fix: made the macos app smaller

lib/bds/embeddings/backends/neural.ex

@@ -32,6 +32,11 @@ defmodule BDS.Embeddings.Backends.Neural do
     * Everywhere else — and as a fallback when EMLX is unavailable or explicitly
       disabled — it runs on optimised native CPU via XLA (`compiler: EXLA`).
 
+  Packaged releases contain only the backend that can run on their platform
+  (`runtime:` conditional deps in mix.exs): macOS releases ship EMLX and no
+  EXLA, Linux/Windows ship EXLA and no EMLX (MLX is Apple-only). The selected
+  backend is therefore started on demand here, never assumed at boot.
+
   The accelerator can be pinned with `config :bds, :embeddings, accelerator:`
   to `:auto` (default), `:emlx`, or `:exla`.
   """
@@ -171,7 +176,20 @@ defmodule BDS.Embeddings.Backends.Neural do
   @doc false
   @spec current_accelerator() :: :emlx | :exla
   def current_accelerator do
-    select_accelerator(configured_accelerator(), emlx_available?(), apple_silicon?())
+    case select_accelerator(
+           configured_accelerator(),
+           emlx_available?(),
+           exla_available?(),
+           apple_silicon?()
+         ) do
+      :none ->
+        raise RuntimeError,
+              "no embeddings accelerator available: neither the EMLX (Apple GPU) nor the " <>
+                "EXLA (CPU) application could be started on this machine"
+
+      accelerator ->
+        accelerator
+    end
   end
 
   @doc """
@@ -179,22 +197,43 @@ defmodule BDS.Embeddings.Backends.Neural do
 
   Prefer the Apple GPU (EMLX) under `:auto` only when it is both available and
   running on Apple Silicon; honour an explicit `:emlx`/`:exla` request, but
-  degrade a forced `:emlx` to EXLA when EMLX is not loaded so a misconfigured
-  host still gets working CPU inference instead of crashing.
+  degrade to the other backend when the requested one is not available so a
+  misconfigured host still gets working inference instead of crashing. Only
+  one backend ships per platform (macOS releases exclude EXLA, Linux/Windows
+  exclude EMLX), so the unavailable side is the norm in production, not an
+  edge case.
   """
-  @spec select_accelerator(:auto | :emlx | :exla, boolean(), boolean()) :: :emlx | :exla
-  def select_accelerator(:exla, _emlx_available?, _apple_silicon?), do: :exla
-  def select_accelerator(:emlx, true, _apple_silicon?), do: :emlx
-  def select_accelerator(:emlx, false, _apple_silicon?), do: :exla
-  def select_accelerator(:auto, true, true), do: :emlx
-  def select_accelerator(:auto, _emlx_available?, _apple_silicon?), do: :exla
+  @spec select_accelerator(:auto | :emlx | :exla, boolean(), boolean(), boolean()) ::
+          :emlx | :exla | :none
+  def select_accelerator(_configured, false, false, _apple_silicon?), do: :none
+  def select_accelerator(:exla, _emlx?, true, _apple_silicon?), do: :exla
+  def select_accelerator(:exla, true, false, _apple_silicon?), do: :emlx
+  def select_accelerator(:emlx, true, _exla?, _apple_silicon?), do: :emlx
+  def select_accelerator(:emlx, false, true, _apple_silicon?), do: :exla
+  def select_accelerator(:auto, true, _exla?, true), do: :emlx
+  def select_accelerator(:auto, _emlx?, true, _apple_silicon?), do: :exla
+  def select_accelerator(:auto, true, false, _apple_silicon?), do: :emlx
 
   defp configured_accelerator do
     config() |> Keyword.get(:accelerator, @default_accelerator)
   end
 
