openai/codex

What it does

You install it, run codex in a project folder, and describe a change. It reads the files in the folder, proposes edits, applies them, and runs the commands needed to check its work, such as the test suite or a package install. It has three levels of access to your machine, named in its own documentation: read-only, workspace-write and danger-full-access. Separately from that, it has two settings for when it must stop and ask you: ask on request, or never ask. The two controls are independent, which the documentation states explicitly: one sets the technical boundary and the other decides when you are consulted. It sandboxes the commands it spawns, using the operating system's own facilities on each platform. What it does not do is work without a paid service behind it, and on Linux it does not sandbox at all without the right system support: it needs bwrap or a bundled helper that requires unprivileged user namespaces, and it prints a warning at startup when that is missing.

Why it matters

Who it suits. Anyone who already works mostly in a terminal and would rather describe a change than make it by hand, and anyone on a paid plan from this provider that already includes the tool. The sandbox levels mean it can be used cautiously: read-only is a real mode, and it is a reasonable way to start. Skip it if you are not willing to pay a model provider, and skip it if your work is on a machine where you cannot install the sandbox support it needs.

Verdict. At 128,633 stars this is the largest repository in today's twelve by a wide margin, and code landed on it on the morning of this edition. Worth half an hour if you already pay for the plan, because the setup is a single command. Two things to get right before you let it loose. First, the combination of full access and never asking removes the file and network boundaries completely, and the documentation says so in those words; that combination should be a deliberate decision and not a default you inherited. Second, on some Ubuntu systems the sandbox is blocked by a security policy, and the documentation's fallback suggestion is to turn that policy off, which is a worse trade than it sounds. Alternatives worth comparing: sst/opencode at 212,625 stars is larger still and provider-neutral, and cline/cline lives inside an editor rather than a terminal.