Astra figures are OpenAI-reported, as of September 2026
GPT-6 Astra data comes from OpenAI's September 3, 2026 announcement and model documentation — vendor-reported, not yet independently verified. Fable 5.1 prices and specs are Anthropic's published rates, verified 2026-09-02.
See our earlier Fable 5 vs GPT-5.5 comparisonGPT-6 Astra vs Fable 5.1 · September 2026
GPT-6 Astra vs Claude Fable 5.1
OpenAI's computer-use flagship against Anthropic's coding flagship — identical list pricing, very different billing behavior. Specs, vendor-reported benchmarks, and how to choose.
TL;DR
Both flagships list at $10/$50 per M tokens (as of September 2026). GPT-6 Astra leads OpenAI's own computer-use and agent benchmarks (Terminal-Bench Science 64.6% vs 52.6%, vendor-run) and offers a 1.05M context window — but requests above 272K input tokens bill at 2x input / 1.5x output. Claude Fable 5.1 keeps flat rates at any context length and holds the strongest published coding score (87.7% SWE-bench Verified; Astra has no published equivalent).
Specs at a glance
Astra rates are OpenAI list prices as of September 2026; Fable 5.1 rates are Anthropic list prices from the September 2, 2026 release.
| Spec | GPT-6 Astra | Claude Fable 5.1 |
|---|---|---|
| Model ID | gpt-6-astra | claude-fable-5-1-20260902 |
| Released | September 3, 2026 | September 2, 2026 |
| Input price (per M tokens) | $10.00 | $10.00 |
| Output price (per M tokens) | $50.00 | $50.00 |
| Long-context billing | 2x input / 1.5x output above 272K input | Flat rates at any context length |
| Context window | 1.05M | 1M |
| Max output | 128K | 128K |
| Computer use | Purpose-built (computer-use first) | Strong (API computer-use tooling) |
| Extended thinking | Effort tiers including xhigh and max | Adaptive budget + effort tiers |
| Data retention | Zero Data Retention for eligible API customers | 30-day mandatory |
The headline prices are identical — the difference shows at scale. Astra requests above 272K input tokens bill the whole request at 2x input / 1.5x output; Fable 5.1 keeps flat $10/$50 at any context length.
Benchmarks — mostly vendor-reported
OpenAI runs both models side by side on Terminal-Bench; the SWE-bench and OSWorld rows come from each vendor separately and are not directly comparable.
| Spec | GPT-6 Astra | Claude Fable 5.1 |
|---|---|---|
| SWE-bench Verified | Not published | 87.7% |
| Terminal-Bench 4.0 | 57.9% | 55.8% |
| Terminal-Bench Science 0.1 | 64.6% | 52.6% |
| BenchCAD | 95.9% | 84.3% |
| OSWorld (see note) | 72.6% | 89.6% |
Sources: Terminal-Bench 4.0, Terminal-Bench Science 0.1 and BenchCAD figures are from OpenAI's own harness runs (September 2026). Fable 5.1's 87.7% SWE-bench Verified is Anthropic-reported (September 2, 2026 release); OpenAI has not published an Astra SWE-bench Verified score. The OSWorld row mixes different benchmark releases — Anthropic reports 89.6% for Fable 5.1, OpenAI reports 72.6% for Astra on OSWorld V2-Offline — so treat it as directional only. Third-party analysis (MindStudio) concludes Astra is not comprehensively ahead.
How to decide
Same price tag, different machines. Route by workload.
You need autonomous computer-use agents
Astra is OpenAI's computer-use-first flagship — built around hosted computer-use, shell and browser tooling, with Agents' Last Exam at 59.3% (vendor-run). Fable 5.1 is capable through API computer-use tooling, but Astra is purpose-built for this.
You need verified agentic coding
Fable 5.1's 87.7% SWE-bench Verified is the strongest published coding score between the two; OpenAI has not published an Astra SWE-bench score, and its Terminal-Bench edge (57.9% vs 55.8%) comes from OpenAI's own harness.
You routinely ingest near-1M-token inputs
Astra's 1.05M window nominally beats Fable 5.1's 1M, but past 272K input tokens the whole request bills at 2x input / 1.5x output. For long-document workloads, Fable 5.1's flat rates usually win on total cost.
You're comparing cost below 272K input
Below the surcharge threshold the two are cost-equivalent: $10/$50 list, $1.00 cached input, 50% batch pricing. Your existing token-mix math carries over — run it through the cost calculator.
Your work touches security research — or looks like it
Astra is OpenAI's first model at the Critical cybersecurity threshold: standard access refuses advanced exploit work, API safety checks can stop tasks mid-run, and cyber capabilities are gated behind a Trusted Access program. Fable 5.1 has no equivalent gate.
At list price the two are nearly interchangeable on cost — the real deltas are the 272K surcharge, computer-use depth, and whose benchmarks you trust.
Price out your own workload
Both models cost $10/$50 per M tokens at list — what matters is your token mix, cache hit rate, and how often you cross 272K input tokens.