Thumbnails

When a video finishes, we save its automatic poster frame plus up to six more frames spread through the video. List them, then pick one or upload your own JPEG or PNG (up to 2 MB, base64-encoded). Your choice becomes posterUrl everywhere: status, listings and webhooks.

GET  /videos/{id}/thumbnails
→ {"current": {"source": "auto"}, "candidates": [{"index": 0, "time": 6.0, "url": "https://…"}, {"index": 1, "time": 15.0, "url": "https://…"}, …]}

POST /videos/{id}/thumbnail   {"candidate": 1}
POST /videos/{id}/thumbnail   {"image": "<base64>", "contentType": "image/png"}

{"candidate": 0} goes back to the automatic frame. Videos made before thumbnail choices existed have no candidates, but you can still upload your own image.