Best AI Coding Assistants

As of July 2026, the two strongest AI coding assistants overall are Claude Code and the OpenAI Codex CLI, which finish within 0.3 points of each other at the top of the Terminal-Bench 2.1 agent leaderboard: Codex CLI on GPT-5.5 scores 83.4 percent and Claude Code on Claude Fable 5 scores 83.1 percent ^[1]. Claude Code runs the highest scoring coding models on the market, Claude Fable 5 at 95.0 percent and Claude Opus 4.8 at 88.6 percent on SWE-bench Verified ^[2], which makes it the pick for hard, autonomous, multi-file work. Codex CLI is the fastest open-source terminal agent and the value pick for anyone already paying for ChatGPT. For in-editor (IDE) coding, Cursor is the best all-around AI editor and GitHub Copilot is the most flexible choice for teams and enterprise. For fully autonomous, hands-off cloud engineering, Devin leads.

Quick verdict: which AI coding assistant is best?

• Best overall and best for hard autonomous coding: Claude Code (Claude Fable 5 or Claude Opus 4.8).
• Best raw terminal-agent score and best open-source CLI: OpenAI Codex CLI on GPT-5.5, 83.4 percent Terminal-Bench 2.1 ^[1].
• Best AI IDE (in-editor flow): Cursor.
• Best for the widest team and enterprise rollout: GitHub Copilot.
• Best free and best value: Gemini CLI (free tier), or Codex CLI if you already pay for ChatGPT.
• Best fully autonomous cloud engineer: Devin.
• Best open-source and model-agnostic: Aider (terminal) and Cline (in your IDE).

Summary comparison table

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Last verified: July 2026. Prices in USD. SWE-bench Verified is a model score; Terminal-Bench 2.1 is a tool-plus-model score from the official leaderboard ^[1][2]. A blank or n/r cell means the vendor or a primary source does not report that figure. Bring-your-own-model tools inherit the score of whichever model you attach.

Best terminal coding agents (CLI)

Command-line agents run in your terminal, read and edit the whole repository, run tests, and iterate on failures. They currently hold the top of the Terminal-Bench 2.1 leaderboard ^[1].

1. Claude Code (Anthropic)

Best for: complex, autonomous, multi-file engineering where correctness matters most.

Claude Code is Anthropic's agentic coding tool for the terminal, with companion extensions for VS Code and JetBrains and a web version ^[4]. It defaults to Claude Sonnet 5 on the $20 per month Pro plan and to Claude Opus 4.8 on Max, Team Premium, and API access, and it can switch on demand to Claude Fable 5, Anthropic's most capable model ^[4]. Those models top both coding benchmarks: Fable 5 scores 95.0 percent and Opus 4.8 88.6 percent on SWE-bench Verified ^[2], and Claude Code reaches 83.1 percent (Fable 5) and 78.9 percent (Opus 4.8) on Terminal-Bench 2.1 ^[1]. Anthropic's own Opus 4.8 report cites a higher 87.6 percent on Terminal-Bench 2.1 using its internal harness ^[6]. Plans: Pro $20 per month, Max $100 per month (5x) and $200 per month (20x), plus API pay-as-you-go; API token prices are $10 input and $50 output per million for Fable 5, and $5 and $25 for Opus 4.8 ^[5]. Claude Code is closed source. Note that from July 7, 2026 Fable 5 moved to usage credits on consumer subscription plans, while API per-token pricing held steady ^[7].

2. OpenAI Codex CLI (OpenAI)

Best for: fast agentic coding, and the best pick if you already pay for ChatGPT.

The OpenAI Codex CLI is OpenAI's open-source terminal agent, released under the Apache-2.0 license, with IDE extensions and a cloud version (Codex Web) ^[13][9]. It runs GPT-5.5 by default and posts the single highest tool-plus-model score on the board, 83.4 percent on Terminal-Bench 2.1 ^[1][9]. OpenAI's own GPT-5.5 launch reported 82.7 percent on the older Terminal-Bench 2.0 and 58.6 percent on SWE-bench Pro; the company does not publish a SWE-bench Verified figure for 5.5, and third-party leaderboards put it near 82.6 percent ^[11][3]. Access is bundled with ChatGPT plans (Free, Go $8, Plus $20, Pro from $100 up to $200 per month, Business $20 per user) or via API key at $5 input and $30 output per million tokens for GPT-5.5 ^[10][12]. There is no separate "GPT-5.5-Codex" model; Codex runs the general GPT-5.5 ^[9].

