# VoiceGate HF Space Work Log

This document records the effective work completed while preparing the
`build-small-hackathon/VoiceGate` Hugging Face Space, plus the pitfalls found
and how they were resolved.

## Current Snapshot

- Space: `https://huggingface.co/spaces/build-small-hackathon/VoiceGate`
- Space git remote: `https://huggingface.co/spaces/build-small-hackathon/VoiceGate`
- Runtime hardware: ZeroGPU / `zero-a10g`
- Space SDK: Gradio
- Local Space wrapper repo: `VoiceGate-hf`
- Local upstream reference checkout: `VoiceGate/`
- Latest confirmed normal runtime commit: `316b35db739d74d05543d6c8c9dd9c16e0580b17`
- Current expected Space secret: `DEEPSEEK_API_KEY`
- Default persistent model root: `/data/voicegate_models`

Do not commit API keys, model weights, uploaded media, generated outputs, or the
local `VoiceGate/` upstream checkout.

## Executive Summary

The Space is no longer just a blank scaffold. It can now run Gradio, invoke
ZeroGPU, prepare a ComfyUI runtime, start ComfyUI from a GPU-backed Gradio
function, and submit several segmented ComfyUI workflows.

Confirmed working:

- Hugging Face Space git push and normal rebuild flow.
- Dev Mode SSH for CPU/container diagnostics.
- ZeroGPU invocation from Gradio through `@spaces.GPU`.
- ComfyUI startup from inside a `@spaces.GPU` function.
- ComfyUI API calls from the Gradio process.
- DeepSeek-compatible LLM node with the Space secret.
- MelBand RoFormer smoke tests in CPU mode and ZeroGPU mode.
- VoxCPM2 TTS-only smoke test in ZeroGPU mode.
- VoiceBridge ASR-only smoke test in ZeroGPU mode.
- Persistent model storage for VoxCPM2, MelBand, Qwen3-ASR, and Qwen3 forced
  aligner under `/data`.

Not yet confirmed at the start of 2026-06-06:

- SRT split -> VoxCPM -> SRT merge.
- Full short-audio VoiceGate workflow.
- Final user-facing Gradio upload/download UI.

## Repository Setup Completed

- Created and pushed the Space wrapper repository.
- Kept `VoiceGate/` as a local-only upstream reference and ignored it in git.
- Preserved Hugging Face LFS rules.
- Copied deployment workflows:
  - `workflows/voicegate_api.json`
  - `workflows/voicegate_ui.json`
- Confirmed the API workflow JSON is valid.
- Confirmed workflow files contain no committed API key.

## Dependency Inventory Completed

Required workflow node providers were identified and pinned:

- ComfyUI core:
  `comfyanonymous/ComfyUI`
- VoiceBridge:
  `YanTianlong-01/comfyui_voicebridge`
- RunningHub VoxCPM:
  `RH-RunningHub/ComfyUI_RH_VoxCPM`
- MelBand RoFormer:
  `kijai/ComfyUI-MelBandRoFormer`
- RunningHub LLM API:
  `HM-RunningHub/ComfyUI_RH_LLM_API`
- rgthree:
  `rgthree/rgthree-comfy`
- Easy Use:
  `yolain/ComfyUI-Easy-Use`
- Comfyroll:
  `Suzie1/ComfyUI_Comfyroll_CustomNodes`
- MW AudioTools:
  `billwuhao/ComfyUI_AudioTools`

Important node source confirmations:

- `ReplaceText` is provided by ComfyUI core extra nodes.
- `MergeAudioMW` is provided by `ComfyUI_AudioTools`.
- `RH_LLMAPI_NODE` is provided by `ComfyUI_RH_LLM_API`.