+  # The backend apps are runtime: false deps on the platforms that can't run
+  # them, so releases exclude one of them entirely and neither is auto-started
+  # in dev/test. Availability therefore means "the app actually starts here":
+  # ensure_all_started errors when the app is absent (or its NIF can't load).
+  # Starting the app is also exactly what the chosen backend needs before
+  # building the serving.
   defp emlx_available? do
-    Code.ensure_loaded?(EMLX) and Code.ensure_loaded?(EMLX.Backend)
+    started?(:emlx) and Code.ensure_loaded?(EMLX.Backend)
+  end
+
+  defp exla_available? do
+    started?(:exla)
+  end
+
+  defp started?(app) do
+    match?({:ok, _apps}, Application.ensure_all_started(app))
   end
 
   defp apple_silicon? do

lib/bds/mac_bundle.ex

@@ -70,6 +70,8 @@ defmodule BDS.MacBundle do
     frameworks = Path.join(contents, "Frameworks")
     rel = Path.join(resources, "rel")
 
+    # Validate before rm_rf! so a refused build leaves any previous bundle intact.
+    with :ok <- BDS.ReleasePackaging.validate_release_source(release_dir) do
       File.rm_rf!(app)
       Enum.each([macos, resources, frameworks], &File.mkdir_p!/1)
 
@@ -83,6 +85,7 @@ defmodule BDS.MacBundle do
         {:ok, app}
       end
     end
+  end
 
   # The main executable must be a real arm64 Mach-O, not a shell script — a
   # script has no Mach-O slices, so LaunchServices advertises x86_64 and offers

lib/bds/release_packaging.ex

@@ -56,7 +56,8 @@ defmodule BDS.ReleasePackaging do
     app_release_source = Keyword.fetch!(opts, :app_release_source)
     mcp_release_source = Keyword.fetch!(opts, :mcp_release_source)
 
-    with :ok <- reset_output(metadata),
+    with :ok <- validate_release_source(app_release_source),
+         :ok <- reset_output(metadata),
          :ok <- copy_release(app_release_source, metadata.app_root),
          :ok <- copy_release(mcp_release_source, metadata.resources_root),
          :ok <- write_manifest(metadata),
@@ -65,6 +66,20 @@ defmodule BDS.ReleasePackaging do
     end
   end
 
+  @doc """
+  Rejects half-assembled releases. A failed `mix release` run can leave `lib/`
+  copied but no `releases/<version>/` (no `env.sh`, no boot scripts) — packaging
+  that produces an app that dies on launch. Refuse it up front instead.
+  """
+  def validate_release_source(release_dir) do
+    if release_dir |> Path.join("releases/*/env.sh") |> Path.wildcard() == [] do
+      {:error,
+       {:incomplete_release, "#{release_dir} has no releases/*/env.sh — did `mix release` fail?"}}
+    else
+      :ok
+    end
+  end
+
   defp normalize_platform(platform) when platform in [:macos, :linux, :windows], do: platform
   defp normalize_platform(:darwin), do: :macos
 

mix.exs

@@ -62,11 +62,21 @@ defmodule BDS.MixProject do
       {:ex_ratatui, "~> 0.11"},
       {:image, "~> 0.67"},
       {:nx, "~> 0.10"},
-      {:exla, "~> 0.10"},
+      # Only one ML inference backend ships per platform; NIF releases are
+      # host-built, so the build OS is the target OS. EXLA (283 MB XLA CPU
+      # payload) never runs in the macOS app — EMLX always wins on Apple
+      # Silicon — but `runtime: false` alone can't exclude it there because
+      # the `image` dep declares exla as an optional application, which drags
+      # it into the release whenever it exists in the prod dep tree. Scoping
+      # it to dev/test on macOS keeps it fully out of macOS releases while
+      # Linux/Windows ship it as their production inference backend.
+      {:exla, "~> 0.10", if(macos?(), do: [only: [:dev, :test]], else: [])},
       # Apple Silicon GPU (Metal) acceleration for embedding inference. Ships
       # precompiled MLX binaries; the Neural backend prefers it on arm64 macOS
-      # and falls back to EXLA-CPU elsewhere (SPECGAPS A1-14c).
-      {:emlx, "~> 0.2.0"},
+      # and falls back to EXLA-CPU elsewhere (SPECGAPS A1-14c). Apple-only, so
+      # non-macOS releases exclude it (runtime: false deps stay out of
+      # releases — nothing pulls emlx in optionally, unlike exla above).
+      {:emlx, "~> 0.2.0", runtime: macos?()},
       {:bumblebee, "~> 0.6.3"},
       {:hnswlib, "~> 0.1.7"},
       {:stemex, "~> 0.2.1"},
@@ -121,4 +131,6 @@ defmodule BDS.MixProject do
       ]
     ]
   end
+
+  defp macos?, do: :os.type() == {:unix, :darwin}
 end

