a native macOS backend: libpardes plus an AppKit shell

Adds -Dplatform=macos, a fourth backend beside tty, gui and web. Zig keeps the
core, the ptys, every effect and the worker threads; Swift owns NSApplication,
the window, input translation, and drawing the cell grid with CoreText. They
meet at a hand-written C ABI in src/macos/pardes.h, built as a static library
the app links.

The ABI is src/web.zig's boundary with the wasm removed, because both hosts are
the same animal: someone else owns the clock, feeds events in through flat
functions, and reads one packed cell buffer out. The browser proved the shape.
The one divergence is that the browser has no processes and forwards every
effect to JavaScript, whereas forkpty is right here, so src/macos.zig performs
them — spawn, write, resize_pty, save_file, new_file, write_dump, open_link,
set_clipboard. lsp, pipe and watch are answered with nothing and marked; the
core already tolerates that, since the browser answers none of them either.

This deliberately inverts ghostty's split, which was studied first and is
written up in docs/ghostty-macos-notes.md. Ghostty hands Zig a bare NSView*,
installs its own CALayer and owns the frame clock; Swift never renders. Pardes
does the opposite because its frame is already a cell grid and CoreText draws
one natively — the alternative is a second hand-rolled glyph atlas, which is
what most of gui.zig's 4,300 lines already are. It would also have been written
blind: the Swift half cannot be compiled here.

What makes the scaffold verifiable rather than dead code is that the Zig half is
ordinary POSIX and builds and tests on Linux. Borrowing ghostty's best trick,
build.zig translate-C's the header into the test build and src/macos.zig asserts
every constant, struct layout, and exported function's arity and widths against
it. That guard earned its place immediately: pardes_scroll grew a cell
coordinate after the Swift view had been written against the older form.

Skipped, and named as the upgrade path in docs/macos.md: the Xcode project,
xcframework, lipo and codesigning ghostty needs. All four exist for
distribution; a dev build is a swiftc invocation and a directory with a plist.

The Swift app is a scaffold and says so — every uncertain API spelling carries
an UNVERIFIED marker, and no part of it has been compiled.

tty is unaffected: 75/75 snapshot scripts and both unit suites pass.

10 files changed, 1833 insertions, 4 deletions

diff --git a/src/look.zig b/src/look.zig
index 4a8cb894..273e20c3 100644
--- a/src/look.zig
+++ b/src/look.zig
@@ -328,7 +328,7 @@ fn findEmbeddedSource(path: []const u8, allow_root_suffix: bool) ?embedded_sourc
 }
 
 const platform_has_fs = switch (pardes.platform) {
-    .tty, .gui => true,
+    .tty, .gui, .macos => true,
     .web => false,
 };
 
diff --git a/src/macos.zig b/src/macos.zig
new file mode 100644
index 00000000..8eb6179a
--- /dev/null
+++ b/src/macos.zig
@@ -0,0 +1,882 @@
+//! libpardes — the static library the native macOS app links against.
+//!
+//! The split, which is the whole design: Zig keeps the core, the ptys, every
+//! effect and the worker threads; Swift owns NSApplication, the window, input
+//! translation and drawing. src/macos/pardes.h is the contract between them and
+//! docs/macos.md argues for the shape.
+//!
+//! This is deliberately src/web.zig's boundary with the wasm removed. Both
+//! hosts are the same animal — someone else owns the clock, feeds events in
+//! through flat functions and reads one packed cell buffer out — and the
+//! browser already proved the shape works. The one real divergence is that the
+//! browser has no processes, so it forwards every effect to JavaScript, whereas
+//! forkpty is right here and this file performs them.
+//!
+//! Everything below is main-thread only. The single exception is the `wakeup`
+//! callback, which a pty reader task calls; the host's job is to hop to the
+//! main thread and call pardes_tick.
+//!
+//! The Zig half is ordinary POSIX and builds/tests on Linux — see the dev-loop
+//! section of docs/macos.md. Only the Swift app needs a Mac.
+
+const std = @import("std");
+const builtin = @import("builtin");
+const posix = std.posix;
+const libc = std.c;
+const pardes = @import("pardes.zig");
+const look = @import("look.zig");
+const temp_file = @import("temp_file.zig");
+const shell_bin = @import("shell_bin.zig");
+const message = @import("message.zig");
+const user_config = @import("user_config.zig");
+
+extern "c" fn forkpty(amaster: *c_int, name: ?[*:0]u8, termp: ?*const anyopaque, winp: ?*const posix.winsize) c_int;
+extern "c" fn execv(path: [*:0]const u8, argv: [*:null]const ?[*:0]const u8) c_int;
+extern "c" fn chdir(path: [*:0]const u8) c_int;
+extern "c" fn _exit(status: c_int) noreturn;
+extern "c" fn setenv(name: [*:0]const u8, value: [*:0]const u8, overwrite: c_int) c_int;
+
+// TIOCSWINSZ: absent from std.c.T on darwin — _IOW('t', 103, winsize). Same
+// constant the tty and gui shells spell for the same reason.
+const TIOCSWINSZ: c_int = @bitCast(@as(u32, if (@hasDecl(posix.T, "IOCSWINSZ")) posix.T.IOCSWINSZ else 0x80087467));
+
+// A library linked into an AppKit process has no terminal to garble, but it
+// does share the app's stderr with Console.app. Same filter as src/main.zig:
+// ghostty-vt narrates every unimplemented escape a child writes, and nobody
+// wants that in a crash report. PARDES_LOG=1 gets the real logger back.
+pub const std_options: std.Options = .{ .logFn = logFn };
+
+fn logFn(
+    comptime level: std.log.Level,
+    comptime scope: @EnumLiteral(),
+    comptime format: []const u8,
+    args: anytype,
+) void {
+    if (scope != .macos and scope != .dump and std.c.getenv("PARDES_LOG") == null) return;
+    std.log.defaultLog(level, scope, format, args);
+}
+
+const log = std.log.scoped(.macos);
+
+// ---------------------------------------------------------------- boundary
+
+/// Sync with: pardes_cell_s. The identical encoding is spelled a second time
+/// for the browser as WebCell in src/web.zig.
+///
+/// ponytail: two copies of a fifteen-line pure encoder, not a shared module.
+/// The web ABI is snapshot-tested through a headless Chrome that does not run
+/// here, so extracting it would refactor a backend I cannot exercise to save
+/// thirty lines. Merge them the day a third host wants the same bytes.
+pub const Cell = extern struct {
+    text: [8]u8,
+    fg: u32,
+    bg: u32,
+    attrs: u16,
+    len: u8,
+    flags: u8,
+};
+
+/// Sync with: pardes_runtime_s. Two callbacks, because everything else the
+/// core asks for it already does itself — it owns the ptys, and look.openLink
+/// hands URLs to /usr/bin/open. Both are optional at the ABI level: a host that
+/// passes null simply does without, rather than trapping inside the library.
+pub const Runtime = extern struct {
+    userdata: ?*anyopaque = null,
+    wakeup: ?*const fn (?*anyopaque) callconv(.c) void = null,
+    set_clipboard: ?*const fn (?*anyopaque, [*]const u8, usize) callconv(.c) void = null,
+};
+
+const color_default: u32 = 0x01000000;
+const color_indexed: u32 = 0x02000000;
+const cell_flag_default: u8 = 1;
+
+// ---------------------------------------------------------------- state
+
+/// One pty, and the task draining it. `gen` is the per-slot spawn generation:
+/// the core reuses pane ids and has no close effect, so a respawned slot must
+/// ignore the previous shell's late bytes rather than feed them to the new one.
+const Pty = struct {
+    file: std.Io.File,
+    pid: posix.pid_t,
+    gen: u32,
+    reader: std.Io.Future(anyerror!void),
+};
+
+/// What a reader task hands the main thread. `gen` travels with the message so
+/// a shell that was replaced while its read was in flight cannot have its
+/// stragglers parsed into the pty that took its slot.
+const Msg = union(enum) {
+    output: struct { pane: u8, gen: u32, bytes: []u8 },
+    eof: struct { pane: u8, gen: u32 },
+
+    fn free(m: Msg, gpa: std.mem.Allocator) void {
+        switch (m) {
+            .output => |o| gpa.free(o.bytes),
+            .eof => {},
+        }
+    }
+};
+
+/// 0.16 has no std.Thread.Mutex, and the gui shell's queue already settled
+/// this: spin on the lock-free std.atomic.Mutex, and keep the critical section
+/// to a pointer append. The reader allocates its chunk BEFORE taking the lock
+/// for exactly that reason — a screenful of output must not make a keystroke
+/// spin through a 64 KiB copy.
+///
+/// ponytail: unbounded. `yes` in a pane can enqueue faster than the host
+/// drains, and nothing throttles the reader — the tty shell gets that for free
+/// from vaxis's 512-slot queue, whose post blocks when full, and the SDL shell
+/// has the same hole this does. Bound it on queued bytes the day someone
+/// watches RSS climb; the trap to avoid is a wait that teardown cannot cancel.
+const Inbox = struct {
+    mutex: std.atomic.Mutex = .unlocked,
+    items: std.ArrayList(Msg) = .empty,
+    /// Set when a wakeup has been delivered and not yet answered by a tick.
+    /// Without it a busy shell posts one wakeup per 64 KiB chunk, and each one
+    /// is a block on the host's main queue — a screenful of output becomes
+    /// thousands of scheduled pumps that all find the same drained inbox.
+    wake_pending: std.atomic.Value(bool) = .init(false),
+
+    fn lock(q: *Inbox) void {
+        // Bounded, unlike the gui shell's otherwise identical spin. AppKit's
+        // main thread runs at a higher QoS than these reader tasks and a raw
+        // CAS spin donates no priority, so a reader preempted inside the append
+        // (which can realloc) would have the highest-priority thread in the
+        // process spinning on it. Yielding hands the core back.
+        var spins: u8 = 0;
+        while (!q.mutex.tryLock()) {
+            spins +%= 1;
+            if (spins == 0) std.Thread.yield() catch {} else std.atomic.spinLoopHint();
+        }
+    }
+
+    fn push(q: *Inbox, gpa: std.mem.Allocator, m: Msg) void {
+        q.lock();
+        defer q.mutex.unlock();
+        q.items.append(gpa, m) catch m.free(gpa);
+    }
+};
+
+const State = struct {
+    gpa: std.mem.Allocator,
+    threaded: *std.Io.Threaded,
+    io: std.Io,
+    core: *pardes.Pardes,
+    arena: std.heap.ArenaAllocator,
+    runtime: Runtime,
+    cells: std.ArrayList(Cell) = .empty,
+    /// The grid `cells` actually holds. Not read back off the core: a render
+    /// can move screen_w/screen_h and then fail, and a host that sized its
+    /// loops from those would walk off the buffer.
+    frame_cols: u16 = 0,
+    frame_rows: u16 = 0,
+    ptys: [pardes.MAX_PANES]?Pty = @splat(null),
+    inbox: Inbox = .{},
+    /// Per-slot spawn generation, owned by the main thread. A reader carries a
+    /// copy in every message it posts; anything that no longer matches belongs
+    /// to a shell this slot has already replaced.
+    gens: [pardes.MAX_PANES]u32 = @splat(0),
+    /// Sub-row wheel distance the core has not been told about yet. The core
+    /// moves a whole row at a time, so fractional trackpad travel accumulates
+    /// here and is spent as wheel presses — see pardes_scroll.
+    scroll_lag: f32 = 0,
+    /// Swapped with the inbox under the lock, so draining it costs one pointer
+    /// exchange and neither side reallocates once capacities have settled.
+    tick_msgs: std.ArrayList(Msg) = .empty,
+    /// Owns the bytes of the user config, which Options only borrows.
+    config_arena: std.heap.ArenaAllocator,
+};
+
+var state: ?State = null;
+
+// ---------------------------------------------------------------- lifecycle
+
+export fn pardes_init(runtime: ?*const Runtime, cols_arg: u16, rows_arg: u16) c_int {
+    if (state != null) return 1; // already up; deinit first
+    initCore(runtime, cols_arg, rows_arg) catch |err| {
+        log.err("init failed: {t}", .{err});
+        return 2;
+    };
+    return 0;
+}
+
+/// The body is split out purely so the cleanup below is real: `errdefer` fires
+/// on an error return and nothing else, so writing this inside an export that
+/// returns c_int would leave every one of these as dead code — and a half-built
+/// init leaks an arena, leaves zstbi pointing at a dead allocator, and (because
+/// Io.Threaded installs process-wide SIGIO/SIGPIPE handlers that only its
+/// deinit restores) hands those handlers permanently to the host app.
