Pin Zig 0.17.0 and replace bufPrintZ

.github/workflows/test.yml

@@ -30,6 +30,19 @@ jobs:
           elixir-version: ${{ matrix.elixir }}
           otp-version: ${{ matrix.otp }}
 
+      # `:zig` tests (mob_nif.zig built for Android, MOB-226) need the pinned
+      # Zig; read it from .tool-versions so CI can't drift from it.
+      - name: Zig version from .tool-versions
+        id: zig
+        run: echo "version=$(awk '$1 == "zig" {print $2}' .tool-versions)" >> "$GITHUB_OUTPUT"
+
+      - uses: mlugg/setup-zig@v2
+        with:
+          version: ${{ steps.zig.outputs.version }}
+          # A cached .zig-cache holds configure results that name the zig
+          # binary by its absolute path, which changes every run.
+          use-cache: false
+
       - name: Cache deps + _build
         uses: actions/cache@v4
         with:
@@ -91,17 +104,28 @@ jobs:
             test/native/erts_dir_test.c \
             android/jni/mob_beam.h
 
-      - name: Android init-args tokenizer
+      - name: Zig version from .tool-versions
+        id: zig
+        run: echo "version=$(awk '$1 == "zig" {print $2}' .tool-versions)" >> "$GITHUB_OUTPUT"
+
+      - name: Set up Zig
         uses: mlugg/setup-zig@v2
         with:
-          version: 0.17.0-dev.269+ebff43698
+          version: ${{ steps.zig.outputs.version }}
+          # A cached .zig-cache holds configure results that name the zig
+          # binary by its absolute path, which changes every run.
+          use-cache: false
 
-      - name: Android init-args and ERTS-dir tests
+      - name: Android Zig unit tests (every file with `test` blocks)
         run: |
-          zig test android/jni/mob_init_args.zig
-          zig test android/jni/mob_erts_dir.zig
-
-      - name: Native harness (frame registry MOB-102/MOB-103, dist port MOB-139, dist cookie MOB-348, stored queue MOB-379, init args MOB-406, node host MOB-428, code versions MOB-408)
+          files=$(grep -lE '^\s*test( "|\s*\{)' android/jni/*.zig)
+          [ -n "$files" ] || { echo "no Zig test files found"; exit 1; }
+          for f in $files; do
+            echo "== zig test $f"
+            zig test "$f"
+          done
+
+      - name: Native harness (frame registry MOB-102/MOB-103, dist port MOB-139, dist cookie MOB-348, stored queue MOB-379, init args MOB-406, node host MOB-428, code versions MOB-408, ERTS dir MOB-493)
         # The frame-registry check is the only automated guard on the
         # element-frame registry's ownership, generation-gating and purge rules.
         # It reproduces the algorithm rather than linking ios/mob_nif.m (which

.tool-versions

@@ -1,3 +1,3 @@
 elixir 1.20.0-otp-29
 erlang 29.1.2
-zig 0.17.0-dev.269+ebff43698
+zig 0.17.0

CHANGELOG.md

@@ -10,7 +10,20 @@ Full module documentation: [hexdocs.pm/mob](https://hexdocs.pm/mob).
 
 ## [Unreleased]
 
+### Changed
+- **Zig pin is 0.17.0.** Replaces `0.17.0-dev.269+ebff43698`. That nightly
+  existed because 0.15.x could not link on the macOS 26 SDK; 0.17.0 is the
+  stable that has the fix (`build_system_migration.md`). `mix mob.doctor`
+  still requires an exact `zig version` match. Companion to mob_dev and
+  mob_new, which move with it.
+
 ### Fixed
+- **Android Zig sources compile on Zig 0.17.0.** `std.fmt.bufPrintZ` was
+  removed, so the post-mortem marker paths in `mob_nif.zig` use
+  `std.mem.printSentinel`, and `Allocator.dupeZ` was removed, so
+  `mob_stored_queue.zig`'s tests use `dupeSentinel`. CI now sets up the
+  pinned Zig from `.tool-versions`, compiles `mob_nif.zig` for Android and
+  runs every Android Zig test file.
 - **A task killed from outside right after `start_async/3` reports the real
   reason (MOB-500).** `Mob.Screen.Server` could pass `{:exit, :noproc}` to
   `handle_async/3` when the kill landed before the screen's monitor reached
@@ -19,6 +32,19 @@ Full module documentation: [hexdocs.pm/mob](https://hexdocs.pm/mob).
   for `Process.exit(pid, :kill)`). Seen once in a few thousand runs of
   `async_test.exs`, next to a test-side race on the same signal ordering.
 
+### Upgrading
+- **Zig 0.17.0, with mob_dev and mob_new's matching releases.** In each
+  app, set `zig 0.17.0` in `.tool-versions` (`mise use zig@0.17.0` installs
+  it and edits the file; `mise install zig@0.17.0` alone leaves the app on
+  the nightly). iOS apps also need `ios/build.zig` and
+  `ios/build_device.zig` off `b.build_root`, which 0.17.0 removed: in the
+  Swift glob, replace `b.build_root.handle.openDir(` with
+  `std.Io.Dir.openDirAbsolute(`, and add `b.dependOnDirectoryContents(.{
+  .cwd_relative = b.fmt("{s}/ios", .{mob_dir}) });` before it (0.17.0
+  caches the configure phase, so without it a new mob Swift file is missed).
+  Or copy the block from a freshly generated app. `mix mob.doctor` flags
+  both.
+
 ## [0.9.25] - 2026-10-22
 
