diff --git a/lib/compiler/resinator/compile.zig b/lib/compiler/resinator/compile.zig
index fbb3797fde..df1bbbcddf 100644
--- a/lib/compiler/resinator/compile.zig
+++ b/lib/compiler/resinator/compile.zig
@@ -1,6 +1,12 @@
-const std = @import("std");
 const builtin = @import("builtin");
+const native_endian = builtin.cpu.arch.endian();
+
+const std = @import("std");
+const Io = std.Io;
 const Allocator = std.mem.Allocator;
+const WORD = std.os.windows.WORD;
+const DWORD = std.os.windows.DWORD;
+
 const Node = @import("ast.zig").Node;
 const lex = @import("lex.zig");
 const Parser = @import("parse.zig").Parser;
@@ -17,8 +23,6 @@ const res = @import("res.zig");
 const ico = @import("ico.zig");
 const ani = @import("ani.zig");
 const bmp = @import("bmp.zig");
-const WORD = std.os.windows.WORD;
-const DWORD = std.os.windows.DWORD;
 const utils = @import("utils.zig");
 const NameOrOrdinal = res.NameOrOrdinal;
 const SupportedCodePage = @import("code_pages.zig").SupportedCodePage;
@@ -28,7 +32,6 @@ const windows1252 = @import("windows1252.zig");
 const lang = @import("lang.zig");
 const code_pages = @import("code_pages.zig");
 const errors = @import("errors.zig");
-const native_endian = builtin.cpu.arch.endian();
 
 pub const CompileOptions = struct {
     cwd: std.fs.Dir,
@@ -77,7 +80,7 @@ pub const Dependencies = struct {
     }
 };
 
-pub fn compile(allocator: Allocator, source: []const u8, writer: *std.Io.Writer, options: CompileOptions) !void {
+pub fn compile(allocator: Allocator, io: Io, source: []const u8, writer: *std.Io.Writer, options: CompileOptions) !void {
     var lexer = lex.Lexer.init(source, .{
         .default_code_page = options.default_code_page,
         .source_mappings = options.source_mappings,
@@ -166,10 +169,11 @@ pub fn compile(allocator: Allocator, source: []const u8, writer: *std.Io.Writer,
     defer arena_allocator.deinit();
     const arena = arena_allocator.allocator();
 
-    var compiler = Compiler{
+    var compiler: Compiler = .{
         .source = source,
         .arena = arena,
         .allocator = allocator,
+        .io = io,
         .cwd = options.cwd,
         .diagnostics = options.diagnostics,
         .dependencies = options.dependencies,
@@ -191,6 +195,7 @@ pub const Compiler = struct {
     source: []const u8,
     arena: Allocator,
     allocator: Allocator,
+    io: Io,
     cwd: std.fs.Dir,
     state: State = .{},
     diagnostics: *Diagnostics,
@@ -409,7 +414,7 @@ pub const Compiler = struct {
             }
         }
 
-        var first_error: ?std.fs.File.OpenError = null;
+        var first_error: ?(std.fs.File.OpenError || std.fs.File.StatError) = null;
         for (self.search_dirs) |search_dir| {
             if (utils.openFileNotDir(search_dir.dir, path, .{})) |file| {
                 errdefer file.close();
@@ -496,6 +501,8 @@ pub const Compiler = struct {
     }
 
     pub fn writeResourceExternal(self: *Compiler, node: *Node.ResourceExternal, writer: *std.Io.Writer) !void {
+        const io = self.io;
+
         // Init header with data size zero for now, will need to fill it in later
         var header = try self.resourceHeader(node.id, node.type, .{});
         defer header.deinit(self.allocator);
@@ -582,7 +589,7 @@ pub const Compiler = struct {
         };
         defer file_handle.close();
         var file_buffer: [2048]u8 = undefined;
-        var file_reader = file_handle.reader(&file_buffer);
+        var file_reader = file_handle.reader(io, &file_buffer);
 
         if (maybe_predefined_type) |predefined_type| {
             switch (predefined_type) {
diff --git a/lib/compiler/resinator/cvtres.zig b/lib/compiler/resinator/cvtres.zig
index 50d2c6e96a..26b6620af2 100644
--- a/lib/compiler/resinator/cvtres.zig
+++ b/lib/compiler/resinator/cvtres.zig
@@ -1,5 +1,7 @@
 const std = @import("std");
+const Io = std.Io;
 const Allocator = std.mem.Allocator;
+
 const res = @import("res.zig");
 const NameOrOrdinal = res.NameOrOrdinal;
 const MemoryFlags = res.MemoryFlags;
@@ -169,8 +171,7 @@ pub fn parseNameOrOrdinal(allocator: Allocator, reader: *std.Io.Reader) !NameOrO
 
 pub const CoffOptions = struct {
     target: std.coff.IMAGE.FILE.MACHINE = .AMD64,
-    /// If true, zeroes will be written to all timestamp fields
-    reproducible: bool = true,
+    timestamp: i64 = 0,
     /// If true, the MEM_WRITE flag will not be set in the .rsrc section header
     read_only: bool = false,
     /// If non-null, a symbol with this name and storage class EXTERNAL will be added to the symbol table.
@@ -188,7 +189,13 @@ pub const Diagnostics = union {
     overflow_resource: usize,
 };
 
