From 7c2cbde4fa0f559d5dca65d90d3f2cc20014508c Mon Sep 17 00:00:00 2001
From: ashhart <71890694+ashhart@users.noreply.github.com>
Date: Sun, 1 Nov 2026 01:16:08 +0000
Subject: [PATCH] qwen3_5: the --drafter openers move to cuda_drafter_open.zig,
 so cuda_native.zig has room again

cuda_native.zig sat at exactly 600 lines after the shared-round pricing landed, so any change to it failed the
600-line rule (#1750). The DFlash2 and MTP openers, their reserve/close callbacks and the DFlash2 calibration move
unchanged; Opened and openDrafter are re-exported, so nothing else changes.
---
 .../families/qwen3_5/cuda_drafter_open.zig    | 91 +++++++++++++++++++
 zig/src/families/qwen3_5/cuda_native.zig      | 91 ++-----------------
 2 files changed, 97 insertions(+), 85 deletions(-)
 create mode 100644 zig/src/families/qwen3_5/cuda_drafter_open.zig

diff --git a/zig/src/families/qwen3_5/cuda_drafter_open.zig b/zig/src/families/qwen3_5/cuda_drafter_open.zig
new file mode 100644
index 0000000000..f96620d30b
--- /dev/null
+++ b/zig/src/families/qwen3_5/cuda_drafter_open.zig
@@ -0,0 +1,91 @@
+//! --drafter over the Qwen CUDA engine: a DFlash2 draft model, or the MoE target's own MTP layer.
+const std = @import("std");
+const lanes = @import("lanes");
+const native = @import("cuda_native.zig");
+const Draft = @import("cuda_draft.zig").Draft;
+const Mtp = @import("cuda_mtp.zig").Mtp;
+const draft_config = @import("cuda_draft_config.zig");
+const cost_adapter = native.cost_adapter;
+const Lanes = native.Lanes;
+
+/// A drafter opened over the engine; DFlash2's `prepare` times the target's windows once the pool is reserved.
+pub const Opened = struct {
+    drafter: lanes.drafter.Drafter,
+    ctx: *anyopaque,
+    close: *const fn (*anyopaque) void,
+    reserve: *const fn (*anyopaque, u32) anyerror!void,
+    prepare: ?struct { ctx: *anyopaque, run: *const fn (*anyopaque) anyerror!lanes.drafter.Facts, bytes: usize } = null,
+};
+
+/// --drafter's directory over engine `p`: a DFlash2 draft (its config's dflash_config), else the MoE's MTP layer.
+pub fn openDrafter(gpa: std.mem.Allocator, io: std.Io, p: *anyopaque, dir: []const u8, bits: u8) !Opened {
+    const l: *Lanes = @ptrCast(@alignCast(p));
+    if (!l.e.g.moe() or draft_config.declared(gpa, io, dir)) return openDFlash(gpa, io, p, dir, bits);
+    return openMtp(gpa, io, p, dir, bits);
+}
+
+/// The DFlash2 drafter in `dir` over engine `p`, 4-bit only, and the target's windows timed for the round loop.
+fn openDFlash(gpa: std.mem.Allocator, io: std.Io, p: *anyopaque, dir: []const u8, bits: u8) !Opened {
+    if (bits != 4) return error.DrafterBitsUnsupported;
+    const l: *Lanes = @ptrCast(@alignCast(p));
+    if (l.e.g.exl3 and l.e.g.moe()) return error.Exl3DrafterUnsupported; // a dense checkpoint drafts as an MLX one
+    if (l.caches.count() != 0 or l.pool.items.len != 0) return error.TapsAfterStreams;
+    const d = try Draft.init(gpa, io, l.e, dir);
+    errdefer d.deinit();
