diff --git a/CMakeLists.txt b/CMakeLists.txt
index b2c423ddda..73813a0d43 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1230,17 +1230,15 @@ else()
     target_link_libraries(${bun} PRIVATE base64::base64)
 endif()
 
-if(NOT WIN32)
-    if(USE_CUSTOM_TINYCC)
-        if(WIN32)
-            target_link_libraries(${bun} PRIVATE "${BUN_DEPS_OUT_DIR}/tcc.lib")
-        else()
-            target_link_libraries(${bun} PRIVATE "${BUN_DEPS_OUT_DIR}/libtcc.a")
-        endif()
+if(USE_CUSTOM_TINYCC)
+    if(WIN32)
+        target_link_libraries(${bun} PRIVATE "${BUN_DEPS_OUT_DIR}/tcc.lib")
     else()
-        find_package(tinycc REQUIRED)
-        target_link_libraries(${bun} PRIVATE tinycc::tinycc)
+        target_link_libraries(${bun} PRIVATE "${BUN_DEPS_OUT_DIR}/libtcc.a")
     endif()
+else()
+    find_package(tinycc REQUIRED)
+    target_link_libraries(${bun} PRIVATE tinycc::tinycc)
 endif()
 
 if(USE_CUSTOM_LOLHTML)
diff --git a/scripts/all-dependencies.ps1 b/scripts/all-dependencies.ps1
index 67ddb6ef94..f4426e4709 100644
--- a/scripts/all-dependencies.ps1
+++ b/scripts/all-dependencies.ps1
@@ -65,9 +65,9 @@ Build-Dependency `
 Build-Dependency `
   -Script "mimalloc" `
   -Outputs @("mimalloc.lib")
-# Build-Dependency `
-#   -Script "tinycc" `
-#   -Outputs @("tcc.lib")
+Build-Dependency `
+  -Script "tinycc" `
+  -Outputs @("tcc.lib")
 Build-Dependency `
   -Script "zlib" `
   -Outputs @("zlib.lib")
diff --git a/scripts/build-tinycc.ps1 b/scripts/build-tinycc.ps1
new file mode 100644
index 0000000000..a671be2ddf
--- /dev/null
+++ b/scripts/build-tinycc.ps1
@@ -0,0 +1,30 @@
+$ErrorActionPreference = 'Stop'  # Setting strict mode, similar to 'set -euo pipefail' in bash
+. (Join-Path $PSScriptRoot "env.ps1")
+
+Push-Location (Join-Path $BUN_DEPS_DIR 'tinycc')
+try {
+  cd win32
+  Run .\build-tcc.bat -clean
+  cd ..
+
+  Set-Content -Path config.h -Value @"
+#define TCC_VERSION "$(Get-Content VERSION)"
+#define TCC_GITHASH "$(git rev-parse --short HEAD)"
+#define CONFIG_TCCDIR "$((Get-Location).Path.Replace('\', '/'))"
+#define CONFIG_TCC_PREDEFS 1
+#ifdef TCC_TARGET_X86_64
+#define CONFIG_TCC_CROSSPREFIX "$PX%-"
+#endif
+"@
+
+  Run clang-cl -DTCC_TARGET_PE -DTCC_TARGET_X86_64 config.h -DC2STR -o c2str.exe conftest.c
+  Run .\c2str.exe .\include\tccdefs.h tccdefs_.h
+
+  # TODO: -MT
+  Run clang-cl libtcc.c -o tcc.obj "-DTCC_TARGET_PE" "-DTCC_TARGET_X86_64" "-O2" "-W2" "-Zi" "-MD" "-GS-" "-c"
+  Run lib "tcc.obj" "-OUT:tcc.lib"
+
+  Copy-Item tcc.obj $BUN_DEPS_OUT_DIR/tcc.lib
+
+  Write-Host "-> tcc.lib"
+} finally { Pop-Location }
diff --git a/src/bun.js/WebKit b/src/bun.js/WebKit
index b4de09f41b..347037014a 160000
--- a/src/bun.js/WebKit
+++ b/src/bun.js/WebKit
@@ -1 +1 @@
-Subproject commit b4de09f41b83e9e5c0e43ef414f1aee5968b6f7c
+Subproject commit 347037014ae069eed1c4f4687001a256949b124e
diff --git a/src/bun.js/api/FFI.h b/src/bun.js/api/FFI.h
index dfe6395106..effe7dc13a 100644
--- a/src/bun.js/api/FFI.h
+++ b/src/bun.js/api/FFI.h
@@ -1,11 +1,11 @@
 // This file is part of Bun!
 // You can find the original source:
-// https://github.com/oven-sh/bun/blob/main/src/bun.js/api/FFI.h#L2
+// https://github.com/oven-sh/bun/blob/main/src/bun.js/api/FFI.h
 //
 // clang-format off
 // This file is only compatible with 64 bit CPUs
 // It must be kept in sync with JSCJSValue.h
-// https://github.com/oven-sh/WebKit/blob/72c2052b781cbfd4af867ae79ac9de460e392fba/Source/JavaScriptCore/runtime/JSCJSValue.h#L455-L458
+// https://github.com/oven-sh/WebKit/blob/main/Source/JavaScriptCore/runtime/JSCJSValue.h
 #ifdef IS_CALLBACK
 #define INJECT_BEFORE int c = 500; // This is a callback, so we need to inject code before the call
 #endif
diff --git a/src/bun.js/api/ffi.zig b/src/bun.js/api/ffi.zig
index ad38445d53..44b0ac3827 100644
--- a/src/bun.js/api/ffi.zig
+++ b/src/bun.js/api/ffi.zig
@@ -670,9 +670,7 @@ pub const FFI = struct {
             val.arg_types.clearAndFree(allocator);
 
