Two server behaviours left ffmpeg (8.1/9.0) without the file size, after
which every seek failed with "size -38" until a reload:
- dart:io holds response headers until body bytes exist: a stalled
source meant no headers within mpv's 5 s timeout. Relay byte responses
are now written on the raw connection, headers with the first bytes or
after 4 s, and a swap ends waiting reads with a plain close.
- every response closed its socket without saying connection: close, so
ffmpeg 8.x reused a dead connection for its next seek (pol's X clips).
The server now says it whenever the request asks.
A failed pull waits 250 ms doubling to 8 s instead of re-pulling at once
(the ~130 ms storm that drew Bilibili's 412/403); 412 counts as an expired
URL and re-resolves the page, at most once per 60 s. The app reloads a
player once per media when ffmpeg reports the lost size anyway. P37: a
read that waits past ffmpeg's retry budget still ends the file early.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