-pub fn writeCoff(allocator: Allocator, writer: *std.Io.Writer, resources: []const Resource, options: CoffOptions, diagnostics: ?*Diagnostics) !void {
+pub fn writeCoff(
+    allocator: Allocator,
+    writer: *std.Io.Writer,
+    resources: []const Resource,
+    options: CoffOptions,
+    diagnostics: ?*Diagnostics,
+) !void {
     var resource_tree = ResourceTree.init(allocator, options);
     defer resource_tree.deinit();
 
@@ -215,7 +222,7 @@ pub fn writeCoff(allocator: Allocator, writer: *std.Io.Writer, resources: []cons
     const pointer_to_rsrc02_data = pointer_to_relocations + relocations_len;
     const pointer_to_symbol_table = pointer_to_rsrc02_data + lengths.rsrc02;
 
-    const timestamp: i64 = if (options.reproducible) 0 else std.time.timestamp();
+    const timestamp: i64 = options.timestamp;
     const size_of_optional_header = 0;
     const machine_type: std.coff.IMAGE.FILE.MACHINE = options.target;
     const flags = std.coff.Header.Flags{
diff --git a/lib/compiler/resinator/errors.zig b/lib/compiler/resinator/errors.zig
index 1d9cbf4c5b..aad74a3ca3 100644
--- a/lib/compiler/resinator/errors.zig
+++ b/lib/compiler/resinator/errors.zig
@@ -1,5 +1,11 @@
+const builtin = @import("builtin");
+const native_endian = builtin.cpu.arch.endian();
+
 const std = @import("std");
+const Io = std.Io;
 const assert = std.debug.assert;
+const Allocator = std.mem.Allocator;
+
 const Token = @import("lex.zig").Token;
 const SourceMappings = @import("source_mapping.zig").SourceMappings;
 const utils = @import("utils.zig");
@@ -11,19 +17,19 @@ const parse = @import("parse.zig");
 const lang = @import("lang.zig");
 const code_pages = @import("code_pages.zig");
 const SupportedCodePage = code_pages.SupportedCodePage;
-const builtin = @import("builtin");
-const native_endian = builtin.cpu.arch.endian();
 
 pub const Diagnostics = struct {
     errors: std.ArrayList(ErrorDetails) = .empty,
     /// Append-only, cannot handle removing strings.
     /// Expects to own all strings within the list.
     strings: std.ArrayList([]const u8) = .empty,
-    allocator: std.mem.Allocator,
+    allocator: Allocator,
+    io: Io,
 
-    pub fn init(allocator: std.mem.Allocator) Diagnostics {
+    pub fn init(allocator: Allocator, io: Io) Diagnostics {
         return .{
             .allocator = allocator,
+            .io = io,
         };
     }
 
@@ -62,10 +68,11 @@ pub const Diagnostics = struct {
     }
 
     pub fn renderToStdErr(self: *Diagnostics, cwd: std.fs.Dir, source: []const u8, tty_config: std.Io.tty.Config, source_mappings: ?SourceMappings) void {
+        const io = self.io;
         const stderr = std.debug.lockStderrWriter(&.{});
         defer std.debug.unlockStderrWriter();
         for (self.errors.items) |err_details| {
-            renderErrorMessage(stderr, tty_config, cwd, err_details, source, self.strings.items, source_mappings) catch return;
+            renderErrorMessage(io, stderr, tty_config, cwd, err_details, source, self.strings.items, source_mappings) catch return;
         }
     }
 
@@ -167,9 +174,9 @@ pub const ErrorDetails = struct {
         filename_string_index: FilenameStringIndex,
 
         pub const FilenameStringIndex = std.meta.Int(.unsigned, 32 - @bitSizeOf(FileOpenErrorEnum));
-        pub const FileOpenErrorEnum = std.meta.FieldEnum(std.fs.File.OpenError);
+        pub const FileOpenErrorEnum = std.meta.FieldEnum(std.fs.File.OpenError || std.fs.File.StatError);
 
-        pub fn enumFromError(err: std.fs.File.OpenError) FileOpenErrorEnum {
+        pub fn enumFromError(err: (std.fs.File.OpenError || std.fs.File.StatError)) FileOpenErrorEnum {
             return switch (err) {
                 inline else => |e| @field(ErrorDetails.FileOpenError.FileOpenErrorEnum, @errorName(e)),
             };
@@ -894,7 +901,16 @@ fn cellCount(code_page: SupportedCodePage, source: []const u8, start_index: usiz
 
 const truncated_str = "<...truncated...>";
 
