Merge branch 'worktree-agent-af8a44154c4e2dbba' into arch-review-remediation

docker-env2/site-x-node-a/appsettings.Site.json

@@ -78,5 +78,16 @@
   // Replication is opt-in and configured separately; absent = local-only.
   "LocalDb": {
     "Path": "/app/data/site-localdb.db"
+  },
+  // arch-review remediation WP1.2: the site hot-path audit writer's SQLite file has no
+  // default path (mirrors LocalDb:Path above) and StartupValidator now requires it for
+  // Site nodes — an unset value used to fall back to a bare "auditlog.db" resolved
+  // relative to CWD, i.e. the container's ephemeral overlayfs, so the pending audit
+  // backlog was silently discarded on every recreate. On the mounted /app/data volume,
+  // same as LocalDb:Path, so it survives container recreate.
+  "AuditLog": {
+    "SiteWriter": {
+      "DatabasePath": "/app/data/auditlog.db"
+    }
   }
 }

docker-env2/site-x-node-b/appsettings.Site.json

@@ -78,5 +78,16 @@
   // Replication is opt-in and configured separately; absent = local-only.
   "LocalDb": {
     "Path": "/app/data/site-localdb.db"
+  },
+  // arch-review remediation WP1.2: the site hot-path audit writer's SQLite file has no
+  // default path (mirrors LocalDb:Path above) and StartupValidator now requires it for
+  // Site nodes — an unset value used to fall back to a bare "auditlog.db" resolved
+  // relative to CWD, i.e. the container's ephemeral overlayfs, so the pending audit
+  // backlog was silently discarded on every recreate. On the mounted /app/data volume,
+  // same as LocalDb:Path, so it survives container recreate.
+  "AuditLog": {
+    "SiteWriter": {
+      "DatabasePath": "/app/data/auditlog.db"
+    }
   }
 }

docker/site-a-node-a/appsettings.Site.json

@@ -120,5 +120,16 @@
       "MaxOplogRows": 250000,
       "MaxOplogAge": "2.00:00:00"
     }
+  },
+  // arch-review remediation WP1.2: the site hot-path audit writer's SQLite file has no
+  // default path (mirrors LocalDb:Path above) and StartupValidator now requires it for
+  // Site nodes — an unset value used to fall back to a bare "auditlog.db" resolved
+  // relative to CWD, i.e. the container's ephemeral overlayfs, so the pending audit
+  // backlog was silently discarded on every recreate. On the mounted /app/data volume,
+  // same as LocalDb:Path, so it survives container recreate.
+  "AuditLog": {
+    "SiteWriter": {
+      "DatabasePath": "/app/data/auditlog.db"
+    }
   }
 }

docker/site-a-node-b/appsettings.Site.json

@@ -113,5 +113,16 @@
       "MaxOplogRows": 250000,
       "MaxOplogAge": "2.00:00:00"
     }
+  },
+  // arch-review remediation WP1.2: the site hot-path audit writer's SQLite file has no
+  // default path (mirrors LocalDb:Path above) and StartupValidator now requires it for
+  // Site nodes — an unset value used to fall back to a bare "auditlog.db" resolved
+  // relative to CWD, i.e. the container's ephemeral overlayfs, so the pending audit
+  // backlog was silently discarded on every recreate. On the mounted /app/data volume,
+  // same as LocalDb:Path, so it survives container recreate.
+  "AuditLog": {
+    "SiteWriter": {
+      "DatabasePath": "/app/data/auditlog.db"
+    }
   }
 }