3. Gemini CLI (Google)

Best for: free and low-cost terminal coding with a very large context window.

Gemini CLI is Google DeepMind's open-source (Apache-2.0) terminal agent ^[22]. It runs Gemini 3 Pro today with Gemini 3.1 Pro rolling out; Gemini 3.1 Pro scores 80.6 percent on SWE-bench Verified per Google's model card, and Gemini CLI reaches 70.7 percent on Terminal-Bench 2.1 ^[8][1]. Its draw is price: a free tier through a personal Google account (historically 60 requests per minute and 1,000 per day), plus paid access via the Gemini API (Gemini 3.1 Pro at $2 input and $12 output per million tokens up to 200K context) ^[22][23]. Google has begun consolidating individual Gemini Code Assist users into its Antigravity agentic IDE, so confirm the current free-tier terms before you build on them ^[30].

4. Aider (open source)

Best for: a lightweight, scriptable, model-agnostic pair programmer in the terminal.

Aider is a free, open-source (Apache-2.0) terminal tool that edits your git repository and works with almost any model through your own API key, so you pay only model costs ^[25]. On its own Aider polyglot benchmark, GPT-5 at high reasoning leads at 88.0 percent, though that leaderboard was last updated in November 2025 and predates the 2026 models above ^[24]. Aider is the go-to for developers who want full control and git-native, diff-based edits.

Best AI code editors (IDE flow)

If you want AI inside a familiar editor with inline completions, chat, and an in-editor agent, these lead.

5. Cursor (Anysphere)

Best for: the best all-around in-editor experience.

Cursor is a closed-source, AI-first IDE (a VS Code fork) from Anysphere ^[14]. It ships its own fast agent model, Composer 2.5 (released May 2026, built on a Moonshot Kimi K2.5 checkpoint), and also runs the frontier models: Claude Opus 4.8, Claude Fable 5, GPT-5.5, and Gemini 3.1 Pro ^[15][18]. Cursor does not publish a SWE-bench Verified or Terminal-Bench score for Composer, citing a proprietary "Cursor Bench" and a roughly 4x speed advantage instead, so treat its benchmark cell as n/r; when running Opus 4.8 it inherits that model's 88.6 percent Verified score ^[15][2]. Pricing is usage-based: Hobby free, Pro $20 per month (with $20 of model usage included), Pro+ $60, Ultra $200, and Teams from $40 per user ^[14].

6. GitHub Copilot (GitHub / Microsoft)

Best for: the widest rollout across editors and the safest enterprise choice.

GitHub Copilot is the most widely deployed assistant, available in VS Code, JetBrains, and Visual Studio with chat, an in-editor agent mode, an autonomous cloud "coding agent" that opens pull requests, and a CLI ^[16][18]. It is multi-model: it now offers Claude Opus 4.8, Claude Sonnet 5, Claude Fable 5, GPT-5.5, and Gemini 3.1 Pro, with an "Auto" router and a GPT-5.3-Codex base model ^[18]. As of June 2026 Microsoft-owned GitHub replaced "premium requests" with dollar-denominated AI credits ^[17]. Plans: Free; Pro $10 per month ($15 of credits); Pro+ $39; Business $19 per seat; Enterprise $39 per seat; and a new Max at $100 ^[16][17]. GitHub does not publish its own SWE-bench figure, so benchmark quality tracks the model you pick (up to 88.6 percent Verified via Opus 4.8) ^[2].

7. Windsurf, now Devin Desktop (Cognition)

Best for: a fast in-house model inside a full IDE.