-pub fn renderErrorMessage(writer: *std.Io.Writer, tty_config: std.Io.tty.Config, cwd: std.fs.Dir, err_details: ErrorDetails, source: []const u8, strings: []const []const u8, source_mappings: ?SourceMappings) !void {
+pub fn renderErrorMessage(
+    io: Io,
+    writer: *std.Io.Writer,
+    tty_config: std.Io.tty.Config,
+    cwd: std.fs.Dir,
+    err_details: ErrorDetails,
+    source: []const u8,
+    strings: []const []const u8,
+    source_mappings: ?SourceMappings,
+) !void {
     if (err_details.type == .hint) return;
 
     const source_line_start = err_details.token.getLineStartForErrorDisplay(source);
@@ -989,6 +1005,7 @@ pub fn renderErrorMessage(writer: *std.Io.Writer, tty_config: std.Io.tty.Config,
         var initial_lines_err: ?anyerror = null;
         var file_reader_buf: [max_source_line_bytes * 2]u8 = undefined;
         var corresponding_lines: ?CorrespondingLines = CorrespondingLines.init(
+            io,
             cwd,
             err_details,
             source_line_for_display.line,
@@ -1084,6 +1101,7 @@ const CorrespondingLines = struct {
     code_page: SupportedCodePage,
 
     pub fn init(
+        io: Io,
         cwd: std.fs.Dir,
         err_details: ErrorDetails,
         line_for_comparison: []const u8,
@@ -1108,7 +1126,7 @@ const CorrespondingLines = struct {
             .code_page = err_details.code_page,
             .file_reader = undefined,
         };
-        corresponding_lines.file_reader = corresponding_lines.file.reader(file_reader_buf);
+        corresponding_lines.file_reader = corresponding_lines.file.reader(io, file_reader_buf);
         errdefer corresponding_lines.deinit();
 
         try corresponding_lines.writeLineFromStreamVerbatim(
diff --git a/lib/compiler/resinator/main.zig b/lib/compiler/resinator/main.zig
index ce8532ae9f..108b914377 100644
--- a/lib/compiler/resinator/main.zig
+++ b/lib/compiler/resinator/main.zig
@@ -1,5 +1,9 @@
-const std = @import("std");
 const builtin = @import("builtin");
+
+const std = @import("std");
+const Io = std.Io;
+const Allocator = std.mem.Allocator;
+
 const removeComments = @import("comments.zig").removeComments;
 const parseAndRemoveLineCommands = @import("source_mapping.zig").parseAndRemoveLineCommands;
 const compile = @import("compile.zig").compile;
@@ -16,19 +20,18 @@ const aro = @import("aro");
 const compiler_util = @import("../util.zig");
 
 pub fn main() !void {
-    var gpa: std.heap.GeneralPurposeAllocator(.{}) = .init;
-    defer std.debug.assert(gpa.deinit() == .ok);
-    const allocator = gpa.allocator();
+    var debug_allocator: std.heap.DebugAllocator(.{}) = .init;
+    defer std.debug.assert(debug_allocator.deinit() == .ok);
+    const gpa = debug_allocator.allocator();
 
-    var arena_state = std.heap.ArenaAllocator.init(allocator);
+    var arena_state = std.heap.ArenaAllocator.init(gpa);
     defer arena_state.deinit();
     const arena = arena_state.allocator();
 
     const stderr = std.fs.File.stderr();
     const stderr_config = std.Io.tty.detectConfig(stderr);
 
-    const args = try std.process.argsAlloc(allocator);
-    defer std.process.argsFree(allocator, args);
+    const args = try std.process.argsAlloc(arena);
 
     if (args.len < 2) {
         try renderErrorMessage(std.debug.lockStderrWriter(&.{}), stderr_config, .err, "expected zig lib dir as first argument", .{});
@@ -59,11 +62,11 @@ pub fn main() !void {
     };
 
     var options = options: {
-        var cli_diagnostics = cli.Diagnostics.init(allocator);
+        var cli_diagnostics = cli.Diagnostics.init(gpa);
         defer cli_diagnostics.deinit();
-        var options = cli.parse(allocator, cli_args, &cli_diagnostics) catch |err| switch (err) {
+        var options = cli.parse(gpa, cli_args, &cli_diagnostics) catch |err| switch (err) {
             error.ParseError => {
-                try error_handler.emitCliDiagnostics(allocator, cli_args, &cli_diagnostics);
+                try error_handler.emitCliDiagnostics(gpa, cli_args, &cli_diagnostics);
                 std.process.exit(1);
             },
             else => |e| return e,
@@ -84,6 +87,10 @@ pub fn main() !void {
     };
     defer options.deinit();
 
