diff --git a/lib/compiler/build_runner.zig b/lib/compiler/build_runner.zig
index 1a019c80d968..d73fb6d29dc6 100644
--- a/lib/compiler/build_runner.zig
+++ b/lib/compiler/build_runner.zig
@@ -415,7 +415,7 @@ pub fn main() !void {
         else => return err,
     };
 
-    var w = if (watch) try Watch.init() else undefined;
+    var w: Watch = if (watch and Watch.have_impl) try Watch.init() else undefined;
 
     try run.thread_pool.init(thread_pool_options);
     defer run.thread_pool.deinit();
@@ -435,6 +435,9 @@ pub fn main() !void {
             else => return err,
         };
         if (fuzz) {
+            if (builtin.single_threaded) {
+                fatal("--fuzz not yet implemented for single-threaded builds", .{});
+            }
             switch (builtin.os.tag) {
                 // Current implementation depends on two things that need to be ported to Windows:
                 // * Memory-mapping to share data between the fuzzer and build runner.
diff --git a/lib/std/Build/Watch.zig b/lib/std/Build/Watch.zig
index 13540a2b36cf..bae3af1f63bd 100644
--- a/lib/std/Build/Watch.zig
+++ b/lib/std/Build/Watch.zig
@@ -600,7 +600,7 @@ const Os = switch (builtin.os.tag) {
             };
         }
     },
-    .dragonfly, .freebsd, .netbsd, .openbsd, .ios, .macos, .tvos, .visionos, .watchos, .haiku => struct {
+    .dragonfly, .freebsd, .netbsd, .openbsd, .ios, .macos, .tvos, .visionos, .watchos => struct {
         const posix = std.posix;
 
         kq_fd: i32,
diff --git a/lib/std/c.zig b/lib/std/c.zig
index 25d45ae8a6f7..390d5f89c3cd 100644
--- a/lib/std/c.zig
+++ b/lib/std/c.zig
@@ -5703,6 +5703,9 @@ pub const SOCK = switch (native_os) {
         pub const RAW = 3;
         pub const SEQPACKET = 5;
         pub const MISC = 255;
+
+        pub const NONBLOCK = 0x40000;
+        pub const CLOEXEC = 0x80000;
     },
     .openbsd => struct {
         pub const STREAM = 1;
@@ -10824,8 +10827,8 @@ pub const LC = enum(c_int) {
 
 pub extern "c" fn setlocale(category: LC, locale: ?[*:0]const u8) ?[*:0]const u8;
 
-pub const getcontext = if (builtin.target.abi.isAndroid() or builtin.target.os.tag == .openbsd)
-{} // android bionic and openbsd libc does not implement getcontext
+pub const getcontext = if (builtin.target.abi.isAndroid() or builtin.target.os.tag == .openbsd or builtin.target.os.tag == .haiku)
+{} // libc does not implement getcontext
     else if (native_os == .linux and builtin.target.abi.isMusl())
         linux.getcontext
     else
diff --git a/lib/std/c/haiku.zig b/lib/std/c/haiku.zig
index a9877d07e3fc..bfac0cfa559b 100644
--- a/lib/std/c/haiku.zig
+++ b/lib/std/c/haiku.zig
@@ -23,6 +23,11 @@ pub extern "root" fn get_system_info(system_info: *system_info) usize;
 pub extern "root" fn _get_team_info(team: i32, team_info: *team_info, size: usize) i32;
 pub extern "root" fn _get_next_area_info(team: i32, cookie: *i64, area_info: *area_info, size: usize) i32;
 pub extern "root" fn _get_next_image_info(team: i32, cookie: *i32, image_info: *image_info, size: usize) i32;
+pub extern "root" fn _kern_get_current_team() team_id;
+pub extern "root" fn _kern_open_dir(fd: fd_t, path: [*:0]const u8) fd_t;
+pub extern "root" fn _kern_read_dir(fd: fd_t, buffer: [*]u8, bufferSize: usize, maxCount: u32) isize;
+pub extern "root" fn _kern_rewind_dir(fd: fd_t) status_t;
+pub extern "root" fn _kern_read_stat(fd: fd_t, path: [*:0]const u8, traverseLink: bool, stat: *std.c.Stat, statSize: usize) status_t;
 
 pub const area_info = extern struct {
     area: u32,
diff --git a/lib/std/crypto/Certificate/Bundle.zig b/lib/std/crypto/Certificate/Bundle.zig
index a74eb44a9174..437f7a224c36 100644
--- a/lib/std/crypto/Certificate/Bundle.zig
+++ b/lib/std/crypto/Certificate/Bundle.zig
@@ -64,6 +64,7 @@ pub fn rescan(cb: *Bundle, gpa: Allocator) RescanError!void {
         .netbsd => return rescanWithPath(cb, gpa, "/etc/openssl/certs/ca-certificates.crt"),
         .dragonfly => return rescanWithPath(cb, gpa, "/usr/local/etc/ssl/cert.pem"),
         .solaris, .illumos => return rescanWithPath(cb, gpa, "/etc/ssl/cacert.pem"),
+        .haiku => return rescanWithPath(cb, gpa, "/boot/system/data/ssl/CARootCertificates.pem"),
         // https://github.com/SerenityOS/serenity/blob/222acc9d389bc6b490d4c39539761b043a4bfcb0/Ports/ca-certificates/package.sh#L19
         .serenity => return rescanWithPath(cb, gpa, "/etc/ssl/certs/ca-certificates.crt"),
         .windows => return rescanWindows(cb, gpa),
diff --git a/lib/std/fs/Dir.zig b/lib/std/fs/Dir.zig
index 6075c8ca0fe1..90c46740ca25 100644
--- a/lib/std/fs/Dir.zig
+++ b/lib/std/fs/Dir.zig
@@ -13,6 +13,7 @@ pub const Entry = struct {
 
 const IteratorError = error{
     AccessDenied,
+    PermissionDenied,
     SystemResources,
     /// WASI-only. The path of an entry could not be encoded as valid UTF-8.
     /// WASI is unable to handle paths that cannot be encoded as well-formed UTF-8.
@@ -287,7 +288,7 @@ pub const Iterator = switch (native_os) {
                     name,
                     false,
                     &stat_info,
-                    0,
+                    @sizeOf(posix.Stat),
                 )))) {
                     .SUCCESS => {},
                     .INVAL => unreachable,