docker/site-b-node-a/appsettings.Site.json

@@ -86,5 +86,16 @@
   // Replication is opt-in and configured separately; absent = local-only.
   "LocalDb": {
     "Path": "/app/data/site-localdb.db"
+  },
+  // arch-review remediation WP1.2: the site hot-path audit writer's SQLite file has no
+  // default path (mirrors LocalDb:Path above) and StartupValidator now requires it for
+  // Site nodes — an unset value used to fall back to a bare "auditlog.db" resolved
+  // relative to CWD, i.e. the container's ephemeral overlayfs, so the pending audit
+  // backlog was silently discarded on every recreate. On the mounted /app/data volume,
+  // same as LocalDb:Path, so it survives container recreate.
+  "AuditLog": {
+    "SiteWriter": {
+      "DatabasePath": "/app/data/auditlog.db"
+    }
   }
 }

docker/site-b-node-b/appsettings.Site.json

@@ -86,5 +86,16 @@
   // Replication is opt-in and configured separately; absent = local-only.
   "LocalDb": {
     "Path": "/app/data/site-localdb.db"
+  },
+  // arch-review remediation WP1.2: the site hot-path audit writer's SQLite file has no
+  // default path (mirrors LocalDb:Path above) and StartupValidator now requires it for
+  // Site nodes — an unset value used to fall back to a bare "auditlog.db" resolved
+  // relative to CWD, i.e. the container's ephemeral overlayfs, so the pending audit
+  // backlog was silently discarded on every recreate. On the mounted /app/data volume,
+  // same as LocalDb:Path, so it survives container recreate.
+  "AuditLog": {
+    "SiteWriter": {
+      "DatabasePath": "/app/data/auditlog.db"
+    }
   }
 }

docker/site-c-node-a/appsettings.Site.json

@@ -86,5 +86,16 @@
   // Replication is opt-in and configured separately; absent = local-only.
   "LocalDb": {
     "Path": "/app/data/site-localdb.db"
+  },
+  // arch-review remediation WP1.2: the site hot-path audit writer's SQLite file has no
+  // default path (mirrors LocalDb:Path above) and StartupValidator now requires it for
+  // Site nodes — an unset value used to fall back to a bare "auditlog.db" resolved
+  // relative to CWD, i.e. the container's ephemeral overlayfs, so the pending audit
+  // backlog was silently discarded on every recreate. On the mounted /app/data volume,
+  // same as LocalDb:Path, so it survives container recreate.
+  "AuditLog": {
+    "SiteWriter": {
+      "DatabasePath": "/app/data/auditlog.db"
+    }
   }
 }

docker/site-c-node-b/appsettings.Site.json

@@ -86,5 +86,16 @@
   // Replication is opt-in and configured separately; absent = local-only.
   "LocalDb": {
     "Path": "/app/data/site-localdb.db"
+  },
+  // arch-review remediation WP1.2: the site hot-path audit writer's SQLite file has no
+  // default path (mirrors LocalDb:Path above) and StartupValidator now requires it for
+  // Site nodes — an unset value used to fall back to a bare "auditlog.db" resolved
+  // relative to CWD, i.e. the container's ephemeral overlayfs, so the pending audit
+  // backlog was silently discarded on every recreate. On the mounted /app/data volume,
+  // same as LocalDb:Path, so it survives container recreate.
+  "AuditLog": {
+    "SiteWriter": {
+      "DatabasePath": "/app/data/auditlog.db"
+    }
   }
 }

src/ZB.MOM.WW.ScadaBridge.AuditLog/Site/SqliteAuditWriter.cs

@@ -174,6 +174,24 @@ public class SqliteAuditWriter : IAuditWriter, ISiteAuditQueue, IAsyncDisposable
             pragmaCmd.ExecuteNonQuery();
         }
 