+    var threaded: std.Io.Threaded = .init(gpa);
+    defer threaded.deinit();
+    const io = threaded.io();
+
     if (options.print_help_and_exit) {
         try cli.writeUsage(stdout, "zig rc");
         try stdout.flush();
@@ -99,12 +106,13 @@ pub fn main() !void {
         try stdout.flush();
     }
 
-    var dependencies = Dependencies.init(allocator);
+    var dependencies = Dependencies.init(gpa);
     defer dependencies.deinit();
     const maybe_dependencies: ?*Dependencies = if (options.depfile_path != null) &dependencies else null;
 
     var include_paths = LazyIncludePaths{
         .arena = arena,
+        .io = io,
         .auto_includes_option = options.auto_includes,
         .zig_lib_dir = zig_lib_dir,
         .target_machine_type = options.coff_options.target,
@@ -112,12 +120,12 @@ pub fn main() !void {
 
     const full_input = full_input: {
         if (options.input_format == .rc and options.preprocess != .no) {
-            var preprocessed_buf: std.Io.Writer.Allocating = .init(allocator);
+            var preprocessed_buf: std.Io.Writer.Allocating = .init(gpa);
             errdefer preprocessed_buf.deinit();
 
             // We're going to throw away everything except the final preprocessed output anyway,
             // so we can use a scoped arena for everything else.
-            var aro_arena_state = std.heap.ArenaAllocator.init(allocator);
+            var aro_arena_state = std.heap.ArenaAllocator.init(gpa);
             defer aro_arena_state.deinit();
             const aro_arena = aro_arena_state.allocator();
 
@@ -129,12 +137,12 @@ pub fn main() !void {
                     .color = stderr_config,
                 } } },
                 true => .{ .output = .{ .to_list = .{
-                    .arena = .init(allocator),
+                    .arena = .init(gpa),
                 } } },
             };
             defer diagnostics.deinit();
 
-            var comp = aro.Compilation.init(aro_arena, aro_arena, &diagnostics, std.fs.cwd());
+            var comp = aro.Compilation.init(aro_arena, aro_arena, io, &diagnostics, std.fs.cwd());
             defer comp.deinit();
 
             var argv: std.ArrayList([]const u8) = .empty;
@@ -159,20 +167,20 @@ pub fn main() !void {
 
             preprocess.preprocess(&comp, &preprocessed_buf.writer, argv.items, maybe_dependencies) catch |err| switch (err) {
                 error.GeneratedSourceError => {
-                    try error_handler.emitAroDiagnostics(allocator, "failed during preprocessor setup (this is always a bug)", &comp);
+                    try error_handler.emitAroDiagnostics(gpa, "failed during preprocessor setup (this is always a bug)", &comp);
                     std.process.exit(1);
                 },
                 // ArgError can occur if e.g. the .rc file is not found
                 error.ArgError, error.PreprocessError => {
-                    try error_handler.emitAroDiagnostics(allocator, "failed during preprocessing", &comp);
+                    try error_handler.emitAroDiagnostics(gpa, "failed during preprocessing", &comp);
                     std.process.exit(1);
                 },
                 error.FileTooBig => {
-                    try error_handler.emitMessage(allocator, .err, "failed during preprocessing: maximum file size exceeded", .{});
+                    try error_handler.emitMessage(gpa, .err, "failed during preprocessing: maximum file size exceeded", .{});
                     std.process.exit(1);
                 },
                 error.WriteFailed => {
-                    try error_handler.emitMessage(allocator, .err, "failed during preprocessing: error writing the preprocessed output", .{});
+                    try error_handler.emitMessage(gpa, .err, "failed during preprocessing: error writing the preprocessed output", .{});
                     std.process.exit(1);
                 },
                 error.OutOfMemory => |e| return e,
@@ -182,22 +190,22 @@ pub fn main() !void {
         } else {
             switch (options.input_source) {
                 .stdio => |file| {
-                    var file_reader = file.reader(&.{});
-                    break :full_input file_reader.interface.allocRemaining(allocator, .unlimited) catch |err| {
-                        try error_handler.emitMessage(allocator, .err, "unable to read input from stdin: {s}", .{@errorName(err)});
+                    var file_reader = file.reader(io, &.{});
+                    break :full_input file_reader.interface.allocRemaining(gpa, .unlimited) catch |err| {
+                        try error_handler.emitMessage(gpa, .err, "unable to read input from stdin: {s}", .{@errorName(err)});
                         std.process.exit(1);
                     };
                 },
                 .filename => |input_filename| {
-                    break :full_input std.fs.cwd().readFileAlloc(input_filename, allocator, .unlimited) catch |err| {
-                        try error_handler.emitMessage(allocator, .err, "unable to read input file path '{s}': {s}", .{ input_filename, @errorName(err) });
+                    break :full_input std.fs.cwd().readFileAlloc(input_filename, gpa, .unlimited) catch |err| {
+                        try error_handler.emitMessage(gpa, .err, "unable to read input file path '{s}': {s}", .{ input_filename, @errorName(err) });
                         std.process.exit(1);
                     };
                 },
             }
         }
     };
-    defer allocator.free(full_input);
+    defer gpa.free(full_input);
 