+fn initCore(runtime: ?*const Runtime, cols_arg: u16, rows_arg: u16) !void {
+    const gpa = std.heap.smp_allocator;
+
+    const threaded = try gpa.create(std.Io.Threaded);
+    errdefer gpa.destroy(threaded);
+    threaded.* = .init(gpa, .{});
+    errdefer threaded.deinit();
+    const io = threaded.io();
+
+    var config_arena: std.heap.ArenaAllocator = .init(gpa);
+    errdefer config_arena.deinit();
+
+    var opts: pardes.Options = .{ .tty_only = true };
+    // Native shells opt into the user config, and every builtin in it must have
+    // run before the host can render a frame — so it is read here, before
+    // Pardes.init, exactly as src/main.zig does it. The env map is rebuilt from
+    // libc's environ because a library has no std.process.Init to inherit one.
+    if (captureEnv(config_arena.allocator())) |*env|
+        opts.startup_config = user_config.load(io, config_arena.allocator(), env);
+
+    // stb_image's allocator shim, for image panes.
+    pardes.image.start(io, gpa);
+    errdefer pardes.image.stop();
+
+    const core = try pardes.Pardes.init(gpa, opts);
+    errdefer core.deinit();
+
+    // Shells emit OSC 133 prompt marks through these, which is what makes
+    // prompt hiding and click-to-move work.
+    writeFile(shell_bin.bash_rc_path, shell_bin.bash_rc);
+    writeFile(shell_bin.fish_rc_path, shell_bin.fish_rc);
+    // Apple's bash 3.2 prints the zsh-deprecation banner into every pane unless
+    // this is in the environment BEFORE bash starts — the rc file is too late.
+    if (comptime builtin.os.tag.isDarwin()) _ = setenv("BASH_SILENCE_DEPRECATION_WARNING", "1", 1);
+
+    state = .{
+        .gpa = gpa,
+        .threaded = threaded,
+        .io = io,
+        .core = core,
+        .arena = .init(gpa),
+        .config_arena = config_arena,
+        .runtime = if (runtime) |r| r.* else .{},
+    };
+    const st = &state.?;
+
+    // The real grid, delivered as an EVENT and not as Options.cols/rows: the
+    // core defers each shell's greeting until it has seen a resize, and the
+    // first forkpty below takes its winsize straight off the core.
+    const cols = @max(1, cols_arg);
+    const rows = @max(1, rows_arg);
+    core.update(.{ .resize = .{ .cols = cols, .rows = rows } });
+
+    // The initial spawns happen before any reader task exists, mirroring the
+    // tty shell. Note the difference in what that buys: tty.zig runs from
+    // main() and really is single-threaded there, whereas this is called from
+    // applicationDidFinishLaunching, by which point AppKit and libdispatch
+    // have long since spawned threads. What keeps the fork safe is the child
+    // itself — chdir and execv, raw syscalls with nothing allocated between
+    // fork and exec — not the thread count. Ordering it this way anyway keeps
+    // the two backends readable side by side.
+    _ = drainEffects(st, false);
+    for (&st.ptys, 0..) |*slot, id| if (slot.*) |*pt| startReader(st, pt, @intCast(id));
+}
+
+export fn pardes_deinit() void {
+    const st = &(state orelse return);
+    // Every reader is joined here, before anything it touches is freed. The
+    // runtime joins its tasks on exit, so a reader left parked in read(2) would
+    // hang the process instead of the app quitting.
+    for (0..pardes.MAX_PANES) |pane| reap(st, @intCast(pane));
+    // Only now is the inbox quiet. Anything still queued owns gpa bytes and
+    // would show up as a leak rather than as the shutdown it actually is.
+    for (st.inbox.items.items) |msg| msg.free(st.gpa);
+    st.inbox.items.deinit(st.gpa);
+    for (st.tick_msgs.items) |msg| msg.free(st.gpa);
+    st.tick_msgs.deinit(st.gpa);
+    st.cells.deinit(st.gpa);
+    st.core.deinit();
+    st.arena.deinit();
+    st.config_arena.deinit();
+    pardes.image.stop();
+    st.threaded.deinit();
+    st.gpa.destroy(st.threaded);
+    state = null;
+}
+
+export fn pardes_should_quit() bool {
+    const st = &(state orelse return true);
+    return st.core.quit;
+}
+
+export fn pardes_animating() bool {
+    const st = &(state orelse return false);
+    return st.core.themeAnimationActive();
+}
+
+/// Drain what the reader tasks collected into the core, then perform whatever
+/// the core queued in response. Returns whether anything moved, so an idle
+/// wakeup does not cost the host a repaint.
+export fn pardes_tick() bool {
+    const st = &(state orelse return false);
+    // Cleared BEFORE the swap: a reader that pushes while this drain is running
+    // must be able to schedule the tick that will collect it.
+    st.inbox.wake_pending.store(false, .release);
+    st.inbox.lock();
+    std.mem.swap(std.ArrayList(Msg), &st.inbox.items, &st.tick_msgs);
+    st.inbox.mutex.unlock();
+
+    var changed = st.tick_msgs.items.len > 0;
+    for (st.tick_msgs.items) |msg| {
+        defer msg.free(st.gpa);
+        switch (msg) {
+            .output => |o| {
+                if (st.gens[o.pane] != o.gen) continue;
+                st.core.update(.{ .output = .{ .pane = o.pane, .bytes = o.bytes } });
+            },
+            .eof => |e| {
+                if (st.gens[e.pane] != e.gen) continue;
+                // The shell is gone: join its reader (a completed future that
+                // is never awaited leaks its allocation), close the master and
+                // free the slot. Without this the slot is only ever reaped by a
+                // later spawn INTO it — and the core emits spawn from newPane
+                // alone, so a pane that becomes a file pane instead would hold
+                // the dead fd for the life of the app.
+                reap(st, e.pane);
+                st.core.update(.{ .eof = .{ .pane = e.pane } });
+            },
+        }
+    }
+    st.tick_msgs.clearRetainingCapacity();
+    if (drainEffects(st, true)) changed = true;
+    // A live theme transition repaints on its own clock; say so, or the host
+    // stops ticking and the fade freezes half-applied.
+    if (st.core.themeAnimationActive()) changed = true;
+    return changed;
+}
+
+// ---------------------------------------------------------------- events in
+
+export fn pardes_key(cp_arg: u32, text_ptr: ?[*]const u8, len: usize, mods: u32) void {
+    const st = &(state orelse return);
+    if (cp_arg > std.math.maxInt(u21)) return;
+    const text: []const u8 = if (text_ptr) |p| p[0..len] else "";
+    st.core.update(.{ .key = .{
+        .cp = @intCast(cp_arg),
+        .text = text,
+        .ctrl = mods & 1 != 0,
+        .alt = mods & 2 != 0,
+        .shift = mods & 4 != 0,
+    } });
+}
+
+export fn pardes_paste(text_ptr: ?[*]const u8, len: usize) void {
+    const st = &(state orelse return);
+    const text: []const u8 = if (text_ptr) |p| p[0..len] else "";
+    st.core.update(.{ .paste = text });
+}
+
+/// Button and kind arrive as their boundary ordinals. An out-of-range value is
+/// dropped rather than reaching an unchecked enum cast — same rule the browser
+/// ABI keeps, for the same reason: the host is not part of this build.
+export fn pardes_mouse(button_arg: c_int, kind_arg: c_int, col: u16, row: u16, mods: u32) void {
+    const st = &(state orelse return);
+    const button: pardes.Mouse.Button = switch (button_arg) {
+        0 => .left,
+        1 => .middle,
+        2 => .right,
+        3 => .wheel_up,
+        4 => .wheel_down,
+        5 => .wheel_left,
+        6 => .wheel_right,
+        7 => .none,
+        else => return,
+    };
+    const kind: pardes.Mouse.Kind = switch (kind_arg) {
+        0 => .press,
+        1 => .release,
+        2 => .motion,
+        3 => .drag,
+        else => return,
+    };
+    st.core.update(.{ .mouse = .{
+        .button = button,
+        .kind = kind,
+        .col = col,
+        .row = row,
+        .ctrl = mods & 1 != 0,
+    } });
+}
+
+export fn pardes_scroll(delta_rows: f32, col: u16, row: u16) void {
+    const st = &(state orelse return);
+    const ticks = takeScrollTicks(&st.scroll_lag, delta_rows);
+    var left = ticks;
+    while (left != 0) {
+        const down = left > 0;
+        left += if (down) -1 else 1;
+        st.core.update(.{ .mouse = .{
+            .button = if (down) .wheel_down else .wheel_up,
+            .kind = .press,
+            .col = col,
+            .row = row,
+        } });
+    }
+}
+
+export fn pardes_resize(cols_arg: u16, rows_arg: u16, cell_w: u16, cell_h: u16) void {
+    const st = &(state orelse return);
+    const cols = @max(1, cols_arg);
+    const rows = @max(1, rows_arg);
+    st.core.update(.{ .resize = .{
+        .cols = cols,
+        .rows = rows,
+        .cell_pixels = if (@hasField(pardes.CellPixels, "w"))
+            .{ .w = @max(1, cell_w), .h = @max(1, cell_h) }
+        else
+            .{},
+    } });
+}
+
+// ---------------------------------------------------------------- frame out
+
+export fn pardes_frame() u32 {
+    const st = &(state orelse return 0);
+    _ = st.arena.reset(.retain_capacity);
+    // The three accessors below must never describe a different frame than the
+    // count this returns, so a failure empties all of them together rather than
+    // leaving last frame's buffer behind a fresh cols/rows.
+    st.cells.clearRetainingCapacity();
+    st.frame_cols = 0;
+    st.frame_rows = 0;
+    const surface = st.core.render(st.arena.allocator()) catch |err| {
+        log.err("render failed: {t}", .{err});
+        return 0;
+    };
+    const count: usize = @as(usize, surface.cols) * surface.rows;
+    st.cells.resize(st.gpa, count) catch return 0;
+    st.frame_cols = surface.cols;
+    st.frame_rows = surface.rows;
+    for (surface.cells, st.cells.items) |cell, *out| {
+        out.* = .{
+            .text = @splat(0),
+            .fg = encodeColor(cell.style.fg),
+            .bg = encodeColor(cell.style.bg),
+            .attrs = encodeAttrs(cell.style),
+            .len = if (cell.default) 1 else cell.len,
+            .flags = @intFromBool(cell.default),
+        };
+        if (cell.default) out.text[0] = ' ' else @memcpy(out.text[0..cell.len], cell.grapheme());
+    }
+    return @intCast(count);
+}
+
+export fn pardes_frame_cells() ?[*]const Cell {
+    const st = &(state orelse return null);
+    return if (st.cells.items.len == 0) null else st.cells.items.ptr;
+}
+
+export fn pardes_frame_cols() u16 {
+    const st = &(state orelse return 0);
+    return st.frame_cols;
+}
+
+export fn pardes_frame_rows() u16 {
+    const st = &(state orelse return 0);
+    return st.frame_rows;
+}
+
+export fn pardes_cursor_x() i32 {
+    const st = &(state orelse return -1);
+    return if (st.core.surface.cursor) |c| c.x else -1;
+}
+
+export fn pardes_cursor_y() i32 {
+    const st = &(state orelse return -1);
+    return if (st.core.surface.cursor) |c| c.y else -1;
+}
+
+export fn pardes_cursor_bar() bool {
+    const st = &(state orelse return false);
+    return if (st.core.surface.cursor) |c| c.bar else false;
+}
+
+// ---------------------------------------------------------------- effects
+
+/// Perform the IO the core queued. `threads_ok` is false for the one drain
+/// inside pardes_init, which runs before any reader task exists.
