GPT-6 Astra vs Claude Fable 5.1 vs Gemini 3.8 Flash
A source-backed comparison of three leading API models across frontier capability positioning, agentic workloads, multimodal inputs and token economics.
Astra and Fable compete in the premium tier, while Gemini offers much lower current token prices and broader multimodal inputs.
Choose Astra when OpenAI's frontier positioning and first-party tool ecosystem are central to the workload.
View GPT-6 AstraAnthropic positions Fable 5.1 for demanding agentic coding, multistep research and complex knowledge work.
View Claude Fable 5.1Gemini's introductory $0.75 input and $3.75 output rates are far below the two premium models' $10 and $50 rates.
View Gemini 3.8 FlashAt a Glance
Detailed Comparison Matrix
| Feature | OpenAI GPT-6 Astra | Anthropic Claude Fable 5.1 | Google Gemini 3.8 Flash |
|---|---|---|---|
| Provider | OpenAI | Anthropic | |
| AIWS Category | AI Model | AI Model | Fast Multimodal |
| Provider Status | Not published | Active | General availability |
| Release Date | Not published | Sep 1, 2026 | Sep 2, 2026 |
| Context Window | 1,050,000 tokens | 1M tokens | 1,048,576 tokens |
| Maximum Output | 128,000 tokens | 128K tokens | 65,536 tokens |
| Input Price / 1M | $10.00 | $10.00 | $0.7500 |
| Cached Input / 1M | $1.00 | $0.2500 | $0.0750 |
| Output Price / 1M | $50.00 | $50.00 | $3.75 |
| Long-Context Pricing | Above 272,000 tokens · $20.00 input · $75.00 output | No separate tier stored | No separate tier stored |
| Pricing Conditions | Long-context tier: Above 272,000 tokens | No special condition stored | Published rate through Dec 31, 2026 |
| Native Input Modalities | text, image | Text, Images | text, image, video, audio, pdf |
| Native Output Modalities | text | Text | text |
| Built-in/API Tools | Image generation: Supported · Web search: Supported · File search: Supported · Code interpreter: Supported · Computer use: Supported · MCP: Supported · Hosted shell: Supported · Apply patch: Supported · Skills: Supported · Tool search: Supported | Not published | Image generation: Not supported · Web search: Supported · File search: Supported · Code interpreter: Supported · Computer use: Supported |
| Core Capabilities | Reasoning: Supported · Image input: Supported · Audio input: Not supported · Video input: Not supported · API access: Available | Reasoning: Supported · Image input: Supported · Audio input: Not supported · Video input: Not supported · API access: Available | Reasoning: Supported · Image input: Supported · Audio input: Supported · Video input: Supported · API access: Available |
| API Availability | Available | Available | Available |
| Provider API Model ID | gpt-6-astra | claude-fable-5-1 | gemini-3.8-flash |
| Verification Checkpoint | Sep 21, 2026 | Sep 1, 2026 | Sep 2, 2026 |
Native output is what the model returns directly. Tool capabilities are separate.
Winner by Use Case
Astra is OpenAI's frontier API model and is documented alongside OpenAI's broad first-party tool and agent stack.
Anthropic explicitly positions Fable 5.1 for demanding reasoning, long-horizon agentic coding and multistep research.
Its introductory 2026 token rates are materially lower than Astra and Fable 5.1.
It is the only model in this comparison whose verified record includes all three input types.
All three models are in the same practical context class; the small numerical difference does not establish a meaningful universal advantage.
Pricing & Token Economics
Example uses 1M standard input tokens + 1M output tokens. It excludes caching, long-context, storage, batch, regional and other special pricing conditions.
What We Think
Premium frontier choice inside OpenAI
Astra is the logical choice when teams need OpenAI's frontier model and can justify premium token rates through higher task success, integrated tools or lower workflow friction. Requests above 272,000 input tokens trigger higher long-context pricing, so realistic cost modeling matters.
Anthropic's premium agentic specialist
Fable 5.1 has the strongest case for teams already centered on Anthropic and workloads involving long-horizon agentic coding, multistep research and complex knowledge work. Its provider positioning should still be validated on representative internal tasks.
Gemini separates on economics and input breadth
Gemini 3.8 Flash costs a fraction of either premium model at its introductory 2026 rates and supports text, image, video, audio and PDF inputs. Buyers should also model the announced January 2027 rates before making long-term commitments.
Methodology & Sources
AI World Scope resolves pricing, context limits, output limits, modalities, API availability and verification dates from canonical model records. Use-case winners are qualitative editorial judgments based on verified provider documentation and workload fit. We do not name a normalized performance champion because the three models have not been tested under one identical independent AI World Scope methodology. Cost comparisons use standard direct API token rates and retain time-limited and long-context pricing conditions.
Provider positioning is not treated as independent AI World Scope performance testing.
Standard token prices exclude tool charges, taxes, infrastructure, retries and workload-specific token amplification.
Gemini 3.8 Flash's introductory rates apply through December 31, 2026; announced rates rise on January 1, 2027.
GPT-6 Astra requests above 272,000 input tokens use higher long-context rates for the full request.
Run a representative internal evaluation before committing production workloads.
Key Takeaways
GPT-6 Astra and Claude Fable 5.1 share the same verified standard token prices: $10 input and $50 output per million tokens.
Gemini 3.8 Flash is the current price leader and the only model here with video, audio and PDF inputs.
Astra carries a long-context surcharge above 272,000 input tokens.
All three sit in approximately the one-million-token context class.
No universal benchmark winner is named without identical independent testing.