diff --git a/Schema.Test/SchemaDataSourceTests.cs b/Schema.Test/SchemaDataSourceTests.cs
index 62421a3..770098d 100644
--- a/Schema.Test/SchemaDataSourceTests.cs
+++ b/Schema.Test/SchemaDataSourceTests.cs
@@ -107,6 +107,71 @@ public void TestCodeGeneratorOutputPathResolves()
 		Assert.AreEqual(Path.GetFullPath(Path.Combine(workingDirectory, "generated")), resolved.ToString());
 	}
 
+	/// <summary>
+	/// A resolved path is normalised, not merely concatenated. A schema beside the data it
+	/// describes is the easy case; one that reaches a sibling directory through <c>..</c> is the
+	/// case that tells a resolver from a string join, and the resolved value is compared,
+	/// displayed and used as a key, so it has to come back as the directory it names rather than
+	/// as a route to it.
+	/// </summary>
+	[TestMethod]
+	public void TestFilePathsResolveThroughTraversalSegments()
+	{
+		Schema schema = CreateAnchoredSchema("../shared/./items.json");
+
+		Assert.IsTrue(schema.GetDataSource("Items".As<DataSourceName>())!.TryResolveFile(out AbsoluteFilePath resolved));
+		Assert.AreEqual(
+			Path.GetFullPath(Path.Combine(workingDirectory, "../shared/./items.json")),
+			resolved.ToString());
+		Assert.IsFalse(resolved.ToString().Contains("..", StringComparison.Ordinal), resolved.ToString());
+	}
+
+	[TestMethod]
+	public void TestDirectoryPathsResolveThroughTraversalSegments()
+	{
+		Schema schema = CreateAnchoredSchema();
+		SchemaCodeGenerator generator = schema.AddCodeGenerator("CSharp".As<CodeGeneratorName>())!;
+		generator.OutputPath = "../build/./generated".As<RelativeDirectoryPath>();
+
+		Assert.IsTrue(generator.TryResolveOutputPath(out AbsoluteDirectoryPath resolved));
+		Assert.AreEqual(
+			Path.GetFullPath(Path.Combine(workingDirectory, "../build/./generated")),
+			resolved.ToString());
+		Assert.IsFalse(resolved.ToString().Contains("..", StringComparison.Ordinal), resolved.ToString());
+	}
+
+	/// <summary>
+	/// The anchor is the directory holding the schema file, and nothing else about the file.
+	/// </summary>
+	[TestMethod]
+	public void TestTheAnchorIsTheSchemaFilesDirectory()
+	{
+		Schema schema = new();
+		schema.SetSourceFile(SchemaPath);
+
+		Assert.AreEqual(workingDirectory, schema.SourceDirectory.ToString());
+		Assert.AreEqual("test.schema.json", schema.SourceFileName);
+	}
+
+	/// <summary>
+	/// Anchoring a schema must not disturb the path it was handed. Callers pass an instance they
+	/// keep using - the editor records the same one as a recent file straight afterwards - and
+	/// reading <c>AbsoluteFilePath.AbsoluteDirectoryPath</c> to find the anchor silently breaks
+	/// equality and the hash code of the instance it is read from (ktsu.Semantics.Paths 5.4.2),
+	/// while leaving its text alone. That is why the anchor is still taken from the string.
+	/// </summary>
+	[TestMethod]
+	public void TestSettingTheSourceFileLeavesTheCallersPathEqualToItself()
+	{
+		AbsoluteFilePath handedIn = SchemaPath;
+		AbsoluteFilePath untouched = SchemaPath;
+
+		new Schema().SetSourceFile(handedIn);
+
+		Assert.AreEqual(untouched, handedIn, "Anchoring the schema changed the path it was given.");
+		Assert.AreEqual(untouched.GetHashCode(), handedIn.GetHashCode(), "Anchoring the schema changed the hash code of the path it was given.");
+	}
+
 	[TestMethod]
 	public void TestLoadWithASourcePathAnchorsTheSchema()
 	{
diff --git a/Schema/Models/Schema.Paths.cs b/Schema/Models/Schema.Paths.cs
index 646dff8..eecf914 100644
--- a/Schema/Models/Schema.Paths.cs
+++ b/Schema/Models/Schema.Paths.cs
@@ -16,6 +16,19 @@ namespace ktsu.Schema.Models;
 /// The anchor is supplied by whoever read the file, so the serializer itself stays free of the
 /// filesystem. A schema that was never read from a file has no anchor and cannot resolve
 /// anything, which every resolution API reports rather than guessing at the working directory.
+///
+/// Resolution goes through <c>AsAbsolute</c> rather than the <c>/</c> combine operator: a schema
+/// may reach a sibling directory through <c>..</c>, and only the former normalises those segments
+/// away. The operator joins, which hands back a route to the file rather than the file.
+///
+/// The anchor is still taken with <see cref="Path.GetDirectoryName(string)"/> rather than
+/// <c>AbsoluteFilePath.AbsoluteDirectoryPath</c>, which would read better. Reading that property
+/// mutates the instance it is read from: in <c>ktsu.Semantics.Paths</c> 5.4.2 an
+/// <c>AbsoluteFilePath</c> stops comparing equal to an identical one, and its hash code changes,
+/// once the property has been touched, while its text stays the same. Callers hand the same
+/// instance on afterwards - the editor records it as a recent file - so reading it here corrupted
+/// equality for a value this code does not own. <c>AsAbsolute</c> carries no such hazard, which is
+/// why only the resolution moved.
 /// </remarks>
 public partial class Schema
 {
@@ -40,7 +53,7 @@ public bool TryResolvePath(RelativeFilePath relativePath, out AbsoluteFilePath r
 			return false;
 		}
 
-		resolved = Path.GetFullPath(Path.Combine(SourceDirectory, relativePath)).As<AbsoluteFilePath>();
+		resolved = relativePath.AsAbsolute(SourceDirectory);
 		return true;
 	}
 
@@ -59,7 +72,7 @@ public bool TryResolvePath(RelativeDirectoryPath relativePath, out AbsoluteDirec
 			return false;
 		}
 
-		resolved = Path.GetFullPath(Path.Combine(SourceDirectory, relativePath)).As<AbsoluteDirectoryPath>();
+		resolved = relativePath.AsAbsolute(SourceDirectory);
 		return true;
 	}