+///
+/// ponytail: the lsp, pipe and watch effects are answered with nothing. Each
+/// wants real machinery — a worker plus a snapshot of the pane's file for lsp
+/// (src/tty/tty.zig:919), a job copy for pipe, and FSEvents for watch, since
+/// inotify is Linux-only. The core is built to tolerate an unanswered effect:
+/// the browser answers none of these either. Lift tty.zig's implementations
+/// when the app is past first light.
+fn drainEffects(st: *State, threads_ok: bool) bool {
+    const core = st.core;
+    var did = false;
+    while (core.nextEffect()) |effect| {
+        did = true;
+        switch (effect) {
+            .spawn => |sp| {
+                // The core reuses pane ids and has no close effect, so a
+                // deleted pane's shell lives in its slot until a respawn lands
+                // here. Reap it: cancel joins the reader, and the generation
+                // bump makes its late bytes and eof unreadable.
+                reap(st, sp.pane);
+                st.gens[sp.pane] +%= 1;
+                const gen = st.gens[sp.pane];
+
+                const cwd = sp.cwd.slice();
+                var cwd_buf: [256:0]u8 = undefined;
+                var cwd_z: ?[*:0]const u8 = null;
+                // <= because writing the sentinel slot of a [N:0]u8 is legal,
+                // and Effect's cwd buffer is exactly 256: `<` would silently
+                // drop a maximal path and start the shell wherever the app
+                // bundle was launched from instead.
+                if (cwd.len > 0 and cwd.len <= cwd_buf.len) {
+                    @memcpy(cwd_buf[0..cwd.len], cwd);
+                    cwd_buf[cwd.len] = 0;
+                    cwd_z = @ptrCast(&cwd_buf);
+                }
+                const child = forkShell(core.shellBin(), cwd_z, core.screen_h, core.screen_w);
+                st.ptys[sp.pane] = .{
+                    .file = child.file,
+                    .pid = child.pid,
+                    .gen = gen,
+                    .reader = .{ .any_future = null, .result = {} },
+                };
+                // Report the pane's starting directory back to the core (tags).
+                var lbuf: [1024]u8 = undefined;
+                if (look.shellCwd(child.pid, &lbuf)) |wd| core.setCwd(sp.pane, wd);
+                if (threads_ok) if (st.ptys[sp.pane]) |*pt| startReader(st, pt, sp.pane);
+            },
+            .write => |w| {
+                if (st.ptys[w.pane]) |pt| writeFd(pt.file.handle, w.bytes.slice());
+            },
+            .resize_pty => |rs| {
+                if (st.ptys[rs.pane]) |pt| {
+                    const ws: posix.winsize = .{ .row = rs.rows, .col = rs.cols, .xpixel = 0, .ypixel = 0 };
+                    _ = posix.system.ioctl(pt.file.handle, TIOCSWINSZ, @intFromPtr(&ws));
+                }
+            },
+            .open_link => |url| look.openLink(url.slice()),
+            .save_file => |sf| {
+                const pane = core.panes[sf.pane] orelse continue;
+                const f = pane.file orelse continue;
+                var pathbuf: [4096:0]u8 = undefined;
+                if (f.path.len >= pathbuf.len) continue;
+                @memcpy(pathbuf[0..f.path.len], f.path);
+                pathbuf[f.path.len] = 0;
+                const fd = libc.open(pathbuf[0..f.path.len :0], .{ .ACCMODE = .WRONLY, .CREAT = true, .TRUNC = true }, @as(libc.mode_t, 0o644));
+                if (fd < 0) continue;
+                writeFd(fd, f.content);
+                _ = libc.close(fd);
+                // After the write, not beside it: every `continue` above is a
+                // save that did not happen and must not be reported as one.
+                var mbuf: [256]u8 = undefined;
+                core.setMessage(sf.pane, message.stamp(&mbuf, "saved", f.path));
+            },
+            .new_file => |request| {
+                var path_buf: [4096:0]u8 = undefined;
+                const made = temp_file.create(&path_buf) orelse continue;
+                if (core.openNewFile(request.pane, request.serial, made.path))
+                    made.adopt()
+                else
+                    made.discard();
+            },
+            .write_dump => {
+                const out = core.dump_out orelse continue;
+                var pbuf: [1024:0]u8 = undefined;
+                const path = pardes.dump.outPath(&pbuf) orelse continue;
+                const fd = libc.open(path, .{ .ACCMODE = .WRONLY, .CREAT = true, .TRUNC = true }, @as(libc.mode_t, 0o644));
+                if (fd < 0) continue;
+                writeFd(fd, out);
+                _ = libc.close(fd);
+                core.setLastDump(path);
+            },
+            .set_clipboard => {
+                const cb = st.runtime.set_clipboard orelse continue;
+                const y = core.yank orelse continue;
+                cb(st.runtime.userdata, y.ptr, y.len);
+            },
+            .lsp, .pipe, .watch => {},
+            .quit => {},
+        }
+    }
+    return did;
+}
+
+// ---------------------------------------------------------------- workers
+
+fn startReader(st: *State, pt: *Pty, id: u8) void {
+    pt.reader = st.io.concurrent(readPty, .{ st, st.io, pt.file, id, pt.gen }) catch |err| {
+        // No reader means the shell fills its pty buffer, blocks in write(2)
+        // and the pane silently freezes. Nothing recovers it, so at least say
+        // so — this is what PARDES_LOG exists for.
+        log.err("pane {d} has no reader ({t}); it will not show output", .{ id, err });
+        return;
+    };
+}
+
+/// Release one pane's shell: join the reader, close the master, reap the child.
+/// Order matters — cancel is what unblocks a task parked in read(2), and the fd
+/// must not be closed under a live reader. Called on eof and again on a spawn
+/// into the same slot, so it has to tolerate an empty slot.
+fn reap(st: *State, pane: u8) void {
+    var pt = st.ptys[pane] orelse return;
+    st.ptys[pane] = null;
+    pt.reader.cancel(st.io) catch {};
+    _ = libc.close(pt.file.handle);
+    // A library inside an app that runs for hours cannot leave these: the tty
+    // shell gets away with never reaping because the process exits seconds
+    // later, but here it would be one zombie per shell ever opened. NOHANG
+    // because the child may still be dying and the UI thread must not wait for
+    // it; the next reap or process exit collects whatever is left.
+    _ = libc.waitpid(pt.pid, null, posix.W.NOHANG);
+}
+
+/// Drain one pty into its inbox and wake the host. The same shape as the tty
+/// shell's reader, with the vaxis event queue replaced by a mutex and one
+/// callback: do the blocking thing away from the loop, hand the bytes over,
+/// leave the core a state machine that never waits.
+fn readPty(st: *State, io: std.Io, pty: std.Io.File, id: u8, gen: u32) anyerror!void {
+    var read_buf: [0x10000]u8 = undefined;
+    var reader = pty.readerStreaming(io, &read_buf);
+    while (true) {
+        var buf: [0x10000]u8 = undefined;
+        var vec = [_][]u8{&buf};
+        const n = reader.interface.readVec(&vec) catch break;
+        if (n == 0) break;
+        // Duped outside the lock on purpose — see Inbox.
+        const bytes = st.gpa.dupe(u8, buf[0..n]) catch break;
+        st.inbox.push(st.gpa, .{ .output = .{ .pane = id, .gen = gen, .bytes = bytes } });
+        wake(st);
+    }
+    st.inbox.push(st.gpa, .{ .eof = .{ .pane = id, .gen = gen } });
+    wake(st);
+}
+
+/// Ask the host for a tick, at most once per tick. `pardes_tick` clears the
+/// flag before it drains, so a push that lands mid-drain still wakes and no
+/// message can be left sitting in the inbox with nobody scheduled to read it.
+fn wake(st: *State) void {
+    const cb = st.runtime.wakeup orelse return;
+    if (st.inbox.wake_pending.swap(true, .acq_rel)) return;
+    cb(st.runtime.userdata);
+}
+
+// ---------------------------------------------------------------- helpers
+
+fn forkShell(bin: []const u8, cwd: ?[*:0]const u8, rows: u16, cols: u16) struct { file: std.Io.File, pid: posix.pid_t } {
+    var master: c_int = undefined;
+    // Resolved BEFORE the fork, into this frame, which the child inherits:
+    // nothing between fork and exec may allocate, so a PATH search cannot
+    // happen there.
+    var path_buf: [std.fs.max_path_bytes]u8 = undefined;
+    const spawn = shell_bin.resolve(bin, &path_buf);
+    const ws = posix.winsize{ .row = rows, .col = cols, .xpixel = 0, .ypixel = 0 };
+    const pid = forkpty(&master, null, null, &ws);
+    if (pid == 0) {
+        if (cwd) |c| _ = chdir(c);
+        _ = execv(spawn.path, &spawn.argv);
+        _exit(127);
+    }
+    return .{ .file = .{ .handle = master, .flags = .{ .nonblocking = false } }, .pid = pid };
+}
+
+fn writeFd(fd: c_int, data: []const u8) void {
+    var off: usize = 0;
+    while (off < data.len) {
+        const n = libc.write(fd, data[off..].ptr, data.len - off);
+        if (n < 0) {
+            if (libc.errno(n) == .INTR) continue;
+            return;
+        }
+        // A zero-byte write makes no progress; looping on it would spin the
+        // main thread forever, which here means a beachball rather than the
+        // tty shell's hung terminal.
+        if (n == 0) return;
+        off += @intCast(n);
+    }
+}
+
+fn writeFile(path: [*:0]const u8, contents: []const u8) void {
+    const fd = libc.open(path, .{ .ACCMODE = .WRONLY, .CREAT = true, .TRUNC = true }, @as(libc.mode_t, 0o644));
+    if (fd < 0) return;
+    defer _ = libc.close(fd);
+    writeFd(fd, contents);
+}
+
+/// Rebuild the process environment as a Map, because a library never sees the
+/// std.process.Init that main() gets one from. Only the config-path lookup
+/// reads it, and the arena owns the copies for the life of the process.
+fn captureEnv(arena: std.mem.Allocator) ?std.process.Environ.Map {
+    var map: std.process.Environ.Map = .init(arena);
+    const environ = std.c.environ;
+    var i: usize = 0;
+    while (environ[i]) |entry| : (i += 1) {
+        const line = std.mem.span(entry);
+        const eq = std.mem.indexOfScalar(u8, line, '=') orelse continue;
+        map.put(line[0..eq], line[eq + 1 ..]) catch return null;
+    }
+    return map;
+}
+
+fn encodeColor(color: pardes.Color) u32 {
+    return switch (color) {
+        .default => color_default,
+        .index => |index| color_indexed | @as(u32, index),
+        .rgb => |rgb| (@as(u32, rgb[0]) << 16) | (@as(u32, rgb[1]) << 8) | rgb[2],
+    };
+}
+
+fn encodeAttrs(style: pardes.CellStyle) u16 {
+    var attrs: u16 = 0;
+    attrs |= @as(u16, @intFromBool(style.bold)) << 0;
+    attrs |= @as(u16, @intFromBool(style.dim)) << 1;
+    attrs |= @as(u16, @intFromBool(style.italic)) << 2;
+    attrs |= @as(u16, @intFromBool(style.blink)) << 3;
+    attrs |= @as(u16, @intFromBool(style.reverse)) << 4;
+    attrs |= @as(u16, @intFromBool(style.invisible)) << 5;
+    attrs |= @as(u16, @intFromBool(style.strikethrough)) << 6;
+    attrs |= @as(u16, @intFromEnum(style.ul)) << 8;
+    return attrs;
+}
+
+/// Spend accumulated sub-row travel as whole wheel notches, keeping the
+/// remainder. The core has no fractional scroll — both other shells do this
+/// same accumulation host-side (stepScroll in gui.zig, the drain loop in
+/// web/app.mjs) — so it lives here and the Swift side stays a translator.
+///
+/// The lag is clamped to one screen's worth so a nonsense delta (an inertial
+/// fling reported in points, a NaN) cannot spin the emit loop.
