Opus 5.5 vs Astra: Claude vs GPT-6 on Real Tasks and Costs
If you've had Anthropic's and OpenAI's pricing pages open side by side this month, the math probably looked like it settled itself. GPT-6 Astra costs 2.5x as much per token as Claude Opus 5.5, so Opus is the cheap one, you pick it, and you get your afternoon back.
Then an early hands-on head-to-head came in, and Astra finished two of three real jobs for less money than Opus (the kind of result that makes you put the calculator down and open a spreadsheet). Opus 5.5 still did the better work on all three.
That one test is the Opus 5.5 vs Astra decision in miniature, because the answer changes depending on whether you're paying for tokens, finished jobs, or work you'd ship without a second pass.
Opus 5.5 shipped on September 22, 19 days after Astra started rolling out on September 3, and I've spent the week since reading both launch posts, both sets of API docs and plan pages, Artificial Analysis's benchmark runs, and the hands-on tests from MindStudio and Nate Herk.
Every figure below links to or names its source, and every hands-on result is credited to the person who ran it. Whether you're choosing for coding, creative work, research, or long agent runs, you'll know which model to start with, which plan gets you in, and roughly what a real task will cost.
Opus 5.5 vs Astra: the short verdict
Claude Opus 5.5 is Anthropic's newest Opus model, priced at $4 per million input tokens and $20 per million output tokens. GPT-6 Astra is OpenAI's top model, at $10 and $50.
Opus 5.5 is the pick for coding, creative work, and research, and Astra is the pick for math and science, or when you need to run at max effort.
Choose Opus 5.5 if:
- You code in long agent sessions: it leads Terminal-Bench 4.0 at each model's best setting (66.4% to 57.9%), and at its default medium effort it costs less per task than Astra on Artificial Analysis's index.
- Design taste counts: in MindStudio's head-to-head write-up, Opus 5.5 won the quality call on all three creative tasks.
- You want the full model on a $20 plan: Claude Pro includes it, while ChatGPT's $20 Plus plan only gives you Astra inside Work and Codex.
- You do research-heavy knowledge work: it scores higher on Humanity's Last Exam with tools and on GDPval-AA.
Choose Astra if:
- Your work is math, science, or formal proofs: it posts 97.6% on FrontierMath Tier 4 and 64.6% on Terminal-Bench-Science.
- You run business-workflow agents: it edges Opus 5.5 on AutomationBench (41.4% to 40.0%), and OpenAI calls it the world's best computer-use model.
- You need max effort specifically: Astra uses far fewer output tokens at the top setting, so it's the cheaper model per task up there.
- You want a usable draft fast and cheap: Astra finished two of MindStudio's three creative jobs faster and for less money, even though Opus 5.5 won on quality.
- You run light jobs at low effort: at the lowest setting, Astra scores 46 to Opus 5.5's 42 on Artificial Analysis's index.
- Your team already lives in ChatGPT and Codex: switching tools has a cost that no benchmark shows.
My take: for most coding and everyday knowledge work, Opus 5.5 is the better default right now, mostly because it scores higher and costs less at its default medium effort. Astra earns its place on math and science, and at max effort it's the cheaper model per task.
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Specs and pricing side by side
The API prices look simple until you get to caching, long prompts, and plans, so the table below puts all of it in one place.
Opus 5.5's prices come from Anthropic's launch post, and its context window, output cap, and cutoff come from Anthropic's model docs. Astra's specs and prices are from OpenAI's Astra model page. Both models cap output at 128K tokens.
OpenAI announced Astra's rollout on September 3, as CNBC reported that day.
What each plan gets you
On Anthropic's side, Opus 5.5 comes with Claude Pro at $20 a month ($17 a month if you pay annually). Claude Free doesn't include Opus, and Max starts at $100 a month for 5x or 20x Pro's usage.
