def render_full_set(progress=gr.Progress()):
    """Render the DJ set using stem separation (demucs) for surgical mixing."""
    if not app_state.transitions:
        return None, "⚠️ Generate a set plan first"

    progress(0.02, desc="Starting stem-based render...")

    def progress_cb(p, msg):
        progress(0.02 + p * 0.90, desc=msg)

    # Separate stems for each track using demucs
    import torch
    from demucs.pretrained import get_model
    from demucs.apply import apply_model
    from stem_mixer import load_stems, mix_stems, make_full

    device = "cuda" if torch.cuda.is_available() else "cpu"
    logger.info(f"Loading demucs model on {device}...")
    progress(0.03, desc="Loading demucs model...")
    
    try:
        model = get_model("htdemucs")
        model.eval().to(device)
    except Exception as e:
        logger.error(f"Failed to load demucs: {e}")
        # Fallback to non-stem mixer
        from mixer import mix_set
        set_audio, set_info = mix_set(
            app_state.analyses, app_state.set_order, app_state.transitions,
            progress_cb=progress_cb
        )
        app_state.rendered_set = set_audio
        progress(0.95, desc="Saving (non-stem fallback)...")
        tmp = tempfile.NamedTemporaryFile(suffix='.wav', delete=False)
        audio_int16 = (set_audio.T * 32767).astype(np.int16)
        scipy.io.wavfile.write(tmp.name, 44100, audio_int16)
        summary = f"# ✅ DJ Set Rendered (non-stem fallback)\n\n"
        summary += f"- **Duration:** {set_info.get('total_duration', 0):.0f}s\n"
        summary += f"- **Note:** demucs failed ({e}), used filter-based mixing\n"
        return tmp.name, summary

    # Separate each track into stems
    all_stems = {}
    for i, tidx in enumerate(app_state.set_order):
        track = app_state.analyses[tidx]
        progress(0.03 + (i / len(app_state.set_order)) * 0.50,
                 desc=f"Separating stems: {track.filename[:30]}...")
        
        y, sr_file = librosa.load(track.path, sr=model.samplerate, mono=False)
        if y.ndim == 1:
            y = np.stack([y, y])
        
        wav = torch.from_numpy(y).float().unsqueeze(0).to(device)
        ref = wav.mean(1, keepdim=True)
        wav_norm = (wav - ref.mean()) / (ref.std() + 1e-8)
        
        with torch.no_grad():
            sources = apply_model(model, wav_norm, device=device, split=True, overlap=0.25)
        
        sources = sources[0] * ref.std() + ref.mean()
        stems = {}
        for name, source in zip(model.sources, sources):
            stem_audio = source.cpu().numpy()
            # Resample to 44100 if needed
            if model.samplerate != 44100:
                stem_audio = np.stack([
                    librosa.resample(stem_audio[c], orig_sr=model.samplerate, target_sr=44100)
                    for c in range(stem_audio.shape[0])
                ])
            stems[name] = stem_audio
        
        all_stems[tidx] = stems
        logger.info(f"Separated {track.filename}: {list(stems.keys())}")

    # Mix using stem mixer
    progress(0.55, desc="Mixing with stems...")
    set_audio, set_info = mix_stems(
        all_stems, app_state.analyses, app_state.set_order,
        progress_cb=lambda p, m: progress(0.55 + p * 0.35, desc=m)
    )
    app_state.rendered_set = set_audio

    progress(0.92, desc="Saving...")
    tmp = tempfile.NamedTemporaryFile(suffix='.wav', delete=False)
    audio_int16 = (set_audio.T * 32767).astype(np.int16)
    scipy.io.wavfile.write(tmp.name, 44100, audio_int16)

    # Summary
    summary = f"# ✅ DJ Set Rendered (stem-based mixing)\n\n"
    summary += f"- **Total duration:** {set_info.get('total_duration', 0):.1f}s "
    summary += f"({set_info.get('total_duration', 0)/60:.1f} min)\n"
    summary += f"- **Tracks:** {len(set_info.get('tracks', []))}\n"
    summary += f"- **Method:** Demucs stem separation → surgical drum/bass swap\n\n"

    summary += "## Tracklist\n"
    for i, t in enumerate(set_info.get('tracks', [])):
        summary += f"{i+1}. **{t['filename']}** — tl={t['tl_start']:.0f}s, stretch=×{t['stretch']:.3f}\n"

    return tmp.name, summary