+fn takeScrollTicks(lag: *f32, delta_rows: f32) i32 {
+    if (!std.math.isFinite(delta_rows)) return 0;
+    const next = std.math.clamp(lag.* + delta_rows, -256, 256);
+    if (!std.math.isFinite(next)) return 0;
+    const whole: i32 = @intFromFloat(@trunc(next));
+    lag.* = next - @as(f32, @floatFromInt(whole));
+    return whole;
+}
+
+// ---------------------------------------------------------------- ABI guard
+
+// The header is hand-written, so nothing but a test keeps it honest. build.zig
+// translate-C's src/macos/pardes.h into this test build and every constant and
+// layout below is asserted against the Zig side — ghostty's trick, and the
+// cheapest possible insurance against a silent ABI skew.
+/// Compare one declaration's arity and scalar widths against the header's.
+/// Not a type equality — translate-C spells pointers `[*c]` and mints its own
+/// struct types, so nothing here would ever match exactly. Arity and width are
+/// what actually break: a parameter added on one side only (which is how the
+/// Swift host first got pardes_scroll wrong), or a u16 that became a u32.
+fn expectSameAbi(comptime C: type, comptime Z: type) !void {
+    const c_fn = @typeInfo(C).@"fn";
+    const z_fn = @typeInfo(Z).@"fn";
+    try std.testing.expectEqual(c_fn.params.len, z_fn.params.len);
+    inline for (c_fn.params, z_fn.params) |cp, zp|
+        try std.testing.expectEqual(@sizeOf(cp.type.?), @sizeOf(zp.type.?));
+    try std.testing.expectEqual(@sizeOf(c_fn.return_type.?), @sizeOf(z_fn.return_type.?));
+}
+
+test "pardes.h declares every export the way it is defined" {
+    const c = @import("pardes.h");
+    try expectSameAbi(@TypeOf(c.pardes_init), @TypeOf(pardes_init));
+    try expectSameAbi(@TypeOf(c.pardes_deinit), @TypeOf(pardes_deinit));
+    try expectSameAbi(@TypeOf(c.pardes_tick), @TypeOf(pardes_tick));
+    try expectSameAbi(@TypeOf(c.pardes_should_quit), @TypeOf(pardes_should_quit));
+    try expectSameAbi(@TypeOf(c.pardes_animating), @TypeOf(pardes_animating));
+    try expectSameAbi(@TypeOf(c.pardes_key), @TypeOf(pardes_key));
+    try expectSameAbi(@TypeOf(c.pardes_paste), @TypeOf(pardes_paste));
+    try expectSameAbi(@TypeOf(c.pardes_mouse), @TypeOf(pardes_mouse));
+    try expectSameAbi(@TypeOf(c.pardes_scroll), @TypeOf(pardes_scroll));
+    try expectSameAbi(@TypeOf(c.pardes_resize), @TypeOf(pardes_resize));
+    try expectSameAbi(@TypeOf(c.pardes_frame), @TypeOf(pardes_frame));
+    try expectSameAbi(@TypeOf(c.pardes_frame_cells), @TypeOf(pardes_frame_cells));
+    try expectSameAbi(@TypeOf(c.pardes_frame_cols), @TypeOf(pardes_frame_cols));
+    try expectSameAbi(@TypeOf(c.pardes_frame_rows), @TypeOf(pardes_frame_rows));
+    try expectSameAbi(@TypeOf(c.pardes_cursor_x), @TypeOf(pardes_cursor_x));
+    try expectSameAbi(@TypeOf(c.pardes_cursor_y), @TypeOf(pardes_cursor_y));
+    try expectSameAbi(@TypeOf(c.pardes_cursor_bar), @TypeOf(pardes_cursor_bar));
+}
+
+test "pardes.h matches the Zig boundary" {
+    const c = @import("pardes.h");
+    const expectEqual = std.testing.expectEqual;
+
+    try expectEqual(@sizeOf(c.pardes_cell_s), @sizeOf(Cell));
+    try expectEqual(@offsetOf(c.pardes_cell_s, "text"), @offsetOf(Cell, "text"));
+    try expectEqual(@offsetOf(c.pardes_cell_s, "fg"), @offsetOf(Cell, "fg"));
+    try expectEqual(@offsetOf(c.pardes_cell_s, "bg"), @offsetOf(Cell, "bg"));
+    try expectEqual(@offsetOf(c.pardes_cell_s, "attrs"), @offsetOf(Cell, "attrs"));
+    try expectEqual(@offsetOf(c.pardes_cell_s, "len"), @offsetOf(Cell, "len"));
+    try expectEqual(@offsetOf(c.pardes_cell_s, "flags"), @offsetOf(Cell, "flags"));
+    try expectEqual(@sizeOf(c.pardes_runtime_s), @sizeOf(Runtime));
+
+    try expectEqual(@as(u32, c.PARDES_COLOR_DEFAULT), color_default);
+    try expectEqual(@as(u32, c.PARDES_COLOR_INDEXED), color_indexed);
+    try expectEqual(@as(u8, c.PARDES_CELL_DEFAULT), cell_flag_default);
+
+    // Every key the host has a name for must be the codepoint the core reads.
+    try expectEqual(@as(u21, c.PARDES_KEY_ENTER), pardes.Key.enter);
+    try expectEqual(@as(u21, c.PARDES_KEY_ESCAPE), pardes.Key.escape);
+    try expectEqual(@as(u21, c.PARDES_KEY_TAB), pardes.Key.tab);
+    try expectEqual(@as(u21, c.PARDES_KEY_BACKSPACE), pardes.Key.backspace);
+    try expectEqual(@as(u21, c.PARDES_KEY_UP), pardes.Key.up);
+    try expectEqual(@as(u21, c.PARDES_KEY_DOWN), pardes.Key.down);
+    try expectEqual(@as(u21, c.PARDES_KEY_LEFT), pardes.Key.left);
+    try expectEqual(@as(u21, c.PARDES_KEY_RIGHT), pardes.Key.right);
+    try expectEqual(@as(u21, c.PARDES_KEY_HOME), pardes.Key.home);
+    try expectEqual(@as(u21, c.PARDES_KEY_END), pardes.Key.end);
+    try expectEqual(@as(u21, c.PARDES_KEY_PAGE_UP), pardes.Key.page_up);
+    try expectEqual(@as(u21, c.PARDES_KEY_PAGE_DOWN), pardes.Key.page_down);
+    try expectEqual(@as(u21, c.PARDES_KEY_DELETE), pardes.Key.delete);
+
+    // The mouse ordinals the switch in pardes_mouse decodes are the enum's own
+    // declaration order; a reorder there is a silent remap of acme's buttons.
+    try expectEqual(c.PARDES_MOUSE_LEFT, @intFromEnum(pardes.Mouse.Button.left));
+    try expectEqual(c.PARDES_MOUSE_MIDDLE, @intFromEnum(pardes.Mouse.Button.middle));
+    try expectEqual(c.PARDES_MOUSE_RIGHT, @intFromEnum(pardes.Mouse.Button.right));
+    try expectEqual(c.PARDES_MOUSE_WHEEL_UP, @intFromEnum(pardes.Mouse.Button.wheel_up));
+    try expectEqual(c.PARDES_MOUSE_WHEEL_DOWN, @intFromEnum(pardes.Mouse.Button.wheel_down));
+    try expectEqual(c.PARDES_MOUSE_WHEEL_LEFT, @intFromEnum(pardes.Mouse.Button.wheel_left));
+    try expectEqual(c.PARDES_MOUSE_WHEEL_RIGHT, @intFromEnum(pardes.Mouse.Button.wheel_right));
+    try expectEqual(c.PARDES_MOUSE_NONE, @intFromEnum(pardes.Mouse.Button.none));
+    try expectEqual(c.PARDES_MOUSE_PRESS, @intFromEnum(pardes.Mouse.Kind.press));
+    try expectEqual(c.PARDES_MOUSE_RELEASE, @intFromEnum(pardes.Mouse.Kind.release));
+    try expectEqual(c.PARDES_MOUSE_MOTION, @intFromEnum(pardes.Mouse.Kind.motion));
+    try expectEqual(c.PARDES_MOUSE_DRAG, @intFromEnum(pardes.Mouse.Kind.drag));
+
+    // The attribute bits the host decodes, against the encoder that writes them.
+    try expectEqual(@as(u16, c.PARDES_ATTR_BOLD), encodeAttrs(.{ .bold = true }));
+    try expectEqual(@as(u16, c.PARDES_ATTR_DIM), encodeAttrs(.{ .dim = true }));
+    try expectEqual(@as(u16, c.PARDES_ATTR_ITALIC), encodeAttrs(.{ .italic = true }));
+    try expectEqual(@as(u16, c.PARDES_ATTR_BLINK), encodeAttrs(.{ .blink = true }));
+    try expectEqual(@as(u16, c.PARDES_ATTR_REVERSE), encodeAttrs(.{ .reverse = true }));
+    try expectEqual(@as(u16, c.PARDES_ATTR_INVISIBLE), encodeAttrs(.{ .invisible = true }));
+    try expectEqual(@as(u16, c.PARDES_ATTR_STRIKETHROUGH), encodeAttrs(.{ .strikethrough = true }));
+    try expectEqual(
+        @as(u16, c.PARDES_UL_CURLY) << c.PARDES_ATTR_UL_SHIFT,
+        encodeAttrs(.{ .ul = .curly }),
+    );
+}
+
+test "colors encode to the three tags the host decodes" {
+    const expectEqual = std.testing.expectEqual;
+    try expectEqual(@as(u32, 0x01000000), encodeColor(.default));
+    try expectEqual(@as(u32, 0x02000021), encodeColor(.{ .index = 33 }));
+    try expectEqual(@as(u32, 0x00112233), encodeColor(.{ .rgb = .{ 0x11, 0x22, 0x33 } }));
+}
+
+test "sub-row scroll spends whole notches and keeps the remainder" {
+    const expectEqual = std.testing.expectEqual;
+    var lag: f32 = 0;
+    // Four quarter-row flicks are one row, and not before the fourth.
+    try expectEqual(@as(i32, 0), takeScrollTicks(&lag, 0.25));
+    try expectEqual(@as(i32, 0), takeScrollTicks(&lag, 0.25));
+    try expectEqual(@as(i32, 0), takeScrollTicks(&lag, 0.25));
+    try expectEqual(@as(i32, 1), takeScrollTicks(&lag, 0.25));
+    try expectEqual(@as(f32, 0), lag);
+
+    // Direction reverses without the accumulated travel leaking across it.
+    try expectEqual(@as(i32, -2), takeScrollTicks(&lag, -2.5));
+    try expectEqual(@as(i32, 0), takeScrollTicks(&lag, 0.25));
+
+    // Garbage moves nothing and leaves the accumulator usable; a fling far
+    // past the clamp spends at most one screen and does not spin the caller.
+    lag = 0;
+    try expectEqual(@as(i32, 0), takeScrollTicks(&lag, std.math.nan(f32)));
+    try expectEqual(@as(i32, 0), takeScrollTicks(&lag, std.math.inf(f32)));
+    try expectEqual(@as(f32, 0), lag);
+    try expectEqual(@as(i32, 256), takeScrollTicks(&lag, 1e9));
+}
diff --git a/src/macos/Info.plist b/src/macos/Info.plist
new file mode 100644
index 00000000..9e8f65f7
--- /dev/null
+++ b/src/macos/Info.plist
@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>CFBundleName</key>
+	<string>pardes</string>
+	<key>CFBundleIdentifier</key>
+	<string>cafe.0x4200.pardes</string>
+	<key>CFBundleExecutable</key>
+	<string>pardes</string>
+	<key>CFBundlePackageType</key>
+	<string>APPL</string>
+	<key>NSHighResolutionCapable</key>
+	<true/>
+	<key>LSMinimumSystemVersion</key>
+	<string>13.0</string>
+	<key>NSPrincipalClass</key>
+	<string>NSApplication</string>
+</dict>
+</plist>
diff --git a/src/macos/Sources/AppDelegate.swift b/src/macos/Sources/AppDelegate.swift
new file mode 100644
index 00000000..4df5899c
--- /dev/null
+++ b/src/macos/Sources/AppDelegate.swift
@@ -0,0 +1,179 @@
+import AppKit
+
+// The macOS host: one window, one view, one core. libpardes owns the state
+// machine, the ptys and every worker thread; this file owns the window and the
+// pump that lets the core move at all.