On OpenAI's side, ChatGPT Plus costs $20 a month and includes Astra in ChatGPT Work and Codex. GPT-6 Pro in regular chat, which runs on Astra, needs a Pro, Business, or Enterprise plan.
Pro $100 gets you 5x Plus usage and 50 GPT-6 Pro messages a week (shared with the older GPT-5.6 Sol Pro). Pro $200 gets 20x usage and 200 messages a week, though OpenAI paused new Pro $200 sign-ups on September 10, 2026.
Plus limits are tight: OpenAI estimates 5 to 45 local Astra messages per five-hour window in Work and Codex on Plus.
So if you want the flagship in a regular chat window, Claude is the $20 option and ChatGPT's cheapest individual plan is the $100 one. If you're still weighing the two apps for everyday use, this Claude vs ChatGPT comparison covers writing, files, voice, and the rest of the daily stuff.
Meet the two models
Claude Opus 5.5
Opus 5.5 is the first model in Anthropic's Claude 5.5 family. Anthropic says it costs 40% less to run than Opus 5 on typical workloads and generates output more than 30% faster. Our Claude Opus 5.5 explainer covers the rest of what changed in the release.
Anthropic also improved how it writes, so it puts the key point first and follows your style rules. The launch post shows side-by-side examples where Opus 5.5 leads with the answer and Opus 5 takes longer to get there.
Two quirks are worth knowing before you build on it. Thinking is always on (you can't switch it off), and Anthropic's docs set its default effort to medium.
It also ships with stricter safeguards. Most cybersecurity tasks get re-routed to Opus 4.8, so security researchers will hit walls until Anthropic opens its Cyber Verification Program to Opus 5.5 in the coming weeks.
GPT-6 Astra
Astra is OpenAI's flagship, and OpenAI's announcement calls it the world's most intelligent and aligned model. Its showcase numbers lean toward math and abstract reasoning: 99.9% on ARC-AGI-3 and 97.6% on FrontierMath Tier 4.
It also meets the Critical threshold for cybersecurity under OpenAI's Preparedness Framework, so it runs with extra safety checks. OpenAI says those checks can pause a task in ChatGPT or Codex and stop it outright in the API.
On September 22, the same day Opus 5.5 launched, OpenAI added GPT-6 Sol and GPT-6 Luna to the family.
Real-work results: how they did on the same tasks
MindStudio published a write-up of one creator's 12-task head-to-head, where both models got identical prompts and ran in their own harnesses on high effort. It tracked quality, run time, and dollar cost, and it details the first rounds.
Opus 5.5 won the quality call on all three. The creator described its sizzle reel as tightly synced to the beat and layered with overlays, while Astra's cut opened quiet and took several seconds for the music to kick in.
Meanwhile, Astra, the model with 2.5x the token price, came out cheaper on two of the three runs.
Astra's business build and working style
On a business test built from mock company data, Astra produced an investor deck, a financial report, a dashboard, and a landing page in one request. The write-up calls the output functional but plain, with a 17-slide deck and only basic sum formulas in places.
Astra's Codex-style harness also stopped mid-task to ask a clarifying question, which the creator liked because it tailors the result. One more note from the same person: Astra's video editing seemed worse than in their earlier tests, with no confirmed cause.
Nate Herk's video runs both models through 12 tasks, opening with the same website, sizzle reel, Instagram reel, and business rounds, then moving on to playable games, a coding challenge, and a book-site redesign.
He logs the time and estimated API cost for each one, and by his own description, Astra wins some rounds too.
MindStudio's results come from one creator, one run per task, and each model in its own tool, so a different harness or effort setting could flip a result. It's a strong signal on creative taste and a clear warning that list price and job cost can point in opposite directions.
Opus 5.5 vs Astra benchmarks: coding, computer use, and reasoning
These are the benchmarks where both companies (or an independent lab) reported a score for each model.
The first six rows come from Anthropic's launch table, which uses OpenAI's reported Astra scores where they exist and Zapier's leaderboard for AutomationBench (the Astra figures match OpenAI's own table wherever both list one). The last row comes from Artificial Analysis.
