Local CI runner with full GitHub Actions parity

dev tool real project •• multiple requests

The 'commit and pray' workflow for testing CI changes is a recurring complaint in HN dev-tool wishlists. nektos/act is the de facto answer but explicitly lacks concurrency, vars context, and parts of the github context. Demand is for an act successor that targets feature parity, not just docker-in-docker, so workflow changes can be debugged in seconds without polluting commit history.

builder note

The hard part isn't docker, it's the GitHub Actions runtime semantics. Steal the act architecture, then close the parity gaps one by one with a conformance test suite vs real Actions. The conformance scoreboard alone is good marketing.

landscape (3 existing solutions)

Anyone solving local CI today either uses act and accepts the gaps, or rewrites pipelines into a CI-agnostic DSL. The gap is the boring one: an act that actually passes the same workflow that GitHub passes, without rewrites.

nektos/act Mature and widely used but a long tail of unsupported features. Concurrency, matrix edge cases, parts of github context, env handling. Workflows that pass in act still fail on real Actions.

Earthly Solves CI portability by being a separate DSL. Doesn't run your existing GitHub Actions workflow files locally, it asks you to rewrite.

Dagger Same shape as Earthly. Programmable CI engine, not a faithful local-Actions runner. Wrong tool for the 'edit YAML, test now, commit when green' workflow.

sources (3)

hn https://news.ycombinator.com/item?id=46345827 "Local CI Environment Parity, high engagement on this wish" 2025-12-27

other https://www.freecodecamp.org/news/how-to-run-github-actions-... "Currently, there is no alternative to act CLI" 2026-03-10

other https://github.com/nektos/act "concurrency, no vars context, incomplete github context" 2026-05-20

github-actionsci-cdlocal-devact-alternativedeveloper-tools