## Runtime Bootstrap Added

The following scripts were added:

- `scripts/bootstrap_comfy.py`
  - Clones ComfyUI.
  - Checks out pinned commits.
  - Clones required custom node repositories.
  - Installs ComfyUI and custom node Python requirements.
  - Prepares expected model directories.
  - Optionally downloads large model assets with `--with-models`.
- `scripts/run_comfy.py`
  - Starts ComfyUI.
  - Waits for `/system_stats`.
  - Supports `--cpu` for SSH diagnostics.
- `scripts/workflow_client.py`
  - Loads `workflows/voicegate_api.json`.
  - Uploads audio through the ComfyUI API.
  - Patches workflow inputs.
  - Submits `/prompt`.
  - Waits for `/history/{prompt_id}`.

Workflow patching currently covers:

- Node `16`: uploaded audio filename.
- Node `105`: `DEEPSEEK_API_KEY`.
- Node `105`: API base URL.
- Node `105`: LLM model name.
- Node `110`: target language.
- Node `180`: job-specific audio output prefix.
- Node `214`: job-specific SRT output prefix.

## Hugging Face Space Runtime Findings

### Dev Mode and SSH

SSH target:

```text
build-small-hackathon-voicegate@ssh.hf.space
```

Local private key:

```text
C:\Users\yantianlong\.ssh\codex_space_voicegate
```

SSH is only available while the Space is in Dev Mode. Normal running Spaces do
not accept SSH and return:

```text
Bad request: SSH in only allowed in Dev mode
```

Dev Mode can be toggled through the Hugging Face API endpoint:

```text
POST /api/spaces/build-small-hackathon/VoiceGate/dev-mode
```

Use Dev Mode for diagnostics only. Persistent fixes must be committed locally
and pushed.

### Dev Mode Stale Commit Pitfall

The running container initially stayed on the original template commit:

```text
a94117f35a42cb17f654ae70cbe619c15345d057
```

even after newer commits were pushed. `restart_space` alone did not move it to
the latest repository state while Dev Mode was enabled.

Fix:

- Disable Dev Mode.
- Use `factory_reboot=True` or push a new commit to trigger a normal rebuild.
- Confirm runtime metadata reports the latest commit.

### ZeroGPU Startup Requirement

When Dev Mode was disabled, the Space entered `RUNTIME_ERROR` with:

```text
No @spaces.GPU function detected during startup
```

Fix:

- Import `spaces`.
- Add at least one `@spaces.GPU(duration=...)` function in `app.py`.

Current placeholder fix:

```python
@spaces.GPU(duration=30)
def placeholder():
    ...
```

Later this placeholder was replaced by real diagnostic functions:

```python
@spaces.GPU(duration=60)
def gpu_smoke_test():
    ...

@spaces.GPU(duration=900)
def comfy_runtime_test():
    ...
```

### SSH Does Not Expose ZeroGPU CUDA

Starting ComfyUI normally through SSH failed with:

```text
RuntimeError: No CUDA GPUs are available
```

Conclusion:

- SSH is useful for CPU-mode diagnostics.
- Real GPU work must run from the Gradio process inside a `@spaces.GPU`
  function.

CPU diagnostic command:

```bash
python scripts/run_comfy.py --cpu
```

### Gradio Request Timeout During Bootstrap

Long bootstrap work should not run synchronously inside a Gradio request. The
first attempt did this:

```text
Gradio click -> bootstrap_comfy.py -> clone repos -> pip install -> start ComfyUI
```

The request was interrupted by Gradio/ZeroGPU's outer queue after roughly 2.5
minutes and returned:

```text
event: error
data: {"error": null}
```

Fix:

- Add a non-GPU `Prepare` action that starts `scripts/bootstrap_comfy.py` as a
  background process.
- Add `Prepare Status` to poll `/tmp/voicegate_bootstrap.log`.
- Keep GPU actions focused on starting ComfyUI and running actual CUDA work.

This avoids wasting ZeroGPU time on clone/install steps and prevents the request
from being killed before diagnostics can return useful logs.

