# Deno v1.45.0 — Release & Upgrade Intelligence
- **Product:** Deno (https://deno.com)
- **Version:** v1.45.0
- **Released:** Jul 10, 2024
- **Impact Score:** 7/10
- **Breaking Changes:** Source flagged
- **Canonical Analysis:** https://changelogs.us/deno/updates/v1.45.0/

## Executive Summary (TL;DR)
Deno v1.45.0. Source highlight: BREAKING(unstable/ffi): remove callback reentrant flag (#24367)

## Breaking Changes & Deprecations
- - BREAKING(unstable/ffi): remove callback reentrant flag (#24367)

## New Features
- feat(cli): Add `--frozen` flag to error out if lockfile is out of date
- feat(cli): `deno init --lib` (#22499)
- feat(compile): support `--env` (#24166)
- feat(ext/crypto): make `deriveBits` `length` parameter optional and nullable
- feat(ext/web): add `Blob.prototype.bytes()` (#24148)
- feat(jsr): support publishing jsr packages in npm workspaces (#24507)

## Improvements
- perf(ext/node): improve `Buffer.from(buffer)` (#24352)
- perf(ext/websocket): avoid global interceptor overhead (#24284)
- perf(ws): optimize fastwebsockets in release profile (#24277)
- perf: optimize Buffer.from("base64") for forgiving-base64 conforming input

## Bug Fixes
- fix(check): CJS types importing dual ESM/CJS package should prefer CJS types
- fix(compile): atomically write compile output (#24378)
- fix(compile): prevent setting unstable feature twice (#24381)
- fix(ext/node): Add `fs.lutimes` / `fs.lutimesSync` (#23172)
- fix(ext/node): add `Module.parent` (#24333)
- fix(ext/node): add ServerResponse#appendHeader (#24216)