specs/embedding.allium

@@ -241,7 +241,12 @@ invariant NativeAcceleratedExecution {
     -- On Apple Silicon the model runs on the Apple GPU via EMLX (MLX/Metal,
     -- params placed on the EMLX.Backend GPU device); everywhere else, and as a
     -- fallback when EMLX is unavailable, it runs on optimised native CPU via
-    -- EXLA. Selection is `accelerator: :auto | :emlx | :exla` (default :auto).
+    -- EXLA. Selection is `accelerator: :auto | :emlx | :exla` (default :auto);
+    -- a request for an unavailable backend degrades to the other one.
+    -- Packaged releases ship only the backend their platform can run (runtime:
+    -- conditional deps): macOS releases exclude EXLA, Linux/Windows releases
+    -- exclude the Apple-only EMLX. The selected backend is started on demand
+    -- by the Neural backend, never assumed started at boot.
     -- Neighbour search is HNSW (hnswlib).
 }
 

test/bds/embeddings/backends/neural_test.exs

@@ -38,29 +38,45 @@ defmodule BDS.Embeddings.Backends.NeuralTest do
   end
 
   describe "accelerator selection (NativeAcceleratedExecution)" do
+    # select_accelerator(configured, emlx_available?, exla_available?, apple_silicon?)
     test "auto prefers Apple GPU (EMLX) when available on Apple Silicon" do
-      assert Neural.select_accelerator(:auto, true, true) == :emlx
+      assert Neural.select_accelerator(:auto, true, true, true) == :emlx
     end
 
     test "auto falls back to EXLA-CPU off Apple Silicon" do
-      assert Neural.select_accelerator(:auto, true, false) == :exla
+      assert Neural.select_accelerator(:auto, true, true, false) == :exla
     end
 
     test "auto falls back to EXLA-CPU when EMLX is unavailable" do
-      assert Neural.select_accelerator(:auto, false, true) == :exla
+      assert Neural.select_accelerator(:auto, false, true, true) == :exla
+    end
+
+    test "auto uses EMLX when EXLA is not shipped (pruned macOS bundle)" do
+      assert Neural.select_accelerator(:auto, true, false, true) == :emlx
+      assert Neural.select_accelerator(:auto, true, false, false) == :emlx
     end
 
     test "explicit :exla is honoured even on Apple Silicon with EMLX present" do
-      assert Neural.select_accelerator(:exla, true, true) == :exla
+      assert Neural.select_accelerator(:exla, true, true, true) == :exla
+    end
+
+    test "explicit :exla degrades to EMLX when EXLA is unavailable" do
+      assert Neural.select_accelerator(:exla, true, false, true) == :emlx
     end
 
     test "explicit :emlx is honoured when available" do
-      assert Neural.select_accelerator(:emlx, true, true) == :emlx
-      assert Neural.select_accelerator(:emlx, true, false) == :emlx
+      assert Neural.select_accelerator(:emlx, true, true, true) == :emlx
+      assert Neural.select_accelerator(:emlx, true, true, false) == :emlx
     end
 
