Inline assistance or delegated work?
“Coding assistant” can mean autocomplete, IDE chat, an agent editing multiple files, or a cloud service that receives a task and returns a pull request. These are different levels of delegation. An inline suggestion stays close to the code; a cloud task works independently for a while and needs a more formal review.
To compare tools, ask where the repository lives, which commands the tool can run, how permissions and data are handled, and how changes can be inspected. The ability to use a shell does not mean unrestricted access is appropriate.
Four tools, different entry points
Codex spans app, CLI, IDE and cloud experiences depending on the current product and plan. OpenAI documents agents working in local or managed environments, editing files and running code with controls. It is worth evaluating for bounded tasks, tests, refactoring or delegated work.
Claude Code is a terminal agent. Anthropic documents interactive and non-interactive use, file reading and editing, and commands governed by configurable permissions. Gemini CLI is open-source software, but the CLI and Gemini model are separate. Google announced that the previous individual/free access stopped serving requests on June 18, 2026; enterprise access and paid API routes remain. Google directs consumers to Antigravity CLI.
GitHub Copilot coding agent is distinct from Copilot autocomplete: it can take a GitHub task, work in a temporary cloud environment connected to a repository and propose a pull request. Review the code and test results before merging; access and plans remain subject to GitHub’s current terms.
Where a coding agent fits in a development workflow
The same repository can be approached locally or through a cloud task. Human review remains the release gate in either case.
Developer defines task
Scope, acceptance criteria and sensitive files are identified.
IDE or terminal agent
A local agent can inspect the working tree and run permitted commands.
Repository and tools
Access is limited to the required files, integrations and environment.
Tests and diff
Run checks, inspect changes and resolve failures before proposing completion.
Branch or pull request
A cloud workflow may return a branch or PR for human review and merge.
Where each agent fits
| Tool | Main interface | Execution | Workflow to evaluate |
|---|---|---|---|
| OpenAI Codex | App, CLI, IDE and cloud depending on mode | Local or managed environment | Multi-file work, tests and delegated tasks with review |
| Claude Code | CLI and documented integrations | Local terminal with configurable permissions | Explore and modify a repository under developer control |
| Gemini CLI | Open-source CLI | Terminal; model access depends on account or API | Terminal workflow; verify current access conditions |
| GitHub Copilot coding agent | GitHub issues and pull requests | Temporary cloud environment | Delegate a tracked task and review the resulting PR |
Features and plans change. This summarizes documented workflow categories, not guaranteed prices, quotas or performance.
Choose by type of work
For a quick local change, a CLI or IDE agent can keep the prompt-code-test loop in the developer’s environment. Claude Code, Codex and Gemini CLI fit this category, with different authentication and control models. For debugging and explanation, staying close to the repository makes it easier to verify references and request small changes.
For a task written as an issue, GitHub Copilot coding agent aligns with a branch and pull-request workflow; Codex cloud offers another managed delegation model. Define acceptance criteria, run automated tests and keep human review before merging or releasing.
Security, context and cost belong in the comparison
A terminal agent may read repositories and execute commands: restrict directories, permissions and network access, keep secrets out of its context and approve destructive actions. For cloud agents, review which files and metadata are transferred, how long the environment exists and which integrations are enabled. A plausible diff can add dependencies or change behavior the tests do not cover.
Do not infer a free plan from an open-source CLI. Gemini CLI remains open-source software, but its former individual model access ended under Google’s June 2026 timeline. Codex and Claude Code depend on plans or APIs; Copilot has distinct products and plans. Check current official documentation rather than planning around unverified quotas.
A useful comparison test
Choose a reversible task, such as adding a clearly specified validation to a test project. Give each tool the same requirements and acceptance criteria; ask it to plan, make the change and run tests. Assess correctness, out-of-scope edits, review time and permission clarity.
The useful measure is the cost of the whole cycle: preparing context, correcting the agent, debugging, reviewing and maintaining the result. Teams should choose a workflow that fits their repositories and controls while keeping responsibility for the merge clear.
Sources & further reading
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