Each qmd is now rendered inside an isolated throwaway copy of the quarto project (option squash.isolate_render, TRUE by default). Concurrent renders no longer share the project state (.quarto/ crossref index, _extensions/ resolution), which removes the random Failed to render errors of parallel compilation (quarto-dev/quarto-cli#2749).
Isolation falls back to rendering in place whenever it is not possible: no quarto project above the qmd, project with a project-level output-dir (websites, books), or filesystem without symlink support (e.g. Windows without the symlink privilege). Every filesystem step of the isolation is checked so a partial isolated project can never be rendered silently.
Outputs are copied back to the real chapter when they are new or updated, so re-renders refresh files left by a previous run.
render_single_qmd() now reports the underlying error message instead of discarding it.
squash 1.2.0
The rendering of the Qmd is now performed insistently with purrr::insistently(), and can be configured in the rendering functions.