diff --git a/code-reviews/Driver.Historian.Wonderware.Client.Contracts/findings.md b/code-reviews/Driver.Historian.Wonderware.Client.Contracts/findings.md
new file mode 100644
index 00000000..972f19a2
--- /dev/null
+++ b/code-reviews/Driver.Historian.Wonderware.Client.Contracts/findings.md
@@ -0,0 +1,139 @@
+# Code Review — Driver.Historian.Wonderware.Client.Contracts
+
+| Field | Value |
+|---|---|
+| Module | `src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware.Client.Contracts` |
+| Reviewer | Claude Code |
+| Review date | 2026-06-19 |
+| Commit reviewed | `a19b0f86` |
+| Status | Reviewed |
+| Open findings | 0 |
+
+## Checklist coverage
+
+A comprehensive review completes every category, recording "No issues found" where
+a category produced nothing rather than leaving it blank.
+
+| # | Category | Result |
+|---|---|---|
+| 1 | Correctness & logic bugs | Driver.Historian.Wonderware.Client.Contracts-003 |
+| 2 | OtOpcUa conventions | No issues found |
+| 3 | Concurrency & thread safety | No issues found |
+| 4 | Error handling & resilience | No issues found |
+| 5 | Security | Driver.Historian.Wonderware.Client.Contracts-001, Driver.Historian.Wonderware.Client.Contracts-002 |
+| 6 | Performance & resource management | No issues found |
+| 7 | Design-document adherence | No issues found |
+| 8 | Code organization & conventions | No issues found |
+| 9 | Testing coverage | No test project — per review instructions; verified by build only |
+| 10 | Documentation & comments | Driver.Historian.Wonderware.Client.Contracts-004 |
+
+## Findings
+
+### Driver.Historian.Wonderware.Client.Contracts-001
+
+| Field | Value |
+|---|---|
+| Severity | High |
+| Category | Security |
+| Location | `WonderwareHistorianClientOptions.cs:24-30` |
+| Status | Resolved |
+
+**Description:** `WonderwareHistorianClientOptions` is a `sealed record`. The C# compiler
+auto-generates a `ToString()` for records that includes every positional constructor
+parameter by name and value — in this case including `SharedSecret`. If the options object
+is ever passed to structured logging (e.g. `_logger.LogDebug("{opts}", options)`), printed
+in an exception message, surfaced in a health-check endpoint, or serialized by a framework
+that calls `ToString()`, the shared secret will appear in plain text in log files or HTTP
+responses. There is currently no `ToString()` override to redact it. The
+`FrameChannel.ConnectInternalAsync` log line in the sibling project does not log `_options`
+directly, so there is no active leak today, but the type is a latent trap for any future
+logging addition.
+
+**Recommendation:** Override `ToString()` to redact the secret, including only the
+non-sensitive connection fields (Host, Port, PeerName, UseTls, ServerCertThumbprint).
+
+**Resolution:** Resolved 2026-06-19 — added `override ToString()` to the record that
+outputs Host, Port, PeerName, UseTls, and ServerCertThumbprint only, omitting
+SharedSecret; verified by build (no test project for this module). `dotnet build` on both
+the Contracts project and the consumer Client project passes with 0 errors/warnings.
+
+---
+
+### Driver.Historian.Wonderware.Client.Contracts-002
+
+| Field | Value |
+|---|---|
+| Severity | Medium |
+| Category | Security |
+| Location | `WonderwareHistorianClientOptions.cs:50-54` |
+| Status | Deferred |
+
+**Description:** `ServerCertThumbprint` is documented as a "SHA-1 thumbprint". The
+consumer (`FrameChannel.DefaultTcpConnectFactory`, sibling project) pins via the no-arg
+`GetCertHashString()` overload, which returns a 40-character SHA-1 hex string. SHA-1 is
+a deprecated hash algorithm for certificate identification. An operator following current
+tooling (Windows Certificate Manager, `certutil -sha256`, `openssl x509 -fingerprint
+-sha256`) would supply a 64-character SHA-256 thumbprint, which will silently never match
+and cause every TLS handshake to fail with a generic auth error and no indication that the
+algorithm mismatch is the cause.
+
+**Recommendation:** Upgrade the consumer to `cert.GetCertHashString(HashAlgorithmName.SHA256)`
+and update the doc to require a 64-char SHA-256 thumbprint. This requires a coordinated
+change to `FrameChannel.DefaultTcpConnectFactory` in the `Client` project (not a
+wire-contract change). Until then the doc has been updated (finding 004) to explicitly warn
+operators that only 40-char SHA-1 thumbprints are accepted.
+
+**Resolution:** Deferred — the fix requires editing `FrameChannel.DefaultTcpConnectFactory`
+in the sibling `Client` project, outside this Contracts module's scope. The documentation
+has been updated (finding 004 fix) to warn operators of the SHA-1-only constraint. Track
+as a follow-up in the `Client` module's review.
+
+---
+
+### Driver.Historian.Wonderware.Client.Contracts-003
+
+| Field | Value |
+|---|---|
+| Severity | Medium |
+| Category | Correctness & logic bugs |
+| Location | `WonderwareHistorianClientOptions.cs:26` |
+| Status | Resolved |
+
+**Description:** The `Port` positional constructor parameter has no `[Range]` validation
+attribute (unlike `ProbeTimeoutSeconds`, which carries `[Range(1, 60)]`). A misconfigured
+zero, negative, or out-of-range port (valid TCP range 1–65535) passes construction
+silently. The consumer then fails at `TcpClient.ConnectAsync` time with a `SocketException`
+whose error gives no hint that the port value is invalid. The sibling
+`ServerHistorianOptions.Validate()` warns on `Port <= 0` at startup, but that fires only
+if the read-path historian is wired; write-path-only or probe-only usage has no guard.
