> ## Documentation Index > Fetch the complete documentation index at: https://docs.capriole.ai/llms.txt > Use this file to discover all available pages before exploring further. # Claude vs ChatGPT: Fable 5.1, Opus 5.5 and GPT-6 Astra > Compare Claude Fable 5.1 and Opus 5.5 with GPT-6 Astra: what each vendor says they do best, plan and API prices, and how to use both in one chat for USD 8. Claude and ChatGPT each lead in different work, so the practical answer is to use both. Anthropic positions **Claude Fable 5.1** for demanding reasoning and long-horizon agentic work, and **Claude Opus 5.5** for long-running agentic coding and knowledge work. OpenAI calls **GPT-6 Astra** its most capable model for the most demanding work. Capriole AI gives you all three, plus **Gemini 4 Argon**, in unlimited web chat for **USD 8 a month**. The same account includes an API that costs up to 92% less than official API prices, with one key for apps and coding agents. ## Claude vs ChatGPT at a glance | | Claude (Anthropic) | ChatGPT (OpenAI) | | - | - | - | | Flagship models | Claude Fable 5.1 and Claude Opus 5.5 | GPT-6 Astra | | What the vendor says they are for | Fable 5.1: demanding reasoning and long-horizon agentic work. Opus 5.5: long-running agentic coding and knowledge work | Complex reasoning, coding, computer use, research, and document creation | | Context window (API) | 1M tokens for both | 1,050,000 tokens | | Max output (API) | 128K tokens for both | 128,000 tokens | | API price per 1M tokens (input / output) | Fable 5.1: USD 10 / USD 50. Opus 5.5: USD 4 / USD 20 | USD 10 / USD 50 | | Entry plan | Claude Pro: USD 20 a month, or USD 17 a month billed yearly | ChatGPT Plus: USD 20 a month | | Flagship on the entry plan | Opus is included. Fable 5.1 is outside Pro's usage limits and runs on usage credits at API rates | GPT-6 Astra in ChatGPT Work and Codex only. GPT-6 Pro in Chat needs Pro, Business, or Enterprise | | Higher plans | Max 5x: USD 100. Max 20x: USD 200 a month | Pro: USD 100, USD 200, or USD 500 a month | | Both in one chat | Capriole AI Premium, USD 8 a month | Capriole AI Premium, USD 8 a month | ## How Anthropic describes Claude Fable 5.1 and Opus 5.5 Anthropic says Claude Fable 5.1 brings stronger long-running agentic coding, multistep research, and document, spreadsheet, and slide work. It is the slower of the two. For most workloads, Anthropic recommends starting with Claude Opus 5.5. Its announcement says Opus 5.5 performs at the level of Fable 5.1 on most work and, on Anthropic's benchmarks, leads in agentic coding, computer use, and knowledge work. Anthropic suggests Fable 5.1 when Opus 5.5 at higher effort still falls short. Both models have thinking always on. They read text and images, write text, and have a 1M-token context window. ## How OpenAI describes GPT-6 Astra OpenAI calls GPT-6 Astra its most capable model for the most demanding work. It lists complex reasoning, coding, computer use, research, and document creation as the main uses. You can set reasoning effort from `low` to `max`. GPT-6 Astra reads text and images and writes text. On the API, prompts above 272K input tokens cost more: 2× the input rate and 1.5× the output rate for the whole request. ## What each subscription gives you **Claude.** Every Claude plan has a five-hour session limit, and paid plans add a weekly limit. Claude Pro gives at least 5× the Free plan's usage per session. Max 5x and Max 20x give 5× or 20× Pro's usage per session. On Pro, Fable 5.1 is not part of the plan's usage limits and is billed through usage credits at standard API rates. On Max, Fable models can use up to 50% of the weekly limits. Read [Claude usage limits explained](https://docs.capriole.ai/articles/claude-usage-limits.md) for the details. **ChatGPT.** On Plus, GPT-6 in Chat runs on GPT-6 Sol. GPT-6 Astra is included in ChatGPT Work and Codex, where OpenAI estimates 5 to 45 local messages per five-hour window and says weekly limits may also apply. GPT-6 Pro, the Chat option powered by Astra, needs Pro, Business, or Enterprise. Even on Pro, OpenAI says GPT-6 Pro use is not unlimited. The [ChatGPT Plus alternative](https://docs.capriole.ai/articles/chatgpt-plus-alternative.md) page compares Plus with Capriole AI in full. Neither Claude Pro nor ChatGPT Plus includes API usage. On those plans, both vendors bill the API separately. ## Use both in one chat for USD 8 Capriole AI Premium costs USD 8 a month for unlimited web chat on every supported model, including GPT-6 Astra, Claude Fable 5.1, Claude Opus 5.5, and Gemini 4 Argon. A [fair-use limit](https://docs.capriole.ai/guides/plans-and-limits.md#what-unlimited-means) of 200 messages per account per day only stops scripted abuse. You do not have to choose one vendor per chat. [Switch models mid-chat](https://docs.capriole.ai/articles/switch-models-mid-chat.md) and the thread, its files, and its context stay together: 1. Draft with GPT-6 Astra. 