OpenAI vs Claude Opus | GPT-5.5 and 4.8 Performance & Pricing Comparison

Why Compare OpenAI and Claude Opus Now

From spring to early summer of 2026, both companies successively refreshed their flagships. OpenAI launched GPT-5.5 on April 23, 2026, for ChatGPT users, followed by API access on April 24. Source

In response, Anthropic released Claude Opus 4.8 on May 28, 2026. Source

Reports indicate that Opus 4.8 outperformed OpenAI's GPT-5.5 and Google's Gemini 3.1 Pro on multiple synthetic benchmarks, framing the competition as a battle over "which is the next flagship." Source

As a result, searching for "openai claude opus" reflects an intent less about consumer chat app usability and more about evaluating raw model performance, pricing, and agent capabilities. This article focuses precisely on those dimensions.

The Models at a Glance — Claude Opus 4.8 vs. GPT-5.5 Specs

Here are the basic specs of both models side by side. Prices are in USD, excluding tax, as of June 5, 2026.

GPT-5.5 has a context window of 1M tokens and a maximum output of 128,000 tokens. Source

Claude Opus 4.8 is also positioned as a flagship model with large-scale context capabilities. Source

In terms of context length, both have reached the 1M token range, meaning neither has a clear advantage in "reading long documents at once." The differences emerge in pricing and agent performance, as discussed below.

Pricing Comparison — Opus 4.8 Leads on Output Cost

Here is a comparison of API token pricing.

Claude Opus 4.8 is priced at $5 input / $25 output, while the lower-latency Fast Mode is $10 input / $50 output. Source

GPT-5.5 is $5 input / $30 output, and the higher-tier GPT-5.5 Pro is $30 input / $180 output. GPT-5.5 also offers pricing options such as batch/flex usage at half the standard price and priority processing at 2.5x. Source

Input pricing is the same at $5 for both, but Opus 4.8's output at $25 is about 17% cheaper than GPT-5.5's $30 — a meaningful difference in practice. For long-form generation or code generation where output tokens add up, this small gap compounds. Meanwhile, GPT-5.5 Pro's costs spike significantly, so using it selectively for specific tasks is the realistic approach.

Benchmark Comparison — Agentic Coding and PC Automation

What both companies now emphasize is not single-turn Q&A, but agentic performance — the ability to autonomously complete tasks end-to-end.

Here is a summary of published figures:

• Terminal-Bench 2.1 (terminal operations): GPT-5.5 is reported at 83.4% on the Codex CLI harness. Anthropic positions Opus 4.8 as exceeding this level on the same benchmark. Source
• Online-Mind2Web (browser/PC automation): Claude Opus 4.8 is cited by testers as achieving 84%. Source
• Legal Agent Benchmark (legal agent tasks): Opus 4.8 is described as the first model to break the 10% barrier overall. Source

On the GPT-5.5 side, OpenAI highlights its strength in end-to-end workflows covering code writing and debugging, online research, data analysis, document and spreadsheet creation, and software operation. Source

An important caveat: these scores are measured by each vendor under their own harness and conditions. Since different harnesses (execution environments) produce different numbers, it is safer to conduct your own reproduction tests on your actual workflows rather than taking the rankings at face value.

Agent Feature Differences — Dynamic Workflows vs. Codex

Alongside raw performance, how you actually run an agent matters just as much.

Claude Opus 4.8 adds Dynamic workflows for Anthropic's coding environment Claude Code, and Effort control for chat and business use cases — allowing you to adjust the depth of responses. Additionally, the Messages API now supports inserting system instructions at any position within the message array. Source

OpenAI describes GPT-5.5 as "the smartest and most intuitive model yet," emphasizing autonomous end-to-end task execution across tools. For coding, the Codex-based harness remains central to evaluation. Source

Here are the selection criteria:

1. If you want to delegate your entire development workflow from the terminal or codebase, Claude Code + Opus 4.8's Dynamic workflows is a strong candidate.
2. If your development already revolves around ChatGPT and Codex, migrating to GPT-5.5 will be smoother from an integration standpoint.
3. If you need fine-grained control over response costs, consider Opus 4.8's Effort control or GPT-5.5's batch/flex pricing options.

Context and Output — Performance in the 1M Token Era

For use cases that require processing large codebases or documents all at once, context length is critical. As noted, both Opus 4.8 and GPT-5.5 have reached the 1M token scale, making them comparable on this axis.

GPT-5.5's maximum output is 128,000 tokens, supporting bulk output of long reports or large code diffs in one go. Source

However, GPT-5.5 has a pricing policy where prompts exceeding 272K tokens incur 2x input and 1.5x output charges for the entire session. Workloads that consistently send very long prompts need to be designed with this threshold in mind. Source

In other words, while both models are tied on "can they read long text," there is a difference in "what it costs to keep sending long text." Whether you run on full context at all times or pass only the relevant portion will determine which model is more optimal.

Choosing by Use Case — Coding / Cost / Ecosystem

Here is a decision table summarizing the comparison by use case.

If coding and agentic workflows are your primary focus, Claude Opus 4.8 is the more accessible choice thanks to its benchmark advantage and lower output pricing. On the other hand, if your development and business workflows are already built around ChatGPT, sticking with GPT-5.5 and leveraging its ecosystem compatibility may result in lower total cost.

Ultimately, the fastest way to decide is to run both models once on your representative tasks and measure output quality and token consumption directly. Specs and pricing change quickly, so always check each company's official site for the latest figures before committing to a contract or production deployment.

Frequently Asked Questions (FAQ)

Q. Which ultimately performs better — OpenAI or Claude Opus?

Anthropic has published results showing Claude Opus 4.8 outperforms GPT-5.5 on multiple synthetic benchmarks, but these are vendor-reported values. Source Rankings can shift depending on measurement conditions (harness), so testing on your specific use cases is the most reliable approach.

Q. Which API is cheaper?

Input pricing is the same at $5 / 1M tokens for both. For output, Claude Opus 4.8 is $25 and GPT-5.5 is $30, making Opus 4.8 slightly cheaper. Source GPT-5.5 Pro at $30 input / $180 output is significantly more expensive, so limiting it to specific high-value tasks is the practical approach. Source

Q. Is there a difference in context length?

Both Claude Opus 4.8 and GPT-5.5 are in the 1M token range. They are roughly equal in "can they read long text," but GPT-5.5 has a pricing surcharge for prompts over 272K tokens, so cost structures differ for workloads that regularly use very long contexts. Source

Q. I can't decide which to use — what should I do?

If you prioritize coding, agents, and output cost, Claude Opus 4.8 is the starting point. If you prioritize existing ChatGPT / Codex integration, GPT-5.5 is where to begin. We recommend trying your representative tasks on both using free or low-cost tiers and choosing the one that fits your use case.

Sources (Primary Information)

• Anthropic — Claude Opus 4.8 (accessed: 2026-06-05)
• OpenAI — Introducing GPT-5.5 (accessed: 2026-06-05)
• OpenAI API — GPT-5.5 Model (accessed: 2026-06-05)
• TradingKey — Claude Opus 4.8 Surpasses GPT-5.5 and Gemini 3.1 Pro (accessed: 2026-06-05)