### Runtime Pip Install Pitfall

The background bootstrap installed a large dependency set and upgraded the
on-disk Torch package. The already-running Gradio process continued to report:

```text
torch=2.11.0+cu130
```

while the ComfyUI subprocess started afterwards reported:

```text
pytorch_version=2.12.0+cu130
```

This is workable for diagnostics, but final production should avoid heavy
runtime `pip install` where possible. Prefer moving stable dependencies into
Space build-time requirements or explicitly controlling pins.

### ZeroGPU Duration and Quota Pitfall

The ASR diagnostic was first decorated with:

```python
@spaces.GPU(duration=1800)
```

The Space rejected it before execution:

```text
ZeroGPU illegal duration
The requested GPU duration is larger than the maximum allowed
```

After reducing the function to `duration=1200`, the Space still rejected the
call because the quota precheck reported:

```text
You have exceeded your Pro ZeroGPU quota (1800s requested vs. 1389s left)
```

The working diagnostic used:

```python
@spaces.GPU(duration=900)
```

For future tests, keep diagnostic durations conservative and increase only when
the workflow has already proven it needs more time.

## Dependency Pitfalls and Fixes

`ComfyUI_AudioTools` initially failed to import.

First failure:

```text
SoX could not be found
ModuleNotFoundError: No module named 'sounddevice'
```

Second failure after adding `sounddevice`:

```text
OSError: PortAudio library not found
```

Third failure:

```text
ModuleNotFoundError: No module named 'easydict'
```

Fourth failure:

```text
ModuleNotFoundError: No module named 'pytorch_lightning'
```

Fixes added:

- `packages.txt`
  - `sox`
  - `libportaudio2`
  - `portaudio19-dev`
- `requirements.txt`
  - `sounddevice`
  - `easydict`
  - `pytorch-lightning`

Final verification:

```text
0.4 seconds: /home/user/app/ComfyUI/custom_nodes/ComfyUI_AudioTools
```

with no `IMPORT FAILED` entry.

## ComfyUI API Smoke Test

Test audio source:

```text
D:\voicebridge-test-audio\test_audio\2-坤哥.MP3
```

The first upload attempt used a plain PowerShell byte pipeline and corrupted the
binary file. The remote file was identified as text instead of MP3, and
`LoadAudio` failed with:

```text
Invalid data found when processing input: 'avcodec_send_packet()'
```

Fix:

- Upload binary test media through a binary-safe method.
- Verify remote `sha256sum` before using the file.

Successful upload result:

```text
/tmp/voicegate_test_audio.mp3: Audio file with ID3 version 2.3.0
```

ComfyUI API endpoints verified in Dev Mode:

- `/system_stats`
- `/upload/image`
- `/prompt`
- `/history/{prompt_id}`

Minimal test workflow:

```text
LoadAudio -> SaveAudioMP3
```

Successful `/history/{prompt_id}` result:

```text
status_str: success
completed: true
```

Output reported by ComfyUI:

```text
audio/api_smoke_voicegate_00001.mp3
```

## Segmented Workflow Smoke Tests

### ComfyUI From Gradio ZeroGPU

On 2026-06-05, `app.py` was expanded with diagnostic Gradio actions:

- `prepare_runtime`: starts `scripts/bootstrap_comfy.py` in the background and
  writes progress to `/tmp/voicegate_bootstrap.log`.
- `prepare_status`: reports the background bootstrap status and log tail.
- `comfy_runtime_test`: runs inside `@spaces.GPU`, starts ComfyUI, and calls
  `/system_stats`.
- `melband_gpu_test`: runs a tiny MelBand workflow inside `@spaces.GPU`.
- `voxcpm_tts_gpu_test`: runs a tiny VoxCPM2 TTS-only workflow inside
  `@spaces.GPU`.

The first attempt ran the full bootstrap synchronously inside a Gradio request
and the request was interrupted by the outer queue with `event: error` and no
function payload after roughly 2.5 minutes. The fix was to start bootstrap as a
background process and poll a status endpoint.

