Language servers — errors after every write

A builder agent (builder.md) gets the compiler's verdict on a file the moment it writes it. After file_write or file_patch the tool result carries the errors a language server found — the same programs VS Code runs behind its red squiggles — so the model fixes the mistake in the same step instead of finding it when the tests run.

{
  "path": "/home/me/code/app/src/history.ts",
  "replacements": 1,
  "errors": [
    "ERROR [42:11] Property 'finishedAt' does not exist on type 'SwitchEntry'."
  ],
  "errors_in_other_files": {
    "src/api.ts": ["ERROR [17:5] Expected 2 arguments, but got 1."]
  },
  "language_server": "typescript",
  "hint": "Fix these before moving on — they are the compiler's word, not a guess."
}

Errors only (severity error), at most 10 per file with a trailer for the rest, and up to 5 other files whose verdict changed because of this write — a renamed function breaks its callers, and the builder hears it at once. Warnings are left out on purpose: a small model chases them instead of the task. A clean file says "hint": "No errors in this file." so the builder can trust it.

Chat agents never see any of this: the hook asks the server only for a builder session, and a builder without a language server for the file's language gets a plain result, as before.

Which servers

id	files	server	install
typescript	.ts .tsx .js .jsx .mjs .cjs .mts .cts	typescript-language-server (with typescript@5)	somora lsp install typescript
pyright	.py .pyi	pyright-langserver	somora lsp install pyright

somora lsp install (no id) installs both; somora lsp status shows what is found and where. The servers are installed with npm into ~/.somora/lsp/ — nothing touches the system's global packages — and found in this order: the command in config, ~/.somora/lsp, then PATH. Nothing is downloaded during a turn: a missing server means no errors on the result, and the builder's environment block says so (pyright — not installed (somora lsp install pyright)).

How it runs

• One server process per project root and language, started when a builder first reads or writes a matching file (a read pre-warms it, so the first write does not wait for the cold start), stopped after ten idle minutes or when somora shuts down.
• The root is the nearest folder at or above the file with a marker (tsconfig.json, package.json, pyproject.toml, setup.py, …, .git), never above the pinned project folder. Pyright is pointed at the project's .venv/bin/python when there is one.
• After a write the server gets the new text and somora waits for its verdict on that file: lsp.waitMs (default 3 s), longer for a project's first verdict (the server loads the project). No verdict in time → no errors on the result, one log line, the turn goes on.
• A server that fails to start is left alone for ten minutes, then tried again.
• The servers live in the main somora process; the file tools ask over loopback HTTP (POST /lsp/diagnostics), so the MCP child that serves claude-cli and codex-cli gets the same verdicts.

Config

lsp:
  enabled: true          # off = no server is started, results as before
  waitMs: 3000           # wait for a verdict after a write (ms)
  servers:
    typescript:
      enabled: true
      # command: /usr/local/bin/typescript-language-server   # instead of ~/.somora/lsp or PATH
    pyright:
      enabled: true

Routes

• POST /lsp/diagnostics {agent, session, path, touch?} → {diagnostics: {server, errors, errors_in_other_files} | null}; with touch: true only starts the server for that file ({touched: true}). null for a chat agent, a disabled feature, a file without a server, or no verdict in time.
• GET /lsp/status → {enabled, waitMs, servers: [{id, title, extensions, enabled, command, source}], running: [{id, root, alive, docs, idleMs}]}.