+
+**Recommendation:** Add `[Range(1, 65535)]` on the `Port` positional parameter.
+
+**Resolution:** Resolved 2026-06-19 — added `[Range(1, 65535)]` to the `Port` positional
+parameter; also updated the `<param name="Port">` XML doc to state the valid range.
+Build passes with 0 errors/warnings on both the Contracts and consumer Client projects.
+
+---
+
+### Driver.Historian.Wonderware.Client.Contracts-004
+
+| Field | Value |
+|---|---|
+| Severity | Low |
+| Category | Documentation & comments |
+| Location | `WonderwareHistorianClientOptions.cs:50-54` |
+| Status | Resolved |
+
+**Description:** The `ServerCertThumbprint` XML doc said "SHA-1 thumbprint (hex, no
+spaces)" but did not state the expected length (40 hex characters for SHA-1). An operator
+supplying a SHA-256 thumbprint (64 hex chars — the format shown by modern tooling) would
+get a silent TLS handshake failure. The doc also did not explain which hash algorithm the
+consumer uses or why SHA-256 thumbprints will not work.
+
+**Recommendation:** Update the XML doc to state the 40-character SHA-1 constraint
+explicitly and warn that SHA-256 thumbprints will silently fail.
+
+**Resolution:** Resolved 2026-06-19 — updated the `ServerCertThumbprint` XML doc to state
+"40 hex characters, no spaces, case-insensitive" and added a `<remarks>` block explaining
+that the consumer uses `GetCertHashString()` (SHA-1) and that a 64-char SHA-256 thumbprint
+will silently never match. Build passes with 0 errors/warnings.
diff --git a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware.Client.Contracts/WonderwareHistorianClientOptions.cs b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware.Client.Contracts/WonderwareHistorianClientOptions.cs
index 4e7c7257..afe856ee 100644
--- a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware.Client.Contracts/WonderwareHistorianClientOptions.cs
+++ b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware.Client.Contracts/WonderwareHistorianClientOptions.cs
@@ -16,14 +16,14 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware.Client;
 ///     </para>
 /// </remarks>
 /// <param name="Host">Sidecar TCP host (DNS name or IP) the client dials.</param>
-/// <param name="Port">Sidecar TCP port (matches the sidecar's <c>OTOPCUA_HISTORIAN_TCP_PORT</c>).</param>
+/// <param name="Port">Sidecar TCP port (matches the sidecar's <c>OTOPCUA_HISTORIAN_TCP_PORT</c>). Valid range: 1–65535.</param>
 /// <param name="SharedSecret">Per-process shared secret the sidecar will verify in the Hello frame.</param>
 /// <param name="PeerName">Diagnostic peer identifier sent in Hello — typically the OtOpcUa instance id.</param>
 /// <param name="ConnectTimeout">Cap on the TCP connect + Hello round trip on each (re)connect.</param>
 /// <param name="CallTimeout">Cap on a single read/write call once connected.</param>
 public sealed record WonderwareHistorianClientOptions(
     string Host,
-    int Port,
+    [Range(1, 65535)] int Port,
     string SharedSecret,
     string PeerName = "OtOpcUa",
     TimeSpan? ConnectTimeout = null,
@@ -47,9 +47,25 @@ public sealed record WonderwareHistorianClientOptions(
     public bool UseTls { get; init; }
 
     /// <summary>
-    ///     Optional SHA-1 thumbprint (hex, no spaces) the client pins the sidecar's TLS server
-    ///     cert against. When null/empty and <see cref="UseTls"/> is true, the client validates
-    ///     the cert chain normally (CA-issued cert).
+    ///     Optional SHA-1 thumbprint (40 hex characters, no spaces, case-insensitive) the client
+    ///     pins the sidecar's TLS server cert against. When null/empty and
+    ///     <see cref="UseTls"/> is true, the client validates the cert chain normally
+    ///     (CA-issued cert).
     /// </summary>
+    /// <remarks>
+    ///     The consumer matches against <c>X509Certificate.GetCertHashString()</c> (SHA-1, 40
+    ///     hex chars). Supplying a SHA-256 thumbprint (64 hex chars, the format shown by modern
+    ///     tooling such as <c>certutil</c> or Windows Certificate Manager) will never match and
+    ///     will cause the TLS handshake to fail silently. Only 40-character SHA-1 hex strings
+    ///     are accepted.
+    /// </remarks>
     public string? ServerCertThumbprint { get; init; }
+
+    /// <inheritdoc/>
+    /// <remarks>
+    ///     Redacts <see cref="SharedSecret"/> so the value cannot appear in log output when the
+    ///     options object is passed to a structured-logging statement.
+    /// </remarks>
+    public override string ToString() =>
+        $"WonderwareHistorianClientOptions {{ Host={Host}, Port={Port}, PeerName={PeerName}, UseTls={UseTls}, ServerCertThumbprint={ServerCertThumbprint ?? "<null>"} }}";
 }