fix(asset-gen): security hardening + provider correctness + local image_path

Security review + code review of the asset-gen feature surfaced concrete issues;
this fixes them and adds regression tests (request-shaping layer, FakeHttpTransport).

Security
- SafeZipExtractor enforces an extension allowlist; ModelImportPipeline passes an
  inert model/texture allowlist so a provider archive can't drop a .cs/.dll under
  Assets/ and have the Editor compile/load it (code execution on import).
- AssetGenJobManager refuses non-http(s) download URLs before fetching
  (file:// SSRF / local-file read into the project).

Provider correctness
- Meshy image->3D polls /openapi/v1/image-to-3d/{id} (was the v2 text URL).
- Meshy text->3D honors texture=true via the preview->refine two-phase flow.
- OpenRouter image->image attaches the reference image (content image_url part).
- fal image->image uses the /edit endpoint + image_urls array; width/height
  forwarded as image_size.
- Sketchfab search forwards categories/count/cursor/downloadable; preview doc
  corrected (returns metadata, not a base64 thumbnail).
- Job import calls AssetDatabase.Refresh() before importing a freshly written file.

Local image input (image_path)
- New LocalImage helper; image_path is read and sent inline as a base64 data URI
  for Meshy / fal / OpenRouter. Tripo rejects local images with a clear error
  (needs a hosted image_url; its upload flow is not wired).

Cleanup (no behavior change)
- Shared AssetGenPaths + ProviderHttp helpers, HttpResult.Ok, MissingKeyMessage,
  cached glTFast probe, dead-field / per-frame-alloc removal, CLI _emit.

Docs: README + manual-verification updated (image_path support; transparency is
import-flag-only; width/height fal-only).

Verified: package compiles clean; Python 1306 passed / 3 skipped. Meshy refine,
fal /edit, and image_path data-URI paths are unit-tested at the request layer
only -- live smoke per provider (real keys) still pending.

Claude-Session: https://claude.ai/code/session_015DAUrMR5UaSEzEn2wNPrEP

Author: Scriptwonder

MCPForUnity/Editor/Helpers/AssetGenPaths.cs

@@ -0,0 +1,31 @@
+using System.IO;
+using UnityEngine;
+
+namespace MCPForUnity.Editor.Helpers
+{
+    /// <summary>
+    /// Project-path conversions shared by the asset-gen import/write code: project-relative
+    /// ("Assets/...") ↔ absolute on-disk paths, with forward-slash normalization for
+    /// cross-platform consistency.
+    /// </summary>
+    public static class AssetGenPaths
+    {
+        /// <summary>Resolve a project-relative ("Assets/...") path to an absolute, forward-slashed path.</summary>
+        public static string ToAbsolute(string projectRelative)
+        {
+            string dataPath = Application.dataPath.Replace('\\', '/');
+            string projectRoot = dataPath.Substring(0, dataPath.Length - "Assets".Length);
+            return Path.Combine(projectRoot, projectRelative).Replace('\\', '/');
+        }
+
+        /// <summary>Convert an absolute (or already-relative) path to a project-relative ("Assets/...") path.</summary>
+        public static string ToProjectRelative(string path)
+        {
+            string p = path.Replace('\\', '/');
+            if (p.StartsWith("Assets")) return p;
+            string dataPath = Application.dataPath.Replace('\\', '/');
+            if (p.StartsWith(dataPath)) return "Assets" + p.Substring(dataPath.Length);
+            return p;
+        }
+    }
+}

MCPForUnity/Editor/Helpers/AssetGenPaths.cs.meta

@@ -58,6 +58,7 @@ public static class AssetGenJobManager
 
         private static readonly Dictionary<string, AssetGenJob> Jobs = new();
         private static readonly Dictionary<string, Runner> Runners = new();
+        private static readonly List<string> _tickIds = new();
         private static bool _ticking;
 
         static AssetGenJobManager()
@@ -221,7 +222,6 @@ private sealed class Runner
             public double NextPollAt;
             public string ProviderJobId;
             public string DownloadUrl;
-            public byte[] InlineData;
             public string LocalPath;
             public Task<string> SubmitTask;
             public Task<ProviderPollResult> PollTask;
@@ -234,7 +234,7 @@ private static bool TryResolveKey(string provider, AssetGenJob job, out string a
             if (!SecureKeyStore.Current.TryGet(provider, out apiKey) || string.IsNullOrEmpty(apiKey))
             {
                 job.State = AssetGenJobState.Failed;
-                job.Error = $"No API key configured for '{provider}'. Add it in the MCP for Unity → Asset Generation tab.";
+                job.Error = AssetGenProviders.MissingKeyMessage(provider);
                 Jobs[job.JobId] = job;
                 Persist(job);
                 return false;
@@ -266,7 +266,11 @@ private static void Tick()
                 _ticking = false;
                 return;
             }
-            foreach (string id in new List<string>(Runners.Keys))
+            // Snapshot keys into a reused buffer so Advance can mutate Runners mid-iteration
+            // without churning the GC on every editor-update frame.
+            _tickIds.Clear();
+            _tickIds.AddRange(Runners.Keys);
+            foreach (string id in _tickIds)
             {
                 if (Runners.TryGetValue(id, out var r)) Advance(r);
             }
@@ -353,6 +357,14 @@ private static void Advance(Runner r)
                         break;
 
