diff --git a/build.zig b/build.zig
index b5f1528..9882273 100644
--- a/build.zig
+++ b/build.zig
@@ -51,63 +51,6 @@ fn timestamp(b: *std.Build) []const u8 {
     });
 }
 
-/// One user-space binary via the shared build-support recipe (freestanding,
-/// ReleaseSmall, `.large` code model, root shim + user link script — see
-/// build-support/build.zig for the full story). The program's file becomes the
-/// `program` module; reach it through `programModule` to add per-binary imports.
-fn addUserBinary(
-    b: *std.Build,
-    target: std.Build.ResolvedTarget,
-    default_imports: []const std.Build.Module.Import,
-    name: []const u8,
-    root: []const u8,
-) *std.Build.Step.Compile {
-    return addUserBinaryImpl(b, target, default_imports, name, root, false);
-}
-
-/// As `addUserBinary`, but built multi-threaded (`single_threaded = false`) so real
-/// atomics/TLS work — required before a binary may call `Thread.spawn`
-/// (docs/threading.md). Threads are a deliberate per-binary opt-in.
-fn addThreadedUserBinary(
-    b: *std.Build,
-    target: std.Build.ResolvedTarget,
-    default_imports: []const std.Build.Module.Import,
-    name: []const u8,
-    root: []const u8,
-) *std.Build.Step.Compile {
-    return addUserBinaryImpl(b, target, default_imports, name, root, true);
-}
-
-fn addUserBinaryImpl(
-    b: *std.Build,
-    target: std.Build.ResolvedTarget,
-    default_imports: []const std.Build.Module.Import,
-    name: []const u8,
-    root: []const u8,
-    threaded: bool,
-) *std.Build.Step.Compile {
-    // The shim and link script live in the kernel domain package, so name them
-    // through it — the same spelling build-support's userBinary uses.
-    const kernel_library = b.dependency("kernel", .{});
-    return build_support.userBinaryFromImports(b, .{
-        .name = name,
-        .root_source_file = b.path(root),
-        .shim_source_file = kernel_library.path("root.zig"),
-        .linker_script = kernel_library.path("user.ld"),
-        .target = target,
-        .default_imports = default_imports,
-        .threaded = threaded,
-    });
-}
-
-/// The `program` module of a binary built by `addUserBinary` — the module rooted
-/// at the program's own source file. Per-binary imports (protocol modules, bus
-/// ABIs) go here, not on the root shim: module imports are not transitive, so an
-/// import added to the root would be invisible to the program's code.
-fn programModule(exe: *std.Build.Step.Compile) *std.Build.Module {
-    return build_support.programModule(exe);
-}
-
 /// The modules the kernel imports, gathered once so both kernel variants (the
 /// installed one and the serial-enabled one `run-x86-64` boots) are built from
 /// the same set. `build_options` is *not* here — it carries `serial`/`test_case`,
@@ -250,7 +193,6 @@ pub fn build(b: *std.Build) void {
     });
     const abi_module = kernel_library.module("abi");
     const device_abi_module = device_library.module("device-abi");
-    const pci_class_module = device_library.module("pci-class");
 
     // Kernel tunables (maximum_cpus, stack sizes, tick rate). A dependency-free module of
     // compile-time constants, imported wherever a knob is read; keeps the trade-offs
@@ -292,14 +234,7 @@ pub fn build(b: *std.Build) void {
         },
     });
 
-    // The wire protocols some test fixtures name as per-binary extras,
-    // exported by the protocol package.
-    const device_manager_protocol_module = protocol_library.module("device-manager-protocol");
 
-    // The driver-side PCI library some test fixtures name as a per-binary
-    // extra. (The rest of the domain modules reach the root only through
-    // build-support's defaultImports below.)
-    const pci_module = device_library.module("pci");
 
     // The initial_ramdisk container format, shared by the kernel (unpacks it) and
     // the EFI loader (packs it in RAM from the boot volume's /system tree). No
@@ -346,18 +281,7 @@ pub fn build(b: *std.Build) void {
     const kernel_install = b.addInstallArtifact(exe, .{ .dest_dir = .{ .override = .{ .custom = "system" } } });
     b.getInstallStep().dependOn(&kernel_install.step);
 