     if (options.preprocess == .only) {
         switch (options.output_source) {
@@ -221,55 +229,55 @@ pub fn main() !void {
             }
         else if (options.input_format == .res)
             IoStream.fromIoSource(options.input_source, .input) catch |err| {
-                try error_handler.emitMessage(allocator, .err, "unable to read res file path '{s}': {s}", .{ options.input_source.filename, @errorName(err) });
+                try error_handler.emitMessage(gpa, .err, "unable to read res file path '{s}': {s}", .{ options.input_source.filename, @errorName(err) });
                 std.process.exit(1);
             }
         else
             IoStream.fromIoSource(options.output_source, .output) catch |err| {
-                try error_handler.emitMessage(allocator, .err, "unable to create output file '{s}': {s}", .{ options.output_source.filename, @errorName(err) });
+                try error_handler.emitMessage(gpa, .err, "unable to create output file '{s}': {s}", .{ options.output_source.filename, @errorName(err) });
                 std.process.exit(1);
             };
-        defer res_stream.deinit(allocator);
+        defer res_stream.deinit(gpa);
 
         const res_data = res_data: {
             if (options.input_format != .res) {
                 // Note: We still want to run this when no-preprocess is set because:
                 //   1. We want to print accurate line numbers after removing multiline comments
                 //   2. We want to be able to handle an already-preprocessed input with #line commands in it
-                var mapping_results = parseAndRemoveLineCommands(allocator, full_input, full_input, .{ .initial_filename = options.input_source.filename }) catch |err| switch (err) {
+                var mapping_results = parseAndRemoveLineCommands(gpa, full_input, full_input, .{ .initial_filename = options.input_source.filename }) catch |err| switch (err) {
                     error.InvalidLineCommand => {
                         // TODO: Maybe output the invalid line command
-                        try error_handler.emitMessage(allocator, .err, "invalid line command in the preprocessed source", .{});
+                        try error_handler.emitMessage(gpa, .err, "invalid line command in the preprocessed source", .{});
                         if (options.preprocess == .no) {
-                            try error_handler.emitMessage(allocator, .note, "line commands must be of the format: #line <num> \"<path>\"", .{});
+                            try error_handler.emitMessage(gpa, .note, "line commands must be of the format: #line <num> \"<path>\"", .{});
                         } else {
-                            try error_handler.emitMessage(allocator, .note, "this is likely to be a bug, please report it", .{});
+                            try error_handler.emitMessage(gpa, .note, "this is likely to be a bug, please report it", .{});
                         }
                         std.process.exit(1);
                     },
                     error.LineNumberOverflow => {
                         // TODO: Better error message
-                        try error_handler.emitMessage(allocator, .err, "line number count exceeded maximum of {}", .{std.math.maxInt(usize)});
+                        try error_handler.emitMessage(gpa, .err, "line number count exceeded maximum of {}", .{std.math.maxInt(usize)});
                         std.process.exit(1);
                     },
                     error.OutOfMemory => |e| return e,
                 };
-                defer mapping_results.mappings.deinit(allocator);
+                defer mapping_results.mappings.deinit(gpa);
 
                 const default_code_page = options.default_code_page orelse .windows1252;
                 const has_disjoint_code_page = hasDisjointCodePage(mapping_results.result, &mapping_results.mappings, default_code_page);
 
                 const final_input = try removeComments(mapping_results.result, mapping_results.result, &mapping_results.mappings);
 
-                var diagnostics = Diagnostics.init(allocator);
+                var diagnostics = Diagnostics.init(gpa, io);
                 defer diagnostics.deinit();
 
                 var output_buffer: [4096]u8 = undefined;
-                var res_stream_writer = res_stream.source.writer(allocator, &output_buffer);
+                var res_stream_writer = res_stream.source.writer(gpa, &output_buffer);
                 defer res_stream_writer.deinit(&res_stream.source);
                 const output_buffered_stream = res_stream_writer.interface();
 
