
-            tokio::time::sleep(std::time::Duration::from_secs(15)).await;
-            if ping_handle.is_connected().await {
-                let _ = ping_handle
-                    .send(r#"{"kind":"ping","id":"sidecar-heartbeat"}"#.to_string())
-                    .await;
-            }
-        }
-    });
-
-    tokio::signal::ctrl_c().await?;
-    info!("shutting down");
-    Ok(())
 }
 
-fn now_ms() -> i64 {
+/// Logging for a foreground run: human-readable, on stdout.
-    use std::time::{SystemTime, UNIX_EPOCH};
+pub fn init_console_tracing() {
-    SystemTime::now()
-        .duration_since(UNIX_EPOCH)
-        .map(|d| d.as_millis() as i64)
-        .unwrap_or(0)
-}
-
-fn init_tracing() {
     tracing_subscriber::fmt()
         .with_env_filter(
             EnvFilter::try_from_default_env().unwrap_or_else(|_| EnvFilter::new("info")),

sidecar/src/unix.rs

@@ -0,0 +1,41 @@
+//! Unix startup and shutdown.
+//!
+//! There is no supervisor protocol to speak: systemd starts the process, and stops it by sending
+//! `SIGTERM`. All this module does is translate the two signals that mean "stop" into the future
+//! [`crate::app::run`] waits on, so a `systemctl stop` unwinds the same way a Ctrl-C does instead
+//! of being killed by the default `SIGTERM` disposition mid-write.
+
+use tokio::signal::unix::{signal, SignalKind};
+
+pub fn run(config_path: Option<&str>) -> anyhow::Result<()> {
+    crate::init_console_tracing();
+
+    tokio::runtime::Runtime::new()?.block_on(crate::app::run(config_path, || {}, shutdown_signal()))
+}
+
+/// Resolves on the first `SIGINT` or `SIGTERM`.
+async fn shutdown_signal() {
+    // A failure to install a handler is not worth aborting a running sidecar for: fall back to
+    // pending, which leaves that signal's default disposition (terminate) in place.
+    let mut term = match signal(SignalKind::terminate()) {
+        Ok(s) => s,
+        Err(e) => {
+            tracing::warn!(error = %e, "could not listen for SIGTERM");
+            std::future::pending::<()>().await;
+            unreachable!()
+        }
+    };
+    let mut int = match signal(SignalKind::interrupt()) {
+        Ok(s) => s,
+        Err(e) => {
+            tracing::warn!(error = %e, "could not listen for SIGINT");
+            term.recv().await;
+            return;
+        }
+    };
+
+    tokio::select! {
+        _ = term.recv() => tracing::info!("SIGTERM received"),
+        _ = int.recv()  => tracing::info!("SIGINT received"),
+    }
+}

