This week in Oxc

[Boshen]

This thread serves as our weekly update channel for sharing project developments with the community.

Click the subscribe button on the right for updates.

For inquiries, please find me on Discord, x, bluesky, or use the Void Zero reach out form.

---

Click Newest to see the latest update.

[Boshen]

2025 Mar 31 Week 14

Oxlint v0.16.5

@camchenry reduced the binary size from 6.32 MB to 5.8 MB by removing documentation texts.

Oxlint plugin written in JS

@Boshen and @overlookmotel are researching and gathering the requirements for custom JavaScript custom plugins, tracking in #9905

Formatter

@Boshen and @leaysgur started a new oxc_formatter crate, where the foundation is based on Biome's formatter. @Boshen is filling in formatting implementations.

ESTree compatibility

@overlookmotel, @leaysgur and @therewillbecode are aligning our Typescript ESTree to typescript-eslint's implementation. Currently passing 75% test cases.

Note our JS ESTree is 100% compatible with acorn's output.

Better and smaller Allocator Vec implementation

@Dunqing is working on a side project to change oxc_allocator's vec implementation, the current version is an outdated std::vec version exposed by bumpalo. The next step is to reduce AST memory consumption and improve performance by replacing u64 fields with u32.

Minifier

Progress has stopped since the alpha version.

[Boshen]

2025 Apr 7 Week 15

Oxlint plugin written in JS

We started a discussion to gather requirements: Oxlint plugin written in JS.

@Boshen and @overlookmotel will decide on the prototype and roadmap this week.

Formatter

@Boshen continues to work on the formatter, passing js 61/645 (9.46%) and ts 20/573 (3.49%) in the prettier conformance suite.

Transformer

@Dunqing improved Oxc's TypeScript semantic data to resolve several outstanding transform issues. PR stack: #10343

Language Server

@Sysix is refactoring the language server's code to enable import plugin: #10268

Switched the unmaintained tower-lsp crate to a a community fork tower-lsp-server: #10298

[Boshen]

2025 Apr 14 Week 16

Oxlint plugin written in JS

@Boshen and @overlookmotel started working on the initial prototype, learning and researching napi and node.js worker threads.

Formatter

@Boshen continues to work on the formatter, passing js js 61/645 (9.46%) -> 189/699 (27.04%) and ts 20/573 (3.49%) -> 110/573 (19.20%) in the prettier conformance suite.

ESTree compatibility

TypeScript estree conformance increased from 75% to 9097/10725 (84.82%). Thank you @leaysgur for reporting where the incompatibilities are.

Transformer

@Dunqing continues to fix issues reported from Rolldown.

[Boshen]

2025 Apr 21 Week 17

Oxlint plugin written in JS

• Started a small prototype that interacts with napi: https://github.com/oxc-project/oxc/tree/napi
• Concluded that we need to use ast tools to generate a more efficient ast walker, to replace https://github.com/oxc-project/oxc-walker

ESTree compatibility

TypeScript estree conformance increased from 9097/10725 (84.82%) to 6458/6493 (99.46%). All remaining issues are tracked in #9705 (comment)

Transformer

Added alignment to TypeScript's useDefineForClassFields: false. Need to set both set_public_class_fields and remove_class_fields_without_initializer to true.

See issue and PR stack

• assumptions.setPublicClassFields doesn't fully simulate tsconfig useDefineForClassFields #9192
• feat(transformer/typescript): support removeClassFieldsWithoutInitializer option #10576

Formatter

No progress.

Parser

~5% performance improvement

• perf(parser): remove -> Result<T> from all parsing methods #10588

[Boshen]

2025 Apr 28 Week 18

Oxlint plugin written in JS

No progress.

Formatter

@Boshen continues to work on the formatter, passing 189/699 (27.04%) -> 236/699 (33.76%) and ts 110/573 (19.20%) -> 143/573 (24.96%) in the prettier conformance suite.

ESTree compatibility

TypeScript estree conformance increased from 6458/6493 (99.46%) to 6478/6481 (99.95%).

Achieving ESTree compatibility is leading to a prettier plugin with oxc parser, which is almost complete and waiting to be released.

Transformer

• perf(transformer): faster UID generation #10759 (22% performance improvement)

[Boshen]

2025 May 5 Week 19

Parser

3% performance improvement

• perf(parser): Explore packed tokens #10933

Oxlint 1.0

We are working towards oxlint v1.0. @camc314 and @Sysix are fixing issues for stability.