The background prepare completed successfully. It installed a large dependency
set and upgraded the on-disk Torch package from `2.11.0` to `2.12.0`. The
already-running Gradio process still reported its originally imported
`torch=2.11.0+cu130`, while the newly started ComfyUI subprocess reported:

```text
pytorch_version=2.12.0+cu130
```

This is acceptable for the smoke test, but runtime pip installs are not ideal
for the final app. A later pass should move heavy Python dependencies into the
Space build/install phase or pin the root requirements more deliberately.

`comfy_runtime_test` result:

```text
cuda_available=True
comfy_ready=true
comfy_elapsed_sec=16.0
ComfyUI version=0.24.0
device=cuda:0 NVIDIA RTX PRO 6000 Blackwell Server Edition MIG 2g.48gb
vram_total=50868518912
```

Observed behavior: separate `@spaces.GPU` calls may run in separate worker
processes, so the ComfyUI subprocess should not be assumed to persist across
different button/API calls.

### ZeroGPU Gradio Invocation

On 2026-06-05, the Space was tested in normal runtime, with Dev Mode off, using
a Gradio button backed by:

```python
@spaces.GPU(duration=60)
def gpu_smoke_test():
    ...
```

The private Space API was called with the local Hugging Face token through:

```text
POST /gradio_api/call/gpu_smoke_test
GET /gradio_api/call/gpu_smoke_test/{event_id}
```

Result:

```text
torch=2.11.0+cu130
cuda_available=True
cuda_device_count=1
device_name=NVIDIA RTX PRO 6000 Blackwell Server Edition MIG 2g.48gb
total_memory_gb=47.38
tensor_result=240.0
memory_reserved_mb=2.00
```

This confirms ZeroGPU CUDA is available from the normal Gradio runtime when the
work is executed inside a `@spaces.GPU` function. SSH still should be treated as
CPU-only diagnostic access.

### DeepSeek LLM Node

On 2026-06-05, `RH_LLMAPI_NODE` was tested through ComfyUI in Dev Mode using
the Space `DEEPSEEK_API_KEY` secret. The key was not printed.

Minimal workflow:

```text
RH_LLMAPI_NODE -> easy showAnything
```

Prompt:

```text
Translate to Simplified Chinese: VoiceGate smoke test.
```

Result:

```text
status_str: success
output: VoiceGate 冒烟测试。
```

This confirms the RunningHub LLM node can read the Space secret and call the
DeepSeek-compatible API endpoint.

### MelBand RoFormer

On 2026-06-05, `MelBandRoFormerModelLoader` and `MelBandRoFormerSampler` were
tested through ComfyUI in CPU mode.

Input:

```text
1 second synthetic 440 Hz WAV generated with ffmpeg
```

Minimal workflow:

```text
LoadAudio -> MelBandRoFormerModelLoader -> MelBandRoFormerSampler
  -> SaveAudioMP3(vocals)
  -> SaveAudioMP3(instruments)
```

Result:

```text
status_str: success
audio/melband_smoke_vocals_00001.mp3
audio/melband_smoke_instruments_00001.mp3
```

CPU-mode runtime for the 1 second smoke input was about 51 seconds. Real runs
should execute inside a `@spaces.GPU` function.

Later on 2026-06-05, the same kind of tiny MelBand smoke test was run from the
normal Gradio runtime inside `@spaces.GPU`.

Input:

```text
1 second synthetic 440 Hz WAV written to ComfyUI/input
```

Result:

```text
status_str=success
completed=True
audio/melband_gpu_32459bea_instruments_00001.mp3
audio/melband_gpu_32459bea_vocals_00001.mp3
elapsed_sec=78.3
```

This confirms the MelBand custom node and model can execute from the Space
ZeroGPU path.