+        // synchronous=NORMAL (arch-review remediation WP1.2): SQLite's FULL default
+        // fsyncs on every transaction commit, which is the dominant cost of the
+        // per-event write path this same change coalesces via FlushIntervalMs — FULL
+        // would still fsync once per FLUSH even after that fix. NORMAL fsyncs at
+        // fewer, WAL-checkpoint-aligned points instead of every commit; the window
+        // this opens is a handful of the most recent commits lost on OS crash / power
+        // loss (WAL mode itself still guarantees no *corruption*, only a possible
+        // short rollback on unclean restart). That trade is acceptable here because
+        // audit writes are explicitly best-effort by design (CLAUDE.md: "Audit-write
+        // failure NEVER aborts the user-facing action — audit is best-effort, the
+        // action's own success/failure path is authoritative") — this is the same
+        // durability class as a dropped audit row, not a new risk class.
+        using (var pragmaCmd = _connection.CreateCommand())
+        {
+            pragmaCmd.CommandText = "PRAGMA synchronous = NORMAL";
+            pragmaCmd.ExecuteNonQuery();
+        }
+
         // Enable FK enforcement on the WRITE connection. PRAGMA foreign_keys is
         // a per-connection, per-session setting in SQLite — it is NOT persisted
         // in the database file, so every new connection that may INSERT into
@@ -306,20 +324,67 @@ public class SqliteAuditWriter : IAuditWriter, ISiteAuditQueue, IAsyncDisposable
         {
             batch.Clear();
             batch.Add(first);
+            var deadline = DateTime.UtcNow.AddMilliseconds(_options.FlushIntervalMs);
 
             // Pull additional ready events up to BatchSize. TryRead is non-
             // blocking and lets us amortise the transaction overhead across a
-            // burst of concurrent enqueues.
-            while (batch.Count < _options.BatchSize &&
-                   _writeQueue.Reader.TryRead(out var next))
+            // burst of concurrent enqueues. Once the immediately-available
+            // burst is drained, keep the transaction open for up to
+            // FlushIntervalMs waiting for MORE events to trickle in — this is
+            // the soft-flush coalescing arch-review remediation WP1.2 adds:
+            // without it, a low-rate trickle of writes (one script call every
+            // few ms, well under BatchSize) fsyncs once PER EVENT, because the
+            // writer loop reaches an empty channel and flushes immediately.
+            // FlushIntervalMs bounds the worst-case added latency any single
+            // event can see from this coalescing.
+            while (batch.Count < _options.BatchSize)
+            {
+                if (_writeQueue.Reader.TryRead(out var next))
                 {
                     batch.Add(next);
+                    continue;
+                }
+
+                var remaining = deadline - DateTime.UtcNow;
+                if (remaining <= TimeSpan.Zero)
+                {
+                    break;
+                }
+
+                var waitToRead = _writeQueue.Reader.WaitToReadAsync().AsTask();
+                var completed = await Task.WhenAny(
+                    waitToRead, Task.Delay(remaining)).ConfigureAwait(false);
+
+                if (completed != waitToRead)
+                {
+                    // Deadline elapsed with nothing new — flush what we have.
+                    break;
+                }
+
+                // WaitToReadAsync resolving false means the channel completed
+                // (Dispose) with nothing left to read; resolving true means at
+                // least one item is available, so the top of the loop's
+                // TryRead will pick it up.
+                if (!await waitToRead.ConfigureAwait(false))
+                {
+                    break;
+                }
             }
 
             FlushBatch(batch);
         }
     }
 
+    /// <summary>
+    /// Total number of <see cref="FlushBatch"/> transactions committed since
+    /// construction. Test-only observability seam (arch-review remediation
+    /// WP1.2) for asserting that FlushIntervalMs coalesces a trickle of
+    /// near-simultaneous writes into a single transaction rather than one
+    /// commit per event; production code never reads this.
+    /// </summary>
+    internal int FlushCountForTests => _flushCountForTests;
+    private int _flushCountForTests;
+
     private void FlushBatch(IReadOnlyList<PendingAuditEvent> batch)
     {
         lock (_writeLock)
@@ -436,6 +501,7 @@ public class SqliteAuditWriter : IAuditWriter, ISiteAuditQueue, IAsyncDisposable
                 }
 
                 transaction.Commit();
+                _flushCountForTests++;
             }
             catch (Exception ex)
             {

