fix: resolve executable path via _NSGetExecutablePath, not argv[0]

Bare-name PATH invocation (e.g. `afm` from any shell) sets
CommandLine.arguments[0] to "afm", which URL(fileURLWithPath:) treats
as relative to the CWD. The metallib search and webui search both
walked the wrong base directory, so Homebrew installs failed with
"MLX metallib not found" whenever invoked without a full path.

Switch both lookups to _NSGetExecutablePath, which goes through the
Mach-O loader and returns the true absolute path regardless of how
the binary was invoked. Bundle.main.executableURL and argv[0] remain
as fallbacks.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: scouzi1966

Sources/MacLocalAPI/Server.swift

@@ -1,6 +1,7 @@
 import Vapor
 import Foundation
 import Compression
+import Darwin
 #if canImport(AppKit)
 import AppKit
 #endif
@@ -916,13 +917,24 @@ class Server {
         let fileManager = FileManager.default
         let cwd = fileManager.currentDirectoryPath
 
-        // Get the executable's absolute directory
-        let executablePath = CommandLine.arguments[0]
+        // Get the executable's absolute directory. argv[0] is unreliable when invoked
+        // via PATH (it is just "afm"), so go through the Mach-O loader.
+        var size: UInt32 = 0
+        _ = _NSGetExecutablePath(nil, &size)
         let executableURL: URL
-        if executablePath.hasPrefix("/") {
-            executableURL = URL(fileURLWithPath: executablePath)
+        if size > 0 {
+            var buffer = [CChar](repeating: 0, count: Int(size))
+            if _NSGetExecutablePath(&buffer, &size) == 0 {
+                executableURL = URL(fileURLWithPath: String(cString: buffer)).resolvingSymlinksInPath()
+            } else if let bundleExec = Bundle.main.executableURL {
+                executableURL = bundleExec.resolvingSymlinksInPath()
+            } else {
+                executableURL = URL(fileURLWithPath: cwd).appendingPathComponent(CommandLine.arguments[0])
+            }
+        } else if let bundleExec = Bundle.main.executableURL {
+            executableURL = bundleExec.resolvingSymlinksInPath()
         } else {
-            executableURL = URL(fileURLWithPath: cwd).appendingPathComponent(executablePath)
+            executableURL = URL(fileURLWithPath: cwd).appendingPathComponent(CommandLine.arguments[0])
         }
         let executableDir = executableURL.deletingLastPathComponent().standardized.path
 

Sources/MacLocalAPI/Utils/MLXMetalLibrary.swift

@@ -1,10 +1,36 @@
 import Foundation
 import ArgumentParser
+import Darwin
 
 enum MLXMetalLibrary {
     private static let lock = NSLock()
     private static var initialized = false
 
+    /// Resolve the absolute path to this binary.
+    ///
+    /// `CommandLine.arguments[0]` is unreliable: when invoked via PATH it is just the
+    /// basename ("afm"), so `URL(fileURLWithPath:)` resolves it relative to the current
+    /// working directory instead of the actual binary location. Use `_NSGetExecutablePath`
+    /// (which goes through the Mach-O loader) and fall back to `Bundle.main.executableURL`
+    /// or argv[0] only if that fails.
+    private static func resolveExecutableURL() -> URL {
+        var size: UInt32 = 0
+        _ = _NSGetExecutablePath(nil, &size)
+        if size > 0 {
+            var buffer = [CChar](repeating: 0, count: Int(size))
+            if _NSGetExecutablePath(&buffer, &size) == 0 {
+                let path = String(cString: buffer)
+                if !path.isEmpty {
+                    return URL(fileURLWithPath: path).resolvingSymlinksInPath()
+                }
+            }
+        }
+        if let bundleExec = Bundle.main.executableURL {
+            return bundleExec.resolvingSymlinksInPath()
+        }
+        return URL(fileURLWithPath: CommandLine.arguments[0]).resolvingSymlinksInPath()
+    }
+
     /// Find the metallib without using Bundle.module (which fatalError's when relocated).
     ///
     /// Search order:
@@ -14,7 +40,7 @@ enum MLXMetalLibrary {
     /// 4. SPM Bundle.module (only if the bundle actually exists — never fatalError)
     private static func resolveMetallib() -> URL? {
         let fileManager = FileManager.default
-        let executableURL = URL(fileURLWithPath: CommandLine.arguments[0]).resolvingSymlinksInPath()
+        let executableURL = resolveExecutableURL()
         let executableDir = executableURL.deletingLastPathComponent()
 
         // 1. Explicit env var override