Compatibility

co-proc does not replace the zsh coproc reserved word.

This is intentional. In zsh, coproc is parsed as a reserved word rather than resolved as a builtin or ordinary command. A shell function named coproc cannot wrap it while preserving native grammar such as:

coproc { cat }
coproc while read -r line; do print -r -- "$line"; done

Preserved native syntax

These remain zsh-native and are not rewritten unless the optional interactive widget sees a simple extended form:

coproc bc
coproc { ... }
coproc while ...
coproc for ...
coproc if ...

Extended syntax

Scriptable extended syntax uses co-proc:

co-proc start calc bc -l
co-proc list
co-proc send calc '1 + 1'
co-proc read calc
co-proc stop calc

With the optional ZLE integration enabled, interactive commands like these are rewritten before acceptance:

coproc calc bc -l
coproc list
coproc send calc '1 + 1'

The widget does not rewrite lines with redirections, pipes, separators, groups, or native control words. Use explicit co-proc start NAME zsh -c '...' for complex startup forms.

Mixing native and named coprocesses

Starting any coprocess retargets zsh's special p handle. co-proc preserves named processes by saving ordinary descriptors before later coprocesses retarget p. If you use native coproc directly and need to keep it after starting another coprocess, save its descriptors first.