src/ZB.MOM.WW.ScadaBridge.AuditLog/Site/SqliteAuditWriterOptions.cs

@@ -9,8 +9,23 @@ namespace ZB.MOM.WW.ScadaBridge.AuditLog.Site;
 /// </summary>
 public sealed class SqliteAuditWriterOptions
 {
-    /// <summary>SQLite database path (or in-memory URI for tests).</summary>
-    public string DatabasePath { get; set; } = "auditlog.db";
+    /// <summary>
+    /// SQLite database path (or in-memory URI for tests). No default —
+    /// mirrors <c>LocalDb:Path</c> (<c>ZB.MOM.WW.LocalDb.LocalDbOptions.Path</c>): a
+    /// bare filename here would resolve relative to the process CWD, which on the
+    /// docker rig is the container's ephemeral overlayfs, not the mounted
+    /// <c>/app/data</c> volume — the file (and its pending forward-state backlog)
+    /// would be silently discarded on every container recreate. Site nodes MUST set
+    /// this explicitly (e.g. <c>/app/data/auditlog.db</c>); <c>StartupValidator</c>
+    /// in ZB.MOM.WW.ScadaBridge.Host enforces the requirement pre-host for Site nodes only,
+    /// the same way it enforces <c>Communication:GrpcPsk</c>. Central composition roots also
+    /// bind this options type (<c>AddAuditLog</c> is shared between roles) but never resolve
+    /// <see cref="SqliteAuditWriter"/>, so the empty default is inert there and deliberately
+    /// left unvalidated by <see cref="SqliteAuditWriterOptionsValidator"/> (which only checks
+    /// the role-agnostic channel/batch/flush knobs) — enforcing it there too would fail
+    /// central's boot via <c>ValidateOnStart</c>, since <c>AddAuditLog</c> runs on both roles.
+    /// </summary>
+    public string DatabasePath { get; set; } = "";
 
     /// <summary>
     /// Capacity of the bounded write queue. Set high enough that ordinary

src/ZB.MOM.WW.ScadaBridge.AuditLog/Site/SqliteAuditWriterOptionsValidator.cs

@@ -6,19 +6,25 @@ namespace ZB.MOM.WW.ScadaBridge.AuditLog.Site;
 /// Validates <see cref="SqliteAuditWriterOptions"/> at host startup
 /// (arch-review 08 round 2 NF4). The channel/batch/flush knobs feed the
 /// background writer task; a zero anywhere stalls it (nothing drains, nothing
-/// flushes), and an empty <c>DatabasePath</c> leaves the SQLite writer with no
-/// backing store. <see cref="SqliteAuditWriterOptions.BacklogPollIntervalSeconds"/>
+/// flushes). <see cref="SqliteAuditWriterOptions.BacklogPollIntervalSeconds"/>
 /// is intentionally NOT validated — a non-positive value has a documented
 /// fall-back-to-30s contract in <c>SiteAuditBacklogReporter</c>.
 /// </summary>
+/// <remarks>
+/// <see cref="SqliteAuditWriterOptions.DatabasePath"/> is deliberately NOT
+/// validated here (arch-review remediation WP1.2). <c>AddAuditLog</c> runs on
+/// BOTH Central and Site composition roots and binds this options type with
+/// <c>ValidateOnStart</c> either way, but only Site nodes ever resolve
+/// <see cref="SqliteAuditWriter"/> — requiring a non-empty path in this
+/// role-agnostic validator would fail Central's boot too. The requirement is
+/// instead enforced pre-host, Site-role-only, by <c>StartupValidator</c> in
+/// ZB.MOM.WW.ScadaBridge.Host (mirrors how it gates <c>Communication:GrpcPsk</c>).
+/// </remarks>
 public sealed class SqliteAuditWriterOptionsValidator : OptionsValidatorBase<SqliteAuditWriterOptions>
 {
     /// <inheritdoc />
     protected override void Validate(ValidationBuilder builder, SqliteAuditWriterOptions options)
     {
-        builder.RequireThat(!string.IsNullOrWhiteSpace(options.DatabasePath),
-            $"AuditLog:SiteWriter:{nameof(SqliteAuditWriterOptions.DatabasePath)} must be a non-empty path.");
-
         builder.RequireThat(options.ChannelCapacity > 0,
             $"AuditLog:SiteWriter:{nameof(SqliteAuditWriterOptions.ChannelCapacity)} " +
             $"({options.ChannelCapacity}) must be > 0.");

