Model comparison

vs

Claude Fable 5.1 vs GPT-6 Astra

Anthropic against OpenAI, compared on listed price, real workload cost, context and capabilities.

The short answer

  • On Terminal-Bench 4.0, as each maker reports it, Claude Fable 5.1 scores 55.8% and GPT-6 Astra 57.9%.
  • Claude Fable 5.1 and GPT-6 Astra list the same input and output prices.
  • Claude Fable 5.1 reads cached input for less ($0.25/M against GPT-6 Astra's $1/M), which decides the bill for agents that resend long context.

Side-by-side specs

SpecClaude Fable 5.1GPT-6 Astra
ProviderAnthropicOpenAI
Input price$10/M$10/M
Output price$50/M$50/M
Cached input$0.25/M$1/M
Blended price (3:1)$20/M$20/M
Context window1M tokens1M tokens
Max output128k tokens128k tokens
InputText, ImagesText, Images
Structured outputYesYes
WeightsClosedClosed
ReleasedSeptember 1, 2026September 2026
Terminal-Bench 4.0 (maker-reported)55.8%57.9%
Humanity's Last Exam (with tools) (maker-reported)65.0%57.2%

Same work, both models

WorkloadClaude Fable 5.1GPT-6 Astra
One chat reply3,000 tokens in, 500 outSame$0.06$0.06
Summarise a 100-page report50,000 tokens in, 1,500 out, one request$0.58$0.58
1,000 classification calls500 tokens in, 20 out, per call$6.00$6.00
Coding-agent session2M tokens in across ~60 turns, 60,000 out, no cache$23.00$23.00
Same session, cached85% of input read from the prompt cache, the rest written to itGPT-6 Astra costs 1.2× as much as Claude Fable 5.1$7.18$8.45

At listed rates. Token counts are typical sizes, not measurements.

Claude Fable 5.1 pricing notes

  • Cache hits bill at $0.25 per 1M tokens (0.025x input), a quarter of Fable 5's $1; cache writes at $12.50 (5-minute tier).
  • The full 1M-token window bills at the standard rate, with no long-context surcharge.
  • Adaptive thinking is always on and cannot be disabled; the effort setting (default high) steers its depth.

GPT-6 Astra pricing notes

  • Requests over 272K input tokens bill in full at 2x input and cache rates and 1.5x output; the listed price is the ≤272K rate.
  • Cache writes bill at $12.50 per 1M tokens (30-minute tier); cache hits at $1.00.

When to pick which

Claude Fable 5.1

Anthropic's Claude model for demanding reasoning and long-horizon agentic work, released as the successor to Fable 5. Same $10 / $50 rate with cache reads at a quarter of the cost; Anthropic points most workloads to the cheaper Opus 5.5.

Pick it if

  • Opus 5.5 at higher effort still falls short on your evals
  • you run long agent sessions; cache hits bill at 2.5% of input
  • you run hours-long agentic coding or multistep research over a 1M window

Skip it if

  • Opus 5.5 covers your workload at 40% of the per-token price
  • your code forces tool use, prefills replies or sets temperature; all return errors

GPT-6 Astra

OpenAI's top GPT-6 model, which OpenAI calls its most capable for the most demanding work. It takes text and images and costs five times GPT-6.1 Sol's per-token rate.

Pick it if

  • you want OpenAI's top tier for complex reasoning, coding or computer use
  • you resend long prompts; cache hits bill at 10% of input
  • you need replies of up to 128K output tokens

Skip it if

  • GPT-6.1 Sol covers your workload at one-fifth the per-token price
  • your prompts routinely pass 272K tokens; the whole request then bills higher

FAQ

Which is better, Claude Fable 5.1 or GPT-6 Astra?

On Terminal-Bench 4.0, as each maker reports it, Claude Fable 5.1 scores 55.8% and GPT-6 Astra 57.9%. These are each maker's own numbers, not a controlled head-to-head; the spec table lists every benchmark both publish.

Which is cheaper, Claude Fable 5.1 or GPT-6 Astra?

Claude Fable 5.1 and GPT-6 Astra list the same input and output prices. On a coding-agent session (2M tokens in, 60,000 out) Claude Fable 5.1 costs $23.00 and GPT-6 Astra $23.00.

Can I switch between Claude Fable 5.1 and GPT-6 Astra mid-task?

Yes. In an Octomind session, /model octohub:claude-fable-5-1 and /model octohub:gpt-6-astra switch models without losing the conversation, so you can draft on one and review on the other.

Try either model

Switch between models inside the same Octomind session.

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Prices from the catalog of 2026-10-31