# Tools Landscape

The agent-coding tool market stabilized around four shapes: terminal agents, IDE-integrated agents, VS Code extension agents, and lightweight pair-programmers. They look similar from the outside but the tradeoffs are real.

This page compares the serious options as of April 2026. No rankings, no "best tool" — just what each one is and the kind of work it fits.

## The four tools worth knowing

| Tool | Shape | Primary loop | License |

| --- | --- | --- | --- |

| Claude Code | Terminal CLI + IDE extensions | Autonomous loop with strong permission model | Proprietary (Anthropic) |

| Codex CLI | Terminal, written in Rust | Autonomous agent with OS-level sandboxing | Open source (OpenAI) |

| Cursor Agent | Forked VS Code (full IDE) | Agent mode with checkpoints | Proprietary |

| Cline | VS Code / JetBrains extension | Plan/Act with approve-every-change | Open source (Apache 2.0) |

Aider is worth mentioning for a specific niche: terminal-based, git-native, deliberately small.

## Claude Code

Anthropic's agent, installed via `npm i -g @anthropic-ai/claude-code` and exposed through terminal, VS Code, and JetBrains.

- **Permission-first architecture.** Every action is gated by a rule system supporting wildcards (`Bash(npm run *)`), path-scoped rules (`Edit(src/**)`), and modes: `default`, `acceptEdits`, `plan`, `auto`, `bypassPermissions`, `dontAsk`. See [Hooks and Policy-as-Code](/s/agents-development/wiki/hooks-policy-as-code).

- **First-party MCP.** Scopes: `local`, `project` (`.mcp.json`), `user`. See [MCP](/s/agents-development/wiki/mcp).

- **Subagents and headless mode.** Built-in subagents (Explore, Plan, general-purpose) plus custom ones in `.claude/agents/`. For CI, `claude -p "task" --output-format json` runs non-interactively. See [Multi-Agent Patterns](/s/agents-development/wiki/multi-agent-patterns).

- **CLAUDE.md.** Plain-text markdown rules with a clear precedence. See [CLAUDE.md and Agent Rules](/s/agents-development/wiki/claude-md-agent-rules).

- **Enterprise settings.** Managed policy files override user settings and cannot be bypassed. See [Enterprise Rollout](/s/agents-development/wiki/enterprise-rollout).

**Best for**: terminal-first teams who want auditable guardrails and can invest in CLAUDE.md and hooks.

**Weakest at**: inline-diff IDE refactoring flows.

Sources: [docs](https://code.claude.com/docs/en/overview), [permissions](https://code.claude.com/docs/en/permissions), [headless](https://code.claude.com/docs/en/headless).

OpenAI's open-source agent, written in Rust, installed with `npm i -g @openai/codex`.

- **Rust + OS sandbox.** Apple Seatbelt on macOS, Landlock + seccomp on Linux. The sandbox is the enforcement layer.

- **Approval modes.** Configurable policies for when edits need sign-off.

- **Models.** GPT-5.4, GPT-5.3-Codex, others with reasoning levels.

- **Subagents and MCP.** Task parallelization and external tool integration.

- **Image inputs.** Screenshots and design specs as context.

**Best for**: teams in the OpenAI ecosystem, people who trust OS sandboxing over prompt-based permissions.

**Weakest at**: Windows is experimental (WSL recommended).

Sources: [Codex CLI docs](https://developers.openai.com/codex/cli/), [GitHub](https://github.com/openai/codex).

## Cursor

A fork of VS Code with the agent built into the IDE.

- **Full IDE, not an extension.** Inline diffs, checkpoints, agent state tightly integrated with the editor.

- **Checkpoints.** Codebase snapshots per session — safety net for long autonomous runs.

- **Queued messages.** Stack instructions while the agent works.

- **Tool-agnostic models.** Anthropic, OpenAI, and others, each with tuned tool prompts.

- **MCP support** plus a rules system (`.cursorrules`) analogous to CLAUDE.md.

**Best for**: developers who want the agent deeply integrated with an editor they already live in.

**Weakest at**: headless CI and reproducibility — a lot of the power lives in the UI.

Sources: [Cursor Agent docs](https://cursor.com/docs/agent).

## Cline

Open-source VS Code, Cursor, and JetBrains extension (Apache 2.0) built around explicit user approval for every action.

- **Approve-every-change.** Every edit and command surfaces a confirmation. Slow but trivially auditable.

- **Plan/Act modes.** Plan explores, Act executes. The separation is explicit.

- **Bring-your-own-model.** Anthropic, OpenAI, Google, OpenRouter, DeepSeek, Ollama.

- **Client-side only.** Context flows directly to the model provider.

- **MCP support.**

**Best for**: regulated environments, learners who want to see every step, teams on strict data paths.

**Weakest at**: speed.

Sources: [Cline docs](https://docs.cline.bot/getting-started/what-is-cline).

## Aider (honorable mention)

A terminal-based pair programmer. Maps your whole codebase, makes one change, auto-commits it. You review with normal git tools.

- Auto-commits per change.

- Codebase map for larger repos.

- Claude, GPT-5.4, DeepSeek, local models.

- Voice-to-code, image context, linting + tests.

**Best for**: solo developers who want a small, inspectable tool with git as the audit log.

Source: [aider.chat](https://aider.chat/).

## Picking one

Do not pick by "which is best". Pick by workflow:

- **Terminal-first, CI, enterprise guardrails**: Claude Code

- **Open source, sandbox over prompt rules**: Codex CLI

- **IDE-native, inline diffs**: Cursor

- **Regulated, approval per change**: Cline

- **Git-native, small surface**: Aider

A common combination: Cursor for editor work plus Claude Code for terminal and CI. They read the same CLAUDE.md and share MCP servers.

## Benchmarks — skip them

No honest public benchmark will tell you which tool fits *your* codebase. Run a real task from your own backlog in each tool for an hour. That is the benchmark.

---

Next: [CLAUDE.md and Agent Rules](/s/agents-development/wiki/claude-md-agent-rules)

## Sources

- [Claude Code docs](https://code.claude.com/docs/en/overview)

- [OpenAI Codex CLI](https://developers.openai.com/codex/cli/)

- [Cursor Agent](https://cursor.com/docs/agent)

- [Cline](https://docs.cline.bot/getting-started/what-is-cline)

- [Aider](https://aider.chat/)

- [MCP](https://modelcontextprotocol.io/)