+    try l.e.setTaps(d.taps());
+    d.target_taps = l.e.tapBytes();
+    cost_adapter.identify(l, dir, .dflash);
+    l.calibration = d;
+    l.draft = d;
+    return .{ .drafter = d.drafter(), .ctx = d, .close = closeDrafter, .reserve = reserveDrafter, .prepare = .{ .ctx = l, .run = calibrateDrafter, .bytes = if (l.capacity < l.e.window_rows) try native.cacheBytes(l.e, l.e.window_rows, l.page_test) else 0 } };
+}
+
+/// The MTP layer beside the checkpoint in `dir` as the drafter over engine `p` (qwen3_5_moe), its ring the window.
+fn openMtp(gpa: std.mem.Allocator, io: std.Io, p: *anyopaque, dir: []const u8, bits: u8) !Opened {
+    if (bits != 4) return error.DrafterBitsUnsupported;
+    const l: *Lanes = @ptrCast(@alignCast(p));
+    if (l.e.g.exl3 and l.e.g.moe()) return error.Exl3DrafterUnsupported; // a dense checkpoint drafts as an MLX one
+    if (l.caches.count() != 0 or l.pool.items.len != 0) return error.TapsAfterStreams;
+    const d = try Mtp.init(gpa, io, l.e, dir, l.capacity);
+    errdefer d.deinit();
+    try l.e.setTaps(d.taps());
+    cost_adapter.identify(l, dir, .mtp);
+    try l.timeWindows(d, null);
+    l.mtp = d;
+    return .{ .drafter = d.drafter(), .ctx = d, .close = closeMtp, .reserve = reserveMtp };
+}
+
+fn reserveMtp(p: *anyopaque, streams: u32) anyerror!void {
+    const d: *Mtp = @ptrCast(@alignCast(p));
+    try d.reserve(streams);
+}
+
+fn closeMtp(p: *anyopaque) void {
+    const d: *Mtp = @ptrCast(@alignCast(p));
+    d.deinit();
+}
+
+fn calibrateDrafter(p: *anyopaque) !lanes.drafter.Facts {
+    const l: *Lanes = @ptrCast(@alignCast(p));
+    const d = l.calibration orelse return error.MissingCalibrationDrafter;
+    if (d.n_costs == 0) {
+        if (l.pool.items.len == 0) return error.MissingReservedQwenCache;
+        try l.timeWindows(d, l.pool.items[0]);
+    }
+    if (d.n_costs != l.e.window_rows) return error.IncompleteWindowMeasurements;
+    l.calibration = null;
+    var phases = l.startup;
+    phases.add(d.startup);
+    phases.print();
+    return d.drafter().facts();
+}
+
+fn reserveDrafter(p: *anyopaque, streams: u32) anyerror!void {
+    const d: *Draft = @ptrCast(@alignCast(p));
+    try d.reserve(streams);
+}
+
+fn closeDrafter(p: *anyopaque) void {
+    const d: *Draft = @ptrCast(@alignCast(p));
+    d.deinit();
+}
diff --git a/zig/src/families/qwen3_5/cuda_native.zig b/zig/src/families/qwen3_5/cuda_native.zig
index 1665dea3e2..f26bbf6e41 100644
--- a/zig/src/families/qwen3_5/cuda_native.zig
+++ b/zig/src/families/qwen3_5/cuda_native.zig
@@ -11,7 +11,6 @@ pub const cost_adapter = @import("cuda_cost_adapter.zig");
 const draws = @import("draw.zig");
 const Draft = @import("cuda_draft.zig").Draft;
 const cuda_rope = @import("cuda_rope.zig");
-const draft_config = @import("cuda_draft_config.zig");
 const prefill = @import("cuda_prefill.zig");
 const Fill = prefill.Fill;
 const reuse = @import("cuda_reuse.zig");
@@ -83,7 +82,7 @@ pub const Loaded = struct {
     all_on_pages: bool = false,
 };
 