src/ZB.MOM.WW.ScadaBridge.Host/StartupValidator.cs

@@ -159,6 +159,28 @@ public static class StartupValidator
                     + "endpoint under ScadaBridge:Communication:CentralGrpcEndpoints "
                     + "(e.g. http://scadabridge-central-a:8083). Central nodes leave it empty.");
 
+                // The site hot-path audit writer's SQLite file (arch-review remediation
+                // WP1.2). SqliteAuditWriterOptions.DatabasePath has no default (mirrors
+                // LocalDb:Path) — an unset value would previously fall back to a bare
+                // "auditlog.db" resolved relative to the process CWD, which on the docker
+                // rig is the container's ephemeral overlayfs, not the mounted /app/data
+                // volume: the file, and every pending (not-yet-forwarded) audit row in it,
+                // was silently discarded on every container recreate. AddAuditLog binds
+                // this options type on BOTH roles (SqliteAuditWriterOptionsValidator
+                // deliberately does not check DatabasePath there, so Central's boot is
+                // unaffected — see that validator's remarks), so the Site-only requirement
+                // lives here, the same way GrpcPsk is gated just above. NOTE: unlike every
+                // other key in this method, AuditLog:SiteWriter is a TOP-LEVEL config
+                // section (AddAuditLog binds "AuditLog:SiteWriter" off the configuration
+                // root, not "ScadaBridge:AuditLog:SiteWriter") — no ScadaBridge: prefix.
+                p.Require("AuditLog:SiteWriter:DatabasePath",
+                    value => !string.IsNullOrWhiteSpace(value),
+                    "is required for Site nodes: the SQLite hot-path audit writer has no "
+                    + "default path (mirrors LocalDb:Path) — an unset value would silently "
+                    + "resolve to a CWD-relative file on the container's ephemeral overlayfs "
+                    + "and lose the pending audit backlog on every redeploy. Point it at the "
+                    + "mounted data volume, e.g. /app/data/auditlog.db.");
+
                 // ScadaBridge:Database:SiteDbPath was required here until LocalDb
                 // Phase 2. The site's tables now live in the consolidated LocalDb
                 // database (LocalDb:Path, which SiteServiceRegistration requires),

src/ZB.MOM.WW.ScadaBridge.Host/appsettings.Site.json

@@ -80,5 +80,14 @@
   // fails to boot, so every site config must set it.
   "LocalDb": {
     "Path": "./data/site-localdb.db"
+  },
+  // arch-review remediation WP1.2: the site hot-path audit writer's SQLite file has no
+  // default path (mirrors LocalDb:Path above) - AuditLog:SiteWriter:DatabasePath is
+  // REQUIRED and validated pre-host on Site nodes (StartupValidator), the same way
+  // LocalDb:Path is, so every site config must set it.
+  "AuditLog": {
+    "SiteWriter": {
+      "DatabasePath": "./data/auditlog.db"
+    }
   }
 }

tests/ZB.MOM.WW.ScadaBridge.AuditLog.Tests/Site/SqliteAuditWriterOptionsValidatorTests.cs