                     case RunnerPhase.Download:
+                        // The download URL comes from an untrusted provider response. Only fetch
+                        // http(s) — refuse file://, ftp://, etc. so a malicious response can't read
+                        // a local file into the project or hit an internal host.
+                        if (!IsAllowedDownloadUrl(r.DownloadUrl))
+                        {
+                            Fail(r, "Refusing to fetch a non-http(s) download URL returned by the provider.");
+                            break;
+                        }
                         r.DownloadTask = r.Transport.SendAsync(
                             new HttpRequestSpec { Method = "GET", Url = r.DownloadUrl }, r.Cts.Token);
                         r.Phase = RunnerPhase.AwaitDownload;
@@ -374,6 +386,10 @@ private static void Advance(Runner r)
                         break;
 
                     case RunnerPhase.Import:
+                        // The result file was just written via File.WriteAllBytes (outside the
+                        // AssetDatabase). Refresh so Unity registers it before we import it,
+                        // mirroring ImportModelFile. Skipped under the test import seam.
+                        if (ImportOverrideForTests == null) AssetDatabase.Refresh();
                         AssetGenJob imported = r.ImportFn(r.Job, r.LocalPath);
                         if (imported != null) r.Job = imported;
                         if (r.Job.State != AssetGenJobState.Failed)
@@ -399,7 +415,7 @@ private static string WriteFile(Runner r, byte[] bytes)
             string root = !string.IsNullOrEmpty(r.OutputFolder) ? r.OutputFolder
                                                                 : (AssetGenPrefs.OutputRoot + "/" + r.Subfolder);
             if (!root.Replace('\\', '/').StartsWith("Assets")) root = AssetGenPrefs.OutputRoot + "/" + r.Subfolder;
-            string absRoot = ToAbsolute(root);
+            string absRoot = AssetGenPaths.ToAbsolute(root);
             Directory.CreateDirectory(absRoot);
             string baseName = SanitizeName(r.Name);
             string fileName = baseName + "." + ext;
@@ -417,13 +433,6 @@ private static string NameFrom(string explicitName, string prompt, string jobId)
             return "asset_" + jobId.Substring(0, 8);
         }
 
-        private static string ToAbsolute(string projectRelative)
-        {
-            string dataPath = Application.dataPath;
-            string projectRoot = dataPath.Substring(0, dataPath.Length - "Assets".Length);
-            return Path.Combine(projectRoot, projectRelative);
-        }
-
         private static string SanitizeName(string raw)
         {
             if (string.IsNullOrWhiteSpace(raw)) return "asset";
@@ -494,6 +503,11 @@ private static bool Faulted(Task t, out string error)
         private static bool IsTerminal(AssetGenJobState s)
             => s == AssetGenJobState.Done || s == AssetGenJobState.Failed || s == AssetGenJobState.Canceled;
 
+        /// <summary>Only http(s) download URLs are allowed; provider responses are untrusted.</summary>
+        private static bool IsAllowedDownloadUrl(string url)
+            => Uri.TryCreate(url, UriKind.Absolute, out Uri u)
+               && (u.Scheme == Uri.UriSchemeHttps || u.Scheme == Uri.UriSchemeHttp);
+
         private static double Now() => EditorApplication.timeSinceStartup;
 
         internal static void ResetForTests()

MCPForUnity/Editor/Services/AssetGen/AssetGenJobManager.cs

@@ -12,5 +12,8 @@ public sealed class HttpResult
         public byte[] Body;
         public string Text;
         public bool IsSuccess;
+
+        /// <summary>True when the transport reports success or the status code is 2xx.</summary>
+        public bool Ok => IsSuccess || (Status >= 200 && Status < 300);
     }
 }

MCPForUnity/Editor/Services/AssetGen/Http/HttpResult.cs

@@ -1,8 +1,8 @@
 using System;
 using System.IO;
+using MCPForUnity.Editor.Helpers;
 using MCPForUnity.Editor.Security;
 using UnityEditor;
-using UnityEngine;
 
 namespace MCPForUnity.Editor.Services.AssetGen.Import
 {
@@ -20,7 +20,7 @@ public static AssetGenJob ImportInto(AssetGenJob job, string localFilePath, bool
                 if (string.IsNullOrEmpty(localFilePath))
                     return Fail(job, "No file to import.");
 