### VoxCPM2 TTS-only

On 2026-06-05, a minimal VoxCPM2 TTS-only workflow was run from the normal
Gradio runtime inside `@spaces.GPU`.

Minimal workflow:

```text
RunningHub_VoxCPM_LoadModel -> RunningHub_VoxCPM_Generate -> SaveAudioMP3
```

Prompt text:

```text
你好，VoiceGate GPU 语音合成测试。
```

Result:

```text
status_str=success
completed=True
audio/voxcpm_tts_gpu_cda209ec_00001.mp3
elapsed_sec=766.2
```

This confirms VoxCPM2 fits and executes in ZeroGPU, but the first cold TTS-only
run was very slow. The final app should minimize cold starts, avoid repeated
ComfyUI/model reloads where possible, and use shorter diagnostic prompts while
tuning.

### VoiceBridge ASR-only

On 2026-06-06, a minimal VoiceBridge ASR-only workflow was run from the normal
Gradio runtime inside `@spaces.GPU`.

Before running ASR, `scripts/bootstrap_comfy.py` was extended so Qwen ASR models
also live on persistent storage:

```text
/home/user/app/ComfyUI/models/Qwen3-ASR
  -> /data/voicegate_models/Qwen3-ASR
```

The model preparation downloads:

```text
/data/voicegate_models/Qwen3-ASR/Qwen3-ASR-1.7B
/data/voicegate_models/Qwen3-ASR/Qwen3-ForcedAligner-0.6B
```

Minimal workflow:

```text
LoadAudio
  -> VoiceBridgeASRLoader(attention=sdpa, forced_aligner=Qwen/Qwen3-ForcedAligner-0.6B)
  -> VoiceBridgeASRTranscribe(return_timestamps=True)
  -> GenerateSRT
  -> easy showAnything
```

Input:

```text
D:\voicebridge-test-audio\test_audio\2-坤哥.MP3
```

Result:

```text
status_str=success
completed=True
elapsed_sec=62.4
```

Returned SRT text:

```text
1
00:00:02,080 --> 00:00:03,200
全民制作人们 大家好

2
00:00:03,439 --> 00:00:06,160
我是练习时长两年半的个人练习生蔡徐坤

3
00:00:06,480 --> 00:00:09,359
喜欢唱、跳、rap、篮球、music
```

This confirms the Qwen3-ASR model, forced aligner, VoiceBridge ASR nodes, and
SRT generation can run in the Space ZeroGPU path. The smoke test intentionally
used `attention=sdpa` instead of `flash_attention_2`; `flash_attention_2`
availability remains unverified.

## Secrets and API Keys

`DEEPSEEK_API_KEY` should be stored only as a Hugging Face Space Secret.

Current expected secret:

```text
DEEPSEEK_API_KEY
```

Optional variables:

```text
DEEPSEEK_BASE_URL=https://api.deepseek.com
DEEPSEEK_MODEL=deepseek-v4-flash
```

Never store these values in:

- `app.py`
- workflow JSON files
- README files
- docs
- `.env` files committed to git

`scripts/workflow_client.py` reads these from environment variables.

`scripts/check_space_env.py` verifies whether these environment variables are
present without printing their values.

## Model Storage

Large model files should live on the Space persistent storage volume instead of
inside `/home/user/app`, because `/home/user/app` can be replaced during Space
rebuilds.