@@ -5,30 +5,30 @@ namespace ZB.MOM.WW.ScadaBridge.AuditLog.Tests.Site;
 /// <summary>
 /// Eager startup validation for <see cref="SqliteAuditWriterOptions"/>
 /// (arch-review 08 round 2 NF4). The site hot-path writer's channel/batch/flush
-/// knobs must be positive or the background writer task cannot make progress;
-/// an empty <c>DatabasePath</c> would leave the SQLite writer with nowhere to go.
+/// knobs must be positive or the background writer task cannot make progress.
 /// <c>BacklogPollIntervalSeconds</c> is deliberately NOT validated — a
 /// non-positive value has a documented fall-back-to-30s contract.
 /// </summary>
+/// <remarks>
+/// <c>DatabasePath</c> is intentionally NOT covered here (arch-review remediation
+/// WP1.2): it defaults to <c>""</c> (no CWD-relative default — mirrors
+/// <c>LocalDb:Path</c>), but this validator runs on both Central and Site
+/// composition roots via <c>ValidateOnStart</c>, and only Site nodes ever resolve
+/// the writer. The Site-only requirement is enforced pre-host by
+/// <c>StartupValidator</c> in ZB.MOM.WW.ScadaBridge.Host — see
+/// <c>StartupValidatorTests.SiteWithoutAuditLogDatabasePath_FailsValidation</c>.
+/// </remarks>
 public class SqliteAuditWriterOptionsValidatorTests
 {
     [Fact]
     public void DefaultOptions_AreValid()
     {
+        // Includes the empty DatabasePath default — this validator does not check
+        // it (see class remarks); only StartupValidator does, and only for Site nodes.
         var validator = new SqliteAuditWriterOptionsValidator();
         Assert.True(validator.Validate(null, new SqliteAuditWriterOptions()).Succeeded);
     }
 
-    [Fact]
-    public void EmptyDatabasePath_Fails()
-    {
-        var validator = new SqliteAuditWriterOptionsValidator();
-        var result = validator.Validate(null, new SqliteAuditWriterOptions { DatabasePath = "" });
-        Assert.False(result.Succeeded);
-        Assert.Contains(result.Failures!,
-            f => f.Contains(nameof(SqliteAuditWriterOptions.DatabasePath), StringComparison.Ordinal));
-    }
-
     [Fact]
     public void ZeroChannelCapacity_Fails()
     {

tests/ZB.MOM.WW.ScadaBridge.AuditLog.Tests/Site/SqliteAuditWriterWriteTests.cs

@@ -24,7 +24,8 @@ public class SqliteAuditWriterWriteTests
     private static (SqliteAuditWriter writer, string dataSource) CreateWriter(
         string testName,
         int? channelCapacity = null,
-        INodeIdentityProvider? nodeIdentity = null)
+        INodeIdentityProvider? nodeIdentity = null,
+        int? flushIntervalMs = null)
     {
         var dataSource = $"file:{testName}-{Guid.NewGuid():N}?mode=memory&cache=shared";
         var opts = new SqliteAuditWriterOptions { DatabasePath = dataSource };
@@ -32,6 +33,10 @@ public class SqliteAuditWriterWriteTests
         {
             opts.ChannelCapacity = cap;
         }
+        if (flushIntervalMs is int flush)
+        {
+            opts.FlushIntervalMs = flush;
+        }
 
         // Default identity provider returns null — existing tests pre-date
         // SourceNode stamping and have no expectation about it. New stamping
@@ -181,6 +186,69 @@ public class SqliteAuditWriterWriteTests
         Assert.Equal(1000, Convert.ToInt64(sidecarCmd.ExecuteScalar()));
     }
 