-                compile(allocator, final_input, output_buffered_stream, .{
+                compile(gpa, io, final_input, output_buffered_stream, .{
                     .cwd = std.fs.cwd(),
                     .diagnostics = &diagnostics,
                     .source_mappings = &mapping_results.mappings,
@@ -287,7 +295,7 @@ pub fn main() !void {
                     .warn_instead_of_error_on_invalid_code_page = options.warn_instead_of_error_on_invalid_code_page,
                 }) catch |err| switch (err) {
                     error.ParseError, error.CompileError => {
-                        try error_handler.emitDiagnostics(allocator, std.fs.cwd(), final_input, &diagnostics, mapping_results.mappings);
+                        try error_handler.emitDiagnostics(gpa, std.fs.cwd(), final_input, &diagnostics, mapping_results.mappings);
                         // Delete the output file on error
                         res_stream.cleanupAfterError();
                         std.process.exit(1);
@@ -305,7 +313,7 @@ pub fn main() !void {
                 // write the depfile
                 if (options.depfile_path) |depfile_path| {
                     var depfile = std.fs.cwd().createFile(depfile_path, .{}) catch |err| {
-                        try error_handler.emitMessage(allocator, .err, "unable to create depfile '{s}': {s}", .{ depfile_path, @errorName(err) });
+                        try error_handler.emitMessage(gpa, .err, "unable to create depfile '{s}': {s}", .{ depfile_path, @errorName(err) });
                         std.process.exit(1);
                     };
                     defer depfile.close();
@@ -332,41 +340,41 @@ pub fn main() !void {
 
             if (options.output_format != .coff) return;
 
-            break :res_data res_stream.source.readAll(allocator) catch |err| {
-                try error_handler.emitMessage(allocator, .err, "unable to read res from '{s}': {s}", .{ res_stream.name, @errorName(err) });
+            break :res_data res_stream.source.readAll(gpa, io) catch |err| {
+                try error_handler.emitMessage(gpa, .err, "unable to read res from '{s}': {s}", .{ res_stream.name, @errorName(err) });
                 std.process.exit(1);
             };
         };
         // No need to keep the res_data around after parsing the resources from it
-        defer res_data.deinit(allocator);
+        defer res_data.deinit(gpa);
 
         std.debug.assert(options.output_format == .coff);
 
         // TODO: Maybe use a buffered file reader instead of reading file into memory -> fbs
         var res_reader: std.Io.Reader = .fixed(res_data.bytes);
-        break :resources cvtres.parseRes(allocator, &res_reader, .{ .max_size = res_data.bytes.len }) catch |err| {
+        break :resources cvtres.parseRes(gpa, &res_reader, .{ .max_size = res_data.bytes.len }) catch |err| {
             // TODO: Better errors
-            try error_handler.emitMessage(allocator, .err, "unable to parse res from '{s}': {s}", .{ res_stream.name, @errorName(err) });
+            try error_handler.emitMessage(gpa, .err, "unable to parse res from '{s}': {s}", .{ res_stream.name, @errorName(err) });
             std.process.exit(1);
         };
     };
     defer resources.deinit();
 
     var coff_stream = IoStream.fromIoSource(options.output_source, .output) catch |err| {
-        try error_handler.emitMessage(allocator, .err, "unable to create output file '{s}': {s}", .{ options.output_source.filename, @errorName(err) });
+        try error_handler.emitMessage(gpa, .err, "unable to create output file '{s}': {s}", .{ options.output_source.filename, @errorName(err) });
         std.process.exit(1);
     };
-    defer coff_stream.deinit(allocator);
+    defer coff_stream.deinit(gpa);
 
     var coff_output_buffer: [4096]u8 = undefined;
-    var coff_output_buffered_stream = coff_stream.source.writer(allocator, &coff_output_buffer);
+    var coff_output_buffered_stream = coff_stream.source.writer(gpa, &coff_output_buffer);
 
     var cvtres_diagnostics: cvtres.Diagnostics = .{ .none = {} };
-    cvtres.writeCoff(allocator, coff_output_buffered_stream.interface(), resources.list.items, options.coff_options, &cvtres_diagnostics) catch |err| {
+    cvtres.writeCoff(gpa, coff_output_buffered_stream.interface(), resources.list.items, options.coff_options, &cvtres_diagnostics) catch |err| {
         switch (err) {
             error.DuplicateResource => {
                 const duplicate_resource = resources.list.items[cvtres_diagnostics.duplicate_resource];
-                try error_handler.emitMessage(allocator, .err, "duplicate resource [id: {f}, type: {f}, language: {f}]", .{
+                try error_handler.emitMessage(gpa, .err, "duplicate resource [id: {f}, type: {f}, language: {f}]", .{
                     duplicate_resource.name_value,
                     fmtResourceType(duplicate_resource.type_value),
                     duplicate_resource.language,
@@ -374,8 +382,8 @@ pub fn main() !void {
             },
             error.ResourceDataTooLong => {
                 const overflow_resource = resources.list.items[cvtres_diagnostics.duplicate_resource];
-                try error_handler.emitMessage(allocator, .err, "resource has a data length that is too large to be written into a coff section", .{});
-                try error_handler.emitMessage(allocator, .note, "the resource with the invalid size is [id: {f}, type: {f}, language: {f}]", .{
+                try error_handler.emitMessage(gpa, .err, "resource has a data length that is too large to be written into a coff section", .{});
+                try error_handler.emitMessage(gpa, .note, "the resource with the invalid size is [id: {f}, type: {f}, language: {f}]", .{
                     overflow_resource.name_value,
                     fmtResourceType(overflow_resource.type_value),
                     overflow_resource.language,
@@ -383,15 +391,15 @@ pub fn main() !void {
             },
             error.TotalResourceDataTooLong => {
                 const overflow_resource = resources.list.items[cvtres_diagnostics.duplicate_resource];
-                try error_handler.emitMessage(allocator, .err, "total resource data exceeds the maximum of the coff 'size of raw data' field", .{});
-                try error_handler.emitMessage(allocator, .note, "size overflow occurred when attempting to write this resource: [id: {f}, type: {f}, language: {f}]", .{
+                try error_handler.emitMessage(gpa, .err, "total resource data exceeds the maximum of the coff 'size of raw data' field", .{});
+                try error_handler.emitMessage(gpa, .note, "size overflow occurred when attempting to write this resource: [id: {f}, type: {f}, language: {f}]", .{
                     overflow_resource.name_value,
                     fmtResourceType(overflow_resource.type_value),
                     overflow_resource.language,
                 });
             },
             else => {
-                try error_handler.emitMessage(allocator, .err, "unable to write coff output file '{s}': {s}", .{ coff_stream.name, @errorName(err) });
+                try error_handler.emitMessage(gpa, .err, "unable to write coff output file '{s}': {s}", .{ coff_stream.name, @errorName(err) });
             },
         }
         // Delete the output file on error
@@ -423,7 +431,7 @@ const IoStream = struct {
         };
     }
 
