diff --git a/src/AquaSynth.Core/IpaGestureExperiment.cs b/src/AquaSynth.Core/IpaGestureExperiment.cs
index aead558..ec5e562 100644
--- a/src/AquaSynth.Core/IpaGestureExperiment.cs
+++ b/src/AquaSynth.Core/IpaGestureExperiment.cs
@@ -108,7 +108,7 @@ public static class IpaGestureExperiment
             throw new ArgumentException("At least one experiment variant is required.", nameof(variants));
         }
 
-        var roundDirectory = Path.Combine(rootDirectory, SafeFileName(roundId));
+        var roundDirectory = Path.Combine(rootDirectory, StoreFileName.From(roundId));
         var candidateDirectory = Path.Combine(roundDirectory, "candidates");
         var timelineDirectory = Path.Combine(roundDirectory, "timelines");
         Directory.CreateDirectory(candidateDirectory);
@@ -122,7 +122,7 @@ public static class IpaGestureExperiment
         {
             foreach (var variant in variantList)
             {
-                var candidateId = SafeFileName($"{target.Id}-{variant.Id}");
+                var candidateId = StoreFileName.From($"{target.Id}-{variant.Id}");
                 var script = BuildCandidateScript(target, variant);
                 var scriptPath = Path.Combine(candidateDirectory, $"{candidateId}.aqua");
                 File.WriteAllText(scriptPath, script, Encoding.UTF8);
@@ -705,13 +705,6 @@ public static class IpaGestureExperiment
     private static string SafeDslName(string value) =>
         new(value.Select(character => char.IsLetterOrDigit(character) ? character : '_').ToArray());
 
-    private static string SafeFileName(string value)
-    {
-        var invalid = Path.GetInvalidFileNameChars().ToHashSet();
-        var safe = new string(value.Select(character => invalid.Contains(character) || char.IsWhiteSpace(character) ? '-' : character).ToArray());
-        return safe.Length == 0 ? "candidate" : safe;
-    }
-
     private static string Format(float value) =>
         value.ToString("0.######", CultureInfo.InvariantCulture);
 
diff --git a/tests/AquaSynth.Dsl.Tests/StoreFileNameTests.cs b/tests/AquaSynth.Dsl.Tests/StoreFileNameTests.cs
index d8012ae..2f82405 100644
--- a/tests/AquaSynth.Dsl.Tests/StoreFileNameTests.cs
+++ b/tests/AquaSynth.Dsl.Tests/StoreFileNameTests.cs
@@ -113,5 +113,20 @@ public sealed class StoreFileNameTests
         }
     }
 
+    [Fact]
+    public void IpaRoundCandidatesWithCollidingSanitisedIdsKeepDistinctFilesAndStayInRoot()
+    {
+        var root = Path.Combine(Path.GetTempPath(), $"aquasynth-ipa-sfn-{Guid.NewGuid():N}");
+        var result = IpaGestureExperiment.WriteRound(
+            root,
+            "round-sfn",
+            [new IpaGestureExperimentTarget("a/b", "p", "voiceless_bilabial_plosive", .1f), new IpaGestureExperimentTarget("a-b", "m", "voiced_bilabial_nasal", .1f)],
+            [new IpaGestureExperimentVariant("base")]);
+
+        Assert.Equal(2, result.Candidates.Select(c => c.Id).Distinct(StringComparer.OrdinalIgnoreCase).Count());
+        Assert.All(result.Candidates, c => Assert.StartsWith(Path.GetFullPath(root), Path.GetFullPath(c.ScriptPath)));
+        Assert.Throws<ArgumentException>(() => IpaGestureExperiment.WriteRound(root, "..", [new IpaGestureExperimentTarget("a", "p", "voiceless_bilabial_plosive")], [new IpaGestureExperimentVariant("base")]));
+    }
+
     private static string UriPath(string uri) => new Uri(uri).LocalPath;
 }