Verdict: Claude Code is the best AI agent for coding for most developers in 2026, with OpenAI Codex the better pick when cost and speed per task dominate. Two September 22 releases forced a re-ranking: Anthropic shipped Claude Opus 5.5 and made it Claude Code's default model the same day, putting Claude Code at the top of Artificial Analysis's independent Coding Agent Index with a score of 66 against 62 for Codex with GPT-6 Astra (Artificial Analysis, as tallied in MightyBot's September 24 ranking). OpenAI answered by releasing GPT-6 Sol and Luna at half their predecessors' prices, making Codex the per-task value leader. Cursor, still fine to use today, carries a November 12 model-supply deadline after OpenAI announced it will wind down Cursor's model access (OpenAI).
TL;DR
- Claude Code wins on quality and control: Opus 5.5 default, 66 on the independent Coding Agent Index, per-subagent model and effort control (Anthropic; Artificial Analysis).
- Codex wins on cost per task: $7.47 and 29.4 minutes with GPT-6 Astra, or $2.99 with the new GPT-6 Sol, against $13.00 and 1.1 hours for Claude Code with Opus 5.5 on the same index (Artificial Analysis; MightyBot).
- Cursor is the quality editor but a supply-risk bet after the November 12 shutoff notice (OpenAI).
- GPT-6 Sol and Luna cut API prices by 50% versus GPT-5.6 equivalents on September 22 (OpenAI).
Last verified: 2026-09-30.
Why the answer changed on September 22
Anthropic released Claude Opus 5.5 on September 22 and it became Claude Code's default Opus model in the same day's release (Anthropic). At default effort the model scores 52.5% on Anthropic's work benchmark, above 51.8% for the more expensive Fable 5.1 at max effort and 46.6% for Opus 5, and it beats GPT-5.6 Sol's top score by 11 points at about a third of the cost per task (Anthropic). Anthropic says Opus 5.5 uses fewer tokens per task than Opus 5, a net cost drop around 40%, and generates output more than 30% faster (Anthropic). Independent corroboration from early access users points the same way: a 680,000-line code migration completed in under a day, and a 200,000-line audit fixed in under three hours where Opus 5 took over 20 hours using 2.5x as many tokens (Snowflake).
OpenAI shipped the GPT-6 Sol and Luna models to Codex the same day, with API prices halved against GPT-5.6: Sol moved from $4 to $2 per million input tokens and $20 to $10 output, Luna to $0.10 and $0.50 (OpenAI). OpenAI reports Sol at high effort improves on its predecessor by 5.4 percentage points on AutomationBench at 58% lower cost per task, and outperforms Claude Opus 5 at maximum effort at about 9% of its cost, though OpenAI still calls GPT-6 Astra its best model across the board (OpenAI).
How the top coding agents compare
| Agent | Default model | Index score | Cost, time per task | Entry price |
|---|---|---|---|---|
| Claude Code | Opus 5.5 | 66 | $13.00, 1.1 h | From $20/mo, real volume at $100 Max |
| Codex | GPT-6 Astra (Sol, Luna in picker) | 62 (57 with Sol) | $7.47, 29 min ($2.99 with Sol) | Meaningful use at $20 Plus |
| Cursor | Multiple, OpenAI models leave Nov 12 | Strong editor UX | Varies | $20 Pro |
| Grok Build | Grok 4.7 | 56 | Not published | Subscription |
Scores and per-task costs are Artificial Analysis's Coding Agent Index, which scores each agent paired with its own model, as summarized on September 24 (Artificial Analysis; MightyBot). Note the effort asymmetry behind the headline benchmark: Anthropic reports Opus 5.5 at 66.4% on Terminal-Bench 4.0 at xhigh effort against 57.9% for GPT-6 Astra as reported by OpenAI at high effort, while Artificial Analysis's own rerun puts the two tied at 59.6% (Artificial Analysis). The honest reading is a narrow quality lead for Claude Code and a decisive efficiency lead for Codex.