Default model root:

```text
/data/voicegate_models
```

`scripts/bootstrap_comfy.py` creates symlinks from ComfyUI's expected paths to
that persistent root:

```text
ComfyUI/models/voxcpm/VoxCPM2
  -> /data/voicegate_models/voxcpm/VoxCPM2

ComfyUI/models/diffusion_models/MelBandRoFormer_comfy
  -> /data/voicegate_models/diffusion_models/MelBandRoFormer_comfy

ComfyUI/models/Qwen3-ASR
  -> /data/voicegate_models/Qwen3-ASR
```

Override the root with:

```text
VOICEGATE_MODEL_ROOT
```

On 2026-06-05, the first two explicit ComfyUI-path models were downloaded to
persistent storage:

```text
/data/voicegate_models/voxcpm/VoxCPM2/model.safetensors
/data/voicegate_models/voxcpm/VoxCPM2/audiovae.pth
/data/voicegate_models/diffusion_models/MelBandRoFormer_comfy/MelBandRoformer_fp32.safetensors
/data/voicegate_models/Qwen3-ASR/Qwen3-ASR-1.7B
/data/voicegate_models/Qwen3-ASR/Qwen3-ForcedAligner-0.6B
```

Verified symlinks:

```text
/home/user/app/ComfyUI/models/voxcpm/VoxCPM2
  -> /data/voicegate_models/voxcpm/VoxCPM2

/home/user/app/ComfyUI/models/diffusion_models/MelBandRoFormer_comfy
  -> /data/voicegate_models/diffusion_models/MelBandRoFormer_comfy

/home/user/app/ComfyUI/models/Qwen3-ASR
  -> /data/voicegate_models/Qwen3-ASR
```

`DEEPSEEK_API_KEY` was also verified as present in the Space environment without
printing its value.

Model download pitfall:

- `huggingface-cli download` is deprecated and failed in the Space.
- `hf download` also failed because of a CLI dependency compatibility issue.
- `scripts/bootstrap_comfy.py` now uses the `huggingface_hub` Python API
  directly for model downloads.

## Current Known Good Commits

- `683b147` Add ComfyUI runtime bootstrap scripts
- `520334e` Record Space SSH runtime findings
- `223ef10` Add ZeroGPU placeholder hook
- `5dac213` Add missing AudioTools dependencies
- `d849d03` Record ComfyUI API smoke test
- `79b8b37` Add GPU smoke test button
- `6e4cd3f` Run Space preparation in background
- `b39ef30` Add ASR diagnostic workflow and deployment guide
- `316b35d` Reduce ASR ZeroGPU duration
- `90f8205` Reduce full workflow smoke test runtime
- `b8ca809` Initialize matplotlib backend for Gradio

## Full Workflow Status

On 2026-06-06, the copied Space workflows were checked against the upstream
VoiceGate workflows:

```text
workflows/voicegate_api.json == VoiceGate/workflows/VoiceGate-Workflow_api.json
workflows/voicegate_ui.json == VoiceGate/workflows/VoiceGate-Workflow.json
checked_connections=31
mismatches=0
```

The connection validator resolves ComfyUI UI-only `SetNode` / `GetNode` helper
pairs before comparing the API workflow to the UI workflow. With that resolution,
the API graph used by the Space follows
`VoiceGate/workflows/VoiceGate-Workflow.json`.

Full workflow runtime attempts:

- Initial full workflow submission failed at prompt validation because
  `VoiceBridgeASRLoader` required `source`; `scripts/workflow_client.py` now
  patches node `31` with `source=HuggingFace`.
- The next run failed because node `31` requested `flash_attention_2`; the Space
  runtime did not have `flash_attn`, so the workflow patch now uses
  `attention=sdpa`.
- A later run submitted prompt `16b45231-c2e3-4ded-aa38-ac6a3b6813d8` and
  reached the heavy nodes, including MelBand, VoxCPM, ASR, and forced aligner
  loading, but exceeded the app-side `800s` wait window before `/history`
  returned completion.
- To reduce smoke-test runtime without changing graph connections, commit
  `90f8205` patches ASR `max_new_tokens=256` and VoxCPM inference
  `inference_steps=4`.
- The next retry did not start execution because Hugging Face ZeroGPU quota was
  exhausted before scheduling:

```text
ZeroGPU quota exceeded
1200s requested vs. 407s left
try again in about 17:22:12
```

Current conclusion: workflow connection fidelity is verified, and individual
GPU smoke tests for CUDA, ComfyUI, MelBand, VoxCPM TTS, and ASR have passed.
The remaining full end-to-end verification is blocked by available ZeroGPU
quota/runtime, not by a known workflow connection mismatch.

