showtime 0.4.2

showtime 0.4.2: chapter mode for long films, two render failures under load fixed, more browsers without a GPU, sound that stays in sync when you cut a render, your own local voice engines, and help pages for when something goes wrong. Every change, with its reasons and limits, is in CHANGELOG.md under 0.4.2; the README has a short "New in 0.4.2" and What's new one sentence for each.

Render

• Chapter mode. render --chapters plans the pieces from your chapters (or the film's acts), --chapter N --job J renders one, and --join --job J joins them with one soundtrack for the whole video and checks every seam before the file is named final. On one machine a whole render is faster: chapters are for a later fix of one chapter (after a whole render or a join), a long film, or a second machine (not measured) (#22).
• Capture lanes keep the video's size under load. Under heavy load a lane could take its screenshots at the browser window's size and the frames were scaled without a word. The renderer now sets the page size again once the page is ready and checks every screenshot's size, retaking a wrong one. With 3 workers on a 6-core Intel Mac with a GPU under load, 7 of 40 renders had a wrong-sized lane before the fix and 0 of 30 after (#49).
• A frame that never comes no longer stalls a render. It is drawn again in a new browser (render) or ends the check with an error naming its step, when the browser reports its processes' work; otherwise the 10-minute cap stays (#24). A WebGL canvas that loses its context on the GPU renders again without the GPU (--gpu off) instead of shipping white.
• More browsers without a GPU. --workers auto uses CPU threads - 2 from 8 threads up (at most 8, within the frame, memory and SHOWTIME_MAX_WORKERS limits): 6 browsers instead of 3 on an 8-thread machine; with a GPU nothing changes (#41).

Footage and voice

• edit render keeps the sound in sync with the picture on showtime's own renders; a range could come out up to 21 ms early (#38).
• On Windows, several audio mix runs writing into one folder at once no longer fail with "permission denied".
• voice script --fit S --estimate says up front whether the narration can fit, before it synthesizes a line (#28, #45).
• Extra local voice engines load by name from ~/.showtime/engines/, and doctor no longer fails on Kokoro when you chose another engine (#8; proposed and designed by @heavygee, who also wrote a matching PR, #36).

Help

• A first-video guide, troubleshooting by symptom and a glossary; showtime doctor ends with a link to the troubleshooting page when a check fails, and the site's docs start on "Start here".

Issues closed: #8, #13, #14, #21, #22, #23, #24, #26, #27, #28, #29, #30, #31, #32, #33, #34, #35, #38, #39, #40, #41, #42, #43, #44, #45, #46, #47, #48, #49.

Still open: #12 (nightly test_cut_frames on the Intel Mac runner). 0.4.2 ships the fix (a lost WebGL canvas renders again without the GPU); it closes once the nightly passes on the released code.

Testing

• Full suite (every test file) on the release commit: green on Linux x64, Windows, macOS on Apple Silicon and macOS on Intel.
• CI on the release PR: fast suite on Linux, Windows and macOS; end-to-end (install, setup, render, qa, captions, MCP) on Linux ARM, Windows x64, Windows ARM and macOS; check_release 0 errors, 0 warnings; version 0.4.2 in every manifest.

Install or update: in Claude Code, /plugin marketplace add FavioVazquez/showtime then /plugin install showtime@showtime; the README covers other agents. The attached showtime-0.4.2.mcpb is the MCP bundle for desktop clients.