Coding
Opus 5.5 has its clearest lead here. It scores 66.4% on Terminal-Bench 4.0 to Astra's 57.9%, and Anthropic says it matches Astra's Terminal-Bench score for about 40% of the cost.
FrontierCode is much closer (54.4% to 53.3%), though Anthropic says Opus 5.5 at default effort beats Astra's top FrontierCode score for about a fifth of the cost per task.
Both Terminal-Bench figures are each model's best setting (Opus 5.5 at xhigh effort, Astra at high), per Anthropic's footnote, so "better at coding" still depends on the kind of coding and the effort you pay for.
Most developers use these models inside a coding agent, so the harness shapes your results as well. If you haven't settled on one, start with this list of AI coding agents.
Computer use
Anthropic reports Opus 5.5 at 81.8% on OSWorld 2.1 (partial score), and OpenAI reports Astra at 72.6% on the OSWorld 2.0 offline set, an earlier version of the test.
The setups differ even for the same model. Opus 5 scores 74.0% in Anthropic's table and 70.2% in OpenAI's, so compare each company's OSWorld numbers only against its own.
AutomationBench, which Zapier runs, gives a cleaner read, and Astra edges ahead 41.4% to 40.0%. Anthropic says its safeguards counted as failures in that run, which pulled its score below what it would reach in practice.
Reasoning and knowledge work
Opus 5.5 leads on Humanity's Last Exam with tools (67.7% to 57.2%) and on GDPval-AA, a test of real work across 44 occupations (1846 to 1542 Elo).
Astra takes the formal, rule-bound stuff. It leads Terminal-Bench-Science 64.6% to 58.7%, and OpenAI reports 96.0% on GPQA Diamond and 97.6% on FrontierMath Tier 4, two tests Anthropic didn't publish for Opus 5.5.
Artificial Analysis's overall index
On Artificial Analysis's Intelligence Index (version 4.3.2, 10 evaluations rolled into one score), Opus 5.5 at max effort scores 58 to Astra's 53. It's faster there too, at 93 output tokens per second to Astra's 59 as of late September.
Anthropic's own launch post admits that benchmark margins have become a less reliable guide to real-world differences at this level.
Real cost per task: why list price misleads
Astra's per-token price is 2.5x Opus 5.5's, but that only carries through to the bill when both models use a similar number of tokens, and from high effort up they don't.
Artificial Analysis ran both models at every effort level and logged the weighted average cost per task on its index:
At medium effort, which is Opus 5.5's default, Opus scores a point higher than Astra and costs about 13% less per task.
From high effort up, Astra becomes the cheaper model per task, and the difference grows at max. There, Opus 5.5 averages about 119,000 output tokens per task to Astra's 27,000, so it lands at $5.98 a task to Astra's $3.26.
Opus still scores higher at max (58 to 53), but you pay about 83% more for those five points.
Match the two on score and Opus usually comes out ahead on price. Opus 5.5 at high effort (54) beats Astra at max effort (53) for $1.82 a task against $3.26.
Caching and long prompts
Caching tilts things further toward Opus for agent and coding work, where the same context gets reread constantly. Anthropic says cache reads make up most of the cost of that kind of work, and Opus 5.5 charges $0.20 per million cached tokens to Astra's $1.00.
Long prompts are the other trap. OpenAI charges 2x on input and 1.5x on output for the whole request once a prompt passes 272,000 tokens, while Anthropic bills Opus 5.5's full 1M window at the standard rate.
How to keep the bill down
For everyday work, run Opus 5.5 at medium or high effort and save max effort for the problems that stump it at lower settings. For Astra, OpenAI's help center suggests starting low, noting that Astra at low effort can outperform OpenAI's older GPT-5.6 Sol at high.
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Which one should you pick for your work?
Pick Opus 5.5 for coding, creative work, long documents, and a $20 budget, and Astra for math, science, and formal reasoning.