             if (val.state) |state| {
-                if (comptime !Environment.isWindows) {
-                    TCC.tcc_delete(state);
-                }
+                TCC.tcc_delete(state);
                 val.state = null;
             }
 
@@ -772,9 +770,6 @@ pub const FFI = struct {
             this: *Function,
             allocator: std.mem.Allocator,
         ) !void {
-            if (comptime Environment.isWindows) {
-                return;
-            }
             var source_code = std.ArrayList(u8).init(allocator);
             var source_code_writer = source_code.writer();
             try this.printSourceCode(&source_code_writer);
@@ -789,9 +784,7 @@ pub const FFI = struct {
             this.state = state;
             defer {
                 if (this.step == .failed) {
-                    if (comptime !Environment.isWindows) {
-                        TCC.tcc_delete(state);
-                    }
+                    TCC.tcc_delete(state);
                     this.state = null;
                 }
             }
@@ -900,9 +893,6 @@ pub const FFI = struct {
             }
 
             pub fn inject(state: *TCC.TCCState) void {
-                if (comptime Environment.isWindows) {
-                    return;
-                }
                 JSC.markBinding(@src());
                 _ = TCC.tcc_add_symbol(state, "memset", &memset);
                 _ = TCC.tcc_add_symbol(state, "memcpy", &memcpy);
@@ -943,9 +933,6 @@ pub const FFI = struct {
             js_function: JSValue,
             is_threadsafe: bool,
         ) !void {
-            if (comptime Environment.isWindows) {
-                return;
-            }
             JSC.markBinding(@src());
             var source_code = std.ArrayList(u8).init(allocator);
             var source_code_writer = source_code.writer();
@@ -969,9 +956,7 @@ pub const FFI = struct {
             this.state = state;
             defer {
                 if (this.step == .failed) {
-                    if (comptime !Environment.isWindows) {
-                        TCC.tcc_delete(state);
-                    }
+                    TCC.tcc_delete(state);
                     this.state = null;
                 }
             }
@@ -1256,22 +1241,7 @@ pub const FFI = struct {
 
