AnthropicText / ChatClaude Fable 5 API: Anthropic's most capable model, one key away
Claude Fable 5 via the ApexApi gateway
Claude Fable 5 is Anthropic's most capable widely released model, built for the most demanding reasoning and long-horizon agentic work, with adaptive thinking always on and a 1M-token context window. Call it through ApexApi's unified, OpenAI-compatible API alongside every other major model.
Claude Fable 5 is served through ApexApi's unified, OpenAI-compatible API. One key, one format, with smart routing and automatic failover. Provider: Anthropic.
Why Claude Fable 5
Adaptive thinking, always on
Reasons as deeply as each task needs automatically, with no thinking toggles or extra parameters to manage.
Long-horizon agentic work
Sustains multi-step coding, tool use, and autonomous runs across long sessions without losing the thread.
1M-token context
Reason over whole codebases and long documents in a single request.
Specifications
- Modality
- chat
- Context window
- 1000K tokens
- Max output
- 128K tokens
- Streaming
- Yes
- Tool / function calling
- Yes
- Vision input
- Yes
Claude Fable 5: measured reliability
From real calls ApexApi made to Claude Fable 5 during health sweeps over the last 30 days. Our own measurements, not vendor claims.
- Success rate
- 100%
- Avg latency
- 7.7s
- Calls measured
- 1
- Last checked
- Jul 25
See how Claude Fable 5 compares against every model we serve on the model rankings.
Claude Fable 5 pricing
- A million tokens in and a million out costs $72.00 here, all-in.
- For lighter work, Claude Haiku 4.5 from the same maker costs 10× less — one string apart on the same key.
- It is one of 33 chat models here with a 1M-token context window.
Getting started with Claude Fable 5
OpenAI-compatible. Point your client at ApexApi, swap your key, and call it. No new SDK to learn.
from openai import OpenAI
client = OpenAI(
base_url="https://api.apexapi.dev/v1",
api_key="<YOUR_APEXAPI_KEY>",
)
response = client.chat.completions.create(
model="anthropic/claude-fable-5",
messages=[{"role": "user", "content": "Hello!"}],
)
print(response.choices[0].message.content)Claude Fable 5 use cases
What teams build with Claude Fable 5 on ApexApi.
Autonomous coding agents
Whole-repo reasoning, multi-file refactors, and long autonomous engineering runs.
Deep research & analysis
Source-grounded synthesis over very large documents and datasets.
Complex enterprise workflows
High-autonomy assistants for legal, financial, and technical work that demand careful reasoning.
Claude Fable 5 vs other models
How it compares, and on ApexApi you can switch between any of them with a single string change, same key, same endpoint.
Claude Fable 5 vs Claude Opus 4.7
Opus 4.7 is the prior Opus-tier flagship; Fable 5 is Anthropic's most capable widely released model, stepping up reasoning depth and long-horizon agentic work. A/B them with one key on ApexApi.
Learn more about Claude Opus 4.7 API →Claude Fable 5 vs GPT-5.5
GPT-5.5 is OpenAI's broad multimodal frontier with strong tool orchestration; Fable 5 leads on demanding reasoning and sustained agentic runs.
Learn more about GPT-5.5 API →Claude Fable 5 vs Gemini 3.1 Pro Preview
Gemini 3.1 Pro centers on native multimodality and very long context; Fable 5 centers on deep reasoning and agentic depth.
Learn more about Gemini 3.1 Pro Preview API →Claude Fable 5 vs Claude Opus 5
Opus 5 delivers near-flagship agentic coding at half of Fable 5's price; Fable 5 remains the ceiling for the hardest reasoning and longest-horizon work.
Learn more about Claude Opus 5 API →Claude Fable 5 API: FAQ
How do I use the Claude Fable 5 API?
Create an ApexApi key, then point your client at https://api.apexapi.dev/v1 and use the model slug. Send a request to /v1/chat/completions with the model slug. The API is OpenAI-compatible, so most OpenAI SDKs work by changing the base URL and key.
Is the Claude Fable 5 API OpenAI-compatible?
Yes. ApexApi exposes Claude Fable 5 through the same OpenAI-compatible interface used across the whole catalog. Swap the base URL and API key and keep your existing code.
How much does Claude Fable 5 cost on ApexApi?
Pay-per-use. See the live price in the Pricing section above. There's no subscription or minimum; you buy credits and pay only for what you call.
Can I switch from Claude Fable 5 to another model later?
Yes. Change a single string (the model slug) to call any other model in the catalog through the same endpoint and key. No re-integration.
Ready to build with Claude Fable 5?
One API key. Every major AI model. Pay only for what you use.
Get your API key, free to start