Oxlint plugin written in JS

No progress.

Formatter

No progress. @Dunqing will pick up the formatter starting from this week.

ESTree compatibility

Most works are done. We now have a working prettier plugin: https://github.com/ArnaudBarre/prettier-oxc-parser waiting for 1.0.

[Boshen]

2025 May 12 Week 20

Parser

2% performance improvement

• feat(allocator/vec2): change len and cap fields from usize to u32 #10884

Oxlint 1.0

@camc314 released oxlint v0.16.11, and is continuing to stabilize the linter for 1.0.

Formatter

@Dunqing started working on the formatter. js 245/699 (35.05%)-> 257/699 (36.77%) ts 157/573 (24.96%) -> 180/573 (31.41%)

ESTree compatibility

All work are done, prettier is integrating oxc parser, with a few blocking issues. PR: https://github.com/prettier/prettier/pull/17472

Resolver

knip adopted oxc-resolver, increased its weekly download count to over 1.3 million. PR: https://github.com/webpro-nl/knip/pull/1081

[Boshen]

2025 May 19 Week 21

Oxlint 1.0

Released oxlint v0.16.12, we continue to stabilize the linter for 1.0.

Parser

We intend to improve the parser by:

• Custom arena allocator #11145
• parser: use checkpoints instead of token lookahead #11194

Formatter

@Dunqing finished printing BinaryExpression and LogicalExpression, js 257/699 (36.77%) -> 281/699 (40.20%), ts 180/573 (31.41%) -> 181/573 (31.59%).

[Boshen]

2025 May 26 Week 22

Oxlint v1.0

Final v0.17.0 release. Now in feature freeze phase until final v1.0 release.

Parser

• parser: reduce unnecessary backtracking #11334 Found a lot of performance improvements

Formatter

@Dunqing continues to work on the formatter.

estree conformance

@overlookmotel completed conformance testing and fixed problems that would block prettier adopting oxc.

[Boshen]

Week 23

Oxlint v1.0

Oxlint 1.0 today.

Oxlint plugin written in JS

We have a consensus on what to build, will release roadmap when it is ready.

Formatter

@Dunqing is rearchitecting the formatter

• refactor(formatter): core revamp #11511

codegen

We are seeking an solution for estree codegen

• estree codegen #11495

[Boshen]

Week 24

Oxlint

Announced Oxlint 1.0 https://voidzero.dev/posts/announcing-oxlint-1-stable

Formatter

@Dunqing is working on supporting comments #11716

Oxlint JS Custom plugin

@camc314 started working on the prototype. First step is to pass a memory buffer created in js to Rust, for raw transfer.

Parser

@leaysgur is looking for ways to improve our ts parser error story

• parser: Improve TS error story #11582

[Boshen]

Week 25

Oxlint plugin written in JS

@overlookmotel completed JS-side Lazy AST visitor.

@overlookmotel did a few benchmarks and concluded that the ESLint custom plugin API can work, with an acceptable performance overhead.

@camc314 started bridging the gap between Rust and JS:

• feat(oxc_linter): reuse allocators #11736
• feat(linter): read source text into the arena #11825
• feat(linter): use oxlint via napi #11779
• feat(napi): bundle napi/parser with tsdown #11833

Formatter

@Dunqing finished the architecture for printing comments

• 06-15-feat_formatter_support_printing_comments

Parser

@leaysgur is helping out on improving our ts error story

• parser: Improve TS error story #11582
• https://github.com/leaysgur/oxc-tsc-fixtures

Minifier

@Boshen started working on Minifier beta

Made a few PRs to test and think about the architecture:

• feat(minifier): remove unused variable declaration #11796
• feat(minifier): treat variable declarations with only read references as const #11804
• feat(minifier): inline and evaluate constant values #11819
• feat(minifier): remove symbol references when code is removed #11820

[Boshen]

Week 26

Oxlint plugin written in JS

@camc314 landed

• feat(napi): add basic oxlint napi bindings #11877

Formatter

@Dunqing continues to work on the formatter

js 324/699 (46.35%) ->342/699 (48.93%)
ts 200/573 (34.90%) -> 210/573 (36.65%)

Minifier

No progress.