Windsurf is a closed-source AI IDE (a VS Code fork) built around the Cascade agent. Cognition, the maker of Devin, acquired Windsurf in July 2025 and has rebranded it "Devin Desktop", so windsurf.com now redirects to the Devin site ^[19][20]. Its in-house SWE-1.6 model (April 2026) is free inside the editor and runs up to 950 tokens per second on Cerebras hardware; Cognition reports SWE-1.6 improved more than 10 percent over SWE-1.5 on SWE-bench Pro but does not publish an absolute SWE-bench Verified score, so its cell is n/r ^[21]. Frontier models (Opus 4.8, GPT-5.5, Sonnet 5) are also selectable. Pricing: Free, Pro $20 per month, Max $200 per month, Teams $80 per month plus $40 per developer seat ^[20].

8. Cline (open source)

Best for: a transparent, open-source agent inside your existing IDE.

Cline is a free, open-source (Apache-2.0) autonomous agent that runs as a VS Code extension and CLI, bringing your own model key (Anthropic, OpenAI, Google, OpenRouter, or local) ^[26]. Because it is model-agnostic, its benchmark ceiling is whatever model you attach: pair it with Claude Fable 5 and you inherit the 95.0 percent Verified score ^[2]. It is the pick for developers who want an auditable agent without leaving their editor or paying a subscription.

Best for enterprise and autonomous cloud engineering

9. Devin (Cognition)

Best for: fully autonomous, delegate-and-forget engineering at team scale.

Devin is Cognition's autonomous cloud software engineer: you assign it a task or issue and it plans, writes, tests, and opens a pull request in its own cloud environment, running many tasks in parallel ^[20]. It uses Cognition's SWE-1.6 model plus frontier models from OpenAI, Anthropic, and Google ^[21]. Cognition has restructured pricing away from the old $500 per month plan: Free, Pro $20 per month, Max $200 per month, Teams $80 per month plus $40 per seat, and Enterprise (billed in Agent Compute Units) ^[20]. Cognition does not publish a current SWE-bench Verified score for the Devin agent, so its cell is n/r.

10. Augment Code

Best for: large enterprise codebases needing deep context and compliance.

Augment Code is a closed-source coding agent with IDE extensions, a CLI ("Auggie"), SOC 2 compliance, and a large-context "context engine" for big repositories ^[27]. It is multi-model (Claude, GPT, Gemini). Its best documented result is 65.4 percent on SWE-bench Verified, set in March 2025 by combining Claude 3.7 Sonnet and OpenAI o1, and 51.8 percent on SWE-bench Pro with Claude Opus 4.5 in 2026 ^[28]. Pricing is a flat Business plan at $100 per month (including $100 of usage and up to 50 seats) with custom Enterprise ^[27]. Sourcegraph's Amp is a comparable usage-based enterprise agent (default GPT-5.5) worth evaluating alongside it.

Underlying models and API prices

The table below lists the models these tools run and their published API prices, so you can estimate real usage cost. Prices are USD per 1,000,000 tokens, verified July 2026.

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Claude Sonnet 5 introductory pricing runs through August 31, 2026, after which it rises to $3 input and $15 output ^[5]. Gemini 3.1 Pro pricing is for prompts up to 200K tokens and rises above that ^[23]. Composer 2.5 also offers a faster variant at $3 input and $15 output ^[15].

SWE-bench Verified vs Terminal-Bench: how to read the scores

Two benchmarks matter here, and they measure different things. SWE-bench Verified is a human-validated set of 500 real GitHub issues; it scores the underlying model, so it is the fairest way to compare raw model quality (Fable 5 95.0 percent, Opus 4.8 88.6 percent, Sonnet 5 85.2 percent, Gemini 3.1 Pro 80.6 percent) ^[2][8]. Terminal-Bench scores a tool-plus-model combination on real command-line tasks, so it captures how good the harness itself is, not just the model ^[1]. Watch two traps. First, versions are not comparable: Terminal-Bench 2.1 is harder than 2.0. Second, vendors' self-reported numbers use different harnesses than the public tbench.ai board, which is why Anthropic cites 87.6 percent for Opus 4.8 while the community board shows 78.9 percent ^[1][6]. Artificial Analysis, using a single standardized harness, similarly places GPT-5.5 at 84.3 percent and Opus 4.8 at 84.6 percent on Terminal-Bench v2.1 ^[29]. For a tools comparison, the tool-specific Terminal-Bench 2.1 numbers are the most apples-to-apples.

