Enable LSP semantic diagnostics on file writes

What changed

Hermes Agent added LSP semantic diagnostics that run on every write_file or patch call. A real language server now checks the edited file for type errors, undefined symbols, and missing imports before the agent continues.

The feature landed on 21 May 2026 and works with any LSP-compatible language server the user has installed on the VPS. No extra API keys or cloud services are required.

Why it matters

Vibe Builders who delegate code changes to Hermes now receive immediate feedback inside the same chat thread instead of discovering broken imports hours later. This reduces the loop of "agent writes code, human tests, agent fixes" that currently wastes tokens and time.

The move pressures pure LLM coding agents that skip static analysis. It also bets that self-hosted agents can match IDE-grade tooling when the host machine already runs the necessary language servers.

How to use it

Update Hermes Agent to the current release, then install the language server for your target language on the same VPS. Add the server binary path to the hermes config under lsp_servers.

Run a write_file or patch command as usual. Errors appear as normal agent messages with file, line, and suggested fix. The check adds roughly 200-800 ms per operation depending on project size.

Watch for

Confirm the bet if generated code passes type checks on first run in three consecutive projects. Watch for slowdowns on large monorepos or false positives that force manual overrides. The next expected step is automatic import insertion once diagnostics are stable.