Reformat Code only asked the language server for formatting, so files whose server has no formatting capability (Markdown with marksman, and others depending on the server) could not be formatted.
Languages can now declare an external formatter. Prettier is the first: a managed tool installed on demand, or the project's own node_modules/prettier, an explicit path, or PATH. It runs on the backend copy of the document with the file's path so Prettier resolves the project's config, overrides and ignore files, and its result is applied as one undoable edit. Language servers that format a file keep doing so unless Prettier is preferred in Settings › Languages › Prettier; formatting on save is opt-in. Parsers without range support format the whole file and say so.
Errors carry structured tool data, so a missing Prettier reuses the shared install prompt and Prettier diagnostics or timeouts show as non-sticky notifications.
Fixes#639
Without a tsconfig.json or jsconfig.json, tsserver's inferred project holds only
open files and what they import, so completion never offered exports from other
files. Register the project's sources with tsserver as an external project,
using the options an inferred project assumes, so no file is written to disk.
Registration needs `typescript.tsserverRequest`. Projects with a configuration,
including one in a subfolder, stay as they were, and so do trees over 10,000
sources or 16 MiB of JavaScript, since tsserver disables its language service
past 20 MiB. Created and deleted files update the project, and unopened files
stay out of Problems.
Root cause: the tools dir installed typescript@latest, now TypeScript 7 (native port, no typescript.js/tsserver.js/ts.server), so @vue/language-server 3 crashed on ts.server.protocol and restarted forever; Volar 3 hybrid mode also needs tsserver/request forwarding, which we never answered.
Fix: pin TS-as-library servers to typescript@<7 and keep shared deps on uninstall; pick a usable tsdk (setting / bundled / project, --tsdk); bridge tsserver/request to vtsls with @vue/typescript-plugin (null when vtsls is absent); answer workspace/configuration for section ""; stop restarting after 3 consecutive early crashes (IDEA); crash summary starts at the exception line.
Siblings covered: typescript-language-server and svelte-language-server (same TS 7 break), vtsls config, install hints in language TOMLs.
Verified: scoped cargo tests, real-server tests (vue-language-server 3.3.13 + vtsls), in-app on macOS (server running, no crash loop). Not verified on Windows.
Claude-Session: https://claude.ai/code/session_01VUYsdXA2nkF5v6zsC93dpn
l0ng-ai