Parser

@leaysgur continues to work on

• parser: Improve TS error story #11582
• refactor(coverage/typescript): Use regex to capture TSxxxx error codes #11932
• test(coverage/typescript): Update TS18xxx error codes handling #11933

[Boshen]

Week 27

Oxlint plugin written in JS

@overlookmotel and @camc314 are bridging the gaps between the Rust and JavaScript side, including adding napi related logic to linter crates, and support transfer of AST to JS using raw transfer.

Formatter

• js 342/699 (48.93%) -> 387/699 (55.36%)
• ts 210/573 (36.65%) -> 219/573 (38.22%)

Progress will be stalled this week. @Dunqing is working in

• transformer: babel-plugin-styled-components #11876

Parser

• feat(ast): add range field to custom serializers #11890

Codegen

• fix(codegen): escape </script #11782

Minifier

No progress.

[Boshen]

Week 28

Oxlint plugin written in JS

JS and Rust sides are now connected through napi. API for reporting diagnostics is implemented.
Next step is to walk ast and measure performance.

Transformer

@Dunqing added basic support for styled-components

• feat(transformer): support styled components plugin #12066

Formatter

No progress.

Minifier

No progress

[Boshen]

Week 29

Type Aware Linting

• https://github.com/oxc-project/tsgolint
• feat(oxlint): experiment: add tsgolint integration #12343

Oxlint plugin written in JS

First prototype of linter JS plugins is complete.
Note: This prototype is a proof of concept rather than ready to release

• feat(napi/oxlint): pass AST in buffer to JS #12350
• ☂️ Oxlint Custom JavaScript Plugin Milestone 1 #9905 (comment)

Minifier

@Boshen added a few changes:

• feat(minifier): remove unused variable declaration #11796
• feat(minifier): remove unused function declaration #12318
• feat(minifier): constant fold small integer multiplication (n <= 255) #12236
• feat(minifier): remove unused -1n #12235

Codegen

Investigated Rolldown memory issues, discovered many inefficient code around sourcemap:

• perf(codegen): remove clone of source text in sourcemap builder #12393
• perf(codegen): replace loop + push with std::iter::repeat #12398
• perf: reduce size of token from 32 bytes to 24 oxc-sourcemap#86
• perf: return &Arc<str> instead &str for source content oxc-sourcemap#88
• codegen: align sourcemap generation with esbuild #12395

Formatter

@Dunqing fixed many issues with comment checking and comments being attached to incorrect places. Another ongoing task is refactoring the call argument to better fit the current architecture.

js 387/699 (55.36%) -> 3413/699 (59.08%)
ts 219/573 (38.22%) -> 234/573 (40.84%)

[Boshen]

2025 Aug Week 31

We started using GitHub Copilot Agent, landed some PRs:

• https://github.com/oxc-project/oxc/pulls?q=is%3Apr+author%3A%40copilot+is%3Amerged+

Type Aware Linting

• No progress this week. @Boshen will resume next week. It is currently blocked by monorepo support.

Oxlint plugin written in JS

This week @overlookmotel researched and built a prototype for running parsing and JS-side AST visitation in multiple threads. It confirmed that lazy deserialization is far more amenable to parallelization than the standard approach (eager deserialization). Lazy deserialization is both faster in itself (by approx 3x), and also scales better across multiple threads.

Formatter

@Dunqing

js 440/699 (62.95%) -> 472/699 (67.53%)
ts 244/573 (42.58%) -> 247/573 (43.11%)

Minifier

• feat(minifier): inline small constant values #12639
• feat(minifier): remove unnecessary 'use strict' directive #12642
• feat(minifier): remove unused class expression #12618

[Boshen]

2025 Aug Week 32

More GitHub Copilot Agent involvement, landed an MCP boierplate, need ideas to what to put in it though.

• feat(tasks): Add MCP boilerplate with echo command to tasks/mcp #12925
• https://github.com/oxc-project/oxc/pulls?q=is%3Apr+author%3A%40copilot+is%3Aclosed+is%3Amerged

Type Aware Linting

Released oxlint --type-aware

• feat(oxlint): add tsgolint integration #12485

Blocked by

• Performance issue with project service tsgolint#67

Waiting for

• feat(linter): Add 36 new TypeScript ESLint rules with comprehensive test fixtures #12893

Oxlint plugin written in JS

@overlookmotel To be updated.

