CLAUDE.md

Project Guidelines — ACE Music Studio

Working notes for AI assistants editing this repo. This file is the what & why — the locked architecture, the gotchas, the sole-author rule. Companion to SKILLS.md (the how — process, debugging, deployment workflow) and AGENTS.md (tool-agnostic version of this file).

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⚠ Sole-author rule (non-negotiable)

Mayank Gupta is the sole author on every commit in this repo. No exceptions.

When committing:

• NO Co-Authored-By: Claude… (or any agent name) trailer.
• NO "Generated with Claude Code" / "🤖 Generated with…" footers.
• NO --author=… flag — let git use the user's configured identity.
• NO attribution in PR descriptions.

If asked to amend, re-commit, or rebase, strip any prior agent attribution from the commit message. Treat any tooling that suggests adding a Claude trailer as a bug to ignore.

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Architecture facts (locked — do not relitigate)

Spec: docs/superpowers/specs/2026-05-18-ace-music-studio-design.md Plan: docs/superpowers/plans/2026-05-18-ace-music-studio.md

1. Backend is ACE-Step 1.5 XL SFT — not ComfyUI. Installed from git (the package isn't on PyPI). The upstream repo is git+https://github.com/ace-step/ACE-Step-1.5.git; the Apple Silicon fork is git+https://github.com/clockworksquirrel/ace-step-apple-silicon.git.
2. Five tabs. Generate, Cover, Extend, Edit, Lyrics. Progressive disclosure — defaults stay short and reveal advanced controls only when asked.
3. One pipeline instance. Single ACE-Step pipeline; mode handlers (generate / cover / extend / edit) call different pipeline entry points. No re-instantiation between calls.
4. @spaces.GPU is applied at module load time. Identity decorator off Spaces. The decorator's duration= parameter takes a callable that estimates per-call timeout from (mode, params, multiplier). Estimator clamps at [60, 300] s.
5. Qwen 2.5 7B handles lyrics generation. Text-only inference; full multimodal weights are NOT required. On Mac the MLX path is used via mlx-lm.
6. HF cache → ./models/<repo>/ symlink. ACE-Step looks for files at local_model_path/.... app._bootstrap() symlinks every cached snapshot into ./models/<org>/<repo>/ so the preload weights are findable. On Spaces, the build-user-owned ~/.cache/huggingface/hub is mirrored to runtime-writable ~/hf-cache-rw/ first, then symlinked.
7. One Gradio process. Lazy backend singleton. get_backend() constructs the pipeline on the first request (~30–60 s warm-up). Module import is fast.

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Gotchas we already paid for (don't re-discover)

Each of these cost a debug cycle. Read once.

MPS / Apple Silicon

• torch.mps has no mem_get_info. Any VRAM-gate that calls that method raises AttributeError. Fix: vram_limit_for("mps") returns None so the gate short-circuits.
• Several ops aren't implemented on the MPS backend (SDPA variants, some index ops). app.py sets PYTORCH_ENABLE_MPS_FALLBACK=1 so they degrade to CPU instead of crashing.

ACE-Step gotchas

TBD as discovered during M1+ implementation. Record new ones here as they come up.

Dependency footguns

• ace-step is NOT on PyPI. Install from git (see requirements.txt).
• Don't pin spaces in requirements.txt. HF Spaces' ZeroGPU build injects its own version. A pin causes pip-resolve failure.
• transformers >= 5 may break imports. Pin: transformers>=4.45,<5.0.

Gradio 6.14 quirks

• Running version is gradio>=6.14,<7. requirements.txt reflects this; HF Spaces sdk_version: 6.14.0 matches.
• Don't put <script> tags inside gr.HTML blocks — they get stripped. JS goes in gr.Blocks(head=…).
• info= is not accepted by gr.Audio or gr.File on 6.14. tooltips.py keeps the strings for COVER_REF_AUDIO, EXTEND_SEED_AUDIO, EDIT_SOURCE_AUDIO, LORA_UPLOAD as the single source of truth — when upstream lands info= on those components, they're a one-line wire-up away.
• Slate-blue band around primary CTA: defeated via .styler { background: transparent } in theme.CSS. If a future Gradio bump reintroduces it, the override needs revisiting.

HF Spaces deployment

• preload_from_hub is build-time only. Runtime falls back to network if any required file isn't preloaded. Use broad globs so configs + index.json files come along.
• ZeroGPU build injects spaces==0.50.0. If requirements.txt pins spaces==0.30.0, pip resolution fails. Don't pin spaces at all — let HF provide it.
• The @spaces.GPU decorator must be applied at module load. Runtime decoration isn't detected by ZeroGPU's startup analyzer.

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Coding conventions

• Python 3.11. HF Spaces base image is 3.11; older syntax (like no match) is fine.
• Flat top-level layout. No src/, no nested packages. One .py per responsibility.
• No conda. python3.11 -m venv .venv; brew for system binaries.
• No emojis in code or commits unless explicitly requested. UI strings (CTA banner, button labels) are OK because they're user-facing copy, not code.
• Type hints on public functions. Internal helpers can skip them when obvious.
• Imports at the top of the file. Inline imports only to break circular deps OR to defer heavy modules (ace-step, torch, mlx) for fast CI startup.
• ruff format + ruff check both pass in CI. No exceptions.

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Commits

• Conventional Commits: <type>(<scope>): <subject> — types: feat, fix, chore, docs, test, refactor, ci, perf.
• Subject is imperative, lowercase, no trailing period.
• Body explains why when not obvious. Reference the spec / plan section if relevant.
• Frequent small commits — one logical change per commit.
• NO Claude trailer. See top of file.

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Testing

• TDD per the plan. Each implementation task has the failing test first.
• L1 + L2 in CI (no GPU): module structure, mocked pipeline call boundaries, ruff. tests/test_smoke_gpu.py is the GPU smoke; it's marked with @pytest.mark.gpu and skipped by default (pyproject addopts = -m 'not gpu').
• No mocks for ACE-Step internals. Mock only the pipe(...) call boundary so the mode-handler logic is verified at the boundary.
• Use pytest -m gpu to opt into the GPU smoke (~32 GB download on a cold cache; runs full generate + cover + extend + edit).

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Out of scope for v1 (don't add without asking)

Per spec §13:

• Multi-prompt batch queue
• Persistent generation history
• User accounts
• Telemetry dashboard
• Voice cloning (RVC)
• LoRA training in-app
• ControlNet-style conditioning
• Spectrogram visualization
• Multi-language UI strings
• Watermarking output audio
• Browser audio editing
• Multi-tenant rate limiting
• DAW export

If a task feels like it needs one of these, stop and ask the user.

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When in doubt

1. Read the spec + plan. Fifteen minutes of reading vs a day of wrong implementation.
2. Read SKILLS.md for the process side — debugging, deployment, when to commit, when to verify.
3. git log --oneline — most non-obvious decisions have a fix-commit explaining the reasoning.
4. Ask the user before changing architectural shape or adding scope outside the v1 list.