Deno v2.9.0 — Release Notes & Engineering Impact

### 2.9.0 / 2026.06.25 Read more: http://deno.com/blog/v2.9 - feat(bundle): add --declaration flag to generate rolled-up .d.ts files (#33838) - feat(cli): add `deno link` and `deno unlink` subcommands (#34359) - feat(cli): add `deno watch` subcommand (#35301) - feat(cli): add deno list subcommand to list declared dependencies (#34972) - feat(cli): auto-migrate pnpm-workspace.yaml on resolution failure (#34993) - feat(cli): provide a `node` on PATH when Node.js is not installed (#34969) - feat(compile): persist Web Storage/KV in a per-app data directory (#34618) - feat(coverage): add configurable coverage thresholds (#35056) - feat(desktop): --compress for self-extracting app bundles (#35420) - feat(desktop): add Linux .deb and .rpm installer output formats (#35296) - feat(desktop): add Windows .msi installer output format (#35378) - feat(desktop): autodetect Vite framework (#35470) - feat(desktop): default UI backend to webview (#35442) - feat(ext/crypto): support remaining modern WebCrypto algorithms (#35223) - feat(ext/http): deprecation warning for legacy request abort (#34397) - feat(ext/net): implement Happy Eyeballs for `Deno.connect` and `Deno.connectTls` (#31726) - feat(ext/node): implement node:test mock.module (#35329) - feat(ext/node): implement node:test mock.timers (#33946) - feat(ext/web): web locks api (#31166) - feat(fmt): add sortNamedImports and sortNamedExports options (#33313) - feat(fmt): infer config from .editorconfig (#34071) - feat(fmt): use lax-css for CSS, SCSS, and Less (#35160) - feat(fmt): use lax-markup for HTML, XML, SVG, and components (#35174) - feat(fmt): use lax-sql for SQL formatting (#35161) - feat(http): allow disabling serve compression (#35253) - feat(http): disable Deno.serve automatic compression by default (#35486) - feat(install): create node_modules for workspace members (#34970) - feat(install): seed deno.lock from bun.lock (#35394) - feat(install): seed deno.lock from package-lock.json (#35330) - feat(install): seed deno.lock from pnpm-lock.yaml (#35346) - feat(install): seed deno.lock from yarn.lock (#35350) - feat(install): warn on package.json engines mismatch (#34225) - feat(lockfile): auto-resolve git merge conflicts in deno.lock (#34726) - feat(lsp): add inferred type request (#35099) - feat(napi): implement Node-API version 10 (#35270) - feat(node): bump reported process.version to v26.3.0 (#34747) - feat(npm): install jsr deps into node_modules via npm-compat registry (#35029) - feat(npm): publishing-trust ranking and no-downgrade trust policy (#34927) - feat(runtime): add request_builder_hook for fetch token and cdn-loop headers (#35088) - feat(task): add --if-present flag to deno task (#35315) - feat(task): add --jobs/--concurrency flag to deno task (#35318) - feat(task): input-based caching with files/output/env (#34509) - feat(task): set npm_execpath, npm_node_execpath and npm_command for package.json scripts (#35317) - feat(test): add --changed and --related flags to deno test (#35199) - feat(test): add --shard flag to split a test run across machines (#35057) - feat(test): add Deno.test.each for parameterized tests (#34938) - feat(test): add retry and repeats options to Deno.test (#35053) - feat(test): built-in snapshot testing via t.assertSnapshot (#35139) - feat(test): show sub-millisecond test durations (#35200) - feat(unstable): CSS module imports (with { type: "css" }) (#35093) - feat: `deno desktop` subcommand (#33441) - feat: `deno remove --global` as alias for `deno uninstall --global` (#35327) - feat: add "preferPackageJson" deno.json setting (#35392) - feat: add stable --unsafe-proto flag (#34738) - feat: enable default minimum dependency age (#35458) - feat: stabilize "links" field in deno.json (#34996) - feat: stabilize bare node built-in resolution (#33316) - feat: support `ignore` option in `Deno.watchFs` (#31582) - feat: support navigator.userAgentData (#34743) - fix(check): treat npm .d.ts as CJS based on package.json (#35166) - fix(core): always register isolate to prevent silent foreground task drop (#35408) - fix(core): don't cache WebIDL sequence keys in thread-local v8::Eternal (#35462) - fix(core): handle async op promise id wraparound (#35126) - fix(core): make uv_compat ready queues thread-safe (#35175) - fix(core): preserve custom .stack getters in error/test formatter (#35246) - fix(core): unwrap global exports in Wasm ESM integration (#34912) - fix(coverage): don't panic in summary reporter without a common root (#35211) - fix(coverage): merge coverage for modules loaded with different hash/search params (#35354) - fix(deploy): use JSR latest for deploy CLI (#35493) - fix(desktop): Wayland support for CEF and webview backends (#35425) - fix(desktop): add Bluetooth usage descriptions to macOS Info.plist (#35472) - fix(desktop): add macOS desktop Info.plist keys (#35484) - fix(desktop): correct libdenort unpack path with non-executable extension (#35267) - fix(desktop): hide bundled libc++ symbols so the desktop runtime can be dlopen'd on Linux (#35424) - fix(desktop): use native Wayland instead of XWayland on Wayland systems (#35485) - fix(ext/crypto): allow deriving AES-OCB keys (#35426) - fix(ext/crypto): clamp X448 scalar per RFC 7748 (#35157) - fix(ext/crypto): pad JWK to multiple of 8 bytes for AES-KW wrap (#35475) - fix(ext/fetch): keep content-encoding and content-length on decompressed responses (#35124) - fix(ext/fetch): require --allow-net for Unix proxy in createHttpClient (#35231) - fix(ext/fs): truncate should not follow a terminal symlink (#35239) - fix(ext/http): apply automatic compression for zero-arg serve handlers (#35490) - fix(ext/http): close active WebSockets on Deno.serve shutdown (#35105) - fix(ext/kv): validate remote KV URL when opening the connection (#35106) - fix(ext/napi): restore Explicit microtask policy in napi_resolve_deferred (#35212) - fix(ext/net): cancel in-flight reads when closing TCP/Unix/Vsock streams (#35294) - fix(ext/net): set transport on address for TlsListener (#35258) - fix(ext/node): allow registerHooks with no resolve or load hook (#35235) - fix(ext/node): avoid panic deserializing empty buffers over child_process IPC (#35340) - fix(ext/node): avoid panic when vm.SourceTextModule uses import.meta (#35375) - fix(ext/node): check --allow-net for proxied request target in node:http(s) (#35241) - fix(ext/node): don't apply requestTimeout to active streaming responses (#35291) - fix(ext/node): fail node:test on unhandled rejection and enforce timeout (#35297) - fix(ext/node): fix `node:test` hook ordering and error handling (#35393) - fix(ext/node): forward permissions when spawning deno with subcommand args (#35443) - fix(ext/node): implement process.resourceUsage() (#35468) - fix(ext/node): implement t.assert.fileSnapshot for node:test (#35478) - fix(ext/node): implement test.TestContext.runOnly (#35158) - fix(ext/node): implement worker_threads.isInternalThread (#35234) - fix(ext/node): import attributes and custom module types in registerHooks ESM hooks (#35028) - fix(ext/node): initialize named stdio exports lazily (#35428) - fix(ext/node): keep dns.lookup permission token internal (#35224) - fix(ext/node): make registerHooks resolve hook work for nested imports (#35169) - fix(ext/node): preserve AsyncLocalStorage context across node:net callbacks (#35237) - fix(ext/node): restore Node binding signature for zlib write/writeSync (#35238) - fix(ext/node): single source of truth for emulated Node version (#35273) - fix(ext/node): stop coloring non-TTY streams in `util.styleText` (#35236) - fix(ext/node): support AbortSignal.timeout in node:test mock.timers (#35474) - fix(ext/node): support HTTP/2 on the DENO_SERVE_ADDRESS override listener (#35089) - fix(ext/node): trace v8 serializer delegate (#35132) - fix(ext/signals): build windows-sys only on Windows (#35283) - fix(install): remove stale root node_modules symlink on deno remove (#35137) - fix(install): resolve package.json dependencies in global