diff --git a/.claude-plugin/plugin.json b/.claude-plugin/plugin.json
index a052e94..72320f4 100644
--- a/.claude-plugin/plugin.json
+++ b/.claude-plugin/plugin.json
@@ -2,7 +2,7 @@
   "$schema": "https://json.schemastore.org/claude-code-plugin-manifest.json",
   "name": "signs-of-ai",
   "description": "Measure a text for the signs of AI writing and read back the evidence — offline, EN/ES, with the tool's own false-positive rate attached.",
-  "version": "0.4.0",
+  "version": "0.7.1",
   "author": {
     "name": "Pedro Hernández — PeopleWorks",
     "url": "https://github.com/peopleworks"
diff --git a/tests/SignsOfAI.Core.Tests/ReleaseVersionTests.cs b/tests/SignsOfAI.Core.Tests/ReleaseVersionTests.cs
new file mode 100644
index 0000000..e132f3c
--- /dev/null
+++ b/tests/SignsOfAI.Core.Tests/ReleaseVersionTests.cs
@@ -0,0 +1,75 @@
+using System.Text.RegularExpressions;
+using Xunit;
+
+namespace SignsOfAI.Core.Tests;
+
+/// <summary>
+/// The version is typed into seven places across five files, and a release bumps them by hand.
+/// <c>.claude-plugin/plugin.json</c> was three releases behind — it said 0.4.0 while every channel
+/// shipped 0.7.1 — and nothing failed, because the release checklist never listed it.
+///
+/// That file is what a plugin directory reads, which makes it the version a stranger sees first.
+/// So this holds every one of them to the engine's own, and fails by file name when a release
+/// forgets one. The eighth time something this project says about itself went stale.
+/// </summary>
+public class ReleaseVersionTests
+{
+    private static readonly string Root = FindRoot();
+
+    /// <summary>The authority: what SignsOfAI.Core ships as.</summary>
+    private static readonly string Engine = Read(
+        Path.Combine("src", "SignsOfAI.Core", "SignsOfAI.Core.csproj"),
+        @"<Version>(?<v>[^<]+)</Version>");
+
+    private static string FindRoot()
+    {
+        var dir = new DirectoryInfo(AppContext.BaseDirectory);
+        while (dir is not null && !Directory.Exists(Path.Combine(dir.FullName, "src")))
+            dir = dir.Parent;
+
+        Assert.NotNull(dir);
+        return dir!.FullName;
+    }
+
+    private static string Read(string relativePath, string pattern)
+    {
+        var text = File.ReadAllText(Path.Combine(Root, relativePath));
+        var match = Regex.Match(text, pattern);
+        Assert.True(match.Success, $"{relativePath} no longer carries a version matching {pattern}.");
+        return match.Groups["v"].Value.Trim();
+    }
+
+    public static TheoryData<string, string> Declarations() => new()
+    {
+        // Published to NuGet.
+        { Path.Combine("src", "SignsOfAI.Cli", "SignsOfAI.Cli.csproj"), @"<Version>(?<v>[^<]+)</Version>" },
+        { Path.Combine("src", "SignsOfAI.Mcp", "SignsOfAI.Mcp.csproj"), @"<Version>(?<v>[^<]+)</Version>" },
+        // What the download page offers, which the release workflow also enforces.
+        { Path.Combine("src", "SignsOfAI.UI", "Services", "DesktopRelease.cs"),
+          @"public const string Version = ""(?<v>[^""]+)"";" },
+        // What a plugin directory shows a stranger. This is the one that drifted.
+        { Path.Combine(".claude-plugin", "plugin.json"), @"""version"":\s*""(?<v>[^""]+)""" },
+    };
+
+    [Theory]
+    [MemberData(nameof(Declarations))]
+    public void Every_shipped_manifest_declares_the_engine_version(string relativePath, string pattern)
+    {
+        Assert.True(Engine == Read(relativePath, pattern),
+            $"{relativePath} says {Read(relativePath, pattern)} and the engine ships {Engine}. "
+            + "A release bumps all of them or none of them.");
+    }
+
+    [Fact]
+    public void The_mcp_registry_manifest_declares_it_in_both_places()
+    {
+        // server.json carries the version twice, and publishing with them out of step is rejected by
+        // the registry after NuGet has already gone out — the worst moment to find out.
+        var path = Path.Combine("src", "SignsOfAI.Mcp", ".mcp", "server.json");
+        var found = Regex.Matches(File.ReadAllText(Path.Combine(Root, path)),
+            @"""version"":\s*""(?<v>[^""]+)""").Select(m => m.Groups["v"].Value).ToList();
+
+        Assert.Equal(2, found.Count);
+        Assert.All(found, v => Assert.Equal(Engine, v));
+    }
+}