Gracefully exit when pointed at a model asset instead of a model bundle directory

swift/Sources/CoreAIShared/Bundle/ModelBundle.swift

@@ -82,9 +82,14 @@ public struct ModelBundle: Sendable {
         case kindMismatch(expected: BundleKind, got: BundleKind)
         case missingField(String)
         case missingAsset(key: String, path: URL)
+        case pointedAtModelAsset(URL)
 
         public var description: String {
             switch self {
+            case .pointedAtModelAsset(let url):
+                return "'\(url.lastPathComponent)' is a model asset, not a model bundle "
+                    + "directory. A model bundle directory contains metadata, a tokenizer, "
+                    + "and a model asset."
             case .missingMetadata(let url):
                 return "metadata.json not found at \(url.path)"
             case .malformedMetadata(let url, let err):
@@ -114,6 +119,16 @@ public struct ModelBundle: Sendable {
     }
 
     public init(at url: URL) throws {
+        // A model bundle is a *directory* (metadata.json + assets + tokenizer).
+        // If the caller points us directly at a `.aimodel`/`.aimodelc` asset,
+        // fail with actionable guidance. This must run before any filesystem
+        // read: a compiled `.aimodelc` is itself a directory holding its own
+        // unrelated metadata.json, which would otherwise parse as a bogus 0.1
+        // bundle and surface a misleading "unsupported metadata_version" error.
+        let ext = url.pathExtension.lowercased()
+        if ext == "aimodel" || ext == "aimodelc" {
+            throw BundleError.pointedAtModelAsset(url)
+        }
         let metadataURL = url.appending(path: "metadata.json")
         guard FileManager.default.fileExists(atPath: metadataURL.path) else {
             throw BundleError.missingMetadata(metadataURL)

swift/Sources/Tools/benchmark/BenchmarkMain.swift

@@ -22,7 +22,7 @@ struct LLMBenchmark: AsyncParsableCommand {
         abstract: "LLM inference benchmark for CoreAI models"
     )
 
-    @Option(name: .customLong("model"), help: "Path to model bundle directory")
+    @Option(name: .customLong("model"), help: "Path to a model bundle directory")
     var model: String
 
     @Option(name: [.customShort("p"), .customLong("prompt-tokens")], help: "Length of prompt")

swift/Tests/CoreAISharedTests/ModelBundleTests.swift

@@ -78,4 +78,40 @@ struct ModelBundleTests {
             _ = try ModelBundle(at: dir)
         }
     }
+
+    @Test("Pointing at a .aimodelc asset throws pointedAtModelAsset, not a parse error")
+    func pointedAtCompiledAssetThrows() throws {
+        // A compiled `.aimodelc` is a directory with its own unrelated
+        // metadata.json. Pointing the tool at it must fail fast with guidance,
+        // not parse that inner metadata as a bogus 0.1 bundle.
+        let bundleDir = FileManager.default.temporaryDirectory.appending(
+            path: "ModelBundleTests-\(UUID().uuidString)"
+        )
+        let asset = bundleDir.appending(path: "model.aimodelc")
+        try FileManager.default.createDirectory(at: asset, withIntermediateDirectories: true)
+        try """
+        { "producer": "coreai-build", "assetVersion": "2.0" }
+        """.write(
+            to: asset.appending(path: "metadata.json"), atomically: true, encoding: .utf8)
+
+        let error = #expect(throws: ModelBundle.BundleError.self) {
+            _ = try ModelBundle(at: asset)
+        }
+        guard case .pointedAtModelAsset = error else {
+            Issue.record("expected pointedAtModelAsset, got \(String(describing: error))")
+            return
+        }
+        #expect(String(describing: error).contains("model.aimodelc"))
+    }
+
+    @Test("Pointing at a .aimodel asset throws pointedAtModelAsset")
+    func pointedAtUncompiledAssetThrows() throws {
+        let error = #expect(throws: ModelBundle.BundleError.self) {
+            _ = try ModelBundle(from: "/some/where/model.aimodel")
+        }
+        guard case .pointedAtModelAsset = error else {
+            Issue.record("expected pointedAtModelAsset, got \(String(describing: error))")
+            return
+        }
+    }
 }