Follow-up result on the duplicated personal Space:

- Space: `YanTianlong/VoiceGate-personal`
- Hardware: Nvidia T4 Small
- Input: short `2-坤哥.MP3` test audio
- Target language: English
- Result: success
- Output: `audio/voicegate_full_23499a26_00001.mp3`
- Total elapsed time reported by Gradio: `24.4s`
- ComfyUI websocket elapsed time: `23.9s`

Top measured node timings:

```text
206 RunningHub_VoxCPM_Generate: 8.2s
99 MelBandRoFormerSampler: 6.6s
105 RH_LLMAPI_NODE: 4.5s
33 VoiceBridgeASRTranscribe: 2.2s
45 VoiceBridgeASRTranscribe: 1.9s
180 SaveAudioMP3: 0.4s
```

This confirms the full VoiceGate workflow can run end-to-end on a warm personal
T4 Small Space for very short audio. Longer audio remains untested on T4 Small
and may still hit runtime or memory limits.

## Gradio Interface Status

The first user-facing Gradio interface now has two tabs:

- `Translate`: simple user flow with audio upload, target language dropdown,
  generated translated dubbing audio output, original/translated subtitle text,
  downloadable `.srt` subtitle files, and status.
- `Diagnostics`: retained internal test controls for Prepare, GPU, ComfyUI,
  MelBand, VoxCPM TTS, ASR, and full workflow timing.

Supported target-language dropdown values:

```text
Arabic, Burmese, Chinese, Danish, Dutch, English, Finnish, French, German,
Greek, Hebrew, Hindi, Indonesian, Italian, Japanese, Khmer, Korean, Lao, Malay,
Norwegian, Polish, Portuguese, Russian, Spanish, Swahili, Swedish, Tagalog,
Thai, Turkish, Vietnamese
```

The `Translate` tab also exposes an advanced cleanup slider:

```text
TTS segment trim start
range: 0.0 - 1.0 seconds
default: 0.0
workflow node: 268 TrimAudioDuration.start_index
```

This controls the trim node between `RunningHub_VoxCPM_Generate` and
`VoiceBridgeAudioListMergerBySRT`. It can skip the first `n` seconds of every
generated TTS segment when a TTS segment begins with noise or an unstable
attack. It changes only node input parameters, not workflow graph connections.

User-facing reliability pitfall found on the duplicated personal Space:

- After switching/rebuilding hardware, ComfyUI started successfully but the
  MelBand model list was empty.
- `/prompt` failed with:

```text
MelBandRoFormerModelLoader 96
model_name: 'MelBandRoFormer_comfy/MelBandRoformer_fp32.safetensors' not in []
```

Root cause: the runtime container had ComfyUI/custom nodes, but required model
files were not present or linked under ComfyUI's model directories yet. Internal
diagnostic usage can tolerate a manual `Prepare` step, but the user-facing
`Translate` path must not require that.

Mitigation added:

- Before running full VoiceGate, the app checks required MelBand, VoxCPM, and
  Qwen3-ASR model paths.
- If any are missing, it runs `scripts/bootstrap_comfy.py --with-models`
  synchronously and rechecks the paths.
- If models still cannot be prepared, the app returns a clear preparation error
  instead of a raw ComfyUI prompt-validation failure.

## Remaining Work

Next recommended steps:

1. Run progressively larger workflows:
   - SRT split and merge
   - full short-audio VoiceGate workflow on the organization ZeroGPU Space after
     quota recovers
2. Polish the first Gradio user interface and validate the automatic model
   preparation path after Space rebuilds/hardware changes.
3. Reduce runtime dependency installation and model reload overhead.