Proofread the subtitle text with a local (or remote) large language model - typos, spelling, grammar, punctuation and casing. Nothing is changed until you apply the suggestions you agree with.

*.gguf files placed in the llama.cpp models folder also appear.Press Review to start. The subtitle is sent to the model in small batches, and suggestions appear in the grid while the review runs - you can inspect, check and uncheck rows before it finishes, or press Stop to keep what was found so far.
Each suggestion shows:
Filter the grid with the category chips above it. Press Apply N fixes to apply the checked suggestions - this is a single undo step (Ctrl+Z reverts everything).
Lines are grouped into sentence units, so a sentence that continues over several subtitles is always reviewed as a whole, and the model sees a couple of surrounding lines as read-only context. Corrections never move words between lines, so timing and reading speed are unaffected. Suggestions belonging to the same sentence are checked and unchecked together.
The Edit prompt… button opens the review instructions sent to the model. {language} is replaced with the auto-detected subtitle language. The strict data-exchange contract is appended by Subtitle Edit and cannot be broken by prompt edits, so feel free to tailor the instructions - e.g. “also flag anachronisms” or “never touch song lyrics”.