 ### Security

android/jni/mob_nif.zig

@@ -4898,7 +4898,7 @@ const MARKER_FILENAME = "mob_post_mortem_appexit_marker.txt";
 // Registry then dedups within the current BEAM session.
 fn readMarker(dir: []const u8) i64 {
     var path_buf: [640]u8 = @splat(0);
-    const path = std.fmt.bufPrintZ(&path_buf, "{s}/{s}", .{ dir, MARKER_FILENAME }) catch return 0;
+    const path = std.mem.printSentinel(&path_buf, "{s}/{s}", .{ dir, MARKER_FILENAME }, 0) catch return 0;
 
     const f = jni.fopen(path.ptr, "rb") orelse return 0;
     defer _ = jni.fclose(f);
@@ -4928,7 +4928,7 @@ fn readMarker(dir: []const u8) i64 {
 // console on a permanently-failing path.
 fn writeMarker(dir: []const u8, ts_ms: i64) void {
     var path_buf: [640]u8 = @splat(0);
-    const path = std.fmt.bufPrintZ(&path_buf, "{s}/{s}", .{ dir, MARKER_FILENAME }) catch {
+    const path = std.mem.printSentinel(&path_buf, "{s}/{s}", .{ dir, MARKER_FILENAME }, 0) catch {
         logMarkerFailureOnce(.path_too_long);
         return;
     };
@@ -4941,7 +4941,7 @@ fn writeMarker(dir: []const u8, ts_ms: i64) void {
     defer _ = jni.close(fd);
 
     var out_buf: [32]u8 = @splat(0);
-    const out = std.fmt.bufPrintZ(&out_buf, "{d}\n", .{ts_ms}) catch {
+    const out = std.mem.printSentinel(&out_buf, "{d}\n", .{ts_ms}, 0) catch {
         logMarkerFailureOnce(.format_failed);
         return;
     };
@@ -4977,7 +4977,7 @@ fn logMarkerFailureOnce(kind: MarkerFailure) void {
     };
 
     var buf: [128]u8 = @splat(0);
-    const msg = std.fmt.bufPrintZ(&buf, "mob_post_mortem: marker write failed ({s}); cross-boot dedup will re-emit until this clears", .{reason}) catch return;
+    const msg = std.mem.printSentinel(&buf, "mob_post_mortem: marker write failed ({s}); cross-boot dedup will re-emit until this clears", .{reason}, 0) catch return;
     jni.logWrite(jni.ANDROID_LOG_ERROR, "MobNIF", "{s}", .{msg});
 }
 

android/jni/mob_stored_queue.zig

@@ -105,7 +105,7 @@ pub const StoredQueue = struct {
 const testing = std.testing;
 
 fn dup(s: []const u8) ![*:0]u8 {
-    return (try testing.allocator.dupeZ(u8, s)).ptr;
+    return (try testing.allocator.dupeSentinel(u8, s, 0)).ptr;
 }
 
 fn release(s: [*:0]u8) void {

build_system_migration.md

@@ -532,6 +532,11 @@ Apple framework module maps under -fmodules — Phase 1 finding).
     nightly has the fix; planning to switch to a zig stable that ships
     the macOS 26 fix when one is released (likely 0.17.0).
 
+  - 2026-10-22: Zig 0.17.0 is that stable. Pin across mob / mob_dev /
+    mob_new is `0.17.0`. `std.fmt.bufPrintZ` is gone (`std.mem.printSentinel`);
+    iOS templates open `{mob_dir}/ios` with `std.Io.Dir.openDirAbsolute`
+    because `Build.build_root` was removed.
+
   - iter 1: build.zig owns driver_tab_ios.c compile.
   - iter 2: + enif_keepalive.c compile.
   - iter 3: + 5 ObjC compiles via xcrun cc system commands

issues.md

@@ -1030,8 +1030,8 @@ landed should drop in cleanly:
 **Why** — `:zigler ~> 0.15` resolves to `zigler 0.15.2`, which targets a
 Zig stdlib snapshot from before the `@Type` builtin signature change
 and before `std.fs.File.stdout()` was removed. The installed Zig
-(currently `0.17.0-dev.269+ebff43698`, the version mob_dev builds with)
-is past both changes.
+(then `0.17.0-dev.269+ebff43698`, the version mob_dev built with; 0.17.0
+since 2026-10-22) is past both changes.
 
 The Elixir-side scaffolding itself is correct — it emits a clean
 `use Zig, otp_app: :app` module with an example `pub fn` in a `~Z`
@@ -1043,8 +1043,8 @@ sigil. The bug is only the version pin.
    tracks Zig 0.17-dev. If a newer zigler release is compatible, bump
    the version in `MobDev.AddNif.maybe_add_zigler_dep/2`.
 
-2. **Pin Zig instead.** Mob already pins a specific Zig version via
-   `~/zig/zig-aarch64-macos-0.17.0-dev.269+ebff43698/`. If zigler 0.15
+2. **Pin Zig instead.** Mob already pins a specific Zig version (then the
+   `0.17.0-dev.269+ebff43698` nightly, now 0.17.0). If zigler 0.15
    needs an earlier Zig, document the supported range, or vendor a
    second Zig install for the zigler path.
 

test/test_helper.exs

@@ -24,7 +24,7 @@
 {:ok, _} = Mob.ComponentRegistry.start_link()
 
 # `:zig` tests shell out to a real zig toolchain (MOB-226); skip where none is
-# installed (CI) rather than fail.
+# installed rather than fail. CI installs the pinned Zig, so they run there.
 zig_exclude = if System.find_executable("zig"), do: [], else: [:zig]
 
 ExUnit.start(exclude: [:onboarding, :on_device] ++ zig_exclude)