The top models behind the two assistants are now GPT-6 Astra, which OpenAI released on September 3, 2026, and Claude Fable 5.1, which Anthropic released two days earlier. Both list at $10 per million input tokens and $50 per million output tokens in the API, and both read text and images. Astra has a 1,050,000-token context window and Fable 5.1 has 1M. In ChatGPT, Astra is available on Plus, Pro, Business and Enterprise plans. In Claude, Fable 5.1 is available on Pro, Max, Team and Enterprise plans.
OpenAI positions Astra for computer use, coding and documents, spreadsheets and slides that follow your templates. Anthropic positions Fable 5.1 for long-running agentic coding, research and multi-stage knowledge work. The published numbers point both ways: OpenAI's own launch table puts Astra ahead on Terminal-Bench 4.0 and DeepSWE, and the same table shows Fable 5.1 ahead on Humanity's Last Exam with tools and on the Artificial Analysis Intelligence Index. Both vendors also add safety layers. Fable 5.1 hands many flagged cybersecurity and biology requests to Opus models, and OpenAI says Astra's extra safety checks can pause legitimate work. Since neither wins everywhere, run the same prompt through both in Omny and compare.
Which should you choose?
ChatGPT
GPT-6 Astra · 1M context
Pick it if
you want computer use and documents, spreadsheets and slides that follow your templates.
Claude
Claude Fable 5.1 · 1M context
Pick it if
you run long agentic coding or research tasks and want Anthropic's most capable model.
Pick ChatGPT with GPT-6 Astra if your work leans on computer use or documents and slides built to your templates. Pick Claude with Fable 5.1 for long agentic coding and research sessions. The vendors' benchmarks split between them, so test both on your own prompts.
Questions
Is ChatGPT or Claude better for coding?
Neither leads everywhere. OpenAI's launch table puts GPT-6 Astra ahead of Claude Fable 5.1 on Terminal-Bench 4.0 and DeepSWE, while Anthropic positions Fable 5.1 for codebase-wide features, code review and multi-day sessions. Try your own repository tasks on both.
How do ChatGPT and Claude compare on API price?
GPT-6 Astra and Claude Fable 5.1 both list at $10 per million input tokens and $50 per million output tokens. Astra charges more for prompts over 272K input tokens, and Fable 5.1 has cheaper cache reads at $0.25 per million tokens against Astra's $1.
Which has the bigger context window?
They are close. GPT-6 Astra lists 1,050,000 tokens, up to 922,000 of them input, and Claude Fable 5.1 lists 1M tokens. Both can return up to 128K output tokens.