lspc

lspc is a JSON-only command-line client for querying installed Language Server Protocol servers and safely previewing their proposed filesystem changes. It keeps language servers warm between invocations and works on Linux, macOS, and Windows.

Install

Install from a checkout with Rust 1.89 or newer:

cargo install --path . --locked
lspc version

lspc launches language servers but does not install them. Install the server you want to use separately.

Configure a server

Find the native user configuration path:

lspc schema config user | jq -r .result.resolvedPath

Create that file with a server declaration and route. For example, if rust-analyzer is on PATH:

version = 1
default_server = "rust"

routes = [
  { server = "rust", language_id = "rust", extensions = [".rs"] },
]

[servers.rust]
executable = "rust-analyzer"

User configuration is trusted. A repository may instead commit .lspc.toml; project-controlled launch fields require an explicit lspc trust grant before the server can start.

Query code

All output is one compact JSON object on stdout. Source lines and columns are zero-based Unicode-scalar positions.

lspc capabilities --workspace . --server rust
lspc definition --workspace . --server rust \
  --file src/lib.rs --line 12 --column 8
lspc references --workspace . --server rust \
  --file src/lib.rs --line 12 --column 8 --include-declaration true

A server may answer an early navigation Query before background indexing finishes. If an expected result is empty, inspect the optional context.serverProgress. Non-empty progress may be related, so watch it and retry after it clears:

lspc session status --workspace . --server rust | jq .result.progress

Preview and apply a rename

Mutation Queries do not edit files. They persist an immutable Preview for inspection:

preview_id=$(
  lspc rename --workspace . --server rust \
    --file src/lib.rs --line 12 --column 8 --new-name replacement |
  jq -r .result.previewId
)
lspc preview show "$preview_id" | jq .result.diff
lspc apply "$preview_id"

Application rechecks the inspected Preview and records a durable Receipt. There is no force-apply path for stale edits.

Discover commands

lspc help | jq
lspc help definition | jq
lspc schema definition | jq
lspc schema --full

help returns a compact command catalog without JSON Schemas. Focused schema returns the exact contract for one command; schema --full is the complete registry for tooling.

Use the structured error.code, error.retry, and error.delivery fields rather than parsing messages. See skills/lspc/ for configuration, Query, Mutation, Trust, and Recovery workflows.

License

Licensed under either MIT or Apache-2.0, at your option.