zsh

zle facts

Every new editor invocation starts in keymap main; a vicmd selection does not survive into the next line.
$? after the transient prompt's zle .send-break is 1; native Ctrl+C yields 130. Known gap, documented as a TODO in _omp_zle-line-init - do not "fix" one without solving the other path.
Ubuntu's /etc/zsh/zshrc defines a zle-line-init (terminfo smkx), so omp's widget takes the decorate path even in minimal setups - never assume the widget slot is empty.

ZVM initializes lazily at first precmd, so it ALWAYS wraps omp's zle-line-init regardless of source order: its wrapper runs our widget first, zvm_zle-line-init second. Because the transient prompt's zle .recursive-edit consumes the whole editing session, ZVM's line-init effectively ran at line END - any line accepted or interrupted from normal mode desynced ZVM_MODE from the active keymap, and zvm_select_vi_mode's same-mode early return made the break permanent.
Fix in _omp_zle-line-init: call zvm_zle-line-init up front (guarded on $+functions[zvm_zle-line-init] and ZVM_INIT_DONE == true). Keep this if the function is ever restructured.
Landmine: zvm_reset_prompt resolves $rawfunc via dynamic scoping. Any ZVM code running zle reset-prompt while inside our line-init picks up the line-init wrapper's rawfunc (_omp_decorated_zle-line-init) and re-enters the widget recursively. The local rawfunc= at the top of _omp_zle-line-init shadows it - load-bearing, keep it.

An interactive zsh with MONITOR prints "[n] pid" at coproc spawn; disown is too late and a { coproc ... } 2>/dev/null block does NOT suppress it. setopt localoptions no_monitor does - side effect: the child inherits SIGINT/SIGQUIT ignored (POSIX no-job-control), which Go preserves.
Duplicate coproc fds to session fds (exec {out}<&p {in}>&p) - duplicates survive a later coproc replacing the slot. disown %+ keeps the daemon out of jobs and the job-count segment.
Writing to a dead coproc pipe raises SIGPIPE, which kills a non-interactive zsh outright (2>/dev/null cannot stop a signal). Guard daemon writes with a kill -0 $pid pre-check plus setopt localoptions localtraps; trap '' PIPE (function-local, user pipelines unaffected).
Never pass a possibly-zero pid to kill -0 - kill -0 0 signals the caller's own process group and always succeeds.

A redirection-only exec applies EVERY listed redirection to the shell permanently: exec {fd}<&p {fd}>&p 2>/dev/null silences the session's stderr for good (caused issue #7653). Scope the stderr suppression with a brace block: { exec ... } 2>/dev/null.
zsh 5.9: read -r -u $fd -d $'\0' -t N ignores -t entirely and blocks forever on a silent fd. Without -d, the timeout works.
Teardown belongs in zshexit_functions; the daemon lifecycle is fd-governed (closing the fds - or the shell dying, even by SIGKILL - EOFs the daemon's stdin).
To debug widget re-entry, log ${funcstack[*]} inside the widget - zle calls from shell functions appear on the stack and expose who invoked what.