             // -- Generate the FFI function symbol
             try writer.writeAll("\n \n/* --- The Callback Function */\n");
-            try writer.writeAll("/* --- The Callback Function */\n");
-            try this.return_type.typename(writer);
-            try writer.writeAll(" my_callback_function");
-            try writer.writeAll("(");
             var first = true;
-            for (this.arg_types.items, 0..) |arg, i| {
-                if (!first) {
-                    try writer.writeAll(", ");
-                }
-                first = false;
-                try arg.typename(writer);
-                try writer.print(" arg{d}", .{i});
-            }
-            try writer.writeAll(");\n\n");
-
-            first = true;
             try this.return_type.typename(writer);
 
             try writer.writeAll(" my_callback_function");
diff --git a/src/bun.js/node/node_fs.zig b/src/bun.js/node/node_fs.zig
index c785163470..55e75cc09a 100644
--- a/src/bun.js/node/node_fs.zig
+++ b/src/bun.js/node/node_fs.zig
@@ -5226,43 +5226,6 @@ pub const NodeFS = struct {
                 _ = bun.sys.close(fd);
         }
 
-        if (Environment.isWindows) {
-            const native_fd = bun.fdcast(fd);
-
-            var data = args.data.slice();
-
-            // "WriteFile sets this value to zero before doing any work or error checking."
-            var bytes_written: u32 = undefined;
-
-            while (data.len > 0) {
-                const adjusted_len = @min(data.len, std.math.maxInt(u32));
-                const rc = std.os.windows.kernel32.WriteFile(native_fd, data.ptr, adjusted_len, &bytes_written, null);
-                if (rc == 0) {
-                    return .{
-                        .err = Syscall.Error{
-                            .errno = @intFromEnum(std.os.windows.kernel32.GetLastError()),
-                            .syscall = .WriteFile,
-                            .fd = fd,
-                        },
-                    };
-                }
-                data = data[bytes_written..];
-            }
-
-            const rc = std.os.windows.kernel32.SetEndOfFile(bun.fdcast(fd));
-            if (rc == 0) {
-                return .{
-                    .err = Syscall.Error{
-                        .errno = @intFromEnum(std.os.windows.kernel32.GetLastError()),
-                        .syscall = .WriteFile,
-                        .fd = fd,
-                    },
-                };
-            }
-
-            return Maybe(Return.WriteFile).success;
-        }
-
         var buf = args.data.slice();
         var written: usize = 0;
 
@@ -5298,7 +5261,7 @@ pub const NodeFS = struct {
         }
 
         while (buf.len > 0) {
-            switch (Syscall.write(fd, buf)) {
+            switch (bun.sys.write(fd, buf)) {
                 .err => |err| return .{
                     .err = err,
                 },
@@ -5312,9 +5275,22 @@ pub const NodeFS = struct {
             }
         }
 
-        // https://github.com/oven-sh/bun/issues/2931
-        if ((@intFromEnum(args.flag) & std.os.O.APPEND) == 0) {
-            _ = ftruncateSync(.{ .fd = fd, .len = @as(JSC.WebCore.Blob.SizeType, @truncate(written)) });
+        if (Environment.isWindows) {
+            const rc = std.os.windows.kernel32.SetEndOfFile(bun.fdcast(fd));
+            if (rc == 0) {
+                return .{
+                    .err = Syscall.Error{
+                        .errno = @intFromEnum(std.os.windows.kernel32.GetLastError()),
+                        .syscall = .SetEndOfFile,
+                        .fd = fd,
+                    },
+                };
+            }
+        } else {
+            // https://github.com/oven-sh/bun/issues/2931
+            if ((@intFromEnum(args.flag) & std.os.O.APPEND) == 0) {
+                _ = ftruncateSync(.{ .fd = fd, .len = @as(JSC.WebCore.Blob.SizeType, @truncate(written)) });
+            }
         }
 