Which AI coding assistant should you choose?

• Choose Claude Code if you want the highest ceiling on hard, autonomous, multi-file tasks and can run Opus 4.8 or Fable 5.
• Choose OpenAI Codex CLI if you already pay for ChatGPT, want the top Terminal-Bench score, or want an open-source harness.
• Choose Cursor if you want the best day-to-day in-editor flow with a fast built-in agent.
• Choose GitHub Copilot if you need one tool across many editors, or you are buying for a team or enterprise.
• Choose Gemini CLI, Aider, or Cline if you want free or open-source tooling and prefer to bring your own model.
• Choose Devin or Augment Code if you want to hand off whole tasks or need enterprise-grade context and compliance.

References

1. Terminal-Bench 2.1 leaderboard, tbench.ai. https://www.tbench.ai/leaderboard/terminal-bench/2.1 ↩
2. SWE-bench Verified leaderboard, llm-stats.com (updated 2026-07-01). https://llm-stats.com/benchmarks/swe-bench-verified ↩
3. SWE-bench Verified benchmark, vals.ai (2026-07-01). https://www.vals.ai/benchmarks/swebench ↩
4. Anthropic, Claude Code model configuration and defaults. https://code.claude.com/docs/en/model-config ↩
5. Anthropic, Claude model and plan pricing. https://platform.claude.com/docs/en/about-claude/pricing and https://claude.com/pricing ↩
6. Anthropic, Introducing Claude Opus 4.8. https://www.anthropic.com/news/claude-opus-4-8 ↩
7. Anthropic, Redeploying Fable 5 (Fable 5 and Mythos 5). https://www.anthropic.com/news/redeploying-fable-5 ↩
8. Google DeepMind, Gemini 3.1 Pro model card. https://deepmind.google/models/model-cards/gemini-3-1-pro/ ↩
9. OpenAI, Codex models. https://developers.openai.com/codex/models ↩
10. OpenAI, Codex pricing. https://developers.openai.com/codex/pricing ↩
11. OpenAI, Introducing GPT-5.5. https://openai.com/index/introducing-gpt-5-5/ ↩
12. OpenAI, API pricing. https://developers.openai.com/api/docs/pricing ↩
13. OpenAI Codex CLI, GitHub (Apache-2.0). https://github.com/openai/codex ↩
14. Cursor pricing. https://cursor.com/pricing ↩
15. Cursor, Composer 2.5. https://cursor.com/blog/composer-2-5 ↩
16. GitHub Copilot plans. https://github.com/features/copilot/plans ↩
17. GitHub, Copilot usage-based billing (AI credits). https://github.blog/news-insights/company-news/github-copilot-is-moving-to-usage-based-billing/ ↩
18. GitHub Copilot supported AI models. https://docs.github.com/en/copilot/reference/ai-models/supported-models ↩
19. Cognition, acquiring Windsurf. https://cognition.com/blog/windsurf ↩
20. Devin pricing (Windsurf is now Devin Desktop). https://devin.ai/pricing ↩
21. Cognition, SWE-1.6. https://cognition.com/blog/swe-1-6-preview ↩
22. Gemini CLI, GitHub (Apache-2.0). https://github.com/google-gemini/gemini-cli ↩
23. Google, Gemini API pricing. https://ai.google.dev/gemini-api/docs/pricing ↩
24. Aider LLM leaderboards. https://aider.chat/docs/leaderboards/ ↩
25. Aider, GitHub (Apache-2.0). https://github.com/Aider-AI/aider ↩
26. Cline, GitHub (Apache-2.0). https://github.com/cline/cline ↩
27. Augment Code pricing. https://www.augmentcode.com/pricing ↩
28. Augment Code, top open-source agent on SWE-bench Verified. https://www.augmentcode.com/blog/1-open-source-agent-on-swe-bench-verified-by-combining-claude-3-7-and-o1 ↩
29. Artificial Analysis, Terminal-Bench v2.1. https://artificialanalysis.ai/evaluations/terminalbench-v2-1 ↩
30. Google Cloud, Gemini Code Assist overview (Antigravity migration). https://docs.cloud.google.com/gemini/docs/codeassist/overview ↩