---
id: SLICE-0009
type: slice
status: ready
parent: NS-0002
title: Harden LSP protocol behavior
refs:
  - hemx-lsp/src/main.rs
  - docs/editor-support.md
  - REQUIREMENTS.md
---

## Objective

Make `hemx-lsp` predictable as an LSP server: initialize capabilities, document sync, completion, hover, diagnostics, shutdown, and unknown request errors should have focused protocol tests.

## Authority

`hemx-lsp/src/main.rs` implements the protocol loop; `docs/editor-support.md` names the editor-facing command surface.

## Close when

- Tests cover `initialize`, `didOpen`, `didChange`, `didSave`, `didClose`, `completion`, `hover`, `shutdown`, and unknown requests.
- The tests assert JSON-RPC framing and response IDs, not just helper functions.
- The server keeps normal HTML/tree-sitter tooling assumptions and does not add editor-provider policy.

## Verification

- `cargo test -p hemx-lsp`
- `cargo run -p hemx-lsp -- help`

## Non-goals

- Do not add async runtime or background watchers unless protocol tests prove sync IO is insufficient.
- Do not publish editor extensions in this slice.

## Evidence

The current LSP loop is small and testable through in-memory readers/writers.