-                string rel = ToProjectRelative(localFilePath);
+                string rel = AssetGenPaths.ToProjectRelative(localFilePath);
                 if (string.IsNullOrEmpty(rel) || !rel.Replace('\\', '/').StartsWith("Assets"))
                     return Fail(job, "Generated file is not under the Assets folder.");
 
@@ -54,15 +54,6 @@ public static AssetGenJob ImportInto(AssetGenJob job, string localFilePath, bool
             }
         }
 
-        private static string ToProjectRelative(string path)
-        {
-            string p = path.Replace('\\', '/');
-            if (p.StartsWith("Assets")) return p;
-            string dataPath = Application.dataPath.Replace('\\', '/');
-            if (p.StartsWith(dataPath)) return "Assets" + p.Substring(dataPath.Length);
-            return p;
-        }
-
         private static AssetGenJob Fail(AssetGenJob job, string message)
         {
             job.State = AssetGenJobState.Failed;

MCPForUnity/Editor/Services/AssetGen/Import/ImageImportPipeline.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.IO;
 using MCPForUnity.Editor.Helpers;
 using MCPForUnity.Editor.Security;
@@ -15,6 +16,15 @@ namespace MCPForUnity.Editor.Services.AssetGen.Import
     /// </summary>
     public static class ModelImportPipeline
     {
+        // Inert asset types permitted out of an UNTRUSTED provider archive (Sketchfab et al.).
+        // Anything else — scripts, assemblies, asmdefs — is skipped on extraction so it can never
+        // compile or load inside the Editor. See SafeZipExtractor for the enforcement.
+        private static readonly HashSet<string> ArchiveAllowedExtensions = new(StringComparer.OrdinalIgnoreCase)
+        {
+            ".gltf", ".glb", ".bin", ".fbx", ".obj", ".mtl",
+            ".png", ".jpg", ".jpeg", ".tga", ".bmp", ".tif", ".tiff", ".webp", ".exr", ".hdr", ".ktx2", ".basis",
+        };
+
         public static AssetGenJob ImportInto(AssetGenJob job, string localFilePath)
         {
             if (job == null) return null;
@@ -23,7 +33,7 @@ public static AssetGenJob ImportInto(AssetGenJob job, string localFilePath)
                 if (string.IsNullOrEmpty(localFilePath))
                     return Fail(job, "No file to import.");
 
-                string rel = ToProjectRelative(localFilePath);
+                string rel = AssetGenPaths.ToProjectRelative(localFilePath);
                 if (string.IsNullOrEmpty(rel) || !rel.Replace('\\', '/').StartsWith("Assets"))
                     return Fail(job, "Generated file is not under the Assets folder.");
 
@@ -71,15 +81,17 @@ private static AssetGenJob ImportModelFile(AssetGenJob job, string rel, string e
         /// </summary>
         private static AssetGenJob ImportArchive(AssetGenJob job, string zipRel)
         {
-            string zipAbs = ToAbsolute(zipRel);
+            string zipAbs = AssetGenPaths.ToAbsolute(zipRel);
             if (!File.Exists(zipAbs))
                 return Fail(job, "Downloaded archive was not found on disk.");
 
             string folderRel = zipRel.Substring(0, zipRel.Length - ".zip".Length);
-            string folderAbs = ToAbsolute(folderRel);
+            string folderAbs = AssetGenPaths.ToAbsolute(folderRel);
 
             Directory.CreateDirectory(folderAbs);
-            SafeZipExtractor.ExtractTo(zipAbs, folderAbs);
+            // Provider archives are untrusted: only inert model/texture files are written under
+            // Assets/ — scripts/assemblies are skipped so they can't be compiled on import.
+            SafeZipExtractor.ExtractTo(zipAbs, folderAbs, ArchiveAllowedExtensions);
 
             AssetDatabase.Refresh();
             AssetDatabase.ImportAsset(folderRel, ImportAssetOptions.ImportRecursive | ImportAssetOptions.ForceUpdate);
@@ -126,18 +138,11 @@ private static string FindFirstModel(string folderAbs)
             {
                 string e = Path.GetExtension(abs).ToLowerInvariant();
                 if (e == ".fbx" || e == ".obj")
-                    return ToProjectRelative(abs);
+                    return AssetGenPaths.ToProjectRelative(abs);
                 if (firstGltf == null && (e == ".glb" || e == ".gltf"))
                     firstGltf = abs;
             }
-            return firstGltf == null ? null : ToProjectRelative(firstGltf);
-        }
-
-        private static string ToAbsolute(string projectRelative)
-        {
-            string dataPath = Application.dataPath.Replace('\\', '/');
-            string projectRoot = dataPath.Substring(0, dataPath.Length - "Assets".Length);
-            return Path.Combine(projectRoot, projectRelative).Replace('\\', '/');
+            return firstGltf == null ? null : AssetGenPaths.ToProjectRelative(firstGltf);
         }
 
         private static void ApplyModelImporterSettings(string rel, AssetGenJob job)
@@ -191,24 +196,27 @@ private static float ComputeMaxDimension(string rel)
             catch { return 0f; }
         }
 
