Best AI for coding: Claude Opus 5.5 tops 15 models at 61.7, and DeepSeek gets 77% of that score for 3% of the cost

Which AI is best for coding right now?

Claude Code with Claude Opus 5.5 is the best AI for coding right now, but only just. On the Artificial Analysis Coding Agent Index, read on 31 October 2026, it beat Copilot Fusion by 1.8 points and Devin's two-model run by 0.2. It's also one of the most expensive, at $11.42 of API spend for each task. The chart below puts the score of each pair against what it cost.

The orange line is the cost frontier. Every pair that sits on it scores higher than anything that costs less. Five of the pairs on the chart make it onto the line: GPT-6 Luna, DeepSeek V4.1 Flash, GPT-6.1 Sol, Copilot Fusion and Claude Opus 5.5. The Gemini, Grok, GLM and Kimi pairs all sit below it, and that means a cheaper pair beats each one of them.

The index is an average of three tests with 290 tasks in all, and it runs each of the tasks three times. FrontierCode asks if a maintainer would merge the change that the agent made to a real repo. Terminal-Bench 4.0 gives it 66 jobs to do in a shell. SWE-Atlas QnA asks it 124 questions about how a codebase works. We left out the Devin pairs that mix two models in one run, and we left out Meta's Muse Code, because we couldn't confirm its price.

Google's Gemini 4 Carbon scored 59.4 in Antigravity CLI, and that would put it in third place. You can't use it yet. In its announcement on 28 October, Google said that Carbon goes first "to a subset of cyber defenders," and that developers and consumers will get it later. It didn't give a date.

Which coding AI is the best value?

DeepSeek V4.1 Flash is the best value for coding. When it ran in Codex, it scored 47.3 for $0.39 a task, and no pair that cost less scored higher. That's 77% of what Claude Opus 5.5 scored, for about 3% of what it cost.

DeepSeek has one big hole. It passed only 28.3% of the shell jobs in Terminal-Bench, while Opus passed 63.1% of them. On FrontierCode, which is the repo test, it beat every one of the OpenAI pairs, at 52.6%. So use it for patches and for questions about your code, and don't hand it a long job in a terminal.

GPT-6.1 Sol is the middle pick. It got 88% of the top score for 13% of the cost, so a run with Opus costs about 7.6 times as much as one with Sol. Copilot Fusion gets the closest to the top. GitHub put it this way in its changelog: "Copilot Fusion Max scored 60, within two points of Claude Code with Opus 5.5 Max." Fusion is a router that picks a model for each of your prompts, and Artificial Analysis lists Anthropic and OpenAI as the makers of the models it called.

Per-token price can mislead you. Claude Sonnet 5.5 costs half as much per token as Opus 5.5 does, yet its runs cost more, at $13.30 a task against $11.42. That's because it took longer. Its average run took 79.7 minutes, and the Opus run took 61.0.

Which plan gets you the best coding AI for $20 a month or less?

Claude Pro is the best coding plan at $20 a month, because it includes Claude Code, and Claude Code uses Opus 5.5 by default. There's a catch. Anthropic's model docs say that Opus 5.5 runs at "medium" effort by default, and the index score came from a run at max effort.

Many people won't pay per token at all, and Artificial Analysis says as much on its own page: "Many users will access coding agent harnesses through subscription plan offerings rather than pay-per-token." The table lists the API price for each model, then the cheapest plan that runs it inside a coding agent. It's as of 31 October 2026, in the US.

ChatGPT Plus is the better $20 plan if you want more runs and can live without the top score. Sol costs about a seventh as much per task as Opus does. OpenAI's Codex pricing estimates that you get 15 to 160 local messages every five hours on Sol, and it says that's not a fixed limit. Google AI Pro, at $19.99 on Google's plans page, gets you Antigravity with Gemini 4 Argon, which sits below the Claude, Copilot and OpenAI pairs. If Pro runs out for you, Claude Code pricing covers the $100 and $200 Max plans.

GitHub Copilot Pro is the cheapest of the strong options. It costs $10 a month and it comes with $15 of AI credits, and Fusion bills each model that it calls at that model's own rate. On its plans page, GitHub lists Claude Opus 5.5, GPT-6.1 Sol, Gemini 4 Argon, Grok 4.7 and Kimi K3 on every plan.

What is the best free AI for coding?

GitHub Copilot Free is the best free AI for coding. On 28 October, GitHub put Fusion on "all Copilot plans," and the free plan comes with "Limited chat and agent usage." You won't get many runs out of it, but you do get the router that scored 59.9.

There are two other free routes. On ChatGPT Free, you get Codex in the desktop app with GPT-6 Luna, which scored 31.1, though it's subject to rollout. Google's Antigravity is free to start, with "Basic weekly rate limits" and "Unlimited Tab completions." Its free tier doesn't say which models you get.

Claude's free plan doesn't include Claude Code. Neither does Google AI Plus at $4.99. The top pair, Claude Code with Opus 5.5, starts at $20.

Does the coding tool matter as much as the model?

The model sets most of the score, and the tool moves it a little. DeepSeek V4.1 Flash scored 47.3 when it ran in OpenAI's Codex and 46.3 when it ran in DeepSeek's own harness. Devin's CLI paired Opus 5.5 with GPT-6 Luna, and it scored 61.5 for $8.00 a task. That's 0.2 points below Claude Code, at 70% of the cost.

Cursor shows up on most of the "best AI coding tools" lists, but it has no row in the index. Its pricing page lists a free tier, Plus at $8 a month with "Only Grok models," Premium at $30, Super at $100 and Ultra at $200. Above Plus, it runs the models of other labs "at API list price." So in Cursor, the model you pick sets both your score and your bill.

Pick the model first, using the table above. Then use the agent that its maker ships, because that's the pair the index measured. AI for coding covers how to check what any of them hands back to you before you merge it.

Why SWE-bench scores no longer pick the winner

SWE-bench can't rank today's models, because its boards don't list them. When we read Scale's SWE-bench Pro board on 31 October 2026, it had no entry for Claude Opus 5.5, GPT-6.1 Sol or Gemini 4 Argon. Its leader was Muse Spark 1.1, at 61.50%.

One of the page-one results for "best AI for coding" still quotes 80.8% on SWE-bench Verified for Claude Opus 4.6. Anthropic has shipped Opus 4.7, 4.8, 5 and 5.5 since then. A score that old can't tell you much about what to buy today.

Where Whizi fits, and where it loses

Whizi is a chat app, not a coding agent or an IDE. It can't open your repo, run a terminal or edit your files, and it has no API, so use Claude Code, Codex or Copilot for the work this index measures. Its chat models run at minimal reasoning effort by default, so don't expect the max effort scores above. It fits one job, which is to ask two models the same coding question before you pay for an agent. Whizi Pro, at $29.99 a month, reaches Claude Opus 5.5, Claude Sonnet 5.5, GPT-6.1 Sol, DeepSeek V4.1 Flash, Grok 4.7 and Kimi K3 in side by side chats, and credits per message vary by model and can change. The coding guide shows how it works.