New Features

Bun.cron — OS-Level Cron Jobs

Bun now includes a built-in Bun.cron API for registering OS-level scheduled jobs that work cross-platform:

• Register jobs using standard cron syntax that integrates with native schedulers (crontab on Linux, launchd on macOS, Task Scheduler on Windows)
• Parse cron expressions with Bun.cron.parse() to determine next execution times, supporting standard 5-field format, named days/months (MON–SUN, JAN–DEC), and nicknames like @yearly and @hourly
• Remove jobs with Bun.cron.remove() using job titles
• Jobs trigger a scheduled() export following the Cloudflare Workers Cron Triggers API

Re-registering with the same title overwrites the existing job in place, and platform-specific logging is available through standard system tools.

Bun.sliceAnsi — Terminal-Aware String Slicing

A new built-in that eliminates the need for the slice-ansi and cli-truncate npm packages. Bun.sliceAnsi provides:

• ANSI-aware slicing that preserves SGR color codes and OSC 8 hyperlinks while slicing by terminal column width
• Grapheme cluster support for correct handling of emoji, combining marks, and flag sequences
• Truncation with ellipsis that emits the truncation marker inside active styles for visual consistency but outside hyperlinks to prevent broken links
• Negative index support for slicing from the end of strings

Performance uses a three-tier strategy: SIMD fast path for ASCII, single-pass streaming for non-negative indices, and two-pass computation for negative indices.

Enhanced Markdown List Rendering

The Bun.markdown.render() API now passes richer metadata to list callbacks:

• listItem callbacks receive index, depth, ordered, and start properties, enabling custom nested numbering schemes (e.g., 1., a., i.) without post-processing
• list callbacks now include the depth property

Breaking change: The listItem callback now always receives a meta object; previously it was only passed for task list items. Use conditional checks on start and checked (which are undefined when not applicable) to handle different list types.

Improvements

--path-ignore-patterns for test discovery — Exclude files and directories from bun test using glob patterns, either via the new command-line flag or test.pathIgnorePatterns in bunfig.toml. Matched directories are pruned during scanning for efficiency.

UDP socket fixes on macOS — Fixed three bugs in dgram UDP socket creation that caused silent failures on macOS, including proper reusePort support.