+    // ----- FlushIntervalMs soft-flush coalescing (arch-review remediation WP1.2) ----- //
+
+    /// <summary>
+    /// A trickle of events — well under <see cref="SqliteAuditWriterOptions.BatchSize"/>,
+    /// spaced closer together than <see cref="SqliteAuditWriterOptions.FlushIntervalMs"/> —
+    /// must coalesce into ONE transaction rather than fsyncing once per event. This is the
+    /// bug WP1.2 fixes: <c>FlushIntervalMs</c> was validated but never read by the writer
+    /// loop, so every trickle-rate write incurred its own commit (and, under SQLite's
+    /// default synchronous=FULL, its own fsync).
+    /// </summary>
+    [Fact]
+    public async Task WriteAsync_TrickleLoad_CoalescesIntoOneTransaction()
+    {
+        var (writer, dataSource) = CreateWriter(
+            nameof(WriteAsync_TrickleLoad_CoalescesIntoOneTransaction),
+            flushIntervalMs: 500);
+        await using var _ = writer;
+
+        const int count = 5;
+        var writeTasks = new List<Task>(count);
+        for (int i = 0; i < count; i++)
+        {
+            writeTasks.Add(writer.WriteAsync(NewEvent()));
+            await Task.Delay(15); // spaced well under the 500ms flush window
+        }
+        await Task.WhenAll(writeTasks);
+
+        using var connection = OpenVerifierConnection(dataSource);
+        using var cmd = connection.CreateCommand();
+        cmd.CommandText = "SELECT COUNT(*) FROM audit_event;";
+        Assert.Equal(count, Convert.ToInt64(cmd.ExecuteScalar()));
+
+        // The defining assertion: all 5 trickled-in writes landed in a single
+        // FlushBatch transaction, not up to 5 separate commits.
+        Assert.Equal(1, writer.FlushCountForTests);
+    }
+
+    /// <summary>
+    /// The flip side: two events spaced FURTHER apart than
+    /// <see cref="SqliteAuditWriterOptions.FlushIntervalMs"/> must NOT be held open
+    /// waiting for a partner — the deadline bounds worst-case added latency, it does
+    /// not turn into an unbounded debounce.
+    /// </summary>
+    [Fact]
+    public async Task WriteAsync_EventsSpacedBeyondFlushInterval_FlushSeparately()
+    {
+        var (writer, dataSource) = CreateWriter(
+            nameof(WriteAsync_EventsSpacedBeyondFlushInterval_FlushSeparately),
+            flushIntervalMs: 50);
+        await using var _ = writer;
+
+        await writer.WriteAsync(NewEvent());
+        await Task.Delay(300); // well beyond the 50ms flush window
+        await writer.WriteAsync(NewEvent());
+
+        using var connection = OpenVerifierConnection(dataSource);
+        using var cmd = connection.CreateCommand();
+        cmd.CommandText = "SELECT COUNT(*) FROM audit_event;";
+        Assert.Equal(2, Convert.ToInt64(cmd.ExecuteScalar()));
+
+        Assert.Equal(2, writer.FlushCountForTests);
+    }
+
     [Fact]
     public async Task WriteAsync_DuplicateEventId_FirstWriteWins_NoException()
     {

tests/ZB.MOM.WW.ScadaBridge.Host.Tests/SiteHealthEndpointTests.cs

@@ -27,10 +27,12 @@ public class SiteHealthEndpointTests : IDisposable
     private readonly List<IDisposable> _disposables = new();
     private readonly Dictionary<string, string?> _previousEnv = new(StringComparer.Ordinal);
     private readonly string _tempDbPath;
+    private readonly string _tempAuditDbPath;
 
     public SiteHealthEndpointTests()
     {
         _tempDbPath = Path.Combine(Path.GetTempPath(), $"scadabridge_health_ep_{Guid.NewGuid()}.db");
+        _tempAuditDbPath = Path.Combine(Path.GetTempPath(), $"scadabridge_health_ep_audit_{Guid.NewGuid()}.db");
 
