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Self-hosting the subtitles model (mirror)

By default, live subtitles download the speech-to-text model on first use from Discourse's HuggingFace repository (Discourse/parakeet-tdt-0.6b-v3-onnx, a clone of the upstream ysdede/parakeet-tdt-0.6b-v3-onnx export). Sites that can't (or don't want to) let browsers reach huggingface.co — airgapped deployments, enterprise networks, or anyone who prefers to control the bytes — can serve the model themselves and point the resenha_stt_model_base_url site setting at their own mirror.

Only the model weights are affected. The runtime bundles (worker, VAD, onnxruntime) are always served from the plugin's own public/ directory and need no extra hosting.

What to mirror

Four files from the ysdede/parakeet-tdt-0.6b-v3-onnx repository (models are CC-BY-4.0; keep the repo's attribution requirements in mind), keeping their exact filenames, in a single flat directory:

File Size Purpose
encoder-model.onnx ~42 MB fp32 encoder graph (runs on WebGPU)
encoder-model.onnx.data ~2.4 GB encoder weights (external data referenced by the graph — the filename must not change)
decoder_joint-model.int8.onnx ~18 MB int8 decoder/joint (runs on WASM)
vocab.txt ~100 KB tokenizer vocabulary 
mkdir parakeet-tdt-0.6b-v3
cd parakeet-tdt-0.6b-v3
for f in encoder-model.onnx encoder-model.onnx.data \
         decoder_joint-model.int8.onnx vocab.txt; do
  curl -LO "https://huggingface.co/ysdede/parakeet-tdt-0.6b-v3-onnx/resolve/main/$f"
done

No subdirectory structure is required or supported: the plugin requests <base_url>/<filename> for each of the four files, nothing else.

Hosting requirements

The files are fetched by the browser (from a Web Worker on the forum's origin), not by the Discourse server, so the mirror must be reachable by your users and must speak CORS if it lives on a different origin:

  • Access-Control-Allow-Origin: <forum origin> (or *) on all four files.
  • HTTPS, if the forum is served over HTTPS (mixed content is blocked).
  • Correct Content-Length (any static file server does this) — it drives the download progress shown in the caption overlay, and the ~2.4 GB file arrives as one plain GET; resumable/range support is not needed.
  • Long-lived cache headers are still recommended (the files are immutable), though the browser keeps a durable Cache API copy after the first download, so mirrors are only re-hit when that storage is evicted.

Example nginx location:

location /models/parakeet-tdt-0.6b-v3/ {
  root /var/www;
  add_header Access-Control-Allow-Origin "https://forum.example.com";
  add_header Cache-Control "public, max-age=31536000, immutable";
}

Then set the site setting:

resenha_stt_model_base_url = https://cdn.example.com/models/parakeet-tdt-0.6b-v3

(Trailing slash optional.)

A custom mirror behaves exactly like the default source: streamed download progress in the caption overlay and a durable Cache API copy on the user's device.

Verifying a mirror

The end-to-end smoke harness can run against a local copy of the mirror directory:

flite -t "the quick brown fox jumps over the lazy dog" /tmp/fix.wav
STT_MODEL_DIR=/path/to/parakeet-tdt-0.6b-v3 \
  node scripts/smoke-stt-worker.mjs /tmp/fix.wav

It loads the shipped worker in headless Chromium (WebGPU required), serves the model files from the given directory exactly as a mirror would, and fails unless the fixture transcribes.