- Coding and long agent runs, Opus 5.5: it leads Terminal-Bench 4.0, costs less at default effort, and Anthropic's early testers describe long unattended runs (Clio says it stayed on a six-repo task for over 18 hours).
- Design, video, and anything where taste counts, Opus 5.5: it won every creative quality call in MindStudio's write-up, including the two runs where it cost more.
- Math, science, and formal reasoning, Astra: it leads Terminal-Bench-Science and posts top scores on FrontierMath and GPQA Diamond, two tests Anthropic didn't report for Opus 5.5.
- Desktop and business-workflow agents, a slight edge to Astra: it scores higher on AutomationBench and OpenAI calls it the world's best computer-use model, but the margin is small enough that you should test both on your own apps.
- Very long documents or codebases, Opus 5.5 on cost: both handle about a million tokens, but Astra's price jumps once a prompt passes 272,000 tokens.
- Security research, neither out of the box: Opus 5.5 hands most cyber tasks to Opus 4.8, and Astra refuses advanced work like proof-of-concept exploits until OpenAI widens access.
- Tight budget on a consumer plan, Opus 5.5: $20 Claude Pro gets you the full model in chat, and on an individual plan, Astra in chat starts at $100.
If you're open to other assistants entirely, start with these Claude alternatives or these AI tools like ChatGPT.
Plenty of teams use both. Some assistants let you switch per task, and Lindy, an AI teammate that works in Slack, lets you choose the model for each task on every plan.
Pick the model that finishes your work for less
The Opus 5.5 vs Astra choice comes down to two questions: what kind of work fills your week, and what effort level you'll run it at.
If you want to settle it for your own team, take three real tasks from last week and run each one on both models at the default effort. Write down the minutes, the dollars, and whether you'd ship the result. An afternoon of that will tell you more than any leaderboard.
For most coding and knowledge work, I'd start with Opus 5.5 at medium effort. If your week is full of math, science, or heavy desktop automation, give Astra the first shot.
Frequently asked questions
Is Opus 5.5 better than Astra?
Opus 5.5 is better than Astra for most coding and knowledge work on current benchmarks, leading Terminal-Bench 4.0 (66.4% to 57.9%) and Artificial Analysis's index (58 to 53). Astra is better at math and science and holds a slight AutomationBench edge (41.4% to 40.0%).
Is Opus 5.5 cheaper than Opus 5?
Yes, Opus 5.5 is cheaper than Opus 5, at $4 and $20 per million input and output tokens against Opus 5's $5 and $25. Cache reads are 60% cheaper at $0.20, and Anthropic says it costs 40% less than Opus 5 on typical workloads at default settings.
Is Astra good?
GPT-6 Astra is a very strong model, with near-perfect scores on FrontierMath Tier 4 (97.6%) and ARC-AGI-3 (99.9%). Its weak spots are the per-token price and, in MindStudio's head-to-head write-up, creative taste on design and video tasks.
Which version of Opus is best?
Claude Opus 5.5 is the best Opus to start with, since it's the newest Opus model and Anthropic's docs recommend it for most workloads. For the hardest reasoning and long-horizon agent work, Anthropic points to Claude Fable 5.1, which costs $10 and $50 per million tokens.
Our Opus 5.5 vs Fable 5.1 comparison covers the cases where Fable 5.1 is worth the extra cost.
Is Astra worth the higher price?
Astra's higher token price pays off on math, science, and max-effort work. At max effort it uses far fewer output tokens than Opus 5.5, so it costs less per task, while at medium effort Opus 5.5 scores slightly higher for about 13% less, per Artificial Analysis.
Can you use Opus 5.5 or Astra for free?
Neither model is available on a free plan. Claude Free doesn't include Opus, and Astra starts with ChatGPT Plus at $20 a month in Work and Codex. Opus 5.5 comes with Claude Pro at $20 a month.