Formatter

@Dunqing

JavaScript | 472/699 (67.53%) -> 505/699 (72.25%)
TypeScript | 247/573 (43.11%) -> 250/573 (43.63%)

Minifier

• feat(minifier): logical assignment with sequential #12957
• feat(minifier): remove optional chaining calls when the function is undefined or null #12956

[Boshen]

2025 Aug Week 32

Type Aware Linting

Announced Oxlint Type-Aware Preview

Oxlint plugin written in JS

@overlookmotel working on integrating multi-threaded JS plugins prototype into oxlint.

Formatter

@Dunqing

JavaScript | 505/699 (72.25%) -> 560/699 (80.11%) | +55 tests (+7.86%)
TypeScript | 250/573 (43.63%) -> 303/573 (52.88%) | +53 tests (+9.25%)

Minifier

• feat(minifier): mark more known global methods as side-effect free #13086
• fix(minifier): keep Array reference id when compressing Array() #13113
• feat(minifier): compress Object(expr)(args) to (0, expr)(args) #13092

AI involvement

Added https://github.com/oraios/serena MCP server to aid GitHub Copilot

• 7e15446
• ci: Implement parallel submodule cloning for faster CI/CD performance #13045

[Boshen]

2025 Aug Week 33

Type Aware Linting

We plan to rewrite the architecture to support typed linting at scale

• RFC: Performant typed linting at scale tsgolint#107

Oxlint plugin written in JS

See update

• ☂️ Oxlint Custom JavaScript Plugin Milestone 1 #9905 (comment)

Formatter

JavaScript | 560/699 (80.11%) -> 620/699 (88.70%) | +60 tests (+8.59%)
TypeScript | 303/573 (52.88%) -> 329/573 (57.42%) | +26 tests (+4.54%)

• feat(oxfmt): Add apps/oxfmt crate with minimum formatting usage #13259

[Boshen]

2025 Aug Week 34

Trusted Publishing

In response to recent events:

• https://socket.dev/blog/nx-packages-compromised
• https://socket.dev/blog/npm-is-package-hijacked-in-expanding-supply-chain-attack
• https://socket.dev/blog/toptal-s-github-organization-hijacked-10-malicious-packages-published
• https://socket.dev/blog/npm-phishing-campaign-leads-to-prettier-tooling-packages-compromise
• https://socket.dev/blog/npm-phishing-email-targets-developers-with-typosquatted-domain
• https://socket.dev/blog/supply-chain-attack-on-lottie-files-player
• https://socket.dev/blog/ultralytics-pypi-package-compromised-through-github-actions-cache-poisoning

Trusted publishing has been enabled for all npm packages and cargo crates within the oxc-project organization. We no longer store any long lived npm tokens. @Boshen does not have any long lived tokens and will not issue out any.

See

• https://github.blog/changelog/2025-07-31-npm-trusted-publishing-with-oidc-is-generally-available
• https://docs.npmjs.com/trusted-publishers

for details.

Type Aware Linting

@camc314 completed a new infra for linting at scale

• refactor: remove use of project service tsgolint#139

Oxlint plugin written in JS

@overlookmotel:

• Added conversion to/from UTF-16 offsets (start and end) in JS-side AST, and in errors passed back to Rust. feat(linter): convert spans to UTF-16 in JS plugins #13344
• Continued work merging plugins prototype into Oxlint proper.

Formatter

JavaScript | 620/699 (88.70%) -> 645/699 (92.27%)
TypeScript | 329/573 (57.42%) -> 331/573 (57.77%)

#13383

Minifier

@sapphi-red continues to improve the minifier

• https://github.com/oxc-project/oxc/pulls?q=is%3Apr+is%3Aclosed+label%3AA-minifier

We now ranked highly on https://github.com/privatenumber/minification-benchmarks

[Boshen]

2025 Sept Week 35 - 36

Type Aware Linting

@camc314 continues to improve tsgolint aiming for stableness.

Oxlint plugin written in JS

@overlookmotel started preparing the current prototype for a demo release.

See latest update #9905 (comment)

Formatter

https://www.npmjs.com/package/oxfmt is released.

@leaysgur is working on Formatter Alpha https://github.com/oxc-project/oxc/milestone/14

@Dunqing continues work on formatting algorithms.

Linter

@camchenry made some break throughs that speeds up the linter by a significant amount, from 5 to 50%:

• perf(linter): skip rules that do not have any relevant node types #13138
• perf(linter): detect node types from let..else statements #13690