sidecar/src/windows.rs

@@ -0,0 +1,239 @@
+//! Windows startup and shutdown: the SCM handshake.
+//!
+//! Unlike systemd, the Windows Service Control Manager cannot supervise an arbitrary console
+//! program. A binary registered with `sc.exe create` has ~30 seconds to call
+//! `StartServiceCtrlDispatcher` and connect back to the SCM; one that never does is killed with
+//! **error 1053, "the service did not respond to the start request in a timely fashion"** — even
+//! though the process itself started perfectly and is sitting there serving traffic. That is the
+//! entire reason this module exists.
+//!
+//! ## One binary, two ways in
+//!
+//! The dispatcher is tried first and *failing is expected*: when the process was started from a
+//! shell rather than by the SCM, the connect fails with `ERROR_FAILED_SERVICE_CONTROLLER_CONNECT`
+//! (1063), and that — and only that — falls through to a normal foreground run. So
+//! `uo-link-sidecar.exe --config ...` stays an ordinary console app you can Ctrl-C, `cargo run`
+//! still works, and the same binary can be registered as a service with no `--service` flag for an
+//! operator to forget. Any other dispatcher error is a real failure and is reported.
+//!
+//! ## Logging goes to a file, because a service has no stdout
+//!
+//! Under the SCM there is no console attached, so the normal stdout subscriber writes into the
+//! void. In service mode the sidecar logs to a daily-rolled file next to its config instead
+//! (`uo-link-sidecar.YYYY-MM-DD.log`, seven kept). A service whose start fails leaves a reason
+//! behind rather than only an SCM error code.
+
+use std::ffi::OsString;
+use std::path::PathBuf;
+use std::sync::Arc;
+use std::sync::OnceLock;
+use std::time::Duration;
+
+use tokio::sync::Notify;
+use tracing_subscriber::EnvFilter;
+use windows_service::service::{
+    ServiceControl, ServiceControlAccept, ServiceExitCode, ServiceState, ServiceStatus, ServiceType,
+};
+use windows_service::service_control_handler::{self, ServiceControlHandlerResult};
+use windows_service::{define_windows_service, service_dispatcher};
+
+/// Must match the name the installer registers (`installer/src/service.rs::WINDOWS_SERVICE`). For
+/// an own-process service the SCM ignores it, but a mismatch would be a trap for whoever converts
+/// this to a shared-process service later.
+pub const SERVICE_NAME: &str = "RunicGatewayLink";
+
+const SERVICE_TYPE: ServiceType = ServiceType::OWN_PROCESS;
+
+/// `ERROR_FAILED_SERVICE_CONTROLLER_CONNECT` — "this process was not started by the SCM", which is
+/// the normal answer when a human runs the binary.
+const ERROR_FAILED_SERVICE_CONTROLLER_CONNECT: i32 = 1063;
+
+/// `service_main` is called through an `extern "system"` trampoline and so can capture nothing.
+/// The parsed `--config` is handed over here instead of being re-parsed, so the service and a
+/// console run resolve their configuration through exactly the same code path.
+static CONFIG_PATH: OnceLock<Option<String>> = OnceLock::new();
+
+pub fn run(config_path: Option<&str>) -> anyhow::Result<()> {
+    let _ = CONFIG_PATH.set(config_path.map(str::to_string));
+
+    match service_dispatcher::start(SERVICE_NAME, ffi_service_main) {
+        Ok(()) => Ok(()),
+        // Not started by the SCM: this is a foreground run, which is not an error.
+        Err(windows_service::Error::Winapi(e))
+            if e.raw_os_error() == Some(ERROR_FAILED_SERVICE_CONTROLLER_CONNECT) =>
+        {
+            console_run(config_path)
+        }
+        Err(e) => Err(anyhow::Error::new(e)
+            .context("could not connect to the Windows service control manager")),
+    }
+}
+
+/// A normal foreground run: stdout logging, Ctrl-C to stop.
+fn console_run(config_path: Option<&str>) -> anyhow::Result<()> {
+    crate::init_console_tracing();
+    tokio::runtime::Runtime::new()?.block_on(crate::app::run(config_path, || {}, async {
+        let _ = tokio::signal::ctrl_c().await;
+    }))
+}
+
+define_windows_service!(ffi_service_main, service_main);
+
+fn service_main(_arguments: Vec<OsString>) {
+    // Arguments are deliberately ignored: for an own-process service the `binPath=` arguments
+    // arrive on the process command line and have already been parsed in `main`. What lands here
+    // is whatever was typed after `sc start`, which nothing in this deployment uses.
+    if let Err(e) = serve() {
+        // Nowhere left to report to but the log: the status handle is gone or was never obtained.
+        tracing::error!(error = %e, "service exited with an error");
+    }
+}
+
+fn serve() -> anyhow::Result<()> {
+    let config_path = CONFIG_PATH.get().cloned().flatten();
+    // Held for the life of the service: dropping the guard stops the background log writer.
+    let _log_guard = init_service_tracing(config_path.as_deref());
+
+    // The SCM calls the control handler on its own thread, so the stop signal crosses a thread
+    // boundary into the async world. `notify_one` stores a permit if nothing is waiting yet, so a
+    // stop that arrives during startup is not lost.
+    let stop = Arc::new(Notify::new());
+    let handler_stop = stop.clone();
+    let status_handle =
+        service_control_handler::register(SERVICE_NAME, move |control| match control {