     test "explicit :emlx degrades to EXLA when EMLX is unavailable" do
-      assert Neural.select_accelerator(:emlx, false, true) == :exla
+      assert Neural.select_accelerator(:emlx, false, true, true) == :exla
+    end
+
+    test "no accelerator available selects :none" do
+      assert Neural.select_accelerator(:auto, false, false, true) == :none
+      assert Neural.select_accelerator(:exla, false, false, false) == :none
+      assert Neural.select_accelerator(:emlx, false, false, false) == :none
     end
 
     test "defn options map each accelerator to its native compiler" do

test/bds/mac_bundle_test.exs

@@ -436,6 +436,8 @@ defmodule BDS.MacBundleTest do
       File.write!(Path.join(release, "bin/bds"), "#!/bin/sh\necho fake release\n")
       File.mkdir_p!(Path.join(release, "lib/wx-2.4/priv"))
       File.write!(Path.join(release, "lib/wx-2.4/priv/wxe_driver.so"), "fake-nif")
+      File.mkdir_p!(Path.join(release, "releases/0.1.0"))
+      File.write!(Path.join(release, "releases/0.1.0/env.sh"), "# env")
 
       icns = Path.join(tmp, "AppIcon.icns")
       File.write!(icns, "fake-icns")
@@ -489,5 +491,28 @@ defmodule BDS.MacBundleTest do
       assert File.exists?(Path.join(app, "Contents/Resources/rel/bin/bds"))
       assert File.exists?(Path.join(app, "Contents/Resources/AppIcon.icns"))
     end
+
+    test "refuses a half-assembled release and keeps the previous bundle", %{app: app} do
+      # A failed `mix release` leaves lib/ but no releases/<version>/env.sh.
+      tmp = Path.join(System.tmp_dir!(), "bds-macbundle-broken-#{System.unique_integer([:positive])}")
+      broken = Path.join(tmp, "rel")
+      File.mkdir_p!(Path.join(broken, "bin"))
+      File.mkdir_p!(Path.join(broken, "lib/wx-2.4/priv"))
+      on_exit(fn -> File.rm_rf!(tmp) end)
+
+      assert {:error, {:incomplete_release, message}} =
+               MacBundle.assemble(
+                 release_dir: broken,
+                 output_dir: Path.dirname(app),
+                 icns_path: Path.join(tmp, "missing.icns"),
+                 version: "0.1.0",
+                 skip_dylibs: true,
+                 skip_codesign: true
+               )
+
+      assert message =~ "mix release"
+      # the refused build must not have wiped the existing bundle
+      assert File.exists?(Path.join(app, "Contents/Resources/rel/bin/bds"))
+    end
   end
 end

test/bds/release_packaging_test.exs

@@ -15,6 +15,8 @@ defmodule BDS.ReleasePackagingTest do
     File.mkdir_p!(Path.join(mcp_release, "mcp/bin"))
     File.write!(Path.join(app_release, "bin/bds"), "app-release")
     File.write!(Path.join(mcp_release, "mcp/bin/bds-mcp"), "mcp-release")
+    File.mkdir_p!(Path.join(app_release, "releases/0.1.0"))
+    File.write!(Path.join(app_release, "releases/0.1.0/env.sh"), "# env")
 
     on_exit(fn -> File.rm_rf(base_dir) end)
 
@@ -66,6 +68,23 @@ defmodule BDS.ReleasePackagingTest do
            }
   end
 
+  test "package refuses a half-assembled release (no releases/*/env.sh)", context do
+    # A failed `mix release` can leave lib/ copied but no releases/<version>/;
+    # packaging that produces an app that dies on launch.
+    File.rm_rf!(Path.join(context.app_release, "releases"))
+
+    assert {:error, {:incomplete_release, message}} =
+             ReleasePackaging.package(
+               platform: :macos,
+               version: "0.1.0",
+               output_dir: context.output_dir,
+               app_release_source: context.app_release,
+               mcp_release_source: context.mcp_release
+             )
+
+    assert message =~ "mix release"
+  end
+
   test "package creates a platform archive for redistribution", context do
     assert {:ok, metadata} =
              ReleasePackaging.package(