- Adds a background mode flag for `astro preview`, enabling preview servers to run as background processes and be managed via new subcommands; auto‑enabled for AI agents.
- Introduces experimental incremental static builds with cacheKey support and an optional `digest` on collection entries, plus a `session: false` config to tree‑shake session runtime.
- Includes numerous fixes: relative paths for `logger.entrypoint`, dev server host URL handling, correct icon glyphs, proper pathname with `build.format:'preserve'`, cookie handling in error pages, and popover attribute rendering.