RFC 0025: Modern Process Spawn API

straight-shoota · March 10, 2026, 10:19am

This RFC is already pretty advanced, but may need some polishing: RFC 0025: Modern Process Spawn API by straight-shoota · Pull Request #25 · crystal-lang/rfcs · GitHub

Here is the full proposal text. We’re still debating some of the hardest decisions in software engineering: naming things. Any input is appreciated.

github.com/crystal-lang/rfcs

process-spawn-api/text/0025-process-spawn-api.md?rgh-link-date=2026-03-03T10%3A39%3A12Z

rfc

---
Feature Name: process-spawn-api
Start Date: 2022-02-28
RFC PR: "https://github.com/crystal-lang/rfcs/pull/25" # fill me in after creating the PR, also update the filename
Issue: "https://github.com/crystal-lang/crystal/issues/16657"
---

## Summary

Provide an ergonomic, safe, and portable API for spawning subprocesses.

## Motivation

This proposal consolidates several ongoing discussions (see [#16657]) into a coherent set of changes. We maintain backward compatibility by introducing incompatible behavior only in new method variants.

These changes aim to improve convenience and portability, and reduce accidental misuse.
Spawning processes is a fundamental capability for many programs, and many users end up writing small helpers to capture output, run one-off commands, or probe for executables. The current API is flexible but doesn't cater to some common needs, and it exposes escape hatches (`shell: true`, `$?`) that make code fragile and non-portable.

## Guide-level explanation

This file has been truncated. show original

Topic		Replies	Views
Improve Process API Crystal Contrib	7	1220	March 10, 2026
Deprecate top-level fork Community	10	859	January 10, 2023
What is the equivalent of Ruby Process.detach? Help & Support	5	387	November 5, 2022
Proposal: add spawn! to exit(1) on any unhandled exception in spawned Fiber Crystal Contrib	11	435	December 29, 2024
Stdlib - A mixed discussion about some modules Crystal Contrib	3	639	July 26, 2019

RFC 0025: Modern Process Spawn API

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