I post this here to help others that might have the same problem. I apologise in Advance if it is the wrong place.

PROBLEM:
I was using the @next version and then I installed a component with the new cli. After that I got those errors:

X [ERROR] Missing "./attachments" specifier in "svelte" package [plugin vite:dep-pre-bundle]

    node_modules/.pnpm/[email protected][email protected]/node_modules/svelte-toolbelt/dist/utils/attach-ref.js:3:36:

      3 │ import { createAttachmentKey } from "svelte/attachments";

        ╵                                     ~~~~~~~~~~~~~~~~~~~~

  This error came from the "onResolve" callback registered here:

    node_modules/.pnpm/[email protected]/node_modules/esbuild/lib/main.js:1150:20:

      1150 │       let promise = setup({

           ╵                     ^

    at setup (file:///C:/Sites/ViteBrowserExt/extension/StoryDrafter/node_modules/.pnpm/vite@5.4.14_@types[email protected][email protected]/node_modules/vite/dist/node/chunks/dep-CHZK6zbr.js:46935:13)

    at handlePlugins (C:\Sites\ViteBrowserExt\extension\StoryDrafter\node_modules.pnpm\[email protected]\node_modules\esbuild\lib\main.js:1150:21)

    at buildOrContextImpl (C:\Sites\ViteBrowserExt\extension\StoryDrafter\node_modules.pnpm\[email protected]\node_modules\esbuild\lib\main.js:873:5)

    at Object.buildOrContext (C:\Sites\ViteBrowserExt\extension\StoryDrafter\node_modules.pnpm\[email protected]\node_modules\esbuild\lib\main.js:699:5)

    at C:\Sites\ViteBrowserExt\extension\StoryDrafter\node_modules.pnpm\[email protected]\node_modules\esbuild\lib\main.js:2032:68

    at new Promise ()

    at Object.context (C:\Sites\ViteBrowserExt\extension\StoryDrafter\node_modules.pnpm\[email protected]\node_modules\esbuild\lib\main.js:2032:27)

    at Object.context (C:\Sites\ViteBrowserExt\extension\StoryDrafter\node_modules.pnpm\[email protected]\node_modules\esbuild\lib\main.js:1874:58)

    at prepareEsbuildOptimizerRun (file:///C:/Sites/ViteBrowserExt/extension/StoryDrafter/node_modules/.pnpm/vite@5.4.14_@types[email protected][email protected]/node_modules/vite/dist/node/chunks/dep-CHZK6zbr.js:50926:33)

X [ERROR] node_modules/.pnpm/bits-ui@2.8.10_@internationalized[email protected][email protected]/node_modules/bits-ui/dist/internal/grace-area.svelte.js:13:24 $derived(...) can only be used as a variable declaration initializer or a class field

https://svelte.dev/e/state_invalid_placement [plugin vite-plugin-svelte-module:optimize-svelte]

    node_modules/.pnpm/bits-ui@2.8.10_@internationalized[email protected][email protected]/node_modules/bits-ui/dist/internal/grace-area.svelte.js:13:24:

      13 │        this.#enabled = $derived(this.#opts.enabled());

         ╵                         ^

  The plugin "vite-plugin-svelte-module:optimize-svelte" was triggered by this import

    node_modules/.pnpm/bits-ui@2.8.10_@internationalized[email protected][email protected]/node_modules/bits-ui/dist/bits/tooltip/tooltip.svelte.js:9:26:

      9 │ import { GraceArea } from "../../internal/grace-area.svelte.js";

        ╵                           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

C:\Sites\ViteBrowserExt\extension\StoryDrafter\node_modules.pnpm\[email protected]\node_modules\esbuild\lib\main.js:1472

  let error = new Error(text);

              ^

Error: Build failed with 2 errors:

node_modules/.pnpm/bits-ui@2.8.10_@internationalized[email protected][email protected]/node_modules/bits-ui/dist/internal/grace-area.svelte.js:13:24: ERROR: [plugin: vite-plugin-svelte-module:optimize-svelte] node_modules/.pnpm/bits-ui@2.8.10_@internationalized[email protected][email protected]/node_modules/bits-ui/dist/internal/grace-area.svelte.js:13:24 $derived(...) can only be used as a variable declaration initializer or a class field

https://svelte.dev/e/state_invalid_placement

node_modules/.pnpm/[email protected][email protected]/node_modules/svelte-toolbelt/dist/utils/attach-ref.js:3:36: ERROR: [plugin: vite:dep-pre-bundle] Missing "./attachments" specifier in "svelte" package

    at failureErrorWithLog (C:\Sites\ViteBrowserExt\extension\StoryDrafter\node_modules.pnpm\[email protected]\node_modules\esbuild\lib\main.js:1472:15)

    at C:\Sites\ViteBrowserExt\extension\StoryDrafter\node_modules.pnpm\[email protected]\node_modules\esbuild\lib\main.js:945:25

    at C:\Sites\ViteBrowserExt\extension\StoryDrafter\node_modules.pnpm\[email protected]\node_modules\esbuild\lib\main.js:1353:9

    at process.processTicksAndRejections (node:internal/process/task_queues:105:5) {

  errors: [Getter/Setter],

  warnings: [Getter/Setter]

}

SOLUTION:
Apparently the new cli upgrades the bits-ui version to 2.8.6. So I downgraded the version to the previous I was using (1.3.4) and it is working again.

PS: a migration guide from the @next version wight be usefull.