posix portability: linux syscalls -> libc (std.c) in one shared path. All raw std.os.linux.* call sites converted with the errno-convention flip (libc returns -1 + thread-local errno, not -errno): open/close/read/write/rename in tty.zig, gui.zig, look.zig; harness too (snapshot.zig: getcwd/mkdir/chdir/fork+waitpid/getdents64->opendir-readdir, e2e_harness.zig: clock_gettime/write/close), so the parity suite itself is POSIX-portable. Per-OS branches kept only where platforms genuinely diverge: shellCwd in look.zig (linux /proc/<pid>/cwd readlink; darwin libproc proc_pidinfo PROC_PIDVNODEPATHINFO with a hand-declared extern; other POSIX degrades to null), bash path (/usr/bin/bash on linux, /bin/bash elsewhere), TIOCSWINSZ constant (absent from std.c.T on darwin). forkpty/execv/chdir externs were already libc and are portable (fork-safety preserved: absolute-path execv, no malloc between fork and exec, initial spawns before worker threads). build.zig: forward target/optimize to the ghostty dep for native/cross (web keeps its no-target fetch), disable ghostty simd for darwin cross-builds (apple_sdk needs xcrun; scalar fallback = web config), link libutil on the BSDs. Pinned ghostty needs two one-line zig-0.16 darwin fixes, applied in the zig-pkg cache and documented in build.zig. Verified: aarch64-macos + x86_64-macos + x86_64-freebsd cross-compiles green; linux native tty + gui + web green; snapshot suite 18/18 with goldens untouched. Out of scope: gui-on-macos needs Metal shaders (SDL GPU rejects our SPIR-V there).

2 files changed, 41 insertions, 59 deletions

diff --git a/test/e2e_harness.zig b/test/e2e_harness.zig
index 6354aa4b..9099f13e 100644
--- a/test/e2e_harness.zig
+++ b/test/e2e_harness.zig
@@ -1,8 +1,11 @@
 const std = @import("std");
 const posix = std.posix;
-const linux = std.os.linux;
+const libc = std.c;
 const ghostty_vt = @import("ghostty-vt");
 
+// TIOCSWINSZ: absent from std.c.T on darwin — _IOW('t', 103, winsize)
+const TIOCSWINSZ: c_int = @bitCast(@as(u32, if (@hasDecl(posix.T, "IOCSWINSZ")) posix.T.IOCSWINSZ else 0x80087467));
+
 extern "c" fn forkpty(
     amaster: *c_int,
     name: ?[*:0]u8,
@@ -13,9 +16,9 @@ extern "c" fn execvp(file: [*:0]const u8, argv: [*:null]const ?[*:0]const u8) c_
 extern "c" fn _exit(status: c_int) noreturn;
 
 fn nowMs() i64 {
-    var ts: linux.timespec = undefined;
-    _ = linux.clock_gettime(linux.CLOCK.MONOTONIC, &ts);
-    return ts.sec * 1000 + @divFloor(@as(i64, ts.nsec), 1_000_000);
+    var ts: libc.timespec = undefined;
+    _ = libc.clock_gettime(.MONOTONIC, &ts);
+    return @as(i64, @intCast(ts.sec)) * 1000 + @divFloor(@as(i64, @intCast(ts.nsec)), 1_000_000);
 }
 
 /// E2E test harness: forks the app in a pty and parses its output with a
@@ -92,7 +95,7 @@ pub const Harness = struct {
 
     pub fn deinit(self: *Harness) void {
         posix.kill(self.pid, posix.SIG.KILL) catch {};
-        _ = linux.close(self.master);
+        _ = libc.close(self.master);
         self.stream.deinit();
         self.raw.deinit(self.gpa);
         self.term.deinit(self.gpa);
@@ -103,10 +106,9 @@ pub const Harness = struct {
     pub fn send(self: *Harness, bytes: []const u8) !void {
         var off: usize = 0;
         while (off < bytes.len) {
-            const rc = linux.write(self.master, bytes[off..].ptr, bytes.len - off);
-            const n: isize = @bitCast(rc);
+            const n = libc.write(self.master, bytes[off..].ptr, bytes.len - off);
             if (n < 0) {
-                if (n == -@as(isize, @intFromEnum(linux.E.INTR))) continue;
+                if (libc.errno(n) == .INTR) continue;
                 return error.WriteFailed;
             }
             off += @intCast(n);
@@ -139,7 +141,7 @@ pub const Harness = struct {
         self.cols = cols;
         self.term.resize(self.gpa, cols, rows) catch {};
         const ws = posix.winsize{ .row = rows, .col = cols, .xpixel = 0, .ypixel = 0 };
-        _ = posix.system.ioctl(self.master, posix.T.IOCSWINSZ, @intFromPtr(&ws));
+        _ = posix.system.ioctl(self.master, TIOCSWINSZ, @intFromPtr(&ws));
     }
 
