fix(setup): install mlx-lm and mlx-audio in setup-python on Apple Silicon

[flowbrix]

Problem

On a fresh Apple Silicon dev setup, just setup installs backend/requirements-mlx.txt but not mlx-audio/mlx-lm themselves, so the Whisper MLX STT path is broken out of the box: POST /transcribe fails with No module named 'mlx_audio' (and, once that is installed, No module named 'mlx_lm').

These two packages are intentionally absent from requirements-mlx.txt because from mlx-audio 0.3.1 / mlx-lm 0.31.1 onward they declare transformers>=5.x, which conflicts with the transformers<=4.57.x cap in requirements.txt (see the existing note in backend/requirements-mlx.txt). The release workflow (.github/workflows/release.yml) already handles this by installing both with --no-deps — but the dev setup recipe never got the same treatment.

Fix

Mirror the release workflow in the Apple Silicon branch of the setup-python recipe ([unix] section; [windows] is unaffected since MLX is macOS-only):

• pip install --no-deps mlx-lm==0.31.1
• pip install --no-deps mlx-audio==0.4.1

with a comment explaining the --no-deps (transformers conflict), plus a pointer to the justfile in the requirements-mlx.txt note. Pins match release.yml so dev and CI stay in sync.

Verification

Ran just setup-python in a clean checkout (no pre-existing venv) on an Apple Silicon Mac — completed successfully, and:

$ backend/venv/bin/python -c "import mlx_audio, mlx_lm"   # OK
$ backend/venv/bin/python -c "import mlx_audio.stt, mlx_audio.tts"   # OK

with mlx-audio 0.4.1 / mlx-lm 0.31.1 resolved as pinned.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features
  • Expanded Apple Silicon (macOS arm64) MLX setup to include required audio and language packages.
• Documentation
  • Updated MLX installation guidance to reference additional setup instructions.
  • Clarified and reinforced installation reliability by pinning compatible MLX package versions during setup.
• Tests
  • Added a Darwin/Apple Silicon MLX smoke test to verify key MLX, audio (TTS/STT), and language (load/generate) entry points import and run.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 0d94b0a1-1643-431f-9e66-05c4a63f5431

📥 Commits

Reviewing files that changed from the base of the PR and between f23fca1 and bb0e990.

📒 Files selected for processing (1)

• backend/tests/test_mlx_smoke.py

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📝 Walkthrough

Walkthrough

The Apple Silicon setup-python recipe now installs pinned mlx-lm and mlx-audio packages with --no-deps. A Darwin arm64 smoke-test module validates MLX core, audio, and language-model entry points.

Changes

MLX setup and validation

Layer / File(s)	Summary
Pinned MLX installation justfile, backend/requirements-mlx.txt	The Apple Silicon setup installs mlx-lm==0.31.1 and mlx-audio==0.4.1 without dependencies, and the requirements comment references the setup-python recipe.
MLX runtime smoke tests backend/tests/test_mlx_smoke.py	Darwin arm64-only tests verify MLX core array execution and callable MLX audio TTS, STT, and language-model entry points.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related issues

• just setup-python doesn't install mlx-audio/mlx-lm — MLX backend fails on fresh Apple Silicon dev setup #823 — Covers adding the missing pinned MLX package installations and validating their entry points.

Possibly related PRs

• jamiepine/voicebox#482 — Uses the same pinned MLX packages and pip --no-deps installation approach.
• jamiepine/voicebox#506 — Addresses the miniaudio dependency implications of installing mlx-audio with --no-deps.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: installing mlx-lm and mlx-audio in setup-python for Apple Silicon.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

🧹 Nitpick comments (1)

justfile (1)

75-80: 🩺 Stability & Availability | 🔵 Trivial | ⚡ Quick win

Add an automated MLX smoke test. The --no-deps split is already documented, but backend/tests/test_qwen_download.py is a manual script and won’t run under pytest, so the mlx_audio import/download path still isn’t guarded in CI. Add a small smoke check for mlx_audio plus one TTS/STT path.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@justfile` around lines 75 - 80, The MLX installation commands lack an
automated CI smoke test for the mlx_audio import and runtime path. Add a
pytest-discoverable smoke test near the existing Qwen download test that imports
mlx_audio and exercises one TTS or STT operation, keeping the check small and
compatible with the installed MLX dependencies.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@justfile`:
- Around line 75-80: The MLX installation commands lack an automated CI smoke
test for the mlx_audio import and runtime path. Add a pytest-discoverable smoke
test near the existing Qwen download test that imports mlx_audio and exercises
one TTS or STT operation, keeping the check small and compatible with the
installed MLX dependencies.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 6e17eb7c-4edc-492c-acc1-752d3e2cbbf6

📥 Commits

Reviewing files that changed from the base of the PR and between f2cf2a7 and f23fca1.

📒 Files selected for processing (2)

• backend/requirements-mlx.txt
• justfile

[flowbrix]

Addressed the CodeRabbit nitpick: added backend/tests/test_mlx_smoke.py (bb0e990), a pytest-discoverable smoke test that runs under just test. It is skipped off Apple Silicon and covers the exact entry points the backend uses — mlx_audio.tts.load, mlx_audio.stt.load (which also exercises the miniaudio dep from #505), mlx_lm.load/generate, plus a basic mlx.core op. Verified locally on Apple Silicon: 4 passed.

🤖 Addressed by Claude Code