-    // --- init: the first user-space program (a system service) ---
-    // The default module set every user binary can import directly, drawn from
-    // build-support's single authoritative list so the root stanzas and the
-    // binary packages can never drift apart. Per-binary extras are added with
-    // programModule(exe).addImport.
-    const default_imports = build_support.defaultImports(.{
-        .kernel = kernel_library,
-        .device = device_library,
-        .client = client_library,
-        .xkeyboard_config = xkeyboard_config_library,
-    });
-
+    // --- the user-space binaries, every one of them a package ---
     // Binary packages (docs/build-packages-plan.md, phase 2): each binary
     // builds itself against the domain packages via build-support's shared
     // recipe, started in ring 3 by the kernel's user-ELF loader like always;
@@ -371,7 +295,7 @@ pub fn build(b: *std.Build) void {
     // Each is built by the same user-binary recipe and laid out at its FHS path on
     // the boot volume (see `bundled` below). The EFI loader walks the tree at boot
     // and hands the kernel an in-RAM initial_ramdisk of it (system/initial-ramdisk.zig).
-    const vfstest_exe = addUserBinary(b, kernel_target, &default_imports, "vfs-test", "test/system/services/vfs-test/vfs-test.zig");
+    const vfstest_exe = b.dependency("vfs-test", .{}).artifact("vfs-test");
     // The drivers, each directory its own package: the PS/2 bus family (bus +
     // keyboard + mouse from one package), the xHCI bus driver, the USB HID
     // class drivers, and USB mass storage. Their unit tests ride along.
@@ -394,29 +318,21 @@ pub fn build(b: *std.Build) void {
     const display_demo_exe = b.dependency("display-demo", .{}).artifact("display-demo");
     const virtio_gpu_package = b.dependency("virtio-gpu", .{});
     const virtio_gpu_exe = virtio_gpu_package.artifact("virtio-gpu");
-    const shared_memory_server_exe = addUserBinary(b, kernel_target, &default_imports, "shared-memory-server", "test/system/services/shared-memory-server/shared-memory-server.zig");
-    const shared_memory_client_exe = addUserBinary(b, kernel_target, &default_imports, "shared-memory-client", "test/system/services/shared-memory-client/shared-memory-client.zig");
-    const fat_test_exe = addUserBinary(b, kernel_target, &default_imports, "fat-test", "test/system/services/fat-test/fat-test.zig");
+    const shared_memory_server_exe = b.dependency("shared-memory-server", .{}).artifact("shared-memory-server");
+    const shared_memory_client_exe = b.dependency("shared-memory-client", .{}).artifact("shared-memory-client");
+    const fat_test_exe = b.dependency("fat-test", .{}).artifact("fat-test");
     // The first binary package (docs/build-packages-plan.md, phase 2): pci-bus
     // builds itself against the domain packages; the root build just takes the
     // artifact for the boot image.
     const pci_bus_exe = b.dependency("pci-bus", .{}).artifact("pci-bus");
-    // A test fixture, not a real driver: hellos to the device manager, then faults —
-    // what the driver-restart scenario drives the crash-loop cap with.
-    const crash_test_exe = addUserBinary(b, kernel_target, &default_imports, "crash-test", "test/system/services/crash-test/crash-test.zig");
-    programModule(crash_test_exe).addImport("device-manager-protocol", device_manager_protocol_module);
-    const device_list_exe = addUserBinary(b, kernel_target, &default_imports, "device-list", "test/system/services/device-list/device-list.zig");
-    programModule(device_list_exe).addImport("device-manager-protocol", device_manager_protocol_module);
-    // A test fixture: claims the pci-caps case's extra unclaimed NIC and exercises the
-    // driver-side PCI library surface (capabilities, MSI, MSI-X, power, FLR) against it.
-    const pci_cap_test_exe = addUserBinary(b, kernel_target, &default_imports, "pci-cap-test", "test/system/services/pci-cap-test/pci-cap-test.zig");
-    programModule(pci_cap_test_exe).addImport("pci", pci_module);
-    programModule(pci_cap_test_exe).addImport("pci-class", pci_class_module);
-    // The IOMMU-enforcement negative test: claims an unclaimed e1000e and fires a rogue
-    // DMA that VT-d must fault. Same PCI building blocks as pci-cap-test.
-    const iommu_fault_test_exe = addUserBinary(b, kernel_target, &default_imports, "iommu-fault-test", "test/system/services/iommu-fault-test/iommu-fault-test.zig");
-    programModule(iommu_fault_test_exe).addImport("pci", pci_module);
-    programModule(iommu_fault_test_exe).addImport("pci-class", pci_class_module);
+    // crash-test is a fixture, not a real driver: it hellos to the device
+    // manager, then faults — what the driver-restart scenario drives the
+    // crash-loop cap with. pci-cap-test and iommu-fault-test exercise the
+    // driver-side PCI library surface and the VT-d rogue-DMA negative proof.
+    const crash_test_exe = b.dependency("crash-test", .{}).artifact("crash-test");
+    const device_list_exe = b.dependency("device-list", .{}).artifact("device-list");
+    const pci_cap_test_exe = b.dependency("pci-cap-test", .{}).artifact("pci-cap-test");
+    const iommu_fault_test_exe = b.dependency("iommu-fault-test", .{}).artifact("iommu-fault-test");
     // The discovery service: one swappable process per firmware
     // (docs/discovery.md), bundled under the neutral ramdisk name
     // "discovery" so the device manager never learns which firmware it is on.
@@ -435,14 +351,14 @@ pub fn build(b: *std.Build) void {
     // The input service and its exercisers: the fan-out server, a hardware-free synthetic
     // source, and a subscriber that doubles as the `input` test's oracle. See docs/input.md.
     const input_exe = b.dependency("input", .{}).artifact("input");
-    const input_source_exe = addUserBinary(b, kernel_target, &default_imports, "input-source", "test/system/services/input-source/input-source.zig");
-    const input_test_exe = addUserBinary(b, kernel_target, &default_imports, "input-test", "test/system/services/input-test/input-test.zig");
-    const args_echo_exe = addUserBinary(b, kernel_target, &default_imports, "args-echo", "test/system/services/args-echo/args-echo.zig");
-    const process_test_exe = addUserBinary(b, kernel_target, &default_imports, "process-test", "test/system/services/process-test/process-test.zig");
+    const input_source_exe = b.dependency("input-source", .{}).artifact("input-source");
+    const input_test_exe = b.dependency("input-test", .{}).artifact("input-test");
+    const args_echo_exe = b.dependency("args-echo", .{}).artifact("args-echo");
+    const process_test_exe = b.dependency("process-test", .{}).artifact("process-test");
     const logger_exe = b.dependency("logger", .{}).artifact("logger");
     // The first multi-threaded binary: exercises runtime.Thread over the thread ABI
-    // (docs/threading.md). Built threaded so its shared-memory poll is real.
-    const thread_test_exe = addThreadedUserBinary(b, kernel_target, &default_imports, "thread-test", "test/system/services/thread-test/thread-test.zig");
+    // (docs/threading.md). Its package opts into threading (real atomics/TLS).
+    const thread_test_exe = b.dependency("thread-test", .{}).artifact("thread-test");
 