         return Maybe(Return.WriteFile).success;
diff --git a/src/bun.js/webcore/blob.zig b/src/bun.js/webcore/blob.zig
index bab81a6ca5..e9e5808f5d 100644
--- a/src/bun.js/webcore/blob.zig
+++ b/src/bun.js/webcore/blob.zig
@@ -1192,18 +1192,23 @@ pub const Blob = struct {
             var file_path: [bun.MAX_PATH_BYTES]u8 = undefined;
             switch (bun.sys.open(
                 pathlike.path.sliceZ(&file_path),
-                // we deliberately don't use O_TRUNC here
-                // it's a perf optimization
-                std.os.O.WRONLY | std.os.O.CREAT | std.os.O.NONBLOCK,
+                if (!Environment.isWindows)
+                    // we deliberately don't use O_TRUNC here
+                    // it's a perf optimization
+                    std.os.O.WRONLY | std.os.O.CREAT | std.os.O.NONBLOCK
+                else
+                    std.os.O.WRONLY | std.os.O.CREAT,
                 write_permissions,
             )) {
                 .result => |result| {
                     break :brk result;
                 },
                 .err => |err| {
-                    if (err.getErrno() == .NOENT) {
-                        needs_async.* = true;
-                        return .zero;
+                    if (!Environment.isWindows) {
+                        if (err.getErrno() == .NOENT) {
+                            needs_async.* = true;
+                            return .zero;
+                        }
                     }
 
                     return JSC.JSPromise.rejectedPromiseValue(
@@ -1212,16 +1217,13 @@ pub const Blob = struct {
                     );
                 },
             }
-            unreachable;
         };
 
-        var truncate = needs_open or bytes.len == 0;
+        // TODO: on windows this is always synchronous
+
+        const truncate = needs_open or bytes.len == 0;
         var written: usize = 0;
         defer {
-            if (truncate) {
-                _ = bun.sys.ftruncate(fd, @as(i64, @intCast(written)));
-            }
-
             if (needs_open) {
                 _ = bun.sys.close(fd);
             }
@@ -1239,13 +1241,17 @@ pub const Blob = struct {
                     if (res == 0) break;
                 },
                 .err => |err| {
-                    truncate = false;
-                    if (err.getErrno() == .AGAIN) {
-                        needs_async.* = true;
-                        return .zero;
+                    if (!Environment.isWindows) {
+                        if (err.getErrno() == .AGAIN) {
+                            needs_async.* = true;
+                            return .zero;
+                        }
                     }
                     if (comptime !needs_open) {
-                        return JSC.JSPromise.rejectedPromiseValue(globalThis, err.toJSC(globalThis));
+                        return JSC.JSPromise.rejectedPromiseValue(
+                            globalThis,
+                            err.toJSC(globalThis),
+                        );
                     }
                     return JSC.JSPromise.rejectedPromiseValue(
                         globalThis,
@@ -1255,6 +1261,14 @@ pub const Blob = struct {
             }
         }
 
+        if (truncate) {
+            if (Environment.isWindows) {
+                _ = std.os.windows.kernel32.SetEndOfFile(bun.fdcast(fd));
+            } else {
+                _ = bun.sys.ftruncate(fd, @as(i64, @intCast(written)));
+            }
+        }
+
         return JSC.JSPromise.resolvedPromiseValue(globalThis, JSC.JSValue.jsNumber(written));
     }
 
diff --git a/src/deps/tinycc b/src/deps/tinycc
index 2d3ad9e0d3..ab631362d8 160000
--- a/src/deps/tinycc
+++ b/src/deps/tinycc
@@ -1 +1 @@
-Subproject commit 2d3ad9e0d32194ad7fd867b66ebe218dcc8cb5cd
+Subproject commit ab631362d839333660a265d3084d8ff060b96753
diff --git a/src/sys.zig b/src/sys.zig
index 14bd23b046..d49ca15687 100644
--- a/src/sys.zig
+++ b/src/sys.zig
@@ -132,6 +132,7 @@ pub const Tag = enum(u8) {
     GetFinalPathNameByHandle,
     CloseHandle,
     SetFilePointerEx,
+    SetEndOfFile,
 
     pub fn isWindows(this: Tag) bool {
         return @intFromEnum(this) > @intFromEnum(Tag.WriteFile);
@@ -681,6 +682,7 @@ pub fn closeAllowingStdoutAndStderr(fd: bun.FileDescriptor) ?Syscall.Error {
 pub const max_count = switch (builtin.os.tag) {
     .linux => 0x7ffff000,
     .macos, .ios, .watchos, .tvos => std.math.maxInt(i32),
+    .windows => std.math.maxInt(u32),
     else => std.math.maxInt(isize),
 };
 