-    pub fn deinit(self: *IoStream, allocator: std.mem.Allocator) void {
+    pub fn deinit(self: *IoStream, allocator: Allocator) void {
         self.source.deinit(allocator);
     }
 
@@ -458,7 +466,7 @@ const IoStream = struct {
             }
         }
 
-        pub fn deinit(self: *Source, allocator: std.mem.Allocator) void {
+        pub fn deinit(self: *Source, allocator: Allocator) void {
             switch (self.*) {
                 .file => |file| file.close(),
                 .stdio => {},
@@ -471,18 +479,18 @@ const IoStream = struct {
             bytes: []const u8,
             needs_free: bool,
 
-            pub fn deinit(self: Data, allocator: std.mem.Allocator) void {
+            pub fn deinit(self: Data, allocator: Allocator) void {
                 if (self.needs_free) {
                     allocator.free(self.bytes);
                 }
             }
         };
 
-        pub fn readAll(self: Source, allocator: std.mem.Allocator) !Data {
+        pub fn readAll(self: Source, allocator: Allocator, io: Io) !Data {
             return switch (self) {
                 inline .file, .stdio => |file| .{
                     .bytes = b: {
-                        var file_reader = file.reader(&.{});
+                        var file_reader = file.reader(io, &.{});
                         break :b try file_reader.interface.allocRemaining(allocator, .unlimited);
                     },
                     .needs_free = true,
@@ -496,7 +504,7 @@ const IoStream = struct {
             file: std.fs.File.Writer,
             allocating: std.Io.Writer.Allocating,
 
-            pub const Error = std.mem.Allocator.Error || std.fs.File.WriteError;
+            pub const Error = Allocator.Error || std.fs.File.WriteError;
 
             pub fn interface(this: *@This()) *std.Io.Writer {
                 return switch (this.*) {
@@ -514,7 +522,7 @@ const IoStream = struct {
             }
         };
 
-        pub fn writer(source: *Source, allocator: std.mem.Allocator, buffer: []u8) Writer {
+        pub fn writer(source: *Source, allocator: Allocator, buffer: []u8) Writer {
             return switch (source.*) {
                 .file, .stdio => |file| .{ .file = file.writer(buffer) },
                 .memory => |*list| .{ .allocating = .fromArrayList(allocator, list) },
@@ -525,17 +533,20 @@ const IoStream = struct {
 };
 
 const LazyIncludePaths = struct {
-    arena: std.mem.Allocator,
+    arena: Allocator,
+    io: Io,
     auto_includes_option: cli.Options.AutoIncludes,
     zig_lib_dir: []const u8,
     target_machine_type: std.coff.IMAGE.FILE.MACHINE,
     resolved_include_paths: ?[]const []const u8 = null,
 
     pub fn get(self: *LazyIncludePaths, error_handler: *ErrorHandler) ![]const []const u8 {
+        const io = self.io;
+
         if (self.resolved_include_paths) |include_paths|
             return include_paths;
 
-        return getIncludePaths(self.arena, self.auto_includes_option, self.zig_lib_dir, self.target_machine_type) catch |err| switch (err) {
+        return getIncludePaths(self.arena, io, self.auto_includes_option, self.zig_lib_dir, self.target_machine_type) catch |err| switch (err) {
             error.OutOfMemory => |e| return e,
             else => |e| {
                 switch (e) {
@@ -556,7 +567,13 @@ const LazyIncludePaths = struct {
     }
 };
 
