@lwc/ssr-runtime

What's Changed

• synthetic-shadow: Preserve focus boundaries for empty tab segments @W-24605807 @W-24587693

What's Changed

• compiler: Clarify invalid if modifier error

What's Changed

• synthetic-shadow: Sanitize native ShadowRoot HTML sinks [W-23994661]

• ssr-compiler,ssr-runtime: Validate render() template return value

• ssr-runtime: Avoid duplicate classes in classList.replace()

• template-compiler: Treat inert as a valid global boolean attribute

What's Changed

• engine-core: Invoke compiled template via intrinsic apply behind a flag

• engine: opt-in hook for parseFragment static content [W-23814957]

• engine-dom: Guard repeat rendererFactory invocations behind a flag (W-23814927)

What's Changed

• hydration: Only hydrate components @W-23722850

• @W-23590585 fix(engine-core): only change attribute for components

• engine-core: Brand sanitized HTML by identity, not object shape (W-23680734)

• engine-core: Guard bridge element property accessors against non-public member access

What's Changed

• integration-wtr: Account for Chromium 151 empty-comment handling

• synthetic-shadow: Gate ShadowRoot undefined-methods behind a flag

• ssr-compiler: Register @api props on in-file base classes (W-23508928)

• @W-23486660 fix(synthetic-shadow): make NodeList polyfill match spec behavior

What's Changed

• engine-core: Invoke compiled template via intrinsic apply behind a flag (W-23790290) [winter27 backport]

• engine: opt-in hook for parseFragment static content (W-23814957) [winter27 backport]

• engine-dom: Guard repeat rendererFactory invocations behind a flag (W-23814927) [winter27 backport]

• hydration: Only hydrate components (W-23722850) [winter27 backport]

• engine-core: Guard bridge element property accessors against non-public member access (W-23641816) [winter27 backport]

What's Changed

• ssr: Properly handle arbitrary default exports @W-21733282

What's Changed

• Remove ENABLE_LEGACY_SIGNAL_CONTEXT_VALIDATION that hasn't been used in 3 releases

What's Changed

• Add more private method tests

• Fix attach shadow in synthetic

What's Changed

• template-compiler: Add name attribute for <details>

• Update preprocessor tag for SFCI

• engine-core: Dedupe additions to WeakMultimap @W-21387024

• @W-20806053 Implement Private Methods

Deprecations

• deprecated

  @lwc/engine-server is deprecated and won't receive further updates. Consumers should update their code to use the replacement, @lwc/ssr-runtime.

Breaking Changes

• breaking

  The main export of each package is now ESM, rather than CommonJS.

  • Beginning with v9.0.3, for compatibility purposes a CJS bundle is published for each package in dist/index.cjs.

• breaking

  The experimentalDynamicComponent option in @lwc/compiler is renamed to dynamicImports, and is no longer experimental.

• breaking

  @lwc/babel-plugin-component no longer performs import deduplication, as rollup provides the same functionality.

  • This is not a breaking change for consumers of @lwc/rollup-plugin or components on the Salesforce platform. It only impacts direct consumers of @lwc/babel-plugin-component or @lwc/compiler.

• breaking

  The type definition for wire decorators is updated. The wire function now has three type parameters, rather than four. The Context parameter was not necessary, and has been removed. Additionally, invalid @wire usage now reports errors in the correct location. Some edge cases can result in false positive errors or false negatives.

  • Reactive properties in configs are type checked, but reactive property chains are not. For example, {id: "$bookId"} will be type checked, but {id: "$book.id"} will not (it will always be permitted).

  • Config values typed as string cannot provide type checking for reactive properties. For example, {str: "$notString"} will be permitted, even if notString is not a string property on the component.

  • To avoid unnecessarily large type unions, only objects can be used at the top level of a property chain. This excludes valid edge cases, like "$myString.length".

  • To avoid unnecessarily large type unions, properties from LightningElement are excluded. This excludes valid edge cases, like "$hostElement.childElementCount".

  • To avoid false positive errors, use a getter prop or a type assertion, such as "$myObj.myProp" as Component["myObj"]["myProp"].

  • For full details, view the pull request that introduced the change.

Other Changes

• Packages now leverage engines.node to warn when using old versions of Node.js. The officially supported Node.js versions remain the LTS releases, currently v22 and v24.

• Type definitions are now published using TypeScript v6.

• All imports from Node's built-in modules now use the node: protocol.