     /// The full viewport text (plainString), newline-joined rows. Caller frees.
@@ -261,18 +263,15 @@ pub const Harness = struct {
     }
 };
 
-/// Write a file (helper for test setup, raw linux syscalls).
+/// Write a file (helper for test setup, raw libc).
 pub fn writeFile(path: [*:0]const u8, data: []const u8) !void {
-    const rc = linux.open(path, .{ .ACCMODE = .WRONLY, .CREAT = true, .TRUNC = true }, 0o644);
-    const sfd: isize = @bitCast(rc);
-    if (sfd < 0) return error.OpenFailed;
-    const fd: c_int = @intCast(sfd);
-    defer _ = linux.close(fd);
+    const fd = libc.open(path, .{ .ACCMODE = .WRONLY, .CREAT = true, .TRUNC = true }, @as(libc.mode_t, 0o644));
+    if (fd < 0) return error.OpenFailed;
+    defer _ = libc.close(fd);
     var off: usize = 0;
     while (off < data.len) {
-        const w = linux.write(fd, data[off..].ptr, data.len - off);
-        const sw: isize = @bitCast(w);
-        if (sw <= 0) break;
-        off += @intCast(sw);
+        const w = libc.write(fd, data[off..].ptr, data.len - off);
+        if (w <= 0) break;
+        off += @intCast(w);
     }
 }
diff --git a/test/snapshot.zig b/test/snapshot.zig
index c1bf03c0..10aa0c86 100644
--- a/test/snapshot.zig
+++ b/test/snapshot.zig
@@ -28,8 +28,7 @@
 //   snap <label>              capture grid text + cursor
 //   snapstyle <label>         capture per-cell style runs (fg,bg,attrs)
 const std = @import("std");
-const posix = std.posix;
-const linux = std.os.linux;
+const libc = std.c;
 const ghostty_vt = @import("ghostty-vt");
 const eh = @import("e2e_harness.zig");
 
@@ -48,9 +47,8 @@ pub fn main(init: std.process.Init) !void {
     // argv: exe-under-test, then flags/scripts. All paths made absolute up
     // front because runScript chdirs into a per-script workdir.
     var cwd_buf: [4096]u8 = undefined;
-    const cwd_rc: isize = @bitCast(linux.getcwd(&cwd_buf, cwd_buf.len));
-    if (cwd_rc <= 0) fatal("getcwd failed", .{});
-    const orig_cwd = cwd_buf[0..@intCast(cwd_rc - 1)];
+    const cwd_p = libc.getcwd(&cwd_buf, cwd_buf.len) orelse fatal("getcwd failed", .{});
+    const orig_cwd = std.mem.span(@as([*:0]u8, @ptrCast(cwd_p)));
 
     var exe: ?[]const u8 = null;
     var update = false;
@@ -461,41 +459,26 @@ fn absPath(arena: std.mem.Allocator, cwd: []const u8, p: []const u8) ![]const u8
 