+//
+// PardesView translates events and calls pardes_key / pardes_mouse /
+// pardes_scroll itself, but never pardes_tick — the core only queues what it
+// was told and does nothing until it is pumped. Rather than grow the view's
+// delegate a third method for "I just fed the core", the view posts this
+// notification after every input call and we answer it with pump(). The string
+// below is the whole contract with PardesView.swift; keep the two in step.
+private let didInputNotification = Notification.Name("pardesDidInput")
+
+final class AppDelegate: NSObject, NSApplicationDelegate, PardesViewDelegate {
+    private var window: NSWindow!
+    private var view: PardesView!
+    // One pump chain at a time. pump() re-arms itself while a theme transition
+    // is in flight and every input pumps as well, so without this a burst of
+    // keys during a fade would leave one 60 Hz chain per keystroke, all of them
+    // ticking until the fade ended.
+    private var pumpScheduled: Bool = false
+
+    func applicationDidFinishLaunching(_ notification: Notification) {
+        // ponytail: 14pt, fixed. The SDL shell steps its font on Ctrl+/Ctrl-
+        // (gui.zig); doing that here means re-measuring the view's metrics and
+        // pushing a resize behind it, so it waits until the font has to move.
+        view = PardesView(fontSize: 14)
+
+        let want = NSSize(width: 1000, height: 700)
+        window = NSWindow(
+            contentRect: NSRect(origin: .zero, size: want),
+            styleMask: [.titled, .closable, .miniaturizable, .resizable],
+            backing: .buffered,
+            defer: false)
+        window.title = "pardes"
+        // We hold this window strongly for the life of the app. Leaving
+        // isReleasedWhenClosed on would have AppKit release it out from under
+        // that reference the moment the close button is pressed.
+        window.isReleasedWhenClosed = false
+        window.contentView = view
+
+        // Trim the content box down to whole cells: a partial column or row is
+        // dead space the core can never draw into.
+        //
+        // ponytail: snapped once, at launch — a live drag lands wherever the
+        // mouse lets go. window.contentResizeIncrements would snap every
+        // resize, at the price of arguing with macOS full-screen tiling.
+        window.setContentSize(NSSize(
+            width: (want.width / view.cellWidth).rounded(.down) * view.cellWidth,
+            height: (want.height / view.cellHeight).rounded(.down) * view.cellHeight))
+        window.center()
+        // On screen before pardes_init, so that the backingScaleFactor read
+        // when seeding the cell metrics below is the one of the screen the
+        // window actually landed on. Drawing before the core exists costs an
+        // empty frame; metrics seeded at 1x would stay wrong forever, because
+        // a scale change moves no bounds and so fires no resize.
+        window.makeKeyAndOrderFront(nil)
+        // AppKit may promote a content view that accepts first responder on its
+        // own, but "may" is not something to bet every keystroke on, and there
+        // is no click-to-focus path here that would recover it.
+        window.makeFirstResponder(view)
+        // ponytail: no main menu, so no Cmd+Q — the close button and the core's
+        // Exit builtin are the two ways out. An NSMenu is ten lines, but the
+        // moment one exists it also has to decide which Cmd keys the core is
+        // allowed to see, and that is a real decision, not boilerplate.
+        //
+        // UNVERIFIED: activate(ignoringOtherApps:) is deprecated on the 14 SDK
+        // in favour of activate(), which does not exist at our 13.0 deployment
+        // target. Expect a deprecation warning, not an error.
+        NSApp.activate(ignoringOtherApps: true)
+
+        var runtime = pardes_runtime_s(
+            userdata: Unmanaged.passUnretained(self).toOpaque(),
+            wakeup: { ud in
+                // A pty reader thread. Every other function in pardes.h is
+                // main-thread-only, so this hop is the entire body — touching
+                // any core state here would be the race the hop exists to
+                // avoid.
+                let host = Unmanaged<AppDelegate>.fromOpaque(ud!).takeUnretainedValue()
+                DispatchQueue.main.async { host.pump() }
+            },
+            set_clipboard: { _, text, len in
+                // Main thread, from inside pardes_tick. `text` is borrowed for
+                // the length of the call, so the String has to be a copy.
+                var yank: String = ""
+                if let text = text, len > 0 {
+                    let bytes = UnsafeRawBufferPointer(start: UnsafeRawPointer(text), count: len)
+                    yank = String(decoding: bytes, as: UTF8.self)
+                }
+                let pasteboard = NSPasteboard.general
+                pasteboard.clearContents()
+                _ = pasteboard.setString(yank, forType: .string)
+            })
+
+        // The real grid, never a placeholder: the core holds each shell's
+        // greeting until it has seen a size, so a correction sent afterwards
+        // arrives with the first prompt already wrapped to the wrong width.
+        let grid = view.gridSize
+        let rc = pardes_init(&runtime, grid.cols, grid.rows)
+        if rc != 0 {
+            NSLog("pardes: the core failed to boot at \(grid.cols)x\(grid.rows), pardes_init returned \(rc)")
+            // Not NSApp.terminate — that runs applicationWillTerminate, which
+            // would call pardes_deinit on a core that never came up.
+            exit(1)
+        }
+
+        // Only now, after init. setContentSize above resized the view, and a
+        // pardesViewDidResize landing before pardes_init would have pushed a
+        // resize into a core that did not exist yet.
+        view.delegate = self
+        NotificationCenter.default.addObserver(
+            self, selector: #selector(inputArrived(_:)), name: didInputNotification, object: nil)
+
+        // pardes_init takes no cell metrics, so the core's PDF placement would
+        // have none until the user first dragged the window. This seeds them,
+        // and pumps. Repeating the size init just saw is safe by design: the
+        // core compares the effective pixel viewport, not the resize event, so
+        // duplicate SIGWINCH-shaped notifications are already a no-op.
+        pardesViewDidResize(view)
+    }
+
+    @objc private func inputArrived(_ notification: Notification) {
+        pump()
+    }
+
+    // Every path into the core ends here. pardes_tick drains the ptys and runs
+    // the effects the core queued, so nothing the user did takes hold until it
+    // runs.
+    private func pump() {
+        if pardes_tick() { view.needsDisplay = true }
+        if pardes_should_quit() {
+            NSApp.terminate(nil)
+            return
+        }
+        // A theme transition is the only thing that moves on its own, and it is
+        // ten 16 ms steps (animation.zig). Nothing else re-arms this, which is
+        // the point of an event-driven host: an idle pardes costs no CPU, where
+        // the SDL shell spins.
+        if pardes_animating() && !pumpScheduled {
+            pumpScheduled = true
+            DispatchQueue.main.asyncAfter(deadline: .now() + 0.016) {
+                self.pumpScheduled = false
+                self.pump()
+            }
+        }
+    }
+
+    func pardesViewDidResize(_ view: PardesView) {
+        let grid = view.gridSize
+        // cell_w/cell_h are physical pixels. The core hands them to the native
+        // PDF placement path, and a point is two pixels on a Retina display, so
+        // passing points would place every page at half size.
+        let scale: CGFloat = window.backingScaleFactor
+        pardes_resize(
+            grid.cols, grid.rows,
+            UInt16((view.cellWidth * scale).rounded()),
+            UInt16((view.cellHeight * scale).rounded()))
+        pump()
+    }
+
+    func pardesViewRequestsPaste(_ view: PardesView) {
+        guard let text = NSPasteboard.general.string(forType: .string) else { return }
+        // Swift lends a temporary NUL-terminated UTF-8 buffer for the duration
+        // of the call, which is exactly as long as the core borrows it.
+        pardes_paste(text, text.utf8.count)
+        pump()
+    }
+
+    // ponytail: one window, no tabs — the core has no multi-window notion, so
+    // the last window closing really is the end of the process.
+    func applicationShouldTerminateAfterLastWindowClosed(_ sender: NSApplication) -> Bool {
+        return true
+    }
+
+    func applicationWillTerminate(_ notification: Notification) {
+        pardes_deinit()
+    }
+}
diff --git a/src/macos/Sources/PardesView.swift b/src/macos/Sources/PardesView.swift
new file mode 100644
index 00000000..2dfa4305
--- /dev/null
+++ b/src/macos/Sources/PardesView.swift
@@ -0,0 +1,478 @@
+// The AppKit half of the macOS backend: NSEvent in, pardes_* out, one
+// CoreGraphics pass per frame back.
+//
+// This file keeps no model of the screen. The core owns the grid and hands it
+// over whole through src/macos/pardes.h, so everything here is translation, and
+// the only state worth holding is the font metrics — which are expensive to
+// measure and never change.
+//
+// Every C constant below is wrapped in an explicit conversion (UInt16(...),
+// UInt32(...)) rather than used bare. A macro's imported Swift type is decided
+// by the importer, not by us, and this file should not have an opinion about it.
+
+import AppKit
+import CoreText
+
+protocol PardesViewDelegate: AnyObject {
+    func pardesViewDidResize(_ view: PardesView)
+    func pardesViewRequestsPaste(_ view: PardesView)
+}
+
+// Matches bg_default/fg_default in src/gui/gui.zig and DEFAULT_FG/DEFAULT_BG in
+// src/web/app.mjs. Three shells render the same core; if these drift, comparing
+// a screenshot across backends stops meaning anything.
+private let defaultFG: UInt32 = 0xCC_CC_CC
+private let defaultBG: UInt32 = 0x12_12_12
+
+private let inputNotification = Notification.Name("pardesDidInput")
+
+// UNVERIFIED: kCTFontAttributeName bridged through NSAttributedString.Key. It is
+// the same string as .font, but spelling the CoreText key means the value stays
+// a CTFont instead of being bridged to NSFont on the way in.
+private let fontAttribute = NSAttributedString.Key(kCTFontAttributeName as String)
+
+// The named sixteen, then xterm's 6x6x6 cube, then the 24-step grey ramp. These
+// sixteen are app.mjs's, not gui.zig's: gui.zig borrows ghostty's palette
+// because it already links it, and the two disagree on the base colors.
+private let ansi16: [UInt32] = [
+    0x00_00_00, 0xCC_00_00, 0x4E_9A_06, 0xC4_A0_00,
+    0x34_65_A4, 0x75_50_7B, 0x06_98_9A, 0xD3_D7_CF,
+    0x55_57_53, 0xEF_29_29, 0x8A_E2_34, 0xFC_E9_4F,
+    0x72_9F_CF, 0xAD_7F_A8, 0x34_E2_E2, 0xEE_EE_EC,
+]
+
+private func paletteColor(_ index: UInt8) -> UInt32 {
+    if index < 16 { return ansi16[Int(index)] }
+    if index >= 232 {
+        let grey = UInt32(8 + (Int(index) - 232) * 10)
+        return grey << 16 | grey << 8 | grey
+    }
+    let n = Int(index) - 16
+    func level(_ part: Int) -> UInt32 { part == 0 ? 0 : UInt32(55 + part * 40) }
+    return level(n / 36) << 16 | level(n / 6 % 6) << 8 | level(n % 6)
+}
+
+private func decodeColor(_ encoded: UInt32, _ fallback: UInt32) -> UInt32 {
+    if encoded == UInt32(PARDES_COLOR_DEFAULT) { return fallback }
+    if encoded & UInt32(PARDES_COLOR_TAG_MASK) == UInt32(PARDES_COLOR_INDEXED) {
+        return paletteColor(UInt8(encoded & 0xFF))
+    }
+    return encoded & UInt32(PARDES_COLOR_RGB_MASK)
+}
+
+/// `block` means the filled cursor sits on this cell.
+private func resolve(
+    _ cell: pardes_cell_s,
+    block: Bool
+) -> (fg: UInt32, bg: UInt32, alpha: CGFloat, visible: Bool) {
+    // The core never painted this cell, which is most of the screen most of the
+    // time, so this branch is the one that has to stay cheap.
+    if cell.flags & UInt8(PARDES_CELL_DEFAULT) != 0 {
+        return block ? (defaultBG, defaultFG, 1, false) : (defaultFG, defaultBG, 1, false)
+    }
+    var fg = decodeColor(cell.fg, defaultFG)
+    var bg = decodeColor(cell.bg, defaultBG)
+    // The block cursor is a second reverse, so a cell that is already reversed
+    // cancels back to normal underneath it. Same rule as emitInstance in
+    // src/gui/gui.zig; the two must not drift.