         // Whole-key env overrides, the sanctioned path: supplying GrpcPsk concretely makes the
         // pre-host secrets expander skip appsettings.Site.json's ${secret:SB-GRPC-PSK-site-1}
@@ -50,6 +52,11 @@ public class SiteHealthEndpointTests : IDisposable
         SetEnv("ScadaBridge__Cluster__SeedNodes__1", "akka.tcp://scadabridge@localhost:18085");
         SetEnv("ScadaBridge__Communication__GrpcPsk", "test-psk-0123456789");
         SetEnv("LocalDb__Path", _tempDbPath);
+        // arch-review remediation WP1.2: SqliteAuditWriterOptions.DatabasePath has no default
+        // and StartupValidator now requires it for Site nodes — same reason LocalDb__Path is
+        // overridden above (appsettings.Site.json's own default is CWD-relative and would
+        // otherwise litter the test working directory when SiteAuditBacklogReporter probes it).
+        SetEnv("AuditLog__SiteWriter__DatabasePath", _tempAuditDbPath);
     }
 
     private void SetEnv(string key, string? value)
@@ -71,6 +78,7 @@ public class SiteHealthEndpointTests : IDisposable
         }
 
         try { File.Delete(_tempDbPath); } catch { /* best effort */ }
+        try { File.Delete(_tempAuditDbPath); } catch { /* best effort */ }
 
         GC.SuppressFinalize(this);
     }

tests/ZB.MOM.WW.ScadaBridge.Host.Tests/StartupValidatorTests.cs

@@ -44,6 +44,10 @@ public class StartupValidatorTests
         // Phase 4: gRPC (CentralControlService) is the only site→central transport, so a Site
         // node must list at least one central gRPC endpoint to dial (no Akka fallback remains).
         ["ScadaBridge:Communication:CentralGrpcEndpoints:0"] = "http://central-a:8083",
+        // arch-review remediation WP1.2: the site hot-path audit writer's SQLite file has no
+        // default path (mirrors LocalDb:Path) — required so it lands on the mounted data volume,
+        // not the container's ephemeral overlayfs.
+        ["AuditLog:SiteWriter:DatabasePath"] = "/app/data/auditlog.db",
     };
 
     [Fact]
@@ -124,6 +128,43 @@ public class StartupValidatorTests
         Assert.Null(Record.Exception(() => StartupValidator.Validate(config)));
     }
 
+    [Fact]
+    public void SiteWithoutAuditLogDatabasePath_FailsValidation()
+    {
+        // arch-review remediation WP1.2: SqliteAuditWriterOptions.DatabasePath has no default
+        // (mirrors LocalDb:Path). An unset value used to fall back to a bare "auditlog.db"
+        // resolved relative to CWD — on the docker rig, the container's ephemeral overlayfs —
+        // so the node booted, looked healthy, and lost its pending audit backlog on every
+        // recreate. Fail fast at boot instead.
+        var values = ValidSiteConfig();
+        values.Remove("AuditLog:SiteWriter:DatabasePath");
+        var config = BuildConfig(values);
+
+        var ex = Assert.Throws<InvalidOperationException>(() => StartupValidator.Validate(config));
+        Assert.Contains("DatabasePath", ex.Message);
+    }
+
+    [Fact]
+    public void SiteWithBlankAuditLogDatabasePath_FailsValidation()
+    {
+        var values = ValidSiteConfig();
+        values["AuditLog:SiteWriter:DatabasePath"] = "   ";
+        var config = BuildConfig(values);
+
+        var ex = Assert.Throws<InvalidOperationException>(() => StartupValidator.Validate(config));
+        Assert.Contains("DatabasePath", ex.Message);
+    }
+
+    [Fact]
+    public void CentralWithoutAuditLogDatabasePath_PassesValidation()
+    {
+        // AddAuditLog binds SqliteAuditWriterOptions on both roles, but only Site nodes ever
+        // resolve the writer — the requirement must not fire for Central.
+        var config = BuildConfig(ValidCentralConfig());
+
+        Assert.Null(Record.Exception(() => StartupValidator.Validate(config)));
+    }
+
     [Fact]
     public void MissingRole_FailsValidation()
     {