-fn getIncludePaths(arena: std.mem.Allocator, auto_includes_option: cli.Options.AutoIncludes, zig_lib_dir: []const u8, target_machine_type: std.coff.IMAGE.FILE.MACHINE) ![]const []const u8 {
+fn getIncludePaths(
+    arena: Allocator,
+    io: Io,
+    auto_includes_option: cli.Options.AutoIncludes,
+    zig_lib_dir: []const u8,
+    target_machine_type: std.coff.IMAGE.FILE.MACHINE,
+) ![]const []const u8 {
     if (auto_includes_option == .none) return &[_][]const u8{};
 
     const includes_arch: std.Target.Cpu.Arch = switch (target_machine_type) {
@@ -626,7 +643,7 @@ fn getIncludePaths(arena: std.mem.Allocator, auto_includes_option: cli.Options.A
                     .cpu_arch = includes_arch,
                     .abi = .gnu,
                 };
-                const target = std.zig.resolveTargetQueryOrFatal(target_query);
+                const target = std.zig.resolveTargetQueryOrFatal(io, target_query);
                 const is_native_abi = target_query.isNativeAbi();
                 const detected_libc = std.zig.LibCDirs.detect(arena, zig_lib_dir, &target, is_native_abi, true, null) catch |err| switch (err) {
                     error.OutOfMemory => |e| return e,
@@ -647,7 +664,7 @@ const ErrorHandler = union(enum) {
 
     pub fn emitCliDiagnostics(
         self: *ErrorHandler,
-        allocator: std.mem.Allocator,
+        allocator: Allocator,
         args: []const []const u8,
         diagnostics: *cli.Diagnostics,
     ) !void {
@@ -666,7 +683,7 @@ const ErrorHandler = union(enum) {
 
     pub fn emitAroDiagnostics(
         self: *ErrorHandler,
-        allocator: std.mem.Allocator,
+        allocator: Allocator,
         fail_msg: []const u8,
         comp: *aro.Compilation,
     ) !void {
@@ -692,7 +709,7 @@ const ErrorHandler = union(enum) {
 
     pub fn emitDiagnostics(
         self: *ErrorHandler,
-        allocator: std.mem.Allocator,
+        allocator: Allocator,
         cwd: std.fs.Dir,
         source: []const u8,
         diagnostics: *Diagnostics,
@@ -713,7 +730,7 @@ const ErrorHandler = union(enum) {
 
     pub fn emitMessage(
         self: *ErrorHandler,
-        allocator: std.mem.Allocator,
+        allocator: Allocator,
         msg_type: @import("utils.zig").ErrorMessageType,
         comptime format: []const u8,
         args: anytype,
@@ -738,7 +755,7 @@ const ErrorHandler = union(enum) {
 };
 
 fn cliDiagnosticsToErrorBundle(
-    gpa: std.mem.Allocator,
+    gpa: Allocator,
     diagnostics: *cli.Diagnostics,
 ) !ErrorBundle {
     @branchHint(.cold);
@@ -783,7 +800,7 @@ fn cliDiagnosticsToErrorBundle(
 }
 
 fn diagnosticsToErrorBundle(
-    gpa: std.mem.Allocator,
+    gpa: Allocator,
     source: []const u8,
     diagnostics: *Diagnostics,
     mappings: SourceMappings,
@@ -870,7 +887,7 @@ fn diagnosticsToErrorBundle(
     return try bundle.toOwnedBundle("");
 }
 
-fn errorStringToErrorBundle(allocator: std.mem.Allocator, comptime format: []const u8, args: anytype) !ErrorBundle {
+fn errorStringToErrorBundle(allocator: Allocator, comptime format: []const u8, args: anytype) !ErrorBundle {
     @branchHint(.cold);
     var bundle: ErrorBundle.Wip = undefined;
     try bundle.init(allocator);
diff --git a/lib/compiler/resinator/utils.zig b/lib/compiler/resinator/utils.zig
index b535ab9c71..021b8cf4de 100644
--- a/lib/compiler/resinator/utils.zig
+++ b/lib/compiler/resinator/utils.zig
@@ -26,7 +26,11 @@ pub const UncheckedSliceWriter = struct {
 /// Cross-platform 'std.fs.Dir.openFile' wrapper that will always return IsDir if
 /// a directory is attempted to be opened.
 /// TODO: Remove once https://github.com/ziglang/zig/issues/5732 is addressed.
-pub fn openFileNotDir(cwd: std.fs.Dir, path: []const u8, flags: std.fs.File.OpenFlags) std.fs.File.OpenError!std.fs.File {
+pub fn openFileNotDir(
+    cwd: std.fs.Dir,
+    path: []const u8,
+    flags: std.fs.File.OpenFlags,
+) (std.fs.File.OpenError || std.fs.File.StatError)!std.fs.File {
     const file = try cwd.openFile(path, flags);
     errdefer file.close();
     // https://github.com/ziglang/zig/issues/5732