+    var reverse = block
+    if cell.attrs & UInt16(PARDES_ATTR_REVERSE) != 0 { reverse = !reverse }
+    if reverse { swap(&fg, &bg) }
+    // ponytail: PARDES_ATTR_BLINK is decoded into nothing. Honouring it costs a
+    // timer plus a repaint budget for a bit nothing in pardes emits today; drive
+    // setNeedsDisplay from an NSTimer here when something does.
+    let visible = cell.attrs & UInt16(PARDES_ATTR_INVISIBLE) == 0 && cell.len > 0
+    // The other shells scale the channels by 6/10. Over a dark background alpha
+    // lands in the same place and costs one blend instead of three multiplies.
+    let alpha: CGFloat = cell.attrs & UInt16(PARDES_ATTR_DIM) != 0 ? 0.6 : 1
+    return (fg, bg, alpha, visible)
+}
+
+private func advance(_ font: CTFont, _ character: UniChar) -> CGFloat {
+    var input = character
+    var glyph = CGGlyph(0)
+    guard CTFontGetGlyphsForCharacters(font, &input, &glyph, 1) else { return 0 }
+    var size = CGSize.zero
+    CTFontGetAdvancesForGlyphs(font, .horizontal, &glyph, &size, 1)
+    return size.width
+}
+
+private func modifiers(_ flags: NSEvent.ModifierFlags) -> UInt32 {
+    var mods: UInt32 = 0
+    if flags.contains(.control) { mods |= UInt32(PARDES_MOD_CTRL) }
+    if flags.contains(.option) { mods |= UInt32(PARDES_MOD_ALT) }
+    if flags.contains(.shift) { mods |= UInt32(PARDES_MOD_SHIFT) }
+    return mods
+}
+
+final class PardesView: NSView {
+    let cellWidth: CGFloat
+    let cellHeight: CGFloat
+    weak var delegate: PardesViewDelegate?
+
+    private let regular: CTFont
+    private let bold: CTFont
+    private let italic: CTFont
+    private let boldItalic: CTFont
+    private let ascent: CGFloat
+    private let ruleThickness: CGFloat
+    private let underlineOffset: CGFloat
+    private var reportedCols: UInt16 = 0
+    private var reportedRows: UInt16 = 0
+
+    init(fontSize: CGFloat) {
+        let system = NSFont.monospacedSystemFont(ofSize: fontSize, weight: .regular)
+        var face = CTFontCreateWithName(system.fontName as CFString, fontSize, nil)
+        // The whole layout is a fixed grid, so a proportional face is not a
+        // cosmetic problem, it is a broken screen. Resolving the system monospace
+        // font by name is a lookup that can miss; "M" and "i" disagreeing on
+        // advance is the cheapest possible proof that it did.
+        let em = advance(face, 0x4D)
+        if em <= 0 || abs(em - advance(face, 0x69)) > 0.01 {
+            face = CTFontCreateWithName("Menlo" as CFString, fontSize, nil)
+        }
+
+        // UNVERIFIED: CTFontSymbolicTraits member spelling (.traitBold/.traitItalic).
+        // A face with no italic cut returns nil here, hence the fallback to `face`.
+        func variant(_ traits: CTFontSymbolicTraits) -> CTFont {
+            CTFontCreateCopyWithSymbolicTraits(face, fontSize, nil, traits, traits) ?? face
+        }
+        regular = face
+        bold = variant(.traitBold)
+        italic = variant(.traitItalic)
+        boldItalic = variant([.traitBold, .traitItalic])
+
+        cellWidth = max(1, advance(face, 0x4D))
+        ascent = CTFontGetAscent(face)
+        cellHeight = max(1, (ascent + CTFontGetDescent(face) + CTFontGetLeading(face)).rounded(.up))
+        ruleThickness = max(1, CTFontGetUnderlineThickness(face))
+        underlineOffset = CTFontGetUnderlinePosition(face)
+
+        // 80x24 only so the window has a size to open at; the AppDelegate reads
+        // gridSize back and boots the core with whatever it actually got.
+        super.init(frame: NSRect(x: 0, y: 0, width: cellWidth * 80, height: cellHeight * 24))
+    }
+
+    required init?(coder: NSCoder) { fatalError("PardesView is built in code, not a nib") }
+
+    // Row 0 at the top, so the drawing arithmetic reads like the grid it is.
+    override var isFlipped: Bool { true }
+    override var isOpaque: Bool { true }
+    override var acceptsFirstResponder: Bool { true }
+
+    var gridSize: (cols: UInt16, rows: UInt16) {
+        let cols = min(max((bounds.width / cellWidth).rounded(.down), 1), CGFloat(UInt16.max))
+        let rows = min(max((bounds.height / cellHeight).rounded(.down), 1), CGFloat(UInt16.max))
+        return (UInt16(cols), UInt16(rows))
+    }
+
+    // MARK: - drawing
+
+    override func draw(_ dirtyRect: NSRect) {
+        guard let ctx = NSGraphicsContext.current?.cgContext else { return }
+        // ponytail: dirtyRect is ignored. pardes_frame() re-renders the whole grid
+        // whatever we do, so clipping would save fills and nothing else. Narrow
+        // the row loops to the dirty band if that ever shows up in a profile.
+        let count = pardes_frame()
+        let cols = Int(pardes_frame_cols())
+        let rows = Int(pardes_frame_rows())
+        fill(ctx, bounds, defaultBG, 1)
+        guard cols > 0, rows > 0, Int(count) == cols * rows, let cells = pardes_frame_cells() else { return }
+
+        // -1 when hidden, which never matches a real cell, so hidden and "bar, so
+        // not a block" collapse into the same comparison.
+        let bar = pardes_cursor_bar()
+        let blockX = bar ? -1 : Int(pardes_cursor_x())
+        let blockY = bar ? -1 : Int(pardes_cursor_y())
+
+        // Background first, batched into runs of equal color. A full redraw is
+        // 80x24 cells at the low end and per-cell fills are exactly what makes
+        // that feel slow. Antialiasing is off because touching rects share an
+        // edge, and blending that edge twice draws a visible seam.
+        ctx.setShouldAntialias(false)
+        for row in 0..<rows {
+            let base = row * cols
+            let y = CGFloat(row) * cellHeight
+            var start = 0
+            var color = resolve(cells[base], block: blockY == row && blockX == 0).bg
+            for col in 1...cols {
+                // A real color is 24 bits, so .max is a sentinel that cannot
+                // compare equal and therefore always flushes the last run.
+                let next: UInt32 = col == cols
+                    ? .max
+                    : resolve(cells[base + col], block: blockY == row && blockX == col).bg
+                if next == color { continue }
+                fill(ctx, CGRect(x: CGFloat(start) * cellWidth, y: y,
+                                 width: CGFloat(col - start) * cellWidth, height: cellHeight),
+                     color, 1)
+                start = col
+                color = next
+            }
+        }
+
+        // CTFontDrawGlyphs lays glyph outlines out with +y up, and isFlipped hands
+        // us a y-down CTM, so drawing text directly in view space renders every
+        // line mirrored. Un-flip once for the whole glyph pass and convert each
+        // baseline into it rather than fighting the text matrix per cell.
+        ctx.setShouldAntialias(true)
+        ctx.saveGState()
+        ctx.textMatrix = .identity
+        ctx.translateBy(x: 0, y: bounds.height)
+        ctx.scaleBy(x: 1, y: -1)
+        let height = bounds.height
+        for row in 0..<rows {
+            let base = row * cols
+            let baseline = height - (CGFloat(row) * cellHeight + ascent)
+            for col in 0..<cols {
+                let cell = cells[base + col]
+                if cell.flags & UInt8(PARDES_CELL_DEFAULT) != 0 { continue }
+                let style = resolve(cell, block: blockY == row && blockX == col)
+                drawCell(ctx, cell, style, x: CGFloat(col) * cellWidth, baseline: baseline)
+            }
+        }
+        ctx.restoreGState()
+
+        if bar {
+            let x = Int(pardes_cursor_x()), y = Int(pardes_cursor_y())
+            if x >= 0, y >= 0, x < cols, y < rows {
+                // gui.zig paints U+258F here. A rect is the same picture without
+                // asking the font for a glyph it may not carry.
+                let fg = resolve(cells[y * cols + x], block: false).fg
+                fill(ctx, CGRect(x: CGFloat(x) * cellWidth, y: CGFloat(y) * cellHeight,
+                                 width: max(1, cellWidth / 8), height: cellHeight), fg, 1)
+            }
+        }
+    }
+
+    private func drawCell(
+        _ ctx: CGContext,
+        _ cell: pardes_cell_s,
+        _ style: (fg: UInt32, bg: UInt32, alpha: CGFloat, visible: Bool),
+        x: CGFloat,
+        baseline: CGFloat
+    ) {
+        // Rules before the glyph, and independent of it: an underlined space is a
+        // real thing and so is an underlined invisible cell.
+        let underline = Int(cell.attrs >> PARDES_ATTR_UL_SHIFT) & 7
+        if underline != Int(PARDES_UL_OFF) {
+            let y = baseline + underlineOffset
+            fill(ctx, CGRect(x: x, y: y, width: cellWidth, height: ruleThickness), style.fg, style.alpha)
+            // ponytail: curly, dotted and dashed all come out solid; only double
+            // earns its second rule. ctx.setLineDash for two of them and a sine
+            // path for the third is the upgrade, once anyone notices.
+            if underline == Int(PARDES_UL_DOUBLE) {
+                fill(ctx, CGRect(x: x, y: y - ruleThickness * 2, width: cellWidth, height: ruleThickness),
+                     style.fg, style.alpha)
+            }
+        }
+        if cell.attrs & UInt16(PARDES_ATTR_STRIKETHROUGH) != 0 {
+            fill(ctx, CGRect(x: x, y: baseline + ascent * 0.3, width: cellWidth, height: ruleThickness),
+                 style.fg, style.alpha)
+        }
+        guard style.visible else { return }
+
+        // UNVERIFIED: withUnsafeBytes over an imported C fixed-size array, which
+        // Swift models as an 8-tuple. String(decoding:) substitutes U+FFFD rather
+        // than trapping, and the core has shipped invalid UTF-8 through here
+        // before — the renderer must not be the thing that dies over it. prefix
+        // clamps, so a bogus len cannot walk off the eight bytes either.
+        let text = withUnsafeBytes(of: cell.text) { raw in
+            String(decoding: raw.prefix(Int(cell.len)), as: UTF8.self)
+        }
+        guard !text.isEmpty, text != " " else { return }
+
+        let heavy = cell.attrs & UInt16(PARDES_ATTR_BOLD) != 0
+        let slanted = cell.attrs & UInt16(PARDES_ATTR_ITALIC) != 0
+        let font = heavy ? (slanted ? boldItalic : bold) : (slanted ? italic : regular)
+        setFill(ctx, style.fg, style.alpha)
+
+        // ponytail: no glyph cache — a cmap lookup per cell, and a whole CTLine
+        // for anything that is not one BMP scalar the face covers. A
+        // [UnicodeScalar: CGGlyph] map, then an atlas, is the upgrade path when a
+        // full redraw shows up in Instruments.
+        let units = text.utf16
+        if units.count == 1, var character = units.first {
+            var glyph = CGGlyph(0)
+            if CTFontGetGlyphsForCharacters(font, &character, &glyph, 1) {
+                var position = CGPoint(x: x, y: baseline)
+                CTFontDrawGlyphs(font, &glyph, &position, 1, ctx)
+                return
+            }
+        }
+        // Emoji, combining marks and anything the face is missing: CTLine finds a
+        // fallback font. The position is set explicitly per cell — this is a fixed
+        // grid, and letting CoreText advance across a row would drift off it.
