The cheap Claude-Fable-5 API offers Mythos-level intelligence for your hardest projects. It excels at autonomous coding, multi-day reasoning, and complex vision tasks, all while maintaining high safety standards and token efficiency.
Why a cheap Claude-Fable-5 API is the ultimate tool for frontier intelligence.
Senior-Grade Reasoning
Achieve senior research scientist grade outputs, picking directions and producing novel first-principles results.
Token Efficiency
Handle 50-million-line codebases with fewer turns and higher reliability than any previous Claude iteration.
Vision-First Audit
Extract precise numbers from scientific figures or rebuild source code from screenshots with zero scaffolding.
Long-Horizon Autonomy
Tackle projects that take days with a proactive model that plans across stages and delegates to sub-agents.
What is Claude Fable 5?
Claude Fable 5 is the first model in Anthropic's Claude 5 family and its first Mythos-class model released to the public, a capability tier above Claude Opus. It's state-of-the-art on most published benchmarks for software engineering, knowledge work, vision, and scientific reasoning, and its lead grows the longer and more multi-step the task. Launched June 9, 2026.
Spec
Value
Model string
claude-fable-5
Context window
1,000,000 tokens
Max output
128,000 tokens / request
Input
Text + image + file
Output
Text
Reasoning
Summarized thinking (raw chain-of-thought not returned)
Benchmarks as reported by Anthropic / OpenAI; validate on your own workload before committing. The honest read: Fable 5 tops the benchmarks but runs ~2× the price of the others. Opus 4.8 is the cheapest of the three and the better default for most general reasoning. GPT-5.5 sits in the middle on price and is the pick if you're standardized on OpenAI / Codex tooling. All three run from one GPTProto key and balance, so you can route each task to the right model without switching providers.
How to Get a claude-fable-5 API Key
Getting a claude-fable-5 API key takes four steps and a few minutes. Create a free GPTProto account, add credits, generate your key, and make your first call — at $8 / $40 it's a cheaper claude-fable-5 API key than going direct, and one key works across every model on the platform. Full claude-fable-5 Documentation is in the docs.
Sign up
Create your free GPT Proto account to begin. You can set up an organization for your team at any time.
Top up
Your balance can be used across all models on the platform, including claude-fable-5, giving you the flexibility to experiment and scale as needed.
Generate your API key
In your dashboard, create an API key — you'll need it to authenticate when making requests to claude-fable-5.
Make your first API call
Use your API key with our sample code to send a request to claude-fable-5 via GPT Proto and see instant AI-powered results.
Answers about the cheap Claude-Fable-5 API, including pricing models, safeguard fallbacks, and autonomous agent capabilities for your enterprise.
How much does the cheap Claude-Fable-5 API cost?
Claude Fable 5 is priced at $10 per million input tokens and $50 per million output tokens. This is less than half the price of the previous Mythos Preview. Additionally, users can leverage a 90% discount on input tokens through prompt caching, making it a very cheap Claude-Fable-5 API option for high-volume, repetitive tasks that require persistent context or large document sets stored in memory.
When should I use Fable 5 instead of Opus 4.8?
Use Fable 5 for your most ambitious, long-running projects that require autonomy. While Opus 4.8 is excellent for general reasoning, Fable 5 is built for tasks that span days, such as large-scale code migrations or deep research. If your query is flagged by cybersecurity or biology safeguards, the system will automatically route to Opus 4.8 to ensure safety without interrupting your workflow or charging you Fable prices.
Does Fable 5 support autonomous coding?
Yes, it is Anthropic's most capable model for agentic coding. It can perform codebase-wide migrations, write its own tests, and use vision to compare outputs against design goals. Stripe reported that Fable 5 compressed months of manual engineering work into just a few days. It functions effectively in agent harnesses like Claude Code, planning across multiple stages and delegating to sub-agents without supervision.
How do the vision capabilities compare?
Fable 5 is the state-of-the-art for vision tasks. It extracts precise data from complex charts, diagrams, and tables within PDFs. Unlike earlier models that required complex harnesses to interpret game states, Fable 5 has demonstrated the ability to beat games like Pokémon FireRed using only raw screenshots. This makes it ideal for rebuilding web apps from UI captures or auditing document-heavy files in legal sectors.
What are the data retention policies?
To maintain high safety standards for Mythos-class models, Fable 5 requires a 30-day data retention period for safety monitoring. This applies to both first-party and third-party surfaces. This data is not used for training new models; instead, it helps identify and reduce false positives in the safeguard classifiers. All human access to this logged data is strictly monitored and recorded to protect user privacy.
Is US-only inference available?
For organizations with strict data residency requirements, US-only inference is available. This ensures that the model processing stays within US borders. This specialized routing is priced at 1.1x the standard rate for both input and output tokens. This means you can still access a relatively cheap Claude-Fable-5 API while satisfying the compliance needs of legal, financial, or government-contracted projects.
