vue-tsc 3.3.12 TS2300 Duplicate $style: Should You Upgrade?

No affiliate links. After I upgraded a scratch project to vue-tsc 3.3.12, a fixture with two <style module> blocks both defining .a threw TS2300 Duplicate identifier '$style'—the same file on 3.3.11 showed 0 diagnostics. This post is the upgrade decision for Vue teams: when that new diagnostic (and the rest of Vue Language Tools v3.3.12 / npm vue-tsc@3.3.12) is worth the bump, and how to fix the CSS-module clash. Nothing in ShopperCove’s production build was changed for this article.

Should you upgrade to vue-tsc 3.3.12?

Yes if you use multiple <style module> blocks in one SFC, typed defineModel default factories, or open untrusted .vue samples in the editor. Wait if you are mid-freeze on 3.3.11 with a clean typecheck and no CSS modules / defineModel factory edge cases—skim the release notes and pin when you next open a Vue branch.

npm published vue-tsc 3.3.12 at 2026-10-02T09:28:35Z (14:58 IST). The GitHub release tag went up at 16:54 UTC the same day (22:24 IST).

What actually shipped (2 Oct 2026)

language-core

• security: improved handling of untrusted Vue files (cea0698)
• feat: infer the first parameter type of the default factory for defineModel (1be73b8)
• feat: report duplicate CSS module names, including non-identifier names
• fix: keep union props when using withDefaults; keep inference-only props strings single-line with block comments
• fix: support calling template bindings without .value
• fix: pad directive hook signatures for short-arity directive bindings; vueCompilerOptions.plugins now overrides the inherited list instead of being deduplicated on resolve
• fix: eliminate synthesized ignore comments across codegen / scoped class aliases / compound handlers; correct template mapping boundaries; stop typedef JSDoc leaking into emitted .d.ts
• perf: precompile attribute glob matchers

Other packages

• component-meta: stop checking JS Vue files as TS
• typescript-plugin: don’t abort reference span fix-up on style-less files
• tsc: prevent watch-mode crash on incremental build
• vscode: reduce focus-mode overhead

ShopperCove smoke test: 3.3.12 vs 3.3.11

On 5 Oct 2026 we installed vue-tsc@3.3.12 and vue-tsc@3.3.11 (with vue@3.5 and typescript@5.9) in separate scratch folders and ran vue-tsc --noEmit.

Fixture	3.3.11	3.3.12
Two <style module> blocks both defining .a	0 diagnostics	TS2300 Duplicate identifier '$style' (twice)
defineModel({ default: (props: { count: number }) => props.missing })	(not compared)	TS2339 on missing — factory param typing holds
Template {{ fn() }} where fn = ref(() => 1)	(clean on both in our run)	No forced .value error (matches the 7ad4a94 fix)

Treat this as one box’s smoke test, not a full regression suite. The duplicate CSS-module diagnostic is the clearest day-one reason to bump if you use multiple <style module> blocks in one SFC.

How to fix TS2300 Duplicate identifier $style

1. Search the SFC for more than one <style module> (or <style module="…">) block that both inject $style.
2. Merge into a single <style module> block, or give modules distinct names and stop relying on the default $style binding for both.
3. Re-run vue-tsc --noEmit on the branch after pinning 3.3.12.
4. Expect tighter defineModel default-factory typing next—fix props.missing-style typos the new inference catches.
5. If you open untrusted .vue files in the editor, note the security hardening around untrusted SFCs.

Upgrade checklist

1. Pin vue-tsc@3.3.12 (and matching Vue Language Tools / Volar build) on a branch.
2. Run vue-tsc --noEmit across the app. Expect new diagnostics on duplicate CSS module names and tighter defineModel default-factory typing.
3. If watch-mode vue-tsc used to crash on incremental rebuilds, re-test after the bump (a59da36).
4. Extension installs: Open VSX Vue / volar returned 200 from this network on 5 Oct 2026.

Bottom line

Should you upgrade? If you ship Vue SFCs with CSS modules or typed defineModel factories, yes—ShopperCove’s DupCss fixture went from 0 diagnostics on 3.3.11 to TS2300 on 3.3.12, which is exactly the bug you want the compiler to catch before production. Pin, typecheck, fix the first $style clash, and skim the security note for untrusted SFCs. No affiliate.

Sources

• 01registry.npmjs.org/vue-tsc/3.3.12
• 02github.com/vuejs/language-tools
• 03github.com/vuejs/language-tools/blob/master/CHANGELOG.md
• 04vuejs.orghttps://vuejs.org/

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