@@ -696,7 +698,7 @@ pub fn write(fd: bun.FileDescriptor, bytes: []const u8) Maybe(usize) {
                 return err;
             }
 
-            return Maybe(usize){ .result = @as(usize, @intCast(rc)) };
+            return Maybe(usize){ .result = @intCast(rc) };
         },
         .linux => {
             while (true) {
@@ -708,10 +710,31 @@ pub fn write(fd: bun.FileDescriptor, bytes: []const u8) Maybe(usize) {
                     return err;
                 }
 
-                return Maybe(usize){ .result = @as(usize, @intCast(rc)) };
+                return Maybe(usize){ .result = @intCast(rc) };
             }
         },
-        .windows => sys_uv.write(fd, bytes),
+        .windows => {
+            // "WriteFile sets this value to zero before doing any work or error checking."
+            var bytes_written: u32 = undefined;
+            std.debug.assert(bytes.len > 0);
+            const rc = std.os.windows.kernel32.WriteFile(
+                bun.fdcast(fd),
+                bytes.ptr,
+                adjusted_len,
+                &bytes_written,
+                null,
+            );
+            if (rc == 0) {
+                return .{
+                    .err = Syscall.Error{
+                        .errno = @intFromEnum(bun.windows.getLastErrno()),
+                        .syscall = .WriteFile,
+                        .fd = fd,
+                    },
+                };
+            }
+            return Maybe(usize){ .result = bytes_written };
+        },
         else => @compileError("Not implemented yet"),
     };
 }
diff --git a/src/sys_uv.zig b/src/sys_uv.zig
index c319c7f3c5..d4bd93f004 100644
--- a/src/sys_uv.zig
+++ b/src/sys_uv.zig
@@ -354,7 +354,7 @@ pub fn pwritev(fd: FileDescriptor, bufs: []const bun.PlatformIOVec, position: i6
     }
 
     if (rc.errno()) |errno| {
-        return .{ .err = .{ .errno = errno, .fd = fd, .syscall = .read } };
+        return .{ .err = .{ .errno = errno, .fd = fd, .syscall = .write } };
     } else {
         return .{ .result = @as(usize, @intCast(rc.value)) };
     }
diff --git a/src/windows.zig b/src/windows.zig
index da8d69c0ab..857b935564 100644
--- a/src/windows.zig
+++ b/src/windows.zig
@@ -2968,3 +2968,24 @@ pub extern "kernel32" fn SetFileInformationByHandle(
     fileInformation: LPVOID,
     bufferSize: DWORD,
 ) BOOL;
+
+pub fn getLastErrno() bun.C.E {
+    return switch (bun.windows.kernel32.GetLastError()) {
+        .SUCCESS => .SUCCESS,
+        .FILE_NOT_FOUND => .NOENT,
+        .PATH_NOT_FOUND => .NOENT,
+        .TOO_MANY_OPEN_FILES => .NOMEM,
+        .ACCESS_DENIED => .PERM,
+        .INVALID_HANDLE => .BADF,
+        .NOT_ENOUGH_MEMORY => .NOMEM,
+        .OUTOFMEMORY => .NOMEM,
+        .INVALID_PARAMETER => .INVAL,
+
+        else => |t| {
+            if (bun.Environment.isDebug) {
+                bun.Output.warn("Called getLastErrno with {s} which does not have a mapping to errno", .{@tagName(t)});
+            }
+            return .UNKNOWN;
+        },
+    };
+}