diff --git a/ZB.MOM.WW.Configuration/src/ZB.MOM.WW.Configuration/ConfigPreflight.cs b/ZB.MOM.WW.Configuration/src/ZB.MOM.WW.Configuration/ConfigPreflight.cs
new file mode 100644
index 0000000..0ebfff6
--- /dev/null
+++ b/ZB.MOM.WW.Configuration/src/ZB.MOM.WW.Configuration/ConfigPreflight.cs
@@ -0,0 +1,75 @@
+using Microsoft.Extensions.Configuration;
+
+namespace ZB.MOM.WW.Configuration;
+
+/// <summary>
+/// Fluent aggregator for validating raw <see cref="IConfiguration"/> BEFORE the host/DI container
+/// exists (e.g. pre-Akka startup). Collects all failures and surfaces them together via
+/// <see cref="ThrowIfInvalid"/>. For options that flow through DI, prefer
+/// <see cref="ServiceCollectionExtensions.AddValidatedOptions{TOptions, TValidator}"/>.
+/// </summary>
+public sealed class ConfigPreflight
+{
+    private readonly IConfiguration _configuration;
+    private readonly List<string> _failures = [];
+
+    private ConfigPreflight(IConfiguration configuration) => _configuration = configuration;
+
+    /// <summary>Starts a preflight over <paramref name="configuration"/>.</summary>
+    public static ConfigPreflight For(IConfiguration configuration)
+    {
+        ArgumentNullException.ThrowIfNull(configuration);
+        return new ConfigPreflight(configuration);
+    }
+
+    /// <summary>The accumulated failure messages (empty when valid).</summary>
+    public IReadOnlyList<string> Failures => _failures;
+
+    /// <summary>True when no failures have been accumulated.</summary>
+    public bool IsValid => _failures.Count == 0;
+
+    /// <summary>Requires the value at <paramref name="key"/> to satisfy <paramref name="predicate"/>.</summary>
+    public ConfigPreflight Require(string key, Func<string?, bool> predicate, string reason)
+    {
+        ArgumentNullException.ThrowIfNull(predicate);
+        if (!predicate(_configuration[key])) _failures.Add($"{key} {reason}");
+        return this;
+    }
+
+    /// <summary>Requires a non-empty value at <paramref name="key"/>.</summary>
+    public ConfigPreflight RequireValue(string key) => AddIf(Checks.Required(_configuration[key], key));
+
+    /// <summary>Requires a valid integer TCP port (1-65535) at <paramref name="key"/>.</summary>
+    public ConfigPreflight RequirePort(string key)
+    {
+        var raw = _configuration[key];
+        if (!int.TryParse(raw, out var port))
+        {
+            _failures.Add($"{key} must be an integer port 1-65535 (was '{raw ?? "null"}')");
+            return this;
+        }
+        return AddIf(Checks.Port(port, key));
+    }
+
+    /// <summary>Runs <paramref name="block"/> only when <paramref name="condition"/> holds (role-conditional rules).</summary>
+    public ConfigPreflight When(bool condition, Action<ConfigPreflight> block)
+    {
+        ArgumentNullException.ThrowIfNull(block);
+        if (condition) block(this);
+        return this;
+    }
+
+    /// <summary>Throws <see cref="InvalidOperationException"/> listing all failures when invalid; otherwise returns.</summary>
+    public void ThrowIfInvalid()
+    {
+        if (_failures.Count > 0)
+            throw new InvalidOperationException(
+                $"Configuration validation failed:\n{string.Join("\n", _failures.Select(e => $"  - {e}"))}");
+    }
+
+    private ConfigPreflight AddIf(string? message)
+    {
+        if (message is not null) _failures.Add(message);
+        return this;
+    }
+}
diff --git a/ZB.MOM.WW.Configuration/tests/ZB.MOM.WW.Configuration.Tests/ConfigPreflightTests.cs b/ZB.MOM.WW.Configuration/tests/ZB.MOM.WW.Configuration.Tests/ConfigPreflightTests.cs
new file mode 100644
index 0000000..8b8428d
--- /dev/null
+++ b/ZB.MOM.WW.Configuration/tests/ZB.MOM.WW.Configuration.Tests/ConfigPreflightTests.cs
@@ -0,0 +1,49 @@
+using Microsoft.Extensions.Configuration;
+using ZB.MOM.WW.Configuration;
+
+namespace ZB.MOM.WW.Configuration.Tests;
+
+public sealed class ConfigPreflightTests
+{
+    private static IConfiguration Config(Dictionary<string, string?> values) =>
+        new ConfigurationBuilder().AddInMemoryCollection(values).Build();
+
+    [Fact]
+    public void Aggregates_all_failures()
+    {
+        var cfg = Config(new() { ["Node:Role"] = "Bogus", ["Node:RemotingPort"] = "0" });
+        var pf = ConfigPreflight.For(cfg)
+            .Require("Node:Role", v => v is "Central" or "Site", "must be 'Central' or 'Site'")
+            .RequirePort("Node:RemotingPort");
+        Assert.False(pf.IsValid);
+        Assert.Equal(2, pf.Failures.Count);
+    }
+
+    [Fact]
+    public void When_runs_block_only_if_condition_true()
+    {
+        var cfg = Config(new() { ["Node:Role"] = "Site" });
+        var pf = ConfigPreflight.For(cfg)
+            .When(cfg["Node:Role"] == "Site",
+                p => p.RequireValue("Node:SiteId"));
+        Assert.False(pf.IsValid);              // SiteId missing
+        Assert.Contains(pf.Failures, f => f.Contains("Node:SiteId"));
+    }
+
+    [Fact]
+    public void ThrowIfInvalid_throws_aggregated_message()
+    {
+        var cfg = Config(new() { ["Node:Name"] = "" });
+        var ex = Assert.Throws<InvalidOperationException>(() =>
+            ConfigPreflight.For(cfg).RequireValue("Node:Name").ThrowIfInvalid());
+        Assert.StartsWith("Configuration validation failed:", ex.Message);
+        Assert.Contains("  - Node:Name", ex.Message);
+    }
+
+    [Fact]
+    public void ThrowIfInvalid_is_noop_when_valid()
+    {
+        var cfg = Config(new() { ["Node:Name"] = "ok" });
+        ConfigPreflight.For(cfg).RequireValue("Node:Name").ThrowIfInvalid();   // does not throw
+    }
+}