Capture LSP debug logs

Prefer a log file because an editor may hide its child process’s standard error:

mergeway-lsp --log-file /tmp/mergeway-lsp.log --log-level debug

Configure those two arguments in the client launcher, reproduce the problem, and inspect the file. Existing content is retained because the server opens the file in append mode. The log can contain absolute paths and error details; review it before sharing and remove it when finished.

For a client that exposes child stderr, use:

mergeway-lsp --log-stderr --log-level debug

Never redirect stderr into stdout. Standard output must contain only framed JSON-RPC traffic.

Environment variables are useful when a client cannot supply arguments:

MERGEWAY_LSP_LOG_FILE=/tmp/mergeway-lsp.log \
MERGEWAY_LSP_LOG_LEVEL=debug \
mergeway-lsp

Flags override the matching non-empty file and level variables. --log-stderr and a truthy MERGEWAY_LSP_LOG_STDERR are additive, but a selected log file takes priority over stderr. Valid truthy values are 1, true, yes, and on, case-insensitively. Logging defaults to info; without a file or stderr selection, logs are discarded.

If the process rejects an invalid level or cannot open the file, it writes mergeway-lsp: ... to stderr and exits 1. Unknown flags exit 2.