Where Claude Code pulls ahead
Claude Code is the best AI agent for coding when the job is repository-shaped work and the bill can absorb a premium. It remains the only major agent where each subagent in one session can run a different model at a different effort level, and Anthropic paired the Opus 5.5 default with a one million-token context window at $4 per million input and $20 per million output tokens (Anthropic; platform.claude.com). GitHub's testing team measured Opus 5.5 solving more terminal tasks than Opus 5 in less than half the steps in VS Code, and one enterprise developer reported an unattended 18-hour overnight run across six repositories with minimal rework (Anthropic). For teams running deep custom workflows, the hooks, skills, and plugin stack is still the deepest harness in the category (MightyBot).
Where Codex is the better pick
Codex wins when cost and turnaround per task decide. Its GPT-6 Astra default finishes tasks for $7.47 in under half an hour on the independent index, GPT-6 Sol drops that to $2.99, and OpenAI's own AutomationBench tests put Sol above Opus-class quality at roughly 9% of Opus 5's per-task cost (Artificial Analysis; OpenAI). Sol also hits 68.8% on DeepSWE v1.1 at maximum effort per OpenAI's published figures (LiteLLM). GPT-6 Astra became the Codex default on September 4 and GPT-5.5 retires from ChatGPT and Codex on October 14 (OpenAI Codex changelog). For high-volume background work, issue-to-PR batches, and teams already on ChatGPT plans, that math is hard to argue with.
The rest of the field
Cursor still offers the smoothest editor-first agent experience, but it is now a supply-limited bet: OpenAI confirmed a proposed shutoff of Cursor's model access on November 12, 2026, following SpaceX's acquisition of Cursor's parent, so model availability depends on whatever Cursor secures next (OpenAI; CNBC). GitHub Copilot's cloud agent remains the pragmatic choice for issue-to-PR work where your code already lives, and both Sol and Luna appeared in its model picker the day they launched (GitHub). Google Antigravity is free for individuals and useful for multi-agent and browser tasks (Google Antigravity). Grok Build improved sharply, nearly doubling its Terminal-Bench 4.0 score to 37.6% on September 21, though that still trails the leaders by 20 points (MightyBot). If coding is one part of a broader personal-agent workflow, a model-agnostic harness such as Hermes Agent or OpenCode keeps your options open (MightyBot).
How to choose in one minute
- Maximum quality and deep custom workflows: Claude Code with Opus 5.5 (Anthropic).
- High-volume, cost-sensitive or overnight work: Codex, starting on GPT-6 Astra and switching routine tasks to GPT-6 Sol (OpenAI).
- Editor-first day-to-day coding: Cursor is still excellent, but confirm its model roadmap before committing past November (OpenAI).
- GitHub-native teams: Copilot with the Sol and Luna options now in the picker (GitHub).
Many heavy users run Claude Code for interactive depth and Codex for background volume, routing work by task type (MightyBot).
How we picked the keyword behind this comparison
The target phrase for this page was chosen the same way every topic on this site is chosen: by measurement, not instinct. We priced 656 keywords in the AI and developer-tooling space using DataForSEO volume and difficulty data. Only 72 (11.0%) cleared a winnable bar of 150-6,000 monthly searches, difficulty 20 or below, a genuine technical term, and at least three words (n=656, measured 2026-09-28 via DataForSEO). The winning keyword for this article clears that bar, and the comparison above was built to answer it directly. Our editorial and testing methodology is described on our how-we-work page.
FAQ
Q: What is the best AI agent for coding in 2026?
A: For most developers, Claude Code running Opus 5.5, which tops Artificial Analysis's independent Coding Agent Index at 66 (Artificial Analysis). Codex is the better choice when cost per task matters more than the last points of quality.
Q: Is Codex cheaper than Claude Code for agentic work?
A: Yes, per task: $7.47 and 29.4 minutes with GPT-6 Astra, or $2.99 with GPT-6 Sol, against $13.00 and 1.1 hours for Claude Code with Opus 5.5 on the same index (Artificial Analysis; MightyBot).
Q: What changed for AI coding agents on September 22, 2026?
A: Anthropic made Opus 5.5 Claude Code's default model, and OpenAI released GPT-6 Sol and Luna with API prices 50% below their GPT-5.6 equivalents (Anthropic; OpenAI).
Q: Is Cursor still a safe choice for coding agents?
A: It remains usable, but OpenAI announced a proposed November 12, 2026 shutoff of Cursor's model access after SpaceX's acquisition, so check Cursor's replacement model plans before long-term commitment (OpenAI).
Top comments (0)