+            ServiceControl::Interrogate => ServiceControlHandlerResult::NoError,
+            ServiceControl::Stop | ServiceControl::Shutdown => {
+                handler_stop.notify_one();
+                ServiceControlHandlerResult::NoError
+            }
+            _ => ServiceControlHandlerResult::NotImplemented,
+        })?;
+
+    // Registering the handler is the handshake 1053 was about. Everything after this point gets to
+    // take as long as it credibly needs, as long as the state keeps being reported.
+    status_handle.set_service_status(ServiceStatus {
+        service_type: SERVICE_TYPE,
+        current_state: ServiceState::StartPending,
+        controls_accepted: ServiceControlAccept::empty(),
+        exit_code: ServiceExitCode::Win32(0),
+        checkpoint: 0,
+        wait_hint: Duration::from_secs(30),
+        process_id: None,
+    })?;
+
+    let ready_handle = status_handle;
+    let result = tokio::runtime::Runtime::new()?.block_on(crate::app::run(
+        config_path.as_deref(),
+        // Reported only once the shard port is bound and the store is open, so a bad config or a
+        // taken port fails the *start* instead of flapping Running → Stopped a moment later.
+        move || {
+            let _ = ready_handle.set_service_status(ServiceStatus {
+                service_type: SERVICE_TYPE,
+                current_state: ServiceState::Running,
+                controls_accepted: ServiceControlAccept::STOP | ServiceControlAccept::SHUTDOWN,
+                exit_code: ServiceExitCode::Win32(0),
+                checkpoint: 0,
+                wait_hint: Duration::default(),
+                process_id: None,
+            });
+        },
+        async move { stop.notified().await },
+    ));
+
+    // A failed run must leave a nonzero SERVICE_EXIT_CODE behind: `sc query` reporting STOPPED with
+    // exit code 0 is what made the original failure look like a clean stop.
+    let exit_code = match &result {
+        Ok(()) => ServiceExitCode::Win32(0),
+        Err(e) => {
+            tracing::error!(error = %e, "sidecar failed");
+            ServiceExitCode::ServiceSpecific(1)
+        }
+    };
+    status_handle.set_service_status(ServiceStatus {
+        service_type: SERVICE_TYPE,
+        current_state: ServiceState::Stopped,
+        controls_accepted: ServiceControlAccept::empty(),
+        exit_code,
+        checkpoint: 0,
+        wait_hint: Duration::default(),
+        process_id: None,
+    })?;
+
+    result
+}
+
+/// Where the service writes its log: beside the config it was pointed at, which is the directory
+/// the installer already provisions and grants the service account write access to.
+fn log_dir(config_path: Option<&str>) -> PathBuf {
+    if let Some(parent) = config_path
+        .map(PathBuf::from)
+        .as_deref()
+        .and_then(|p| p.parent())
+        .filter(|p| !p.as_os_str().is_empty())
+    {
+        return parent.to_path_buf();
+    }
+    match std::env::var_os("ProgramData") {
+        Some(program_data) => PathBuf::from(program_data).join("RunicGateway"),
+        None => std::env::temp_dir(),
+    }
+}
+
+/// Returns `None` if the log file could not be opened — a service that cannot write a log is still
+/// a service worth running, and the SCM start must not fail over it.
+fn init_service_tracing(
+    config_path: Option<&str>,
+) -> Option<tracing_appender::non_blocking::WorkerGuard> {
+    let appender = tracing_appender::rolling::Builder::new()
+        .rotation(tracing_appender::rolling::Rotation::DAILY)
+        .filename_prefix("uo-link-sidecar")
+        .filename_suffix("log")
+        .max_log_files(7)
+        .build(log_dir(config_path))
+        .ok()?;
+
+    let (writer, guard) = tracing_appender::non_blocking(appender);
+    tracing_subscriber::fmt()
+        .with_env_filter(
+            EnvFilter::try_from_default_env().unwrap_or_else(|_| EnvFilter::new("info")),
+        )
+        .with_ansi(false) // a log file is not a terminal
+        .with_writer(writer)
+        .init();
+    Some(guard)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn log_dir_follows_the_config_file() {
+        assert_eq!(
+            log_dir(Some(r"C:\ProgramData\RunicGateway\sidecar.toml")),
+            PathBuf::from(r"C:\ProgramData\RunicGateway")
+        );
+    }
+
+    #[test]
+    fn a_bare_filename_does_not_become_the_filesystem_root() {
+        // `--config sidecar.toml` has a parent of "", which as a path means the root of the current
+        // drive — somewhere a service account cannot write. Fall back instead.
+        let dir = log_dir(Some("sidecar.toml"));
+        assert_ne!(dir, PathBuf::from(""));
+        assert!(dir.is_absolute(), "{}", dir.display());
+    }
+
+    #[test]
+    fn no_config_falls_back_to_program_data() {
+        let dir = log_dir(None);
+        assert!(dir.is_absolute(), "{}", dir.display());
+    }
+
+    #[test]
+    fn service_name_matches_the_installer() {
+        // installer/src/service.rs::WINDOWS_SERVICE. Kept as a literal on both sides — the two
+        // repos are released independently and do not share a crate.
+        assert_eq!(SERVICE_NAME, "RunicGatewayLink");
+    }
+}