install (#35135) - fix(install): seed pnpm workspace members and catalog deps (#35376) - fix(jupyter): report cell errors instead of failing silently (#35328) - fix(lsp): honor --env-file from deno.json `test` task in test runner (#34905) - fix(lsp): include tsconfig roots in script names (#34136) - fix(lsp): make requests work for files opened from node_modules (#35176) - fix(lsp): report TS2307 for unresolved imports in .d.ts entrypoints (#35469) - fix(node): expose lazy console stdio streams (`console._stdout`/`_stderr`) (#35488) - fix(node): propagate source thread id to `process` `workerMessage` event (#35374) - fix(node/test): route nested top-level test() to a subtest (#35406) - fix(npm): avoid spurious npm re-resolution that fails under --cached-only (#35051) - fix(npm): don't apply import map to npm bin main module (#35097) - fix(npm): make peer dependency warning actionable and show importers (#35242) - fix(npm): slim cached full packument when minimumDependencyAge is set (#35285) - fix(npm): support `catalog:` protocol in deno.json imports (#35168) - fix(npm): symlink workspace npm members into root node_modules by name (#35383) - fix(pack): include assets matched by publish.include in the tarball (#35331) - fix(pack): surface slow type diagnostics (#35379) - fix(permissions): don't require --allow-run for process.kill on self (#34382) - fix(permissions): require --allow-net for Unix domain socket ops (#34395) - fix(permissions): treat Windows `\\?\` verbatim paths as equivalent (#35096) - fix(publish): continue publishing workspace after a package fails (#35133) - fix(publish): skip already-published versions before type checking (#35134) - fix(repl): highlight regex literals correctly (#35103) - fix(resolver): better hint when importing a linked package by the wrong name (#35319) - fix(resolver): resolve linked packages by bare specifier (#35228) - fix(runtime): capture blob worker roots before revocation (#35128) - fix(runtime): don't silently lose Deno.watchFs events (#35122) - fix(runtime): make Deno.test.* sub-methods no-op under `deno run` (#35344) - fix(runtime): suggest --unstable-unsafe-proto after **proto** access (#35192) - fix(serve): exit cleanly on SIGTERM/SIGINT in deno serve (#32862) - fix(serve): shut down old workers on watcher restart (#35136) - fix(serve): update request_signal_streaming spec for legacy abort warning (#35193) - fix(task): set npm lifecycle env vars when running package.json scripts (#35252) - fix(test): ignorelist leaks from sanitizer-ignoring tests (#35005) - fix(test): skip invalid doctest import bindings (#35382) - fix(test/node): mark test-worker-fshandles-open-close-on-termination as flaky (#35387) - fix(tests): skip npm/playwright_compat on windows-aarch64 (#35358) - fix(update): refetch npm metadata so stale cache doesn't hide newer versions (#35380) - fix(upgrade): stream zstd delta patch to avoid 2GiB OOM (#35284) - fix: Headers inspect for duplicate Set-Cookie values (#35461) - fix: accept U+30FB KATAKANA MIDDLE DOT in identifiers (#35147) - fix: cache 404 responses for remote modules (#35138) - perf(core): reduce snapshotted cppgc op member templates (#35298) - perf(core): skip source ASCII checks in release runtime setup (#35186) - perf(ext/crypto): port WebCrypto from JS to Rust (#34966) - perf(ext/web): port console/inspect to Rust (cppgc object wrap) (#35087) - perf(macos): enable chained fixups to cut pre-main startup (~0.8ms) (#35409) - perf(runtime): lazy-load node:buffer and node:timers globals (#35373) - perf(snapshot): guard against lazy modules leaking into eager snapshot (#35332) - perf(snapshot): minify snapshot sources (#35183) - perf(workers): incremental message-passing cleanups (#35108) - perf: V8 code cache for residual lazy-loaded ESM modules (#35338) - perf: gate eager node bootstrap to node workers (#35337) - perf: lazy-load OSX frameworks with `lzld` (#35341) - perf: startup profiling instrumentation + clap fast-path (#35263) - perf: startup time (22ms -> 15ms) (#34450)