 fn listSnaps(arena: std.mem.Allocator, dir_path: []const u8, scripts: *std.ArrayList([]const u8)) !void {
     const dir_z = try arena.dupeZ(u8, dir_path);
-    const rc = linux.open(dir_z, .{ .ACCMODE = .RDONLY, .DIRECTORY = true }, 0);
-    const sfd: isize = @bitCast(rc);
-    if (sfd < 0) fatal("no snapshots/ dir at {s}", .{dir_path});
-    const fd: i32 = @intCast(sfd);
-    defer _ = linux.close(fd);
-    var buf: [8192]u8 align(@alignOf(linux.dirent64)) = undefined;
-    while (true) {
-        const r = linux.getdents64(fd, &buf, buf.len);
-        const n: isize = @bitCast(r);
-        if (n <= 0) break;
-        var off: usize = 0;
-        while (off < @as(usize, @intCast(n))) {
-            const d: *align(1) linux.dirent64 = @ptrCast(&buf[off]);
-            const name = std.mem.span(@as([*:0]const u8, @ptrCast(&d.name)));
-            if (std.mem.endsWith(u8, name, ".snap"))
-                try scripts.append(arena, try std.fmt.allocPrint(arena, "{s}/{s}", .{ dir_path, name }));
-            off += d.reclen;
-        }
+    const dir = libc.opendir(dir_z) orelse fatal("no snapshots/ dir at {s}", .{dir_path});
+    defer _ = libc.closedir(dir);
+    while (libc.readdir(dir)) |d| {
+        const name = std.mem.sliceTo(@as([*:0]const u8, @ptrCast(&d.name)), 0);
+        if (std.mem.endsWith(u8, name, ".snap"))
+            try scripts.append(arena, try std.fmt.allocPrint(arena, "{s}/{s}", .{ dir_path, name }));
     }
 }
 
 fn readFileAlloc(arena: std.mem.Allocator, path: []const u8) ![]u8 {
     const path_z = try arena.dupeZ(u8, path);
-    const rc = linux.open(path_z, .{ .ACCMODE = .RDONLY }, 0);
-    const sfd: isize = @bitCast(rc);
-    if (sfd < 0) return error.OpenFailed;
-    const fd: i32 = @intCast(sfd);
-    defer _ = linux.close(fd);
+    const fd = libc.open(path_z, .{ .ACCMODE = .RDONLY });
+    if (fd < 0) return error.OpenFailed;
+    defer _ = libc.close(fd);
     var buf: std.ArrayList(u8) = .empty;
     var chunk: [16384]u8 = undefined;
     while (true) {
-        const r = linux.read(fd, &chunk, chunk.len);
-        const n: isize = @bitCast(r);
+        const n = libc.read(fd, &chunk, chunk.len);
         if (n < 0) {
-            if (n == -@as(isize, @intFromEnum(linux.E.INTR))) continue;
+            if (libc.errno(n) == .INTR) continue;
             return error.ReadFailed;
         }
         if (n == 0) break;
@@ -506,15 +489,15 @@ fn readFileAlloc(arena: std.mem.Allocator, path: []const u8) ![]u8 {
 
 fn mkdir(arena: std.mem.Allocator, path: []const u8, exist_ok: bool) !void {
     const path_z = try arena.dupeZ(u8, path);
-    const n: isize = @bitCast(linux.mkdir(path_z, 0o755));
-    if (n < 0) {
-        if (exist_ok and n == -@as(isize, @intFromEnum(linux.E.EXIST))) return;
+    const rc = libc.mkdir(path_z, 0o755);
+    if (rc != 0) {
+        if (exist_ok and libc.errno(rc) == .EXIST) return;
         return error.MkdirFailed;
     }
 }
 
-fn chdirRc(path_z: [:0]const u8) isize {
-    return @bitCast(linux.chdir(path_z.ptr));
+fn chdirRc(path_z: [:0]const u8) c_int {
+    return libc.chdir(path_z.ptr);
 }
 
 fn rmrf(path: []const u8) void {
@@ -522,15 +505,15 @@ fn rmrf(path: []const u8) void {
     if (path.len >= path_buf.len) return;
     @memcpy(path_buf[0..path.len], path);
     path_buf[path.len] = 0;
-    const pid: isize = @bitCast(linux.fork());
+    const pid = libc.fork();
     if (pid == 0) {
         const argv: [4:null]?[*:0]const u8 = .{ "rm", "-rf", @as([*:0]const u8, @ptrCast(&path_buf)), null };
         _ = execvp("rm", &argv);
-        linux.exit_group(127);
+        libc._exit(127);
     }
     if (pid < 0) return;
-    var status: u32 = 0;
-    _ = linux.wait4(@intCast(pid), &status, 0, null);
+    var status: c_int = 0;
+    _ = libc.waitpid(pid, &status, 0);
 }
 
 fn printFirstDiff(golden: []const u8, actual: []const u8) void {