     // Every user binary and its FHS home on the boot volume. There is no packed
     // ramdisk artifact any more: make-fat-image.py lays each binary out at this
diff --git a/build.zig.zon b/build.zig.zon
index e75ac78..3f708cd 100644
--- a/build.zig.zon
+++ b/build.zig.zon
@@ -58,6 +58,19 @@
         .@"usb-hid" = .{ .path = "system/drivers/usb-hid" },
         .@"usb-storage" = .{ .path = "system/drivers/usb-storage" },
         .@"virtio-gpu" = .{ .path = "system/drivers/virtio-gpu" },
+        .@"vfs-test" = .{ .path = "test/system/services/vfs-test" },
+        .@"fat-test" = .{ .path = "test/system/services/fat-test" },
+        .@"shared-memory-server" = .{ .path = "test/system/services/shared-memory-server" },
+        .@"shared-memory-client" = .{ .path = "test/system/services/shared-memory-client" },
+        .@"crash-test" = .{ .path = "test/system/services/crash-test" },
+        .@"device-list" = .{ .path = "test/system/services/device-list" },
+        .@"pci-cap-test" = .{ .path = "test/system/services/pci-cap-test" },
+        .@"iommu-fault-test" = .{ .path = "test/system/services/iommu-fault-test" },
+        .@"input-source" = .{ .path = "test/system/services/input-source" },
+        .@"input-test" = .{ .path = "test/system/services/input-test" },
+        .@"args-echo" = .{ .path = "test/system/services/args-echo" },
+        .@"process-test" = .{ .path = "test/system/services/process-test" },
+        .@"thread-test" = .{ .path = "test/system/services/thread-test" },
         // See `zig fetch --save <url>` for a command-line interface for adding dependencies.
         //.example = .{
         //    // When updating this field to a new URL, be sure to delete the corresponding