+        let attributed = NSAttributedString(string: text, attributes: [fontAttribute: font])
+        ctx.textPosition = CGPoint(x: x, y: baseline)
+        CTLineDraw(CTLineCreateWithAttributedString(attributed as CFAttributedString), ctx)
+    }
+
+    private func setFill(_ ctx: CGContext, _ rgb: UInt32, _ alpha: CGFloat) {
+        ctx.setFillColor(red: CGFloat((rgb >> 16) & 0xFF) / 255,
+                         green: CGFloat((rgb >> 8) & 0xFF) / 255,
+                         blue: CGFloat(rgb & 0xFF) / 255,
+                         alpha: alpha)
+    }
+
+    private func fill(_ ctx: CGContext, _ rect: CGRect, _ rgb: UInt32, _ alpha: CGFloat) {
+        setFill(ctx, rgb, alpha)
+        ctx.fill(rect)
+    }
+
+    // MARK: - keyboard
+
+    override func keyDown(with event: NSEvent) {
+        let flags = event.modifierFlags
+        // The ABI has no super bit, so a Command chord cannot be expressed at all.
+        // Cmd-V is the paste the delegate owns; every other one is swallowed
+        // rather than delivered as the bare keystroke the core would insert.
+        if flags.contains(.command) {
+            if event.charactersIgnoringModifiers?.lowercased() == "v" {
+                delegate?.pardesViewRequestsPaste(self)
+            }
+            return
+        }
+
+        let control = flags.contains(.control)
+        let option = flags.contains(.option)
+        // With ctrl or option down, `characters` is already the composed result —
+        // Ctrl-A is U+0001, Option-A is "å". The core wants the base key and no
+        // text, which is what app.mjs does with the same two bits.
+        let composed = (control || option ? event.charactersIgnoringModifiers : event.characters) ?? ""
+        guard let scalar = composed.unicodeScalars.first else { return }
+
+        var codepoint = scalar.value
+        // 0xF700..0xF8FF is AppKit's private-use block for function keys. The nine
+        // the core names get translated; the rest (F1-F12, Insert, the keypad) are
+        // dropped, because passing one through paints a stray glyph.
+        // These constants come from an unnamed C enum, so which width Swift picks
+        // for them is not something this file should depend on: wrapping each in
+        // UInt32() compiles whether they import as Int, Int32 or UInt32.
+        if scalar.value >= 0xF700 && scalar.value <= 0xF8FF {
+            switch scalar.value {
+            case UInt32(NSUpArrowFunctionKey): codepoint = UInt32(PARDES_KEY_UP)
+            case UInt32(NSDownArrowFunctionKey): codepoint = UInt32(PARDES_KEY_DOWN)
+            case UInt32(NSLeftArrowFunctionKey): codepoint = UInt32(PARDES_KEY_LEFT)
+            case UInt32(NSRightArrowFunctionKey): codepoint = UInt32(PARDES_KEY_RIGHT)
+            case UInt32(NSHomeFunctionKey): codepoint = UInt32(PARDES_KEY_HOME)
+            case UInt32(NSEndFunctionKey): codepoint = UInt32(PARDES_KEY_END)
+            case UInt32(NSPageUpFunctionKey): codepoint = UInt32(PARDES_KEY_PAGE_UP)
+            case UInt32(NSPageDownFunctionKey): codepoint = UInt32(PARDES_KEY_PAGE_DOWN)
+            case UInt32(NSDeleteFunctionKey): codepoint = UInt32(PARDES_KEY_DELETE)
+            default: return
+            }
+        }
+
+        // Enter, Tab, Escape and Backspace already arrive as the ASCII controls the
+        // header names. Two keys do not: the keypad's Enter is U+0003 and Shift-Tab
+        // is U+0019, neither of which is in the function-key block above, so without
+        // this both reach the core as a control it has no binding for and do
+        // nothing. The browser shell resolves them from the DOM key name and this
+        // is what keeps the two hosts saying the same thing.
+        if codepoint == 0x03 { codepoint = UInt32(PARDES_KEY_ENTER) }
+        if codepoint == 0x19 { codepoint = UInt32(PARDES_KEY_TAB) }
+
+        // A control character is functional, and functional keys must not also
+        // carry text.
+        let functional = codepoint < 0x20 || codepoint == 0x7F || codepoint >= 0xF0000
+        let text = functional || control || option ? "" : composed
+        // The pointer is borrowed for the call and nowhere else, which is the only
+        // thing the header promises about it.
+        text.withCString { pardes_key(codepoint, $0, text.utf8.count, modifiers(flags)) }
+        NotificationCenter.default.post(name: inputNotification, object: self)
+    }
+
+    // MARK: - mouse
+
+    override func mouseDown(with event: NSEvent) { send(PARDES_MOUSE_LEFT, PARDES_MOUSE_PRESS, event) }
+    override func mouseUp(with event: NSEvent) { send(PARDES_MOUSE_LEFT, PARDES_MOUSE_RELEASE, event) }
+    override func mouseDragged(with event: NSEvent) { send(PARDES_MOUSE_LEFT, PARDES_MOUSE_DRAG, event) }
+    override func rightMouseDown(with event: NSEvent) { send(PARDES_MOUSE_RIGHT, PARDES_MOUSE_PRESS, event) }
+    override func rightMouseUp(with event: NSEvent) { send(PARDES_MOUSE_RIGHT, PARDES_MOUSE_RELEASE, event) }
+    override func rightMouseDragged(with event: NSEvent) { send(PARDES_MOUSE_RIGHT, PARDES_MOUSE_DRAG, event) }
+    // otherMouse covers button 2 and up. acme's vocabulary stops at three, so
+    // every one of them lands on middle rather than being invented into a fourth.
+    override func otherMouseDown(with event: NSEvent) { send(PARDES_MOUSE_MIDDLE, PARDES_MOUSE_PRESS, event) }
+    override func otherMouseUp(with event: NSEvent) { send(PARDES_MOUSE_MIDDLE, PARDES_MOUSE_RELEASE, event) }
+    override func otherMouseDragged(with event: NSEvent) { send(PARDES_MOUSE_MIDDLE, PARDES_MOUSE_DRAG, event) }
+    override func mouseMoved(with event: NSEvent) { send(PARDES_MOUSE_NONE, PARDES_MOUSE_MOTION, event) }
+
+    override func scrollWheel(with event: NSEvent) {
+        guard let at = cell(for: event) else { return }
+        if event.hasPreciseScrollingDeltas {
+            // The core scrolls a row at a time, so libpardes accumulates the
+            // sub-row travel and spends it as wheel presses — which is why the
+            // cell has to travel with the delta.
+            pardes_scroll(Float(-event.scrollingDeltaY / cellHeight), at.col, at.row)
+        } else if event.scrollingDeltaY != 0 {
+            // AppKit's sign is the opposite of the DOM's: positive deltaY means the
+            // content moved down, which is a scroll back through history.
+            let button = event.scrollingDeltaY > 0 ? PARDES_MOUSE_WHEEL_UP : PARDES_MOUSE_WHEEL_DOWN
+            pardes_mouse(button, PARDES_MOUSE_PRESS, at.col, at.row, modifiers(event.modifierFlags))
+        } else {
+            return
+        }
+        NotificationCenter.default.post(name: inputNotification, object: self)
+    }
+
+    private func send(_ button: pardes_mouse_button_e, _ kind: pardes_mouse_kind_e, _ event: NSEvent) {
+        guard let at = cell(for: event) else { return }
+        pardes_mouse(button, kind, at.col, at.row, modifiers(event.modifierFlags))
+        NotificationCenter.default.post(name: inputNotification, object: self)
+    }
+
+    private func cell(for event: NSEvent) -> (col: UInt16, row: UInt16)? {
+        // Clamp against the frame the core last rendered, not against our own
+        // metrics: a window that has been resized but not yet ticked would
+        // otherwise report a column the core has no cell for. Before the first
+        // frame there is no grid to point at and the event is meaningless.
+        let cols = Int(pardes_frame_cols())
+        let rows = Int(pardes_frame_rows())
+        guard cols > 0, rows > 0 else { return nil }
+        let point = convert(event.locationInWindow, from: nil)
+        let col = min(max(Int(point.x / cellWidth), 0), cols - 1)
+        let row = min(max(Int(point.y / cellHeight), 0), rows - 1)
+        return (UInt16(col), UInt16(row))
+    }
+
+    // MARK: - geometry
+
+    override func updateTrackingAreas() {
+        super.updateTrackingAreas()
+        for area in trackingAreas { removeTrackingArea(area) }
+        // .inVisibleRect keeps the area correct across resizes on its own, which
+        // is why the rect argument can be anything.
+        addTrackingArea(NSTrackingArea(rect: .zero,
+                                       options: [.mouseMoved, .inVisibleRect, .activeInKeyWindow],
+                                       owner: self,
+                                       userInfo: nil))
+    }
+
+    override func setFrameSize(_ newSize: NSSize) {
+        super.setFrameSize(newSize)
+        // AppKit resizes a view many times over one drag and almost all of those
+        // land inside the same cell. Only a changed grid is news, and the core
+        // reflows every pty on a resize, so the no-ops are not free.
+        let grid = gridSize
+        guard grid.cols != reportedCols || grid.rows != reportedRows else { return }
+        reportedCols = grid.cols
+        reportedRows = grid.rows
+        delegate?.pardesViewDidResize(self)
+    }
+
+    // Dragging the window between a Retina display and a 1x one changes the
+    // backing scale without moving a single bound, so setFrameSize above never
+    // fires and the physical cell metrics the core uses to place PDF pages stay
+    // at the old scale forever. This is the only notification of it. (Ghostty
+    // hooks the same one, and additionally re-fires from the window's
+    // didChangeScreen notification, which AppKit does not always pair with it.)
+    override func viewDidChangeBackingProperties() {
+        super.viewDidChangeBackingProperties()
+        delegate?.pardesViewDidResize(self)
+    }
+}
+
+// ponytail: no NSTextInputClient, so dead keys and IME composition never reach
+// the core — keyDown reads `characters` and that is the whole story. Adopting
+// the protocol and routing through interpretKeyEvents is the upgrade when
+// someone needs to type Japanese.
diff --git a/src/macos/Sources/main.swift b/src/macos/Sources/main.swift
new file mode 100644
index 00000000..6cb2646e
--- /dev/null
+++ b/src/macos/Sources/main.swift
@@ -0,0 +1,16 @@
+import AppKit
+
+// Ghostty's ordering lesson: whatever must exist before AppKit boots goes above
+// app.run(), because after that call the runloop owns this thread forever.
+// pardes has nothing in that class — the core cannot come up until there is a
+// window to measure, so pardes_init waits for applicationDidFinishLaunching.
+
+let app = NSApplication.shared
+app.setActivationPolicy(.regular)
+
+// NSApplication does not own its delegate. This is a global, so it lives as
+// long as the process does; the same line inside a function would not.
+let delegate = AppDelegate()
+app.delegate = delegate
+
+app.run()
diff --git a/src/macos/build-app.sh b/src/macos/build-app.sh
new file mode 100755
index 00000000..6734f8d3
--- /dev/null
+++ b/src/macos/build-app.sh
@@ -0,0 +1,45 @@
+#!/bin/sh
+# Assemble pardes.app from libpardes.a and the Swift sources. Run it through
+# `zig build macos-app -Dplatform=macos`, or by hand with the install prefix as
+# $1 once `zig build -Dplatform=macos` has produced the library.
+#
+# There is no Xcode project on purpose. An .app is a directory with a plist and
+# a binary in it, swiftc ships with the Command Line Tools, and a hand-written
+# pbxproj would be a second build system to keep in step for no gain at this
+# stage. What Xcode buys — an xcframework of universal slices, codesigning,
+# notarization, a DMG — is distribution machinery; see docs/macos.md for the
+# upgrade path when that day comes.
+set -eu
+
+root=$(cd "$(dirname "$0")/../.." && pwd)
+out=${1:-"$root/zig-out"}
+app="$out/pardes.app"
+lib="$out/lib/libpardes.a"
+
+[ -f "$lib" ] || { echo "missing $lib — run: zig build -Dplatform=macos" >&2; exit 1; }
+command -v swiftc >/dev/null || { echo "swiftc not found (needs macOS + Command Line Tools)" >&2; exit 1; }
+
+rm -rf "$app"
+mkdir -p "$app/Contents/MacOS" "$app/Contents/Resources"
+cp "$root/src/macos/Info.plist" "$app/Contents/Info.plist"
+
+# -import-objc-header rather than a module map: the header is consumed straight
+# from the source tree, so there is nothing to stage and nothing to keep in
+# sync. A module map is what an xcframework needs, and there isn't one.
