diff --git a/build.zig b/build.zig
index 06acd0fa3..9f6d06a5d 100644
--- a/build.zig
+++ b/build.zig
@@ -6,10 +6,10 @@ const zls_version = std.SemanticVersion.parse(@import("build.zig.zon").version)
 const minimum_build_zig_version = @import("build.zig.zon").minimum_zig_version;
 
 /// Specify the minimum Zig version that is usable with ZLS:
-/// std.Threaded: replace more kernel32 functions with ntdll
+/// rework fuzz testing to be smith based
 ///
 /// A breaking change to the Zig Build System should be handled by updating ZLS's build runner (see src\build_runner)
-const minimum_runtime_zig_version = "0.16.0-dev.2535+b5bd49460";
+const minimum_runtime_zig_version = "0.16.0-dev.2669+e0173c2ce";
 
 const release_targets = [_]std.Target.Query{
     .{ .cpu_arch = .aarch64, .os_tag = .linux },
diff --git a/build.zig.zon b/build.zig.zon
index 499eda875..14df4464a 100644
--- a/build.zig.zon
+++ b/build.zig.zon
@@ -10,7 +10,7 @@
     // nix flake update --commit-lock-file
     // ```
     // If you do not use Nix, a ZLS maintainer can take care of this.
-    .minimum_zig_version = "0.16.0-dev.2535+b5bd49460",
+    .minimum_zig_version = "0.16.0-dev.2676+4e2cec265",
     // If you do not use Nix, a ZLS maintainer can take care of this.
     // Whenever the dependencies are updated, run the following command:
     // ```bash
diff --git a/flake.lock b/flake.lock
index 3166bdcfb..e1041e2fe 100644
--- a/flake.lock
+++ b/flake.lock
@@ -16,31 +16,13 @@
         "type": "github"
       }
     },
-    "flake-utils": {
-      "inputs": {
-        "systems": "systems"
-      },
-      "locked": {
-        "lastModified": 1705309234,
-        "narHash": "sha256-uNRRNRKmJyCRC/8y1RqBkqWBLM034y4qN7EprSdmgyA=",
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "rev": "1ef2e671c3b0c19053962c07dbda38332dcebf26",
-        "type": "github"
-      },
-      "original": {
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "type": "github"
-      }
-    },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1770464364,
-        "narHash": "sha256-z5NJPSBwsLf/OfD8WTmh79tlSU8XgIbwmk6qB1/TFzY=",
+        "lastModified": 1772047000,
+        "narHash": "sha256-7DaQVv4R97cii/Qdfy4tmDZMB2xxtyIvNGSwXBBhSmo=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "23d72dabcb3b12469f57b37170fcbc1789bd7457",
+        "rev": "1267bb4920d0fc06ea916734c11b0bf004bbe17e",
         "type": "github"
       },
       "original": {
@@ -57,6 +39,7 @@
       }
     },
     "systems": {
+      "flake": false,
       "locked": {
         "lastModified": 1681028828,
         "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
@@ -74,17 +57,17 @@
     "zig-overlay": {
       "inputs": {
         "flake-compat": "flake-compat",
-        "flake-utils": "flake-utils",
         "nixpkgs": [
           "nixpkgs"
-        ]
+        ],
+        "systems": "systems"
       },
       "locked": {
-        "lastModified": 1770598090,
-        "narHash": "sha256-k+82IDgTd9o5sxHIqGlvfwseKln3Ejx1edGtDltuPXo=",
+        "lastModified": 1772280928,
+        "narHash": "sha256-3Anj6gxEr94r2BTPa0+73PADJCRUmRdntIUhyfY7Zzo=",
         "owner": "mitchellh",
         "repo": "zig-overlay",
-        "rev": "142495696982c88edddc8e17e4da90d8164acadf",
+        "rev": "e0f2810732c4205e929dc00c63ced0145240ddb8",
         "type": "github"
       },
       "original": {
diff --git a/src/build_runner/build_runner.zig b/src/build_runner/build_runner.zig
index 38874a402..3e0183442 100644
--- a/src/build_runner/build_runner.zig
+++ b/src/build_runner/build_runner.zig
@@ -58,13 +58,9 @@ pub fn main(init: process.Init.Minimal) !void {
     const io = threaded.ioBasic();
 
     // ...but we'll back our arena by `std.heap.page_allocator` for efficiency.
-    var single_threaded_arena: std.heap.ArenaAllocator = .init(std.heap.page_allocator);
-    defer single_threaded_arena.deinit();
-    var thread_safe_arena: std.heap.ThreadSafeAllocator = .{
-        .child_allocator = single_threaded_arena.allocator(),
-        .io = io,
-    };
-    const arena = thread_safe_arena.allocator();
+    var arena_instance: std.heap.ArenaAllocator = .init(std.heap.page_allocator);
+    defer arena_instance.deinit();
+    const arena = arena_instance.allocator();
 
     const args = try init.args.toSlice(arena);
 
@@ -106,7 +102,7 @@ pub fn main(init: process.Init.Minimal) !void {
             .io = io,
             .gpa = gpa,
             .manifest_dir = try local_cache_directory.handle.createDirPathOpen(io, "h", .{}),
-            .cwd = try process.currentPathAlloc(io, single_threaded_arena.allocator()),
+            .cwd = try process.currentPathAlloc(io, arena),
         },
         .zig_exe = zig_exe,
         .environ_map = try init.environ.createMap(arena),
@@ -259,8 +255,10 @@ pub fn main(init: process.Init.Minimal) !void {
                 fatal("argument '{s}' is not available", .{arg});
             } else if (mem.eql(u8, arg, "--debug-pkg-config")) {
                 builder.debug_pkg_config = true;
-            } else if (mem.eql(u8, arg, "--debug-rt")) {
-                graph.debug_compiler_runtime_libs = true;
+            } else if (mem.cutPrefix(u8, arg, "--debug-rt=")) |rest| {
+                graph.debug_compiler_runtime_libs =
+                    std.meta.stringToEnum(std.builtin.OptimizeMode, rest) orelse
+                    fatal("unrecognized optimization mode: '{s}'", .{rest});
             } else if (mem.eql(u8, arg, "--debug-compile-errors")) {
                 builder.debug_compile_errors = true;
             } else if (mem.eql(u8, arg, "--debug-incremental")) {