-        private static bool IsGltfastAvailable()
+        private static bool? _gltfastAvailable;
+
+        /// <summary>
+        /// True when the glTFast package is present. Cached after the first probe — the result only
+        /// changes on a package install/uninstall, which triggers a domain reload that resets this
+        /// static. Shared with the Asset Gen settings tab so the reflection scan runs at most once.
+        /// </summary>
+        internal static bool IsGltfastAvailable()
         {
-            if (Type.GetType("GLTFast.GltfImport, glTFast") != null) return true;
-            foreach (var asm in AppDomain.CurrentDomain.GetAssemblies())
+            if (_gltfastAvailable.HasValue) return _gltfastAvailable.Value;
+            bool found = Type.GetType("GLTFast.GltfImport, glTFast") != null;
+            if (!found)
             {
-                try { if (asm.GetType("GLTFast.GltfImport") != null) return true; }
-                catch { /* dynamic/!resolvable assembly */ }
+                foreach (var asm in AppDomain.CurrentDomain.GetAssemblies())
+                {
+                    try { if (asm.GetType("GLTFast.GltfImport") != null) { found = true; break; } }
+                    catch { /* dynamic/!resolvable assembly */ }
+                }
             }
-            return false;
-        }
-
-        private static string ToProjectRelative(string path)
-        {
-            string p = path.Replace('\\', '/');
-            if (p.StartsWith("Assets")) return p;
-            string dataPath = Application.dataPath.Replace('\\', '/');
-            if (p.StartsWith(dataPath)) return "Assets" + p.Substring(dataPath.Length);
-            return p;
+            _gltfastAvailable = found;
+            return found;
         }
 
         private static AssetGenJob Fail(AssetGenJob job, string message)

MCPForUnity/Editor/Services/AssetGen/Import/ModelImportPipeline.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.IO;
 using System.IO.Compression;
 
@@ -9,10 +10,15 @@ namespace MCPForUnity.Editor.Services.AssetGen.Import
     /// every entry's resolved target must stay inside <c>destDir</c>. Directory entries are
     /// created; file entries are written by copying the entry stream (no reliance on the
     /// ZipFileExtensions helper). Used to unpack marketplace model archives (e.g. Sketchfab).
+    ///
+    /// When <paramref name="allowedExtensions"/> is supplied, file entries whose extension is not
+    /// on the allowlist are SKIPPED (not written). Callers that extract UNTRUSTED archives into the
+    /// Assets tree MUST pass an allowlist of inert asset types so executable content (.cs/.dll/
+    /// .asmdef) can never land under Assets/ and be compiled/loaded by the Editor.
     /// </summary>
     public static class SafeZipExtractor
     {
-        public static void ExtractTo(string zipPath, string destDir)
+        public static void ExtractTo(string zipPath, string destDir, ISet<string> allowedExtensions = null)
         {
             if (string.IsNullOrEmpty(zipPath)) throw new ArgumentException("zipPath required", nameof(zipPath));
             if (string.IsNullOrEmpty(destDir)) throw new ArgumentException("destDir required", nameof(destDir));
@@ -46,6 +52,13 @@ public static void ExtractTo(string zipPath, string destDir)
                         continue;
                     }
 
+                    // Allowlist gate: skip anything that isn't an inert asset type the caller permits.
+                    if (allowedExtensions != null && allowedExtensions.Count > 0
+                        && !allowedExtensions.Contains(Path.GetExtension(entry.Name).ToLowerInvariant()))
+                    {
+                        continue;
+                    }
+
                     string parent = Path.GetDirectoryName(target);
                     if (!string.IsNullOrEmpty(parent)) Directory.CreateDirectory(parent);
 

MCPForUnity/Editor/Services/AssetGen/Import/SafeZipExtractor.cs

@@ -66,5 +66,13 @@ private static bool IsConfigured(string id)
             try { return SecureKeyStore.Current.Has(id); }
             catch { return false; }
         }
+
+        /// <summary>
+        /// Standard "no key" message: points the user at the Asset Generation tab and the env override.
+        /// Shared by the asset-gen tools and the job manager so the wording stays in one place.
+        /// </summary>
+        public static string MissingKeyMessage(string provider)
+            => $"No API key configured for '{provider}'. Add it in the MCP for Unity → Asset Generation tab " +
+               $"(or set MCPFORUNITY_{(provider ?? string.Empty).ToUpperInvariant()}_API_KEY).";
     }
 }