+#
+# -lc++ because ghostty-vt pulls in simdutf and highway, which are C++. The Zig
+# side bundles compiler_rt/ubsan_rt into the archive (see build.zig), so the
+# C++ runtime is the only thing left for this link to supply.
+# -target is not optional. Without it swiftc uses the host triple, so
+# LC_BUILD_VERSION records whatever macOS built the thing and dyld refuses to
+# launch it on anything older — the Info.plist's LSMinimumSystemVersion is a
+# claim, not the enforcement. It is also what turns on the availability
+# diagnostics that catch a post-13 API before a user does.
+swiftc -O -target "$(uname -m)-apple-macos13.0" \
+	-import-objc-header "$root/src/macos/pardes.h" \
+	-o "$app/Contents/MacOS/pardes" \
+	"$root"/src/macos/Sources/*.swift \
+	"$lib" -lc++ \
+	-framework AppKit -framework CoreText -framework CoreGraphics
+
+echo "built $app"
diff --git a/src/macos/pardes.h b/src/macos/pardes.h
new file mode 100644
index 00000000..e0d6fa32
--- /dev/null
+++ b/src/macos/pardes.h
@@ -0,0 +1,204 @@
+// libpardes — the C ABI the macOS app links against.
+//
+// Hand-written, and kept honest by a test: build.zig translate-C's this file
+// into the unit-test build, and src/macos.zig asserts every constant and
+// struct layout below against the Zig side (ghostty's trick — see docs/macos.md).
+// Change nothing here without running `zig build unit-test -Dplatform=macos`.
+//
+// Division of labour, which is the whole design in two lines:
+//   Zig  owns the core, the ptys, every effect, and the worker threads.
+//   Swift owns NSApplication, the window, input translation, and drawing.
+//
+// There is exactly one core per process, so there are no handles: the state is
+// a file-scoped singleton, same as src/web.zig. Every function below must be
+// called from the main thread. The one exception is the `wakeup` callback,
+// which fires from a pty reader thread.
+
+#ifndef PARDES_H
+#define PARDES_H
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// ---------------------------------------------------------------- frame
+
+// One rendered cell. Mirrors pardes.Cell (src/pardes.zig) flattened for the
+// wire; the identical encoding is spelled a second time for the browser in
+// src/web.zig as WebCell.
+typedef struct {
+  // UTF-8 grapheme, `len` bytes. The core caps graphemes at seven bytes; the
+  // eighth is always zero so a debugger prints something sensible.
+  uint8_t text[8];
+  // 0x01000000            terminal default
+  // 0x02000000 | index    256-color palette entry
+  // 0x00RRGGBB            direct color
+  uint32_t fg;
+  uint32_t bg;
+  // bit 0 bold, 1 dim, 2 italic, 3 blink, 4 reverse, 5 invisible,
+  // 6 strikethrough; bits 8.. hold PARDES_UL_*.
+  uint16_t attrs;
+  uint8_t len;
+  // bit 0: the core never painted this cell — draw it as the default cell
+  // (background only), which is what makes a partial redraw cheap.
+  uint8_t flags;
+} pardes_cell_s;
+
+#define PARDES_COLOR_DEFAULT 0x01000000u
+#define PARDES_COLOR_INDEXED 0x02000000u
+#define PARDES_COLOR_TAG_MASK 0xff000000u
+#define PARDES_COLOR_RGB_MASK 0x00ffffffu
+
+#define PARDES_ATTR_BOLD 0x0001u
+#define PARDES_ATTR_DIM 0x0002u
+#define PARDES_ATTR_ITALIC 0x0004u
+#define PARDES_ATTR_BLINK 0x0008u
+#define PARDES_ATTR_REVERSE 0x0010u
+#define PARDES_ATTR_INVISIBLE 0x0020u
+#define PARDES_ATTR_STRIKETHROUGH 0x0040u
+#define PARDES_ATTR_UL_SHIFT 8
+// Literals rather than (1u << n): Swift's macro importer is dependable on a
+// plain integer and less so on an expression, and nothing here can compile the
+// Swift side to find out. The ABI guard asserts each value against the encoder.
+
+#define PARDES_UL_OFF 0
+#define PARDES_UL_SINGLE 1
+#define PARDES_UL_DOUBLE 2
+#define PARDES_UL_CURLY 3
+#define PARDES_UL_DOTTED 4
+#define PARDES_UL_DASHED 5
+
+#define PARDES_CELL_DEFAULT 0x01u
+
+// ---------------------------------------------------------------- input
+
+// Modifier bitmask shared by key and mouse events.
+#define PARDES_MOD_CTRL 0x0001u
+#define PARDES_MOD_ALT 0x0002u
+#define PARDES_MOD_SHIFT 0x0004u
+
+// Keys that carry no text. The four editing keys are their ASCII controls;
+// everything else lives in a private-use plane so it can never collide with a
+// real codepoint arriving as text.
+#define PARDES_KEY_ENTER 0x0Du
+#define PARDES_KEY_ESCAPE 0x1Bu
+#define PARDES_KEY_TAB 0x09u
+#define PARDES_KEY_BACKSPACE 0x7Fu
+#define PARDES_KEY_UP 0xF0001u
+#define PARDES_KEY_DOWN 0xF0002u
+#define PARDES_KEY_LEFT 0xF0003u
+#define PARDES_KEY_RIGHT 0xF0004u
+#define PARDES_KEY_HOME 0xF0005u
+#define PARDES_KEY_END 0xF0006u
+#define PARDES_KEY_PAGE_UP 0xF0007u
+#define PARDES_KEY_PAGE_DOWN 0xF0008u
+#define PARDES_KEY_DELETE 0xF0009u
+
+// acme's three buttons carry the whole vocabulary: 1 selects, 2 executes,
+// 3 looks. Wheel buttons are ordinary buttons, not a separate axis.
+typedef enum {
+  PARDES_MOUSE_LEFT = 0,
+  PARDES_MOUSE_MIDDLE = 1,
+  PARDES_MOUSE_RIGHT = 2,
+  PARDES_MOUSE_WHEEL_UP = 3,
+  PARDES_MOUSE_WHEEL_DOWN = 4,
+  PARDES_MOUSE_WHEEL_LEFT = 5,
+  PARDES_MOUSE_WHEEL_RIGHT = 6,
+  PARDES_MOUSE_NONE = 7,
+} pardes_mouse_button_e;
+
+typedef enum {
+  PARDES_MOUSE_PRESS = 0,
+  PARDES_MOUSE_RELEASE = 1,
+  PARDES_MOUSE_MOTION = 2,
+  PARDES_MOUSE_DRAG = 3,
+} pardes_mouse_kind_e;
+
+// ---------------------------------------------------------------- runtime
+
+// What the host lends the core. Two callbacks, because everything else the
+// core wants done it already does itself: it owns the ptys, and it opens URLs
+// through /usr/bin/open. Copied by value during pardes_init, so the struct
+// need only outlive that call.
+typedef struct {
+  // Passed back to every callback below. Conventionally the AppDelegate.
+  void *userdata;
+
+  // "Your state moved; please pump me." Called from a pty reader thread, so
+  // the host must hop to the main thread before calling pardes_tick — see
+  // AppDelegate.wakeup, which does exactly one DispatchQueue.main.async.
+  void (*wakeup)(void *userdata);
+
+  // The yank register changed. `text` is borrowed for the duration of the
+  // call only. Main thread, inside pardes_tick.
+  void (*set_clipboard)(void *userdata, const char *text, size_t len);
+} pardes_runtime_s;
+
+// ---------------------------------------------------------------- lifecycle
+
+// Returns 0 on success, or a nonzero opaque error code. Pass the real window
+// grid, not a placeholder: init delivers it as the first resize EVENT (the
+// core defers each shell's greeting until it has seen one), and the first
+// forkpty takes its winsize straight off the core — boot at 80x24 and the
+// shell draws its first prompt to a width the window never had.
+int pardes_init(const pardes_runtime_s *runtime, uint16_t cols, uint16_t rows);
+void pardes_deinit(void);
+
+// Drain pty output into the core and perform the effects it queued. Call after
+// every input function and on every wakeup. Returns true if anything changed
+// and the host should mark its view dirty.
+bool pardes_tick(void);
+
+// The core asked to exit (the Exit builtin, or the last pane closing).
+bool pardes_should_quit(void);
+
+// A theme transition is mid-flight and wants ~60 Hz ticks until it settles.
+bool pardes_animating(void);
+
+// ---------------------------------------------------------------- events in
+
+// `cp` is a codepoint or one of PARDES_KEY_*; `text`/`len` are the host's
+// already-composed characters for printable keys and empty for functional
+// ones. `text` is borrowed for the call.
+void pardes_key(uint32_t cp, const char *text, size_t len, uint32_t mods);
+void pardes_paste(const char *text, size_t len);
+void pardes_mouse(pardes_mouse_button_e button, pardes_mouse_kind_e kind,
+                  uint16_t col, uint16_t row, uint32_t mods);
+
+// Trackpad/precision wheel distance in rows, sign following the grid (positive
+// scrolls down). The core has no fractional scroll — it moves a row at a time —
+// so libpardes accumulates here and emits whole-row wheel presses, keeping the
+// remainder. Both other shells do this same accumulation host-side (stepScroll
+// in gui.zig, the drain loop in web/app.mjs); it lives in Zig here so the Swift
+// side stays a translator. A discrete wheel notch should go through
+// pardes_mouse instead.
+void pardes_scroll(float delta_rows, uint16_t col, uint16_t row);
+
+// `cell_w`/`cell_h` are one cell in physical pixels, which only the native PDF
+// placement path reads. Pass the backing-store size, not points.
+void pardes_resize(uint16_t cols, uint16_t rows, uint16_t cell_w,
+                   uint16_t cell_h);
+
+// ---------------------------------------------------------------- frame out
+
+// Render one frame. Returns the cell count (cols * rows), or 0 on failure.
+// The buffer returned by pardes_frame_cells is valid until the next call.
+uint32_t pardes_frame(void);
+const pardes_cell_s *pardes_frame_cells(void);
+uint16_t pardes_frame_cols(void);
+uint16_t pardes_frame_rows(void);
+
+// -1 when the cursor is hidden. `bar` asks for a thin insert-mode caret.
+int32_t pardes_cursor_x(void);
+int32_t pardes_cursor_y(void);
+bool pardes_cursor_bar(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // PARDES_H
diff --git a/src/main.zig b/src/main.zig
index a3e7f862..343742e3 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -160,7 +160,10 @@ fn nativeMain(init: std.process.Init) !void {
     switch (pardes.platform) {
         .tty => try @import("tty/tty.zig").run(init, opts),
         .gui => try @import("gui/gui.zig").run(init, opts),
-        .web => unreachable, // web enters through webMain, never here
+        // Both library shells are entered by their host through a flat C ABI,
+        // and never link this file at all: the browser through src/web.zig,
+        // the macOS app through src/macos.zig.
+        .web, .macos => unreachable,
     }
 }
 
diff --git a/src/pardes.zig b/src/pardes.zig
index 08536544..5d0ff9fb 100644
--- a/src/pardes.zig
+++ b/src/pardes.zig
@@ -40,7 +40,7 @@ pub const image = @import("image.zig");
 pub const dump = @import("dump.zig");
 pub const lsp = @import("lsp/lsp.zig");
 
-pub const Platform = enum { tty, gui, web };
+pub const Platform = enum { tty, gui, web, macos };
 pub const platform: Platform = @field(Platform, @tagName(@import("pardes_config").platform));
 
 /// Native PDF quality is a shell property, but the core owns MuPDF and the
@@ -64,7 +64,9 @@ pub const sdl_pdf_raster_policy: PdfRasterPolicy = .{
 };
 pub const pdf_raster_policy: PdfRasterPolicy = switch (platform) {
     .tty => kitty_pdf_raster_policy,
-    .gui => sdl_pdf_raster_policy,
+    // Both pixel shells rasterize for a real display and can afford it; the
+    // wire-bandwidth argument that shapes the Kitty policy does not apply.
+    .gui, .macos => sdl_pdf_raster_policy,
     .web => kitty_pdf_raster_policy,
 };