[suasgn]

Summary

@tailwindcss/oxide-wasm32-wasi only has a threaded wasm32-wasip1-threads build. In browsers it needs SharedArrayBuffer, which is only available on cross-origin isolated pages (COOP/COEP headers), so the scanner can't run on most pages.

This adds a separate single-threaded wasm32-wasip1 build for browsers:

• browser.mjs loads it with non-shared memory and scans an in-memory filesystem (memfs), exported as __fs and __volume. Scanning runs on the calling thread.
• The pinned NAPI CLI only builds wasm32-wasip1-threads, so scripts/build-browser.mjs builds the module with Cargo directly, and build.rs links emnapi's single-threaded archive. The script reads the artifact path from Cargo's JSON output, and fails the build when the module doesn't link against the memory that browser.mjs creates.
• The browser field of @tailwindcss/oxide-wasm32-wasi now points to browser.mjs, and the package ships types (index.d.ts, browser.d.mts). The threaded browser loader (tailwindcss-oxide.wasi-browser.js, wasi-worker-browser.mjs) is still published, so code that imports it by path, for example on cross-origin isolated pages, keeps working.
• @tailwindcss/oxide gets a browser entry that re-exports the browser build.
• build now runs build:browser, so CI, the release workflows and CONTRIBUTING.md install the wasm32-wasip1 target.

The Node.js and native builds are unchanged.

Related

• Addresses the browser part of Oxide as WASM Module? #11610: using Oxide on play.tailwindcss.com, and the SharedArrayBuffer errors when loading @tailwindcss/oxide-wasm32-wasi in a browser. The edge runtimes from the original question (e.g. Deno Deploy) are not tested.
• An alternative to Feat: Adds rust config options to detect threading support in oxide #18292, which builds crates/oxide for wasm32-unknown-unknown with wasm-bindgen. This PR does not change the scanner code, because Rayon runs on the calling thread on wasm32-wasip1. It exposes the same Scanner API as Node.js instead of separate Wasm* types, and supports scan() over memfs. A wasm32-unknown-unknown build without the WASI runtime may be smaller.

Test plan

• pnpm --filter @tailwindcss/oxide test:ui: new Playwright tests (Chromium, Firefox, WebKit) serve the bundled entry without COOP/COEP headers. They check candidate extraction, UTF-16 positions, memfs discovery with incremental rescans, and use from an application-owned worker. One test makes Worker throw, to check that the build never creates workers.
• pnpm test:integrations ./integrations/oxide/wasm.test.ts: a new test loads the browser entry of the packed package in Node.js with SharedArrayBuffer removed.
• pnpm --filter @tailwindcss/oxide build:browser, with the default target directory and with CARGO_BUILD_TARGET_DIR set to another directory. Both copy the fresh module.
• Linked the module against memory that is too small, and against shared memory, to check that the build rejects both.
• cargo check --target wasm32-wasip1 -p tailwind-oxide works without EMNAPI_LINK_DIR.

🤖 Generated with Claude Code

[greptile-apps]

Confidence Score: 5/5

[Medium impact] The reviewed changes appear safe to merge.

_{Reviews (5) · Last reviewed commit: "Load the browser build asynchronously an..." · Reviewed by Greptile}

[coderabbitai]

Walkthrough

The change adds a single-threaded wasm32-wasip1 browser build for oxide. It adds a browser loader that initializes WASI, fetches and instantiates the WASM module, and exports the scanner and in-memory filesystem. Package metadata, declarations, build workflows, and artifact handling are updated for the new entry point. Playwright and integration tests cover browser scanning without cross-origin isolation or SharedArrayBuffer.

Merge Risk: Low · up to 07611

TypeScript browser consumers need a workaround to import the virtual filesystem from the package root.

Pre-merge checks: 4

Check name	Status	Explanation
Title check		The title clearly summarizes the main change: adding a single-threaded browser build of Oxide.
Description check		The description explains the browser build, its implementation, package changes, and test plan. It is directly related to the changeset.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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[coderabbitai]

Actionable comments posted: 1

Review info

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Reviewing files that changed from the base of the PR and between 8093f21 and db0c97f.

Files selected for processing: 3

• crates/node/npm/wasm32-wasi/README.md
• crates/node/npm/wasm32-wasi/package.json
• crates/node/scripts/move-artifacts.mjs

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[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to GitHub limitations.

⚠️ Outside diff range comments (1)

Minor · Route browser root imports to browser types. · package.json:10

crates/node/package.json:10
Minor · Functional Correctness · Quick win

Route browser root imports to browser types.

TypeScript consumers importing __fs or __volume from @tailwindcss/oxide get missing-export errors, even when their bundler selects the browser entry. Provide browser-conditional type routing for consumers that enable the browser condition, while keeping the Node root on index.d.ts.

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Reviewing files that changed from the base of the PR and between db0c97f and 076119e.

Files selected for processing: 3

• crates/node/build.rs
• crates/node/npm/wasm32-wasi/README.md
• crates/node/npm/wasm32-wasi/browser.mjs

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• crates/node/npm/wasm32-wasi/README.md

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