2. Switch to Claude Fable 5.1 and ask it to challenge the draft. 3. Switch to Claude Opus 5.5 or Gemini 4 Argon for a third view, or to finish the work. Premium also includes free image generation with GPT Image 2.5 and Nano Banana 2.1, files and web search, projects, chat export, personalization, and storage controls. ## API prices compared For apps and coding agents, Capriole AI charges the same price for every supported model. | Model | Official API price per 1M tokens (input / output) | Capriole AI | | - | - | - | | GPT-6 Astra | USD 10 / USD 50 | USD 8 per 5M tokens | | Claude Fable 5.1 | USD 10 / USD 50 | USD 8 per 5M tokens | | Claude Opus 5.5 | USD 4 / USD 20 | USD 8 per 5M tokens | USD 8 per 5M tokens is USD 1.60 per million, for input and output alike. Premium includes 5M API tokens a month, and top-ups cost USD 8 per 5M tokens. Cached input counts at 10%, as [charged tokens](https://docs.capriole.ai/articles/charged-tokens.md) explains. One key works with OpenAI Chat Completions, OpenAI Responses, and Anthropic Messages clients, and with [10 documented coding agents](https://docs.capriole.ai/guides/one-api-key-coding-agents.md), including Codex and Claude Code. ## Which one should you use? * **Start with Claude Opus 5.5** for most coding and knowledge work. That is Anthropic's own advice, and its API price is the lowest of the three. * **Move to Claude Fable 5.1** for the hardest reasoning or long agentic tasks, when Opus 5.5 is not enough. * **Use GPT-6 Astra** for demanding reasoning, research, coding, and document work, or for a second opinion from another vendor. The vendors' benchmarks do not tell you which model is best at your task. Asking two of them in the same thread does. The [model guide](https://docs.capriole.ai/guides/choose-a-model.md) compares all four flagships, including Gemini 4 Argon, and explains the **Thinking** and **Fast** presets. ## Frequently asked questions > **Is Claude better than ChatGPT?** > > It depends on the task. Anthropic positions Claude Opus 5.5 and Fable 5.1 for agentic coding, knowledge work, and long reasoning. OpenAI positions GPT-6 Astra for its most demanding work. Try both on your own task in one Capriole AI chat. > **Which is cheaper, Claude or ChatGPT?** > > The entry plans cost the same: Claude Pro and ChatGPT Plus are both USD 20 a month. On the API, Claude Opus 5.5 costs USD 4 / USD 20 per million tokens, and GPT-6 Astra and Claude Fable 5.1 both cost USD 10 / USD 50. Capriole AI Premium costs USD 8 a month for unlimited web chat with all three. > **Can I use Claude and ChatGPT models in one app?** > > Yes. Capriole AI has GPT-6 Astra, Claude Fable 5.1, Claude Opus 5.5, and Gemini 4 Argon in one workspace, and you can switch models inside the same conversation. > **Do I need both a Claude and a ChatGPT subscription?** > > Not to chat with both vendors' flagship models. Capriole AI Premium covers them in one USD 8 plan. You still need the vendors' own apps for features that exist only there, such as Claude Code with a Claude sign-in or ChatGPT Work. ## Get started > **[Start chatting](https://www.capriole.ai/)** > > Switch between Claude and GPT-6 Astra in one chat, no account needed. > **[Get Premium](https://www.capriole.ai/?view=api)** > > Unlimited web chat and an API key for USD 8 a month. ## Official sources * Anthropic: [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview), [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview), [Claude Opus 5.5 announcement](https://www.anthropic.com/claude-opus-5-5), [Claude plans and pricing](https://claude.com/pricing), [What is the Max plan?](https://support.claude.com/en/articles/11049741-what-is-the-max-plan), and [Claude Fable models on your plan](https://support.claude.com/en/articles/15424964-claude-fable-models-on-your-plan) * OpenAI: [GPT-6 Astra model](https://developers.openai.com/api/docs/models/gpt-6-astra), [What is ChatGPT Plus?](https://help.openai.com/en/articles/6950777-what-is-chatgpt-plus), [GPT-6 and other models in ChatGPT](https://help.openai.com/en/articles/20001354-gpt-6-and-other-models-in-chatgpt), [Managing usage with GPT-6 Astra in Work and Codex](https://help.openai.com/en/articles/20001516-managing-usage-with-gpt-6-astra-in-work-and-codex), and [About ChatGPT Pro tiers](https://help.openai.com/en/articles/9793128-about-chatgpt-pro-tiers) Capriole AI facts on this page are maintained as first-party documentation. 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