Codex CLI vs OpenCode vs Cline vs Ralph Workflow 2026: Which AI Coding Agent Actually Runs Unattended?

The question isn't which agent is smartest

If you've spent any time in AI coding discussions in 2026, you've heard about Codex CLI, OpenCode, and Cline. They're all powerful. They all generate good code when you're sitting there guiding them.

The harder question is: which one can actually run while you're asleep and produce something you'd merge in the morning?

That's the question this comparison answers. No feature grids. No star ratings based on vibes.

Codex CLI (OpenAI)

What it is: OpenAI's official terminal-based coding agent, announced in early 2026. It runs in your terminal and integrates directly with the OpenAI API.

What it does well: - Native integration with OpenAI's strongest models - Clean terminal interface with file editing capabilities - Good at single-pass refactoring and code generation - Fast when used interactively

Where it falls short for unattended work: - No built-in multi-phase workflow (plan → code → verify) - No checkpoint/resume mechanism — if it crashes, you start over - Limited to OpenAI models (no cost arbitrage across providers) - Interactive-first design — expects you to review and approve each step

Codex CLI is a powerful interactive tool. But it's not built for walking away and coming back to a complete project.

OpenCode

What it is: An open-source terminal coding agent with a focus on deterministic behavior and reproducibility.

What it does well: - Deterministic execution model — same input produces consistent output - Open source with an active community - Good at scriptable, repeatable tasks - Clean architecture that's easy to extend

Where it falls short for unattended work: - No structured verification phase — you have to manually check if the output is correct - No planning phase — it jumps straight to implementation - No cost arbitrage — uses one model per session - Not designed for multi-hour unattended runs

OpenCode is excellent for reproducible coding tasks. It's the tool you want when you need the same thing done the same way every time.

Cline

What it is: A VS Code extension that brings AI coding into the editor with a focus on diff-based editing and inline context.

What it does well: - Deep IDE integration — sees your full project context - Diff-based editing — you see exactly what changes - Good at understanding complex codebases - Native VS Code integration

Where it falls short for unattended work: - IDE-bound — requires VS Code to be running - No pipeline orchestration — one agent, one session - No checkpoint/resume across sessions - Interactive by design — you're expected to be at the keyboard

Cline is a great editor companion. It's not an orchestrator.

The gap all three share

Codex CLI, OpenCode, and Cline are all interactive tools. They're built for the model where you sit at the keyboard, guide the agent, and approve changes as they happen.

That model works well for exploration and small tasks. It falls apart when: - The task is too big to babysit (takes 2+ hours) - You want to review the output as a whole, not piece by piece - You want to sleep while the work happens

Ralph Workflow

What it is: A free and open-source composable loop framework that orchestrates the coding agents you already have (Claude Code, Codex CLI, OpenCode, etc.) in a structured pipeline.

How it fills the gap:

Planning phase — A strong model turns your spec into a concrete implementation plan. You don't have to be there for this.

Development phase — Coding agents work through the plan. You can route different phases to different models to control costs (Cheap model for boilerplate? Strong model for critical logic? Your call.)

Verification phase — Automated checks validate the output. Tests run. Linters run. You come back to a verdict, not just a summary.

Checkpoint resume — If it crashes at 3 AM, it picks up from where it left off. You don't wake up to nothing.

Key design choices that matter for unattended work:

Runs on your machine with your own API keys — no vendor lock-in

Model-agnostic — Claude, GPT, Gemini, DeepSeek — use whatever you want per phase

TOML configuration — define agent policies declaratively

Repo-native — works with your git workflow, not against it

When to use what

If you want to... | Use
Quickly generate code while at the keyboard | Codex CLI, OpenCode, or Cline
Run a reproducible, deterministic script | OpenCode
Get AI suggestions inside VS Code | Cline
Ship a well-specified, substantial task overnight | Ralph Workflow

The bottom line

Codex CLI, OpenCode, and Cline each solve an important part of the AI coding problem — but they all assume you'll be there watching.

Ralph Workflow is built for the opposite assumption: you wrote a clear spec, you trust the pipeline, and you want to come back to something reviewable.

Different tools for different moments. Know which moment you're in.

Ready to try unattended coding?

👉 Codeberg (primary): codeberg.org/RalphWorkflow/Ralph-Workflow 👉 GitHub (mirror): github.com/Ralph-Workflow/Ralph-Workflow 👉 Docs: ralphworkflow.com/docs

pipx install ralph-workflow
ralph --init
$EDITOR PROMPT.md # write your spec
ralph # run — then walk away

Which AI coding tool do you use for overnight tasks? We're curious what actually works in practice.