diff --git a/GitLfsCache.Tests/Tool/StoreFlagTests.cs b/GitLfsCache.Tests/Tool/StoreFlagTests.cs
new file mode 100644
index 0000000..e5a0944
--- /dev/null
+++ b/GitLfsCache.Tests/Tool/StoreFlagTests.cs
@@ -0,0 +1,40 @@
+// Copyright (c) 2023-2026 ktsu-dev contributors
+
+namespace ktsu.GitLfsCache.Tests.Tool;
+
+using ktsu.GitLfsCache.Tool;
+
+[TestClass]
+public class StoreFlagTests
+{
+	[TestMethod]
+	public void Store_RelativeDirectory_ResolvesAgainstTheWorkingDirectory()
+	{
+		// The options validator refuses a root that is not fully qualified, so passing `--store ./cache`
+		// through verbatim aborted startup with a validation stack trace.
+		string resolved = Program.ResolveStoreRoot("./cache");
+
+		Assert.IsTrue(Path.IsPathFullyQualified(resolved), resolved);
+		Assert.AreEqual(Path.Combine(Environment.CurrentDirectory, "cache"), resolved);
+	}
+
+	[TestMethod]
+	public async Task Store_RelativeDirectory_IsAcceptedByTheCommandLine()
+	{
+		// The invalid upstream stops the run after the flags are read and before a server starts, so a
+		// relative --store reaches the same one-line failure path as any other flag mistake.
+		int exitCode = await Program.Main(["--store", "./cache", "--upstream", "not-a-name-url-pair"]);
+
+		Assert.AreEqual(1, exitCode);
+	}
+
+	[TestMethod]
+	public void Store_FullyQualifiedDirectory_IsKeptAsGiven()
+	{
+		string root = Path.Combine(
+			Path.GetPathRoot(Path.GetTempPath()) ?? Path.DirectorySeparatorChar.ToString(),
+			"gitlfscache");
+
+		Assert.AreEqual(root, Program.ResolveStoreRoot(root));
+	}
+}
diff --git a/GitLfsCache.Tool/Program.cs b/GitLfsCache.Tool/Program.cs
index 94825bb..d7c0655 100644
--- a/GitLfsCache.Tool/Program.cs
+++ b/GitLfsCache.Tool/Program.cs
@@ -29,7 +29,7 @@ internal static class Program
 	/// <summary>The configuration key the <c>--token-key</c> flag overrides.</summary>
 	private const string TokenKeyKey = "GitLfsCache:TokenKeys:0";
 
-	private static async Task<int> Main(string[] args)
+	internal static async Task<int> Main(string[] args)
 	{
 		Option<int?> port = new("--port", "-p")
 		{
@@ -110,7 +110,7 @@ private static async Task<int> Main(string[] args)
 
 			if (parseResult.GetValue(store) is string storeRoot)
 			{
-				overrides[StoreRootKey] = storeRoot;
+				overrides[StoreRootKey] = ResolveStoreRoot(storeRoot);
 			}
 
 			if (parseResult.GetValue(maxSize) is string budget)
@@ -285,6 +285,19 @@ private static bool TryApplyUpstreams(
 		return true;
 	}
 
+	/// <summary>
+	/// Resolves the <c>--store</c> flag against the working directory.
+	/// </summary>
+	/// <remarks>
+	/// The options validator requires a fully qualified root, which keeps configuration files and
+	/// environment variables strict for container deployments. A relative directory is what someone
+	/// running the tool locally types, though, so the flag resolves it the way <c>--config</c> does
+	/// rather than letting startup fail with a validation stack trace.
+	/// </remarks>
+	/// <param name="storeRoot">The directory as given on the command line.</param>
+	/// <returns>The fully qualified directory.</returns>
+	internal static string ResolveStoreRoot(string storeRoot) => Path.GetFullPath(storeRoot);
+
 	/// <summary>
 	/// Groups every <c>--allow</c> flag by the upstream it names.
 	/// </summary>