We build software with AI every day. Not as an experiment, not for a demo - for production code that real users depend on. Over the past few weeks, we've been running three different AI coding setups inside Cursor side by side, and the results are worth sharing.
The three contenders:
- Cursor's built-in agent (powered by Claude Opus 4.6)
- OpenAI Codex 5.3 running as an extension in Cursor
- Claude extension (with Opus 4.6) running as an extension in Cursor
Same developer. Same codebase. Same types of tasks. Different tools. Here's what we found.
TL;DR for the impatient
| Quality | Speed | Cost | Daily usability | |
|---|---|---|---|---|
| Cursor (Opus 4.6) | Best | Fast | Expensive | Great |
| Codex 5.3 extension | Very good | Fast | Cheapest by far | Great |
| Claude extension (Opus 4.6) | Good | Slowest | Expensive | Frustrating |
If you want the short version: Codex 5.3 wins on price-to-quality ratio. It's not even close.
Cursor with Claude Opus 4.6: the gold standard (at a price)
Let's start with the best outcome. Cursor's native agent, running on Claude Opus 4.6, consistently produces the highest quality code.
It understands context deeply. It makes fewer mistakes. When you give it a complex multi-file refactor, it tends to get the whole picture right on the first try. Edits are clean, it respects your existing code style, and it rarely introduces regressions.
The problem? Cost.
Whether you're on a Cursor subscription plan or piping your own Anthropic API key, Opus 4.6 is expensive to run. On the Cursor Pro plan, you'll burn through your fast request quota quickly if you're doing anything non-trivial. With an API key, the token costs add up fast - especially on larger codebases where every request carries significant context.
For teams that ship fast and need the best possible AI assistance, this is still the setup to beat. But not everyone can justify the spend, and that's where things get interesting.
Codex 5.3 as a Cursor extension: the surprise winner
This one caught us off guard.
OpenAI's Codex 5.3, running as an extension inside Cursor with High Thinking enabled, delivers quality that's on par with Claude Opus 4.5 - and in some cases better. It handles complex tasks well, follows instructions accurately, and produces clean, idiomatic code.
But here's the kicker: it's absurdly cheap.
On the $20/month OpenAI subscription, we couldn't hit the 5-hour usage limit. Not because we weren't trying - we were using it heavily, all day, for real development work. The limit just never came. For a tool that performs at this level, that's remarkable value.
The experience feels snappy. Responses come back quickly. It picks reasonable approaches to problems. It doesn't over-engineer solutions or go on weird tangents. It just... works, consistently, at a fraction of the cost.
If you're a solo developer or a small team watching your budget, this is the setup to try first. You get 90% of the quality at maybe 20% of the cost. That math is hard to argue with.
Claude extension in Cursor: the disappointing option
We had high hopes for this one. Same Opus 4.6 model, just accessed through Anthropic's official Claude extension instead of Cursor's native integration. In theory, same brain, same results.
In practice? Not even close.
The cost problem. On the $20/month Anthropic subscription, we hit the 5-hour usage limit in about 30 minutes. Thirty minutes. That's barely enough time to get through a single feature implementation. We upgraded to the $100/month plan, and that was more reasonable - we didn't hit the limit there. But $100/month is a lot to spend on a coding assistant that underperforms the native Cursor experience.
The speed problem. The Claude extension was noticeably slower than both Cursor's native agent and Codex. Every interaction felt like it had extra latency. When you're in a flow state, that friction is real. You start hesitating to ask questions or request changes because you know you'll be waiting.
The "strange paths" problem. This was the most frustrating part. The Claude extension would often take bizarre, roundabout approaches to solve problems. Where Cursor's native agent would make a clean, direct edit, the extension would sometimes refactor things that didn't need refactoring, create unnecessary abstractions, or take three steps to accomplish something that should have been one.
We're not sure why this happens. It could be differences in how context is passed to the model, differences in the system prompts, or differences in how edits are applied. Whatever the cause, the result is that the same model (Opus 4.6) behaves differently depending on the integration layer around it.
Of the three options we tested, this was consistently the worst experience. Not terrible - it still produces working code. But given the cost and the alternatives available, it's hard to recommend.
Why the same model performs differently
This is worth calling out because it surprised us too.
Claude Opus 4.6 through Cursor's native agent and Claude Opus 4.6 through the Claude extension are hitting the same underlying model. Yet the results diverge. This tells you something important: the integration layer matters as much as the model itself.
How context is gathered, how the codebase is indexed, how edits are proposed and applied, what system prompts are used, how conversation history is managed - all of these details shape the output. Cursor has spent years optimizing this pipeline. That optimization shows.
It's similar to how two different cars can use the same engine but deliver very different driving experiences. The engine matters, but so does everything around it.
The cost breakdown (real numbers)
Let's make the comparison concrete:
Cursor Pro ($20/month)
- Includes fast requests with Opus 4.6
- Burns through quota on heavy usage days
- Best quality output of anything we tested
- Worth it if you use the full Cursor ecosystem
Codex 5.3 via OpenAI ($20/month)
- Couldn't reach the 5-hour limit with heavy daily use
- Quality comparable to Opus 4.5 or better
- Best value proposition by a wide margin
- High Thinking mode is the sweet spot
Claude extension via Anthropic ($20/month)
- 5-hour limit hit in ~30 minutes
- Effectively unusable at this tier for real work
Claude extension via Anthropic ($100/month)
- Didn't hit the limit
- But slower and quirkier than the other two options
- Hard to justify when Codex 5.3 is $80/month cheaper and competitive on quality
What we actually recommend
If budget is no concern: Cursor Pro with Opus 4.6 (native). It's the best AI coding experience available right now, full stop.
If you want the best value: Codex 5.3 as a Cursor extension with High Thinking. $20/month for near-top-tier quality with generous usage limits. This is what we'd recommend to most developers.
If you're already paying for Claude Max: Use it through Cursor's native integration, not the Claude extension. The integration quality difference is real.
Skip the Claude extension for now. Unless Anthropic significantly improves the extension's speed and context handling, you're paying more for a worse experience.
What this means for the AI coding landscape
A few takeaways from running this comparison:
Price and quality are decoupling. The most expensive option isn't always the best. Codex 5.3 at $20/month competing with Opus 4.6 at multiples of that price signals that the market is getting more competitive.
Integration quality is a moat. Cursor's native experience being better than extensions using the same model shows that the IDE integration layer is where real differentiation happens. It's not just about which LLM you plug in.
Usage limits vary wildly. A $20/month plan that lasts 30 minutes vs. one that lasts all day - these are completely different products even though they're priced the same. Always test the limits before committing.
The landscape shifts fast. These observations are from February 2026. By the time you read this, there might be new models, new pricing, new integrations. The principles (test before you commit, integration matters, price isn't quality) will hold. The specifics will evolve.
Our setup going forward
We're keeping Cursor Pro as our primary tool. The native Opus 4.6 experience is unmatched for complex work.
For longer sessions and budget-sensitive projects, we reach for Codex 5.3. The quality-to-cost ratio is too good to ignore.
The Claude extension is on the bench. We'll revisit it when the speed and integration improve, but right now it doesn't earn a spot in the daily workflow.
The best AI coding setup in 2026 isn't about picking the "smartest" model. It's about picking the right combination of model, integration, and pricing that lets you ship code without friction - or financial stress.
We're building Test-Lab.ai, an AI-powered browser testing platform. Our opinions on AI coding tools come from using them every day to build and ship production software.