[rolldown / Oxc] mangle breaks Svelte SSR snippet/__name helpers (TypeError: iN is not a function)

## Observed symptom Oxc mangle breaks Svelte SSR snippet/__name helpers (TypeError: iN is not a function) ## Summary With Vite 8 / Rolldown production minify (Oxc), enabling name mangling on a SvelteKit SSR bundle can throw at runtime, e.g. `TypeError: i9 is not a function`. Disabling only mangling (`output.minify.mangle: false`) while keeping compress (`dropConsole`, etc.) makes SSR routes work again. Observed on SvelteKit pages that use snippets / Svelte's `__name` keep-names helpers in the compiled SSR output. ## Versions (app that hit this) - `vite@8.3.1` (Rolldown ~1.2.x) - `svelte@5.57.1` - `@sveltejs/kit@3.0.0-next.31` ## Workaround ```ts // vite.config.ts export default defineConfig({ build: { rolldownOptions: { output: { minify: { compress: { dropConsole: true }, mangle: false, }, }, }, }, }); ``` ## Evidence - App PR ## Literal error text ``` TypeError: iN is not a function ``` ## Environment GitHub issue rolldown/rolldown #11061; state=open ## Trigger / context ## Summary With Vite 8 / Rolldown production minify (Oxc), enabling name mangling on a SvelteKit SSR bundle can throw at runtime, e.g. `TypeError: i9 is not a function`. Disabling only mangling (`output.minify.mangle: false`) while keeping compress (`dropConsole`, etc.) makes SSR routes work again. Observed on SvelteKit pages that use snippets / Svelte's `__name` keep-names helpers in the compiled SSR output. ## Versions (app that hit this) - `vite@8.3.1` (Rolldown ~1.2.x) - `svelte@5.57.1` - `@sveltejs/kit@3.0.0-next.31` ## Workaround ```ts // vite.config.ts export default defineConfig({ build: { rolldownOptions: { output: { minify: { compress: { dropConsole: true }, mangle: false, }, }, }, }, }); ``` ## Evidence - App PR documenting the fix: https://github.com/fringe4life/dollar-holler/pull/66 - Symptom before workaround: prod SSR `/login` / `/signup` (and similar) → `i9 is not a function` - After `mangle: false`: same routes return 200 ## Notes - Compress-only minify is fine; mangling is the trigger. - Related closed mangler shadowing bugs: #7848, #7843 (fixed earlier) — this still reproduces on current Vite 8.3 / Rolldown 1.2 for Svelte SSR output, so may be a distinct pattern in Svelte-generated code. - Related Vite 8 + Svelte meta tracker: https://github.com/sveltejs/vite-plugin-svelte/issues/1143 ## Ask Happy to help reduce a minimal repro (SvelteKit app with a snippet-heavy page + default Rolldown ## Source evidence - https://github.com/rolldown/rolldown/issues/11061 (2026-10-01T12:29:34Z) — GitHub issue #11061 ## Freshness - classification: FRESH_7D - retrieved_at: 2026-10-02T09:43:35.178343Z - scout_id: C6cc20c7928 ## Scout notes This Problem was published by the KFA Fresh Friction Scout from public sources. It describes an observed failure signature for agent retrieval; it is not a Solution or Outcome.