-fn cacheBytes(e: *const E.Engine, cap: usize, test_tokens: usize) !usize {
+pub fn cacheBytes(e: *const E.Engine, cap: usize, test_tokens: usize) !usize {
     return std.math.add(usize, e.streamBytes(cap), try cache_mod.pageExtra(e.g, cap, test_tokens, e.kv8));
 }
 
@@ -191,87 +190,9 @@ fn reserve(p: *anyopaque, streams: u32) anyerror!void {
     const l: *Lanes = @ptrCast(@alignCast(p));
     try reservation.target(E.Cache, E.Part, l, streams); // with a pool: the first window, the shapes on its lanes
 }
-/// A drafter opened over the engine; DFlash2's `prepare` times the target's windows once the pool is reserved.
-pub const Opened = struct {
-    drafter: lanes.drafter.Drafter,
-    ctx: *anyopaque,
-    close: *const fn (*anyopaque) void,
-    reserve: *const fn (*anyopaque, u32) anyerror!void,
-    prepare: ?struct { ctx: *anyopaque, run: *const fn (*anyopaque) anyerror!lanes.drafter.Facts, bytes: usize } = null,
-};
-
-/// --drafter's directory over engine `p`: a DFlash2 draft (its config's dflash_config), else the MoE's MTP layer.
-pub fn openDrafter(gpa: std.mem.Allocator, io: std.Io, p: *anyopaque, dir: []const u8, bits: u8) !Opened {
-    const l: *Lanes = @ptrCast(@alignCast(p));
-    if (!l.e.g.moe() or draft_config.declared(gpa, io, dir)) return openDFlash(gpa, io, p, dir, bits);
-    return openMtp(gpa, io, p, dir, bits);
-}
-
-/// The DFlash2 drafter in `dir` over engine `p`, 4-bit only, and the target's windows timed for the round loop.
-fn openDFlash(gpa: std.mem.Allocator, io: std.Io, p: *anyopaque, dir: []const u8, bits: u8) !Opened {
-    if (bits != 4) return error.DrafterBitsUnsupported;
-    const l: *Lanes = @ptrCast(@alignCast(p));
-    if (l.e.g.exl3 and l.e.g.moe()) return error.Exl3DrafterUnsupported; // a dense checkpoint drafts as an MLX one
-    if (l.caches.count() != 0 or l.pool.items.len != 0) return error.TapsAfterStreams;
-    const d = try Draft.init(gpa, io, l.e, dir);
-    errdefer d.deinit();
-    try l.e.setTaps(d.taps());
-    d.target_taps = l.e.tapBytes();
-    cost_adapter.identify(l, dir, .dflash);
-    l.calibration = d;
-    l.draft = d;
-    return .{ .drafter = d.drafter(), .ctx = d, .close = closeDrafter, .reserve = reserveDrafter, .prepare = .{ .ctx = l, .run = calibrateDrafter, .bytes = if (l.capacity < l.e.window_rows) try cacheBytes(l.e, l.e.window_rows, l.page_test) else 0 } };
-}
-
-/// The MTP layer beside the checkpoint in `dir` as the drafter over engine `p` (qwen3_5_moe), its ring the window.
-fn openMtp(gpa: std.mem.Allocator, io: std.Io, p: *anyopaque, dir: []const u8, bits: u8) !Opened {
-    if (bits != 4) return error.DrafterBitsUnsupported;
-    const l: *Lanes = @ptrCast(@alignCast(p));
-    if (l.e.g.exl3 and l.e.g.moe()) return error.Exl3DrafterUnsupported; // a dense checkpoint drafts as an MLX one
-    if (l.caches.count() != 0 or l.pool.items.len != 0) return error.TapsAfterStreams;
-    const d = try Mtp.init(gpa, io, l.e, dir, l.capacity);
-    errdefer d.deinit();
-    try l.e.setTaps(d.taps());
-    cost_adapter.identify(l, dir, .mtp);
-    try l.timeWindows(d, null);
-    l.mtp = d;
-    return .{ .drafter = d.drafter(), .ctx = d, .close = closeMtp, .reserve = reserveMtp };
-}
-
-fn reserveMtp(p: *anyopaque, streams: u32) anyerror!void {
-    const d: *Mtp = @ptrCast(@alignCast(p));
-    try d.reserve(streams);
-}
-
-fn closeMtp(p: *anyopaque) void {
-    const d: *Mtp = @ptrCast(@alignCast(p));
-    d.deinit();
-}
-
-fn calibrateDrafter(p: *anyopaque) !lanes.drafter.Facts {
-    const l: *Lanes = @ptrCast(@alignCast(p));
-    const d = l.calibration orelse return error.MissingCalibrationDrafter;
-    if (d.n_costs == 0) {
-        if (l.pool.items.len == 0) return error.MissingReservedQwenCache;
-        try l.timeWindows(d, l.pool.items[0]);
-    }
-    if (d.n_costs != l.e.window_rows) return error.IncompleteWindowMeasurements;
-    l.calibration = null;
-    var phases = l.startup;
-    phases.add(d.startup);
-    phases.print();
-    return d.drafter().facts();
-}
-
-fn reserveDrafter(p: *anyopaque, streams: u32) anyerror!void {
-    const d: *Draft = @ptrCast(@alignCast(p));
-    try d.reserve(streams);
-}
-
-fn closeDrafter(p: *anyopaque) void {
-    const d: *Draft = @ptrCast(@alignCast(p));
-    d.deinit();
-}
+const drafter_open = @import("cuda_drafter_open.zig");
+pub const Opened = drafter_open.Opened;
+pub const openDrafter = drafter_open.openDrafter;
 
 /// A request this engine refuses, in words, or with no engine (null) its open; null: none of its own.
 pub fn explain(ctx: ?*anyopaque, err: anyerror) ?[]const u8 {
@@ -307,7 +228,7 @@ fn pick(sampling: ?lanes.Sampling, position: u64) E.Draw {
     return .{ .rule = cuda.sample.Rule.from(lanes.gpu_rule.rule(s)), .position = position };
 }
 
-const Lanes = struct {
+pub const Lanes = struct {
     timing_on: bool = false,
     trace: ?*round_timing.Trace = null,
     gpa: std.mem.Allocator,
@@ -398,7 +319,7 @@ const Lanes = struct {
     }
 
     /// Each width timed on a reset cache after its captured launch shape is warm.
-    fn timeWindows(self: *Lanes, d: anytype, reserved: ?*E.Cache) !void {
+    pub fn timeWindows(self: *Lanes, d: anytype, reserved: ?*E.Cache) !void {
         self.startup.add(try cost_adapter.measure(self, d, reserved));
     }